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RE and BPS (Ti, Zr, Nb, P, Y) element evolution

of Archaean mafic-ultramafic volcanic suites,

Pilbara Block, Western Australia

A.Y. Glikson,* C. Pride,** B. Jahn***

R. Davy**** and A. H. Hickman****

B.M.R. Record No. 1986/6

Bureau of Mineral Resources, Geology andGeophysics, Canberra, Australia

University of Ottawa, Ontario, Canada

Institute of Geology, University of Rennes,Rennes -Cedex, France

Geological Survey of Western Australia,Perth, Western Australia

List of contents

Abstract^ P. 1

1.^INTRODUCTION^ 3

II. RARE EARTH ELEMENT PATTERNS^ 5

III. RELATIONS BETWEEN RE AND HFS (Ti,Zr,Nb,Y,P) ELEMENTS^8

IV. COMPARISONS WITH OTHER MAFIC-ULTRAMAFIC VOLCANIC

SUITES^ 11

V. PETROGENESIS^ 12VI.^CONCLUSIONS AND TECTONIC IMPLICATIONS^24

Acknowledgements^ 28References^ 29

Tables^ 40Figure captions^ 45Figures^ 50Appendix I

Appendix II^ 8.5

Abstract

Determinations of rare earth (RE) and high field strength (HFS)

elements (Ti, Zr, Nb, P, Y) in 3.7-2.7 by.old mafic to ultramafic

volcanic sequences in the Pilbara Block, Western Australia, show marked

stratigraphic-geochemical variations. These variations are interpreted

in terms of source mantle heterogeneities and magmatic fractionation

processes. The regularity of RE patterns and RE-alkali elements-Mg°

relations suggest that the role of crustal contamination was limited.

Three principal phases of RE and HFS evolution are recognized: (1) 3.7-

3.4 b.y. (lower Warrawoona Group), marked by tholeiitic basalts with

positive (Ce/Yb)N ratios (1.0-3.0) and Ce>Zr>Nb>Ti>P>Y enrichment

orders relative to chondrites; (2) 3.4-3.0 b.y. (upper Warrawoona

Group, Gorge Creek Group, Warambie Basalt) marked by tholeiitic basalts

with lower (Ce/Yb)N (1.0-2.3) and variable HFS element enrichment

orders, and (3) 3.0-2.7 b.y. (Louden Volcanics, Negri Volcanics,

Fortescue Group), marked by very high total RE, high (Ce/Yb)N (3.4-6.3)

and high HFS element abundances. Most Pilbara basalts analysed are

geochemically distinct from the contemporaneous light-RE depleted and

HFS-chondritic greenstones of the central and eastern Yilgarn Block.

Petrological modelling suggest that (Ce)N - (Ce/Yb)N relations in 3.7-

3.6 b.y. old basalts are consistent with batch melting of^chondritic

garnet lherzolite mantle source. The 3.4-3.0 b.y. old basalts can be

interpreted in terms of dynamic melting. The 3.0-2.7 b.y. old basalts

are interpreted in terms of partial melting of light RE-enriched mantle

containing a high (>30%) alkali basalt component.^Departures of RE

and HFS element ratios from chondritic values are further accounted for

only in part by fractional crystallization of clinopyroxene and

plagioclase, as suggested by comparisons between (1) model primary

magma compositions calculated by iterative addition of olivine to Qz-

tholeiite analyses, and (2) associated high-Mg basalts. The role of

Cpx fractionation is supported by low CaO/Al 2 0 3 ratios and by

comparisons of the RE data with model fractionation trends. The

indicated heterogeneity of mantle source regions underlying the Pilbara

Block may be significant in relation to tectonic activity. The 3.7-3.4

and 3.0-2.7 b.y. phases may reflect relatively stable periods during

which upper mantle sources were slightly to strongly enriched in RE and

HFS elements, possibly derived by addition of melts produced by

incipient melting of garnet lherozolite sources. The 3.4-3.0 b.y.

phase was characterised by differential vertical movements between

uprising batholiths and intervening rifted basins where clastic

sediments of the Ca 3.0 b.y. Gorge Creek Group accumulated. This phase

involved diapiric mantle activity producing peridotitic komatiites and

dynamic remelting of strongly convecting mantle, by analogy with late

Archaen igneous activity in the central and eastern parts of the

Yilgarn Block. The 3.0-2.7 Gyr phase tapped strongly light RE enriched

subcontinental mantle. Significantly, the breaks between the above

three phases coincided with major plutonic and volcanic felsic igneous

activity about 3.4-3.5 b.y. ago and 3.0 b.y. ago.

3

I.^INTRODUCTION

This report discusses the RE (rare earth) and HFS (high field

strength) elements characteristics of Archaean greenschist-facies

tholeiitic basalts (TB)*, andesitic and silicified basalts (TA)

dolerites (TD), high-Mg basalts (HMB) and peridotitic komatiite (PK).

The 3.7-2.7 b.y. old metamorphosed volcanic sequences of the Pilbara

Block, Western Australia, reveal distinctive RE and HFS element

patterns for individual volcanic units, allowing insight into temporal

geochemical variations in the early mantle and crust (Glikson, 1979;

Glikson and Hickman, 1981 a,b; Jahn et al., 1981; Barley and Bickle,

1982; Hickman, 1983). These patterns are discussed in terms of the

composition of source regions of the volcanic magmas, partial melting

and magmatic fractionation processes, possible contamination and

alteration. The rare earth elements (RE), because of their

systematic ionic radii change with an atomic number, distinctive

crystal/liquid partition coefficients (Kd), and relative immobility

during alteration, provide criteria for the investigation of source

characteristics and nature of mineral phase fractionation. The low Kd

values of the RE and HFS elements (Arth, 1976; Irving, 1978; Hanson,

* Petrochemical definitions are given at the bottom of Table 1.

- 4 -

1980), result in similarities between their ratios in primary

komatiiitic magmas and their mantle sources (Nesbitt and Sun, 1976; Sun

and Nesbitt, 1977, 1978), provided no crustal assimilation/

contamination processes have severely affected the magmas. The purpose

of this report is to (1) examine systematic variations in RE and HFS

element characteristics of Pilbara volcanics; (2) compare the RE

distribution with that of other Archaean and younger volcanic suites,

and (3) consider petrogenetic and tectonic implications of the data.

The geology of the northern part of the Pilbara Block has been

described by Hickman (1983), and further information is given by Bickle

et al. (1983), Barley et al, (1984) and Groves and Batt (1984). The

samples studied for RE elements have been collected as a part of a BMR-

GSWA regional geochemical study (Glikson and Hickman, 1981a, Glikson

and Davy, in prep.). Sample classifications and localities are given

in Table 1 and Fig. 1 and petrographic descriptions in Appendix I.

Determinations were made by instrumental neutron activation (INAA)

analysis by C. Pride (54 samples) and isotope dilution (ID) analyses by

B. Jahn (6 samples). Accuracy for Ce, Sm, Nd, Eu, Yb is +/- 5% and for

Tb, Lu, Th and Hf +/- 10% of the amount present. For further

qualification of accuracy and precision refer to Jacobs et al (1977)

and Hanson (1976). RE data for spinifex-textured komatiites of the

Negri Volcanics (Sun and Nesbitt, 1978) are also discussed. In

addition to the RE element determinations chemical analyses were

conducted using the following methods: (1) Th, U and Hf by INAA at the

University of Ottawa by C. Pride; (2) Si, Al, Ti, Fe (total Fe as

Fe 20 3 ), Mn, Mg, Ca, Na, K, P, Ga, Rb, Sr, Y, Zr, Ba and Pb by X-ray

fluorescence at BMR laboratories, using an automated Philips PW-1210

spectrometer and applying the methods of Norrish and Hutton (1969) and

Norrish and Chappell (1967); and (3) Li, Cr, Co, Ni, Cu and Zn by

atomic absorption spectrometry at BMR laboratories, using a Varian

Techtron spectrophotometer. Evaluations of accuracy and precision of BMR

data are given by Sheraton and Labonne (1978). Computer programs used

in conjuction with this paper are reported elsewhere (Glikson and Owen,

1982).

II.^RARE EARTH ELEMENT PATTERNS

Major element and trace element data and CIPW norms are

presented in Appendix I. The major element features are portrayed on

the normative 01-Opx-Cpx-Qz tetrahedron (Fig. 2), indicating the

importance of Qz and Opx-rich compositions. The Qz-normative nature of

the tholeiitic basalts and even some high-Mg basalts (NSB, NV, NB) have

been interpreted in terms of shallow-level fractionation of olivine

(Glikson, 1983). However, crustal contamination and secondary

silicification have contributed silica. In particular, Fortescue Group

basalts (notably the Mt Roe Basalt) contain high normative Qz, some of

which is clearly secondary. Chondrite-normalized RE patterns indicate

flat to light RE (LRE)- enriched patterns (Fig. 3). There is a broad

sympathetic relation between Si0 2 , total RE and (Ce/Yb)N* values (Fig.

4), and an overall decrease in total RE and (Ce/Yb)N with Mg'** values

(Appendix I). RE characteristics of different volcanic units are

summarized for tholeiitic basalts (TB) in Table 2 and can be compared

on Figs 4-9.

*^N = Chondrite normalized value

** 100 Mg0/(Mg0 + FeO) (Mol%)

6

Some of the main features of the data set are as follows. TB of

the Talga-Talga Subgroup and dolerites of the Duffer Formation display

a wide range of total RE (@ 20-80 ppm) and positive light/heavy RE

fractionation (Ce/Yb)N @ 1-3. Analyses of TB of the North Star Basalt

obtained by isotope dilution spectrometry have negative Nb and Eu

anomalies (Fig, 3a) while analyses of more fractionated TB of lower Mg'

value obtained by neutron activation show weak negative Nd anomalies

(Fig. 3b). TB of the Euro Basalt show low total RE ( -40 ppm) and near-

flat chondritic profiles (Ce/Yb)N @ 1-2. Low RE are also typical of TB

of the Gorge Creek Group and the Warambie Basalt (Fig, 4). TB of the

former have near-flat heavy RE (HRE) patterns, while two samples of the

latter unit have positive Eu anomalies. TB of the Negri Volcanics have

moderately high total RE (@ 60 ppm) and highly fractionated light/heavy

RE, (Ce/Yb)N @ 6 (Fig, 4). TB of the Louden Volcanics have lower total

RE (@ 35-55 ppm) than the Negri Volcanics, fractionated light RE

((Ce/Sm)N @ 2.2-2.5) and often near-flat heavy RE ((Sm/Yb)N @ 1.4-2.3).

RE characteristics of TB of the Mt Roe Basalt are similar to the Negri

Volcanics. The three upper units of the Fortescue Group - Kylena

Basalt, Nymerina Basalt and Maddina Basalt - display remarkably high

total RE abundances (@ 70-160 ppm) and strong fractionation of the

light RE (Ce/Sm)N @ 2.3-2.7. The heavy RE are somewhat less

fractionated ((Sm/Yb)N @ 1.5-1.8) and thus (Ce/Sm)N>(Sm/Yb)N.

Most samples within individual volcanic units show regular RE

profiles, which is suggestive of little departure from original igneous

patterns. Departures from regularity may be related to advanced

tholeiitic fractionation shown by high FeO and TiO 2 abundances (samples

75040026A, 45062), enrichment in CO 2 which complex the RE (Collerson

-7 -

and Fryer, 1978; Hanson, 1980) (samples 80040273, 49349) and hydration

(sample 99375). However, plots of total RE and of (Ce/Yb)N versus CO 2

do not reveal systematic variations.

In view of their Qz normative compositions and geochemical

variability (Figs 4-13) tholeiitic basalts are unlikely to represent

primary magmas, unless formed at shallow depth under high H 20 partial

pressures (Nicholls and Ringwood, 1972). Inspite of their metamorphism

to chlorite-tremolite assemblages, the high-Mg basalts (HMB) have

fairly regular RE patterns which are likely to be near-primary. Total

RE levels in HMB vary widely, i.e. @ 20-40 ppm in the NSB, below 5 ppm

in the AB, @ 10-20 ppm in the CB and @40-60 ppm in the NV. Since the

high Mg basalts have fractionated mainly olivine and orthopyroxene,

whose KdRE

are almost nil, the RE patterns of these rocks more

representative of mantle composition. The RE profiles of high-Mg

basalts are analogous to those of spatially associated tholeiites in

some volcanic units, i.e. NSB, AB, CB, HB and NB (Fig. 3), reflecting

the compositional continuity between TB and HMB (Glikson and Hickman,

1981a). In particular, the analogy between the strongly

light/intermediate fractionation of RE of HMB and TB of the Negri

Volcanics is noted (Figs 4, 6). The light/heavy RE fractionation in

the HMB is less than in the associated TB. (Ce/Sm)N and (Sm/Yb)N values

are still higher than in most mid-ocean ridge and ophiolitic basalts.

Samples whose Mg' value exceeds 60 usually show (Ce/Yb)N ratios of less

than 2.0. HMB of the Negri Volcanics (Sun and Nesbitt, 1978)

constitute exceptions in this regard, with (Ce/Yb)N values of @ 3-4

(Table 2. Fig. 5).

Ill.^RELATIONS BETWEEN RE AND HFS (Ti, Zr, Nb, Y, P) ELEMENTS

Ti, Zr, Nb, Y and P are relatively stable during sea water-rock

interaction (Hart, 1971; Humphries and Thomson, 1978; Staudigel and

Hart, 1983), and have been extensively used in petrogenetic studies in

relation to tectonic environment (Pearce and Cann, 1973); Pearce, 1975;

Pearce and Norry, 1979). The very low Kd (mineral/melt partition

coefficients) values of these elements for olivine and orthopyroxene

result in a behaviour similar to the RE. Nesbitt and Sun (1976) have

shown that chondritic ratios between these elements are commonly

retained in metamorphosed primary high-Mg lavas, and many tholeiites

with the exception of P - which is considered to have behaved as a

siderophile component upon metal/silicate liquid fractionation of the

mantle during core formation (Sun, 1984). Variations in ratios such as

Ti/Zr, Ti/Y, Zr/Y, Zr/Nb and Y/Yb may help to identify magmatic

fractionation processes when interpreted in the light of experimental

and naturally observed Kd values. However, attempts to apply HFS

elements to finger-printing ancient tectonic environments (Pearce et

al., 1977) must take into account vertical and horizontal

heterogeneities in magmatic source regions of basalts (Green, 1971;

Glikson and Hickman, 1981b).

Pilbara volcanic units display stratigraphic differences in HFS

element abundances. TiO 2 decreases in tholeiitic basalts with

stratigraphic level, from 0.5 -2.3% in the lower Warrawoona Group to

0.5-1.7% in the upper Warrawoona Group, to lower levels in

stratigraphically higher volcanics (Table 2; Appendix I). It

correlates positively with total RE and and Y in the Warrawoona Group

9

and Gorge Creek Group (Fig. 9g). Fortescue Group basalts have markedly

higher RE/Ti ratios than stratigraphically Lower units, showing a TiO 2

range of 0.6-1.4% and an RE range of 50-160 ppm. No obvious relations

are observed between TiO2

and (Ce/Yb)N ratios.

When the Pilbara rocks are treated as a single group, a good

correlation exists between Ce and Zr (r = 0.94) (fig. 9a) and also

between Ce and P (r = 0.70). These correlations suggest concentrations

of RE in minor phases such as zircon and apatite. A positive

correlation is seen on Zr - (Ce/Yb)N plots and a general negative trend

on Ti/Zr - (Ce/Sm)N plots (Fig. 10). In comparison to model mantle

ratios Ti/Zr and Zr/Ce are low to chondritic, Zr/Hf ratios range from

chondritic to high, Zr/Y, Zr/Nb and P/Zr are high to very high. Ti/Y

and Ti/P are similar or higher than primitive mantle in tholeiitic

basalts of the Warrawoona Group, and similar or lower than primitive

mantle in the Fortescue Group. The breakdown of these relations in

terms of individual volcanic units is given in Table 4 and Figs 9g and

9h.

The data reflect near-chondritic character for HFS elements of

some tholeiitic basalts in the Apex Basalt, Euro Basalt, Charteris

Basalt and Honeyeater Basalt (Table 3). The marked departures of HFS

elements from chondritic ratios shown by tholeiitic basalts of the

other volcanic units reflect relative enrichment of these elements in

the following orders:

NSB - Zr> Nb> Ti> P> Y; NAB - Zr> Nb> Ti>Y> P and Zr >Ti >P >Y;

DF (dolerites)- Zr>Ti>Y>P>Nb; AB - P>Zr>Ti>Y>Nb;

EB - Zr>P>Ti>Nb>Y; CB - P>Zr>Ti>Y>Nb;

- 10 -

HB - Zr> P> Y> Ti>Nb; WB - P> Ti> Zr> Y>Nb; NV - Zr>Nb> P> Ti> Y;

LV - Zr>Nb> P> Y> Ti and Zr> P> Ti> Y; MRB - Zr> P>Nb> Y> Ti;

KB - Zr>Nb> P> Y> Ti; NB - Zr>Nb> P> Y> Ti; MB - Zr>Nb> P> Y> Ti

These patterns show that, except for the light RE, zirconium is

the most generally enriched of the HFS elements with respect to

chondritic ratios, except in the Charteris Basalt and the Warambie

Basalt where P is most enriched. Of the above HFS elements, Y and Ti

are normally least enriched with respect to chondrites. Nb normally

closely follows Zr in the enrichment sequence. Ti is the third most

strongly relatively enriched element in lower Warrawoona Group basalts

and in dolerites of the Duffer Formation, while P is the third most

enriched element in tholeiitic basalts of the EB, HB, LV, NV and

Fortescue Group. Tholeiitic basalts of the Louden Volcanics and

Fortescue Group display depletion in Ti relative to other HFS elements

and also Nb depletion - suggesting these elements were removed by

ilmenite or Ti-magnetite (Pearce and Norry, 1979).

