card 1990 superior province canada

Precambrtan Research, 48 (1990) 99 -156

Elsevier Soence Pubhshe r s B V , A m s t e r d a m - - P n n t e d m The Nether lands

99

A review of the Superior Province of the Canadian Shield, a product of Archean accretion

K.D Card Geologtcal Survey of Canada, Ottawa, Ont KIA OE4, Canada

(Received January 30, 1989, revised and accepted January 24, 1990 )

ABSTRACT

Card, K D , 1990 A review of the Super ior Province of the C a n a d m n Shield, a product of Archean accret ion

P r e c a m b n a n R e s , 48 99 -156

The Superior Province consists of northern and southern high-grade gneiss subprovlnces and a central region of alternating granite-greenstone and metasedlmentary belts Subprovmces are commonly fault-bounded and &splay contrasting hthologlcal assemblages, metamorphic and structural styles, geophysical characteristics, and ages, they are comparable to PhanerozoIc suspect terranes The Middle and Late Archean rocks of the Superior Province are of mantle and juvenile crustal origin with little evidence of inheritance of components older than ca 3 l Ga High-grade gneiss subprovmces are mainly deeper level equivalents of the supracrustal-rich belts but one, Minnesota River Valley, is part of an older, ca 3 6 Ga terrane that was juxtaposed late m the tectonic history Granite-greenstone terranes are characterized by low-grade voicano-se&mentary sequences ( thole lmc-komatnt ic submarine lava plato, tholentlc-calc-alkahc submanne to subaenal central complexes, early platform-type quartz arenlte-stromatollt lc carbonate, late Tlmlskamlng-type shoshomtlc/alkahc volcanic-fluvial sediment) that range in age from ca 3 0 Ga to 2 7 Ga The volcanlcs represent oceamc, island arc, and continental arc volcamsm, the quartz aremte-carbonate sequences deposition on relatively stable, early-formed ca 3 0 Ga crust, and the Tlmiskammg-type sequences deposition m pull-apart basins developed along strike-slip faults Late Archean, ca 2 75-2 70 Ga greenstone sequences occur throughout the Superior Province Middle Archean, ca 3 0-2 8 Ga sequences are common m northern and central Superior province, rare or absent in the south Volcamsm was accompanied by mafic to t rondhjemmc plutomsm The metasedlmentary belts consist of variably metamorphosed volcanogenlc turbidites with detrital zircons ranging in age from ca 3 0 Ga to 2 7 Ga The metased~ments were deposited after major volcamsm and probably represent accretlonary prisms Late Archean orogenesls, accompanied and followed by calc-alkahc plutomsm, youngs southward from about 2 73-2 72 Ga to 2 70-2 68 Ga It revolved large-scale nor th-south compression and dextral transpresslon and displays thin- to thick-skinned transitions The contemporanelty of events along the lengths of the belts and their southward younging, coupled w~th the evidence of major compression, are consistent with subduction-driven oblique accretion of oceanic and continental volcanic arcs, accreuonary sedimentary wedges, older microcontinental fragments etc in a convergent margin setting analogous to parts of the Pacific Rim Differences (eg abundance ofkomatntes and tonahtic plutonlc states) are attributable to a hotter Archean mantle

Introduction

The Superior Province, one of the world's largest Archean cratons, is exposed m the central part of the continent and together w~th other Archean cratons and Proterozo~c orogens, makes up the Canadian Shield, the Pre- cambrian core of North America (Hoffman, 1988, Fig. 1 ).

Over the past century, the Superior Prov-

race has been mapped by many geologists and recent advances, particularly m geochronology (Krogh, 1982), geochemistry (Patchett et al, 1981), kinematic analysis (Hanmer, 1986), and geophysics (Gupta et al., 1982, Dods et al, 1985 ) have provided new tools for unravelhng the complicated history of this ancient craton. In the following, the geology of the Superior Province is reviewed, comparisons are made with Phanerozolc Pacific-type orogens, and a

0 3 0 1 - 9 2 6 8 / 9 0 / $ 0 3 50 © 1990 Elsevier Science Publ ishers B V

I00 K D CARD

L E G E N D ~ - ~ Proterozolc, Phanerozolc rocks

Subprownce boundary ARCHEAN SUBPROVlNCE TYPE

~ Plutomc CAPE S M I T H

~ Volcano- plutomc BELT

~ Metased)mentary

~ H,gh-grade gne)ss I

I 300 km I

H U D S O N

BAY

TRANS - H U D S O N \

OROGEN ~ k

T H 0 M PSON.,~.-~'~ ~'3" PIKWITONEI ~ + + .z --~ ~ . . . . BEL , JAME

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+++ ++++++ ~_~_ _ _~.

BIRD

WINNIPEG

INTERIOR ~ _ - E ~ _ - - _ - ~ ~ ~ PLAINS ~ ~

@2 .,~ MINNESOT A ~ ' ~ - ~ " , ~ t - = VALLEY~"~",~

SOUTHERN PROVINCE

sopERIoR

+ +BIENVILL E + ÷ ÷ ÷ + 1

,x b~z 6

+ + + ~ +

%,

q- C3

:BROADBACK RIVER

/' HOMOCLiNE

O

Fig 1 Subprovmces of the Superior Province

model revolving subduct~on-drlven accretion for assembly of the Archean craton ~s presented. Here, Early Archean refers to rock umts and events older than 3.4 Ga, Middle Archean to the interval 3.4-2.8 Ga, Late Archean to the interval 2.8-2.5 Ga, and Early Proterozolc to the interval 2.5-1.6 Ga. All isotopic ages quoted, unless otherwise specified, are based on mulUple U-Pb determinations using zlr-

con, and have analytical errors of less than 5 Ma.

Definition of provinces, subprovinces and the nature of their boundaries

The geology of the Superior Province is shown m Figs 2, 4 and 5 With the exception of Proterozolc mafic dyke swarms, alkahc

SUPERIOR PROVINCE OF CANADIAN SHIELD, PRODUCT OF ARCHEAN ACCRETION 101

rock-carbonatlte complexes, and scattered outhers of Proterozoic and Phanerozoic sedimentary cover, the rocks of this 2 million km 2 region are of Archean age. Furthermore, they are at most slightly affected by Proterozolc deformation concentrated along the Superior- Trans-Hudson boundary in the northwest and northeast and along the Grenville front, Mid- continent rift, and Kapuskasmg zone in the south The Superior Province was stabilized near the end of the Late Archean, and with the exception of the aforementioned igneous activity and faulting, has remained stable since then.

The Superior Province is a remnant of a more extensive craton now surrounded and truncated by Early Proterozolc orogens, many of which represent collision zones between Ar- chean provinces (Gibb, 1983; Hoffman, 1988, Fig 1 ). The western, northern, and southeastern boundaries of the Superior Province with the Trans-Hudson and Grenville orogens are tectonic w~th thrusting and transcurrent fault. ing. The southern and eastern contacts with the Penokean and New Quebec (Labrador Trough) orogens represent Early Proterozolc supracrustal sequences unconformably overlying and thrust upon the Superior Province

The Superior Province can be subdivided into volcano-plutonlc ("gramte-greenstone" ), metasedlmentary, plutonlc, and high- grade gneiss subprovinces on the basis of h- thology, structure, metamorphism, geophysical and metallogenetic characteristics, and ages of rock units and tectonic events (Card and Cieslelski, 1986) These subprovmces (Fig. l ) Include northern and southern high-grade gneiss terranes, and a broad central region of alternating volcano-plutonlc and metasedlmentary subprovinces. The high-grade gneiss subprovinces are characterized by upper amphlbolite- and granuhte-facles gnelsses of supracrustal and plutonic origin and positive gravity and magnetic anomalies. The volcano° plutonic subprovInces have low-grade greenstone belt metavolcanlc-metasedlmentary se-

quences surrounded and intruded by granltold bathohths whereas the Intervening metasedlmentary terranes consist mainly of variably deformed and metamorphosed turbldltes and anatectic granites

Subprovince boundaries are commonly zones of structural and metamorphic transition of appreoable width in which faulting and igneous activity have masked any primary lithological transitions. Some subprovlnce boundaries (eg Sachlgo-Plkwltonel and Wawa-Kapuskasing) represent metamorphic transitions (Hubregtse, 1980 Percival, 1983 ), whereas others (eg. Mlnto-Bienvllle) correspond to changes in structural trend and style. Many subprovlnce boundaries are east-west faults that extend throughout much of Supe- rior Province and juxtapose terranes of contrasting geological and geophysical character- 1sties. Some boundary faults are crustal-scale, affecting significant crustal thicknesses and producing geophysical anomalies attributable to changes in crustal structure (Hall and Bris- bin, 1982) Some have histories of early dip- slip movement, possibly thrusting, and late strike-slip displacement associated with shearing, metasomatic alteration, and formation of lode gold deposits (Card et al., 1989) The amount and nature of the displacements on these structures is generally unknown and late transcurrent movements may mask earlier displacements.

Isotopic age determinations show that volcanic and plutomc rocks of Superior province range from about 3.1 Ga to 2.6 Ga and that within this range there is evidence for several major magmatic episodes at about 3.0 Ga and 2 7 Ga (Fig. 3) During these episodes, tholentic, calc-alkahc, komatntic and alkahc volcamcs and assocmted volcanogenlc clastlc and chemical sediments of the greenstone belts were deposited, as were the turbidltes of the intervening metasedimentary subprovlnces Early magmatlc episodes may have been accompanied or succeeded by regional deformation and metamorphic events to which names

102 K D CARD

- 5 4 ° "~

I 92 °

\ \ \

Hudson

Hudson Bay Basra

Lake ~(~-" x x Wmmpeg ~

~ Archean rocks reworked during i Proterozo¢ orogenesls

Late potesaic suite plutons-gramte grenodionte syenite

Early eddic suite plutons-quarrz diorite tonalite, grenodlorffe unclassified feleic intermediate plutonic rocks

r - - ] Gcetsaic plutonIc (tonaltte-grenodlorlte) / / rocks with maflc enclaves

L Grenullte facies ortho-and paregnelss

Paragnelss mlgmatde dlotexlte

- ~ TulClldltic motasedlments wocke conglomerate, pellte

~ Fluvlol/olluv,al sandstone ccogk~morete, commonly with alkelic volcenics

~ Quartz aremte quartz pebble conglomerate stromotolitic /÷÷

movie

Tholeilec-komatlltic metavolcenic sequences

~ Mlxad celo elkolic and tholelltJc :'÷~ metevolcanic sequences

Mafic ultremohc enorti~osfftc ~? v'; intrusions

-p + +

34

Lake Supenor

km 0 200 . /

f I I J J

Penokean

Orogen Fault (solid circle indicates downthrown side

arrows indicate relative movement)

Thrust fault ~ ~

960 92° I I I

Fig 2 Geology of the western Superior Province l = A t l k o k a n belt, 2 = A t l k w a bathohth, 3=Aulneau bathohth, 4=Beardmore-Geraldton belt, 5 = B l r c h - U c h l belt, 6=Bird River belt, 7=Caribou Lake belt, 8=Cross Lake belt, 9 = Dalles bathohth, 10= Favourable Lake belt, 11 = Fort Hope belt, 12 = Georgia Lake area, 13 = Giants Range bathohth, 14 = Gods Lake belt, 15 = Hemlo belt, 16 = Horseshoe Lake belt, 17= Island Lake belt, 18 = KaUala-Balrd bathohth, 19= Lac du Bonnet bathohth, 20 = Lac des Isles complex, 21 = Lake of the Woods belt, 22 = Lake St Joseph belt, 23 = Lount Lake bathohth, 2 4 = L u m b y Lake belt, 25=Manltouwadge belt, 26=Manltouwadge gneiss, 2 7 = M a r m l o n bathohth, 28 = Melchett Lake belt, 2 9 = Mulcahy Lake complex, 30 = Muskratdam Lake belt, 31 = North Caribou Lake belt, 32 = North Trout Lake bathohth, 3 3 = N o r t h Spirit Lake belt, 3 4 = O n a m a n gneiss, 35=Oxford Lake belt, 36=Pick le Lake belt, 3 7 = Pukaskwa gneiss, 38 = Rainy Lake belt, 39= Red Lake belt, 40 = Rice Lake belt, 41 = Sabaskong bathohth, 42 = San Antonio Formation, 43= Sandy Lake belt, 44= Saganaga-Northern Lights bathohth, 45= Savant Lake belt, 46= Seine Group, 47= Sen Bay gneiss, 48= Shebandowan belt, 49= Steep Rock Group, 50= Sturgeon Lake bathohth, 52=Trout Lake bathohth, 53 = Utlk Lake belt, 54 = Vermilion bathohth, 55 = Vermilion belt, 56 = Wabigoon diapinc axis


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104

TABLE l

Summary of the isotopic ages of rock umts and events, southern Superaor Province

K D CARD

Age Minnesota River Wawa Kapuskasmg Abmbt Pontiac (Ma) Valley

2630

2650

2670

2690 Late plutons

2710

2730

2750 2770

2800

2900

3000

3100

3400 3600

Late plutons (2684-2660) Late deformation (2685 + 5) Shebandowan Group Felslc plutons (2700-2690)

Early deformation (2695 + 5 )

Deformation, meta- Volcamcs (2696) morphlsm (ca 2700)

Synvolcamc plutons

Volcamcs (2749)

Deformatmn, meta- Early volcanic and morph~sm, plutomc rocks plutonlsm (ca 2800-3000) (ca 2900)

Deformation, metamorphism - Mortoman Event (ca 3600) Volcamc, plutonlc precursors of Morton, Montewdea gneiss

H~gh-grade metamorphism and deformation (ca 2680-2620)

Supracrustal and intrusive precursors of KSZ high-grade gnelsses

Late plutons (2686-2665)

Late deformation

Tlmlskamlng Group Felslc plutons (2700-2690)

Early deformation, metamorphism (2695 + 5)

Volcamcs (2697)

Synvolcanlc intrusions

Volcamcs (2747)

Late plutons, pegmat~tes (2687-2663)

Deformation and metamorphism (2690+5) Early plutons Sediments (2713)

such as "Wamplgowan orogeny" and "Lauren- tlan orogeny" have been given (Stockwell, 1982; Ermanovlcs and Wanless, 1983). How- ever, the effects of these early events have been largely obhterated by the polyphase deformation, regional metamorphism and widespread

plutomsm of the last major events to affect these rocks during the Kenoran orogeny (Stockwell, 1982 ). There is isotopm evidence, summarized m Fig. 3 and to be dealt with m later text, that the late, Kenoran events are not everywhere of the same age but that the cul-


Quetlco Wablgoon Winnipeg River Bird River English River

Pegmat~te Late deformatton,

metamorphism Gramtes (2671-2653 )

Deformation

Grano&orlte sills (2687 )

Late gramtes Late deformation - wrench faulting (2585 + 5 )

Late granite, pegmat~te

DeformaUon (9) Seine Group Late granite plutons Sediments Felslc plutons (2700-2690)

(2710-2695)9 80

Deformation, metamorphism (2710-2700)

Deformation metamorphism Deformation, (ca 2700) metamorphism

(ca 2700)

Deformation, metamorphism (2680)

Calc-alkahne Grano&onte plutons Sediments voicanlcs (2730-2710) (2709)

Synvolcanlc intrusions

TholelltlC volcamcs (2775-2730)

Volcanlcs and synvolcanlc intrusions

Deformation (ca 2800)

Volcanic and plutomc rocks ( 3100-2900)

Deformation and plutonlsrn (ca 2800)

Early gnelsslc plutonlc rocks (3170-3040)

mmatlon of orogenic activity was older in the north than in the south (Krogh et al., 1974) The sequence of major rock units and events for each subprovlnce IS summarized m Tables l and 2

There is a general lack of evidence, in the

form of unconformities, chemical contamination, or ISOtOpic inheritance, for older slallc basement to the voluminous 2 7 Ga metavolcanlc and metase&mentary accumulations. Rare unconformities and relatively mature shallow water platform and alluvial/fluvial

TA

BL

E 2

Sum

mar

y of

the

isot

opic

age

s of r

ock

umts

and

eve

nts,

nor

ther

n Su

peri

or P

rovi

nce

Age

U

chl

Ber

ens

Riv

er

Sach

lgo

(Ma)

2630

2650

2670

2690

2710

2730

2750

2770

Lat

e pl

uton

s L

ate

plut

ons

Lat

e pl

uton

s (2

704-

2668

) (2

715-

2690

) (2

705-

2680

L

ate

defo

rmat

ion

Faul

ting

fa

ultin

g Y

oung

er d

efor

mat

ion

(271

0-27

00)

met

amor

phis

m (

ca 2

700)

Sa

n A

ntom

o Fo

rmat

ion

Cro

ss L

ake,

Isl

and

Lak

e pl

uton

s (2

720-

2714

) O

xfor

d L

ake

Gro

ups

Def

orm

atio

n,

Def

orm

aUon

, D

efor

mat

mn,

m

etam

orph

ism

(27

30-

met

amor

phis

m

met

amor

phis

m (

2730

- 27

10)

Plut

ons

(276

0-27

30)

2710

) Pl

uton

s (2

731-

2728

) Pl

uton

s (2

732-

2712

)

You

nger

, cal

c-al

kahn

e vo

lcam

cs a

nd

synv

olca

nlc

lntr

usm

ns

(275

7-27

31)

You

nger

vol

cam

cs a

nd

synv

olca

mc

mtr

umon

s (2

757-

2720

)

2780

28

00

2900

3000

Tho

emm

-kom

atnt

m

volc

anlc

s an

d g

nel

sslc

plut

omc

rock

s (c

a 30

00-2

800)

Gne

lssl

c pl

uton

lc ro

cks

(ca

3000

-280

0)

Def

orm

atlo

n, p

luto

msm

(c

a 28

00)

Vol

cam

c an

d pl

utom

c ro

cks

(302

3-28

30)

3100

3400

3600

PIkw

ltone

~ an

d T

hom

pson

Bel

t

Def

orm

atio

n, h

ighg

rade

m

etam

orph

ism

(26

80-

2629

) Pe

gmat

Re

(269

0-26

82)

Def

orm

atio

n,

met

amor

phis

m

plut

omsm

(27

19-2

684)

Old

ergn

elss

Tho

mps

on

Bel

t(30

86-2

926)

Eas

tmam

, La

Gra

nde

Riv

er

Plu

tons

(272

8-27

08)

Def

orm

atio

n,

met

amor

phis

m

Def

orm

atio

n9

Plut

omc

and

volc

amc

rock

s

Ash

uam

pl

Def

orm

atio

n,

hlgh-grade

meta

morp

hosm

(2650-2620 )

Ton

ahte

plu

tons

(2

690)

Ung

ava

Plut

ons

(271

2)

Def

orm

atio

n,

met

amor

pMsm

(B

lenv

llle

)

Def

orm

atio

n9

Plut

omc

rock

s

O

>

SUPERIOR PROVINCE OF CANADIAN SHIELD, PRODUCT OF ARCHEAN ACCRETION 1 0 7

sediments are apparently confined to the older, ca 3 0 Ga sequences and to the somewhat younger riftogenlc sequences present along some of the major subprovlnce boundary faults Much of the Superior Province represents new continental crust formed during several major mantle separation events in the Middle and Late Archean, probably in settings and by processes not unlike those existing to- day in parts of the Pacific Furthermore, the fault-bounded nature of Superior subprovlnces and their distinctive geological and age characteristics invite comparison with Phane- rozolc "suspect terranes" such as those of the North American Cordillera (Coney et a l , 1980) The description of these subprovmces will proceed generally from south to north summarizing geological relationships ~mpor- tant to tectomc interpretations

neous and mafic gneiss and amphIbohte are metavolcanIc, suggesting the MRV IS of volcano-plutonic origin. Geochronological evidence (Goldich, 1972, Goldlch and Fischer, 1986) indicates orogenic events at 3.6 (Mor- tonian event) , 3 0, 2.8, and 2.7 Ga, the latter perhaps suturing along the GLTZ

The MRV is separated from the Wawa subprovince to the north by the Hillman and McGrath gneIsses, perhaps correlative with the MRV, and poorly known supracrustal belts Two tonahte plutons are 2688 Ma (Z.E Peter- man, unpub, data)

Wawa Subprovince

A Late Archean volcano-plutomc terrane

Minnesota River Valley

Early Archean htgh-grade gneiss, a possible foreland

Minnesota River Valley (MRV) in the southwest is characterized by granuhte-facles plutonlc and supracrustal gneiss older than 2 6 Ga It is separated from the Superior Province by the Great Lakes Tectonic Zone (GLTZ) (Sims et al , 1980; Fig 2 ), a crustal-scale thrust dipping 30 ° north according to seismic evidence (Gibbs et a l , 1984) MRV and simdar gneisses to the east (Morey et a l , 1982) may represent a foreland to the Superior Province, amalgamated about 2 7 Ga ago and dismem- bered during Early Proterozolc orogenesis. MRV may alternatively have been accreted to the Superior Province during the Penokean orogeny at ~ 1 86 Ga The ~ 2 7 Ga plutons cut- ting both the MRV gnelsses and the adjacent Superior Province terranes suggest the former

MRV gneisses were metamorphosed at 5 5- 7 kbar and 650-730°C (Perkins and Chipera, 1985) Geochemical evidence (Wooden et a l , 1982) indicates the felsic gneiss is meta-lg-

The Wawa Subprovince extends east from the Vermihon district of Minnesota to the Ka- puskaslng structural zone (KSZ) The subprovince is bounded on the south by the Early and Middle Proterozoic Southern Province and the Mid-Continent Rift and on the north by the metasedlmentary Quetlco Subprovince In the Vermihon district Bauer (1985) correlated structures across the faulted boundary between the low-grade Vermilion greenstone belt and the amphlbohte-facles Quetlco subprovlnce, implying the existence of an early major recumbent fold straddling this interface To the east, north-dipping mylonltes separate plutons of the Wawa Subprovlnce and QuetlcO schists and granites (Percival and Stern, 1984). Gramtes along the contact contain both amphibohte and paragneiss inclusions suggesting pre-granlte juxtaposition of the two terranes

In the Shebandowan area, the contact is ex- tensively faulted with north-dipping mylonite zones showing reverse displacement The deformation which produced these structures during juxtaposition of the subprovlnces has been dated in the Shebandowan area at 2689- 2685 Ma (Corfu and Stott, 1986) To the east,

108 K D CARD

Wllhams (1987, in press) described the Wawa-Quetlco interface as a zone of highly deformed, disrupted gabbro, anorthosIte, and mafic gneiss bodies enclosed in metasedlmentary migmaUte with mylomtes displaying evidence ofdlp-shp and strike-slip components of movement.

The contact between the Wawa Subprovlnce and the KSZ is a 10 km wide gradatlonal zone displaying structural, hthologtc and metamorphic continuity albeit with some faulting. Co- res od domal structures in the eastern Wawa Subprovmce have upper amphlbohte facies gneiss that continue uninterrupted into the KSZ where they are mlgmatlUC granuhtes with structures typical of the KSZ Within the transition zone metamorphic grade changes gra- datlonally from amphlbohte to granuhte facies and structural style from domal to consistently northwest-dipping gneIssoslty (Percival and Card, 1983; 1985)

Supracrustal rocks

Greenstone belts of the Vermlhon and She- bandowan areas in the west (Fig. 2) and the Hemlo and Mlchlplcoten areas m the east (Fig 4) form about 35% of the Wawa Subprovlnce and consist of approximately 60% tholentlc and komatntlc mafic volcanics, 20-25% calc- alkahc and tholentIc felsic, intermediate, and mafic volcamcs, 15-20% metasedlments, and minor alkahc and shoshonmc volcanics

The Vermilion belt consists of thick lower sequences of pillowed tholentIc and calc-alkahc basalt, andeslte, and minor daote with jaspditlc ironstone overlain by mixed calc-alkahc felslc pyroclastlcs, mafic lavas, and ironstone, turbldltlC wacke, and conglomerate, all capped by calc-alkahc felsic volcanlcs in the east and by tholeutlc and calc-alkahc basalt, andeslte, komatnte, ironstone, and marble in the west (Sims, 1976, Shulz, 1980) Their geochemistry indicates that the volcanic rocks represent mantle-derived, juvenile crustal additions The basalts are similar to low-K tho-

lentes of Cenozoic island arcs, and the calc-alkahc felslc volcanlcs may have been derived by partial melting of tholentlc basalts at mantle depths (Goldlch, 1972, Arth and Hanson, 1975)

The Shebandowan belt has two lower mafic- felsic cycles of tholentic basalt with minor komatnte, mafic-ultramafic intrusions, and andesite with minor felsic volcanlcs and ironstone overlain by daclte and rhyolite tufts and flows (Shegelskl, 1980). A daclte is 2732 Ma (Corfu and Stott, 1986). This sequence is unconformably overlain by the Shebandowan Group of volcamc-clast conglomerate, crossbedded arkose, mudstone with ripple marks and desiccation cracks, ironstone, and dacite-andesIte pyroclast~cs and scoriaceous flows with calc-alkahc dlfferentlon trends and shoshonitlC affinities. A tonahte clast from conglomerate is 2704 Ma and a daclte flow 2689 Ma (Corfu and Stott, 1986).

