detailed geochemistry and k-ar geochronology of the...

Detailed Geochemistry and K-Ar Geochronology of the MetamorphicSole Rocks and Their Mafic Dykes from the Mersin Ophiolite,

Southern Turkey

ÖMER FARUK ÇELİK

Kocaeli Üniversitesi, Mühendislik Fakültesi, Jeoloji Mühendisliği Bölümü, TR–41380 Kocaeli, Turkey

(e-mail: [email protected])

Abstract: The metamorphic sole rocks at the base of mantle peridotites from the Mersin ophiolite consist of amphibolites andmetasedimentary lithologies. Mineral parageneses in the metamorphic sole rocks exhibit amphibolite and greenschist faciesassemblages. Geothermobarometric studies based on mineral assemblages and chemical compositions of minerals indicate thataverage metamorphic temperature during the metamorphism was 522 ± 15 °C and the pressure was less than 5 kb. Amphibolitesfrom the metamorphic sole rocks exhibit geochemical characteristics of a supra-subduction zone (SSZ) type ophiolite, based on theirmajor, trace and rare earth element (REE) compositions. The Th/Nb ratios of the amphibolites are higher than the average mid-oceanridge basalt (MORB) and ocean island basalt (OIB) values. This may suggest that they were probably derived from an enriched mantlesource modified by the addition of subduction component. Island arc tholeiite (IAT), OIB and MORB-like geochemistry of theamphibolites suggest that protoliths of these rocks were formed in a SSZ environment similar to the South Sandwich arc-basinsystem from South Atlantic ocean and the Mariana Trough from the Western Pacific. Isolated dolerite dykes intrude both themetamorphic sole rocks and the ophiolitic units at different structural levels. Dolerite dykes cutting the metamorphic sole rocksexhibit IAT-like geochemistry. They are enriched in large-ion-lithophile elements (LILE), depleted in high-field-strength elements(HFSE) and have relatively flat REE patterns, which also confirm their subduction-related origin. Double subduction is inferred hereto explain the generation of the metamorphic sole rocks and dykes in the Neotethyan ocean, since the metamorphic sole rocks exhibitSSZ characteristics and were intruded by unmetamorphosed IAT-like dolerite dykes.

Key Words: ophiolite, geochemistry, metamorphic rock, dyke, East Mediterranean, Neotethys

Mersin Ofiyolitinden Metamorfik Taban Kayaçları ve Mafik Daykların Ayrıntılı Jeokimyası ve K-Ar Jeokronolojisi, Güney Türkiye

Özet: Mersin ofiyolitine ait manto peridotitlerinin tabanında yer alan metamorfik taban kayaçları amfibolitlerden ve metasedimanterlitolojilerden meydana gelir. Metamorfik taban kayaçları içerisindeki mineral birliktelikleri, bu kayaçların amfibolit ve yeşilşist fasiyesitoplulukları olduğunu gösterir. Mineral topluluklarına ve minerallerin kimyasal bileşimlerine dayalı jeotermobarometre çalışmaları,metamorfizma esnasındaki metamorfik sıcaklığın 522 ± 15 °C ve basıncın 5 kb’dan az olduğuna işaret eder. Metamorfik tabankayaçlarından amfibolitlerin ana, iz ve nadir toprak elementleri bileşimlerine dayalı jeokimyası, bu kayaçların Yitim Zonu Üstü (SSZ)tipi ofiyolitlerin jeokimyasal özelliklerine sahip olduklarını gösterir. Amfibolitlerin Th/Nb oranları, ortalama değer Okyanus Ortası SırtıBazaltlarından (MORB) ve Okyanus Adası Bazaltlarından (OIB) yüksektir. Bu durum muhtemel olarak bu kayaçların yitim bileşenininetkisiyle zenginleşen manto kaynağının değişmesi sonucu oluştuklarını gösterir. Amfibolitlerin Adayayı Toleyitleri (IAT), OIB ve MORBbenzeri jeokimyası, bu kayaçların köken kayaçlarının Yitim Zonu Üstü ortam koşulları içerisinde oluştuklarını ve Batı PasifiktekiMariana Trough ve Güney Atlantik Okyanusunda, Güney Sandwich yay-basen sistemlerine benzerlik sunduklarını gösterir. İzole doleritdaykları, metamorfik taban kayaçlarına ve ofiyolitik üniteye farklı yapısal seviyelerde sokulum yaparlar. Metamorfik taban kayaçlarınıkesen dolerit daykları Adayayı Toleyitleri benzeri jeokimya gösterirler. Bu kayaçlar LIL elementler bakımından zenginleşmişler bunakarşın HFS elementler bakımından tüketilmişlerdir. Dolerit dayklarının göreceli düz nadir toprak elementleri gidişleri de bu kayaçlarınyitim ile ilişkili kökenlerini teyit eder. Metamorfik taban kayaçlarının SSZ özelliklerini göstermeleri ve metamorfik olmayan AdayayıToleyitleri benzeri dolerit daykları tarafından kesildikleri için Neotetis Okyanusunda dayklar ve metamorfik taban kayaçlarınıngelişimini açıklamak için çift yitim sonucuna varılır.