In view of the fractionated nature of tholeiites relative to

primary magmas (Green, 1973) , HFS element relations in the high-Mg

basalts may be expected to be closer to primary magma and mantle

values. However high-Mg basalts of the NSB, lower Warrawoona Group,

have low Ti/Zr and Ti/Y and high Ti/P, Zr/Y, Zr/Nb and (Ce/SON as

compared to primitive mantle. HMB of the Apex Basalt, Charteris

Basalt and Honeyeater Basalt have Ti/Zr ratio similar to Chondrites

(Table 4). High-Mg basalts of the Negri Volcanics, in variance from

the tholeiitic basalts, display strong depletion of Ti relative to Zr

and Y (Ti/Zr and Ti/Y similar to NSB), primitive mantle to high Ti/P

ratios, and high Zr/Y ratios (Table - 4). Four high-Mg basalts.

of the Nymerina Basalt are characterized by low Ti/Zr and Ti/P, high

Ti/Y. Zr/Y and 7r/Nb (Table 4). Some enrichment sequences shown by high-Mg

basalts are as follows:

NSB - Zr >Y>Ti >Nb>P; AB - P> Zr> Y .>Ti>Nb; CB - Ti>Zr> Y>P>Nb

and Zr >Y >Ti> P >Nb;

HB - P> Y >Zr > Ti>Nb; NB - Zr>Nb > P >Y > Ti.

Similar enrichment orders occur in tholeiitic basalts and high-Mg

basalts of the Nymerina Basalt. The differences between enrichment

sequences of co-existing TB and HMB in other units throw some doubt on

their cogeneity and/or fractionation history. On the other hand, RE

pattern analogies and the compositional continuity between TB and HMB

support interpretation of their relations in terms of fractional

crystalization of magnesian primary magmas. The contrasted enrichment

patterns of HFS elements in the lower Warrawoona Group and the

Fortescue Group with respect to Ti and P perhaps reflect the role of

apatite as a host of RE in the latter group. This possibility is in

accord with the negative Eu anomalies shown by some Fortescue Group

basalts in similarity with apatite (Hanson, 1980).

IV. COMPARISONS WITH OTHER MAFIC-ULTRAMAFIC VOLCANIC SUITES

Comparisons between RE patterns of the Pilbara volcanics, other

Archaean terrains and ophiolitic and oceanic domains (Figs 4, 5, 7, 8)

indicate that the Pilbara rocks, by contrast to the latter groups,

mostly have (Ce/Yb)N^unity. Tholeiitic and high-Mg basalts of

the Warrawoona Group (@ 3.7-3.4 Gyr) show some similarities with those

of the contemporaneous Onverwacht Group of the eastern Transvaal (Jahn

— 12 —

et al., 1982), but differ from the light RE depleted late Archaean

greenstone suites of the Yilgarn Block (Sun and Nesbitt, 1978) and

other late Archaean terrains (Jahn et al., 1980). The very high total

RE and (Ce/Yb)N values of tholeiites of the Fortescue Group above the

Mt Roe Basalt distinguish these rocks from the similar aged Yilgarn

greenstone. These values are even higher than those of Scourie

dolerites ((Ce/Yb)N @ 2-6) which Weaver and Tarney (1981) considered

typical of continental tholeiite suites. While tholeiitic basalts of

the Warrawoona Group display RE and HFS elements values within the

range of normal to enriched mid-ocean ridge basalts (MORB), the Louden

Volcanics, Negri Volcanics and Fortescue Group basalts have certain

features similar to boninites (high-Mg andesites) (Sun and Nesbitt,

1978; Cameron et al., 1979; Cameron and Nisbitt, 1982; Nisbet and Sun,

1980; Hickey and Frey, 1982), i.e. high Si0 2 (50-57%), high (Ce/Yb)N

(4-6), RE profiles with (Ce/Sm)N>(Sm/Yb)N and near-flat heavy RE

patterns, low Ti/Zr (below 50), Ti0 2/P 20 5 (4-10) and CaO/Al 20 3 (@ 0.5)

(Figs 4, 9 f&h, 11, 12c). However, total RE, Ti and other HFS element

abundances are much higher in the Pilbara basalts than in boninites,

consequently they have significantly lower CaO/Ti0 2 and Al 203/Ti02 .

The strong depletion shown by arc-trench tholeiites and calc-alkali

basalts in transition metals (Ni, Cr, Co, V) is not recognized in

Pilbara volcanics (Glikson and Hickman, 1981a,b).

V.^PETROGENESIS

The relative stability of high field strength (HFS) elements (most

RE, Y, Zr, Hf, Nb, Ti) as compared to other large ion lithophile (LIL)

elements (Na, K, Rb, Sr, Ca, Eu) during metamorphism renders them

useful in the study of the origin of metamorphosed volcanic rocks

- 13 -

(Pearce and Cann, 1973; Pearce, 1975; Humphries and Thomson, 1978;

Beswick, 1982, 1983; Staudigel and Hart, 1983; Condie et al., 1977;

Jahn et al., 1982).

The distribution of RE and HFS elements may be due to inherent

mantle heterogeneity, mantle fractionation or contamination.

The latter process, through incorporation of even small proportions of

geochemically evolved sialic material, may significantly increase the

light RE levels in the basalt. As an example, assimilation of 10%

granite with 80 ppm Ce and 5 ppm Yb by MORB-type magma is capable of

raising the Ce/Yb ratio by a factor of about 1.5. Equaly, mobile

components such as Si0 2 , alkalies, U and Th may be readily introduced

into the basic magma. Huppert and Sparks (1985) suggested that

assimilation of sialic materials by high temperature magnesian magma

may be reflected by positive K-Mg and Rb-Mg correlations. Metamorphic

mobility of the LIL elements in amphibolitized dykes was shown by

Weaver and Tarney (1981) to be in the sequence RbBa>KSTh>LaCe. On

the other hand, the following features suggest that RE and HFS element

relations in the analyzed light-RE enriched rocks may be largely

contamination-free:

(1) The close coherence of chondrite-normalized RE patterns of the

strongly light-RE enriched basalts of the Louden Volcanics,

Negri Volcanics and Fortescue Group is inconsistent with sialic

contamination, unless accompanied by thorough mixing.

(2) For most units an inverse correlation exists between Ce and MgO

and between total RE and Mg' value, suggesting that RE abundances

are primarily related to tholeiitic magmatic fractionation.

— 14 —

(3) In contrast to Huppert and Sparks' (1985) observed increase in K

and Rb with MgO, reflecting crustal assimilation, negative to

constant relations between alkalies and MgO pertain to the Pilbara

volcanics, which militates against significant contamination.

Also, no positive correlation is observed between RE and alkali

elements.

In modelling RE fractionation, a mantle source X2 chondrite

abundances was assumed for comparative purpose (Sun, 1982; Anders and

Ebihara, 1982; Evensen et al., 1978), using Kd values from Arth (1976).

Model RE patterns obtained by partial melting of such a source, leaving

01 and Opx in the residue, are capable of matching the heavy and middle

RE patterns but are not compatible with the relative light RE

enrichment of many volcanic units (Fig. 3). The models plotted in this

figure assume variable source mantle RE-enrichment factors, residual

phase proportions and melt fractions (F). Because of uncertainties

inherent in these assumptions no precise model-data matchings were

attempted, and model fields are plotted for reference only. Chondritic

source enrichment factors range from about X2 for Charteris Basalt

models to about X10 for Kylena Basalt models. Although the mismatch

between the models and the light RE patterns may be overcome if garnet

and/or amphibole remained in the residue, as these phases do not appear

on the liquidus at the degrees of melting (>20%) required to produce

the observed basaltic compositions (Green, 1971, 1973), this is

unlikely. Thus, the magmas were probably not derived solely from a

chondritic source.

- 15 -

Tarney et al. (1980) interpreted light RE-enriched basic magmas in

terms of enrichment of chondritic mantle by liquid components produced

by incipient fusion of garnet lherzolite. The RE patterns of such

magmas are modelled in Fig. 3 g-o for small F - (0.025-0.1) and

residual 01 (60%), Opx (18%), Cpx (14%) and Gnt (8%), after Frey et al.

(1978). The RE profiles derived from this model are consistent with

the light/medium RE patterns of the Pilbara data but are too steep with

regard to the medium/heavy RE patterns. The differences may indicate

derivation of the light RE enriched magmas by partial melting of

enriched mantle sources (Tarney et al. 1980). Estimates of the

proportion of such RE-rich fractions may be obtained from the

approximate position of the RE data patterns between the chondritic (A)

and the light RE-enriched (B) partial melt fields portrayed in Fig. 3.

Further estimates are made below on the basis of log(Ce)N -log(Ce/Yb)N

plots (fig. 6). Tarney et al. (1980) calculated a series of RE

fractionation models on this diagram, including equilibrium partial

melting, closed system and open system fractional crystallization,

continuous dynamic melting, magma mixing and zone refining for magmas

derived from chondritic and light RE-depleted mantle sources (Fig. 6).

Chondrite-normalized plots for Ce/Yb against Ce show that Pilbara rocks

of most units do not lie on any single magmatic fractionation line

proposed by Tarney et al (1980). However, the limited data suggest

that equilibrium batch melting of a lherzolite or a garnet-lherzolite

source may have contributed to the Euro Basalt, the Louden and Negri

Volcanics and the Mount Roe Basalt. The data for the Mount Roe Basalt,

and possibly the Apex Basalt, also lie close to the curve indicating

high-pressure open-system crystal fractionation of a source involving

ecolgitic residue. The data for the Louden Volcanics are also

consistent with mixing of a LRE-depleted mantle source and ocean-floor

— 16 —

type alkali basalt. All other units show relations which are

inconsistent with any single, model trends, i.e. no unit

unequivocally follows any given fractionation-source model, which hints

at a considerable degree of mantle heterogeneity.

Other problems arising from attempted model-data matching include:

(1) the small but significant (Yb/Lu)N<1.0 ratios of the data; (2)

common negative Eu anomalies, and some positive Eu anomalies; (3)

marked departures of alkali elements (Rh, Ba, K), alkali earth elements

(Sr) and highly charged large ion lithophile elements (U, Th, Pb) from

regular chondrite-normalized patterns. The first could reflect

amphibole fractionation since Kd*Kdn (Irving, 1978). However, since

amphibole is an unlikely residual phase in basic magmas these anomalies

may reflect an analytical problem (S. Sun, pers. comm., 1984).^The

second is attributable either to fractionation of plagioclase, or

secondary remobilization of Eu +2 due to the low Kd of Eu +2 in

silicates relative to aqueous chloride-rich and CO 2 -rich solutions

(Flynn and Burnham, 1978). The third may reflect secondary

redistribution of the more mobile elements (Smith and Smith, 1976;

Condie et.al., 1977).

Assuming a model pyrolite source (Ringwood, 1975) with trace

element abundances X2 ordinary chondrite (Sun, 1982), the effects of

precipitation of 01, Opx, Cpx, Gnt, Hb and Plg from a primary magma

derived by 30% melting of the source have suggested in Table 5 have

been calculated and plotted in Figs 6-13. The residue includes 01

(Fo90) and aluminous orthopyroxene (En90) at a ratio of 3:1. The

calculations apply Kd values for RE from Arth (1976) and Hanson (1980),

for Zr, Y and Nb from Pearce and Norry (1979), and for P from Schilling

— 17 —

et al. (1980). The model primary magma is used in turn to derive

crystal fractionation trends for precipitating mineral phases by

surface equilibrium according to Rayleigh's law (Shaw, 1970), and the

fractionation trends are plotted for comparisons with Pilbara data.

The relations between (Ce)N and (Sm)N indicate that, while little

fractionation of the RE is effected by crystallization of 01, Opx and

Pig, the (Ce/Sm)N ratios increase by precipitation of Cpx, Hbl and Gnt

(Fig. 5a). However, the magnitude of this light RE enrichment is

sufficient to account only for some of the Warrawoona Group basalts.

(Sm)N-(Yb)N relations (Fig. 5h) show that a combination of Cpx and Gnt

crystallization from the assumed primary magma is capable of producing

some of the compositions of the Warrawoona Group, Gorge Creek Group and

Whim Creek Group, but cannot account for the more highly fractionated

samples of the Warrawoona Group or, in particular, the Fortescue Group

(Fig. 5b). Fractionation of Gnt decreases the total RE abundance and

elevates the (Ce/Yb)N ratios. Hornblende fractionation is more

effective in increasing (Ce/Sm)N and garnet is more effective in

increasing (Sm/Yb)N (Fig. 8). Co-precipitation of Gnt and Cpx is

capable of accounting for some of the observed RE fractionation, as

evident on (Ce/Yb)N - (Yb)N plot (fig. 7) and (Ce/Sm)N - (Sm/Yb)N plot

(fig. 8). On the other hand, co-precipitation of Gnt and Hbl is

unlikely in view of the exclusive fields of these phases on phase

diagrams for basaltic magmas (Green, 1971, 1973). The RE plots

collectively suggest few consistent crystallization trends for the

various volcanic units. The Charteris Basalt comes closest to the

assumed primary magma derived by 30% melting of pyrolite. The plots

indicate that, if the model primary magma is a source of basalt of the

other units, combination of Cpx, Gnt, Hbl and Pig separations can only

— 18 —

give rise to some of the samples, which suggests that heterogeneous

mantle sources existed.

Model fractionation trends for the HFS elements partly explain

departures of the data from chondritic compositions (Fig. 9). An

increase in Zr/Y ratios above the chondritic value (2.4) is affected by

KdY >KdZr of Cpx, Opx, Hbl and Gnt (Fig. 9b). However, the very high

Zr/Y ratios (4-8) of samples of the Negri Volcanics and Fortescue Group

are suggestive of a high Zr/Y ratio in the source. A sharp departure

from chondritic ratios is also shown by Ti/Zr values in Fortescue Group

basalts (Fig. 9f), and cannot be accounted for by crystal fractionation

of a chondritic parent magma.

However, the departure of Ti/Zr ratios as well as (Ce/Sm)N ratios

from chondritic ratios was probably enhanced by Cpx and/or Hbl

separation, as shown by the negative trend on (Ce/Sm)N-Ti/Zr - plots

(Fig. 10), since Ti and Sm have higher Kd C Px than Zr and Ce. The same

consideration applies to (Ce/Sm)N-Ti/P - relations (Fig. 11). The

lack of linearity on these plots reflects the heterogeneous nature of

magma sources. Divergent trends are observed on Ti-Y plots (Fig. 9g) -

Warrawoona Group basalts display an increase in Ti/Y ratios above

chondritic values (280), attributable to 01, Opx and Cpx fractionation,

or to Ti-rich source, while Fortescue Group basalts display a marked

decrease in Ti/Y ratios, possibly due to an RE-enriched source.

Precipitation of Cpx is hardly sufficient to account for the high P

levels and low Ti/P ratios of the Fortescue Group data (Fig. 9h).

Precipitation of Cpx, Hbl and Pig from RE-chondritic magma is

consistent with the low Ca/Ti and Al/Ti ratios of many Pilbara basalts

(Fig. 12a, 12b). Although separation of Gnt would significantly

— 19 —

enhance some of the above trends, the petrological objections outlined

below rule out this possibility.

The data patterns underline the difficulty in discriminating

between geochemical variations produced by mantle source

heterogeneities and those produced by precipitation of phases with high

Kd for heavy RE and HFS elements. Further evidence is provided by

experimental petrology. Green's (1971) petrogenetic grid for mantle-

derived liquids shows that the stability field of amphibole in pyrolite

(0.1% H 20) extends up to 20 kb, where this phase disappears on 1-2%

melting, whereas at low pressures it disappears at @ 10% melting.

Garnet, by contrast, is mainly stable above 25 kb, and disappears

between 25-35 kb on up to 15% melting. Neither phase is thus likely

on the liquidi of Pilbara tholeiitic to high-Mg compositions, since

they represent above 20% melting (Green, 1973). Separation of garnet

can thus only occur upon either very small degree of melting or with

extremely advanced fractional crystallization at high pressures, while

that of amphibole would occur under shallower depth and higher pH 20

conditions. The latter process would be accompanied by magnetite

separation and strong depletion in Cr and V. not observed in Pilbara

basalts (Glikson and Hickman, 1981a, b). Since neither process appears

likely for the high-Qz normative tholeiites and the high-Mg basalts, RE

and HFS element heterogeneity of the mantle source prior to the main

partial melting events provide a more attractive explanation. The

scarcity of undersaturated alkali volcanics in Archaean greenstone

belts, demonstrated more by trace elements levels than by the high

silica contents (which may be secondary), suggests that such

metasomatic mantle enrichment was confined to the mantle and has not

given rise to extrusion of alkali magma.

— 20 —

If light RE enrichment of mantle source regions of Pilbara

volcanic suites is accepted the question arises whether this is an

original feature of the Archaean mantle or reflects on its subsequent

modification. A Sm-Nd isochron age of 3560 ± 32 Myr measured on

samples of the upper part of the North Star Basalt yields an initial

143Nd/

144Nd ratio of 0.508104 ± 34 from which a model time integrated

Sm/Nd ratio of 0.308 ± 0.004 is deduced (Hamilton et al., 1981). This

ratio is very close to the chondritic ratio 0.31 (Evensen et al., 1978)

derived from the Angra dos Reis achondrite (4550 Myr; I Nd = 0.50682)

(Lugmair and Marti, 1977). Fletcher and Rosman (1982) recalculated the

ENd value of the North Star Basalt from Hamilton et.al's. data. The

positive sign of this parameter suggests a positive Sm/Nd ratio of the

source and thus a long term time-integrated depletion of the mantle in

light RE, probably due to early differentiation. Similar observations

have been made in the Yilgarn Block and in other Archean terrains

(McCulloch and Compston, 1981).

As suggested above, it is likely that both mantle heterogeneity

and fractionation of Cpx and pig played a role in the derivation of

some of the Pilbara basalts. Considerations based on major element

composition of the basalts can be applied to test this possibility.