The Hemlo belt also comprises several mafic-felsic volcanic cycles with numerous mafic-ultramafic intrusions and metasedlments, chiefly volcanogenic wacke and ironstone. There is a general west to east facies transmon from coarse pyroclastlcs to eplclas- tic sediments in the upper part of the sequence (Muir, 1985) The Hemlo gold deposits occur m a shear zone within this transition Felslc volcamcs are 2770 Ma and 2695 Ma (Corfu and Muir, 1989a, b).

The Mlchiplcoten belt has at least three blmodal mafic-felslc volcanic cycles with intercalated clastlc and chemical sediments, notably carbonate-facies and sulphlde-faoes ironstone (Goodwln, 1962; Sage, 1987) Two older cycles have tholeimc basalt and andeslte overlain by calc-alkahc daote and rhyolite The basalts are similar to oceanic island-arc tholel- ltes whereas the andesites are high alumina and LREE enriched. Some daotes are similar to the andesltes, whereas others have depleted HREE (Sylvester et a l , 1987) The youngest cycle, separated from the lower cycles by clastlc metasedlments of the Dot6 Group, includes tho-

SUPERIOR PROVINCE OF CANADIAN SHIELD PRODUCT OF ARCHEAN ACCRETION 1 0 9

Fig 4 Geology of the southeastern Superior Province l=Abmbl belt, 2=Algoma bathohth, 3=Batchawana belt, 4=Belleterre belt, 5=Bell River complex, 6--Broadback River belt, 7=Cadillac Group, 8=Chapleau block, 9=Ch~bougamau pluton, 10=Cummings complex, ll=Fraserdale-Moosonee block, 12=Frotet-Evans belt, 13 = Gamltagama belt, 14 = Gamltagama complex, 15 = Granada Formation, 16 = Groundog Rsver block, 17= L'apparent gneiss, 18 = Lac Dot6 complex, 19= Lac Frechette pluton, 20 = Lac Slmard pluton, 21 = Latuhp bathohth, 22 = M lchlplcoten belt, 23 = Mongoose Lake pluton, 24 = Muscocho pluton, 25 = Opemlsca pluton, 26 = Otto pluton, 27= Pontmc Group, 28=Prelssac-Lacorne bathohth, 29=Rlvlere Outaoums complex, 30=Round Lake bathohth, 31=Shawmere complex, 32 = Timlskammg Group, 33 = Watabeag bathohth, 34 = Wawa gneiss

leutes, minor komatnte , and calc-alkahc volcanlcs, both low- and high-silica rhyolite with depleted H R E E and no Eu anomalies Sylves- ter et al ( 1987 ) noted similarities between the MlchlpIcoten volcanics and those of the Taupo, New Zealand and Kermadec-Tonga regions of the Pacific. Felslc volcanlcs from the lower cycles are 2749 Ma and 2744 Ma, and from the upper cycle, 2698 Ma and 2696 Ma (Turek et a l , 1984) Still older volcanlcs have ages of 2889 Ma and 2881 Ma (Turek et a l , 1988)

Chemical sediments of Mlchiplcoten belt include oxide (magnet i te -cher t ) , carbonate (s ider i te-cher t ) and sulphide (pyri te) facies ironstone The thxck Helen iron formation caps a mafic-felslc volcanic cycle and comprises a lower siderite member , a middle pyritic car-

bonate member , and an upper cher t -carbonate member capped by black graphitlC, pynt tc shale The ironstone is considered to have formed in a submarine cauldron environment by hotsprlng actlvtty and bacterial reduction of sea-water sulphate (Goodwln et a l , 1985 )

Clastlc metasedlments of the Dot6 Group that unconformably overlie volcanic rocks are mainly coarse conglomerate in the west and conglomerate, wacke, shale, and crossbedded arkose In the east (Attoh, 1981) A tonahte clast from conglomerate is 2698 Ma (Corfu and Sage, 1987 ), similar to ages of underlying felsic volcanlcs and intrusions (Krogh and Turek, 1982, Turek et a l , 1984)

The satelllt~c Gaml tagama greenstone belt consists of mafic and felslc metavolcanlcs and

110 K D CARD

metasedlments with an aggregate thickness of about 4500 m (Ayres, 1983) Lower and upper massive and pillowed basalts are low-K tholentes with flat REE patterns and no Eu anomalies (Smith et al., 1985 ). The felsic volcanics are LREE-ennched, HREE-depleted calc-alkahc rhyodaclte and rhyolite 2713 Ma old Correlative metasedlments are volcanogenlc.

Plutonlc rocks

Bathohths of the western Wawa subprovlnce, Including the Saganaga-Northern Lights, Sunbar-Batwlng, Manltouwadge, and Pu- kaskwa complexes, consist mainly of tonahtic gneiss with variable amounts of mafic enclaves of volcanic and dyke origin (Percival et al , 1985) Tonahtes have REE patterns sugges- tive of derivation by partial melting of a thol- eiltiC parent at mantle depths (Arth and Han- son, 1975)

Early synvolcanic to synkinematlc plutons are mainly quartz diorite, trondhjemlte and granodiorite, one, the Shebandowan pluton, has an age of 2696 Ma (Corfu and Stott, 1986) Late- to postkinematlc plutons in the Sheban- dowan area are 2684 Ma (Corfu and Stott, 1986) and near Hemlo, 2674 Ma (Corfu and Muir, 1989a) The late kinematic Giants Range bathohth of the Vermilion district is monzogranite with a low Imtlal Sr ratio, LREE enrichment, HREE depletion, and a negative Eu anomaly Late syenite-diorite plutons have high Mg numbers and Sr, Ba, and LREE contents typical of"sanukItolds" derived by partial melting of LILE-enriched mantle sources (Shirey and Hanson, 1984 )

Gabbro, monzogranlte, and syenite Intru- sions In the east include early synvolcanic plutons ranging from 2745 Ma to 2699 Ma and later, synkinemat~c to post-kinematic plutons ranging from 2694 Ma to 2662 Ma (Krogh and Turek, 1982, Turek et al , 1984, Sullivan et al , 1985, Frarey and Krogh, 1986) Early tron- dhjemitlC intrusions have high A12Oj, low SIOE,

depleted HREE, low initial Sr ratios, and were probably derived by partial melting of basaltic sources The younger plutons are commonly granitic, have high K, higher initial Sr ratios, low total REE, enriched LREE, depleted HREE, negative Eu anomalies, and were probably derived from partial melting of siliceous granuhte or greywacke (Smith et a l , 1985 )

The Wawa bathohthlc complex consists mainly of tonahte gneiss with kilometre-scale mafic metavolcanxc enclaves forming promi- nent xenohth-rlch zones. Metasedimentary enclaves near Borden Lake include stretch-pebble conglomerate and wacke The gneiss is cut by concordant to discordant bodies of granodiorite, granite, syenite, and pegmatite The age of zircons in the Wawa gneiss complex decrease systematically from about 2707 Ma or older In the west to about 2650 Ma or younger in the east near the Kapuskaslng structural zone Sphene and monazlte have ages of 2649- 2642 Ma A granodlorlte intrusion is 2677 Ma, late granites 2633 Ma and 2637 Ma, and a tonallte cobble from Borden Lake conglomerate is 2664 Ma (Percival and Krogh, 1983; Krogh et al., 1986b) Conversely, near Wawa, a granite is 2888 Ma (Turek et al , 1984)

Structure and metamorphism

Structural studies in the Vermilion district by Hooper and Ojakangas (1971), Bauer (1985) and Huddleston et al (1988) indicate that early deformation, for which there IS little fabric evidence, resulted in recumbent, nappe- style folding of supracrustal sequences of both the Vermilion greenstone belt and the adjacent Quetlco Subprovince A second, polyphase event, accompanied by low-pressure greenschist to amphlbohte facies metamorphism resulted in upright, moderately to steeply plunging folds with axial plane foliation and steep hneatIon Increasingly brittle late deformation led to further folding and formation of kink bands, shears, and dextral faults The polyphase deformation represents a single major

SUPERIOR PROVINCE OF CANADIAN SHIELD PRODUCT OF ARCHEAN ACCRETION

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transpresslonal event with north-south short- enlng and dextral shear with a north-side-up component of displacement compared by

Huddleston et al (1988) to deformation m Phanerozoic orogens attributed to oblique accretion of hthosphenc plates

112 K D CARD

Stott and Schnelders (1983) described the structure of the Shebandowan belt in terms of a southern domain characterized by a single, early (DI) generation of upright, northwest- plunging folds w~th weak to moderate axial planar foliation and axial hneatlon, and a northern domain in which the early (D1) folds are affected by a second (D2) event resulting in tight to lsochnal, east-plunging structures with well-developed fohations and hneatIons and numerous high strain zones The early (DI) event is attributed to diaplric uprise of the bathohths and is placed at approximately 2696 Ma, the age of the Shebandowan pluton. The second (D2) event, which is ascribed to regional transpresslon involving northwest- southeast compression and simple shear, is bracketed between 2696 Ma, the age of the Shebandowan pluton, and 2684 Ma, the age of the post-kinematic Burchell Lake pluton D2 was probably contemporaneous with TlmlS- kamlng-type volcanism at 2689 Ma and was accompanied by low-grade regional metamorphism

The Hemlo rocks have been multiply deformed and regionally metamorphosed at grades ranging from greenschist to upper amphibohte facies Walker (1967) demonstrated a northward increase in metamorphic grade In the central part of the belt where he mapped biotite, garnet, and silhmanite isograds in metasediments The isograds are not obviously related to granitoid bathohths but rather increase toward the Quetlco SubprovInce boundary Major structures include east- and north-trending, upright lsochnes and east- and northwest-striking faults There are well-developed, east-west, dextral shear zones with subhorizontal stretching hneation and mylonItlC fabric in the Hemlo area

Michiplcoten and Gamitagama belts have been metamorphosed under low pressure greenschIst and lower amphlbolite facies con- dItlOnS (Ayres, 1969, Studemeister, 1983), have undergone at least two periods of folding, and are cut by north-trending sinistral faults

Mlchiplcoten belt is crudely syncllnorlal with east-west to northwest trending lsochnal folds, at least three regionally developed fohatlons, macro- and meso-scale recumbent folds, thrusts, and major overturning of stratigraphlc sequences (Attoh, 1981 ) Llthologlc units are commonly bounded by bedding-parallel faults that were active early in the evolution of the belt when recumbent folding and overturning occurred Later NW-SE shortening caused steepening of dips, development of steep cleavages, and pervasive shearing (McGill and Shrady, 1986 )

In the Wawa gneiss complex, metamorphic grade increases eastward from low amphlbollte facies (hornblende-plagloclase) to upper amphlbollte (gamet-chnopyroxene-hom- blende-plagloclase) facies near the KSZ The gnelsses form domes with culminations at 25- 30 km intervals Minor folds and stretching hneatlons are generally incongruent with the domal structures, and this together with evidence for multiple deformation such as rootless intrafohal folds and discordant internal foliation in xenohths suggest that the domal structures are the product of superimposed folding events, not simple dmplrism Steeply dipping gnelssoslty IS transected and rotated by zones of flat-lying fohation, possibly the result of ductile extension (Moser, 1988 )

Kapuskasing Structural Zone

An Archean crustal cross-section

Kapuskaslng Structural Zone (KSZ) is a discontinuous, partly fault-bounded, northeast-trending zone of high-grade gneiss marked by positive gravity and magnetic anomalies that cuts across the east-west trends of the lower grade, supracrustal-rlch subprovinces of the central Superior Province (Fig 4) Geo- physical anomalies associated With the structure extend northward into James Bay where they are abruptly terminated, possibly by faults of the Wlnlsk River system (Figs 6 and 9)

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The western boundary of the KSZ with the Wawa gneiss terrane has been described previously and may represent an exposed example of the Conrad mldcrustal seismic dlscontl- nmty (Peroval, 1986). Across the entire transmon, metamorphic pressures decrease from 7 to 9 kbar in KSZ granuhtes to 5-6 kbar m amphlbollte facies Wawa gneiss to 2-3 kbar m greenschxst facies metavolcanlcs of Mlchlp- lcoten greenstone belt (Percival, 1983, Stude- melster, 1983) Profiles and radlometrlc ages across this transxtlon show decreasing apparent ages with increasing paleopressure In zircon (2 7-2 62 Ga) and sphene (2 69-2 49 Ga) (Peroval and Krogh, 1983; Krogh et al., 1986b), K /At hornblende (2.69-2.48 Ga) and biotite (2 5-2.0 Ga) (Hunt and Roddlck, 1987 ) and Rb-Sr biotite (2.50-1.93 Ga) (Z E Peterman, pers comm., 1985). Furthermore, age gaps between systems with different block- lng temperature widen with increasing pressure

In the east, the contact between high-grade KSZ gneiss and low-grade greenstone and gramte of the Abltlbi Subprovmce, the Ivan- hoe Lake fault, comodes with a hnear magnetic anomaly and with paired high (KSZ)- low (Abltlbl) gravity anomalies. The fault is marked by seismic reflectors dipping approximately 35°NW (Cook, 1985) and is interpreted as a thrust (Percival and Card, 1983 ).

The southern part of the KSZ has moderately NW-dlpplng units of orthogne|ss, parag- ne~ss, and the Shawmere layered gabbro-anorthoslte complex These rocks were deformed and metamorphosed under upper amphlbohte to granuhte faoes conditions (700-800 ° C, 7- 8 kbar, Percival, 1983) KSZ tonalite gneisses have variable LILE contents, variable but mi- nor Rb relative to K depletion, slgmficant U depletion relative to Th, steep REE patterns, and fractlonated HREE (Rudmck et al., 1985 ). The highest grade KSZ rocks are slgmficantly depleted in K, Rb, Ba and U relative to their

lower grade equivalents in the Wawa Subprov- lnce (Ashwal et al , 1987) and in B and L1 relative to average upper crustal rocks (Shaw et a l , 1988) Fired inclusions m KSZ granuhtes are dominated by C02 and H20 (Rudmck et al., 1984)

The northern part of the KSZ, the Fraser- dale-Moosonee block, is fault-bounded and has been considered a "pop-up" similar to the Lar- amlde Ulnta Mountains of Utah (Percival and McGrath, 1986 ) The Groundhog River block of granulltes is interpreted as a perched thrust tip as it lacks a gravity anomaly

Kapuskasmg crustal cross-section

High-grade rocks of the KSZ represent the basal part of an oblique crustal cross-section, a 120-km wide zone extending from low-grade supracrustal rocks of the Mlchlplcoten greenstone belt metamorphosed at pressures of 2-3 kbar corresponding to depths of 5-10 km, through amphlbollte facies gneiss of the eastern Wawa Subprovmce metamorphosed at pressures of 4-6 kbar corresponding to depths of 15-20 km, to granullte facxes rocks of the KSZ metamorphosed at pressures of 8 + 1 kbar corresponding to depths of 30 km (Percival and Card, 1983, 1985, Percival and McGrath, 1986). This crustal cross-section comprises three megalayers. ( 1 ) an upper ca 10 km layer ofgreenschlst to amphlbollte faoes supracrustal rocks with abundant discordant plutons and steeply-dipping, commonly brittle, structures, (2) a 10-20 km Intermediate layer consisting ofgnelsslc plutomc rocks with domal and ductile extensional structures (Moser, 1988) and remnants of supracrustal rocks, all metamorphosed at amphlbohte facies, and (3) a lower layer of upper amphibollte to granuhte facies gnelsses of plutonlc and supracrustal origin, and metamorphosed bo&es of mafic, ultramafic and anorthosltlC rocks, all w~th ewdence for high-strain, ductile deformation. The crust beneath the southern KSZ is over 50 km thick, 10-5 km thicker than in adjacent areas (Bo-

SUPERIOR PROVINCE OF CANADIAN SHIELD, PRODUCT OF ARCHEAN ACCRETION I 15

land et al., 1988) This Moho bulge may be a crustal root supporting the dense near-surface granuhte slab

Geological relationships and geochronological data indicate that the KSZ rocks are Late Archean, essentially the same age as rock units of the adjacent subprovlnces. The KSZ could represent the basal part of a magmatlc arc where supracrustal rocks were progressively buried, probably both magmatlcally by volcanic accumulations and lntraplated tonahtlc intrusions, and tectonically by accretIonary processes. The pattern of decreasing radlometrlc age w~th depth may represent progressively slower cooling with depth followed by later thrusting and transport of a cool crustal slab toward surface, or, alternatively, to prolonged metamorphism and magmatlsm at depth with addition of mantle-derived material resulting in vertical accretion and crustal thickening (Corfu, 1987).

Uplift of the KSZ occurred m the Late Ar- chean and Early Proterozolc, possibly in response to remote compressional tectonlsm. North-trending dykes of the 2450 Ma Mata- chewan swarm (Heaman, 1988) cross the southern KSZ with only minor offsets, implying that major thrusting preceeded 2450 Ma.

Abitibi Subprovince

Home of the world's largest Archean greenstone belt

The Abitlbi Subprovince is dominated by the Abitibl greenstone belt, which, covering an area of over 85,000 km 2, is the world's largest relatively contiguous area of low-grade Archean volcanic and sedimentary rocks (Fig. 4). The Abitlbi belt is also one of the world's richest mining areas, in the past 100 years, over 100 million ounces of gold and major amounts of copper, zinc, silver, and iron ore have been produced from the Tlmmlns,, Karkland Lake, Noranda, Vol D'or, Matagaml, and ChIbou- gamau camps

The Abltibl belt, mainly because of its acces- slblhty, excellent state of preservation, and economic importance has been intensely stud- ied and explored Much of this work is sum- manzed in a hthostratigraphlc map of the belt published by Quebec and Ontario (MERQ- OGS, 1984) and in recent papers by Dlmroth et al. (1982, 1983a, b, 1984, 1985a, b), Hodg- son (1983), Gelinas and Ludden (1984), Al- lard et al ( 1985 ), Jensen ( 1985 ), and Ludden etal (1986).

The Abltibl Subprovlnce is bounded on the west by the KSZ and on the east by the Gren- ville Front Tectonic Zone, a zone of Protero- ZOlC faulting and cataclasis that forms the boundary between the Superior and Grenville provinces. North of the Abitlbl greenstone belt, orthognelss and plutonlc rocks with remnant greenstone enclaves are in ill-defined contact with paragneiss and orthognelss of the Opatica Subprovlnce In the southeast, the AbItIbI metavolcanlc sequences are m fault contact with Archean metasedlments of the Pontiac Sub- province. In the southwest, the Abitlbi Sub- province rocks are unconformably overlain by Early Proterozolc sediments of the Huronian Supergroup and Middle Proterozolc, Keween- awan volcanlcs and sediments

In the Abltibi Subprovlnce, the magnetic (Fig 6) and gravity (Fig. 7) fields reflect the surface geology with greenstone belts and tonahtic plutons having negative magnetic and positive gravity expression and gramtlc plutons positive magnetic and negative gravity anomalies. Major faults are expressed by discontinuities or steep gradients in the potential fields. Interpretation of the gravity field across part of the AbltibI greenstone belt and granitic batholiths indicates that the greenstone belts extend to depths of less than 5 km on average with deeper keels to 6-8 km. The bathohths are tabular, extending to depths of 3-5 km (Card et a l , 1984). Seismic refraction experiments suggest that the Moho topography is uneven and possibly deepens southward (Ludden et al., 1986) Recent seismic reflection experl-

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SUPERIOR PROVINCE OF CANADIAN SHIELD, PRODUCT OF ARCHEAN ACCRETION 1 17

ments revealed numerous shallow-dipping reflectors, possibly major thrusts.

Supracrustal rocks

The Abitlbi Subprovlnce consists of approximately 40% supracrustal rocks, concentrated mainly in the AbItlbl greenstone belt, but also m the Batchawana belt m the west, and 60% granItold rocks. Volcamcs and related Intru- sions constitute about 80% of the greenstone belts, metasedlments 20% Of the volcamc sequences, 70% are tholelltlC and 25% calc-alkahc with minor komatnt lc and alkahc vari- eties Goodwln (1977) estimated that the volcanic sequences of the southern Abltlbl belt consist of 55% basalt, 34% andeslte, 7% daclte, and 4% rhyolite Tholentlc and calc-alkahc volcanlcs each comprise about 40% of the southern sequences, alkahc volcanlcs 12%, and komatntes less than 10%.

The Batchawana greenstone belt consists of an older sequence of Fe-nch and Mg-nch thol- elltlC pillowed flows and sills that form an east- trending, fault-bounded homochne in the western part of the belt dlsconformably overlain by clastic sediments (Corfu and Grunsky, 1987 ) A younger sequence of mixed tholelitlc and calc-alkahc flows and breccms with abundant interflow sediments and tufts and conformably overlying volcanogenic wacke and conglomerate forms the eastern part of the belt. A chert-magneti te iron formation lies between the upper and lower sequences. Felslc volcanics have ages ranging from 2729 Ma to 2698 Ma. Corfu and Grunsky cited the lack of inheritance in the zircon isotopic system as evidence that the rocks were formed from juvenile mant le-denved material

The Abltlbl greenstone belt comprises several major volcanic cycles, some consisting of a lower ul tramafic-mafic division, a middle tholentlc basalt division, and an upper diverse tholentlC and calc-alkahc mafic- lntermedi- ate-felsic division. Locally, there is an unconformably overlying alkahc-shoshonit ic dlvi-

slon that includes the Tlmlskamlng Group and similar sequences (Dlmroth et al., 1982; Jen- sen, 1985 ) These sequences form three major types of physiographic elements, submarine lava plain, submarine to subaerial central volcanic complexes, and subaerial to submarine rift basin fill. Submanne lava plains, formed of both komatlmC and tholentlC flow sequences, and little else, are 5-7 km thick, have broad lateral extent, and low rehef. Individual flow units are traceable long distances and were probably erupted mainly from fissures under relatively deep-water conditions (Dlmroth et al., 1985a) Komatnt lc pyroclastlcs present in the Val d 'Or and Tlmmlns areas suggest that not all komatlltlC volcanism represents fissure eruptions. The submarine lava plato accumulations, formed of stacked, overlapping, thin but extensive flow units, are similar in many ways to Cenozoic subaerial sequences such as those of the Snake River Plain, Idaho, similar Cenozoic oceanic lava plains have been described near Hawan (Holcomb et al., 1988).

The central volcamc complexes, commonly about 30 km in diameter, are composed of tholentlc and calc-alkahc sequences character- lzed by concentrations of felslc volcanlcs of both subaqueous and subaerial pyroclastlc or- lgm (DeRosen-Spence et a l , 1980; Goodwm and Rldler, 1970, G6hnas and Ludden, 1984 ). Some central volcanic complexes are s~mple shwld volcanoes but most comprise a number of overlapping and coalescing volcanoes. There are abrupt but systematic proximal-distal faoes and thickness changes related to distinct volcanic centers. Individual flows have lateral extents of a few kflometres, features such as lava lakes and calderas are present, and many central volcamc complexes are cored by synvolcanic plutons

Dlmroth et al. (1982, 1985a, b) compared the physiographic evolution of Abitlbl belt to modern island arcs. Submarine fissure eruption of komatntes and primitive low-K tholel- Ites formed submarine lava plains of immature, submarine, volcanic arcs Eruption of

1 1 8 K D CARD

calc-alkalic and tholentlc lavas and pyroclas- tics formed edifices within central volcanic complexes which were built up to sea level Maturation of the island arcs through continued volcanism, plutonism and crustal thickening led to emergence of volcanic islands Erosion, accompanied by voluminous pyro- clastic eruptions, resulted in formation of aprons of volcaniclastlc debris and turbidltiC sediments, shed into neighbouring submarine basins In some areas, extension led to rifting, uplift, erosion and deposition of coarse clastic debris Dimroth et al. (1985a, b) noted that modern island arcs and the Abitlbl belt are comparable in many ways, including linear distribution of volcanic centres, volcanic and sedimentary asymmetry, volcanic rock chem- IStry, evolutionary histories, and paucity of shallow-water sediments Dlmroth (1985) es- t imated that the rate of magma emplacement in Abltlbi belt was comparable to that of Me- sozoic-Cenozoic island arcs, implying large- scale crustal recycling in both t ime periods

Komatntes form parts of thick sequences of ultramafic and mafic flows and intrusions with minor felslc tuffs and chert None of the komatntes have been directly dated but they probably belong to two age groups, one older than 2725 Ma, the other 2715-~2700 Ma. Rhyohte at the base of a komatut lc sequence in the Lake Abitibi area is 2714 Ma and a pyroclastlc unit near Karkland Lake is 2705 Ma (Corfu et al., 1989) Interlayered perldotitic, pyroxenitIC, and basaltic komatntes with Mg- and Fe-rich tholentes form cycles ca. 1 km thick which extend over large areas. Komatn te flows are characterized by olivine and pyroxene spinifex texture, and polyhedral jolntlng. Some flows are layered with a lower cumulate zone, central spinifex zones, and an upper, chilled, polyhedrally jointed zone (Pyke et al., 1973 ). Thick layered perldotitic flows (Arndt, 1977) merge with sill-like layered mafic-ultramafic complexes. The geochemistry of Abitibl ko- matlItes has been investigated by Arth et al (1977), Dupr6 et al (1984) and Barnes

( 1985 ) who concluded that they were derived from partial melting of mantle sources depleted in LIL, LREE, and incompatible elements Catell et al. (1984) found some koma- txltes depleted in A1203, LREE and HREE whereas others are A1EO3-undepleted with flat HREE and depleted LREE patterns They attributed these differences to mixing of melts derived from heterogeneous, variably-depleted mantle sources, a conclusion shared by Ludden and Gelinas (1982). Arndt and Nls- bet (1982) found Abltibl komatntes and ko- matntIc basalts depleted in T1, Zr, and LREE, Mg-basalts enriched in incompatible elements and with flat REE patterns, and Fe-tholentes enriched In Zr, T1, Y, and LREE. The geochemical differences indicate different magma sources for the interlayered komatntes and tholentes, all were probably derived from heterogeneous, variably depleted mantle sources.