Anahtar Sözcükler: ofiyolit, jeokimya, metamorfik kayaç, dayk, Doğu Akdeniz, Neotetis

Introduction

The Tauride belt, as part of the Alpine-Himalayanmountain system, is one of the best regions to observethe metamorphic sole rocks and remnants of Cretaceousophiolites generated from the Neotethyan ocean. The

ophiolites in this belt (Figure 1a) are located as dispersedslices on both sides of the Mesozoic Tauride platformcarbonates (Dilek & Moores 1990; Juteau 1980). Theydo not exhibit a complete ophiolite stratigraphy. Thedeeper parts, such as tectonites, are the best preserved

685

Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol. 17, 2008, pp. 685–708. Copyright ©TÜBİTAKFirst published online 07 April 2008

GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY

686

Tauride platformcarbonates

metamorphic sole

podiformchromite

(harzburgite, dunite)

dolerite dyke

alternation of dunite,wehrlite and pyroxenite

plagiogranite

petrological Moho

pillow lavas

dunite

mantle tectonites

upperpartoftheMSR

(mostlyamphibolite)

lowerpartoftheMSR

(mostlymeta-pelite)

banded chromiteseismic Moho

neo-autochthonous

amphibole-mica-schist(hb+pl+bt+mu+qtz+opq)

micaschist(pl+bt+mu+qtz+opq)

chlorite-calcite-schist(qtz+ep+chl+cal+opq)

amphibolite(hb+pl+px+ep+bt+qtz+opq+spn+ap)

amphibolite(hb+pl+spn)

amphibolite(hb+pl+bt-mu+spn-ap)


quartzite(qtz+pl+ep+chl+bt+mu+opq)


epidote-amphibolite(hb+pl+ep+bt+qtz+spn-ap)

calc-schist(qtz+ep+chl+cal+opq)

epidote-amphibolite(hb+pl+ep+bt+qtz+spn-ap)

c

gabbroic cumulates(olivine-gabbro, gabbro,leuco-gabbro)

0 10 km

N

coversedimentsophiolitemetamorphicsole rocks

basement

Mediterranean Sea

Mersin

M-76

M-88

M-148

M-167

Aslanköy

melange

melangeophiolitic

Fındıkpınarı

Şahna

thrust fault

strike-slip fault

M-168

M-178

b

a

Kızıldağophiolite

M e d i t e r r a n e a n S e a

KarpathosKöyceğiz

Rhodes

AegeanSea

Lycianophiolites

Yeşilova38o

42oN 31 oE 39o

B l a c k S e a

Antalyaophiolite ophiolite

Beyşehir

ophioliteMersin

TroodosCyprus

EF

Ankara

TuzLake

Upper Cretaceousophiolites

0 160km

NAHO

PKOPO

DO

EAFZ

LakeVan

DSF

İstanbul

İAES

NAFZ

ArabianPlatform

Southeast An

atolian Suture

T a u r i dr b

e C a o n a t eP l a

t fo r

m

T a u r i dr b

e C a o n a t eP l a

t fo r

m

Figure 1. (a) Generalized map, modified after Dilek & Moores (1990), showing the distribution of theTauride Belt Ophiolites and the main tectonic subdivisions of Turkey. Inset: İAES– İzmir-Ankara-Erzincan suture; NAFZ– North Anatolian Fault Zone; EAFZ– East Anatolian Fault Zone; EF– EcemişFault; DSF– Dead Sea Fault; AHO– Alihoca ophiolite; PKO– Pozantı-Karsantı ophiolite; PO–Pınarbaşı ophiolite; DO– Divriği ophiolite; (b) simplified geological map of the Mersin ophiolite andthe location of the samples from the metamorphic sole rocks, modified after Parlak & Delaloye(1999); (c) synthetic log of the Mersin ophiolitic complex, modified from Parlak et al. (1996),and the rock types of the metamorphic sole rocks (MSR). Mineral abbreviations: hb– hornblende;pl– plagioclase; px– pyroxene; ep– epidote; bt– biotite; mu– muscovite; qtz– quartz; chl– chlorite;spn– sphene; ap– apatite; cal– calcite; opq– opaque mineral.

and in the upper parts of the assemblage, sheeted dykeshave generally disappeared. However, all these ophiolitescontain metamorphic sole rocks and mélange units, and allthese ophiolites, including the metamorphic sole rocks,are cross-cut by dolerite, gabbro and pyroxenite dykes.The isolated dolerite dykes cutting the metamorphic solerocks are neither folded nor metamorphosed. Therefore,dyke injection has been interpreted to have occurred in anoceanic environment prior to obduction of oceanic crustonto the Tauride platform carbonates but after ductiledeformation of the metamorphic sole rocks (Lytwyn &Casey 1995; Parlak & Delaloye 1996; Dilek et al. 1999;Çelik & Delaloye 2003).

The metamorphic sole rocks and the dykes cuttingdifferent parts of the ophiolites provide useful constraintson the age of intra-oceanic subduction and thetectonomagmatic evolution of the ophiolites in an oceanicenvironment. The metamorphic sole rocks from theTauride Belt ophiolites are tectonically located betweenmantle peridotites and a mélange unit (Figure 1c), but canbe also observed in the mélange unit as blocks of differentsizes (Çelik & Delaloye 2006). The cooling and/orformation ages of the metamorphic sole rocks from theTauride Belt ophiolites range from 91 to 93 Ma, based on40Ar-39Ar geochronology (Dilek et al. 1999; Parlak &Delaloye 1999; Çelik et al. 2006). General characteristicsof the metamorphic sole rocks from the Tauride Beltophiolites are summarized in Table 1.

There are different arguments in the literature for theintra-oceanic subduction/obduction events controlling theorigin of the Tauride Belt ophiolites and their metamorphicsole rocks. For example, Lytwyn & Casey (1995) and Dileket al. (1999) suggested that the generation of the TaurideBelt ophiolites occurred along a mid-ocean ridge system inthe Neotethyan ocean. However, many authors (e.g.,Pearce et al. 1984; Parlak et al. 1996, 2000, 2002, 2006;Robertson 2002; Bağcı & Parlak 2006; Çelik et al. 2006)argued that generation of the ophiolites occurred in asupra-subduction zone (SSZ) environment. Also, theoccurence of the metamorphic sole rocks and their dykeswas mostly explained by subduction of a single oceaniclithosphere in the Neotethyan ocean (Lytwyn & Casey1995; Polat et al. 1996; Parlak & Delaloye 1996, 1999;Önen & Hall 2000). Parlak et al. (1995) reported that,while the metamorphic sole rocks of the Mersin ophioliteexhibit within plate basalt characteristics (WPB), thedolerite dykes crosscutting the metamorphic sole rocks, as

well as the Mersin ophiolite itself, present island arctholeiite (IAT) affinities.