Frey et al. (1978) estimated the extent of fractional crystallization

of alkali to tholeiitic basalts by iterative addition of olivine (in

equilibrium with the magma) to obtain model primary magma compositions

in equilibrium with mantle olivine (Fo88-90), applying Roeder and

Emslie's (1970) relationship: Kd FP ici. = 0.3. However, the F

(residual liquid fraction) values obtained from such calculations can

be applied to estimates of primary incompatible trace element levels

— 21 —

only if 01 and Opx (Kd @ nil) precipitated from the magma. However, as

suggested above on the basis of trace elements, and as shown below by

mass balance calculations for major elements, this is unlikely. The

role of precipitating phases can be evaluated by comparisons between

model primary magma compositions and the analyses of the Archaean high-

Mg basalts (HMB) providing a test as to whether the latter may

represent primary magmas in view of their high Mg' values (69<) and

high Ni and Cr abundances (Appendix I).

In view of their advanced fractionation tholeiitic basalts are

unlikely to represent primary trace element patterns, except if the

magmas formed at shallow depth under high pH 20 partial pressures

(Nicholls and Ringwood, 1972). By contrast, the trace element patterns

of high Mg basalts (HMB), which have fractionated mainly olivine and

orthopyroxene of very low KdRE

, render the RE patterns of these rocks

significant vis-a-vis mantle composition (Sun and Nesbitt, 1977, 1978).

Comparisons between model primary magmas derived by iterative 01

additions to Qz-tholeiites and the data for high-Mg basalts reveal

marked discrepancies. Thus, tholeiitic basalts of the North Star

Basalt require very large olivine additions (40-60%) to obtain Mg'

values in equilibrium with mantle olivine - a result of the high Fe

abundance in these rocks. Consequently, Mg0 levels of the model

primary magmas are too high, and SiO2'

Al203

and CaO levels are too low

in comparison to the HMB. This discrepancy clearly points to

precipitation of Ca and Al bearing phases, i.e. Cpx and Plg. The model

primary magmas also have high TiO 2 (0.9-1.5%) as compared to the high-

Mg basalt, which would have been partly removed by Cpx, supporting the

above interpretation. The generally low Ca/A1 ratios of the Qz-

tholeiites (Fig. 13c) are consistent with an earlier loss of Cpx.

—22—

Similar relations are observed between model primary magmas and HMB of

other volcanic units.

It is useful to attempt estimates of proportion of fractionated

residual phases, which would in turn allow an idea on the bulk Kd

coefficient and primary magma abundances of various trace elements.

Such calculations require knowledge of: (1) the major element

composition of a model primary magma. From this composition and that

of the analyzed volcanic rock the residue composition may be obtained

by mass balance, (equation 1), and the proportion of residual phases by

a CIPW norm; (2) The F value required for the mass balance calculation

and for subsequent trace element fractionation calculations (equation

2) is given by equation 3, and (3) application of appropriate Kd

values:

for major elements: CE =FC

E + (1-F)C

Ep^1^r

e^efor trace elements: C

p = C

l/F

(Kd-1)

(E - major element; e - trace element; p - primary magma; 1 - liquid; r

- residue; F - fraction of liquid; Kd - crystal/liquid partitioning

coefficient for trace element e).

For the Pilbara compositions it is found that, due to their high

SiO2

abundances, the high-Mg basalt compositions are unlikely to

represent primary magmas as such. Some crustal contamination and/or

secondary addition of silica is implied. Instead of using the HMB

compositions, the model primary magma composition listed in Table 5

has been applied, the derivation of F follows Allegre et al.'s

- 23 -

(1977) procedure:

C i = FC i'. F = C i /C i

p^l^P 1where Kdi tm nil.

— (3)

Using an incompatible (i) element such as Zr, and taking the abundance

of this component in high-Mg basalts as approximating that of the

primary magma, F values derived by equation 3 were applied. The

results of such calculations confirm the role of Cpx, Opx, Plg, and in

some cases iron oxides, in the fractional crystallization processes

that produced the observed Qz-tholeiite compositions.

Fractionation of Cpx and Plg, as supported above, when combined

with source heterogeneities, are capable of accounting for some of the

RE and HFS element characteristics of the tholeiitic basalts.

Fractional crystallization of Cpx would elevate the Ce/Sm ratios (Fig.

5a). Precipitation of Mg-rich diopside can explain the low Mg' value

and Ca/A1 ratios of the tholeiites. Separation of Plg may account for

some of the negative Eu anomalies shown by the basalts, although a

depletion of relatively mobile Eu due to alteration is more likely.

Fractionation of feldspar is consistent with the preceding model

primary magma calculations, indicating an excess of CaO and Al 20 3

relative to the HMB; however, significant fractionation of plagioclase

^

Pla^Plawould decrease the Ce/Sm ratios, since Kd ->Kd - (Irving, 1978), and

^

Ce^Sm

is therefore unlikely.

- 24 -

VI . CONCLUSIONS AND TECTONIC IMPLICATIONS

Rare earth (RE) element and high field strength (HFS) element data

for Pilbara tholeiitic basalts and high-Mg basalts reveal secular

changes in the composition of mantle source regions from which primary

magmas were derived. These variations reflect mantle heterogeneities

and fractionation processes dominated by clinopyroxene and plagioclase,

resulting in departure of RE and HFS element ratios from chondritic

ratios. Typical trace element characteristics of the various volcanic

units throughout the 3.7-2.7 b.y. old geological column of the Pilbara

Block may be summarized as follows:

(1) Several of the mafic-ultramafic volcanic units display enrichment

in the light RE relative to the intermediate RE, (relative to

chondrites) and of intermediate RE relative to the heavy RE.

(Ce/Sm)N are moderate for the @ 3.7-3.4 b.y. lower Warrawoona

Group (0.9-1.6), chondritic to slightly above chondritic for the @

3.4-3.0 b.y. old upper Warrawoona Group, Gorge Creek Group and

Warambie Basalt, and high (2.2-3.1) for most of the Louden

Volcanics, Negri Volcanics and Fortescue Group basalts.

Intermediate to heavy RE ratios vary from (Sm/Yb)N = 1.0-2.0 for

Warrawoona Group basalts to 1.4-2.9 for upper Whim Creek Group and

Fortescue Group basalts.

(2) RE element fractionation is positively related to total RE and

to SiO 2 and negatively to Mg' value. Total RE are at a minimum

from the Euro Basalt to the Warambie Basalt and increase

markedly in the upper Whim Creek Group and Fortescue Group.

Some of the high-Mg basalts associated with the tholeiites have

— 25 —

analogous RE characteristics.

(3) RE elements correlate positively with Ti, Zr and P in some

units, suggesting residence in sphene, zircon and apatite. The

rocks have high Ce/Zr ratios relative to chondrites. Among the

HFS elements enrichment sequences relative to chondrites show

that Zr and Nb are the commonly most enriched component, with Ti

the next most enriched in the lower Warrawoona Group and P the

next most enriched in younger volcanic units. Ti is relatively

depleted among the HFS elements in the Fortescue Group.

(4) The older Warrawoona Group and the younger Whim Creek Group-

Fortescue group section are separated by a section containing

basaltic units that are RE-depleted and/or little RE-

fractionated, i.e. the upper part of the Warrawoona Group, Gorge

Creek Group and Warambie Basalt.

On the whole, the mafic-ultramafic rocks of the Pilbara Block

are significantly more fractionated with regard to the RE elements,

i.e. have higher (Ce/Yb)N, as compared to the late Archaean basalts

of the central and eastern Yilgarn Block (Sun and Nesbitt, 1978).

Important similarities exists between RE characteristics of the

Warrawoona Group are and the contemporaneous (3.6-3.3 b.y.)

Onverwacht Group, eastern Transvaal (Jahn et al., 1982; Glikson and

Jahn, 1985). The ca. 2.7.b.y. Fortescue Group basalts have

significantly higher total RE and HFS elements and higher (Ce/Yb)N

than the contemporaneous Yilgarn greenstones, pointing to lateral

mantle heterogeneity in the late Archaean.

— 26 —

RE patterns of the Warrawoona Group are consistent with partial

melting of chondritic to light RE-enriched garnet lherzolite sources.

In the case of the upper Warrawoona Group dynamic remelting of depleted

mantle is possible. Some rocks of the Gorge Creek Group may have been

derived from light RE depleted sources mantle. The strongly RE

fractionated basalts of the Upper part of the Whim Creek Group (Louden

Volcanics and Negri Volcanics) and the Fortescue Group have high (Ce)N

and (Ce/Yb)N, similar to alkali basalts (Fig. 6) and are consistent

with partial melting of chondritic mantle source including over 30%

light RE-enriched fraction. The marked departures of RE and HFS

element ratios from chondritic ratios shown by tholeiitic basalts

mainly reflect intra-mantle heterogeneities and crystal fractionation,

with limited crustal contamination, a conclusion supported by

departures of RE and HFS elements ratios of HMB from chondritic ratios.

An approximate correlation between the high-Mg basalts and model

parental magma of Qz tholeiites is possible only if significant

fractional crystallization of Cpx and some Plg, as well as 01, has

occurred, as also supported by relatively low Ni and Cr in the basalts.

(Glikson and Hickman, 1981a, b).

If RE and HFS element enrichment of the lithosphere is a

progressive time-dependent process, the above variations have

implications to the pre-history of mantle sources of basalts. The RE

and HFS element data of Pilbara mafic-ultramafic volcanics define

temporal changes in the composition of underlying source mantle

regions. Major changes appear to have occurred upon the onset of the

upper Warrawoona Group (Ca 3.4 b.y.) and also between the Warambie

Basalt and Louden Volcanics (Ca 3.0 b.y.). During the first phase

7. 27—

(lower Warrawoona Group) mantle sources relatively enriched in light

RE, Zr, Nb and Ti relative to chondrites were tapped, producing high-Mg

primary magmas and their derivative tholeiites. TB of this stage have

low MgO ( 6.5%) and Ni (75 ppm). During the second phase (Upper

Warrawoona Group, Gorge Creek Group, Warambie Basalt) partial melting

affected chondritic to only slightly light RE-enriched mantle sources.

TB of this phase have high MgO ( 7.5-8.0%) and Ni( 140 ppm). High

Ni/Mg ratios, diagnostic of high-T melting (due to lower K41 1), are

typical of this stage (Glikson and Hickman, 1981a). This phase is

associated with major high-degree fusion events producing peridotitic

magmas such as abound in the Apex Basalt (Glikson and Hickman, 1981a).

This type of mantle activity bears close analogies with the late

Archaean mantle underlying the central and eastern Yilgarn Block (Sun

and Nesbitt, 1978). During the third phase (Louden Volcanics, Negri

Volcanics, Fortescue Group) magma sources were strongly enriched in

light RE, Zr, Nb and P relative to chondrites. TB of this stage tend to

have low MgO ( 4-6%) and Ni (40-60 ppm), and very high Zr ( 100-400

ppm). Crustal contamination may have been relatively important at this

stage.

In so far as periods of catastrophic mantle melting, possibly

associated with vigorous convection and diapiric rise (Green, 1975;

Glikson, 1983), triggered tectonic instability, the geochemical data

underline important distinctions between mantle evolution patterns of

the three stages. During the second phase, rather poorly constrained

between @ 3.4 Gyr and @ 3.0 Gyr (deLaeter et al., 1981; Hickman, 1983),

major magmatic and tectonic events included: (1) emplacement of

granitic batholiths; (2) uplift and erosion of batholiths; (3)

development of rift structures at interbatholith positions where

— 28 —

clastic sediments of the Gorge Creek Group were deposited; (4) major

volcanic episodes, including mafic-ultramafic volcanism (? pre-rifting)

of the upper Warrawoona Group, Gorge Creek Group and the Warambie

Basalt. The intense tectonic activity during the second phase

contrasts with relative tectonic stability during the first phase and

the third phase (Hickman, 1983; Grove and Batt, 1984). During the

third phase intrasialic plateau volcanism of the Fortescue Group @ 2.7

b.y. ago tapped light RE and HFS element-enriched mantle sources,

suggesting advanced geochemical fractionation of the lithosphere at

this stage. These geochemical variations may reflect an evolution from

(1) a stable environment overlying a weakly fractionated lithosphere,

through (2) a rifting phase associated with partial melting of depleted

mantle, widespread crustal anatexis and formation of batholiths, to (3)

ensialic continental-type environment of the Fortescue Group, overlying

fractionated lithosphere. Significantly, the breaks between the three

phases were marked by peaks of felsic igneous activity, represented by

the ca 3.4-3.5 b.y. old trondhjemite-granodiorite-dacite association

and by the ca 2.9-3.1 b.y. post-tectonic granites and Mons Cupri

Volcanics (Jahn et al., 1981; Hickman, 1983; Blake and McNaughton,

1984).

Acknowledgements

We wish to thank S. Sun and W. Johnson for reviewing the

manuscript. This report is published with the permission of the

Director, Bureau of Mineral Resources, Geology and Geophysics and the

Director, Geological Survey of Western Australia.

— 29 —

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— 34 —

HANSON, G.N., 1980 - Rare earth elements in etrogenetic

studies of igneous systems.^Annual Review Earth

Planetary Science, 8, 371-406.

HART, S.R., 1971 - K, Rb, Cs, Sr and Ba contents and Sr

isotope ratios of ocean floor basalts.^Philosophical

Transactions Royal Society London, A268, 573-587.

HAWKESWORTH, C.J. & O'NION, R.K., 1977 - The petrogenesis of

some Archaean volcanic rocks from southern Africa. •

Journal of Petrology, 18, 487-520.

HERMANN, A.G., BLANCHARD, D.P., HASKIN, L.A., JACOBS, J.W.,

KNAKE, D., KOROTEV, R.L. & BRANNON, J.C., 1976 - Major,

minor and trace elements compositions of peridotitic

and basaltic komatiites from the Precambrian crust of

southern Africa.^Contributions to Mineralogy and

Petrology, 59, 1-12.

HICKEY, R.L. & FREY, F.A., 1982 - Geochemical

characteristics of boninite series volcanics:

implications for their source.^Geochimica et

Cosmochimic Acta, 46, 2099-2115.

HICKMAN, A.H., 1983 - Geology of the Pilbara Block and

Environs.^Geological Survey of Western Australia

Bulletin, 127.

HUMPHRIES, H.E. & THOMSON, G., 1978 - Trace element mobility

during hydrothermal alteration of oceanic basalts.

Geochimica et Cosmochimica Acta, 42, 127-136.

HUPPERT, H.E. & SPARKS, S.J., 1985 — Cooling and contamination of mafic

and ultramafic magmas during ascent through continental crust.

Earth Planetary Science Letters, 74, 371-389.

— 35 —

IRVING, A.J., 1978 - A review of experimental studies of

crystal/liquid trace element partitioning.^Geochimica

et Cosmochimica Acta, 42, 743-770.

JACOBS, J.W., KOROTEV, R.L., BLANCHARD, D.P. & HASKIN, L.A. 1977 -

A well tested procedure for instrumental neutron activation

analysis of silicate rocks and minerals.^Journal

Radioanalytical Chemistry, 40, 93-114.

JAHN, B., VIDAL, P. & TILTON, G., 1980 - Archaean mantle

heterogeneity, evidence from chemical and isotopic

abundances in Archaean igneous rocks.^Philosophical

Transactions Royal Society London, A297, 353-364.

JAHN, B., GLIKSON, A.Y., PEUCAT, J.J. & HICKMAN, A.H., 1981 -

REE geochemistry and geochronology of Archaean silicic

volcanics and granitoids from the Pilbara Block, Western

Australia.^Geochimica et Cosmochimica Acta, 45, 1633-1652.

JAHN, B., GRUAU, G. & GLIKSON, A.Y., 1982 - Komatiites of

the Onverwacht Group, South Africa:^REE geochemistry,

Sm/Nd age and mantle evolution.^Contributions to Mineralogy

and Petrology, 80, 25-40.

LeROEX, A.P., ERLANK, A.J. & NEEDHAM, H.D., 1981 -

Geochemical and mineralogical evidence for the

occurrence of at least three distinct magma types in

the FAMOUS region.^Contributions to Mineralogy and

Petrology, 77, 24-37.

LUGMAIR, G.W., & MARTI, K., 1977 - Sm-Nd-Pu time pieces in

the Angra dos Reis meteorite.^Earth and Planetary

— 36 —

Science Letters, 35, 273-284.

McCULLOCH, M.T. & COMPSTON, W., 1981 - Sm-Nd ages of Kambalda and

0Kanowna greenstones and heteveneity in the Archaean mantle.

Nature, 294, 322-327.

NESBITT, R.W. & SUN, S., 1976 - Geochemistry of Archaean

spinifex-textured peridotites and magnesian and low-

magnesian tholeiites.Êarth and Planetary Science

Letters, 31, 433-453.

NESBITT, R.W., & SUN, S., 1980 - Geochemical features of some

Archaean and post-Archaean magnesian low-alkali

liquids.^Philosophical Transactions Royal Society

London , A297, 365-381.

NICHOLLS, I.A. & RINGWOOD, A.E., 1972 - Production of

silica-saturated tholeiitic magmas in island arcs.Êarth

and Planetary Science Letters, 17, 243-246.

NORRISH, K. & CHAPPELL, B., 1967 - X-ray fluorescence

spectrography.În:^ZUSSMANN, J. (editor), Physical Methods

in Determinative Mineralogy.Âcademic Press, London, 161-214.

NORRISH, K. & HUTTON, J.J., 1969 - An accurate X-ray

spectrographic method for the analysis of a wide range

of geological samples.^Geochimica et Cosmochimica

Acta, 33, 431-453.

PEARCE, J.A., 1975 - Basalt geochemistry used to investigate

past tectonic environments on Cyprus.^Tectonophysics,

25, 41-67.

— 37 —

PEARCE, J.A. & CANN, J.R., 1973 - Tectonic setting of basic

volcanic rocks determined using trace element analyses.

Earth and Planetary Science Letters, 19, 290-300.

PEARCE, T.H., GORMAN, B.E. & BIRKETT, T.C., 1977 - The

relationships between major element chemistry and

tectonic environment of basic and intermediate volcanic

rocks.Êarth and Planetary Science Letters, 36, 121-

132.

PEARCE, J.A. & NORRY, M.J., 1979 - Petrogenetic implications

of Ti, Zr, Y, and Nb variations in volcanic rocks.