The thick tholentic sequences that form the lower and middle parts of major volcanic cycles throughout Abitibi belt consist mainly of pillowed and massive basalt flows with minor dacltlC, rhyolitic, and sedimentary units. Both Mg- and Fe-, quartz-normative and olivine- normative tholentes are similar to MORB in their major and trace element compositions (Goodwln and Smith, 1980) They have un- fractIonated REE patterns, are LILE depleted, and were probably derived from weakly depleted mantle sources (Ludden et al., 1986 )

In the northern Abitibi belt, large layered gabbro-anorthosite complexes intrude the lower tholentlc sequences The Lac Dor6 complex (Allard et al., 1985) near ChIbougamau is a 5 × 50 km intrusion consisting of a lower zone of cyclically repeated anorthosite, gabbroic anorthoslte, and gabbro units, a layered zone of ferrogabbro, pyroxenite, gabbroic anorthoslte, a vanadium-rich magnetltite unit, a sodic granophyre zone, and an upper border zone of gabbro and gabbroic anorthosite The complex is 2725-2728 Ma old (J Mortensen, pers. comm., 1987) The Cummings complex near Chibougamau, consists of three separate


layered sills, a lower dunlte-perldotlte sill, a middle pyroxenlte-gabbro-granophyre sill, and an upper gabbro-pyroxenite-ferrodior- ite-granophyre sill.

The differentiated, calc-alkahc and tholei- 1tic felslc-mafic volcanic sequences that form the central complexes range in age from about 2720 to 2709 Ma with a second major pulse represented by the Blake River Group at 2703- 2697 Ma (Nunes and Jensen, 1980; Nunes and Pyke, 1981, Mortensen, 1987, Corfu et al , 1989 ) Several of these sequences, for example the Blake River Group, consist of lower thol- elltlC basalt and andeslte and upper calc-alkahc basaltic to rhyolitic lavas and pyroclas- tics The transition from tholentic to calc- alkahc volcanism is abrupt and marks a change from tholentes with LILE depletion and unfractionated REE patterns resembling oceanic basalts to calc-alkahc volcanlcs resembling modern oceanic island andesites (Baragar, 1968) that are LILE undepleted, LREE enriched, and HREE depleted. Goodwln and Smith (1980) suggested that the transition marks a change from melts derived from depleted mantle sources to melts derived from mantle unmodified by crustal additions Cap- devila et al (1982) suggested that the transition marks a decrease in the depth of melting, and increase m the degree of partial melting and fractional crystallization. Ujike and Goodwln ( 1987 ) concluded that felslc volcanlcs in the Noranda area are products of frac- t~onation of mafic magmas in extensional settings similar to the Miocene Japan Sea

Alkahc and shoshonitic volcanics form parts of the Timlskaming Group (Cooke and Moor- house, 1969) and the Hatiy Formation (P1- card and Piboule, 1986) in the southern and northern parts of Abitibl belt respectively The Tlmlskaming volcanics, Including trachyte, trachyandesite, leucltite, and mugearlte, form four, dominantly subaerlal flow and pyroclas- tic units They have highly fractlonated REE patterns with LREE enrichment suggesting derivation from enriched mantle sources

(Capdevila et al., 1982, Basu et a l , 1984). Ujlke (1985) concluded that the Timlskam- ing volcanlcs are chemically similar to modern alkalic volcanlcs of mature island arcs implying the TimiskamIng represents the last stage of island arc volcanism in settings similar to modern arc systems. The Tlmiskaming volcanlcs and associated fluvial conglomerate and sandstone were deposited about 2680-2700 Ma ago, Basu et al (1984) have determined a Nd/Sm age of 2702 + 105 Ma on Timlskamlng volcanlcs The Tlmiskamlng Group, like other similar sequences in Superior Province, is associated with a major subprovince boundary fault, the IOrkland Lake-Cadillac fault that forms the contact between the Abltibi and Pontiac subprovlnces In the Noranda-Val D'or region

Pelagic and chemical sediments, including oxide, sulphide, and carbonate ironstone, chert, and mudstone form thin, laterally persistent units within the lower submarine lava plain accumulations Resedimented or turbidltlC facies wacke, conglomerate, siltstone, and minor iron formation form thick, widespread units, notably within and about the central volcanic complexes Some of the conglomerates are composed solely of volcanic debris whereas others are rich in plutonic material presumably derived from erosion of synvolcanic plutons. Some sequences show transitions from shallow manne through slope to submarine fan facies (Mueller and Dlmroth, 1984) Alluvial and fluvial sediments have been described by Hyde (1980) and Dlmroth et al (1982) as forming the lower parts of predominantly tur- bIditic sequences, or as lateral facies equivalents of turbldltes. However, most of the alluvial-fluvial sediments form parts of Timlskaming-type sequences which unconformably overlie the older volcanic sequences and hence may be younger than the turbidltes. The Timiskamlng Group and similar sequences such as the upper part of the Porcu- pine Group near Timmins, the Duparquet and La Bruere formations near Noranda, and part

120 K D CARD

of the Opemisca Group near Chlbougamau, are coarse conglomerate, conglomeratic sandstone, and argalhte with numerous unconformities, rapid vertical and lateral facies changes, large-scale cross-bedding, and locally derived clasts, both from underlying older sequences and from within the younger sequences themselves Alkalic and shoshonltiC flows, brecclas, and hypabyssal intrusions form parts of these sequences and their erosion has contributed clastlc debris. Most Timiskamlng-type sequences are spatially related to major faults such as the Karkland Lake-Cadillac and Por- cupine-Destor structures

Plutontc rocks

Early, pre-klnematlc tonahte gneiss forms batholithlc complexes in and around the greenstone belts, contain mafic volcanic enclaves, and are intruded by syn- and post-kinematic plutons In the L'apparent complex, Raclcot et al. (1984) recognized multiple deformatlonal and intrusive events and suggested that some old, pre-greenstone plutonlc rocks are present. Pre- to synkinematic quartz diorite, tonallte, and granodlonte plutons are commonly similar in chemistry and age to associated felsic volcanics and form the cores of central volcanic complexes. The 2689 Ma (Mortensen, 1987 ) Round Lake tonalite bathohth which intrudes Abitibl greenstones near Karkland Lake displays trondhjemitlC differ- entlatlon trends, LREE ennchment, and a negative Eu anomaly (Lafleur, 1985) The Chi- bougamau dlorite-tonahte pluton, which intrudes lower volcanics and is unconformably overlain by an upper sedimentary sequence, is 2717 Ma (Krogh, 1982)

Late- to post-kinematic granodlorlte and monzogranite intrusions that interrupt structural trends and commonly have amphlbohte facies metamorphic aureoles range in age from 2699 to 2673 Ma (Frarey and Krogh, 1986, Corfu and Grunsky, 1987) SyenltiC plutons, including both quartz- and nephehne-beanng

syemte as well as monzonite, diorite, and pyroxenlte, are mainly massive, post-kinematic intrusions with ages of 2678-2668 Ma (Corfu and Grundsky, 1987, Corfu et al., 1989) Some may be similar in age to the Timlskamlng alkahc/shoshonltiC volcanlcs Small porphyritic felsic intrusions in the Tlmmlns area, some of which contain lode gold deposits, intrude folded volcanic rocks but are themselves deformed and altered, have ages ranging from 2691 to 2688 Ma (Corfu et a l , 1989) Major folding thus occurred before 2691 Ma and was followed by shearing and formation of gold deposits.

Structure and metamorphtsm

AbltIbl greenstone belt has major domal an- tlforms, commonly cored by granitic bathol- lths, and synforms occupied by thick volcanic sequences such as the Blake River Group DImroth et al. (1983a), Jensen (1985) and others have suggested that this pattern was es- tabhshed at an early evolutionary stage with domes initiated by the formation of central volcanic complexes and synchnorla by synvolcanlc normal faulting Gibson et al (1986) postulated that Abltlbl volcanism occurred in an extensional tectonic regime not unlike those in which modern backarc basins and island arcs develop Significant synvolcanlc extension led to listrlc normal faulting, subsidence and tilting, resulting in steeply-dipping homochnal sequences of great apparent thickness but limited depth extent and uniformly low metamorphic grade. It is also possible that these structures are not formed by large-scale folding of thick stratified sequences, but rather by thrusting and juxtaposition of diverse sequences. Corfu et al ( 1989 ) cited geochronological evidence that the two limbs of the Blake River syncllnonum are not correlative. The greenstone sequences have isochnal to open folds that are the products of at least two phases of deformation Near Timmins, the Shaw done and Porcupine synform are polyphase struc-


tures with early major folds that predate formation of younger east-west lsocllnes The older folding also predates deposition of Tim- lskammg-type sediments The younger folds, which post-date the sediments, have axial plane foliation and east-plunging llneatlon and are overprinted by crenulat~on cleavage and shears

The Abitibl greenstone belt in the IOrkland Lake area is divided into a number of weakly deformed domains, each hawng distinctive hthologlcal and structural characteristics, by narrow, hnear high-strata zones characterized by strong cataclastic fohatlon, mylomtes, and faults (Toogood and Hodgson, 1986). Shear- related S-C fohatlon patterns and displacements m the shear zones indicate late dextral transcurrent movement In the Noranda area, doubly-plunging first-order synchnorla and antlchnoria are composed of folds with subvertical, east-west trending axml surfaces and steep plunges These structures were formed by superposmon of east-west folds on early folds of variable trends The central parts of the major synchnoria and ant~clinoria are low strata zones whereas the margins are highly strained, commonly faulted, zones Hubert et al (1984) emphasized the importance of wrench fault- rag, speofically smlstral strike-shp movements on the Porcupme-Destor and Klrkland Lake-Caddlac faults, in the tectomc evolution of the Noranda area However, Dimroth and Rocheleau (1985) and Archambault (1985) pointed out that regional fold trends and hneatlon attitudes are not consistent w~th sinlstral wrench-faulting but are more hkely the products of nor th-south compression of a heterogeneous, anlsotropic regmn Hubert and Lud- den (1986) further emphasized the role of wrench faulting with the development of loz- enge-shaped domains bounded by faults and h~gh strain zones that juxtaposed different htho-tectonlc domains to form a collage of tee- tonically accreted blocks

Major east-west faults such as the Porcu- pme-Destor (PD) and Klrkland Lake-Cadil- lac (KLC) structures form boundaries be-

tween domains of contrasting structural and metamorphic characteristics They also control distribution of some rock units, notably Timiskamlng-type sequences and porphyry dykes. Dimroth et al. ( 1983a, b) described the PD as a dextral transcurrent fault and the KLC as a steep north-dipping thrust Robert ( 1989 ) described the KLC in the Val d 'Or area as a high strain zone dipping 80 ° north with an early DI foliation oblique to the zone boundaries with subvertical elongation llneaUon and subhorlzontal to subvertical folds indicating d~p-slip Later D2 strata characterized by moderately to steeply plunging asymmetric folds and associated cleavage records dextral transcurrent shearing. Robert interpreted the KLC as a dextral transpressive structure that evolved from a zone of shortening into a zone of transcurrent shearing

The AbItlbl greenstone belt is notable for its generally low grade of metamorphism, much of the belt ~s in low greenschlst facies and large areas are m subgreensch~st, prehni te-pumpel- lyxte facies (Jolly, 1978; Fraser et al , 1978, Fig 8) Only in contact metamorphic aureoles about gramtic intrusions are grades of upper greenschlst and lower amphlbolite, or hornblende hornfels, reached Jolly (1978), Dlm- roth et al (1983b), and Gehnas et al (1982) recognized several different types and ages of metamorphism, including early sea-floor metamorph | sm and metasomatlsm, locahzed hydrothermal metasomat~sm related to vol- canogemc massive sulphldes, and burial metamorphism SynkInemat~c regional metamorphism related to plutonIsm resulted in formation of low-pressure greensch~st and amphlbohte facies assemblages There was also widespread late metasomaUc carbonat~zation, sericmzatlon, and slhclficatlon, notably along faults and shear zones Ductile deformaUon and metamorphism began in Abitlbl belt, judging from the zircon ages of the youngest deformed volcamc rocks, approximately 2700 Ma ago Late, increasingly brittle deformation persisted until about 2680 Ma, the age of late-

122 KD CARD

to post-kinematic plutons, and was probably coeval with Tlmxskaming volcanism and sedimentation.

Pontiac Subprovince

A Late Archean metasedlmentary terrane m the southeast

The Pontiac Subprownce is bounded on the south and east by the Grenville Front Tectomc Zone, and on the north by the Karkland Lake- Cadillac (KLC) fault (Fig 4). In the northwest, a narrow trough of Proterozolc sediments probably covers a major north-trending fault that juxtaposes Pontiac metasedlments with Abltlbl metavolcanics (Kalhokoska, 1987)

The Pontiac Subprovince has a northern zone of low- to med ium grade metasedlments, the Pontiac Group, a central region of metasedlmentary gneiss and granitic intrusions, the Rivi~re Outaouais complex, and a southern area of low-grade metavolcanIcs, metase&- ments, and related plutonlc rocks, the Belle- terre volcanic domain (Fig 4).

Supracrustal rocks

In the north, turbidltiC wacke, pehte, and minor conglomerate of the Pontiac Group from a sequence at least 3 km thick exposed in an east-west belt approximately 15-20 km wide and 150 km long Where little metamorphosed and deformed, the rocks display primary structures such as graded beds, ripple cross- laminations, Bouma divisions, load-casts, and flames. Several cyclically-repeated facies include massive wacke with beds 30-60 cm thick, medium-bedded wacke (30 cm) with pehtlc lnterbeds and partings, and thin-bedded sequences with approximately equal proporUons ofwacke and pehte (Holubec, 1972 ) There are horizons rich in amphiboles, possibly metamorphosed carbonate-rich beds and concre- tions, along with minor amounts of lean oxide-

and sulphide facies ironstone and graphltlC schists. Lajole and Ludden (1984) noted that the Pontiac metasediments are rich in framework quartz and display southward decreasing average gram size and bedding thickness and Increasing sand/shale ratios They also found large variations in REE enrichment, LREE/ HREE ratios, and relatively high Cr, N1, and Sc abundances They concluded that the Pon- tiac sediments were derived from a complex source region to the north that had a high proportion of tonahtlc plutomc rocks Rocheleau and Dlmroth (1985) pointed out that the Pontiac greywackes are volcanogenlc with abundant matrix derived from breakdown of plagioclase and rocks fragments and compositions approximating andesxte and rhyodaclte Rocheleau and Dxmroth ( 1985 ) and Dlmroth et al ( 1982 ) considered the Pontiac, Cadillac, and T~miskamlng groups as correlatives, rep- resenting distal, medial, and proximal facies respectively of a northward and upward-coar- sening sequence Gari6py et al (1984) found several different types of detrltal zircons in Pontiac metawackes, some approximately 2714 Ma, others 2925-3000 Ma old They concluded that the sediments were derived mainly from 2 7 Ga volcamc and plutomc sources, but that there was a significant contribution from older, ca 3 0 Ga sources as well The ages of the youngest detrltal zircons dem- onstrate that deposition of the Pontiac sediments occurred after most, if not all, of the volcanism m the adjacent Abltlbl subprovlnce

In addition to the predominant wacke sequences, the Pontiac Group has local lnterbeds of polymict conglomerate with metavolcanic and metasedlmentary clasts, and monomic t greywacke pebble conglomerate (Goulet, 1978) Near or at the base of the sequence are mafic and ultramafic metavolcanics which have been tenuously correlated with various volcanic groups north of the KLC (Dlmroth et al., 1982)

In the north, Pontmc turbidItes are in contact with Tlmlskaming-type conglomeratic


sediments (Goulet, 1978; Dlmroth et al., 1982 ) These units, like the Timiskaming of the Karkland Lake area, unconformably overlie the Blake River Group Their southern contact with the Pontiac sediments, where not faulted, has been interpreted as an unconformity (Hol- ubec, 1972) and as conformable (Goulet, 1978, Dlmroth et al, 1982) The latter authors explain the conformable relationship between the Tlmiskaming and Pontiac, and the uncon- formable relationships between the Timls- kaming and Blake River, which they correlate with the Pontiac, as the result of repeated uplift north of the KLC fault and subsequent prograding of alluvial fans southward. It IS also possible that the Timlskamlng-type sequences are younger than the adjacent Pontiac turbldltes and may represent late alluvial/fluvial sediments deposited in pull-apart basins formed by transcurrent movements on the KLC.

In the Belleterre volcanic domain m the south, low-grade metavolcanlcs of the Baby greenstone belt unconformably overlie wacke and argilhte tentatively correlated with the Pontiac Group (Imreh, 1973).

Plutonlc rocks

In the central Pontiac Subprovlnce, gneissic, non-mlgmatltiC metasedlments and granltold intrusions in approximately equal proportions form the Rivi6re OutaouaIs complex (ROC) Plutonlc rocks include the 2695 Ma Lac des Quinze tonahte (Mortensen et al, 1988), numerous peralumlnous granite and pegmatite bodies with accessory muscovite, garnet, and beryl, and monzogranlte, granodlorlte, and syenltiC plutons Massive, post-kinematic syenitic intrusions which also intrude the lower-grade supracrustal sequences to the north and south, comprise syenite, syenodiorlte, and

gabbro (Van de Walle, 1978 ) and have ages of 2687 and 2678 Ma (Mortensen et al, 1988 )


Stratified rocks of the Pontiac subprovlnce have been folded about east-west isochnes with north-dipping axial surfaces and are cut by north-dipping faults (Van de Walle, 1978, Dimroth et al, 1983a) These south-verging structures are the product of polyphase deformation including early flexural folding, later ductde deformation, and still later brittle shearing and faulting, all under conditions of north-south compression In the higher grade ROC, the dominant structures are south-verging thrust imbrications and recumbent folds cored by granitic intrusions (Van de Walle, 1978, Cardet al, 1981)

Regional metamorphism that accompanied deformation increases southward from low greenschlst to upper amphibohte facies (Jolly, 1978 ) Kyanlte-, sllhmanlte-, and garnet-bearing assemblages indicate medium pressure Barrovian-type metamorphism In contrast to the low pressure Abukuma-type of Abitlbl belt The southward increase in metamorphic pressure-temperature is probably attributable to significantly greater uplift in the south and to heat effects of the numerous plutons

The ages of the pre- to synklnematlc Lac des Qulnze complex (2695 Ma) and the post-tectonic syenltlC plutons (2687 Ma) demon- strates that major deformation and metamorphism in the Pontiac Subprovince occurred at about 2700-2690 Ma, coeval with events in the Abltlbl Subprovlnce Pegmatltes from ROC have monazite ages of 2668 and 2663 Ma, demonstrating that higher temperature conditions persisted here later than in Abltibi subprovince The Pontiac Subprovince has rock types and structural-metamorphic patterns that are generally similar to those of Quetico subprovince and may, like Quetlco, represent an accretionary prism.

124 K D CARD

Quetico Subprovince

An accrettonary prism

The 10-100 km wide Quetlco metasedimentary belt extends 1200 km from beneath Pha- nerozoIc cover in Minnesota eastward to the KSZ in Ontario East of the KSZ, similar metasedimentary schists and gnelsses of the Opa- tica subprovince extend into Quebec (Figs. 2 and 4) The Quetico Subprovince has regional aeromagnetic (Fig 6) and gravity (Fig. 7) lows Seismic studies (Young et a l , 1986, Halls, 1982) indicate that the crust is 35-42 km thick, comparable to that of adjacent volcano-plutonic terranes. However, the mid- crustal discontinuity is about 18 km beneath the Quetlco versus some 30 km beneath the Wabigoon volcano-plutonlc terrane

The northern boundary of the Quetico Sub- province with volcanic and plutonic rocks of Wablgoon subprovince is largely faulted In the west, the Rainy Lake-Seine River fault system separates Quetlco metasediments from over- turned, polydeformed greenstone belt sequences of Wabigoon subprovlnce (Poulsen et a l , 1980; Blackburn et al., 1985). Conglomer- ate of the Seine Group occurs sporadically along the boundary, possibly in pull-apart basins in a dextral wrench zone (Poulsen, 1986) The Rainy Lake-Seine River system merges with the Quetico fault and this structure, characterized by a 100 km dextral displacement (Blackburn et a l , 1985), forms the boundary eastward toward Lake Nlplgon

Recent detailed studies by Kehlenbeck (1986) have defined the boundary in the Beardmore-Geralton area east of Lake Nipi- gon as a structurally distinct zone wherein displacement of refolded folds and older fabric elements along faults and shear discontinutles has resulted in a pseudostratigraphy of juxtaposed hthotectonic panels Williams (in press) described the Interface as fault-bounded panels of metasediments floored by basalts that represent separate, successively more distal seg-

ments of a prograding clastic wedge. Thin- skinned imbrication of these panels occurred along north-dipping thrusts that were originally at a shllow angle but rotated towards vertical by continued right-lateral convergence resulting in progressive internal shortening, lsochnal folding, metamorphism, plutonlsm, and crustal thickening in a regional transpresslve regime

Supracrustal rocks

The Quetico Subprovlnce has marginal low- to medium-grade and interior high-grade metasedlments Metavolcanic rocks, now mainly mafic gneiss, are minor The low-grade metasediments, thin- to medium-bedded wacke, sIltstone, and minor conglomerate, are turbI- dites, deposited mainly in distal fan environments (Wood, 1980) Most are arkosxc and hthIc wacke of both felsic and mafic volcanic provenance (Ojakangas, 1985; Sawyer, 1988 ) A mixed population of detntal zircons yielded ages ranging from 3009 to 2698 Ma (Davis et a l , in press) indicating that Quetico sediments are younger than any igneous activity in the Wabigoon or Wawa subprovInces except for late Timlskaming-type sequences and late plutonlsm Quetico sedimentation is bracketed between 2698 Ma, the age of the youngest detrital zircons, and 2688 Ma, the age of a post- kinematic pluton (Davis et a l , in press)

Gnetsstc and mtrustve rocks

Gnelsses of the interior parts of Quetlco subprovlnce were derived mainly from wacke and siltstone, display increasing metamorphic grade inward to upper amphibollte and granullte facies, and are commonly migmatitic

The oldest intrusions are rare tonahtes with mafic inclusions, granodionte sills, and bodies of amphlbohte and gabbro Younger leuco- granite with tonallte and mafic gneiss inclusions forms dykes and large complexes such as the Lac La Croix bathollth of the Vermilion


district (Southwick and Sims, 1980). The leu- cogranite is a potasslc, high-silica rock with low trace element and REE abundances indicating a tonahtic source

Peraluminous granite with metased~mentary inclusions is characterized by accessory muscovite, garnet, cordiente, sllllmanlte, and tourmaline Beryl and spodumene are present in associated pegmatites (Pye, 1965) Their peralumlnous composition, mineralogy, and low trace element and REE and high Ba and Be contents indicate there are S-type granites formed by anatexls of alumlnous sediments Monazite ages of 2671-2653 Ma for Quetlco granites and pegmatites (Percival and Sulli- van, 1988 ) show that major magmatism in the Quetlco Subprovince was later than that in the Wabigoon and Wawa subprovlnces


The Quetico subprovlnce has a straight, east- west trending, deceptively slmple-appeanng structural fabric that is primarily attributable to upright folds with a strong fohatlon into which hthologlcal layering has been transposed The planar fabric is at a high angle to, and superimposed upon, structures within the adjacent Wabigoon and Wawa volcano-plutonic subprovinces Furthermore, this fabric is developed throughout the Quetico Subprov- lnce and is commonly at a low angle to the belt boundaries (Williams, in press).