Backarc basins, such as the Lau and Mariana Troughfrom the SSZ systems of the Western Pacific ocean have arange of rock compositions that, in addition to normal mid-ocean ridge basalts (N-MORB), include IAT, backarc basinbasalts (BABB), and enriched basalts that comprise oceanisland basalt (OIB), as well as fractionated rocks of theseseries (Gribble et al. 1988, 1996; Hawkins 1995a, b,2003). A similar geochemical range, from MORB to IAT,was also observed in the South Sandwich arc-basin systemof South Atlantic ocean (Pearce et al. 2000; Leat et al.2004). Accordingly, the SSZ would be a potential area togenerate metamorphic sole rocks having a variety ofgeochemical characteristics.

This study presents geochemical and petrologicalcharacteristics of the metamorphic sole rocks and theirdykes from the Mersin ophiolite. The aim of this study isto discuss possible generation of the metamorphic solerocks in a supra-subduction zone environment.

Geological Setting

The Mersin ophiolite complex, located in the CentralTauride belt of Turkey, crops out over an area 60 km long,25 km wide. It is separated from the Eastern Tauride belt(e.g., Pozantı-Karsantı ophiolite) by the left-lateral Ecemişfault (Figure 1a). The Mersin ophiolite complex (~ 6 kmthickness), comprises, from bottom to top (Figure 1c), theMersin ophiolitic mélange, the metamorphic sole rocks andthe Mersin ophiolite. It tectonically overlies Mesozoicplatform carbonates (Juteau 1980; Dilek & Moores 1990;Parlak 1996; Parlak et al. 1996).

The Mersin ophiolitic mélange consists ofconglomerates, sandstones, shales, mudstones,radiolarites, blocks of Permian to Cretaceous limestones,serpentinized harzburgites, gabbros, basalts, fragments ofmetamorphic sole rocks and granitic blocks (Parlak 1996;Parlak & Delaloye 1996, 1999; Parlak & Robertson2004).

The metamorphic sole rocks, composed mainly ofamphibolites and micaschists (Table 2), are tectonicallylocated between the mantle tectonites and the Mersinophiolitic mélange. Highly folded and faulted, themetamorphic sole rocks at the base of the mantletectonites have a thickness of about 100 m. They crop out

Ö.F. ÇELİK

687


688

Oph

iolit

eM

etam

orph

ic s

ole

Stru

ctur

al p

ositi

on o

f m

etam

orph

ic s

ole

Age

of m

etam

orph

ic s

ole

(Ma)

Prot

olith

Maf

ic d

yke

cutt

ing

met

amor

phic

sol

eAg

e of

maf

ic d

ykes

LYCI

AN

OPH

IOLI

TE

garn

et-a

mph

ibol

ite, p

yrox

ene-

amph

ibol

ite, a

mph

ibol

ite,

epid

ote-

amph

ibol

ite, k

yani

te-

garn

et-

mic

asch

ist,

mic

asch

ist,

m

arbl

e, q

uart

zite

, (Çe

lik &

D

elal

oye

2003

)

tect

onic

ally

loca

ted

both

at

the

base

of

the

peri

dotit

es

and

in t

he m

élan

ge, ~

30

0–35

0 m

thi

ckne

ss

(Çel

ik &

Del

aloy

e 20

03)

40Ar

-39Ar

age

s fr

om K

öyce

iz a

rea

(Çel

ik e

t al

. 20

06);

93.

1±0.

9 (h

ornb

lend

e) -

93.

0±0.

9

(hor

nble

nde)

, 91.

7±0.

7 (m

usco

vite

) -

93.6

±0.

8 (m

usco

vite

). 40

Ar-39

Ar a

ges

from

Ye

ilova

are

a (Ç

elik

et

al. 2

006)

; 90.

07±

0.5

(hor

nble

nde)

- 9

1.3±

0.9

(hor

nble

nde)

, 91

.2±

2.3

(mus

covi

te)

amph

ibol

ites:

alk

alin

e (O

IB)

and

thol

eiiti

c ba

salti

c ro

cks

(MO

RB,

IA

T). m

icas

chis

t: g

reyw

acke

s,

lithi

c sa

ndst

ones

, (Çe

lik 2

002;

Çe

lik &

Del

aloy

e 20

03)

dole

rite

dyk

es (

IAT)

(Ç

elik

& D

elal

oye

2003

)

K-A

r ag

es, r

angi

ng f

rom

63

.6±

1.6

to

90.3

3±2.

7 (Ç

elik

200

2; Ç

elik

&

Chia

radi

a, 2

008)

ANTA

LYA

OPH

IOLI

TE

pyro

xene

-am

phib

olite

, am

phib

olite

, epi

dote

-am

phib

olite

, (Çe

lik &

Del

aloy

e 20

03)

tect

onic

ally

loca

ted

in t

he

mél

ange

uni

t (Ç

elik

&

Del

aloy

e 20

03)

40Ar

-39Ar

age

s fr

om a

mph

ibol

ites

(Çel

ik e

t al

. 20

06);

93.

0±1.