ROEDER, P.L. & EMSLIE, R.F., 1970- Olivine-liquid

equilibrium.^Contributions to Mineralogy and

Petrology, 29, 275-289.

SCHILLING, J.G., BERGERSON, M.B. & EVANS, R., 1980 - Halogens

in the mantle beneath the north Atlantic.

Philosophical Transactions Royal Society London, A297,

147-178.

SHERATON, J.W. & LABONNE, B., 1978 - Petrology and

geochemistry of acid igneous rocks of northeast

Queensland.Âustralian Bureau of Mineral Resources

Bulletin, 159.

SMITH, R.E. & SMITH, S.E., 1976 - Comments on the use of Ti,

Zr, Y, Sr, K, P and Nb in classification of basaltic

magmas.Êarth Planetary Science Letters, 32, 114-120.

— 38 —

STAUDIGEL, H. & HART, S.R., 1983 - Alteration of basaltic

glass : mechanism and significance for the oceanic crust-

sea-floor budget.^Geochimica et Cosmochimica Acta, 47, 337-350.

SUN, S., 1980 - Lead isotopic study of young volcanic rocks

from mid-ocean ridges, ocean islands and island areas.

Philophical Transactions Royal Society London , A297, 409-446.

SUN, S., 1092 - Chemical composition and origin of the

Earth's primitive mantle.^Geochimica et Cosmochimica

Acta, 46, 179-192.

SUN, S., 1984 - Geochemical characteristics of Archaean

ultramafic and mafic volcanic rocks : implications for

mantle composition and evolution.În:^KRONER, K., HANSON,

G.N. & GOODWIN, A.M. (editors), Archaean Geochemistry.

Springer Verlag, Berlin, 25-46.

SUN, S. & HANSON, G.N., 1975 - Origin of Ross Island

basanitoids and limitations on the heterogeneity of

mantle sources for alkali basalts and nephelinites.


SUN, S., NESBITT, R.W. & SHARASKIN, A.Y., 1979 - Chemical

characteristics of mid-ocean ridge basalts.Êarth and

Planetary Science Letters, 44, 119-138.

SUN, S. & NESBITT, R.W., 1977 - Chemical heterogeneity of

the Archaean mantle : composition of the Earth and

mantle evolution.Êarth and Planetary Science Letters,

35, 429-448.

— 39 —

SUN, S. & NESBITT, R.W., 1978 - Petrogenesis of Archaean

ultrabasic and basic volcanics:^evidence from rare

earth elements.^Contributions to Mineralogy and

Petrology, 65, 301-325.

TARNEY, J., WOOD, D.A., SAUNDERS, A.D., CANN, J.R. & VARET,

J., 1980 - Nature of mantle heterogeneity in the North

Atlantic : evidence from deep sea drilling.

Philosophical Transactions Royal Society London , A297,

179-202.

WEAVER, B.L. & TARNEY, J., 1981 - The Scourie dyke suite

Petrogenesis and geochemical nature of the Proterozoic

subcontinental mantle.^Contributions to Mineralogy and

Petrology, 78, 175-188.

WOOD, D.A., TARNEY, J., VARET, J., SAUNDERS, A.D., BOUGAULT,

H., JERON, J.L., TREUIL, M. & CANN. J.R., 1979 -

Geochemistry of basalts drilled in the north Atlantic by

IPOD Log 49 : implications for mantle heterogeneity.

Earth and Planetary Science Letters, 42, 77-79.

TABLE 1 - UNIT-ROCK TYPE CLASSIFTCATION OF RE ELEMENT ANALYSES*

APPROXIMATEAGE (b.y.) **

PK^HMB^TB^TD TA DACITE RHYOLITh SILICIFIEDLAYA

FORDESCUEMaddina Basalt (MB)^ 2 2 4Nymerina Basalt (NB)^1^3 - 4Kylena Basalt (KB)^ 3 1 4

2.75^ Mt Roe Basalt (MRB)^ 3 2 5

WHIM CREEK GROUPLouden Volcanics (LV)^ 1 2 3Negri Volcanics (NV)^3^2 1 6Mons Cupri Fragmentals (MCF)^-Mt Brown Rhyolite (MBR)^-

3.0^ WaraMbie Basalt (WE)^ 1^2 3

GCMGE CRF3EK GROUPHoneyeater Basalt (MB)^1^2^1 4Charteris Basalt (CB)^2^3 5

WAREAWOONA GROUP3.2^ It7man Formation (14TE)^ -

Euro Basalt (EB)^ 3 33.34^)^ ( Panorama Formation (PF)^-

3.2^) ( Apex Basalt (AB)^1^1 23.45^ Duffer Formation (DF)^ -^3 1 5 2 113.6^ Mt Ada Basalt (MAB)^ 4 43.7^ North Star

Basalt (NSB)^1^3^6 2 2 14

1^11^34^6 11 9 10 3 72

PK^-^peridotitic komatiite (MgO^20%)HMB -^high-Mg basalt (Mg0 > 8%;^MgO/A1,0„> 0.6)TB^tholeiitic basalt^(MgO 4 8%;^Mg(0/Al203 < 0.6)TD^-^tholeiitic doleriteTA^tholeiitic andesite and silicified basalt (Si0 2 55%)

Including felsic - intermediate volcanic samples,to be discussed elsewhere (Glikson et al., in prep.)

** For compilation of isotopic ages refer to Hickman (1983)and Blake and McNaughton (1984). The Ca 3.7 b.y. and3.6 b.y. ages for the NSB and NAB, respectively, are Sm-14disochron ages (B. Jahn, in prep.).

TABLE 2

RE AND HFS ELEMENTS RANGES OF THOLEIITIC BASALTS,DOLERPIES AND ANDESITES

ACCORDING TO VOLCANIC UNITS

tREE* (Ce/Yb)N (Ce/Sm)N (Sm/Yb)N TiO2% ut

P05at

ZrRan

Nbprin Pint

North Star Basalt (NSB) 6 30-80 1.0-3.0 0.9-1.6 1.0-2.0 0.58-2.31 0.03-0.23 77-210 2-9 19-39

Mt Ada Basalt (MAB) 4 20-70 1.8-2.7 1.2-1.5 1.4-1.9 0.79-2.05 0.06-0.21 61-171 3-9 14-29

Duffer Fm dolerites (DF) 3 30-55 1.3-1.7 1.1-1.3 1.1-1.3 1.33-2.18 0.08-0.18 83-144 3-6 26-35

Apex Basalt (AB) 1 30 2.3 1.2 1.9 0.99 0.12 62 2 19

Euro Basalt (EB) 3 17-40 1.0-2.0 0.9-1.1 1.0-1.8 1.03-1.67 0.10-0.17 22-26 0-4 22-26

Charteris Basalt (CB) 3 15-17 1.0-1.9 1.3-1.6 1.2-1.3 0.51-0.75 0.05-0.06 29-33 N.D. 9-12

Honeyeater Basalt (MB) 3 27-32 1.1-1.4 1.1 1.0-1.2 0.31-1.01 0.04-0.14 14-103 3-4 10-31

Warambie Basalt (WB)** 2 20 1.6 1.0 1.4-1.7 1.19-1.21 0.14-0.18 49-124 0-8 17-18

Louden Volcanics (LV) 3 35-55 3.4-4.0 2.2-2.5 1.4-2.3 0.44-0.90 0.05-0.10 73-129 2-4 13-18

Negri Volcanics (NV) 3 60-65 5.8-6.3 2.2 2.6-2.9 0.91-1.04 0.09-0.12 128-136 5 18

Mt Roe Basalt (MRB) 5 54-67 4.8-5.6 2.0-2.2 2.4-2.6 0.66-1.13 0.09-0.17 123-154 4-5 20-27

Kylena Basalt (KB) 4 80-160 5.2-6.0 2.7-3.1 1.7-2.0 0.65-1.38 0.15-0.33 185-393 20-23 25-47

Nymerina Basalt (NB) 3 70-115 4.0-6.1 2.1-2.4 1.7-2.8 0.95-1.22 0.14-0.15 171-210 7-10 26-29

Maddina Basalt (MB) 4 75-100 3.8-4.8 2.3-2.7 1.5-1.8 0.68-1.03 0.08-0.14 151-211 7-11 29-36

Ce, Nd, Sm, Eu, Tb, Yb, Lu** excluding a highly carbonated sample

-p-

TABLE3

SUNIKARY OF HFS ELEMENT RATIOS IN THOLEIITIC BASALTS RELATION

TO PRIMITIVE MANTLE, ACCORDING TO VOLCANIC UNITS

Ti/Zr Ti/Y Ti02/P205 P/Zr Zr/Ce Zr/Y Zr/Nb

PRIMITIVE 118 280 10 2.4 15MANTLE*

LWG - V+ + ++ - + +

(AB V V V ++ - V +UWG (

(EB V + V ++ + + +

(CB V + V + V V +GCG (

(HB - _ - ++ V + ++

WE V + V ++ V + V

LV, NG V+ V + - ++ ++

FG + - + +

LWG - Lower Warrawoona Group

UWG - Upper Warrawoona group

GCG^Gorge Creek Group

FG^Forte scue Group

for other unit abbreviations, see Table 1

Value after Sun (1982)

++ very high; + high; V - similar to primitive mantle; V+ -similar to high; - low;very low.

- 43 -TABLE 4

HIGH IONIC POTENTIAL ELEMENT (Ti, Zn, Nb, Y, P)

AND RE ELEMENT RATIOS IN HIGH-MG BASALTS

Ti/Zr Ti/Y Ti02/P205 Zr/Y Zr/Nb Y/Yb (Ce/Yb)N (Ce/Sm)N (Sm/Yb)N

Chondritic 118 280 10 2.4 15 10 1.0 1.0 1.0

NSB 75040024C 45 177 18.6 3.9 18.5 9.1 1.45 1.30 1.04

NSB 75040025D 25 183 17.3 7.3 41.6 8.7 1.36 1.34 1.00

NSB 45075 44 245 12.2 5.6 16.7 6.6 2.03 1.76 1.15

AB 49336 105 255 8.5 2.4 8.4 0.62 0.65 0.94

CB 49271 120 270 9.0 2.3 10.2 1.19 1.08 1.09

CB 49275 114 281 12.2 2.5 9.1 1.26 1.14 1.09

HB 49385 114 270 9.0 2.3 9.4 1.18 1.40 0.83

NV 331/337 9.7 3.16 2.52 1.23

NV 331/338 52 192 10.7 3.7 3.79 2.88 1.30

NV 331/339 19.5 3.72 2.67 1.37

AverageOnverwacht HMB34 Samples 48 330 12 7.2 13.5

AverageYilgarn HMB76 Samples 76 189 10 2.5 23

Nymerina Basalt68941 59 376 6 6.3 23.3

68942 67.8 362 7.5 5.3 21.4

68943 68.3 365 8.1 5.3 21.4

68944 68.4 329 8.0 4.8 17.6

* * * * * * * * * * *

— 44 —

TABLE 5

(1)Model mantle composition (major elements - pyrolite,

Ringwood (1975); trace elements X2 chondrite, after Sun

(1982), Anders and Ehibara (1982), Nakamura (1974) and

Evensen et al. (1978));

(2)Model primary magma derived by 30% melting of pyrolite,

leaving a residue of OL (Fo90) and aluminous Opx at a

ratio of 3:1.

Pyrolite Model Primary Magma

Si 0 2 46.1 49.55

Al203

4.3 12.00

FeOt 8.2 11.80

MgO 37.6 13.98

Ca0 3.1 10.33

Na20 0.4 1.33

K20 0.03 0.10

Ti ppm

(X2 chondrite) Model Primary Magma

1200 3658

Zr 10.2 33

4.28 12.6

Nb 0.68 2.05

Ce 1.73 5.75

Pr 0.512

Nd 1.26

Sm 0.406 1.34

Eu 0.154

Gd 0.552

Tb 0.0996

Dy 0.686

Ho 0.1508

Er 0.45

Tm 0.068

Yb 0.44 1.42

Lu 0.0678

* * * ** * * * * *

— 45 —

CAPTIONS

1. Geological sketch map of the Pilbara Block, Western Australia,

showing sample localities from which RE-analysed rocks were

derived.^Numbers indicated are the two last digits of sample

numbers given in Appendix I.

2. Normative 01-Opx-Cpx-Qz plots of Pilbara data. Solid circle -

average of 155 mid-ocean ridge basalts (Brian et al., 1976);

Inverted triangle-NOR olivine basalt, FAMOUS area (DR4-303)

(Le Roux et al., 1981);^MP-MOR picrite, FAMOUS area (10-03C)

(Le Roux et al., 1981);^HP-Hawaiian picrite (Gunn, 1971);

GPK-Gorgona Island peridotitic komatiite (Echeverria, 1980).

S-Scourie dolerite L636 (Weaver and Tarney, 1981).^P-Model

pyrolite (Ringwood, 1975);^H-Model primary magma (Table 5).

Legend of symbols attached.

3. Normalized rare earth element pattern of Pilbara basalts

compared to model pattern reference frames (normalizing

primitive mantle values from Sun (1982)).^Sample numbers

are marked to the left end of the curves and Mg' values

(100 MgO/Mg0+Fe0) mol% to the right.^Model partial

melting fields A and B are specified within the figures

according to model source composition, nature and

proportion of residual phases and fraction of melting (F),

as discussed in the text.^Data plotted in Fig. 3a are by

B. Jahn (IDMS), in Fig. 3k by Sun and Nesbitt (1978)

(IDMS), and in all the other figures by C. Pride (INAA).

— 46 —

4. (Ce/Yb)N - total RE plots.^Symbols as for Fig. 2.

Y - Yilgarn greenstones (Sun and Nesbitt, 1978);^S

Scourian dolerites (Weaver and Tarney, 1981);^M -

Midocean Ridge Basalts (Wood et al 1979;^Sun et al 1979);

B - Boninites (Hickey and Frey, 1982);^N - Onverwacht

Group (Jahn et al., 1982;^Hermann et al., 1976;

Hawkesworth and O'Nions 1977).

5. (a) (Ce)N - (Sm)N plots.^Symbols as for Figs. 2 and 4.

Circled stars:^D - depleted midocean ridge basalt;Ê

- enriched midocean ridge basalt;ÔI ocean island

basalt;Â - arc-trench basalt;^C - high Al calc

alkali basalt (Sun, 1980);^S - Scourian dolerite

(Weaver and Tarney, 1981);^P (solid circle) - model

pyrolite (Ringwood 1975);^H (open circle) - model

primary basalt (Table 5). Arrows represent trends of

liquid evolution by fractionation of indicated phases

from the model primary magma (ol - olivine; op -

orthopyroxene;^cp - clinopyroxene;^hb - hornblende;

pl - plagioclase;^gt - garnet;^ph - phlogopite).

Arrow heads are placed at 50% crystal fractionation.

(b) (Sm)N-(Yb)N plots.^Symbols as for Figs. 2 and 5.

(c) (Sm)N-(Nd)N plots.^Symbols as for Figs. 2 and 5.

6. Log (Ce/Yb)N - log (Ce)N plots.^Symbols as for Fig. 2 and

5. The data are compared with magmatic fractionation

trends calculated by Tarney et al (1980), as follows:

A.Êquilibrium batch melting of garnet lherzolite source

(S i : RE = 2x chondritic) (55% 01, 23% Opx, 15% Cpx, 5%

— 47 —

Gt), with a melting mode of 10%, 20%, 40%, 30%

respectively;^numbers on curve are % melting.

B. Equilibrium batch melting of lherzolite (S 2 -LRE-

depleted source of 50% 01, 25% Opx, 25% Cpx) with a

melting mode of 15%, 35%, 50% respectively.^Numbers

on curve are % melting.

C. Continuous melting of mantle residue left after 10%

melting of source S 2 with 2% melt retained in the

residue.^Numbers represent successive 2% melting

increments, with 2% melt always retained in the

source.

D. Closed system low pressure crystal fractionation of

basalt-rhyolite series from eastern Iceland, using Kd

values from Arth and Hanson (1975).^Numbers are

percent crystal fractionation.

E. Low-pressure open system crystal fractionation

involving continuous magma replenishment to the

chamber, fractionation of 27.5% 01, 22.5% Cpx and 50%

Pig. F (liquid fraction) = 0.99.^Initial MORB magma

of (Ce/Yb)N = 1.^Numbers marked on the curve

represent the ratio of X (X=T-F) to Y (Y=fraction of

liquid erupted from the magma chamber).

F.^High-pressure open system crystal fractionation

involving eclogite (86% Cpx, 14% Gt) separation.

Numbers marked on curve are as for E.^Initial liquid

is derived by 30% partial melting of garnet lherzolite

(RE- chondritic mantle).

— 48 —

G. Zone refining enrichment of magma produced by 30%

batch melting of mantle source S 2 and re-equilibration

with the volumes of S 2' the parameters being marked

along the curve.

H. Zone refining enrichment of LRE depleted MORB re-

equilibrated with the volumes of garnet lherzolite,

being marked along the curve.

^

Ml.^Mixing curve between X2 RE-enriched chondritic mantle

source (S 1 ) and undersaturated olivine melilite

liquid.^Numbers represent percentage of metasomatized

LREE-rich component in the mantle.

^

M2.^Mixing curve between LRE depleted source (S 3 ) and

ocean floor alkali basalt.

7. (Ce/Yb)N - (Yb)N plots.^Symbols as for Figs. 2, 4 and 5.

8. (Ce/Sm)N - (Sm/Yb)N plots.^Symbols as for Figs. 2, 4 and

5. B - Cape Vogel boninite (Hickey and Frey, 1982).

9. HFS element covariations.^Solid lines:^chondritic ratios

(after Sun, 1982)

(a) Ce-Zr plots

(b) Y-Zr plots

(c) Hf-Zr plots

(d) Zr-Nb plots

(e) Zr-P plots

(f) Zr-Ti plots

(g) Y-Ti plots

(h) P 2 0 5 -Ti0 2 plots

Symbols as for Figs. 2, 4 and 5. DM - depleted midocean

ridge basalt (Sun et al., 1979);^EM - enriched midocean

ridge basalt (Sun et al,^1979);^AT - Arc-trench basalt,

sample 68-72 (Gill, 1970).