The Quetico metasedimentary sequences comprise mainly north-facing homochnal panels separated by zones up to 2 km wide with abundant folds and soft-sediment deformation features (Williams, 1987) Early isochnes are cut by a pervasive foliation and are refolded about shallow-plunging folds formed during or after migmatizatIon (Percival and Williams, 1989) The foregoing deformation is the result of major nor th-south shortening followed by dextral transpression under increasingly brittle conditions that culminated in dextral movements along the major boundary

faults and complementary oblique slnistral movement on the northeast-trending Gravel River fault. There is thus evidence in Quetlco subprovlnce, and in adjacent parts of the Wa- bigoon Subprovince, for early thin-skinned tectonism involving thrust juxtaposition of diverse supracrustal sequences followed by thick- skinned accretion culminating in strlke-shp faulting (Williams, in press)

Abukuma-type regional metamorphism accompanying and following the second phase of deformation and approximately coincident with granitic plutonism resulted in the metamorphic zonation from marginal greenschxst facies to interior low pressure amphibohte and granuhte facies (Fig. 8 ) The symmetrical patterns of metamorphism are consistent with structural thickening and differential uplift of the central parts of the belt Estimated metamorphic conditions are 500°C and 2 5 kb in the west and 700-780°C and 6 kb in the eastern and central parts (Percival, 1989) Perci- val estimated a geothermal gradient of 20- 3 7 ° C / k m between 7 and 18 km depth and a lateral thermal gradient of 50-100 ° C / k m The high gradients, the low pressure of metamorphism, and the t iming of regional metamorphism relative to granite emplacement indicate that metamorphic heat was supplied by rising anatectic magmas

Percival and Williams (1989) suggested that the Quetico belt represents an accretlonary prism with submarine fan and abyssal turbidites accreted onto the Wabigoon arc and later compressed by docking of the Wawa arc They compared the Quetlco-Wawa boundary with the Izu collision zone of central Japan where the Izu-Bonin arc impinges on the Honshu accretlonary complexes They ascribed the high- temperature metamorphism to conversion from a fore-arc to a back-arc setting dunng col- hsion Such a model is in accord with the relationships among the Quetlco, Wablgoon, and Wawa subprovinces, their tectono-magmatic histones, the evidence for early thin-skinned and later thick-skinned tectonlsm, the charac-

126 K D CARD

LEGEND

Unmetarnorphosed, weakly metamorphosed mtrusmns

I I Subgreenschmt facms

I I Greenschlst, lower amphlbohte facies

Amphlbohte facms

m Granuhte upper amphlbohte facies

~ - - ~ Retrograded granuhte facies HUDSON

BAY

,, \+ , + ~ c/+--+fD+J.~i

~+~ f['l//

/

1+/

Fig 8 Patterns of regional metamorphism

300 KM t J

tenstlcs of the Quetlco metasedlments, and the time constraints ( 10-20 Ma) on their deposition, deformation, and metamorphism.

Wabigoon Subprovince

A middle to late Archean volcano-plutontc terrane

The Wablgoon volcano-plutonlc subprovince, averaging 100 km wide, is exposed for some 900 km eastward from Manitoba and Minnesota, to beneath the Proterozolc cover of the N~plgon Embayment , to and beneath Pha- nerozolc cover of the Moose River basin (Fig 1 ) Gravity data (Fig 7) indicate greenstone

belts in the Lake of the Woods, Sioux Lookout, and Sturgeon Lake areas extend to depths of about 5 km, batholithlc complexes to 4-7 km and late plutons to about 2 km (Dusanowskyj and West, 1976, Bnsbln and Green, 1980) Se- ismic reflection and refraction studies reveal a three-layer crust, an upper 16 km layer with few reflectors, a middle layer ca 5 km thick corresponding to the mid-crustal velocity discontin- uously, and a lower layer with numerous reflectors extending to the Moho at a depth of ca. 38 km (Hall and Brisbln, 1982)

The Wablgoon Subprovlnce is bounded on the north by plutonlc and metasedlmentary rocks of the Winnipeg R~ver and Enghsh River subprovinces This boundary, generally placed


at the contacts between plutomc rocks on the north and supracrustal rocks on the south, has been variously interpreted as intrusive (Breaks et al , 1978 ), as a tectonically modified unconformity (Clark et al., 1981 ), and as a fault (Wilson, 1971, Blackburn et al., 1985, Davis et al , 1989)

The Wablgoon Subprovlnce consists of about 65% plutonic and 35% supracrustal rocks, including 60% tholentlc and minor komatntlC volcanics, 30% calc-alkahc and minor shosh- onltIC volcamcs, and 10% metased~ments A western greenstone domain in the Lake of the Woods-Rainy Lake-Savant Lake area is separated from an eastern greenstone domain in the Atikokan-Geraldton area by a plutonlc domain, the Wablgoon diaplriC axis (Edwards and Sutchffe, 1980)

Supracrustal rocks

The greenstone belts of the western Wabl- goon Subprovmce generally consist of lower mafic volcamc sequences (Keewatln Series of Lawson, 1885) overlain by mixed felsxc and mafic volcanics and turbldlUc sediments (Coutchiching Series of Lawson, ibid. ), all overlain unconformably by alluvial/fluvial sediments (Seine Series of Lawson, 1bid ) This stratlgraphic sequence is generally repeated throughout the Wablgoon Subprovince (Blackburn et a l , 1985) The lower mafic sequences are mainly subaqueous tholentlc basalts with some basaltic komatll te Some have MORB-hke chemistry and display slight LREE enrichment and minor Eu anomahes (Shlrey and Hanson, 1986) The ages of these sequences are poorly constrained, a felsic unit within the lower mafic sequence of the Stur- geon Lake belt is 2775 Ma (Davis and Trow- ell, 1982, Davis et a l , 1988)

Overlapping, more locahzed felslc, intermediate, and mafic calc-alkahc and tholentic sequences, in part subaerial, have high REE abundances, especially HREE, slight LREE enrichment, and negative Eu anomalies They

range from 2745 to 2703 Ma (Davis et a l , 1982)

Metasedlments of the western Wabigoon greenstone belts include thin xnterflow Iron- stone and shale units, and thicker turblditic wacke, siltstone, and conglomerate units, mainly in the upper part of the piles, and Tim- lskamlng-type alluvial/fluvial conglomerate and sandstone, commonly unconformably overlying volcanic rocks. In some sequences, alluvial/fluvial sediments unconformably overlying volcanlcs are in turn overlain by turbldltes (Turner and Walker, 1973, Teal and Walker, 1977) The petrography and chemistry of the turbldltes indicate a volcanic provenance, mainly 2 7 Ga dacitlC to basaltic volcanlcs with some contribution from ca 3 0 Ga crustal sources (Shxrey and Hanson, 1986) The turbidltlC sequences are coeval with, and derived largely from, the mixed volcanic sequences

The Tlmxskaming-type conglomerate-sandstone sequences, also containing siltstone, ironstone, and shoshonltlC volcanics, consist of locally-derived detritus The Seine Group occurs along the Quetico and Seine River faults which form part of the Wablgoon-Quetico subprovincial boundary The Seine Group was deposited between 2695 Ma, the age of a tonalite clast, and 2688 Ma, the age of a post-tectonic pluton (Davis et al , Creek conglomerate along Quetlco boundary west of

1986) The Max the Wablgoon-

Lake Nlpxgon IS younger than 2684 Ma, the age of a tonahte clast (Percival and Sulhvan, 1986), and alluvial conglomerate in the Sturgeon Lake belt in younger than 2698 Ma (Davis et a l , 1989)

The eastern Wablgoon greenstone belts are generally similar in hthology and age (2669- 2692 Ma, Anglln and Franklin, 1989) to those of the west except for the presence of ca 3 0 Ga supracrustal sequences in the Lumby Lake and Atlkokan belts The Lumby Lake belt consists of a lower blmodal mafic-felslc sequence with rare komatntes and an upper sequence of ironstone, stromatohtic marble, quartz aren-

128 KD CARD

lte, and argilhte These strata unconformably overlie the Marmion bathohth. Davis and Jackson ( 1988 ) obtained zircon ages of 3003 Ma for the batholith and 2999 Ma for overlying felslc volcanics. They also obtained an age of 2809 Ma on tltanite from the bathohth which they interpreted as evidence for an early metamorphic event.

In the Atikokan belt, a sequence of conglomerate, stromatohtic limestone, ironstone, and ultramafic tuff, the Steeprock Group, unconformably overlies the Marmion batholith (Jol- lffe, 1966, Wilks and Nlsbet, 1985). The similarities between the Steeprock Group and the Lumby Lake sequence suggest that the former is also of Middle Archean age and may represent an early rifted margin deposit (Davis and Jackson, 1988 )

Plutomc rocks

Plutonic rocks form large bathohthlc complexes both within and around the greenstone belts and can be subdivided into early, synvolcanlc ultramafic, mafic, and granltold intrusions, and later, syn- to post-tectonic granitold intrusions

Synvolcanic mafic intrusions include the Bad Vermilion Lake gabbro-anorthosite complex of the Rainy Lake area with a S m - N d age of 2747 Ma (Ashwal et al., 1985) and the Mulcahy Lake layered mafic intrusion with a age of 2733 Ma ( Moms on et al , 1985 ), similar to the 2732 Ma age of tonahte of the Atlkwa batholith (Davis and Edwards, 1982, 1986 ). Geochem- ical data indicate that the Mulcahy intrusion and associated mafic volcanlcs were derived from a depleted mantle source (Morrlson et al , lbid) The Lac des Iles complex, a platinum- bearing ultramafic-mafic intrusion (Sutchffe and Sweeny, 1985) has an age of 2693 Ma and the Beldleman Bay subvolcanlc t rondhjemite sill is 2734 Ma, similar in age and chemistry to the volcanic rocks it intrudes (Davis et a l , 1985)

The Wabigoon dlaplric axis (Thurston and

Davis, 1985) comprises several granitoid batholIths with greenstone remnants, now mainly amphlbohte and mafic gneiss, forming xenohth-rlch zones linking greenstone belts and forming septa between domal structures in the gneiss. The pre- to synklnematic gnelssic intrusions are mostly tonahte and granodlorite Contacts with greenstones are commonly highly strained but locally can be seen to be intrusive The intrusive rocks display limited compositional range, trondhjemltiC differentiation trends, low initial Sr ratios, low 180 ratios, moderately enriched LREE, depleted HREE, and no Eu anomalies suggesting derivation by partial melting of basaltic rocks (Blrk, 1979; Blrk et al., 1979, Longstaffe, 1979). Rocks of this suite in the Rainy Lake area have compositions, and N d / S m and ~80 isotopic ratios, indicating derivation from mantle and crustal sources younger than 3 0 Ga (Shirey and Hanson, 1986) Many have N d / Sm ratios that plot near a 2764 Ma "iso- chron", a m in imum age for mantle enrichment accompanying or preceding a major crust-forming event in this part of Superior province Some gneissic intrusions are 2 75- 2 70 Ga, others are 3 1-2 9 Ga (Goldich and Fischer, 1986, Davis et al , 1988 )

Late- to post-kinematic plutons are mostly granodlorlte, granite, and monzodiorlte. Some intrusions are structurally concordant, others distinctly discordant Some have tectonlzed margins and massive interiors, possibly the result of their emplacement as magmatlc diaplrs (Schwerdtner et a l , 1979) They are chemically diverse but their initial Sr and 180 ratios indicate little involvement with older crust (Longstaffe et al., 1982 ) The granitic plutons may have been derived by partial melting of tonalities Monzodlorite intrusions in the Rainy Lake area are chemically similar to mantle-derived, hlgh-Mg andesites (sanu- kites) of Cenozoic island arcs presumably derived by direct melting of mantle material enriched by subductlon of crustal material shortly before the melting event (Shlrey and Hanson,


1984, 1986; Stern et al., 1989). The late plutons are 2701-2682 Ma, placing a limit on the age of major tec tomsm m this part of Superior province


The Wabigoon Subprovince supracrustal rocks form cuspate synformal wedges between and surrounding domal bathohthIc complexes. At greenstone-bathohth contacts, generally zones of high strain, gneissosity and hneation m the plutonic rocks are steep and parallel to structures in the supracrustal rocks Away from these contacts and toward the in- tenor of the bathohths, gneIssosity commonly dips at low angles, forming elhpt~cal structures of various dimensions (Schwerdtner, 1984). Some elliptical structures are true domes with fiat fohation dipping progressively more steeply away from leucocratic, relatively massive cores toward more mafic outer zones. Schwerdtner et al. (1979) considered these to be formed by gravity-driven diapirlsm when ductility contrasts between the plutonic rocks and metavolcamcs were lowered by heating from the intrusions themselves. However, fol- Iation in other elliptical, non-domal structures in lnchned to vertical throughout. Percival et al. ( 1985 ) described the structure of the Sow- den-Wab~kami lakes complex as a series of generally east trending, sinuous antfforms and synforms defined by gneIssoslty dipping 45 ° to vertical. The gneisses are structurally complex with cataclastlc and blastomylonitic zones, rootless recumbent isochnes, refolded folds, and steep, complex lineatmn patterns indica- tive of multiphase deformation. DIapinsm played a role in the structural evolution of Wa- blgoon subprovince, but was only one of a number of tectomc processes operative at various times, levels, and scales.

Several episodes of deformation and regional metamorphism have affected the supracrustal rocks. Poulsen et al. (1980) deduced that folds m part of the wedge-shaped area be-

tween the Quetlco and Seine River faults are downward-facing structures developed on strata that had been previously inverted as a result of early, nappe style deformation. F~- nally there was development of crenulation cleavage, minor folding, shearing, and late transcurrent faulting. The shears, which are related to the regional fault systems, are vertical, have subhonzontal shckenside hneations, and include east trending dextral and northeast- to north-trending sinistral sets. They reflect late tectonic regional shortening about a northwest-southeast subhorlzontal axis Gold-bearing quartz vein systems in the Rainy Lake area and throughout the Wablgoon Subprovince are closely related to these shear zones (Poulsen, 1983).

Major folds in greenstones of the Calm Lake area (Borradalle, 1982) are lsocllnal, steeply plunging structures with axial plane fohatlon and lineatlon. These folds were produced by nor th-south shortening and subvertlcal extension. The folds are warped about gramtoid bathohths and may have resulted from tilting and rotation of early recumbent folds about rising dlapinc intrusions Folds and fohatlons in the supracrustal rocks are concordant with foliation in the plutomc gneisses. The early major structures are overprinted by local cren- ulatmn cleavage and minor folds.

In the southern part of the Beardmore-Ger- aldton greenstone belt, Kehlenbeck (1986) described the dominant (F2) folds as east-west upright buckle-style lsoclines with a penetrative axial plane foliation ($2) that affects bedding (So) and an early bedding plane foliation (SI). These folds are disrupted by shear surfaces parallel to the $2 fohatlons and are con- tamed within fault or shear-bounded panels. There are reversals in the structural facing directions of the F 2 folds, both from one panel to another and along the lengths of individual panels The early bedding plane foliation, reversals in structural facing directions, and small scale refolded folds imply the presence of ear- her folds of regional extent which were re-

130 KD CARD

folded by later F2 folding. The F 2 structures were themselves modified by late, north-striking kinkfolds

The shear zones described by Kehlenbeck ( 1986 ) coincide in part with major east-west, south-dipping faults with dextral strike-slip and reverse dip-slip components of movement that mark abrupt changes in structural facing and trends, and control gold-bearing quartz vein systems (Macdonald, 1983). Complementary northeast-striking shears and faults such as the Marmlon and Minlss River faults are slmstral These conjugate structures reflect northwest- southeast regional shortening

Low-pressure greenschist facies metamorphism in greenstone belt interiors grade out- ward to amphlbolite facies in the margins and m surrounding meta-plutonlc rocks Borra- dalle ( 1982 ) noted that the metamorphic isograds crosscut fold axial surfaces and also greenstone belt-orthogneiss contacts. Meta- morph|sm, therefore, is not related to emplacement of the gneiss but may be related to the syn- to late-kinematic plutons. Isotopic age data indicates that major ductile deformation occurred at about 2710-2700 Ma and was accompanied and outlasted by plutonism and regional metamorphism (Table 1 ) Early deformation may have involved major thrusting as Davis et al (1989) cited evidence for juxtaposition of older sequences over younger m the western Wabigoon Subprovlnce. Increasingly brittle deformation, culminating in transcurrent faulting, persisted until ca. 2685-2680 Ma.

Winnipeg River Subprovince

A middle and late Archean plutonlc terrane

The Winnipeg River Subprovlnce, mainly felsic and intermedmte felsic plutonic rocks with minor supracrustal remnants, is bounded on the north by supracrustal and plutonlc rocks of the Bird River and English River subprovlnces The eastern boundary is placed at the MlnlSS River fault but Winnipeg River has rock

types and ages similar to those of the Wabl- goon dlaplrlC axis of Wabigoon subprovlnce and it is possible that the two terranes were once contiguous

Plutonlc rocks

Winnipeg River Subprovmce consists of over 95% plutonlc rocks, a gnelsslc suite, a sodlc plutonlc suite, and a potasslc suite in general order of decreasing age. Gnelsses which form approximate 25% of the terrane are quartz diorite, tonahte, and granodiorite with inclusions of mafic metavolanics, mafic dykes, and metasedlments and later fohated to massive quartz diorite to granite intrusions (Breaks et a l , 1978, Beakhouse, 1985). The predominant tonahte gneiss represents plutonic rocks derived from partial melting of mafic rocks, the granitic rocks differentiates oftonalltlC magma, and the mafic Inclusions are chemically similar to oceanic basalts (Gower et al , 1983) The gneiss complex represents multiple intrusion into pre-existing greenstones with ongoing deformation and metamorphism and contains rocks with ages ranging from 3170 to 2840 Ma (Krogh et al., 1976, Corfu, 1988)

Sodic plutonic rocks that form approximately 35% of the terrane are fohated to massive, metamorphosed, recrystalhzed diorite to granodiorlte. They form parts of gneiss complexes and more homogeneous syn- to late-kinematic bathohths and plutons Many intrusions have strongly fohated margins and more massive interiors, possibly indicating diaplriC emplacement. They display trondhjemltiC differentiation trends, low total REE, fractlonated REE patterns, HREE depletion, and were probably derived from partial melting of basaltic sources (Beakhouse, 1985) They range from about 2760 Ma to 2700 Ma (Beakhouse et a l , 1988; Corfu, 1988) A granodiorite straddhng the Winnipeg River-Wablgoon boundary is 2709 Ma indicating that these subprovlnces were juxtaposed at or by this time.


Potasslc intrusions that form approximately 40% of the bedrock are mainly massive, unre- crystallized leucogranlte and granodlorlte Granite forms several large, late- to post-kinematic, homogeneous bathohths with calc-alkahc dlfferentmtlon trends. They are geo- chemically evolved with high K, Rb, LREE, Y and initial Sr ratios suggesting derivation by partial melting oftonahte (Beakhouse, 1985 ) Their ages range from about 2705 to 2660 Ma (Beakhouse et a l , 1988 )

Deformatlon and metamorphism

The Winnipeg River Subprovlnce has undergone polyphase deformation and amphlbohte to low pressure granuhte facies regional metamorphism In the Dryden area, where low- grade Wablgoon metavolcanlcs and metasedlments are juxtaposed with medium- to high- grade Winnipeg River gneiss, metamorphic grade increases rapidly but uniformly northward with metamorphic lsograds parallel to the faulted subprovincial boundary (Bartlett, 1978)

Early deformation, expressed by foliation and rootless lsocllnes m the supracrustal remnants and tonalltlC gneiss, is overpnnted by a second phase of folding that coincided with emplacement of early plutons and regional metamorphism The second phase was followed by emplacement of mafic dykes and then by increasingly brittle deformation that culminated in transcurrent faulting (Beakhouse, 1985, Gower and Clifford, 1981 ).

There is isotopic evidence for three tectono- metamorphic events (Corfu, 1988). Meta- morphic zircons In tonahte gneiss are 2790 Ma and may date early plutomsm A second event at 2710-2700 Ma involving deformation, metamorphism, and plutonism may be correlative with similar events in Wablgoon subprovince (Table 1 ). A third event involving granuhte metamorphism and deformation at 2680 is concentrated near the Winnipeg River- English River boundary and may be related to

a major tectono-metamorphtc event to the north

Bird River Subprovince

The Bird River Subprovlnce is a wedge- shaped volcano-plutonlc terrane between the Winnipeg River plutonlc and English River metasedlmentary subprovlnces The Bird River greenstone belt is similar to the greenstone belts of the western Wabigoon Subprov- race, approximately the same age (2745-2740 Ma, Tlmmlns et al., 1985) and has an extensive, chromlte-beanng ultramafic-mafic sill (Scoates, 1983 )

Plutonlc rocks are generally similar to those of the Winnipeg River Subprovmce and include early gnelsslc to fohated sodlc intrusions, one of which is 2779 Ma (Tlmmlns et a l , 1985 ), and late potassic intrusions, including pegmatitlC granite and rare element pegmatltes (Cerny et al , 1981 ). These are peralumlnous, K-rich, slllClC, highly fractlonated rocks with low Ba, Sr, T1, Zr and LREE contents and high ~ 80 values indicating they are S- type granites. Associated complex pegmatltes are enriched in elements such as Ta, L1, and Be (Ayres and Cerny, 1982 )

English River Subprovince

The English River metasedlmentary subprovince is exposed in the area between Lake Winnipeg and Phanerozoic cover of the Moose River basin (Fig. 2 ) The Nemlscau River and Oplnlca River metasedimentary terranes of Quebec (Fig 5) may be the eastward exten- sions of the English River Subprovlnce The English River Subprovlnce is bounded on the north by volcanic and plutonlc rocks of the Uchl Subprovlnce where major dextral transcurrent faults, the Sydney lake and Lake St Joseph structures, juxtapose high-grade Eng- hsh River metasedlments with low-grade greenstones (Stone, 1976; McRltchle and We- ber, 1971 ). This boundary is marked by paired

132 KD CARD

positive (Enghsh River) and negative (Uchl) gravity anomalies indicating that it may represent a major suture zone

Supracrustal rocks

Metasedlmentary rocks, originally turbldltic wackes and slltstones now mainly gneiss and mlgmatlte, form approximately 65% of the bedrock In addition, there are minor amounts of mafic gneiss, probably of both volcamc and intrusive ongln, and lean ironstone (Meyn and Palonen, 1980). The metasedlments have mi- neralogical and chemical compositions indicating a m~xed volcanlc-plutonlc (Breaks et a l , 1978) or dacltlC volcanic (Van de Kamp and Beakhouse, 1979) provenance Progres- sive anatexls has resulted in widespread mlgmatlzat~on.

There are minor amphlbohtes, probably of volcanic and intrusive origin, intercalated with the metasedlments and in the Melchett Lake area a small greenstone belt is capped by ironstone and turbldltiC metased~ments.

Intrusive rocks

Peralumlnous, S-type granite with metase- d~mentary inclusions and minerals such as garnet, cordlerite, sllhmanlte, and tourmaline occurs throughout the migmatltiC complex. Some associated pegmatites have LI, Be, U, and Th minerals (Breaks et al., 1985). A pegmatltlC leucosome m migmatitlc paragnelss is 2681 Ma (Krogh et a l , 1976). There are also early, pre- to synkinematic tonahte and granodlorlte intrusions and late- to post-lonematlc granite- granodiorite plutons. A late pegmatlte is 2652 Ma (Krogh et a l , 1976)


Structural trends, including folds and foha- tIons, are subparallel to subprovlnce boundaries and were formed dunng polyphase deformation and metamorphism (Thurston and

Breaks, 1978). Early deformation, formation of upright isocllnes with axial plane foliation, was accompanied by mlgmatlzatlon A second phase, development of variably plunging Z folds and penetrative foliation, was accom- pained by further mlgmatizatlon. During a third, increasingly brittle phase, there was S- folding, development of cleavage, cataclasis, and faulting.

The English River Subprovlnce, like Que- tlco, has symmetrical patterns of metamorphism with greenschist facies marginal zones increasing to amphIbolite and low-pressure granuhte facies m the interior Maximum metamorphlc temperatures and pressure were 700- 750°C and 4.7-5.4 kb (Chipera and Perkins, 1988)

Uchi, Sachigo, and La Grande River subprovinces

Mtddle and Late Archean volcano-plutonlc terranes tn the north

The Uchl, Sachlgo, and La Grande River subprovlnces are characterized by narrow, sinuous, partly interconnected greenstone belts surrounded and Intruded by voluminous granltold rocks (Figs 2 and 5) Structural trends are predominantly east-west to northwest

Supracrustal rocks The greenstone belts of the Uchl Subprov-

lnce, including the Rice Lake, Red Lake, and Blrch-Uchl belts, consist of lower blmodal basalt-rhyolite cycles and upper calc-alkahc and tholentlc basalt-andes~te-rhyolite sequences Their geochemistry indicates that the basalts are mantle-denved, oceanic tholentes, whereas the LREE-ennched andesltes and strongly fractlonated felslc volcamcs were derived by melting and assimilation of slahc crust by mantle-derived mafic magmas in large, zoned magma chambers (Thurston and Fyer, 1983 ). The volcanlcs range from 2990 and 2732 Ma and generally form two age groups, an older

SUPERIOR PROVINCE OF CANADIAN SHIELD PRODUCT OF ARCHEAN ACCRETION 133

group about 3.0-2.8 Ga and a younger group about 2 75-2 73 Ga (Nunes and Thurston, 1980, Ermanovlcs and Wanless, 1983, Corfu and Wallace, 1986; Corfu and Andrews, 1987, Turek et a l , 1989) The Birch-Uchl and Red Lake belts have tectonlcally juxtaposed sequences of these two age groups.

Metasedlmentary rocks In the Uchi greenstone belts include stromatolltiC marble units intercalated with the older, ca. 3.0 Ga volcanic cycles of the Blrch-Uchl belt (Hofmann et al., 1985 ), volcanogenlc wacke, conglomerate, and ironstone, notably in the upper parts of the sequences, and younger, Tlmiskamlng-type crossbedded quartz arenite and conglomerate of the San Antonio Formation of the Rice Lake belt. The San Antonio Formation is younger than ca 2730-2715 Ma plutonlsm and deformation (Turek et al., 1989) but was affected by later, ca 2700 Ma deformation.