0 (h

ornb

lend

e), 9

3.8±

1.7

(hor

nble

nde)

amph

ibol

ites:

alk

alin

e (O

IB)

and

thol

eiiti

c ba

salti

c ro

cks

(IAT

),

(Çel

ik &

Del

aloy

e 20

03)

abse

ntab

sent

BEY

EHR

-H

OYR

AN

OPH

IOLI

TE

garn

et-a

mph

ibol

ite, p

yrox

ene-

amph

ibol

ite, a

mph

ibol

ite,

epid

ote-

amph

ibol

ite, c

alc-

schi

st, q

uart

zite

, (Çe

lik &

D

elal

oye

2006

)

tect

onic

ally

loca

ted

both

at

the

base

of

the

peri

dotit

es

and

in t

he m

élan

ge (

Elito

k 20

01; Ç

elik

& D

elal

oye

2006

)

40Ar

-39Ar

age

s fr

om a

mph

ibol

ites

(Çel

ik e

t al

. 20

06);

90.

9±1.

3 (h

ornb

lend

e), 9

1.5±

1.9

(hor

nble

nde)

amph

ibol

ites:

alk

alin

e (O

IB)

and

thol

eiiti

c ba

salti

c ro

cks

(MO

RB)

, (Ç

elik

& D

elal

oye

2006

)

mic

roga

bbro

and

do

leri

te d

ykes

(IA

T),

(Elit

ok 2

001)

abse

nt

POZA

NTI

-K

ARSA

NTI

O

PHIO

LITE

pyro

xene

-am

phib

olite

, am

phib

olite

, bio

tite-

amph

ibol

ite, e

pido

te-

amph

ibol

ite, g

arne

t-ky

anite

-am

phib

ole

mic

asch

ist,

m

icas

chis

t, q

uart

zite

, (D

ilek

et

al. 1

999;

Lyt

wyn

& C

asey

19

95; P

olat

& C

asey

199

6;

Çelik

200

7)

tect

onic

ally

loca

ted

both

at

the

base

of

the

peri

dotit

es

and

in t

he m

élan

ge, ~

40

0–50

0 m

thi

ckne

ss

(Lyt

wyn

& C

asey

199

5;

Pola

t &

Cas

ey 1

996;

Dile

k et

al.

1999

; Çel

ik 2

007)

40Ar

-39Ar

age

s fr

om a

mph

ibol

ites

(Dile

k et

al.

1999

)[4]

; 91.

7±1.

2 (h

ornb

lend

e), 9

0.4±

1.8

(hor

nble

nde)

. 40 Ar

-39Ar

age

s fr

om m

icas

chis

t (Ç

elik

et

al. 2

006)

; 92.

4±1.

3 (m

usco

vite

)

amph

ibol

ites:

alk

alin

e (O

IB)

and

thol

eiiti

c ba

salti

c ro

cks

(MO

RB

and

IAT)

. mic

asch

ist:

lith

ic

sand

ston

es (

Çelik

200

7)

dole

rite

(IA

T), a

nd

pyro

xeni

te d

ykes

(O

IB),

(Ç

elik

200

7)

K-A

r ag

es f

rom

dol

erite

dy

kes

(Thu

izat

et

al. 1

981)

; 71

±3

(pla

gioc

lase

). K

-Ar

(who

le r

ock)

age

s fr

om

dole

rite

dyk

es (

Çelik

200

2);

betw

een

69.2

±2.

1 -

83.3

±2.

2

PIN

ARBA

I O

PHIO

LITE

amph

ibol

ite, p

lagi

ocla

se

amph

ibol

ite, a

mph

ibol

e sc

hist

, ep

idot

e-pl

agio

clas

e-am

phib

ole-

schi

st, c

alcs

chis

t, (

Verg

ili &

Pa

rlak

200

5)

tect

onic

ally

loca

ted

both

at

the

base

of

the

peri

dotit

es

and

in t

he m

élan

ge (

Verg

ili

& P

arla

k 20

05)

K-A

r ag

es f

rom

am

phib

olite

s (V

ergi

li &

Par

lak

2005

); 1

02.2

±2.

9 (h

ornb

lend

e), 1

07.3

±3

(hor

nble

nde)

amph

ibol

ites:

OIB

and

IAT

(Ver

gili

& P

arla

k 20

05)

mic

roga

bbro

-dia

base

dy

kes

(IAT

) (V

ergi

li &

Pa

rlak

200

5)ab

sent

DVR

O

PHIO

LITE

amph

ibol

ite, p

lagi

ocla

se

amph

ibol

ite, p

lagi

ocla

se-

amph

ibol

e sc

hist

, pla

gioc

lase

-ep

idot

e-am

phib

ole-

schi

st,

calc

schi

st, (

Parl

ak e

t al

. 200

6)

the

met

amor

phic

sol

e lie

s be

twee

n m

antle

tec

toni

tes

and

mél

ange

. ~ 1

00–4

00

m t

hick

ness

(Pa

rlak

et

al.

2006

)

abse

ntam

phib

olite

s: a

lkal

ine

(OIB

) an

d th

olei

itic

(IAT

) (P

arla

k et

al.

2006

).

dole

rite

dyk

es w

ith

alka

line

affin

ity (

OIB

) (P

arla

k et

al.

2006

)ab

sent

Tabl

e 1.

Geo

logi

cal a

nd g

eoch

rono

logi

cal r

esul

ts f

rom

the

met

amor

phic

sol

e ro

cks

and

cros

s-cu

ttin

g m

afic

dyk

es o

f th

e Ta

urid

e Be

lt O

phio

lites

.

Ö.F. ÇELİK

689

Tabl

e 2.

M

iner

al a

ssem

blag

es a

nd t

extu

res

in t

he m

etam

orph

ic s

ole

rock

s an

d m

afic

dyk

es o

f th

e M

ersi

n op

hiol

ite.