10. (Ce/Sm)N - Ti/Zr plots.^Symbols as for Figs. 2 and 5.

11. (Ce/Sm)N - Ti0 2 /P 2 0 5 plots.^Symbols as for Figs. 2 and 5.

12. (a) Al 2 0 3 /Ti0 2 - TiO 2 plots.

(b) CaO/A1203

- TiO2

plots.

(c) CaO/Al 2 0 3 - TiO 2 plots.

Symbols as for Figs. 2, 5 and 9.

1111 Taiga -Taiga Subgroup

Duffer Formation

Salgash Subgroup

George Creek Group

Whim Creek Group

Fortescue Group

/

A L

0^ 100 km1^1^1^1^1

12 °30'116°00'20°15'

22°15'

INDIAN

og421

Granite

Greenstone xenolith-rich zones

V

OCEAN

V 77 7V

^,z7, ,',*,+ + I-

+^/

^+ + ^+

+ ++

7/„/".+ 4-^+^1^+

+ 4+ +

., + + + + + + +^4 + +

+ + ++^4- +^ +^+ + +

7.-)qh, . ++ : ' -11- + : +

+^--z-ziob. +^+

^

Z V V,^+ i + , + 4-+ + , 11'

, - ' 4- + +

'VV., VV +

^

VI 9, 12 7,/,/,/,," + +^+

+ + +

^

.' ^+ + +

+H8 375, 79,

+Fr^/^

+

+1,,/ +Z,,, r ' , „

V/77 , ^+^+ I^

, 85, 98

/,L62:24 V7Z,Z^ ie

'VV,77/^+NI^ 0.--""+ , - + Z_,.,,^+ * -1^

v

+ .7% r .,019v1--,

+ + + .^,,,^ + 4

+ 4- c

'

4 + + + + f + 4 ' ++ + 4-^40"

+ + +^■ + +Z.c.7+ +^4-

+ 4 + + + I + + ' + + + +

+

4 + + + + 4 + + f+ + 4 + 4 + 4 +

+^+^+^■^4-^4-+ + + + 1+ 1 4 + +

+ ++ 4 +

+ +. +^+

+^+ ^4

• : : + + 4-+ +

+ +4 +

f

1 5' -7

+ +

4 ++ + + +

+ ++ + +

+ +

A A

41//fit,+ + +S 62, 64, 68,75, 76,

79 86, 92+

111, 114 117,L 22, 127/130!\1_31,

34, 140,1 1, 14 , 147r /4 A

MRB 931, 47,N51, 52, 63,

CB 250'7 69, 7

4

A

'7

Fig. 1 - Geological sketch map of the northern part of the Pilbara Block, Western Australia, showinglocation of samples collected for REE analyses.

Legend for Figures 2 and 4 - 12

• NORTH STAR BASALT - TB 0 HONEYEATER BASALT - DOLERITE

• NORTH STAR BASALT - HMB 0 HONEYEATER BASALT - HMB

* NORTH STAR BASALT - PK .. WARRAMBIE BASALT

• MOUNT ADA BASALT - TB * NEGRI VOLCANICS - SPINIFEX HMB

• DUFFER FORMATION - DOLERITES III NEGRI VOLCANICS - THOLEIITES

411- APEX BASALT - TB • LOUDEN VOLCANICS

-4-, APEX BASALT - HMB AL Mt ROE BASALT

• EURO BASALT - TB Ir KYLENA BASALT

III CHARTERIS BASALT - TB * NYMERINA BASALT - TB

+ CHARTERIS BASALT - HMB * NYMERINA BASALT - HMB

o HONEYEATER BASALT - TB II MADDINA BASALT

Record 1986/6 01 16/F60/2

52

Qz

Cp Op

53

aNORTH STAR BASALT

1 000

A SOURCE 07.8 [HONOR'S

RESIDUE. 01 3 0.7DPI • 0.3

45052r 45044D. I

I. 450756060^ A

1

1000

1 00

10

40250

492614927149275

49260

1000

Cs Rb Bo Nb La Ce Pr Nd Sm Eu Gd Tb Dv Ho Er Tm Yb Lu 4 .

1000

MOUNT ADA BASALT

SOURCE 64 CHOMP'S

RESIDUE,^01^• 0.7DPI O. 3

1 00

1_^45079 1,6345076 ___ _ ■, 4^6

10211i D' 5

/ ,

Cs Rb Bo Nb La Ce Pr Nd Sm EL, Gd Tb Dy Ho Er Tm Yb Lu

DUFFER FORMAT ION - DOLEIR I TES

7_J

0

0.0

100

1 00 -750400430760409660

75040046.1

0; 5

A^SOUREI 83.5 CHONDRITE

RESIDUE. 01 • 1.0

1000

100

10

Cs Rb Bo Nb La Ce Pr Nd Sm Eu Gd Tb Dy Ho Fr Tm YE, tu N•^ Es Rb Bo Nb La Ce Pr Nd Sm Eu Gd lb O y Ho Fr Tm Yb Lu

Record 1986/6 16/F50/3

Fig.3b APEX BASALT

EURO BASALT

1 000

1000

713

A SOURCE 03.2 CRONDRITERESIDUE, 01^1.0

A

Co fib 8a Nb La Ce Pr Nd Sm Eu Gd lb Oy Ho Er Tm Yb Lu

UI

> 000

0UI^. 40344^0,0

- 49347

1 0O.

40340

0

0

> 1 00

0

1 0

0

A^SOURCE 02.7 CH0600I1E

RESIDUE, DI • 1.0

40336

40325

CHARTER'S BASALT HONE 1/1 61 A TER BASALT

Cs Rb Bo N6 La Ce Pr Nd Sm Eu Gd lb By Ho Er To Yb Lu N.

WARAMBIE BASALT

A^SOURCE 62.3 CHONEIRIIERESIDUE: 01. 0.7

OPX • 0.3

800402688004027080040273

Cs Rb 8a Nb La Ce Pr Nd Sm Eu Gd lb By Ho Er TM Yb Lu

Record 1986/6

Cs Rb Ba Nb La Ce Pr Nd Sm Eu Gd lb Dy Ho Er TM Yb Lu 43

16/F50/4

NEGRO BASALTIc

54.

Fig. 3c_ LOUDEN VOLCAN 1 CS

B SOURCE 82.5 CHONORI 1ERESIDUE, 01 • 0.60, OK • 0.18

CP6 • 11. 14, GNI • 0.08

A^SOURCE 82.5 CHONORITERESIDUE, DI • 0.7

CPx • 0.3

Cs R6 Bo Nb Lo Ce Pr Nd Sm Eu Gd Tb Dy Ho Er 6 Yb Lu N.

MOUNT ROE BASALT

Cs Rb 8a Nb Lo Ce Prr. Nd Sm Eu Gd Tb Dy Ho Err. Tm Yb Lu^s9

YLENA BASALT

8 SOURCE xa CHONDRI TE^4 SOURCE 44 (Harm lc

^

RESIOuE, 01 • 0. 6; OPx • O. IX^RESIDUE 01 • 0.5

^

CPx • 0.14, CaCr • . 08^OPX • 0. 3: CPX • O. 19' 66963^ 0711 • .01

1 000

1 00 r 68952 .025

E 69631

- 68RSI_ 68947

10

..........^I^,^■

Cs Rb Ba Nb La Ce Prr. Nd Sm Eu Gd lb By Ho Err. Tm Yb Lu^N . Cs Rb Ba Nb La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Im Yb Lu

Cs Rb Bo Nb La Ce Pr Nd Sm Ey Gd Tb Dy Ho Er Tm Yb Ty Ili

Record 1986/6

Cs Rb Bo Nb La Co Pr Nd Sr. Eu Cd lb Dy Ho Er Tm Yb Lo

16/150/5

1000

100

10

NYMERINA BASALT

P^B SOURCE 65.5 CH060617ERESIDUE, DI • O. 6, OPX • 0. 18

CPX • 0.14: 087 • 0.08

A - SOURCE 85.5 CHONDRITERESIDUE: 01 . 0.5

OPx . 0.3(PR • O. i9GNI • 0.01

1000

MACIO INA BASALT

10

1000

000

- SOURCE X6 [HONOR! ITRESIDUE: 01 • 0.6OPX • 0.181 CPX = 0.14

GNI • 0.06

40SO50St

00 0 0

100

10

- SOURCE 00.2 0606001 66RESIDUE: 01 - 0.0OPX • 0. is CPX • 0.14

GNI • 0.08

A^SOURCE 00.2 CHONORI TERESIDUE: 01 • 0.6OPX • 0.3CPX • 0.05GNI • 0.05

47 -

-

- 60134011760646114

- 80046111 .

A^ 44

44;

52

8 - SOURCE 010 CRONDRITERESIDUE: 01 = 0.6OPX • 0.181 CPX^0.14GNI • 0.08

A SOURCE X10 CHONORITERESIDUE, 01 • 1550P8 • 0. 31 CPX • 0.190141 • 0.01

•

***

A" •

•

,,^,.._^ •^,^—IP^\ \ - - - -* -**:^ S^\\• , ^ ■

„^,

^

,^ \* ,--_, , -- •-- „ , - -^•^110. I- --,--- ,^,^' I^ ----_--------4-' ,/ _.\....\,'"'^„''I^----111---•^-'^ ---411--4, w ,...21. .....,..--'^L----

---*--A- -.-,'D a* 411Ir ... \-1 ,,13----.64t * '+0 1I

vy•

Fig.4

55

10

9

7

6

5

4

3

2

1

20^

40^60^80^100^

120^

140^

160REEEt0tQ1J PPM

Record 1986/6^ 16/ F60/6

10 20

m [N]30 40

Record 1986/6 18/F50/7

Fig.5a

120

110

100

90

80

70

LJ

r-1

60

50

40

30

20

10

56

40

30

ii

" 20

10

Fig. 5b

57

10^

20^

30Yb [N]

Record 1986/6^1 6 / F50/8

Fig. 5c

40

30

10

10 70605020 30^40

Nd [N]Record 1986/6 16/F80/9

- S2^.^

10^-

_

_^41:- --.-,‘' -------- . .4.- - - ...:4 " "^G ..._._ 1-. - ' . 7,- 20^- -- .-^ e •^—

- 0--

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_^/ '^

• - "...•76 / .1 5 i

•.7*. 2 ----

S2. ------------ .., _ .../.. 1r0

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•:-.-•-•

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./.^.^/^.

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08-- _m_Bor P_ _ 76 :

„ 5^,..!--..7/^ )ó...x^...„^,^_

^

.,.^di5t,- ®

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.,. ,•••• 10^ ris,* ® _

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/ r

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A

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.

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,,,, :e•^Ho./' 50

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_

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59

Fig. 6

10

10Ce EN:

100

Record 1986/6 18/F50/10

OI0

e ®_

c-1

41E..0^,----*-- m_

ie.** /I1

• /^ I*î"1

_• I..-/ •

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• *., / ,fr•B^'^' -IF '1^ >^1

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IÎÎÎÎÎÎÎ

•

0

IÎÎ

Fig-710

9

7

3

2

1

10^

20^

30yb, [N]

Record 1986/6^ 16/F50/71

VV •

\

• • cpC \\^•

\

^. ^1^•‘....ob^11'1 iwittcp‘ ,^ -IF 1

1

^

t^,,,,,,, is, 0^„^#4,...1/w ^111•

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4. 0

3. 0

2. 0

1. 0

Fig.8

to '

1_U^ 2.0^

3. 0

[Sm/Yb] NRecord 1986/6^

16/F50/ 12

tC6I -7

Cbs

liFy _7-7 •

120

110

100

90

80

70

60

50

_ Y-3.72+ 0.31X r= 0.94

- 90

7,7

69

^40^ **40 -'.1)/4(1.^30^ ,

6^,730 -

^20^s-20-Ê ' • a„-*

ii02,V171-'^•B *---.' D II •

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^„..-AA.-^■Îi^,Î^1^ IÎ^.^ 1Î^1

80

= 70

= 60

-

-

50 U

c0

Fig. 9a

100^ 200^ 300^

400Zr [PPM]

Record 1986/6^ 16/F50/13

- gt

50

Y= 10.77+ 0.10X r= 0.88 ••

,c) •0 • ,,,„---^•

/a- ..---o^A

• -- -^•

.04.

r*

40

30r-■

>-

20

Fig. 9b

100^200^300^400Zr [PPM]

Record 1986/6^18/F50/14

b3

100^

200^

300^ 400Zr- EPPMJ

10

9

B

7

3

2

1

64

Fig. 9c

Record 1986/6^ 16/F50/15

4

65

Fig.9d

lo^20^

30Nb [PPM]

Record 1986/6^1 6 / F50 1 113

Fig. 9e

400

300

100

500

P [PPM]1 0 00^

1 500

Record 1986/6^ 18/F50/17

Wo

100

• ••

••

200

400

300

Fig. 9f

5000^ 10000^

15000T [PPM]

Record 1986/6^ 16/F50/18

Fig.9g

15000

113/f50/19Record 1986/6

50

40

30

>-20

10

0. 35

0. 30

0. 25

0. 20

0. 15

0. 10

0.05

Fig.9h

0.5^1.0^1.5^

2. 0^

25

T 02 Ewt:Z.JRecord 1986/6^

16/F50/20

0

0

04-A0

10

Fig.10

4.0

3. 0

2. 0

_^•^S14. 0_^ E *

°_^•^ o&^Ift_-^hb I

_^• 0.^*__It...i.t.1.0 -

^

^ cs^-scow'_ DH

50^

100^

150^

200

Ti/Zr-

Record 1986/6^ I6/F50/21

III

15 205^10

Ti02/P205Record 1986/6 161130/22

Fig.11

2. 0

—II

4. 0

3. 0

1. 0

®

•.^*

* * ,* 45 4

• It^*AA

•

I^I^.^.^1^.^.^,^.^1^.^.^.^.^1^,^.^.^,

•

*

40

30

10

DM0

•

Off^EM0•

•• •* • •

Fig. 12a

0.5^1.0^1.5^

2. 0^

25

T102 Ewt,7,]

0

Record 1986/6^ 16/F50/23

IÎ A0.5

0

** 4-

•1.•• •ôl op

• DMpl 0•

AT cpv0

EM

•

(***) •® 10 A *Jr '14,.a* 41f

••

•IÎî^ IÎ^ 1ÎÎ

1.0^1.5^2.0

T 02 Ewt%125

Fig.12b

-13

30

20

10

Record 1986/6^ 16/F50/24

1. 3

1. 2

1. 1

1. 0

0. 9

0. 8

0. 7

0. 6

0. 5

0. 4

0. 3

0. 2

0. 1

gt0^P1

•ol,op

••

-•-

• I •

EM

•

•

PO^•* •••

*

0^+ 10 *• Cl*

cp

• • -If• •

DM^•0 *

• •

• •

•

Fiq.12c

0.5^1.0^1.5^

2. 0^

25Ti 02 [wt%]

Record 1986/6^

16/F50/25

NORTH STAR BASALT NORTH STAR BASALT MOUNT ADA BASALT

Ce PPM 4.32 10.24 11.70 12.29 12.40 13.17 Ce 14.22 18.31 31.78 47.73 11.61 16.58 34.88 35.30

Nd 2.68 6.38 7.19 7.60 7.45 9.64 Nd^4.89 7.57 14.89 22.31 6.12 8.41 18.90 19.60

Sm 0.76 1.83 2.04 2.17 2.10 3.33 Sm^1.94 2.99 5.02 7.25 2.13 2.91 5.72 5.87

Eu 0.22 0.56 0.61 0.66 0.60 1.19 Eu^0.63 1.11 1.70 0.66 0.77 1.03 1.80 2.10

Gd 0.98 2.25 2.53 2.76 2.61 4.61 Tb^0.44 0.68 0.98 0.14 0.47 0.62 0.97 1.12

Dy 1.16 2.83 3.15 3.40 3.30 5.26 Yb^1.81 2.37 3.02 4.14 1.59 2.38 3.37 3.49

Er 0.75 1.87 2.06 2.25 2.16 3.05 Lu^0.47 0.61 0.70 1.03 0.50 0.52 0.69 0.71

Yb 0.75 1.95 2.09 2.26 2.16 2.73

(Ce/Yb)N 1.46 1.34 1.42 1.38 1.46 1.23 2.00 1.96 2.68 2.93 1.86 1.77 2.63 2.57-JO (Ce/Sm)N 1.33 1.31 1.35 1.33 1.39 0.93 1.72 1.44 1.49 1.55 1.28 1.34 1.43 1.41

(Sm/YWN 1.10 1.02 1.06 1.04 1.05 1.32 1.16 1.37 1.80 1.90 1.45 1.33 1.84 1.82

Y PPM 6 17 19 20 19 29 12 22 29 39 14 20 28 29

Zr 23 125 74 77 77 105 67 92 138 210 61 77 169 171

Hf ,^1.839 2.633 4.088 6.063 1.785 2.196 4.357 4.555

Nb 3 4 4 2 4 4 4 7 9 3 5 9 9

Th 0.918 1.137 1.643 2.407 0.599 0.791 1.487 1.659

Rb 40 23 10 3 5 6 6 17 19

Ba 29 214 105 79 18 89 21 242 234 182 22 18 45 55

Sr 25 111 112 71 95 130 35 120 125 123 176 90 239 139

Ni 1163 146 138 115 108 56 141 49 56 9 76 71 41 41

DUFFERFORMATION DOLERITES

APEXBASALT

SALGASH SUBGROUP

EUROBASALT

GORGE CREEK GROUP

CHARTER IS BASALT HONEYEATER BASALT

Rock Type

7504

0046J

TO

7504

0043A

TD

7504

0066C

TD

49336

HMB

49325

TB

49344

TB

49347

TB

49349

TB

49271

HMB

49261

TB

49269

TB

49275

HMB

49250

TB

49385

HMB

49379

TB

49375

TD

49398

TB

SiO2^Wt% 50.04 50.29 49.66 51.11 49.76 49.27 48.80 46.22 44.22 48.42 49.13 49.16 50.96 49.30 50.38 46.78 49.31