The greenstone belts of the Sachlgo Sub- province are cyclic sequences of tholentic basalt overlain by mixed calc-alkahc felsic and intermediate volcanlcs and sediments (Ayres, 1977; Gilbert, 1985 ). They range in age from over 3000 to about 2720 Ma and form two age groups, one about 3023-2860 Ma, another about 2750-2720 Ma (Corfu and Wood, 1980, Nunes and Wood, 1980; Corfu et a l , 1985; Turek et al., 1986 ).

Several belts, notably North Spirit Lake, North Caribou Lake, Sandy Lake, and Mus- kratdam Lake, have lower sequences of relatively mature, crossbedded quartz arenIte, quartz pebble conglomerate, and stromatohc carbonate (Donaldson and Jackson, 1965; Wood, 1977, Thurston and Chlvers, m press). These shallow-water, platform-type sediments are associated with mafic/ultramafic lavas, subaerlal to subaqueous felslc pyroclastlcs, and ironstone. Most if not all, are ca. 3 0 Ga and may represent passive margin deposits developed on early-formed sialic crust (Thurston and Chivers, in press).

Younger, Timiskaming-type sequences in the Cross Lake, Oxford Lake, and Island Lake

areas consist of crossbedded conglomerate, sandstone, and mudstone intercalated with shoshonltlC mafic and felslc volcanlcs with high LILE contents, unfractionated HREE profles, and no Eu anomalies (Brooks et al., 1983) These shallow-water sequences commonly rest unconformably on older volcanic sequences and are spatially related to major faults. They display rapid facies variations, numerous internal unconformities, and consist largely of locally-derived detritus. They have been compared with late rift deposits of modern evolved island arcs (Brooks et al., lbld) and to deposits of pull-apart basins developed along transcurrent faults (Thurston and Chlvers, in press ) Volcanlcs from the Cross Lake and Oxford Lake sequences are 2706 Ma (D Davis, pers c o m m , 1986)

The greenstone belts of the La Grande River Subprovince have lower basalt-rhyolite cycles and komatiItes overlain by differentiated calc- alkahc and tholentlc volcanics and sediments. Skulskl et al. ( 1988 ) found that the lower thol- elltiC volcanIcs have a MORB geochemistry and were probably formed by fractional crystallization of komatlitlC magmas. Late-stage basalts and andesltes are considered to be the products of crustal contamination of komati- ltlC liquids Sequences of relatively mature quartz pebble conglomerate, quartz arenite, carbonate, ironstone, and greywacke with mafic-ultramafic flows, tufts, and Intrusions are also present (Roscoe and Donaldson, 1988).

Plutontc rocks Plutonlc rocks of the Uchi and Sachlgo sub-

provinces include an early pre- and synklnematlc, deformed, metamorphosed sodlc quartz dionte- tonahte suite, and a later syn- to post- lonematic potasslc granlte-granodlonte-syen- lte suite (Ermanovlcs et al., 1979; HiUary and Ayres, 1980). Many of the early sodlc plutons have ages of 3.0-2 8 Ga, similar to the older volcanic sequences. Others with ages of 2.75- 2.73 Ga are coeval with the younger volcanlcs.

134 K D CARD

The younger granitic plutons are generally post- volcanic and syn- to post-tectonic with respect to Late Archean events, they range In age from 2730 to 2680 Ma (Krogh et a l , 1974, Corfu et a l , 1985, Krogh et al., 1985; Corfu and Wal- lace, 1986; Corfu and Andrews, 1987, Turek et a l , 1987 ) A late monzonlte pluton that is possibly coeval with Tlmlskamlng-type sequences is 2705 Ma (Turek et a l , 1986)

The Berens River Subprovlnce, a plutonic terrane between Uchl and Sachigo subprovinces (Fig. 2), has plutonlc suites similar to those of Uchl-Sachigo (Ermanovics et a l , 1979) ranging from 3000 Ma to 2690 Ma (Krogh et al., 1974, Ermanovlcs and Wanless, 1983, Corfu and Ayres, 1984). The older plutonic rocks were metamorphosed under intermediate pressure-temperature conditions (Ayres, 1978 ) and polydeformed under general north-south compression (Park and Er- manovlcs, 1978 ).

Bienvllle subprovlnce, a plutonlc terrane north of the La Grande River belt has 2800 Ma tonahte-granodlorite gneiss with small greenstone remnants and late granodlorite plutons, one with an age of 2712 Ma (Mortensen and ClesielskI, 1987)

Structure and metamorphtsm Uchl and Sachlgo subprovinces were af-

fected by low pressure regional metamorphism and polyphase deformation involving north- south shortening about 2.73-2.70 Ga ago Early ductile deformation formed upright lsochnes with variable trends, axial plane foliation, and steeply plunging elongation hneatlon This was accompanied by low pressure greenschlst to amphibohte facies metamorphism that displays steep gradients toward granitic plutons (Ayres, 1978; Thurston and Breaks, 1988), occurred before deposition of Tlmiskaming- type sequences, and was coeval with emplacement of 2730-2715 Ma plutons. In the Sa- chigo Subprovlnce, there is a general increase in metamorphic grade toward the Pikwitonel Subprovince (Weber and Scoates, 1978 ) This

regional gradient may be attributable to exposure of progressively deeper crustal levels toward the Plkwitonel and consequently regional metamorphism is related to depth as well as to plutonism.

A second, post-Tlmlskaming phase of deformation represents a brittle-to-ductile transition and resulted in further folding and development of conjugate shears Northwest dextral and northeast Slnlstral deformation zones developed dunng the late deformation have subhorizontal hneatlon, hydrothermal alteration, and, locally, gold-bearing quartz vein systems (Andrews, 1983 ) Corkery and Lenton (1984) described juxtaposition of older and younger volcanic sequences along arcuate deformation zones with transposed foliation Late deformation events were coeval with granite plutonlsm and deposition of Tlmiskammg-type sequences about 2.7 Ga ago

Pikwitonei, Minto, and Ashuanipi subprovinces and the Superior-Trans-Hudson boundary zone

Hzgh-grade and reworked terranes tn the north

In the northwest, the Pikwitonel subprovlnce, an arcuate high-grade gneiss terrane, is bounded on the southeast by the Sachlgo Sub- province and on the west by the Thompson belt, a zone of reworked Archean and Early Proterozolc rocks that separates Archean gneiss of the Superior Province from Early Protero- zoic supracrustal and plutonlc rocks of the Trans-Hudson orogen (Weber and Scoates, 1978; Green et al., 1985, Hoffman, 1988)

The Plkwltonel-Sachlgo boundary is an or- thopyroxene lsograd that obliquely transects structures and rock units of both subprovinces (Weber and Scoates, 1978, Hubregtse, 1980) The Pikwltonel-Thompson belt contact is a narrow transition zone that represents the eastern limit of Proterozolc structural and metamorphic overpnntmg of Pikwitonei gneiss (Bell, 1971) Within this zone, east-trending


Plkw~tonel structures are overprmted by northeast-trending structures of the Thomp- son belt, PlkwItonel granulites are retrogres- sively metamorphosed, and Molson dykes, a swarm of mafic dykes emplaced 1883 Ma ago (Heaman et al, 1988 ) are transposed and metamorphosed The western boundary of the Thompson belt, the Nelson front, is a fault zone with both dip-slip and sinlstral strike-slip movements (Green et al., 1985 ).

The Pikwitonel Subprovlnce has positive magnetic and gravity signatures and the Supe- rlor-Trans-Hudson boundary zone is marked by magnetic and gravity lows, seismic discontinuities, and variations in crustal structure (Green et al, 1985).

In the northeast, southern supracrustal-nch terranes, the La Grande River, Nemlscau River, and Opinaca River subprovlnces are separated from northern and eastern plutomc and high-grade gneiss terranes by faults expressed by discontinuities in the magnetic patterns (Fig. 6) The northern boundary of the Superior Province has commonly been placed at the southern edge of the Proterozoic Cape Smith belt (Stockwell, 1982; Taylor, 1982) However, Hoffman ( 1985 ) has proposed that the Cape Smith belt is allochthonous implying that the KovIk gnelsses lmmedmtely north of the Cape Smith belt are also part of the Supe- rior Province.

Geology The Plkwitonel Subprovlnce consists ofton-

ahtlc gneiss, paragnelss, calc-slhcate gneiss, and mafic, ultramafic, and anorthosltlC bodies, all deformed and metamorphosed to granuhte grade. These rocks are probably the high-grade equivalents of plutonlc and supracrustal rocks exposed in Sachlgo subprovlnce. Gnelsses are 2719-2736 Ma and late pegmatltes 2629-2598 Ma (Krogh et al., 1986a)

Northwest- to west-trending structures of Plkwltonel subprovince were formed by early lsochnal folding accompanied by amphlbohte facies metamorphism followed by emplace-

ment of mafic dykes and further folding, granuhte metamorphism, and mlgmatlzatlon at 630-800°C and 7.9 kb (Mezger et al, 1986). Major metamorphism occurred at 2684-2736 Ma ago but there was also earlier metamorphism, probably connected with plutonism at 2719-2690 Ma, and emplacement of pegmatltes at 2589 Ma (Krogh et al, 1986a)

Thompson belt consists mainly of amphlbollte facies tonallte gneiss, the retrograded equivalents of Pikwltonei granuhtes Gnelsses of the eastern and central parts of the belt are 2770 Ma whereas those in the west are 3086- 2926 Ma (Machado et al., 1987) The Ar- chean rocks are cut by Proterozoic granites and ultramafic intrusions and are overlain by deformed, metamorphosed Early Proterozolc sediments and mafic-ultramafic volcanlcs

The Ashuanlpl complex in the east consists of granuhte facies mIgmatitlc paragnelss and rare mafic gneiss with sheets of tonahte gneiss and fohated to massive tonahte, diatexite, granite, and syenite (Eade, 1966; Percival and Girard, 1988). A tonahte pluton is 2690 Ma and metamorphic zircons from diatexlte range from 2688 to 2620 Ma (Mortensen and Perci- val, 1982 ). These ages indicate that Ashuanlpl complex is the high-grade equivalent of the Oplnaca River and Nemlscau River metasedimentary subprovinces.

Mlnto subprovInce consists of orthopyrox- ene-bearlng plutonic rocks of charnockxtic affinity, diorite, granodlorlte, diatexlte, and granite with inclusions of granuhte facies metasediments and metavolcanics (Stevenson, 1968). A late granodlorite in the east is 2721 Ma (Machado et al., 1989) Dominant northerly structures are overprinted by east-west structures, possibly faults, revealed by the magnetic patterns (F~g 7 ). The Kovlk terrane north of Cape Smith belt has Archean gnelsses with deformed Proterozolc supracrustal remnants. The gneisses have Rb-Sr ages of 2900- 2600 Ma (Doig, 1987)

The northerly structural trends and ortho- pyroxene-beanng plutonIc rocks of Minto sub-

136 K D CARD

province indicate that this terrane is distinct from other parts of Superior province and may represent a relatively late addit ion to the craton The mixed Archean-Proterozolc terrane north of Cape Smith belt may be analogous to the Thompson belt of the northwestern Supe- rior Province.

Summary of the geology and tectonic evolution

The Superior Province consists of approximately 75% gnelsslc and plutonic rocks and 25% low- to medium-grade supracrustal rocks that form terranes with distinctive hthological, tectono-metamorphic, age, and geophysical characteristics. Gneiss terranes are concentrated in the north and southwest whereas the central part of the craton consists of low-grade granlte-greenstone and metased |mentary subprovinces (Fig. 1 ). The Superior Province IS a remnant of a larger Archean continent, assem- bled in the Late Archean, fragmented in the Early Proterozoic, and modified by colhsional deformation during Proterozoic events. With the exception of the Early Archean Minnesota River Valley terrane, the rocks were formed during the Middle and Late Archean Southern terranes such as the Abltibl Subprovlnce con- SlSt mainly of Late Archean juvenile crust of Island arc origin. Terranes in the north, for example Uchi and Sachigo, preserve multiple generations of arcs and other elements ranging in age from 3.0 to 2.7 Ga.

Htgh-grade gnetss

High-grade gneiss subprovinces consist of upper amphlbohte and granuhte facies ortho- and paragnelss with anorthosltlC and char- nockltiC intrusions. Gneisslc foliation, domal structures, and high-strain zones, the products of polyphase ductde deformation, are typical. There are some differences among the various high-grade terranes. The Minnesota River Val- ley has 3.6 Ga rocks and may represent an Early Archean foreland onto which the younger arc

terranes were accreted along a suture represented by the Grea t 'Lakes Tectonic Zone Minto subprovince has northerly-trending structures and may also be a distinctive terrane juxtaposed late m the tectonic history The remaining high-grade subprovmces are equivalents of low-grade, supracrustal-rlch terranes and represent exposures of the lower levels of a layered crust, not fundamentally different types of crust

Plutontc rocks

Plutonlc rocks of the granlte-greenstone and plutonlc subprovinces include early pre- to synklnematlc, follated, sodlc plutonlc suites and later, syn- to post-kinematic, generally massive potasslc suites.

The sodlc plutonlc rocks have mafic enclaves of metavolcanic and Intrusive origin, display trondhjemltlC differentiation trends, l imited compositional ranges, low initial strontium and oxygen ratios, fractlonated REE patterns with LREE ennchment and HREE depletion, and no or slightly negative Eu anomalies They were probably formed by partial melting of enriched mantle or juvenile mafic crustal rocks Many have ages similar to those of associated volcanic rocks and to mafic intrusions

The calc-alkallC potasslc intrusions have high K, Rb, and Y contents, low strontium and oxygen isotopic ratios, low total REE, ennched LREE, depleted HREE, negative Eu anomalies, and variable Rb isotopic compositions They were probably derived by partial melting oftonall te or siliceous granuhte Many are coeval with major tectonlsm and in several greenstone-granite subprovinces there is evidence for a l 0 to 20 million year hiatus between cessation of the volcanism and onset of the late potasslc plutonism.

Highly fractlonated potassic granites, for example those of the Bird River Subprovince, and some syenitic intrusions may be A-type, analogous to post-colhsional granites of Phanero-


zoic orogens such as the Alaskan Cordillera (Sylvester, 1989) Other syenite-diorite plutons have high Mg, N1, Cr, and LILE contents similar to "sanukltold" volcanics of Cenozoic island arcs

Peraluminous, S-type gramtes prevalent in the metasedlmentary subprovlnces are highly fractionated, have low LREE contents and high oxygen isotopic ratios, and were derived by an- atex~s of alumlnous sedimentary rocks.

Fohated plutonlc rocks and supracrustal remnants of the plutonlc and granite-greenstone subprovlnces were metamorphosed under amphibohte facies conditions They display domal structures, the result of multiple deformation including early ductive folding, dIapinsm, and late brittle deformation Some plutomc subprovlnces have positive gravity signatures, suggesting that dense lower crust may lie at shallow depths This, coupled with the evidence for somewhat higher metamorphic pressures suggests that they represent somewhat deeper-level equivalents of the granite-greenstone terranes

Several subprovxnces, notably the Wabi- goon, Uchl, and Sachlgo, have older ca 3 0 Ga granitold domains Some (eg Marmlon bathohth of Wabigoon subprovince) constitute basement to ca 3 0-2.8 Ga supracrustal sequences and may have had similar relationships to the younger, ca. 2 7 Ga greenstones. However, contacts between the older plutonlc and younger supracrustal rocks are mainly tectonic This, taken together with the general lack of isotopic or geochemical inheritance in the younger igneous rocks, suggests that their juxtaposition was essentially tectonic. Some of the older plutonlc units, for example those of the Wablgoon dmplriC axis and Winnipeg River subprovlnce, may represent remnant microcontlnents

Supracrustal rocks

The volcanic-sedimentary sequences of the greenstone belts range in age from about 3.0 to

2 7 Ga Supracrustal rocks in the south are mainly younger than 2 8 Ga whereas in the north, older, 3.0-2.8 Ga sequences are more common Five mare facies associations are present ( l ) platform-type quartz arenlte- stromatohtlc carbonate sequences, (2) mafic- ultramafic submanne lava plain sequences, (3) mixed mafic-felslc submanne to subaerial central volcamc sequences; (4) turbldltiC clastic sequences, and, (5) Tlmlskaming-type shoshonitic volcanic-alluvial/fluvial sedimentary sequences.

Crossbedded quartz arenlte and quartz pebble conglomerate, commonly with stromatohtic carbonate, komatnte, ironstone, and subaerial pyroclastlcs, are present in the Wablgoon, Uchl, Sachlgo, and La Grande River subprovlnces These relatively mature, shallow-water sediments have a sialic provenance and were probably deposited under relatively stable conditions m continental platform or rafted margm environments Most, if not all, are older than 2 8 Ga

Mafic-ultramafic submarine lava plain sequences consisting of pillowed and massive tholeutic flows with komatntes, mafic/ultramafic sills, sulphide facies ironstone, chert, and argflhte, form the lower, areally extensive parts of greenstone belts. Most are 2 75-2 70 Ga They are chemically similar to oceanic volcanics (MORB, immature arc, oceanic island) and are comparable to oceanic submarine lava plain and Hawaiian-type shield volcanic accumulations

Mafic-felsic volcanic sequences that form the more areally restricted central complexes are chemically diverse, including both calc-alkahc and tholentlc compositions Many are bi- modal mafic-felslc sequences whereas others are more fully fractlonated comprising andes- ltlC and dacitic compositions as well These sequences commonly shallow upward, with lower subaqueous basalt and andesite overlain by shallow-water to subaerial dacltiC and rhyoh- tic pyroclastlcs, Ironstone, and epiclastic sediments They are probably the products of arc

138 K D CARD

volcanism, both evolving island and continental arcs Most are 2.75-2.70 Ga but ca 2.8 Ga arc volcanics and associated plutons are present in the Uchl and Sachigo subprovinces

Turbidxtic clastic sediments, mainly greywacke and siltstone with minor conglomerate, form thick units m the greenstone belts, typically within and as aprons about the upper mixed volcanic sequences Turbldites also form the extensive, variably metamorphosed sequences of the metasedlmentary subprovinces These texturally Immature rocks, composed largely of felsic volcanic detritus, were derived mainly from 2 75 to 2.70 Ga complexes and hence were deposited after, or during and after, major volcanism in the nelgh- bouring granlte-greenstone subprovlnces

The Tlmlskaming-type accumulations consist of Immature fluvial/alluvial sediments, typically crossbedded arenite and conglomerate with some shale and ironstone, and calc- alkahc to alkahc, shoshonltlC subaerial volcanics These sequences display rapid faoes variations and internal unconformities, consist largely of locally-derived debris, and unconformably overlie volcanics and subvolcanic plutons. Most are affected only by late deformatlonal and metamorphic events Many Timiskammg-type sequences are associated with subprovince boundary faults and may have been deposited in pull-apart basins developed by late transcurrent movements on these structures Others may be comparable to late shoshonltic volcanic-clastlc sediment rift sequences of modern evolved island arcs. In the northern Superior Prownce, deposl tmn of Tlmiskaming-type sequences occurred about 2 71-2 70 Ga and in the south, about 2.69-2.68 Ga


The dominant east-west structural trends (Fig. 9 ) and metamorphic zonation (Fig 8 ) of the Superior Province are the products of several orogenic events Evidence for ca 3 0 -

2 8 Ga events is sparse and consists of scattered isotopic ages of metamorphic rocks and minerals, unconformities between 3 0-2 8 Ga supracrustal and plutonlc rocks, and hints of old structural elements The effects of these events have been largely destroyed by late, polyphase deformation, metamorphism, and plutonism during the ca 2 7 Ga Kenoran orogeny There is evidence that these late, Kenoran events are generally younger in the south than in the north The absolute ages of the youngest deformed, metamorphosed rocks, principally metavolcanlcs, and the oldest, unmetamor- phosed, post-tectonic intrusions in the Sachlgo and Uchl subprovlnces indicate that ductile deformation began at about 2 73 Ga and later, increasingly brittle deformation persisted until ca 2 70 Ga In the Wawa, Abltlbl, and Pontiac subprovlnces, deformation began at about 2 70 Ga and continued until ca 2 68 Ga

Several greenstone belts, for example the Vermilion belt, contain evidence of pre-cleavage deformation. Major downward-facing structures, possibly nappes, are present in the Rainy Lake and MlchIplcoten belts The Abl- tlbl belt has major antlformal domes and synformal basins that were apparently established at an early stage and were subsequently modified by polyphase deformation involving folding, thrusting, and transcurrent faulting

During Late Archean orogenesls, early ductile deformation involving major nor th-south shortening and subvertical extension attributable to nor th-south subhorizontal compression was accompamed by low- to intermediate-pressure metamorphism Late, increasingly brittle deformation with folding and formation of conjugate shears and major northwest dextral and northeast sinlstral transcurrent faults also involved nor th-south shortening by oblique compression or transpresslon

In the volcano-plutonlc subprovlnces, syn- chnorial and antlchnorial greenstone belts bi- furcate and wrap around domal bathohthlc complexes Although there was appreciable diapirism in connection with emplacement of

S U P E R I O R PROVINCE OF CANADIAN SHIELD P R O D U C T OF ARCHEAN ACCRETION 139

LEGEND

~ ~, u~. Fault displacement undefined transcurrent, thrust, normal

"~ ~, Fold antlchne or antfforrn synchne or synform

/ ' + Foliation inchned subhorlzontal trends based on magnetics ~n part

__7 - - v >Z---

"-'-'-" - "k; ;- "-

/ - /

- - / I - ; " .-" . - ~ . "

>::-. ";,

---,, '-> I=-2-

Y

300 km • !

Fig 9 Major faults and general structural trends FL=Favourable Lake fault, GFTZ=Grenvtlle Front Tectonic Zone, GL=Gwllltm Lake fault, IL= Ivanhoe Lake fault, K= Kenyon fault, KLC= Karkland Lake-Cadillac fault, L= Lepage fault, LGR = La Grande River fault, LSJ= Lake St Joseph fault, MR = Mmtss River fault, NF= Nelson Front, O= Onapmg fault, PD=Porcupme-Destor fault, Q=Quetlco fault, SL=Sydney Lake fault, SR=Seme River fault, T=Tlmlskammg fault, WR = Wmxsk R~ver fault

the bathohths, many of the domal and elhptl- cal structures are the product o f polyphase de- formatxon Some structures m the plutonlc gneiss complexes, for example the Wawa gnexss domain, are possibly the result o f ductile ten- sxonal flow

Quet~co metase&menta ry subprovmce has early recumbent folds overpr inted by major eas t -west subhonzonta l xsochnes with van- able facing dlrectmns that are m turn overpnnted by late, doubly-plunging folds and east-

west transcurrent faults. The Pontiac Subprov- race has south-verging structures that probably constitute a series of thrust imbrications and recumbent folds cored by granmc intrusions

Regional metamorphism ranging from subgreenschlst to granuhte facies accompanied and outlasted the deformatlonal events and generally coincided with major plutonlsm. Metamorphic grades m the volcano-plutonlc subprovlnces generally range from subgreensch~st to low amph~bohte fac~es In the

140 K D CARD

,,w + + ~ + =.o, oo + = . . . . . + o o , . + ~ KM 0

~ - . . . . . - . . . . . - ~ 7 , , >_ - f ~ ~ ~ . . . . ~ . . ¢ , . . c Z ~ - - - -

SSE 0 KM

-10

20

3O

4O

NW KM 0

10-

20

30-

40-

-i + . . . . + ~ + Ab,t,b, + ~ S E N ° + Ab,t,b, + , . . . . . . ~ ' ~ S

LEGEND Proterozolc rocks

A r c h e a n [ ~ Granuhte gneiss

I + I Felsic plutons I, 1 Metased . . . . tary belt

Tonahte gneiss I I Greenstone belt

Fig 10 Cross-sectlonsofthe Superior ProvmceArchean crust

metasedlmentary subprovlnces, metamorphic grades increase inward from low greenschist in marginal zones to amphlbohte, and locally, low-pressure granuhte facies m the interiors Plutonic complexes in the central parts of the belts are possible sources of heat for this high- temperature, low-pressure metamorphism

C r u s t a l s t r u c t u r e

The Archean crust of the Superior province, as interpreted from seismic studies, modelling of gravity and magnetic data, and observation of suspected crustal cross-sections, is grossly layered (Fig. 10) An upper layer approximately 10 km thick with no or few seismic reflectors, possibly a consequence of steeply-dipping structures, has greenschist to amphlbohte facies supracrustal sequences and plutons that extend, on average, to depths of about 5 km with local keels to 10 km. Below this IS a 10- 20 km thick intermediate layer consisting of

gnelsslc, generally tonahtlc plutonlc rocks with supracrustal remnants, all metamorphosed to amphlbohte grade, and more massive intrusions A lower layer of granuhte facies gneiss of plutonlc and supracrustal origin extends to the base of the crust at an average depth of 40 km. The middle and lower layers have numerous seismic reflectors probably attributable to subhonzontal , heterogeneous layering and to thrusts Much of the hthologlcal and structural variation evident in Superior province is probably the result of differential uplift and exposure of different levels of this layered crust. Geobarometnc calibration of metamorphic mineral assemblages Indicates that the greenstone belts were metamorphosed at pressures of ca 3-4 kb or depths of less than l0 km whereas the high-grade metamorphism of the metasedlmentary belts occurred at pressures of 4-6 kb, and the high-pressure granuhtes of the Kapuskaslng and Plkwltonel terranes represent metamorphism at depths of 20-30 km.