Sam

ple

Roc

k ty

peTe

xtur

eam

ppx

plqt

zep

btm

uch

lca

lsp

nap

opq

M-7

6am

phib

olite

nem

atob

last

icX

XX

M-7

7do

leri

tesu

b-op

hitic

XX

XX

XM

-78

amph

ibol

itede

cuss

ate

XM

-79

calc

schi

stgr

anol

epid

obla

stic

XX

XX

XX

M-8

0ep

idot

e-am

phib

olite

gran

onem

atob

last

icX

XX

*XX

M-8

1am

phib

ole-

quar

tz-m

icas

chis

tgr

anol

epid

obla

stic

XX

XX

XX

M-8

2do

leri

tesu

b-op

hitic

XX

*XX

XX

M-8

3am

phib

olite

nem

atob

last

icX

XX

*XX

M-8

4ep

idot

e-am

phib

olite

nem

atob

last

icX

XX

*XX

M-8

5ep

idot

e-am

phib

olite

nem

atob

last

icX

XX

XX

XX

XM

-86

dole

rite

mic

ro-g

ranu

lar

XX

XX

X*X

XM

-87

dole

rite

mic

ro-g

ranu

lar

XX

XX

XX

M-8

8ch

lori

te-c

alci

te-s

chis

tgr

anon

emat

obla

stic

XX

XX

XM

-148

epid

ote-

amph

ibol

itene

mat

opor

phyr

obla

stic

XX

XX

XM

-149

dole

rite

sub-

ophi

ticX

XX

M-1

50do

leri

tesu

b-op

hitic

XX

X*X

XX

XM

-151

amph

ibol

itegr

anob

last

icX

X*X

XX

XM

-152

amph

ibol

itegr

anob

last

icX

XX

XX

M-1

53am

phib

olite

nem

atob

last

icX

XX

XX

XX

M-1

54am

phib

olite

gran

obla

stic

XX

*XX

XM

-155

amph

ibol

itegr

anob

last

icX

XX

XM

-156

amph

ibol

itene

mat

obla

stic

XX

*XX

XM

-157

amph

ibol

itene

mat

obla

stic

XX

XX

XX

XM

-158

amph

ibol

itene

mat

obla

stic

XX

*XX

*XM

-159

amph

ibol

itegr

anob

last

icX

XX

XX

M-1

60ep

idot

e-am

phib

olite

gran

onem

atob

last

icX

XX

XX

XM

-161

amph

ibol

itegr

anob

last

icX

X*X

*X*X

*XX

XM

-162

amph

ibol

itegr

anob

last

icX

XX

M-1

63am

phib

olite

gran

obla

stic

XX

XX

M-1

64am

phib

olite

nem

atob

last

icX

XX

XX

XM

-165

amph

ibol

itegr

anon

emat

obla

stic

XX

XM

-166

amph

ibol

itene

mat

obla

stic

XX

*XX

XM

-167

amph

ibol

itene

mat

obla

stic

XX

XX

M-1

68am

phib

olite

gran

onem

atob

last

icX

XX

XM

-169

amph

ibol

itegr

anon

emat

obla

stic

XX

XX

M-1

70am

phib

olite

gran

obla

stic

XX

XX

M-1

71am

phib

olite

gran

obla

stic

XX

XM

-172

amph

ibol

itegr

anob

last

icX

XX

M-1

73am

phib

olite

gran

obla

stic

XX

*XX

M-1

74am

phib

olite

gran

obla

stic

XX

XM

-175

amph

ibol

itegr

anob

last

icX

X*X

XX

M-1

76am

phib

olite

gran

obla

stic

XX

X*X

XX

XM

-177

amph

ibol

itegr

anob

last

icX

X*X

*XX

XM

-178

amph

ibol

itegr

anob

last

icX

XX

X

* in

dica

ting

seco

ndar

y m

iner

al d

evel

opm

ent

(mos

tly in

vei

ns).

in the localities of Fındıkpınarı, Şahna and Arslanköy(Figure 1b).

The Mersin ophiolite consists of, from bottom to top,tectonized peridotites (harzburgites and dunites),ultramafic cumulates (dunite, wehrlite and pyroxenite),mafic layered cumulates (olivine gabbro, gabbro,leucogabbro and anorthosite), isotropic gabbros and minorplagiogranites, and alkaline to tholeiitic basaltic volcanicsin association with deep marine sediments (Parlak 1996)(Figure 1c). The contacts in the Mersin ophiolite andsurrounding units are all tectonic. Doleritic and gabbroicdykes cutting the entire ophiolite sequence and themetamorphic sole rocks do not cut the ophiolitic mélangeand the platform carbonates. The Mersin ophiolite isunconformably overlain by Late Paleocene sediments(Avşar 1992).

Analytical Methods

Major and trace element analyses (Table 3) were carriedout by XRF spectrometry at Lausanne University.Compositions were determined using glass beads fused ina gold-platinum crucible at 1150 °C made from ignitedpowders to which Li2B4O7 had been added in a 1:5proportion of rock to flux. Rare earth elements wereanalysed by inductively coupled plasma mass spectrometry(ICP-MS) at Actilabs, in Ancaster, Ontario). Detection limits(ppm) and Analytical Uncertainty (%) of the followingelements are: Sc (1.2 ppm, 6.6%), V (1.2 ppm, 3.1%),Cr (1.1 ppm, 7.4%), Co (1 ppm, 19.4%), Ni (0.9 ppm,8.1%), Cu (1.1 ppm, 19.6%), Zn (1.1 ppm, 3.8%), Ga(0.5 ppm, 9.2%), Rb (0.6 ppm, 3.1%), Sr (0.8 ppm,3.4%), Y (0.8 ppm, 1.6%), Zr (0.7 ppm, 2.4%), Nb (0.6ppm, 5.8%), Ba (7 ppm, 11.4%), Hf (0.7 ppm, 16.6%),Pb (1.1 ppm, 8.2%), Th (1.4 ppm, 5.7%), U (0.7 ppm,22.6%).