Ti 0 2 1.33 1.35 2.18 0.51 0.99 1.03 1.11 1.67 0.54 0.51 0.54 0.61 0.75 0.63 0.99 0.31 1.01

Al 2 03 13.28 13.78 13.47 12.18 11.86 14.53 14.40 11.99 14.35 15.84 15.31 14.01 12.95 9.95 14.52 18.47 14.91

FeOt 14.60 13.81 15.25 9.60 10.66 12.60 12.90 15.29 9.14 8.08 8.77 10.87 11.48 10.32 10.47 9.75 10.81

MnO 0.25 0.22 0.24 0.19 0.21 0.19 0.22 0.22 0.19 0.16 0.16 0.21 0.15 0.19 0.20 0.18 0.20

MgO 6.43 5.86 4.85 12.00 7.75 7.45 7.00 4.62 10.60 8.65 8.40 9.15 4.08 12.20 8.15 7.45 7.80

CaO 8.86 9.09 7.22 9.28 14.45 8.20 7.88 7.16 10.57 12.38 9.44 7.28 6.45 9.95 7.22 9.14 7.81

Na 2 0 1.64 2.51 2.25 2.26 1.70 1.84 2.46 3.22 1.87 1.60 3.46 3.54 2.20 1.52 2.04 1.45 2.46

0'2 0.22 0.56 0.47 0.15 0.09 0.28 0.25 • 0.08 0.25 0.19 0.03 0.28 1.31 0.72 1.29 0.39 0.87

P 2 0 5 0.09 0.08 0.18 0.06 0.12 0.10 0.12 0.17 0.06 0.06 0.06 0.05 0.05 0.07 0.14 0.04 0.15

H 2Ot 1.80 0.96 2.14 2.30 1.51 4.14 4.12 4.06 4.94 3.70 4.12 3.98 3.98 3.98 4.22 5.86 3.90

C02 0.20 0.33 0.82 0.05 0.15 0.15 0.30 4.75 2.30 0.20 0.15 0.10 4.75 0.35 0.15 0.05 0.05

Total 98.76 98.86 98.75 99.69 99.35 99.78 99.56 99.45 99.03 99.79 99.57 99.18 99.11 99.19 99.77 99.87 99.36

Mg'value 44.0 43.0 36.2 69.0 56.4 51.3 49.2 35.0 67.4 65.6 63.1 60.1 38.8 67.8 58.1 57.7 56.2

Qz^Wt% 7.71 3.47 8.98 3.34 4.74 2.17 13.49 1.24 22.05 2.28 1.81 0.89

Fo 2.88 5.41 7.74 8.71 2.46

Fa 1.51 2.41 4.87 6.47 1.35

En 13.53 11.19 11.63 20.36 8.37 17.35 16.22 11.99 25.34 15.28 5.73 13.46 13.98 20.53 19.35 19.14 17.59

Fs 13.69 11.62 14.80 9.67 4.54 13.97 14.76 12.48 18.05 5.82 3.27 8.04 12.17 10.22 12.89 11.65 10.46

Wo 5.95 7.56 1.80 9.71 18.34 3.71 3.88 3.31 10.50 8.44 5.97 12.47 3.18 0.90 4.52

En 2.90 3.65 0.79 6.16 11.22 1.99 1.98 2.19 7.04 5.08 3.41 7.82 1.82 0.53 2.69

Fs 2.94 3.79 1.01 2.93 6.09 1.60 1.80 0.88 2.68 2.90 2.30 3.89 1.22 0.32 1.60

Mt 4.82 4.52 5.05 1.47 4.27 3.87 3.53 8.04 3.06 3.21 1.88 2.05 4.95 1.64 2.30 3.67 3.89

11 2.59 2.61 4.26 0.99 1.91 2.04 2.20 3.30 1.09 1.00 1.07 1.21 1.49 1.25 1.96 0.62 2.00

An 28.96 25.09 25.98 23.22 24.83 31.84 28.72 4.57 31.79 36.75 27.34 22.54 1.72 19.08 27.81 45.30 28.26

Ab 14.24 21.59 19.58 19.60 14.60 16.22 21.73 28.38 16.75 14.02 30.60 31.39 19.49 13.49 18.01 13.00 21.73

Or 1.33 3.36 2.86 0.91 0.54 1.72 1.54 0.49 1.56 1.16 0.19 1.73 8.10 4.46 7.95 2.44 5.37

5.21 7.65

Ca 0.47 0.76 1.92 0.12 1.15 0.36 0.71 11.25 5.54 0.47 0.36 0.24 8.40 0.83 0.36 0.12 0.12

4

SALGASH SUBGROUP^

GORGE CREEK CROUP

DUFFER

FORMATION DOLERITES

APEX

BASALT

EURO

BASALT CHARTERIS BASALT HONEYEATER BASALT

Ce^PPM 14.38 14.34 26.61 3.44 14.09 9.26 11.36 19.07 5.40 8.03 7.41 6.92 5.76 6.77 15.30 7.40 17.52

Nd 8.42 9.09 13.36 7.02 11.82 3.30 4.31 3.80 3.23 3.46 7.99

Sm 3.29 2.96 4.77 1.26 2.79 2.28 2.62 4.06 1.19 1.22 1.28 1.45 1.37 1.16 3.23 0.72 3.63

Eu 1.30 1.17 1.89 0.39 1.09 0.84 0.95 1.57 0.54 0.53 0.56 0.51 0.53 0.52 1.09 0.55 1.12

Tb 0.68 0.69 0.97 0.31 0.55 0.55 0.60 0.77 0.27 0.29 0.30 0.35 0.33 0.33 0.72 0.40 0.77

Yb 2.89 2.85 4.16 1.58 2.29 2.71 2.49 1.17 1.05 1.06 1.42 1.40 1.48 3.45 2.96 3.27

Lu 0.51 0.50 0.76 0.71 0.44 0.37 0.26 0.49 0.45

(Ce/Yb)N 1.27 1.28 1.63 0.61 2.27 1.03 1.07 1.95 1.17 1.95 1.78 1.24 1.05 1.16 1.13 0.64 1.36

(Ce/Sm)N 1.03 1.14 1.31 0.64 1.19 0.95 1.02 1.10 1.06 1.54 1.36 1.12 0.99 1.37 1.11 2.41 1.13

(Sm/Yb)N 1.23 1.13 1.24 0.95 1.91 1.08 1.05 1.77 1.10 1.26 1.31 1.11 1.06 0.85 1.01 0.26 1.20

Y^PPM 27 26 35 12 19^:. 22 22 26 12 9 11.1313 12 14 28 10 31

Zr 84 83 144 29 62 60 62 115 27 26 29 32 37 33 93 14 103

Hf 2.29 2.489 3.928 0.824 1.843 1.631 1.915 3.059 0.804 0.898 0.913 0.989 1.302 1.072^4.289 1.02 2.883

Nb 3 3 6 2 2 4 3 4

Th 0.55 0.205 0.435 0.419 0.387 0.556

Rb 5 24 22 4 10 6 6 7 5 43 27 33 7 19

Ba 84 836 368 14 7 37 25 7 51 72 13 64 128 486 1642 87 261

Sr 190 186 321 64 136 76 106 74 151 242 98 77 71 54 150 91 137

Ni 89 84 49 267 128 126 120 40 227 199 192 134 31 182 53 87 56

WHIN CREEK GROUP^F0R1ESCUE GROUP

^

WARANBIE BASALT^LOUDEN VOLCANICS^

NEGRI VOLCANICS^ NT ROE BASALT^ MENA BASALT

8004 8004 80048004 8004 8004 8004

^

0270 0268 0273^70024 70026 70022^70001 70012 70009^331/337^331/338 331/339^68952 68963 68951 69031 68947^0111^0114 0122 0117Rock Type^TD^TB^TO^TAP^TAP^TBA^TAP^TOP^TBA^HMB^HMS^HMB^TB^TB^TEA^TA^TA^TA^TB^TB^TB

SiO2^Wt% 48.00 48.40 47.00 56.00 56.90 54.70 56.50 53.60 52.60 51.84 55.39 54.73 46.20 52.40 49.60 55.50 57.60 55.60 53.20 54.70 53.80

TiO2 1.21 1.19 1.70 0.44 0.46 0.90 0.91 1.04 1.03 0.39 0.43 0.39 0.94 0.84 1.09 0.66 1.13 0.65 1.38 1.05 1.26

Al 203 14.90 14.70 12.60 14.70 14.50 11.50 12.00 13.40 13.60 9.93 11.69 11.92 11.00 12.70 12.80 12.60 12.30 14.00 14.10 13.80 13.60FeOt 12.95 12.59 14.66 7.65 7.61 9.98 9.99 10.66 10.35 9.68 9.30 9.68 9.81 8.28 10.78 19.17 15.45 8.91 10.80 9.17 10.26Mn0 0.23 0.22 0.25 0.13 0.14 0.15 0.15 0.15 0.16 0.23 0.22 0.19 0.18 0.12 0.13 0.07 0.09 0.14 0.15 0.12 0.14MgO 8.18 7.77 2.96 6.50 6.00 5.35 5.70 5.25 4.95 16.50 12.26 11.71 5.50 3.76 4.74 4.98 3.72 5.41 4.88 3.98 4.04Ca° 10.50 9.88 5.25 6.70 6.30 10.30 6.85 8.50 7.90 9.06 7.86 7.51 8.65 6.55 7.60 0.16 1.23 6.52 6.42 6.40 7.30Na20 1.59 2.17 4.14 3.38 3.47 2.94 2.54 3.29 4.90 0.98 1.92 2.72 0.82 2.26 2.34 0.04 0.20 3.52 3.06 3.14 2.46K

20 0.48 0.41 0.67 1.73 2.04 0.74 2.38 0.93 0.15 0.34 0.18 0.07 0.97 1.70 0.30 0.44 0.34 1.88 1.56 2.28 2.80P205 0.14 0.16 0.18 0.05 0.06 0.10, 0.10 0.12 0.09 0.04 0.04 0.02 0.14 0.16 0.17 0.09 0.17 0.15 0.33 0.24 0.29H

20t 1.70 1.72 2.58 2.60 2.60 2.09 2.40 2.23 2.42 4.06 1.76 2.47 2.79 2.93 4.04 6.12 5.45 2.76 3.40 3.01 2.70

.-I..0

CO2 0.05 0.05 7.65 0.08 1.24 0.14 0.08 1.08 12.50 8.45 6.45 1.34 0.10 0.15 1.35 1.20

Total 99.93 99.26 99.64 99.96 100.08 99.99 99.66 99.25 99.23 98.88 99.22 98.83 99.50 100.15 100.04 99.83 99.02 99.64 99.43 99.24 99.85

Mg'value 53.0 52.4 26.5 60.2 58.4 48.8 50.4 46.7 46.0 62.6 56.3 54.3 50.0 44.7 43.9 31.6 29.4 52.0 44.6 43.6 41.2

Qz^Wt% 8.46 4.33 4.76 9.75 8.52 5.41 0.14 4.63 1.13 23.34 22.13 21.43 35.66 40.69 3.85 5.29 8.58 7.95Fo 1.87 2.31 3.24OL

1.81 2.20 1.47

EnIs13.89

12.15

12.38

10.73

7.56

17.32

13.41

8.23

12.17

8.53

7.29

5.44

10.52

9.28

8.48

7.30

9.19

9.79

30.55

12.58

26.63

14.16

25.20

14.63

14.12

15.57

9.60

12.53

12.24

16.17

13.20

29.34

9.84

26.27

10.85

10.34

10.90

12.81

9.31

10.70

8.57

10.07Wo

Di7.95 7.89 5.38 5.51 11.26 7.75 9.29 7.36 9.71 6.73 7.19 5.95 3.73 2.09 3.82

En 4.12 4.11 3.17 3.10 6.21 4.01 4.85 3.51 6.39 4.14 4.31 2.98 1.70 0.96 1.74Fs 3.61 3.56 1.94 2.17 4.63 3.53 4.18 3.74 2.63 2.20 2.50 2.84 2.00 1.10 2.05Mt 2.21 2.46 4.06 1.81 1.36 3.45 2.23 3.24 2.36 0.49 0.65 0.98 4.06 1.59 0.92 1.67 2.04 2.66Ii 2.33 2.31 3.31 0.86 0.89 1.73 1.77 2.01 2.01 0.75 0.82 0.75 1.84 1.64 2.15 1.33 2.28 1.27 2.72 2.07 2.45An 32.59 29.80 20.30 18.37 16.21 14.65 19.41 15.11 21.94 22.93 20.35 0.22 17.30 20.88 17.43 18.24Ab 13.66 18.77 35.91 29.28 30.02 25.21 22.00 28.37 42.70 8.39 16.37 23.29 7.15 19.61 20.52 0.36 1.80 30.58 26.86 27.52 21.33Or 2.88 2.48 4.06 10.47 12.33 4.43 14.39 5.60 0.91 2.03 1.07 0.42 5.91 10.30 1.84 2.77 2.13 11.41 9.56 13.95 16.96C 5.19 8.87 7.32 8.94 12.75 12.32Ca 0.12 0.12 17.84 0.19 2.86 0.33 0.19 2.53 29.30 19.71 15.21 3.24 0.23 0.35 3.18 2.80

- 6 -

WIN CREEK GROUP^ FOFITESCUE GROUP

WARRANBIE BASALT LOUDEN VOLCANIC NEGRI VOLCANICS NT ROE BASALT KYLENA BASALT

Ce^PPM 9.35 9.45 34.62 22.07 20.18 34.26 38.43 36.82 36.57 16.90 21.00 23.20 32.46 36.55 39.89 64.71 15.06 51.94 93.39 101.03 99.25

Nd 5.33 5.73 13.71 9.19 8.50 16.54 17.38 17.34 17.57 6.74 7.70 9.50 13.51 16.02 17.97 18.83 21.58 38.42 37.90 41.99

Sm 2.05 2.07 3.43 2.04 1.97 3.63 4.02 3.85 3.79 1.61 1.75 2.08 3.77 3.92 4.57 4.90 3.25 3.92 7.81 7.63 7.50

Eu 1.19 1.18 1.22 0.50 0.47 1,04 1.29 1.14 1.07 0.44 0.57 0.61 1.30 1.20 1.40 1.47 1.15 1.10 1.61 1.80 1.95

Tb 0.48 0.44 0.49 0.31 0.35 0.57 0.47 0.54 0.54 0.62 0.68 0.57 0.75 1.29 1.77 1.34

Yb 1.30 1.61 1.75 1.41 1.48 1.73 1.53 1.57 1.45 1.39 1.44 1 .62

0:::1 0 : ::1

195..961 1.88 2.17 4.51 4.68 4.44

Lu 0.43 0.43 0.39 0.42 0.78 0.86 0.86

(Ce/Yb)N 1.83 1.49 5.03 3.98 3.47 5.04 6.39 5.96 6.41 3.09 3.71 3.64 4.86 5.67 5.20 8.40 2.04 6.09 5.27 5.49 5.69

CD (Ce/Sm)N 1.07 1.07 2.37 2.54 2.40 2.21 2.24 2.24 2.26 2.46 2.82 2.62 2.02 2.19 2.05 3.10 1.09 3.11 2.81 3.11 3.11

C) (Sm/Yb)N 1.71 1.39 2.12 1.57 1.44 2.27 2.85 2.66 2.83 1.26 1.32 1.39 2.40 2.59 2.54 2.71 1.87 1.96 1.88 1.77 1.83

Y^PPM^17^18^18^13^13^18^18^18^18

Zr^49^52^124^74^73^129^136^128^128

HF^1.547 1.696 3.53^1.73^1.792 2.866^3.279 2.974 2.888

Nb^ 8^2^3^4^5^5^5

Th^0.425 0.46^2.22^5.08^5.264 7.51^9.593 6.627 6.301

Rb^17^20^15^60^56^20^69^22^4

Ba^108^102^224^511^605^218^1017^564^41

Sr^115^132^219^177^229^538^298^579^125

21^20^24^27^22^25^47^47^47

132^147^154^123^141^185^389^381^393

2.912 3.197 3.452 2.69^3.22^3.837 7.713 8.031

4^4^5^5^4^ 20^23^21

2.792 3.567 2.88 5.541 1.78^2.617 9.738 3.95 10.985

29^58^9^17^7^65^70^92^110

441^762^141^242^112^1140^585^501^754

269^251^398^8^44^452^264^175^249

Ni^143^131^177^83^77^147^160^112^111^

303^81^164^151^310^79^47^40^35

TABLE 1 - UNIT-ROCK TYPE CLASSIFICATION OF RE ELEMENT ANALYSES*

APPROXIMATEAGE (b.y.)**

PK^HMB^TB^TD^TA DACITE RHYOLITE SILICIFIEDLAYA

FORTESCUE GROUP

2.75^

WHIM CREEK GROUP

Maddina Basalt (MB)^ 2^2Nymerina Basalt (NB)^1^3Kylena Basalt (KB)^ 3^1Mt Roe Basalt (MRS.)^ 3^2

Louden Volcanics (LV)^1^2Negri Volcanics (NV)^3^2^1

4445

36

Mons Cupri Fragmentals (MCF)^-Mt Brown Rhyolite (MBR)^-

3.0^ Warambie Basalt (MB)^ 1^2 3

GORGE CREEK GROUPHoneyeater Basalt (MB)^1^2^1 4Charteris Basalt (CB)^2^3 5

WARRAWOONA GEOUP3.2^ Wyman Format ion (WF)^ -

Euro Basalt (EB)^ 3 33.34^)^ ( Panorama Formation (PF)^-

3.2^) ( Apex Basalt (AB)^1^1 23.45^ Duffer Formation (DF)^-^3^1 5 2 113.6^ Mt Ada Basalt (MAB)^ 4 43.7^ North Star

Basalt (NSB)^1^3^6^2 2 14

1^11^34^6^11 9 10 3 72

PK^-^peridotitic komatiite (MgO^20%)HMB -^high-Mg basalt (Mg0 > 8%;^MgO/AL)01 > 0.6) *TB^-^tholeiitic basalt^(MgO 4 8%;^m010,12 .‹ 0.6)TD^-^tholeiitic doleriteTA^-^tholeiitic andesite and silicified basalt (Si0 2 > 55%)

* Including felsic - intermediate volcanic samples,to be discussed elsewhere (Glikson et al., in prep.)