Tectomc htstory

The Superior craton was formed in the Ar- chean by the assembly of diverse elements, some of which were generated primarily in the Late Archean, others of which have significant Middle Archean components, and, m the case of the Minnesota River Valley, Early Archean rocks and tectomc events. Most subprovinces are complexes that represent collages of smaller, previously-formed terranes. The existence of ca 2.8 Ga quartz arenite-carbonate

platform sequences suggests that some of the early-formed terranes were relatively stable and p o s s i b l y e x t e n s i v e .

Renewed magmatic activity in the Late Ar- chean resulted m volcamsm, plutonlsm, and sedimentation throughout the Superior Prov- ince. In the northern Superior Province volcanism ended about 2 73-2.72 Ga ago with the onset of major polyphase deformation, regional metamorphism, and plutonlsm Early d u c t l v e d e f o r m a t i o n u n d e r c o n d i t i o n s o f

north-south compression and low-pressure

85 °

\ x~/\

/~ Mafm dyke

• Alkalic rock-carbonat i te complex

\\ \~ xx\

• \

/ \ \ \ ',> >~.W"-

\V

/ / \ ,

,f ~ ~\\ /\ Ii

-x

eo'

\

/ / /

(- >

3 0 0 KM I I

9,~o ~ 70 °

a.5 ° ao" T s"

F~g 11 Proterozoac marie dyke swarms, alkahc rock-carbonaUte complexes, and tectomc elements 1 = Matchewan dykes, 2 = Molson dykes, 3 = Prelssac dykes, 5 = A b m b l dykes, 6 = Keweenawan dykes, 7= Grenvdle dykes

142 K D CARD

W l WR ER US AW I Q W

E / ' S G a 2 71 Go

WR ER US

M R V P AW Q W WR ER US

® 0 ® O @ 0 @ 0 + + + + + / , - - /1~ . ..~ ~,1 " " - - x ~ / ~ ÷ + . - - • i / _ - t ~ - + + + + + + . . . . . . . - ' k z ~ l , ~ ... , I ~ - . i x + ~ I / \ l \ - I -_ .

2 7 0 - 2 6 8 Go

Fig 12 Cross-sections depicting Lake Archean tectonic evolution of the Superior Province revolving southward obhque accretion of island arcs, accretlonary prisms, m]crocontments, etc A W= Ablnbi-Wawa island arc terrane, E R = English River accrenonary prims, M R V= Minnesota River Valley foreland, P= Pontiac accretionary prism, Q--Quetlco accretionary prism, US=Ulchl-Sachlgo ~sland arc terranes, W=Wablgoon island arc and m~crocontlnent terranes, WR = Wmmpeg River mIcrocontlnent

metamorphism was succeeded by increasingly brittle deformat |on in a dextral transpresslve regime that culminated m transcurrent fault- rag, shearing and low-grade metamorphism Deposition of late alluvial-fluvml sedimentary and shoshomtic volcamc sequences at approximately 2 71 Ga during this late brittle deformation was followed by emplacement of post-kinematic gramtic and syeninc Intrusions about 2 70-2 67 Ga ago

In the southern Superior Province, major volcanism ended about 2 71-2 70 Ga ago with onset of polyphase deformation, again under general nor th-south major compression, with accompanying plutonlsm and low-pressure regional metamorphism Deposition of the thick turbidlte sequences of the metasedlmentary belts also occurred at about this time. Later, increasingly brittle deformation attributed to nor th-south dextral transpresslon was coeval with deposition of alluvml-fluvial sedimentary and shoshonltlC to alkahc volcanic sequences, notably the Tlm~skaming Group, about 2 70-2 68 Ga ago, and followed by emplacement of post-kinematic granitic, syemtic, and pegmatltlC intrusions 2 68-2 65 Ga ago

The last major orogenic events to affect the Superior province, the Kenoran orogeny

(Stockwell, 1982), occurred some 20 mllhon years earlier in the north than in the south The main terminal orogenic events, probably correlative with docking of the various terranes, occurred at about 2 72 Ga in the Sachlgo and Uchl subprovinces, about 2.71 Ga in the Wa- blgoon and Quetlco subprovlnces, and about 2 70 Ga in the Abitlbl, Wawa, and Pontiac subprovlnces (Fig 12) Furthermore, although uplift and cratonizatlon of most of the Superior Province occurred prior to emplacement of Early Proterozolc mafic dykes of the Matachewan Swarm, granuhte faoes metamorphism in high-grade gneiss terranes such as Kapuskaslng and Plkwltonel was followed by magmatlsm and slow cooling at great depth with the result that zircons from these high- grade rocks yield U - P b isotopic ages as young as 2 6 Ga. Uplift and erosion of some high- grade terranes may have occurred in the Early Proterozoic, possibly in connection with colh- slonal orogenic events about the margins of Superior craton

Superior Province is apparently underlain by a thick, metasomatlzed, hthospheric root. Late Archean and ProterozoIc magmatic rocks unit of probable mantle origin within and about Superior Province, including Huroman basalts


(Jolly, 1987), mafic dykes (Condie et al , 1988), and alkahc rock-carbonatl te complexes (Bell et al., 1986), show evidence in their trace element and isotopic composit ions of derivation from variably depleted and enriched mantle sources The isotopic data indicates that mantle metasomat~sm occured at least 2 7 Ga ago and hence is probably connected with large-scale melt extraction and crustal recycling during formation of the Su- perior crust (Shlrey and Carlson, 1986).

Tectonic models

Various tectonic models that have been proposed for the Superior Province can be viewed as either "fiXlSt" or "moblhs t" depending on whether the rocks units are considered to have been brought together principally by vertical or horizontal mechanisms of assembly (Black- burn, 1980). Most fixist models assume a preexisting smhc crust with formation of supracrustal sequences i n r i f t s or linear down- warps initiated in the crust by mantle processes Cont inued downwarplng (sagductlon) and partial melting followed by plutonlsm, dlapirlsm, deformation, metamorphism, thickening, and uplift, all the products of vertical, gravity-driven tectomcs, resulted in for- matron of an Archean craton rich in plutonlc rocks and greenstones. Examples of fix1st models include those of Goodwln (1977), Young (1978), and Ayres and Thurston (1985) In contrast, mobllist models assume mobile, mainly oceamc crust within a plate tectomc framework involving subducUon and horizontal accretion (Talbot, 1973), mainly in convergent plate boundary settings. Examples of mobfllSt models include those of Goodwm and Rldler (1970), Langford and Morin (1976), Dimroth et al ( 1983a, b), Ludden et al (1986), Sylvester et al (1987), and Pero- val and Williams ( 1989 )

In the author's opinion, any model proposed must satisfy the following

(1) Field and isotopic evidence indicates

that most Superior Province supracrustal sequences were not deposited on older slahc crust nor were slahc rocks older than 3 1 Ga involved m a significant way in their evolution The ca 2.8 Ga quartz arenlte-carbonate platform sequences in the north are an exception but do not lnvahdate the generalization

(2 )Super io r province rocks represent newly-formed crust, derived from mantle or recycled juvenile crustal sources dunng Mid- dle and Late Archean magmatic events that represent major episodes of crust-mantle separation preceeded or accompanied by large- scale mantle enrichment, probably the result of rapid recycling of oceanic crust

(3) The supracrustal sequences, m terms of their stratigraphy, rock associations, and geochemistry are most closely comparable to volcamc and sedimentary sequences of modern, Pacific-type marginal orogens They do not resemble rifted margin or continental rift sequences They do resemble oceanic, island arc, and continental arc accumulations

(4) Plutomc rocks of Superior province bear many similarities to those of younger orogens. Granuhte gnelsses of the high-grade terranes and tonallte gnelsses of the volcano-plutonlc subprovlnces have their counterparts in younger magmatlc terranes such as the Coast plutonlc complex of the Cordillera Superior Province trondhjemltlC synvolcanlc plutons, younger syntectonlc calc-alkahne bathohths, and still younger, post-tectonic granitic to syemtic plutons are matched by similar suites in many Phanerozoic orogens (Woodsworth et a l , 1983, Roddlck and Hutchlson, 1972 )

( 5 ) There is evidence for early thin-skinned deformation with formation of thrusts and nappes, followed by thick-skinned deformation with rotation of early-formed structures and formation of new upright structures, culminating in transcurrent faulting Similar evolutionary patterns are present in younger orogens Furthermore, the belt-like architecture of Superior province IS reminiscent of Phane- rozoic orogens The southern Wab~goon and

144 K D CARD

adjacent parts of Quetlco subprovlnces are similar to Cordilleran fold and thrust belts with the interior of Quetico subprovlnce represent- ing an internal metamorphlc -p lu tomc zone Southern Abitlbi and Pontiac subprovlnces may constitute a similar example

(6) Superior province crust is about 40 km thick, is layered, and displays variations in metamorphic, structural, and hthologlc char- acterlstics that correspond in part to different levels of exposure of this layered crust

(7) The construction and evolutxon of the alternating, linear volcano-plutonic and metasedimentary belts, and their southward young- lng, is consistent with lateral accretion of complex, long-lived volcanic arcs, oceanic islands and plateaux, microcontments , and accretionary prisms in a regime with an oblique dextral component of plate convergence

A tectomc model for Superior Provmce

A model that best accounts for the foregoing features of the Superior Province involves subductlon-drlven accretion of Archean crustal elements, most of which range in age from 3.1 to 2 6 Ga Some terranes, for example Uchl, Sachlgo, and Wabigoon, are complexes consisting of Middle and Late Archean rocks juxtaposed by early accretlonary processes that resulted in formation of relatively stable cra- tonic elements some 3 0-2 8 Ga ago when mature platform-type sequences were deposited

During Late Archean orogenesls, northward-directed subduction led to successive ac- cretlon of alternating volcano-plutonIc and metasedlmentary terranes (Fig 12) Uchi and Sachlgo subprovinces were amalgamated about 2 72 Ga ago. The Winnipeg River and Wabi- goon subprovlnces, along with the newly- formed English River accretionary sedimentary complex, were accreted to the Uchl-Sa- chlgo terrane approximately 2.71 Ga ago along a suture that generally corresponds to the Eng- lish Rlver-Uchx boundary Northward subductlon at a low angle resulted in renewed

magmatism throughout the northern Superior Province, including formation of the Berens River plutonlc arc Late tectomsm culminated with transcurrent faulting and deposition of Tlmlskamlng-type sequences

Accretion of mainly Late Archean volcano- plutonlc complexes of Wawa and Abitlbl subprovinces and accreUonary sedimentary complexes of Quetico and Pontiac subprovlnces occurred about 2 7 Ga ago Again, shallow northward subduction resulted in magmatism and tectomsm culminating in transcurrent faulting and deposition of the Tlmlskamlng Group and similar sequences. The Minnesota River Valley may also have been juxtaposed at this t ime Post-tectonic plutonlsm and ele- vated temperatures persisted for another 10- 20 milhon years in the volcano-plutonlc belts and for 30-50 million years m the high-grade terranes

Posstble settzngs and modern analogs

Modern analogs of the Superior Province may exist in the convergent-plate boundaries of the western Pacific, for example those of the Indonesian, Philippine and Japanese regions described by Hamilton ( 1979, 1988 ), Karlg et al. (1986), and Talra et al (1985). In the northwest Pacific, on-going accretion results from subductxon of the Philippine Sea and Pa- cific plates beneath the margins of Eurasia These plates, which are being consumed at subductlon zones such as the Ryuku and Mar- lanas trenches, carry a variety of active and remnant volcanic arcs, trench and basin sedimentary accumulations, seamounts, oceanic plateau, and submerged mlcrocontlnents Col- hslon between elements such as the Mananas ridge and Japan arc cause uplift, erosion, and sedimentation of volcanlclastlc turbldites into adjacent trenches and basins (Maynard et al., 1982 ) With continuing subductlon, relatively buoyant elements such as the sedimentary accumulations, island arcs, seamounts, and submarine plateaux will not subduct but rather are


accreted (Talbot, 1973; Hamilton, 1988). By analogy, the lower tholent~c-komatntlC submanne accumulations of the Superior Prov- ince greenstone successions would represent a submanne lava plato, Hawanan-type strata- volcanoes, or volcamc plateaux. Recent stud- les (Holcomb et al., 1988) have revealed the presence of extensive Cenozoic submarine basalt flows w~th similarities to the lower, mafic sequences of many Archean greenstone belts. The calc-alkahc central volcamc complexes would be the upper parts of mature ~sland arcs and continental arcs; blmodal states may be the products of volcanism on stretched continental crust in back-arc basins Turbl&t~c sediments may represent trench fill, inter-arc basra, accretmnary prism, or deep-sea fan deposits. Some late fluvml-alluvml se&mentary and shoshonlt~c-alkallc volcamc sequences may represent late rift-phase sedimentation and volcanism m mature island arcs. Other T~mls- kamlng-type sequences are probably pull-apart basin deposits developed dunng late transpress~on. The synvolcamc plutons are comparable to those of the roots of modem arc systems The later plutomc states represent syntectomc magmat~c arcs and post-tectonic gramt~c to syenlt~C magmat~sm.

In Cenozoic orogens deformation occurs in two mare stages, an early, thm-slonned, low- temperature stage revolving major thrusting, recumbent folffmg, wrench faulting, and shear- mg associated with detachment and incorpo- ration of the accret~onary complexes, and a later th~ck-slonned, h~gh-temperature stage assocmted with emplacement of younger plutomc rocks. In the Superior Province much of the deformaUon and metamorphism is of the second, h~gh-temperature stage, but vestiges of early, low-temperature thrusting and recumbent folding are preserved in many areas.

In the northwest Pacific regmn, accretmn has produced elements that resemble Archean terranes in terms ofhthologic and structural com- plexity The Philippine Islands, for example, are described by Hamilton (1979) and Karig

et al. (1986) as a jumble of subduct~on complexes, magmatlc rocks, and volcanlclasUc se&ments of several different arc systems. These rocks, along with back-arc basin and continental margan volcano-sedimentary sequences, were brought together through a complex sequence of convergence, rifting, stnke- shp faulting, lsocllnal folding and plutomsm The Japanese Islands are also an excellent example of an accretlonary complex with a history of subductmn, colhslon, faulting, volcamsm, se&mentat~on and plutomsm extending from Paleozo~c to Recent Ume (Yosh~da, 1975, Talra et a l , 1983).

There are many &fferences between the Su- perior Province and possible Phanerozolc an- flogs such as Japan. The Superior Province has a high proportion of plutomc rocks, notably of tonahte referred to be the product of partial melting of subducted oceamc crust. Koma- tntes, formed from magmas approaching mantle composmon, are abundant m Superior Province, rare m Phanerozo~c volcamc terranes. The proportions of daclte, rhyohte, and pillow basalt forming blmodal sequences are higher, and andesltes lower, in Superior greenstone sequences, especmlly in comparison to modem oceamc ~sland sequences. Steeply &p- ping structures are prevalent m the upper crustal levels represented by Superior Province greenstone and metase&mentary belts, many Phanerozo~c orogens are characterized by thrusts and nappes Bluesch~st facies metamorphism, characteristic of paired metamorphic belts m some Phanerozo~c orogens, is absent in Superior Province.

Some of the foregoing differences, for example the h~gher proportmn of plutomc rocks, may be attributable m part to exposure of deeper average crustal levels m Superior Prov- ince. The dominance of steep structures and paucity of thrusts and nappes in Superior Province may be more apparent than real. Early thrusts and recumbent folds, spora&c- ally preserved m some belts, may have been largely obhterated by late dmpmsm and

146 K D CARD

transpresslon Recent selsmlc work suggests that flat structures may be much more abundant and important than previously recognized

Models of global thermal evolution and the presence of komatntes indicate that the mantle was significantly hotter during the Archean than at present Archean heat flow was consequently greater, and most of this heat was lost through production of new oceanic crust (Blc- kle, 1978; Abbott and Hoffman, 1984) In- creased product ion of oceanic crust implies in- creased subduction and rapid recycling of young crust which would produce blmodal basalt-daclte suites and abundant tonahtes (Ab- bott and Hoffman, 1984), rock types characteristic of the Superior Province. Subduction of young oceanic crust increases the probabil- ity of spreading ridge subductlon which would also promote blmodal volcanism and tonahtIc plutonlsm (Abbott and Hoffman, 1986). Sub- duction of a spreading ridge, or any buoyant element, beneath an active arc would result in uplift of the arc, cessation of volcanism, and low-grade metamorphism and calc-alkahc intrusive activity. Uplift of the arc would also result in erosion, the products of which could be deposited locally as subaerial clastic sediments or distally as turbldltes In Superior Province, spreading ridge subductlon could account for the pattern of cessation of volcanism followed by deformation, plutonlsm, low-grade metamorphism, and uplift of the volcano-plutonic terranes and deposition of turblditltiC sediments in adjacent metasedimentary subprovlnces.

A hotter Archean mantle would result in a thicker oceanic crust with density stratifica- tion and zones of lntercrustal melting and magma formation (Blckle, 1986). Such a crust would be buoyant, would resist subductlon, but when subducted would do so at a low angle (Sleep and Windley, 1982 ). This would result In broad zones of igneous activity and metamorphism w~th product ion of abundant tonahtic magma emplaced as horizontal sheets

with the crust, features characteristic of the Superior Province

A thick, density-stratified oceanic htho- sphere would tend to delamlnate dunng subductlon (Hoffman and Ranalh, 1988) This would facilitate removal of the upper, more buoyant parts thus promoting "skimming tectonics" (Talbot, 1973), and leaving a denser, more easily subducted lower slab Colhslon of oceanic and continental plates leading to de- lamination and tectonic interleaving of the upper parts of the oceanic crust with the deeper parts of the continental crust provides a mech- anism for transporting supracrustal rocks to deep levels thus accounting for their presence in high-grade terranes (Sleep and Wlndley, 1982).

The model presented here is, taking Into account factors such as higher Archean heat flow, in general accord with the geological character- IStiCS of the Superior Province Further tests of this model might involve investigations of the question of Inheritance of older isotopic or detrital components The model also predicts that horizontal tectonlsm was more important than has heretofor been recognized. If so, thrusts, nappes, and superposltlOn of older over younger sequences should be common Reflec- tion seismic experiments and integrated structural-geochronological studies have potential for investigating these problems

Acknowledgements

This synthesis is a synopsis of work done toward compiling the geology of Superior province for the geological and tectonic maps of North American and the Canadian Shield Vol- ume of the Decade of North American Geol- ogy. Sandra Barnes, as research assistant, con- trlbuted much to this synthesis. Critical reviews by Paul Hoffman, John Percival, Jon Scoates, and Phi1 Thurston significantly improved the manuscript. Nancy Devine patiently and ex- pertly typed numerous versions. Tim West drafted some of the figures. Geophysical maps


were supphed by the Geophysical Data Centre, Geologtcal Survey of Canada. Geological Sur- vey of Canada Contrlbutmn 42388.

References

Abbott, D H and Hoffman, S E, 1984 Archaean plate tectonics revlsted 1 Heat flow, spreading rate, and the age of subductmg oceanic lithosphere and their effects on the ongm and evolution of continents Tectonics, 3 429-448

Abbott, D J and Hoffman, S E, 1986 Hot spot abundance, ridge subducUon and the evolution of greenstone belts In Abstr Workshop on Tectonic Evolu- tion of Greenstone Belts, LPI Tech Rep 86-10, pp 46-48

Allard, G O, Caty, J -L and Gobed, A , 1985 The Ar- chean supracrustal rocks of the Chlbougamau area In L D Ayres, P C Thurston, K D Card and W Weber (Editors), Evolution of Archean Supracrustal Se- quences Geol Assoc Can Spec Pap , 28 55-64

Andrews, A J , 1983 Alteration, metamorphism and structure associated with Archean volcanic-hosted gold deposits, Red Lake District Ont Geol Surv Mlsc Pap , 116 211-215

Anghn, C D and Franklin, J M , 1989 Preliminary lead isotope studies of base metal and gold mineralization in the eastern Wablgoon Subprovmce, northwestern Ontario In Curr Res PartC, Geol Sur Can,89-1C 285-292

Archambault, G , 1985 Archean wrench fault tectonics and structural evolution of the Blake River Group, Abmbl Belt, Discussion Can J Earth Scl, 22 943- 945

Arndt, N T , 1977 Thick, layered pendotl te-gabbro lava flows in Munro Township Can J Earth S o , 14 2620- 2637

Arndt, N T and Nlsbet, E G , 1982 What is a komatute 9 In N T Arndt and E G Nlsbet (Editors), Komatmes Allen and Unwm, London, pp 283-308

Arth, J G and Hanson, G N , 1975 Geochemistry and ongm of the early Precambnan crust of northeastern Minnesota Geochlm Cosmochlm Acta, 39 325-362

Arth, J G , Arndt, N T and Naldrett, A J , 1977 Genesis of Archean komatutes from Munro Township, On- tano trace element evidence Geology, 5 590-594

Ashwal, L D , Wooden, J L , Phmney, W C and Morn- son, D A , 1985 Sm-Nd and Rb-Sr isotope systemat- lcs of an Archean anorthome and related rocks from the Superior Province of the Canadian Shield Earth Planet Scl Lett , 74 338-346

Ashwal, L D , Morgan, P , Kelley, S A and Percival, J A , 1987 Heat production and moblllzauon of heat pro- ducmgelements Earth Planet Scl Let t , 85 439-450

Attoh, K , 1981 Pre- and Post-Dor6 sequences in the

Wawa volcanic Belt, Ontario In Curr Res, Part B, Geol Surv Can, 81-1B 49-54

Ayres, L D , 1969 Geology of Townships 31 and 30 Ranges 20 and 19 Ont Dep Mines, Geol Rep 69, 100 pp

Ayres, L D , 1977 Importance of stratigraphy m Early Precambnan volcanic terranes Cychc volcamsm at Setting Net Lake, northwestern Ontario Geol Assoc Can Spec Pap, 16 243-264

Ayres, L D , 1978 Metamorphism m the Superior Prov- ince of northwestern Ontario and its relationship to crustal development Geol Surv Can, 78-10 25-36

Ayres, L D , 1983 Blmodal volcanism m Archean greenstone belts exemphfied by greywacke composition, Lake Superior Park, Ontario Can J Earth S o , 20 1168-1194

Ayres, L D and Cemy, P , 1982 Metallogeny ofgranltoid rocks m the Canadian Shield Can Mineral , 20 439- 536

Ayres, L D and Thurston, P C , 1985 Archean supracrustal sequences m the Canadian Shield an overview In L D Ayres, P C Thurston, K D Card and W We- ber (Editors), Evolution of Archean supracrustal sequences Geol Assoc Can Spec Pap , 28 343-380

Baragar, W R A , 1968 Major-element geochemistry of the Noranda volcanic belt, Quebec-Ontario Can J Earth Scl , 5 773-790

Barnes, S J , 1985 The petrography and geochemistry of komatnte flows from the Abmbl greenstone belt and a model for their formation Llthos, 18 241-270

Bartlett, J R , 1978 Metamorphic trends m the metasedlmentary rocks north of Eagle Lake, Ontario Thesis Umv Western Ontario, London, Ont , 73 pp (unpublished)

Basu, A R , Goodwm, A M and Tatsumoto, M , 1984 Sm/Nd study of Archean alkahc rocks from the Supe- rior Province of the Canadian Shield Earth Planet Sci Lett , 70 40-46

Bauer, R L , 1985 Correlation of early recumbent and younger upright folding across the boundary between an Archean gneiss belt and greenstone terrane, northeastern Minnesota Geology, 13 657-660

Beakhouse, G P , 1985 The relationship of supracrustal sequences to a basement complex in the western Eng- hsh River Subprovmce In L D Ayres, P C Thurston, K D Card and W Weber (Editors), Evolution of Ar- chean supracrustal sequences Geol Assoc Can Spec Pap , 28 169-178

Beakhouse, G P , McNutt, R H and Krogh, T E, 1988 Comparative Rb-Sr and U-Pb zircon geochronology of late- to post-tectonic plutons in the Winnipeg River belt, northwestern Ontario, Canada Chem Geoi , 72 337-35 l

Bell, C K , 1971 History of the Superior-Churchill Boundary in Manitoba In Geosclence Studies in Manitoba Geol Assoc Can Spec Pap , 9 5-10

148 K D CARD

Bell, K , Blenkmsop, J , Kwon, S T , T&on, G R and Sage, R P , 1986 Age and radlogemc Isotopic systematics of the Borden Lake carbonatlte complex, Ontano, Can- ada Can J Earth Sa ,24 24-30

Buckle, M J , I978 Heat loss from the earth, a constramt on Archean tectonics from the relation between geothermal gradients and the rate of plate production Earth Planet SCI Lett ,40 301-315

Buckle, M J , 1986 Imphcatlons of meltmg for stablhsa- tlon of the lithosphere and heat loss m the Archean Earth Planet Scl Lett ,80 314-324

Bark, D , 1979 Rb/Sr chronology of the Ramy Lake Ar- chean gramtold batholith, Wablgoon Belt, northwest- em Ontario Can J Earth Scl , 16 141-149

Bark, D , KolJonen, T and Rosenberg, R J , 1979 Rare earth dlstnbutlon m Archean gramtold plutons of the Wablgoon volcanic-plutomc Belt, northwestern On- tano Can J Earth Scl , 16 270-289