Mineral analyses were performed on a Cameca SX50electron microprobe at University of Lausanne equippedwith wavelength dispersive spectrometry. Operatingconditions were 15kV accelerating voltage and 15 nAsample current. Counting times of 10–30 s were applied.The amphibole analyses were re-calculated by using aspreadsheet program of Tindle & Webb (1994). Resultsof mineral analyses are given in Tables 4–7.

K-Ar age measurements were performed at the GenevaUniversity (Switzerland) Mineralogy Department. Theextracted minerals were obtained by magnetic separation,

heavy liquids and hand picking under a binocularmicroscope in order to produce high-purity mineralseparates (>99%). Potassium concentrations weremeasured twice using atomic absorption (Pye-Unicam8000). The values reported in Table 8 are therefore theaverage of the duplicate measurements. Isotope analyses ofargon were made using isotope dilution on an AEI-10-Smass spectrometer. Constants were those recommendedby Steiger & Jäger (1977). LP-6 and HD-B1 internationalstandards were used for calibration of the massspectrometer response.

Mineralogy and Petrography

The upper part of the metamorphic sole rocks (close to themantle tectonites) consists mainly of amphibolites, whereasthe lower part comprises mica schists, calcschists, marbleand quartzite. The mica schists were also observed as smallslices within the amphibolites, as observed in the Pozantı-Karsantı and Lycian ophiolites (Çelik 2002, 2007; Çelik &Delaloye 2003). The foliation in the amphibolites iscommon and defined by subparallel alignment ofamphibole-epidote and amphibole-plagioclasecrystalloblasts. The commonest textures of theamphibolites are granoblastic, nematoblastic andgranonematoblastic.

Based on the classification of Leake et al. (1997), allamphiboles in the amphibolites and dolerite dykes are calcicamphiboles. Amphibole compositions (edenite andmagnesio-hornblende) from the amphibolites arecharacterized by SiO2= (44.8–46.8 %), Al2O3= (8.7–11.1%), FeO= (12.7–14.7 %), MgO= (11.5–12.7 %) andK2O= (0.5–0.8 %). XMg values (Mg/Mg+Fe+2) ofamphiboles range from 0.58 to 0.67 (Table 4). Pyroxenein the amphibolites (M-178) was observed asequidimensional crystalloblasts. In sample (M-178) it isrepresented by diopside with Al (0.08–0.1 a.p.f.u.) and Na(0.04 a.p.f.u.) contents and a higher Si content (1.95–1.97 a.p.f.u.). Titanite and apatite are the most abundantaccessory minerals in the parageneses. Titanite wascommonly observed along the foliation planes and asinclusions in the amphibole crystalloblasts. It is also parallelto the lineation orientation of the amphibole crystalloblastand may be developed during the deformation stage of themetamorphic sole rocks. Plagioclase is commonly altered tosaussurite and sericite and generally lacks polysynthetictwinning. Plagioclases from the amphibolite (M-154) have


690

Ö.F. ÇELİK

691

Tabl

e 3.

Chem

ical

ana

lyse

s of

am

phib

olite

s. m

eta-

pelit

es a

nd d

oler

ite d

ykes

fro

m t

he m

etam

orph

ic s

ole

rock

s of

the

Mer

sin

ophi

olite

.

Sam

ple

M-7

6M

-78

M-8

0M

-83

M-8

5M

-148

M-1

51M

-153

M-1

54M

-157

M-1

59M

-164

M-1

65M

-168

M-1

70M

-171

M-1

75M

-176

M-1

78R

ock

type

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

amp

SiO

245

.82

41.7

037

.32

44.0

735

.94

43.6

344

.97

45.0

344

.93

46.6

244

.36

46.8

444

.71

43.9

243

.26

44.5

243

.52

45.0

243

.72

Al2O

311

.09

11.0

013

.47

11.5

912

.40

13.7

211

.47

15.3

011

.50

16.0

411

.81

15.5

811

.96

11.9

312

.28

12.7

312

.06

13.2

511

.96

TiO

22.

301.

152.

261.

692.

093.

222.

873.

392.

903.

273.

032.

493.

022.

612.

592.

492.

393.

412.

58Fe

2O3(

T)*

12.4

514

.26

9.98

11.3

19.

9013

.80

13.9

114

.39

13.5

914

.03

14.4

813

.04

13.7

913

.85

14.5

713

.80

13.4

613

.13

14.0

6M

nO0.

190.

200.

160.

140.

160.

190.

180.

180.

180.

170.

180.

170.

190.

190.

230.

200.

200.

250.

19M

gO12

.45

18.0

84.

579.

277.

619.

4410

.64

7.56

10.6

85.

8510

.36

7.62

10.3

311

.14

10.5

810

.41

11.7

96.

8311

.53

CaO

12.3

78.

0724

.01

14.8

917

.03

11.5

411

.59

7.87

11.9

77.

2511

.39

8.76

12.2

812

.14

11.9

211

.43

11.8

112

.29

12.0

4N

a 2O

1.61

1.10

0.92

2.47

1.38

2.62

2.41

3.73

2.37

4.78

2.53

3.96

2.01

2.18

2.25

2.33

2.25

2.58

2.15

K2O

0.75

0.13

0.15

0.32

1.89

0.45

0.67

0.62

0.52

0.65

0.70

0.71

0.81

0.75

0.87

1.24

0.70

1.86

0.70

P 2O

50.

340.

100.

290.

240.

220.

590.

360.

480.

340.

490.

390.

370.

400.

380.

300.

360.

350.

690.