1111^11 11^11 01 1 0* R 8 6 0 0 6 0 *

** For compilation of isotopic ages refer to Hickman (1983)and Blake and McNaughton (1984). The Ca 3.7 b.y. and3.6 b.y. ages for the NSB and MAB, respectively, are Sm-Ndisochron ages (B. Jahn, in prep.).

TABLE 2

RE AND HFS ELEMENTS RANGES OF THOLEIITIC BASALTS 0DOLERITES AND ANDESITES

ACCORDING TO VOLCANIC UNITS

tREE*Plan

(Ce/Yb)N (Ce/Sm)N (Sm/Yb)N TiO2% wt

P 0 ZrPrim

NbPlin

North Star Basalt (NSB) 6 30-80 1.0-3.0 0.9-1.6 1.0-2.0 0.58-2.31 0.03-0.23 77-210 2-9 19-39

Mt Ada Basalt (MAB) 4 20-70 1.8-2.7 1.2-1.5 1.4-1.9 0.79-2.05 0.06-0.21 61-171 3-9 14-29

Duffer Fm dolerites (DF) 3 30-55 1.3-1.7 1.1-1.3 1.1-1.3 1.33-2.18 0.08-0.18 83-144 3-6 26-35

Apex Basalt (AB) 1 30 2.3 1.2 1.9 0.99 0.12 62 2 19

Euro Basalt (EB) 3 17-40 1.0-2.0 0.9-1.1 1.0-1.8 1.03-1.67 0.10-0.17 22-26 0-4 22-26

Charteris Basalt (CB) 3 15-17 1.0-1.9 1.3-1.6 1.2-1.3 0.51-0.75 0.05-0.06 29-33 N.D. 9-12

Honeyeater Basalt (NB) 3 27-32 1.1-1.4 1.1 1.0-1.2 0.31-1.01 0.04-0.14 14-103 3-4 10-31

Warambie Basalt (WB)** 2 20 1.6 1.0 1.4-1.7 1.19-1.21 0.14-0.18 49-124 0-8 17-18

Louden Volcanics (LV) 3 35-55 3.4-4.0 2.2-2.5 1.4-2.3 0.44-0.90 0.05-0.10 73-129 2-4 13-18

Negri Vblcanics (NV) 3 60-65 5.8-6.3 2.2 2.6-2.9 0.91-1.04 0.09-0.12 128-136 5 18

Mt Roe Basalt (MRB) 5 54-67 4.8-5.6 2.0-2.2 2.4-2.6 0.66-1.13 0.09-0.17 123-154 4-5 20-27

Kylena Basalt (KB) 4 80-160 5.2-6.0 2.7-3.1 1.7-2.0 0.65-1.38 0.15-0.33 185-393 20-23 25-47

Nymerina Basalt (NB) 3 70-115 4.0-6.1 2.1-2.4 1.7-2.8 0.95-1.22 0.14-0.15 171-210 7-10 26-29

Maddina Basalt (MB) 4 75-100 3.8-4.8 2.3-2.7 1.5-1.8 0.68-1.03 0.08-0.14 151-211 7-11 29-36

* Ce, Nd, Sm, Eu, Tb, Yb, Lu** excluding a highly carbonated sample

APPENDIX 1

MAJOR ELEMENTS, TRACE ELEMENTS AND CIPW NORMS FOR PILBARA VOLCANICS

TALGA TALGA SUB GROUP

NORTH STAR BASALT^

NORTH STAR BASALT^

MOUNT ADA BASALT

Rock Type

7504

0019H

PK

7504

0025D

HMB

7504

0024C

HMB

7504

0024A

TB

7504

0026B

TB

7504

0026A

TB

45075

HMB

45068

TB

45064

TB

45062

TB

45092

TB

45086

TB

45076

TB

45079

TB

Major^SiO2 Wt% 42.50 51.79 50.77 51.30 51.32 50.57 48.63 50.96 49.87 48.17 49.25 48.85 45.27 46.76Elements^

TiO 2 0.28 0.52 0.56 0.58 0.58 1.38 0.49 1.16 1.56 2.31 0.79 1.02 1.99 2.05

Al 203 6.18 13.60 14.39 14.82 14.85 13.52 12.45 13.81 13.01 12.84 12.33 11.51 12.00 12.43

FeOt 10.41 9.04 9.29 9.42 9.73 14.20 8.35 12.24 14.23 17.09 10.80 11.38 14.37 13.60

MnO 0.21 0.20 0.21 0.25 0.32 0.25 0.18 0.22 0.22 0.26 0.18 0.17 0.22 0.26

MgO 28.11 10.82 9.64 8.61 7.69 6.15 9.96 6.98 6.05 5.68 7.77 5.95 4.44 3.09

CaO 4.09 8.77 9.67 10.51 11.83 9.58 8.55 10.21 8.76 6.95 9.19 8.81 6.43 8.72

Na20 0.04 0.82 1.16 1.64 0.85 1.47 0.07 1.85 2.33 1.96 1.30 1.00 2.63 1.92

K200.01 0.89 0.49 0.30 0.27 0.35 0.02 0.31 0.56 0.61 0.01 0.03 0.04 0.04

P20 50.02 0.03 0.03 0.04 0.03 0.13 0.04 0.08 0.16 0.23 0.06 0.07 0.20 0.21

H2Ot 7.26 2.24 1.76 1.33 1.17 1.00 5.13 0.80 1.18 1.50 3.64 3.77 1.56 2.30

CO2 0.03 0.11 0.03 0.04 0.10 0.12 4.55 0.05 0.50 0.30 2.75 5.20 8.35 6.10

Total 99.14 98.84 98.00 98.84 98.75 98.74 98.43 98.68 98.44 98.23 98.08 97.78 97.52 97.49

Mg value 82.8 68.1 64.9 62.0 58.5 43.6 68.0 50.4 43.1 37.2 56.2 48.2 35.5 28.8

CIPW^Qz Wt% 7.05 5.74 4.77 8.64 8.28 24.63 5.62 4.70 6.01 13.17 25.18 17.10 24.16

Norm^Fo 29.97

01 Fa 6.07

En 32.08 24.42 20.69 16.77 13.99 12.16 26.53 12.77 12.13 13.34 20.39 15.71 11.46 8.05Hy

Fs 5.90 9.55 9.30 8.61 8.30 12.48 10.54 9.98 12.45 16.89 12.90 13.54 15.25 14.46

Wo 1.50 5.09 6.48 8.30 9.36 7.09 9.07 6.78 2.86 0.02

En 1.14 3.39 4.17 5.16 5.58 3.44 4.92 3.29 1.26 0.01Di

Fs 0.21 1.33 1.87 2.65 3.31 3.53 3.84 3.38 1.60 0.01

Mt 3.64 3.00 3.10 3.10 3.20 4.66 2.87 4.01 4.69 5.68 3.67 3.88 4.79 4.58

Ii 0.58 1.02 1.10 1.13 1.13 2.67 1.00 2.24 3.03 4.53 1.58 2.05 3.92 4.07

An 18.07 31.79 33.77 32.92 36.68 29.80 14.32 28.97 23.94 25.22 29.29 11.00 3.48Pig

Ab 0.37 7.16 10.17 14.19 7.35 12.67 0.63 15.93 20.18 17.11 11.60 8.97 23.06 16.99

Or 0.06 5.43 3.00 1.81 1.63 2.11 0.13 1.86 3.39 3.72 0.06 0.19 0.24 0.25

C 7.92 6.39 7.91 8.38

Ca 0.07 0.26 0.07 0.09 0.23 0.28 11.07 0.12 1.16 0.70 6.59 12.54 19.68 14.51

NORTH STAR BASALT NORTH STAR BASALT MOUNT ADA BASALT

Ce PPM 4.32 10.24 11.70 12.29 12.40 13.17 Ce 14.22 18.31 31.78 47.73 11.61 16.58 34.88 35.30

Nd 2.68 6.38 7.19 7.60 7.45 9.64 Nd^4.89 7.57 14.89 22.31 6.12 8.41 18.90 19.60

Sm 0.76 1.83 2.04 2.17 2.10 3.33 Sm^1.94 2.99 5.02 7.25 2.13 2.91 5.72 5.87

Eu 0.22 0.56 0.61 0.66 0.60 1.19 Eu^0.63 1.11 1.70 0.66 0.77 1.03 1.80 2.10

Gd 0.98 2.25 2.53 2.76 2.61 4.61 Tb^0.44 0.68 0.98 0.14 0.47 0.62 0.97 1.12

Dy 1.16 2.83 3.15 3.40 3.30 5.26 Yb^1.81 2.37 3.02 4.14 1.59 2.38 3.37 3.49

Er 0.75 1.87 2.06 2.25 2.16 3.05 Lu^0.47 0.61 0.70 1.03 0.50 0.52 0.69 0.71

Yb 0.75 1.95 2.09 2.26 2.16 2.73

(Ce/Yb)N 1.46 1.34 1.42 1.38 1.46 1.23 2.00 1.96 2.68 2.93 1.86 1.77 2.63 2.57

(Ce/Sm)N 1.33 1.31 1.35 1.33 1.39 0.93 1.72 1.44 1.49 1.55 1.28 1.34 1.43 1.41

(Sm/Yb)N 1.10 1.02 1.06 1.04 1.05 1.32 1.16 1.37 1.80 1.90 1.45 1.33 1.84 1.82

Y PPM 6 17 19 20 19 29 12 22 29 39 14 20 28 29

Zr 23 125 74 77 77 105 67 92 138 210 61 77 169 171

Hf 1.839 2.633 4.088 6.063 1.785 2.196 4.357 4.555

Nb 3 4 4 2 4 4 4 7 9 3 5 9 9

Th 0.918 1.137 1.643 2.407 0.599 0.791 1.487 1.659

Rb 40 23 10 3 5 6 6 17 19

Ba 29 214 105 79 18 89 21 242 234 182 22 18 45 55

Sr 25 111 112 71 95 130 35 120 125 123 176 90 239 139

Ni 1163 146 138 115 108 56 141 49 56 9 76 71 41 41

SALGASH SUBGROUP^

GORGE CREEK GROUP

DUFFER^

APEX^

EUROFORMATION DOLERITES

^BASALT^

BASALT^

CHARTERIS BASALT^HONEYEATER BASALT

Rock Type

7504

0046J

TD

7504

0043A

TD

7504

0066C

TD

49336

HMB

49325

TB

49344

TB

49347

TB

49349

TB

49271

HMB

49261

TB

49269

TB

49275

HMB

49250

TB

49385

HMB

49379

TB

49375

TD

49398

TB

SiO2^Wt% 50.04 50.29 49.66 51.11 49.76 49.27 48.80 46.22 44.22 48.42 49.13 49.16 50.96 49.30 50.38 46.78 49.31

Ti 02 1.33 1.35 2.18 0.51 0.99 1.03 1.11 1.67 0.54 0.51 0.54 0.61 0.75 0.63 0.99 0.31 1.01

Al203

13.28 13.78 13.47 12.18 11.86 14.53 14.40 11.99 14.35 15.84 15.31 14.01 12.95 9.95 14.52 18.47 14.91

FeOt 14.60 13.81 15.25 9.60 10.66 12.60 12.90 15.29 9.14 8.08 8.77 10.87 11.48 10.32 10.47 9.75 10.81

MnO 0.25 0.22 0.24 0.19 0.21 0.19 0.22 0.22 0.19 0.16 0.16 0.21 0.15 0.19 0.20 0.18 0.20

MgO 6.43 5.86 4.85 12.00 7.75 7.45 7.00 4.62 10.60 8.65 8.40 9.15 4.08 12.20 8.15 7.45 7.80

Ca0 8.86 9.09 7.22 9.28 14.45 8.20 7.88 7.16 10.57 12.38 9.44 7.28 6.45 9.95 7.22 9.14 7.81

Na20 1.64 2.51 2.25 2.26 1.70 1.84 2.46 3.22 1.87 1.60 3.46 3.54 2.20 1.52 2.04 1.45 2.46

K20 0.22 0.56 0.47 0.15 0.09 0.28 0.25 0.08 0.25 0.19 0.03 0.28 1.31 0.72 1.29 0.39 0.87

P205

0.09 0.08 0.18 0.06 0.12 0.10 0.12 0.17 0.06 0.06 0.06 0.05 0.05 0.07 0.14 0.04 0.15

H2Ot 1.80 0.96 2.14 2.30 1.51 4.14 4.12 4.06 4.94 3.70 4.12 3.98 3.98 3.98 4.22 5.86 3.90

C02

0.20 0.33 0.82 0.05 0.15 0.15 0.30 4.75 2.30 0.20 0.15 0.10 4.75 0.35 0.15 0.05 0.05

Total 98.76 98.86 98.75 99.69 99.35 99.78 99.56 99.45 99.03 99.79 99.57 99.18 99.11 99.19 99.77 99.87 99.36

Mg' value 44.0 43.0 36.2 69.0 56.4 51.3 49.2 35.0 67.4 65.6 63.1 60.1 38.8 67.8 58.1 57.7 56.2

Qz^Wt% 7.71 3.47 8.98 3.34 4.74 2.17 13.49 1.24 22.05 2.28 1.81 0.89

Fo 2.88 5.41 7.74 8.71 2.46

Fa 1.51 2.41 4.87 6.47 1.35

En 13.53 11.19 11.63 20.36 8.37 17.35 16.22 11.99 25.34 15.28 5.73 13.46 13.98 20.53 19.35 19.14 17.59

Fs 13.69 11.62 14.80 9.67 4.54 13.97 14.76 12.48 18.05 5.82 3.27 8.04 12.17 10.22 12.89 11.65 10.46

Wo 5.95 7.56 1.80 9.71 18.34 3.71 3.88 3.31 10.50 8.44 5.97 12.47 3.18 0.90 4.52

En 2.90 3.65 0.79 6.16 11.22 1.99 1.98 2.19 7.04 5.08 3.41 7.82 1.82 0.53 2.69

Fs 2.94 3.79 1.01 2.93 6.09 1.60 1.80 0.88 2.68 2.90 2.30 3.89 1.22 0.32 1.60

Mt 4.82 4.52 5.05 1.47 4.27 3.87 3.53 8.04 3.06 3.21 1.88 2.05 4.95 1.64 2.30 3.67 3.89

Ii 2.59 2.61 4.26 0.99 1.91 2.04 2.20 3.30 1.09 1.00 1.07 1.21 1.49 1.25 1.96 0.62 2.00

An 28.96 25.09 25.98 23.22 24.83 31.84 28.72 4.57 31.79 36.75 27.34 22.54 1.72 19.08 27.81 45.30 28.26

Ab 14.24 21.59 19.58 19.60 14.60 16.22 21.73 28.38 16.75 14.02 30.60 31.39 19.49 13.49 18.01 13.00 21.73

Or 1.33 3.36 2.86 0.91 0.54 1.72 1.54 0.49 1.56 1.16 0.19 1.73 8.10 4.46 7.95 2.44 5.37

5.21 7.65

Ca 0.47 0.76 1.92 0.12 1.15 0.36 0.71 11.25 5.54 0.47 0.36 0.24 8.40 0.83 0.36 0.12 0.12

- 4 -

SALGASH SUBGROUP^ GORGE CREEK CROUP

DUFFER^APEX^EURO

FORMATION DOLERITES^BASALT^BASALT^CHARTERIS BASALT^HONEYEATER BASALT

Ce^ppm^14.38 14.34 26.61^3.44^14.09^9.26 11.36 19.07^5.40^8.03^7.41^6.92^5.76^6.77 15.30^7.40 17.52

Nd^8.42^9.09 13.36^7.02^ 11.82^3.30^4.31^3.80^3.23^3.46^7.99

Sm^3.29^2.96^4.77^1.26^2.79^2.28^2.62^4.06^1.19^1.22^1.28^1.45^1.37^1.16^3.23^0.72^3.63

Eu^1.30^1.17^1.89^0.39^1.09^0.84^0.95^1.57^0.54^0.53^0.56^0.51^0.53^0.52^1.09^0.55^1.12

Tb^0.68^0.69^0.97^0.31^0.55^0.55^0.60^0.77^0.27^0.29^0.30^0.35^0.33^0.33^0.72^0.40^0.77

Yb^2.89^2.85^4.16^1.58^2.29^2.71^2.49^1.17^1.05^1.06^1.42^1.40^1.48^3.45^2.96^3.27

Lu^0.51^0.50^0.76^0.71^ 0.44^0.37^0.26^0.49^0.45

(Ce/Yb)N^1.27^1.28^1.63^0.61^2.27^1.03^1.07^1.95^1.17^1.95^1.78^1.24^1.05^1.16^1.13^0.64^1.36

(Ce/Sm)N^1.03^1.14^1.31^0.64^1.19^0.95^1.02^1.10^1.06^1.54^1.36^1.12^0.99^1.37^1.11^2.41^1.13

(Sm/Yb)N^1.23^1.13^1.24^0.95^1.91^1.08^1.05^1.77^1.10^1.26^1.31^1.11^1.06^0.85^1.01^0.26^1.20

Y^PPM^27^26^35^12^19^22^22^26^12^9^11^13^12^14^28^10^31

Zr^84^83^144^29^62^60^62^115^27^26^29^32^37^33^93^14^103

Hf^2.29^2.489 3.928^0.824^1.843^1.631 1.915 3.059^0.804 0.898 0.913 0.989 1.302^1.072 4.289 1.02^2.883

Nb^3^3^6^2^2^4^ 3^4

Th^ 0.55^ 0.205 0.435 0.419 0.387 0.556

Rb^5^24^22^4^10^6^6^7^5^43^27^33^7^19

Ba^84^836^368^14^7^37^25^7^51^72^13^64^128^486^1642^87^261

Sr^190^186^321^64^136^76^106^74^151^242^98^77^71^54^150^91^137

Ni^89^84^49^267^128^126^120^40^227^199^192^134^31^182^53^87^56

^

WARANBIE BASALT^LOUDEN VOLCANICS^

NEGRI VOLCANICS^

NT ROE BASALT^ KYLENA BASALT

^8004 8004 8004^ 8004 8004 8004 8004

^

0270 0268 0273^70024 70026 70022^70001 70012 70009^331/337^331/338 331/339^68952 68963 68951 69031 68947^0111^0114 0122 0117