Blackbum, C E , 1980 Toward a moblhst tectonic model for part of the Archean of Northwestern Ontano Geoscl Can ,7 64-72

Blackbum, C E , Bond, W D , Breaks, F W , Davq D W , Edwards, G R , Paulsen, K H , Trowell, N F and Wood, J , 1985 Evolution of Archean volcamc-sedl- mentary sequences of the western Wablgoon Subprov- mce and its margins a review In L D Ayres, PC Thurston, K D Card and W Weber (Editors), Evo- lutlon of Archean Supracrustal Sequences Geol As- sot Can Spec Pap, 28 89-116

Boland, A V, Elhs, R M , Northey, D J , West, G F, Green, A G , Forsyth, D A , Mereau, R F , Meyer, R P , Morel-&d’Hulssler, P , Buchbmder, G G R , Asudah, I and Haddon, R A R , 1988 Selsmlc dehneatlon of upthrust Archaean crust in Kapuskasmg, Northern Ontano Nature, 335 7 11-7 13

Borradarle, G J , 1982 Companson of Archean structural styles in two belts of the Canadian Supenor Province Precambnan Res , 19 179-189

Breaks, F W , Bond, W D and Stone, D , 1978 Prehml- nary geological synthesis of the Enghsh River Sub- provmce, northwestern Ontano and its beanng upon mmeral exploration Ont Geol Surv Mlsc Pap, 72,

55 PP Breaks, F W , Cherry, M E and James, D A, 1985 Me-

tallogeny of Archean gramtold rocks of the English River Subprovmce, Supenor Province, Ontano, Can- ada a review In Cornwall Conference on High Heat Producmg Granites, Hydrothermal Qrculatlon, and Ore Genesis Inst Mm Metall , 9-3 1

Bnsbm, WC and Green, A G , 1980 Gravity model of the Aulneau batholith, northwestern Ontano Can J Earth Sa , 17 968-977

Brooks, C, Ludden, J , Pigeon, Y and Hubregtse, J J M W , 1982 Volcamsm of shoshomte to h&-K andeslte affinity m an Archean arc environment, Ox- ford Lake, Mamtoba Can J Earth Scl , 19 55-67

Capdevlla, R , Goodwin, A M , UJike, 0 and Gorton, M P , 1982 Trace-element geochemistry of Archean volcanic rocks and crustai growth m southwestern Abltlbl Belt, Canada Geology, 10 418-422

Card, K D , Percival, J A, Lafleur, J and Hogarth, D D , 198 1 Progress report on reponal geologcal synthesis, central Supenor Provmce Geol Surv Can ,8 1 -lA 77- 93

Card, K D , Gupta, V K , McGrath, P H and Grant, F S , 1984 The Sudbury Structure its reglonal geologcal and geophysical setting In E G Pye, A J Naldrett and P E Glblm (Editors), The Geology and Ore Deposits of the Sudbury Structure Ont Geol Surv , 1 25-44

Card, K D and Clesdskl, A , 1986 DNAG No 1 Sub- divisions of the Supenor Province of the Canadian Shield Geoscl Can, 13 5-13

Card, K D , Poulsen, K H and Robert, F , 1989 The Ar- chean Supenor Province of the Canadian Shield and its lode gold deposits Econ Geol Monogr ,6 11-28

Cattell, A , Krogh, T E and Amdt, N T , 1984 Confllct- mg Sm-Nd whole rock and U-Pb zircon ages for Ar- chean lavas from Newton Township, Abitlbl Belt, On- tano Earth Planet Scl Lett ,70 280-290

Cemy, P , Trueman, D L , Zlehlke, D V , Good, B E and Paul, B J , 198 1 The Cat Lake-Wmmpeg River and Weskusko Lake pegmatlte fields, Manitoba Man Dep Energy Mines, Mm Res Dlv , ER 80-1,2 16 pp

Chlpera, S J and Perkins, D , 1988 Evolution of blotlte- garnet geothermometers apphcatlon to the English River subprovmce, Ontano Contnb Mmeral Petrol , 98 40-48

Clark, G S , Bald, R and Ayres, L D , 198 1 Geochronol- ogy of orthognelss adjacent to the Archean Lake of the Woods greenstone belt, northwestern Ontano a possible basement complex Can J Earth Sa , 18 94- 102

Coney, P J , Jones, D L and Monger, J W H , 1980 Cor- dllleran suspect terranes Nature, 288 329-333

Condle, K C , Bobrow, D J and Card, K D , 1988 Geo- chemistry of Precambnan mafic dykes from the south- em Supenor Provmce of the Canadian Shield In H C Halls and W F Fahng (Editors), Mafic Dyke Swarms Geol Assoc Can Spec Pap ,34 95-108

Cook, F A , 1985 Geometry of the Kapuskasmg structure from a hthoprobe pilot reflection survey Geology, 13 368-37 I

Cooke, D L and Moorhouse, W W , 1969 Tlmlskammg volcanism m the Kirkland Lake area, Ontano, Can- ada Can J Earth Sa ,6 117-132

Corfu, F , 1987 Inverse age stratlficatlon m the Archaean crust of the Supenor Province Evidence for mfra- and subcrustal accretions from high resolution U-Pb zlr- con and monazite ages Precambnan Res ,36 259-275

Corfu, F , 1988 Differential response of U-Pb system m coexlstmg accessory minerals, Wmmpeg River Sub- provinces, Canadian Shield lmphcatlons for Archean crustal growth and stabdlzatlon Contnb Mmeral Pe- trol, 98 312-325


Corfu, F and Ayres, L D , 1984 U-Pb age and genetic slgmficance of heterogeneous zircon populations in rocks from the Favourable lake area, northwestern Ontano Contnb Mineral Petrol , 88 86-101

Corfu, F , Krogh, T E and Ayres, L D , 1985 Y-Pb zlr- con and sphene geochronology of a composite Ar- chean gramtold batholith, Favourable Lake area, northwestern Ontano Can J Earth Sa , 22 1436- 1451

Corfu, F and Muir, T L , 1989 The Hemlo-Heron Bay greenstone belt and Hemlo AU-MO deposit, Supenor Province, Ontano, Canada 1 Sequence of Igneous activity determined by zircon U-Pb geochronology Chem Geol ,79 183-200

Corfu, F and Muir, T L , 1989 The Hemlo-Heron Bay greenstone belt and Hemlo AU-MO deposit, Supenor Province, Ontano, Canada 2 Tlmmg of metamorphism, alteration, and Au mmerahzatlon from tltan- lte, rutlle, and monazlte geochronology Chem Geol , 79 201-223

Corfu, F and Stott, G M , 1986 U-Pb age for late magmatism and regonal deformation in the Shebandowan Belt, Supenor Provmce, Canada Can J Earth SCI ,23 1075-1082

Corfu, F and Wallace, H , 1986 U-Pb zircon ages for magma&m m the Red Lake Greenstone Belt, northwestern Ontano Can J Earth Sa ,23 27-42

Corfi, F and Wood, J , 1986 U-Pb zircon ages m supracrustal and plutomc rocks, North Spmt Lake area, northwestern Ontano Can J Earth SCI ,23 967-977

Corfu, F and Andrews, A J , 1987 Geologcal constraints on the timing of magmatlsm, deformation, and gold mmerahzatlon m the Red Lake greenstone belt, northwestern Ontano Can J Earth Sa ,24 1302-l 320

Corfu, F and Grunsky, E C , 1987 Igneous and tectonic evolution of the Batchawana Greenstone Belt, Supe- nor Province a U-Pb zircon and tltamte study J Geol, 95 87-105

Corfu, F and Sage, R P , 1987 A precise U-Pb zircon age for a trondhjemlte clast in the DorC conglomerate, Wawa, Ontano In Proc Abstr ,33rd Annu Inst Lake Superior geology, p 18

Corfu, F , Krogh, T E , Kwok, Y Y and Jensen, L S ,1989 U-Pb zircon geochronology m the southwestern Abl- tlbl greenstone belt, Supenor Province, Can J Earth Sa, 26 1747-1763

Corkery, M T and Lenton, P G , 1984 Cross Lake supracrustal investigation In Man Mm Res Dlv, Rep Field Actlvltles, 1983 32-45

Davis, D W and Edwards, G R , 1982 Zircon U-Pb ages from the Kakag Lake area, Wablgoon Subprovmce, northwest Ontano Can J Earth Sa ,19 1235-1245

Davis, D W and Trowell, N F , 1982 U-Pb zircon ages from the eastern Savant Lake-Crow Lake metavol- came-metasedlmentary belt, northwest Ontano Can J Earth Scl , 19 868-877

Davis, D W , Blackbum, C E and Krogh, T E , 1982 Zir- con U-Pb ages from the Wablgoon-Mamtou Lakes re- gon, Wablgoon Subprovmce, northwest Ontano Can J Earth Sa , 19 254-266

Davq D W , Krogh, T E , Hmzer, J and Nakamura, E , 1985 Zircon dating of polycychc volcanism at Stur- geon Lake and lmphcatlons for base metal mmerahzatlon Econ Geol ,80 1942-1952

Davis, D W and Edwards, G R , 1986 Crustal evolution of Archean rocks in the Kakag Lake area, Wablgoon Subprovmce, Ontano as interpreted from high prea- slon U-Pb geochronology Can J Earth Scl ,23 182- 192

Davis, D W , Poulsen, K H and Kamo, S L , 1989 New insights mto Archean crustal development from geochronology m the Rainy Lake area, Supenor Province, Canada J Geol, 97 379-398

Davis, D W and Jackson, M , 1988 Geochronology of the Lumby Lake greenstone belt a 3 Ga complex within the Wablgoon Subprovmce, northwest Ontano Geol Sot Am Bull , 100 818-824

Davq D W , Sutchffe, R H and Trowell, N F , 1988 Geochronolo@cal constraints on the tectomc evolution of a Late Archean greenstone belt, Wablgoon subprovince, northwest Ontano, Canada Precambnan Res, 39 171-191

Davis, D W , Pezzutto, F and OJakangas, R J , m press The age and provenance of metasedlmentary rocks m the Quetlco Subprovmce, Ontano, from smgle zircon analyses lmphcatlons for Archean sedimentation and tectonics m the Supenor Province Earth Planet Sa Lett

De Rosen-Spence, A F , Provost, G , Dlmroth, E , Goch- nauer, K and Owen, V , 1980 Archean subaqueous felslc flows, Royan-Noranda, Quebec, Canada, and their Quaternary equivalents Precambnan Res , 12 43-77

Dimroth, E , 1985 A mass balance between Archean and Phanerozolc rates of magma emplacement, crustal growth and erosion lmphcations for recyclmg of the contmental crust Chem Geol , 53 17-24

Dlmroth, E , Imreh, L , Rocheleau, M and Goulet, N , 1982 Evolution of the south-central part of the Ar- chean Abltlbl Belt, Quebec Part I stratlgraphy and paleogeographlc model Can J Earth Sa , 19 1729- 1758

Dimroth, E , Imreh, L , Goulet, N and Rocheleau, M , 1983a Evolution of the south-central segment of the Archean Abltlbl Belt, Quebec Part II tectonic evolution and geomechamcal model Can J Earth SCI ,20 1355-1373

Dlmroth, E , Imreh, L , Goulet, N and Rocheleau, M , 1983b Evolution of the south-central segment of the Archean Abltlbl Belt, Quebec Part III plutomc and metamorphic evolution and geotectomc model Can J Earth Scl ,20 1374-l 388

150 KD CARD

Dimroth, E, Rocheleau, M and Mueller, W, 1984 Pa- leography, isostasy and crustal evolution of the Ar- chean Abitlb~ Belt a comparison between the Rouyn- Noranda and Chlbougamau-Chapais areas In J Guha and E H Chown (Editors), Chlbougamau - Stratig- raphy and Mineralization Can Inst Mining Metall Spec Vol, 34 73-91

Dimroth, E and Rocheleau, M, 1985 Archean wrench fault tectonics and structural evolution of the Blake River Group, Abitlbi Belt, Quebec Discussion Can J Earth Scl, 22 941-943

Dimroth, E, Imreh, L, Cousineau, P, Leduc, M and Sanschagrln, Y, 1985a Paleogeographlc analysis of mafic submarine flows and its use in the exploration for massive sulphide deposits In L D Ayres, P C Thurston, K D Card and W Weber (Editors), Evo- lution of Archean Supracrustal Sequences Geol As- soc Can Spec Pap, 28 203-222

Dimroth, E, Rocheleau, M, Mueller, W, Archer, P, Brlsson, H, Fortin, G , Jutras, M, Lefebvre, C, Pich6, M, Pilote, P and Simoneau, P, 1985b Paleogeo° graphic and paleotectonic response to magrnatlc processes a case history from the Archean sequence in the Chibougamau area, Quebec Geol Rundsch, 7411 11- 32

Dods, S D, Teskey, D J and Hood, P J , 1985 The new series of 1 1,000,000-scale magnetic anomaly maps of the Geological Survey of Canada compilation tech- niques and interpretation In W J Hinze (Editor), The Utility of Regional Gravity and Magnetic Anomaly Maps Okla Soc Explor Geophys, 69-87

Doig, R, 1987 Rb-Sr geochronology and metamorphic history of Proterozolc to early Archean rocks north of the Cape Smith fold belt, Qu6bec Can J Earth Sci, 24 813-825

Donaldson, J A and Jackson, G D, 1965 Archaean sed- imcntary rocks of North Spirit Lake area, northwestern Ontario Can J Earth Sci, 2 622-647

Dupr6, B, Cbauvel, G and Arndt, N T, 1984 Pb and Nd isotopic study of two Archean komatntic flows from Alexo, Ontano Geochim Cosmochim Acta, 48 1965- 1972

Dusanowskyj, T H and West, G F , 1976 A gravity study of the Sturgeon Lake area In Proc 1976 Geotraverse Conference, Precambrlan Res Group, Univ Toronto, pp 56-60

Eade, K E, 1966 Fort George River and Kaniapiskau River (west half) map-areas, New Quebec Geol Surv Can Mem 339, 84 pp

Edwards, G R and Sutchffe, R H, 1980 Archean gramtold terranes of the western Supenor Province, On- tario In Geol Assoc Can, Progr with Abstracts, 5, 50

Ermanovics, I F , McRitchie, W D and Houston, W N, 1979 Petrochemistry and tectonic setting of plutonic rocks of the Superior Province in Manitoba In F Bar-

ker (Editor), Trondhjemites, Dacltes and Related Rocks Elsevier, Amsterdam, pp 323-362

Ermanovlcs, I F and Wanless, R K, 1983 Isotopic age studies and tectonic interpretation of Superior Prov- ince In Manitoba Geol Surv Can Pap, 82-12, 22 pp

Frarey, M J and Krogh, T E, 1986 U-Pb zircon ages of late internal plutons of the Abitlbl and eastern Wawa Subprovlnces, Ontario and Quebec Geol Surv Can Pap, 86-1A 43-48

Fraser, J A, Heywood, W W and Mazurskl, M A, 1978 MetamorphlcmapoftheCanadlanShield Geol Surv Can Map 1475A, scale 1 3,500,000

Gari6py, C, All~gre, C J and Lajoie, J , 1984 U-Pb systematics in single zircons from the Pontiac sediments, Abltibl greenstone belt Can J Earth Scl, 21 1296- 1304

G6hnas, L, Melhnger, M and Trudel, P, 1982 Archean mafic metavolcanlcs from the Rouyn-Noranda district, Abitibl greenstone belt, Qu6bec mobility of ma- jorelements Can J Earth Sci, 19 2258-3275

G61inas, L and Ludden, J N , 1984 Rhyolitic volcanism and geochemical evolution of an Archean central rang complex The Blake River Group Volcanlcs in southern Abltlbl Belt, Superior Province Phys Earth Planet Inter, 35 77-88

Gibb, R A, 1983 Model for suturing of Superior and Churchill plates an example of double indentation tectonics Geology, 11 413-417

Gibbs, A K, Payne, B, Setzer, T , Brown, L D, Oliver, J E and Kaufman, S, 1984 Seismic reflection study of the Precambrian crust of central Minnesota Geol Soc Am Bull, 95 280-294

Gibson, I , Roberts, R G and Gibbs, A, 1986 An extensional fault model for the early development of greenstone belts, with reference to a portion of the Abitibi belt, Ontario, Canada Earth Planet Sci Lett, 79 159- 167

Gilbert, H P, 1985 Geology of the Knee Lake-Gods Lake area Manit Dep Energy Mines Geol Rep, 83-1B, 76 PP

Goidich, S S, 1972 Geochronology in Minnesota, In P K Sims and G B Morey (Editors), Geology of Minne- sota a Centennial Volume Mlnn Geol Surv, 27-37

Goldich, S S and Fischer, L B, 1986 Air-abrasion experiments in U-Pb dating of zircon Chem Geol, 58 195- 215

Goodwin, A M, 1962 Structure, stratigraphy and ongln of iron formations, Michlpicoten area, Algoma Dis- trict, Ontario, Canada Geol Soc Am Bull, 73 561- 586

Goodwin, A M, 1977 Archean volcanism in Superaor Province, Canadian Shield Geol Assoc Can Spec Pap, 16 205-241

Goodwln, A M and Ridler, R H, 1970 The Abitibi orogenic belt In Symposium on Basins and Geosynchnes of the Canadian Shield Geol Surv Can Pap, 70-40 1-24


Goodwln, A M and Smith, I E M , 19 80 Chemical discontinuities in Archean metavolcanlc terrains and the development of Archean crust Precambnan Res, l 0 301-311

Goodwin, A M , Thode, H G , Chou, C L and Karkhan- sis, S N , 1985 Chemostratigraphy and origin of the late Archean siderite-pyrite-rich Helen Iron Forma- tion, Mlchiplcoten belt, Canada Can J Earth Sci, 22 72-84

Goulet, N , 1978 Stratigraphy and structural relationships across the Cadillac-Larder Lake Fault, Rouyn- Beauchantel area, Quebec M E R Q , DPV-602, 155 PP

Gower, C F and Clifford, P M , 1981 The structural geometry and geological history of Archean rocks at Kenora, northwestern Ontario - a proposed type area for the Kenoran Orogeny Can J Earth Scl, 18 1075- 1091

Gower, C F , Crocket, J H and Kablr, A , 1983 Petrogen- esls of Archean granitold plutons from the Kenora area, English River Subprovince, northwest Ontario, Can- ada Precambnan Res, 22 245-270

Green, A G , Hajnal, Z and Weber, W , 1985 An evolutionary model of the western Churchill Province and western margin of the Superior Province in Canada and the north-central United States Tectonophyslcs, 116 281-322

Gupta, V K , Thurston, P C and Dusanowskyj, T H , 1982 Constraints upon models ofgreenstone belt evolution by gravity modelling, Blrch-Uchl greenstone belt, northern Ontario Precambnan Res, 16 233-255

Hall, D H and Brisbin, W C , 1982 Overview of regional geophysical studies in Manitoba and northwestern Ontario Can J Earth Scl, 19 2049-2059

Halls, H C , 1982 Crustal thickness in the Lake Superior region In R T Wold and W J Hlnze (Editors), Ge- ology and Tectonics of the Lake Superior Basin Geol Soc Am Me, 156 239-243

Hamilton, W B, 1979 Tectonics of the Indonesian region U S Geol Surv Prof Pap , 1078, 345 pp

Hamilton, W B, 1988 Plate tectonics and island arcs Geol Soc Am Bull, 100 1503-1527

Hanmer, S , 1986 Asymmetrical pull-aparts and foliation fish as kinematic indicators J Struct Geol , 8 111- 122

Heaman, L D , 1988 A precise U-Pb zircon age for a Hearst dyke Geol Assoc Can Abstr , 13, p A53

Heaman, L M , Machado, N , Krogh, T E and Weber, W , 1986 Precise U-Pb zircon ages for the Molson dyke swarm and the Fox River sill Constraints for Early Proterozoic crustal evolution in northeastern Mani- toba, Canada Contrib Mineral Petrol, 94 82-89

Hillary, E M and Ayres, L D , 1980 TrondhjemitlC basement enclave near the Archean Favourable Lake volcanic complex, northwestern Ontario, Canada Can J Earth S o , 17 652-667

Hodgson, C J , 1983 The structure and geological development of the Porcupine camp - a re-evaluation In A C Colvlne (Editor), The Geology of Gold in On- tario Ont Geol Surv ,Misc Pap , 110 211-225

Hoffman, P F , 1985 Is the Cape Smith Belt (northern Quebec) a khppe 9 Can J Earth Sci, 22 1361-1369

Hoffman, P F , 1988 United plates of America, the birth of a craton Early Proterozolc assembly and growth of Laurentia Annu Rev Earth Planet Sci, 16 543-603

Hoffman, P F and Ranalli, G , 1988 Archean oceanic flake tectonics Geophys Res Lett , 15 1077-1080

Hofmann, H J , Thurston, P C and Wallace, H , 1985 Archean stromatohtes from Uchi greenstone belt, northwestern Ontario In L D Ayres, P C Thurston, K D Card and W Weber (Editors), Evolution of Ar- chean Supracrustal Sequences Geol Assoc Can Spec Pap , 28 125-132

Holcomb, R T , Moore, J G , Llpman, P W and Belder- son, R H , 1988 Voluminous submarine lava flows from Hawaiian volcanoes Geology, 16 400-404

Hooper, P and Ojakangas, R W , 1971 Early deforma- tional history of Archean rocks in the Vermilion dis- trlct, northeastern Minnesota Can J Earth Sci, 8 423-434

Holubec, J , 1972 Lithostratigraphy, structure and deep crustal relations of Archean rocks of the Canadian Shield, Rouyn-Noranda area, Quebec Krystallnlkum, 9 63-88

Hubert, C and Ludden, J N , 1986 Archean wrench-fault tectonics in the Abltibi greenstone belt of Canada In Workshop on the Tectonic Evolution of Greenstone Belts Lunar Planet Isnt Contr lb, 584 59-61

Hubert, C , Trudel, P and G611nas, L , 1984 Archean wrench fault tectonics and structural evolution of the Blake River Group, Abltlbl Belt, Quebec Can J Earth Sci, 21 1024-1032

Hubregtse, J J M W , 1980 The Archean Plkwltonei granuhte domain and its position at the margin of the northwestern Superior Province (central Manitoba) Man Dep Energy Mines, Geol Pap , 80-3 16 pp

Huddleston, P J , Schultz-Ela, D and Southwick, D L , 1988 Transpression in an Archean greenstone belt, northern Minnesota Can J Earth Sci, 25 1060-1068

Hunt, P A and Roddick, J C , 1987 A compilation of K - Ar ages Geoi Surv Can Pap 87-2

Hyde, R S , 1980 Sedimentary facies in the Archean Tlmiskaming Group and their tectonic lmphcatlons, Abitlbi greenstone belt, northeastern Ontario, Can- ada Precambrlan Res, 12 161-195

Imreh, L , 1973 Relations stratigraphique entre ie Groupe de Pontiac et le slllon metavolcanlque de Baby au T6miscamingue, Qu6bec Can J Earth Sci, 10 1350- 1353

Jensen, L S , 1985 Stratigraphy and petrogenesis of Ar- chean metavolcanlc sequences, southwestern Abltibi Subprovince, Ontario In L D Ayres, P C Thurston,

152 K D CARD

K D Card and W Weber (E&tors), Evolutmn of Ar- chean supracrustal sequences Geol Assoc Can Spec Pap, 28 65-87

Jollffe, A W, 1966 Stratigraphy of the Steeprock Group, Steep Rock Lake, Ontario Geol Assoc Can Spec Pap, 3 75-98

Jolly, W T, 1978 Metamorphic history of the Archean Abltlbl belt In J A Fraser and W W Heywood (Edi- tors), Metamorphism m the Canadian Shield Geol Surv Can Pap, 78-10 63-78

Jolly, W T, 1987 L~thophfle elements m Huroman low- T~ continental tholemes from Canada and evolutmn of the Precambnan mantle Earth Planet So Lett, 85 401-415

Kalhokoskl, J , 1987 The Pontmc problem, Quebec-On- tario, m hght of gravity data Can J Earth Scl, 24 1916-1919

Kang, D E, Sarewltz, D R and Haeck, G D, 1986 Role of stnke-shp faulting m the evoluUon ofallochthonous terranes m the Phlhppmes Geoloy, 14 852-855

Kehlenbeck, M M, 1986 Folds and folding m the Beard- more-Geraldton fold belt Can J Earth Scl, 23 158- 171

Krogh, T E, 1982 Improved accuracy of U-Pb zircon ages by the creation of more concordant systems using an mr abrasmn techmque Geoch~m Cosmoch~m Acta, 46 637-649

Krogh, T E and Turek, A, 1982 Precise U-Pb zircon ages from the Gamlugama greenstone belt, southern Supe- rlorPrownce Can J Earth Scl, 19 859-867

Krogh, T E, Ermanoxacs, I F and Davis, G L, 1974 Two episodes of metamorphism and deformation m the Ar- chean rocks of the Canadmn Shield In Carnegie Inst Geophys Lab Yearbook, 73 573-575