38Cr

2O3

0.11

0.19

0.05

0.11

0.04

0.05

0.11

0.04

0.11

0.01

0.09

0.02

0.09

0.10

0.10

0.09

0.09

0.04

0.10

NiO

0.06

0.10

0.02

0.07

0.02

0.04

0.03

0.02

0.03

0.01

0.03

0.02

0.03

0.04

0.03

0.04

0.04

0.02

0.04

LOI

0.97

3.66

7.15

4.43

11.8

81.

170.

641.

311.

091.

040.

730.

960.

840.

910.

810.

861.

010.

960.

93To

tal

100.

5199

.74

100.

3310

0.59

100.

5510

0.46

99.8

499

.91

100.

2110

0.22

100.

0910

0.53

100.

4710

0.13

99.7

910

0.49

99.6

610

0.33

100.

37pp

mSc

4451

824

1531

5136

4224

3735

3845

4641

4520

47V

244

214

183

216

188

315

303

262

306

210

318

245

302

276

290

285

278

238

284

Cr77

412

9228

768

430

930

676

223

472

155

620

141

611

694

709

645

678

225

730

Co69

9554

7647

7364

6173

5967

5571

6964

6967

5568

Ni

406

664

150

439

100

270

222

193

234

6421

011

922

426

524

424

726

411

628

3Cu

6442

5280

7294

8353

732

124

5284

8714

210

150

5788

Zn97

102

6893

8811

010

711

110

612

411

510

211

410

512

011

010

611

210

9G

a16

1414

1315

1917

2017

2218

1918

1717

1516

1916

Rb

156

56

338

1413

714

1312

1410

1019

928

9Sr

352

2045

021

415

346

720

843

443

448

737

656

432

927

619

529

924

264

625

8Y

2213

1717

1724

2124

2128

2323

2222

2421

2127

22Zr

159

5020

310

419

220

617

821

617

321

318

913

818

814

915

114

615

331

814

7N

b34

1240

2539

6041

3539

4643

3142

3636

3334

7335

Ba10

115

n.d

5413

620

521

221

587

172

408

229

157

145

130

401

176

1138

104

Hf

n.d

n.d

3n.

d7

n.d

35

24

32

3n.

dn.

dn.

d2

11n.

dPb

1216

68

n.d

57

47

n.d

65

76

66

6n.

d7

Th5

46

46

58

55

46

37

53

55

94

U2

24

22

24

2n.

d2

2n.

d2

2n.

d3

23

2La

24.7

92.

7924

.48

19.4

825

.40

2.64

66.8

9Ce

54.1

68.

7553

.06

39.5

954

.14

8.33

137.

78Pr

6.65

1.26

6.11

4.79

6.18

1.43

15.5

7N

d27

.64

6.25

25.0

220

.16

24.7

47.

9361

.34

Sm5.

872.

055.

384.

565.

162.

9111

.79

Eu1.

830.

761.

881.

331.

510.

933.

17G

d5.

322.

184.

804.

154.

253.

629.

13Tb

0.75

0.36

0.68

0.60

0.60

0.65

1.21

Dy

4.27

2.21

3.84

3.46

3.41

4.52

6.47

Ho

0.79

0.43

0.72

0.63

0.62

0.98

1.14

Er2.

081.

171.

891.

641.

612.

942.

92Tm

0.27

0.16

0.26

0.22

0.22

0.45

0.38

Yb1.

690.

981.

571.

251.

362.

932.

25Lu

0.24

0.14

0.22

0.17

0.19

0.45

0.32

n.d

= n

ot d

etec

ted.

am

p =

am

phib

olite

. * =

Tot

al ir

on e

xpre

ssed

as

Fe2O

3.


692

Tabl

e 3.

(Con

tinue

d)

Sam

ple

M-7

7M

-82

M-8

6M

-87

M-1

49M

-150

M-7

9M

-81

M-8

8R

ock

type

dole

rite

dyk

edo

leri

te d

yke

dole

rite

dyk

edo

leri

te d

yke

dole

rite

dyk

edo

leri

te d

yke

mic

asch

ist

mic

asch

ist

mic

asch

ist

SiO

252

.45

53.5

451

.87

51.3

953

.52

52.0

426

.62

76.0

049

.43

Al2O

315

.92

15.7

615

.13

16.1

115

.86

15.4

61.

629.

0514

.61

TiO

20.

731.

290.

460.

781.

151.

269.

730.

880.

71Fe

2O3 (T

)*9.

9311

.85

8.57

9.87

11.6

711

.58

6.42

5.86

8.96

MnO

0.16

0.18

0.15

0.16

0.19

0.18

0.12

0.06

0.23

MgO

6.38

4.26

8.25

6.19

5.13

5.05

3.42

2.20

5.30

CaO

9.94

7.47

9.47

9.23

8.12

7.67

27.5

00.

937.

77N

a 2O

1.75

3.01

1.49

1.83

2.63

3.37

1.38

1.26

2.98

K2O

0.75

0.90

1.66

1.93

0.99

1.13

2.13

2.51

1.21

P 2O

50.

060.

120.

040.

070.

100.

110.

290.

120.

06Cr

2O3

0.02

0.00

0.05

0.03

0.01

0.01

20.6

40.

010.

02N

iO0.

010.

000.

020.

010.

000.

000.

030.

010.

01LO

I1.

871.

662.

742.

280.

611.

400.

021.

128.