Rock Type^TO^TB^TD^TAP^TAP^TBA^TAP^TBP^TBA^HMB^HMB^HMB^TB^TB^TBA^TA^TA^TA^TB^TB^TB

SiO2^Wt% 48.00 48.40 47.00 56.00 56.90 54.70 56.50 53.60 52.60 51.84 55.39 54.73 46.20 52.40 49.60 55.50 57.60 55.60 53.20 54.70 53.80

TiO2

1.21 1.19 1.70 0.44 0.46 0.90 0.91 1.04 1.03 0.39 0.43 0.39 0.94 0.84 1.09 0.66 1.13 0.65 1.38 1.05 1.26

Al203

14.90 14.70 12.60 14.70 14.50 11.50 12.00 13.40 13.60 9.93 11.69 11.92 11.00 12.70 12.80 12.60 12.30 14.00 14.10 13.80 13.60

FeOt 12.95 12.59 14.66 7.65 7.61 9.98 9.99 10.66 10.35 9.68 9.30 9.68 9.81 8.28 10.78 19.17 15.45 8.91 10.80 9.17 10.26

MnO 0.23 0.22 0.25 0.13 0.14 0.15 0.15 0.15 0.16 0.23 0.22 0.19 0.18 0.12 0.13 0.07 0.09 0.14 0.15 0.12 0.14

MgO 8.18 7.77 2.96 6.50 6.00 5.35 5.70 5.25 4.95 16.50 12.26 11.71 5.50 3.76 4.74 4.98 3.72 5.41 4.88 3.98 4.04

CaO 10.50 9.88 5.25 6.70 6.30 10.30 6.85 8.50 7.90 9.06 7.86 7.51 8.65 6.55 7.60 0.16 1.23 6.52 6.42 6.40 7.30

Na20 1.59 2.17 4.14 3.38 3.47 2.94 2.54 3.29 4.90 0.98 1.92 2.72 0.82 2.26 2.34 0.04 0.20 3.52 3.06 3.14 2.46

K20 0.48 0.41 0.67 1.73 2.04 0.74 2.38 0.93 0.15 0.34 0.18 0.07 0.97 1.70 0.30 0.44 0.34 1.88 1.56 2.28 2.80

P205

0.14 0.16 0.18 0.05 0.06 0.10 0.10 0.12 0.09 0.04 0.04 0.02 0.14 0.16 0.17 0.09 0.17 0.15 0.33 0.24 0.29

H20t 1.70 1.72 2.58 2.60 2.60 2.09 2.40 2.23 2.42 4.06 1.76 2.47 2.79 2.93 4.04 6.12 5.45 2.76 3.40 3.01 2.70

CO2

0.05 0.05 7.65 0.08 1.24 0.14 0.08 1.08 12.50 8.45 6.45 1.34 0.10 0.15 1.35 1.20

Total 99.93 99.26 99.64 99.96 100.08 99.99 99.66 99.25 99.23 98.88 99.22 98.83 99.50 100.15 100.04 99.83 99.02 99.64 99.43 99.24 99.85

Mg'value 53.0 52.4 26.5 60.2 58.4 48.8 50.4 46.7 46.0 62.6 56.3 54.3 50.0 44.7 43.9 31.6 29.4 52.0 44.6 43.6 41.2

Qz^Wt% 8.46 4.33 4.76 9.75 8.52 5.41 0.14 4.63 1.13 23.34 22.13 21.43 35.66 40.69 3.85 5.29 8.58 7.95

Fo 1.87 2.31 3.24

01ra 1.81 2.20 1.47

En 13.89 12.38 7.56 13.41 12.17 7.29 10.52 8.48 9.19 30.55 26.63 25.20 14.12 9.60 12.24 13.20 9.84 10.85 10.90 9.31 8.57

HyFs 12.15 10.73 17.32 8.23 8.53 5.44 9.28 7.30 9.79 12.58 14.16 14.63 15.57 12.53 16.17 29.34 26.27 10.34 12.81 10.70 10.07

Wo 7.95 7.89 5.38 5.51 11.26 7.75 9.29 7.36 9.71 6.73 7.19 5.95 3.73 2.09 3.82

DiEn 4.12 4.11 3.17 3.10 6.21 4.01 4.85 3.51 6.39 4.14 4.31 2.98 1.70 0.96 1.74

Fs 3.61 3.56 1.94 2.17 4.63 3.53 4.18 3.74 2.63 2.20 2.50 2.84 2.00 1.10 2.05

Mt 2.21 2.46 4.06 1.81 1.36 3.45 2.23 3.24 2.36 0.49 0.65 0.98 4.06 1.59 0.92 1.67 2.04 2.66

Ii 2.33 2.31 3.31 0.86 0.89 1.73 1.77 2.01 2.01 0.75 0.82 0.75 1.84 1.64 2.15 1.33 2.28 1.27 2.72 2.07 2.45

An 32.59 29.80 20.30 18.37 16.21 14.65 19.41 15.11 21.94 22.93 20.35 0.22 17.30 20.88 17.43 18.24

Ab 13.66 18.77 35.91 29.28 30.02 25.21 22.00 28.37 42.70 8.39 16.37 23.29 7.15 19.61 20.52 0.36 1.80 30.58 26.86 27.52 21.33

Or 2.88 2.48 4.06 10.47 12.33 4.43 14.39 5.60 0.91 2.03 1.07 0.42 5.91 10.30 1.84 2.77 2.13 11.41 9.56 13.95 16.96

C 5.19 8.87 7.32 8.94 12.75 12.32

Ca 0.12 0.12 17.84 0.19 2.86 0.33 0.19 2.53 29.30 19.71 15.21 3.24 0.23 0.35 3.18 2.80

- 6 -

WHIM CREEK GROUP^ FORTESCUE GROUP

WARRANBIE BASALT LOUDEN VOLCANICS NEGRI VOLCANICS NT ROE BASALT KYLENA BASALT

Ce^PPM 9.35 9.45 34.62 22.07 20.18 34.26 38.43 36.82 36.57 16.90 21.00 23.20 32.46 36.55 39.89 64.71 15.06 51.94 93.39 101.03 99.25

Nd 5.33 5.75 13.71 9.19 8.50 16.54 17.38 17.34 17.57 6.74 7.70 9.50 13.51 16.02 17.97 18.83 21.58 38.42 37.90 41.99

Sm 2.05 2.07 3.43 2.04 1.97 3.63 4.02 3.85 3.79 1.61 1.75 2.08 3.77 3.92 4.57 4.90 3.25 3.92 7.81 7.63 7.50

Eu 1.19 1.18 1.22 0.50 0.47 1.04 1.29 1.14 1.07 0.44 0.57 0.61 1.30 1.20 1.40 1.47 1.15 1.10 1.61 1.80 1.95

Tb 0.48 0.44 0.49 0.31 0.35 0.57 0.47 0.54 0.54 0.58 0.57 0.62 0.68 0.57 0.75 1.29 1.77 1.34

Yb 1.30 1.61 1.75 1.41 1.48 1.73 1.53 1.57 1.45 1.39 1.44 1.62 1.70 1.64 1.95 1.96 1.88 2.17 4.51 4.68 4.44

Lu 0.43 0.43 0.39 0.42 0.78 0.86 0.86

(Ce/Yb)N 1.83 1.49 5.03 3.98 3.47 5.04 6.39 5.96 6.41 3.09 3.71 3.64 4.86 5.67 5.20 8.40 2.04 6.09 5.27 5.49 5.69

(Ce/SION 1.07 1.07 2.37 2.54 2.40 2.21 2.24 2.24 2.26 2.46 2.82 2.62 2.02 2.19 2.05 3.10 1.09 3.11 2.81 3.11 3.11

(Sm/Yb)N 1.71 1.39 2.12 1.57 1.44 2.27 2.85 2.66 2.83 1.26 1.32 1.39 2.40 2.59 2.54 2.71 1.87 1.96 1.88 1.77 1.83

Y^PPM^17^18^18^13^13^18^18^18^18^ 21^20^24^27^22^25^47^47^47

Zr^49^52^124^74^73^129^136^128^128^ 132^147^154^123^141^185^389^381^393

HF^1.547 1.696 3.53^1.73^1.792 2.866^3.279 2.974 2.888^ 2.912 3.197 3.452 2.69^3.22^3.837 7.713 8.031

Nb^ 8^2^3^4^5^5^5^ 4^4^5^5^4^20^23^21

Th^0.425 0.46 2.22^5.08 5.264 7.51^9.593 6.627 6.301^ 2.792 3.567 2.88 5.541 1.78^2.617 9.738 3.95 10.985

Rb^17^20^15^60^56^20^69^22^4^ 29^58^9^17^7^65^70^92^110

Ba^108^102^224^511^605^218^1017^564^41^ 441^762^141^242^112^1140^585^501^754

Sr^115^132^219^177^229^538^298^579^125^ 269^251^398^8^44^452^264^175^249

Ni^143^131^177^83^77^147^160^112^111^ 303^81^164^151^310^79^47^40^35

;

1-7

NYMERINA BASALT^

MADDINA BASALT

Rock Type

8004

0130

HMBP

8004

0134

TB

8004

0131

TBA

8004

0127

TB

8004

0140

TB

8004

0141

TB

8004

0147

TA

8004

0143

TA

SiO2^Wt% 53.70 53.10 51.50 52.30 51.80 53.90 57.70 57.30

TiO2

1.07 0.95 1.22 1.16 0.78 0.82 0.68 1.03

Al203

9.25 14.00 11.30 12.70 14.40 14.50 13.90 13.60

FeOt 10.43 9.90 9.81 8.32 8.99 9.09 8.54 9.44

MnO 0.17 0.14 0.14 0.15 0.12 0.14 0.13 0.14

MgO 7.90 5.20 4.24 3.24 5.30 5.10 4.72 3.58

CaO 9.60 7.20 8.40 8.25 7.45 7.65 5.48 6.40

Na20 2.02 3.80 2.94 4.16 2.68 3.02 3.36 2.62

K20 1.38 1.36 0.47 0.85 0.69 0.78 2.78 1.58

P205

0.12 0.15 0.14 0.15 0.08 0.13 0.14 0.13

H20t 1.97 3.29 4.04 3.30 4.15 3.73 2.35 3.22

CO2

1.70 0.95 5.25 5.00 3.65 0.90 0.15 1.20

Total 99.31 100.04 99.45 99.58 100.09 99.76 99.93 100.24

Mg'value 57.4 48.4 43.5 41.0 51.2 50.0 49.6 40.3

Qz^Wt% 9.03 2.23 17.95 12.58 14.39 8.47 6.33 15.26

Fo

01 Fa

En 10.90 11.04 8.34 13.73 11.53 9.81 8.72HYFs 11.05 13.41 9.64 13.85 11.35 10.36 13.62

Wo 10.24 4.99 3.34 4.55 1.13

En 5.98 2.44 1.65 2.18 0.45Di

Fs 3.77 2.47 1.62 2.30 0.70

Mt 2.61 1.82 1.79 2.04 1.00 1.49 0.81 0.82

Ii 2.08 1.86 2.42 2.28 1.54 1.62 1.32 2.01

An 12.37 17.64 7.91 8.62 13.90 24.61 14.93 21.26

Ab 17.47 33.11 26.01 36.38 23.58 26.53 29.00 22.79

Or 8.34 8.28 2.90 5.19 4.24 4.78 16.76 9.60

C 3.33 1.94 4.52

Ca 3.95 2.23 12.48 11.75 8.63 2.12 0.35 2.81

E;)

1-8

NYMERINA BASALT MADDINA BASALT

Ce^PPM 43.17 43.55 53.82 66.92 43.29 44.51 69.84 60.08Nd 23.25 19.63 29.50 36.60 21.95 21.65 29.45 27.05Sm 4.69 4.23 5.72 6.39 4.27 4.00 4.68 5.26ELF 1.50 1.20 1.73 1.87 1.15 1.22 1.20 1.49Tb 0.83 0.69 0.91 0.96 0.81 0.95 0.93 1.06Yb 1.87 2.66 2.19 2.83 2.80 2.88 3.05 3.17Lu 0.31 0.49 0.36 0.46 0.50 0.53 0.59

(Ce/Yb)N 5.87 4.16 6.25 6.01 3.93 3.93 5.82 4.82(Ce/Sm)N 2.16 2.42 2.21 2.46 2.38 2.61 3.50 2.68(Sm/Yb)N 2.72 1.72 2.83 2.45 1.65 1.51 1.66 1.80

Y^PPM^23^29^26^29^29^30^30^36Zr^145^171^181^210^151^151^211^201Hf^3.513 4.009 4.182 5.266^7.789 3.68^8.435 4.763Nb^7^7^9^10^7^8^11^10Th^4.394 5.583 6.681 11.131^3.536 6.783^4.945 8.914Rb^57^37^15^29^19^17^119^43Ba^307^368^779^629^336^431^1247^586Sr^305^230^126^337^137^196^393^179

Ni^171^78^78^65^89

APPENDIX II

PETROGRAPHIC DEFINITIONS OF ANLAYSED SAMPLES

North Star Basalt

7504001911 - Ch-Tr PK230 - Ch-Tr HMB24C - Ta-Tr HMB24B - Ch-Tr TB26B - Am-Sa TB26A - Am TB

45075^- Am-Ca-Ep HMB45068^- Am-Pig-Sa TB45064^- Am-Ch-Ep TB45062^- Ch-Am-Plg TB

Mount Ada Basalt

45092^- Ch-Tr-Ep-Ca TB45086^- Ca-Ch-Ep-Plg TB45076^- Ca-Plg-Ch TB45079^- Ca-Plg-Ch TB

Dolerites in the Duffer Formation

750400463 - Sa-Ch-11 TO43A - Am-Ep TO66C - Il-rich TO

Alex Basalt

49336^- Ch-Tr HMB49325^- Tr-Ch (Ca) TB

Euro Basalt

49344^- Tr-Ch^(Ca, Cl) TB49347^- Ep-Tr-Cl (Sp, Ca) TB49349^- Ca-Ch-Qz (Mt) TB

Charteris Basalt

49271^- Carbonated HMB49261^- Ep-Ca-Ch Tb49269^- Altered TB with relic OL49275^- Epidotized HMB49250^- Ca-Ch (Qz) TB

Honeyeater Basalt

49385^- Serpentinized Cpx HMB49379^- Cpx-bearing TB49375^- Saussuritized (ca) TD49398^- Cpx-bearing porphyritic TB

733

11-2

Warambie Basalt

80040270 -268 -273 -

Am-plg-Opx (Se, Sa, Qx, Ch) TDAm-Pig (So, Ii, Ep) TBCarbonated Plg-Ch-Opx (Mu, Bi) Td

Louden Volcanics

70024^- Cpx-Plg-Ch (Se, Qz, Su) TAP70026^- Cpx-Ch (Pr, Qz, Ca, Su) TAP70022^- Plg-Am-Ch-Qz-Ca (Su) TBA

Negri Volcanics

700017001270009331/337331/338331/339

- Am-Ch-Sa-Qz (Su) TAP- Am-Plg-Ch-Sa-Qz (Ep, Ca, Su) TBP- Plg-Am-Ch-Qz-Ep-Ca-Sa (Su) TBA- Spinifex-textured high-Mg basalt- Spinifex-textured high-Mg basalt- Spinifex-textured high-Mg basalt

Mt Roe Basalt

68932^- Sa-Se-Ch-Ca-Sp-Qz TB68963^- Ch-Se-Sa-Ca-Sp (Su) TB68951^- Ch-Ca-Sp-Sa-Se (Qz, Pig, Su) TBA69031^- Ch-Sa-Plg-Qz (Sp, Hm) TA68947^- Ch-Plg-Ca-Sp (Su, Se) TA

Kylena Basalt

8004011^- Plg-Ch-Cpx-Sa-Bi-Lx-Ca TA0114^- Plg-Ch-Sa-Cpx-Ca TB0122^- Sa-Plg-Ch-Cpx-Ca-Ep-Sp-Opx-Se TB0117^- Sa-Plg-Ch-Cpx-Ca-Ep-Sp-Opx TB

Nymerina Basalt

80040130^- Plg-Cpx-Ch-Ca-Opx HMBP0134^- Plg-Sa-Ch-Ca-Sp-Lx TB0131^- Pig-Ca-Ch-Opx-Ep-Sp TBA

Maddina Basalt

80040140 - Ca-Sa-Ch-Pz-Am-Lx-Ta TB0141^

- Sa-Ch-Plg-Cpx-Sp-Lx-Pr-Ta TB0147^

- Sa-Ch-Plg-Cpx-Sp-Lx-Pr-Ta TA0143^

- Sa-Ch-Plg-Cpx-Sp-Lx-Pr-Ta TA

81

11-3

Symbols

Am -ÂmphiboleCa -^CarbonateCh^-^ChloriteCpx -^ClinopyroeneEp^-ÊpidoteIi^-ÎlmeniteLx^-^LeucoxeneMt -^Magnetite01^-ÔlivineOpx -ÔrthopyroxenePr^-^PrehnitePlg -^PlagioclaseQz^-^QuartzSa^-^SaussuriteSe^-^SericiteSp^-^SpheneSu^-^SulphideTa -^TalcTr^Tremolite

PK^-^Peridotitic komatiiteHMB -^High-Mg basaltHMBP -^High-Mg basalt (porphyritic)TB^-^Tholeiitic basaltTBPTholeiitic basalt (porphyritic)TBA —^Tholeiitic basalt (amygdaloidal)TD 7^Tholeiitic basaltTA^-^Tholeiitic andesiteTAP -^Tholeiitic andesite (porphyritic)

e a s (i y eeme eouio ay gikso c ie a ueau o miea esouces ... · ueau o miea esouces geoogy a ......

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