Krogh, T E, Hams, N B W and Davis, G L, 1976 Ar- chean rocks from the eastern Lac Seul region of the Enghsh R~ver gneiss belt, northwestern Ontario, part 2 Geochronology Can J Earth So , 13 1212-1215

Krogh, T E, Heaman, L, Machado, N, Davis, D and Weber, W, 1986a GS-36 U-Pb geochronology program P~klw~tone~-Thompson-Cross Lake Area In Report of Field Activates, 1986, Manlt Energy Mines, pp 178-180

Krogh, T E, Corfu, F and Percival, J A, 1986b U-Pb zircon and sphene ages from the Kapuskasmg zone m the Chapleau-Agawa Bay region In Progr w~th Ab- stracts, Geol Assoc Can Mm Assoc Can, 11 191

Lafleur, P J , 1986 The Archean Round Lake bathohth, Ab~t~b~ greenstone belt a synthes~s Thes~s Umv Ot- tawa, 245 pp

Langford, F F and Monn, M A, 1976 The development of the Superior Province of Northwestern Ontario by mergmg ~sland arcs Am J Scl, 276 1023-1034

Lalo~e, J and Ludden, J , 1984 Petrology of the Archean Pontmc and Kewagama se&ments and ~mphcaUons for the stratigraphy of the southern Ab~t~b~ belt Can J Earth Sc~, 21 1305-1314

Lawson, A C, 1885 Report on the geology of the Lake of the Woods region, w~th special reference to the Kee- warm (Huromang) belt of the Archaean rocks Geol Surv Can, Rep, 1, 151 pp

Longstaffe, F J , 1979 The oxygen isotope geochemistry ofArchean gramtolds In F Barker (Editors), Tron- dhjemltes, Dacltes, and Related Rocks Elsevier, Am- sterdam, pp 363-399

Longstaffe, F J , Cerny, P and Muehlenbachs, K, 1981 Oxygen-isotope geocbemlstry of the gramto~d rocks m the Winnipeg R~ver pegmat~te district, southeastern Mamtoba Can Mineral, 19 195-204

Longstaffe, F J , McNutt, R H and Crocket, J H, 1982 Rare-earth element modelling of Archean meta-~g- neous and igneous rocks, Lake Despair area, northwestern Ontario Precambrlan Res, 17 275-296

Ludden, J N and Gehnas, L, 1982 Trace element char- actenst~cs of komatutes and komatnt~c basalts from the Abltlbl metavolcamc belt of Qu6bec In N T Arndt and E G Nlsbet (Editors), Komatlltes Allen and Un- win, London, pp 331-346

Ludden, J N, Hubert, C and Gan6py, C, 1986 The tectomc evoluuon of the Ab~tlb~ greenstone belt of Can- ada Geol Mag, 123 153-166

Macdonald, A J , 1983 A re-apprmsal of the Geraldton goldcamp, Ont Geol Surv, Mlsc Pap 116 194-197

Machado, N, Heaman, L, Krogh, T E and Weber, W, 1987 GS-31 U-Pb geochronology program Thomp- son belt-northern Supenor Province Mamt Energy Mines, Miner Div Rep Field Actlwt~es, 1987 145- 147

Machado, N, Goulet, N and Gan6py, C, 1989 U-Pb geochronology of reactivated Archean basement and of Hudsoman metamorphism in the northern Labra- dorTrough Can J Earth So , 26 1-15

Maynard, J B, Vallonl, R and Yu Ho-Shmg, 1982 Com- posmon of modern deep sea sands from arc-related basins In J K Leggett (Editor), Trench-Forearc Ge- ology Geol Soc Lond Spec Pap, 10 551-561

McGdl, G E and Shrady, C H, 1986 Evidence for a complex Archean deformatmnal history, southwestern Mlchlplcoten greenstone belt, Ontario J Geophys Res, 91 E281-E289

McRltchle, W D and Weber, W, 1971 Metamorphism and deformatmn m the Manlgotagan gne~ss~c belt, southeastern Manitoba In W D McRltchle and W Weber (E&tors), Geology and Geophysics of the Rice Lake Regton, Southeastern Mamtoba (Project P~- oneer) Mamt Mines Branch Publ, 71-1 235-284

Mmlst Energ~e Resour Quebec Ontario Geol Surv, 1984 Llthostratlgraphlc map of the Abltlbl Subprov- race Ont Geol Surv/Mm Energle Res, Que, Map 2484/D P 83-16, scale 1 500,000

Meyn, H D and Palonen, P A, 1980 Stratigraphy of an Archean submanne Precambnan Res, 12 257-285

Mezger, K, Bohlen, S R and Hanson, G N, 1986 GS-


43 Investigations of metamorphism m the Plkw~tonel Domain Mamt Energy Mines, Rep Field Act~wtles, 1986 204-205

Morey, G B, Sims, P K, Cannon, W F, Mudrey, M G, Jr and Southwlck, D L, 1982 Geologtcal Map of the Lake Superaor Region, Minnesota, Wisconsin, and northern Michigan, Mmn Geol Surv Map S-13, scale 1 1,000,000

Momson, D A, Davis, D W, Wooden, J L, Bogard, D D, Maczuga, D E, Phmney, W C and Ashwal, L D, 1985 Age of the Mulcahy Lake intrusion, N W Ontario, and lmphcauons for the evolution of greenstone-granlte terrains Earth Planet Scl Lett, 73 306-316

Mortensen, J K, 1987 Prehminary U-Pb zircon ages for volcanic and plutonlc rocks of the Noranda-Lac Abl- tlbl area, Abitlbl Subprovmce, Quebec Geol Surv Can Pap,B7-1A 581-589

Mortensen, J K and CleSlelslo, A, 1987 U-Pb zircon and sphene geochronology of Archean plutomc and orthogne~sslc rocks of the James Bay region and Blen- vdle Domain Quebec In Radiogenic Age and Iso- toplcStu&es, Rep 1 Geol Surv Can Pap,87-2 129- 134

Mortensen, J K and Percival, J A, 1987 Reconnmssance U-Pb zircon and monazlte geochronology of the Lac Clalrambault area Ashuanlpl complex, Quebec In Ra&ogemc Age and Isotopic Studies, Rep 1 Geol Surv Can Pap, 87-2 136-142

Monensen, J K, Thenault, R F and Card, K D, 1988 U-Pb and Rb-Sr age constraints for plutomsm and metamorphism in the Pontiac Subprovlnce and adjacent Grenville Prownce In Geol Assoc Can Mm Assoc Can Progr Abstracts, 13, p A87

Moser, D, 1988 Structures of the Wawa gneiss terrain near ChapleauOntarlo Geol Surv Can Pap, 88-1C 93-99

Mueller, W and Dlmroth E, 1984 Sedimentary and de- positional history of the Blondeau and Cheblstuan Formations in the Waconichl synchne, Chlbougamau, Quebec In J Guha and E H Chown (Editors), Chl- bougamau - Stratigraphy and Mmerahzation Can Inst MmmgMetall Spec Vol, 34 137-152

Muir, T L, 1985 Hemlo tectono-stratlgl'aphlc study Ont Geol Surv Mlsc Pap, 126 71-74

Nunes, P D and Jensen, L S, 1980 Geochronology of the Abltib~ metavo!camc belt, Karkland Lake area - progress report In E G Pye (Editor), Summary of Geo- chronology StudIes 1977-1979 Ont Geol Surv M P, 92 40-45

Nunes, P D and Thurston, P C, 1980 Two hundred and twenty mdhon years of Archean evolution a zircon U- Pb age stratlgraphic study of the Uchl-Confederation Lakes greenstone belt, northwestern Ontano Can J EarthScl, 17 710-721

Nunes, P D and Pyke, D R, 1981 Time-stratlgraphlc correlation of the Kadd Creek orebody with volvanic

rocks south of Tlmmins, Ontario, as inferred from zircon U-Pb ages Econ Geol, 76 944-951

Nunes, P D and Wood, J , 1980 Geochronology of the North Spirit Lake area, District of Kenora - progress report In E G Pye (Editor), Summary of Geochron- ology Stu&es 1977-1979 Ont Geol Surv M P, 92 7-14

Ojakangas, R W, 1985 Review ofArchean clastlc sedimentation, Canadian Shield major felslc volcanic contributions to turbldite and alluvial fan-fluvial facies associations In L D Ayres, P C Thurston, K D Card and W Weber (Editors), Evolution of Archean Supracrustal Sequences Geol Assoc Can Spec Pap, 8 23-48

Park, R G and Ermanovlcs, I F, 1978 Tectonic evolution of two greenstone belts from the Superior Prov- ince in Manitoba Can J Earth So , 15 1808-1816

Patchett, P J, Kuovo, O, Hedge, C E and Tatsumoto, M, 1981 Evolution of continental crust and mantle het- erogeneity evidence from Hflsotopes Contnb Min- eral Petrol, 78 279-297

Percival, J A. 1983 High-grade metamorphism in the Chapleau-Foleyet area, Ontano Am Mineral, 68 668- 686

Percival, J A, 1986 A possible exposed Conrad Dlscon- tmmty m the Kapuskasing uplift, Ontario In Reflec- uon Seismology the Continental Crust (Geodyn Ser, 14) Am Geophys Union, Washington, D C, pp 135- 141

Percival, J A and Card, K D, 1983 Archean crust as revealed in the Kapuskasmg uplift, Superior Province, Canada Geology, 11 323-326

Percival, J A and Krogh, T E, 1983 U-Pb zircon geochronology of the Kapuskasmg Structural Zone and vicinity in the Chapleau-Foleyet area, Ontario Can J Earth Sci, 20 830-843

Percival, J A and Card, K D, 1985 Structure and evolution of Archean crust in central Superior Province, Canada In L D Ayres, P C Thurston, K D Card and W Weber (Editors), Evolution ofArchean Supracrus- tal Sequences Geol Assoc Can Spec Pap, 28 179- 192

Percival, J A and Stern, R A, 1984 Geological synthesis in the western Superior Province, Ontario Geol Surv Can Pap, 84-1A 397-408

Percival, J A, Stern, R A and Dlgel, M R, 1985 Re- gional geological synthesis of western Superior Prov- ince, Ontario Geol Surv Can Pap, 85-1A 385-397

Percival, J A and McGrath, P H, 1986 Deep crustal structure and tectonic h~story of the northern Kapus- kasmg uplift of Ontario an integrated petrological- geophysical study Tectonics, 5 553-572

Percival, J A and Girard, R, 1988 Structural character and history of the Ashuampl complex in the Scheffer- vllle area, Quebec-Labrador Geol Surv Can Pap, 88- IC 51-60

Percival, J A and Williams, H R, 1989 Late Arche'an

154 KD CARD

Quetlco accretionary complex Superior Province, Canada Geology, 17 23-25

Percival, J A and Sulhvan, R W , 1986 Age constraints on the evolution of the Quetlco belt, Superior Prov- ince, Ontario In Workshop on the Tectonic Evolution of Greenstone Belts Lunar Planet Inst Con tnb , 584 91-93

Perkins, D and Chlpera, S J , 1985 Garnet-orthopyrox- ene barometry applied to the English River Subprov- ince, the Minnesota River Valley and other high-grade terranes Contrib Mineral Petrol , 86 69-80

Plcard, C and Piboule, M , 1986 P6trologle des roches volcanlques du slllon de roches vertes archeennes de Matagaml-Chibougamau/l l 'ouest de Chapais (Abl- tibl est, Qu6bec) 2 Le groupe hautement potasslque d'Opemlsca Can J Earth Scl, 23 1169-1189

Poulsen, K H , 1983 Structural setting of vein-type gold mineralization in the Mine Centre-Fort Francis area implications for the Wabigoon Subprovlnce In A C Colvlne (Editor), The Geology of Gold In Ontario Ont Geol Surv MlsC Pap , l l 0 174-180

Poulsen, K H , 1986 Rainy Lake wrench zone an example of an Archean Subprovlnce boundary In northwestern Ontario In Workshop on the Tectonic Evo- lution of Greenstone Belts Lunar Planet Inst Contnb, 584 97-99

Poulsen, K H , Borradalle, G J and Kehlenbeck, M M , 1980 An inverted Archean succession at Rainy Lake, Ontario Can J Ear thSci , 17 1358-1369

Pye, E G , 1965 Georgia Lake area Ont Dep Mines Geol Rep, 31. l l 3 pp

Pyke, D R , Naldrett, A J and Eckstrand, O E, 1973 Ar- chean ultramafic flows in Munro Township, Ontario Geol Soc Am Bull, 84 955-978

Raclcot, D , Chown, E H and Hanel, T , 1984 Plutons of the Chlbougamau-Desmaralsville belt a preliminary survey In J Guha and E H Chown (Editors), Chl- bougamau - Stratigraphy and Minerahzatlon Can Inst MlnlngMetall Spec Vol, 34 178-197

Robert, F , 1989 Internal structure of the Cadillac tectonic zone southeast of Val d'Or, AbltibI belt, Quebec Can J Earth Sci, 26 2661-2690

Rocheleau, M and Dlmroth, E , 1985 Petrology of the Archean Pontiac and Kewagama sediments and implications for the stratigraphy of the southern Abmbl belt Discussion Can J Earth S o , 22 1374-1379

Roddick. J A and Hutchison, W W , 1972 Plutonic and associated rocks of the Coast Mountains of British Co- lumbia In 24th Int Geol Congr Guidebook A04-C04. Can, 71 pp

Roscoe, S M and Donaldson, J A , 1988 Uranlferous pyritic quartz pebble conglomerate and layered ultramafic intrusions In a sequence of quartzite, carbonate, iron formation and basalt of probable Archean age at Lac Sakaml, Quebec Geol Surv Can Pap , 88-1C 117-121

Rudnlck, R L , Ashwal, L D and Henry, D J , 1984 Fluid inclusions in high-grade gnelsses of the Kapuskasing Structural Zone, Ontario metamorphic fluids and uphft/eroslonpath Contrib Mineral Petrol, 87 399- 406

Rudnlck, R L , McLennan, S M and Taylor, S R , 1985 Large ion lithophile elements in rocks from high pressure granuhte facies terrains Geochlm Cosmochlm Acta, 49 1645-1655

Sage, R P , 1987 Preliminary interpretation of the relationship between economic minerahzatlon and volcanic stratigraphy in the Wawa area Ont Geol Surv MlSc Pap , 100 41-44

Sawyer, E W , 1986 The influence of source rock type, chemical weathering and sorting on the geochemistry of clastlc sediments from the Quetlco metasedlmentary belt, Superior Province, Canada Chem Geol , 55 77-95

Schulz, K J , 1980 The magmatlc evolution of the Ver- milion greenstone belt, N E Minnesota Precambrian R e s , l l 215-245

Schwerdtner, W M , 1984 Foliation patterns in large gneiss bodies of the Archean Wablgoon Subprovlnce, southern Canadian Shield J Geodyn, 1 313-337

Schwerdtner, W M , Stone, D , Osadetz, K , Morgan, J and Stott, G M , 1979 Granitoid complexes and the Archean tectonic record in the southern part of northeastern Ontario Can J Earth Sci, 16 1965-1977

Scoates, R F J , 1983 A preliminary stratigraphic exami- nation of the ultramafic zone of the Bird River Sill (part of 52L/SNE) Manlt Miner Res, Div , Rep FleldActivlties, 1983 70-83

Shaw, D M , Truscott, M G , Gray, E A and Middleton, T A , 1988 Boron and hthium in high-grade rocks and minerals from the Wawa-Kapuskasing region, On- tario Can J Earth Scl, 25 1485-1502

Shegelskl, R J , 1980 Archean cratonizatlon, emergence and red bed development, Lake Shebandowan area, Canada Precambrian Res, 12 331-347

Shlrey, S B and Hanson, G N , 1984 Mantle-derived Ar- chean monzodiorltes and trachyandesltes Nature, 310 222-224

Shlrey, S B and Hanson, G N , 1986 Mantle heteroge- neity and crustal recycling In Archean granite-greenstone belts evidence from Nd isotopes and trace elements in the Rainy Lake area, Ontario Geochlm Cosmochlm Acta, 50 2361-2651

Shirey, S B and Carlson, R W , 1986 Rb and Nd isotope evolution of the Archean Superior Province mantle enrichment and present subcontlnental mantle reser- voirs Terra Cognita, 6 237

Sims, P K , 1976 Early Precambrlan tectonic-igneous evolution in the Vermilion District, northeastern Min- nesota Geol Soc Am Bull, 87 379-389

Sims, P K , Card, K D , Morey, G B and Peterman, Z E, 1980 The Great Lakes Tectonic Zone - a major crus-


tal structure in central north Amenca Geol Soc Am Bull, 91 690-698

Skulskl, T , Hynes, A and Francis, D , 1988 Basic lavas of the Archean La Grande greenstone belt Products of polybaslc fractlonatlon and crustal contamination Contrlb Miner Petrol, 100 236-245

Sleep, N H and Wmdley, B F , 1982 Archean plate tectonics constraints and inferences J Geol , 90 363- 379

Smith, T E, Huang, C H , Riddle, C and Choudhry, A G , 1985 The geochemistry of Archean igneous and meta- igneous rocks, Gamltagama area, Wawa (Shebando- wan) Sub-province, Ontano Neues Jahrb Miner Abh,151 53-86

Southwlck, D L and Sims, P K , 1980 The Vermilion granitic complex - a new name for old rocks in northern Minnesota U S Geol Surv Prof Pap , 1124-A A1--A11

Stern, R A , Hanson, G N and Shlrey, S B, 1989 Petro- genesis of mantle-derived, LILE-ennched Archean monzodlontes and trachyandemtes (sanukltolds) in southwestern Superior Province Can J Earth Scl, 26 1688-1712

Stevenson, I M , 1968 A geological reconnaissance of Leaf River map-area, New Quebec and Northwest Territo- ries Geol Surv Can Mem,356 , l l 2 p p

Stockwell, C H , 1982 Proposals for time classification and correlation of Precambnan rocks and events in Canada and adjacent areas of the Canadian Shield, Part I a time classification of Precambnan rocks and events Geol Surv Can Pap , 80-19, 135 pp

Stone, D , 1976 The Sydney Lake cataclastlc zone In Proc 1976 Geotraverse Conf, Umv Toronto, pp 88- 91

Stott, G M and Schnelders, B R , 1983 Gold mlnerah- zatlon in the Shebandowan belt and its relation to regional deformation patterns In A C Colvme (Edi- tor), The Geology of Gold in Ontario Ont Geol Surv Mlsc P a p , l l 0 181-193

Studemelster, P A , 1983 The greenschlst facies of an Ar- chean assemblage near Wawa, Ontario Can J Earth S o , 20 1409-1420

Sullivan, R W , Sage, R P and Card, K D , 1985 U-Pb zircon age of the Jubilee stock in the Mlchlplcoten greenstone belt near Wawa, Ontario Geol Surv Can Pap , 95-1B 361-365

Sutchffe, R H and Sweeney, J M , 1985 Geology of the Lac des Isles complex, District of Thunder Bay Ont Geol Surv M P , 126 47-53

Sylvester, P J , 1989 Post-colhsonal alkaline granites J Geoi , 97 261-280

Sylvester, P J , Attoh, K and Schulz, K J , 1987 Tectonic setting of late Archean blmodal volcanism in the M1- chlplcoten (Wawa)greenstone belt, Ontario Can J Earth Scl , 24 1120-1134

Talra, A , Salto, Y and Hashlmoto, M , 1983 The role of

oblique subductlon and strike slip tectonics in the evolution of Japan In T W C Hdde and S Uyeda (Edi- tors), Geodynamlcs m the western Pacific - Indone- sian region (Geodyn Ser, 8) Am Geophys Union, Washington, D C , pp 303-306

Talbot, C J , 1973 A plate tectonic model for the Ar- chaeancrust Phdos Trans R Soc Lond ,A273 413- 427

Taylor, F C , 1982 Reconnaissance geology of a part of the Canadian Shield, northern Quebec and Northwest Temtones Geoi Surv Can Mem, 399, 32 pp

Teal, P R and Walker, R G , 1977 Stratigraphy and sedlmentology of the Archean Mamtou Group, northwestern Ontario Geol Surv Can Pap , 77-1A 181- 184

Thurston, P C and Breaks, F W , 1978 Metamorphic and tectonic evolution of the Uchl-Engllsh River Subprov- ince In J A Fraser and W W Heywood (Editors), Metamorphism in the Canadian Shield Geol Surv Can Pap , 78-10 49-62

Thurston, P C and Chlvers, K M , in press Secular van- atlon in greenstone sequence development emphasiz- ing Superior Province, Canada Precambnan Res

Thurston, P C and Fryer, B J , 1983 The geochemistry of repetitive cyclical volcanism from basalt through rhyolite in the Uchl-Confederatlon greenstone belt, Canada Contrlb Mineral Petrol, 83 204-226

Timmms, E A , Turek, A and Symons, D T A , 1985 U - Pb zircon geochronology and paleomagnetlsm of the Bird River greenstone belt, Manitoba Geol Assoc Can Mln Assoc Can, Progr with Abstracts, 10, p 62

Toogood, D J and Hodgson, C J , 1986 Relationship between gold deposits and the tectonic framework of the Abltlbl greenstone belt in the Karkland Lake-Larder Lake area Ont Geol Surv Mlsc Pap , 130 79-86

Turek, A , Smith, P E and Van Schmust, W R , 1984 U - Pb zircon age and the evolution of the Mlchlplcoten plutonlc-volcanlc terrane of the Superior Province, Ontario Can J Earth Scl, 21 457-464

Turek, A , Carson, T M , Smith, P E, Van Schmus, W R and Weber, W , 1986 U-Pb zircon ages for rocks from the Island Lake greenstone belt, Manitoba Can J Earth S o , 23 92-101

Turek, A , Keller, R , Van Schmus, W R and Weber, W , 1987 U-Pb zircon ages for the Rice Lake area, southeastern Manitoba Can J Earth Scl, 26 23-30

Turek, A , Van Schmus, W R and Songe, R P , 1988 Ex- tended volcanism in the Mlchlplcoten greenstone belt, Wawa, Ontario In Geol Assoc Can, Mm Assoc Can, Prog with Abstracts, 13, p A127

Turner, C C and Walker, R G , 1973 Sedlmentology, stratigraphy and crustal evolution of the Archean greenstone belt near Sioux Lookout, Ontario Can J Earth Scl, 10 817-845

Ujlke, O , 1985 Geochemistry of Archean alkahc voi-

156 KD CARD

camc rocks from the Crystal Lake area, east of Kark- land Lake, Ontario, Canada Earth Planet Sc~ Lett, 73 333-344

Ujlke, O and Goodwm, A M, 1987 Geochemistry and ongm of Archean felslc metavolcamc rocks, central Noranda area, Quebec, Canada Can J Earth Scl, 24 2551-2567

Van de Kamp, P C and Beakhouse, G P, 1979 Parag- ne~sses m the Pakwash Lake area, English R~ver gneiss belt, northwest Ontario Can J Earth Scl, 16 1753- 1763

Van de Walle, M, 1978 Canton de Montbefllard Town- ship Mm R~ch Nat, Geol Rep., 188, 128 pp

Walker, J W R, 1967 Geology of the Jackfish-Mlddleton area Ont Dep Mines, Geol Rep, 50, 38 pp

Weber, W and Scoates, R F J , 1978 Archean and Proter- OZOlC metamorphism m the northwestern Superior Province and along the Churchill-Superior boundary, Manitoba Geol Surv Can Pap, 78-10 5-16

Wdks, M E and Nlsbet, E G, 1985 Archean stromatohtes from the Steep Rock Group, northwestern On- tario, Canada Can J Earth Scl, 22 792-799

Wdhams, H R, 1987 Structural studies m the Wablgoon and Quetlco subprownces Ont Geol Surv Open File Rep, 5668, 163 pp

Wllhams, H R, in press Subprovmce accretion tectomcs in the south-central Superior Province Can J Earth Sct

Wdson, H D B, 1971 The Superior Province m the Pre- cambrian of Mamtoba In A C Turnock (Editor), Geosc~ence Studies in Manitoba Geol Assoc Can Spec Pap, 9 41-49

Wood, J , 1977 Geology of the North Sprat Lake area, Dlstnct of Kenora (Patncla Portion) Ont Dlv Mines Geoi Rep, 150, 60 pp

Wood, J , 1980 Ep~clast~c sedimentation and stratigraphy m the North Sprat Lake and Rainy Lake areas, a comparison Precambnan Res, 12 227-255

Wooden, J L, Goldlch, S S and Suhr, N H, 1982 Origin of the Morton gneiss, southwestern Minnesota 2 Geochemistry Geol Soc Am Spec Pap, 182 57-75

Woodsworth, G J , Crawford, M L and Holhster, L S, 1983 Metamorphism and structure of the Coast Plu- tomc Complex and adjacent belts, Prance Rupert and Terrace areas, British Columbia In Geol Assoc Can Mln Assoc Can, 1983 Annu Meet, Victoria, B C, Field Trip No 14, 41 pp

Yoshlda, T (Editor), 1975 An Outhne of the Geology of Japan Geol Surv Jap, 61 pp

Young, R A, Wright, J and West, G F, 1986 Seismic crustal structure northwest of Thunder Bay, Ontario In M Barazangl and L D Brown (Editors), Reflec- tion Seismology The Continental Crust (Geodyn Ser, 14) Am Geophys Umon, Washington, D C, pp 143- 155

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