66To

tal

99.9

510

0.04

99.8

999

.87

99.9

999

.26

99.9

110

0.00

99.9

6pp

mSc

4038

3535

4043

n.d

840

V30

236

824

731

637

937

513

294

248

Cr11

816

239

127

2133

280

3814

9Co

5454

5046

5547

4469

42N

i58

1510

659

2131

8636

45Cu

7033

6667

4031

941

28Zn

7091

6372

8988

8568

159

Ga

1518

1315

1617

1112

16R

b24

2031

3925

2546

4931

Sr12

818

262

109

152

163

172

5316

4Y

1927

1621

2627

1419

18Zr

3879

2544

6370

192

114

43N

b2

41

24

431

287

Ba53

174

337

1144

137

129

161

425

168

Hf

36

n.d

n.d

5n.

dn.

d10

n.d

Pb12

810

910

9n.

d14

10Th

3n.

d3

33

n.d

89

n.d

U2

n.d

n.d

32

n.d

102

n.d

La3.

763.

290.

722.

072.

252.

83Ce

6.16

9.84

2.19

5.20

7.15

8.70

Pr0.

991.

660.

370.

891.

241.

48N

d5.

049.

162.

274.

846.

928.

19Sm

1.75

3.25

1.01

1.78

2.56

2.92

Eu0.

571.

030.

400.

660.

860.

95G

d2.

203.

961.

512.

343.

343.

70Tb

0.41

0.71

0.29

0.43

0.61

0.66

Dy

2.93

4.92

2.09

3.12

4.26

4.61

Ho

0.65

1.08

0.47

0.69

0.94

1.01

Er2.

043.

221.

472.

112.

843.

05Tm

0.31

0.48

0.22

0.33

0.43

0.45

Yb2.

093.

251.

522.

152.

883.

03Lu

0.33

0.51

0.23

0.34

0.44

0.47

Ö.F. ÇELİK

693

Tabl

e 4.

Amph

ibol

e an

alys

es f

rom

the

am

phib

olite

s of

the

met

amor

phic

sol

e ro

cks

of t

he M

ersi

n op

hiol

ite.

Sam

ple

M-1

54-1

cM

-154

-3c

M-1

54-4

cM

-154

-5c

M-1

54-5

rM

-154

-5r1

M-1

54-6

cM

-154

-7c

M-1

54-8

cM

-154

-9c

M-1

54-1

0cM

-151

-1c

M-1

51-1

rM

-151

-2c

M-1

51-3

cM

-151

-4c

SiO

245

.98

46.7

146

.04

46.6

146

.29

46.8

46.6

445

.26

46.8

146

.68

46.5

945

.57

45.7

646

.13

45.8

946

.22

TiO

21.

350.

961.

81.

161.

651.

561.

541.

861.

421.

561.

611.

241.

351.

551.

761.

72

Al2O

39.

699.

629.

48.

7810

9.81

9.32

109.

569.

179.

69.

849.

749.

189.

499.

34

Fe2O

3(c)

0.17

1.12

n.d

n.d

n.d

0.76

0.72

n.d

0.79

n.d

0.27

n.d

0.32

1.2

n.d

1.01

FeO

(c)

13

.312

.38

13.6

713

.213

.42

12.7

312

.69

13.7

712

.83

13.4

513

.17

14.2

314

.03

13.5

614

.72

13.5

1

MnO

0.2

0.2

0.2

0.19

0.24

0.2

0.22

0.16

0.16

0.19

0.17

0.23

0.31

0.15

0.3

0.24

MgO

12.3

312

.76

12.3

712

.06

12.3

412

.75

12.6

212

.02

12.5

212

.67

12.5

511

.62

11.7

611

.88

11.5

911

.92

CaO

11.9

211

.91

11.8

611

.94

11.8

411

.98

11.7

11.8

611

.73

11.9

211

.79

11.8

711

.91

11.6

211

.89

11.6

1

Na 2

O

1.

982

2.12

1.75

2.09

1.97

1.92

2.17

1.96

21.

992.

042.

041.

942.

191.

98

K2O

0.62

0.56

0.7

0.55

0.75

0.6

0.71

0.84

0.61

0.72

0.75

0.54

0.53

0.54

0.66

0.55

F

0.

010.

10.

040.

040.

130.

050.

040.

040.

080.

110.

080.

050.

030.

02n.

d0.

09

Cl

0.

030.

02n.

d0.

03n.

d0.

010.

01n.

dn.

d0.

01n.

d0.

010.

020.

02n.

dn.

d

H2O

(c)

2.02

22.

021.

992

2.05

2.03

2.02

2.02

22.

021.

992.

012.

022.

042

O=

Fn.

d0.

040.

020.

020.

050.

020.

020.

010.

030.

040.

030.

020.

010.

01n.

d0.

04

O=

Cl0.

01n.

dn.

d0.

01n.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

dn.

d

Tota

l99

.58

100.

3110

0.21

98.2

810

0.68

101.

2510

0.14

99.9

710

0.45

100.

4310

0.54

99.2

99.7

999

.81

100.

5310

0.15

Si

6.

777

6.81

16.

759

6.93

96.

749

6.76

66.

818

6.67

86.

817

6.82

26.

792

6.76

86.

758

6.8

6.75

16.

786

Ti

0.

149

0.10

50.

198

0.13

0.18

10.

169

0.16

90.

206

0.15

50.

171

0.17

60.

139

0.15

0.17

20.

195

0.19

Al/A

lIV1.

223

1.18

91.

241

1.06

11.

251

1.23

41.

182

1.32

21.

183

1.17

81.

208

1.23

21.

242

1.2

1.24

91.

214

AlVI

0.46

0.46

40.

387

0.47

90.

468

0.43

80.

424

0.41

60.

458

0.40

10.

441

0.49

10.

454

0.39

50.

397

0.40

2

Fe3+

0.01

80.

123

n.d

n.d

n.d

0.08

20.

079

n.d

0.08

6n.

d0.

029

n.d

0.03

60.

133

n.d

0.11

1

Fe2+

1.64

1.50

91.

678

1.64

31.

636

1.53

91.

552

1.69

91.

563

1.64

41.

605

1.76

71.

733

1.67

11.

811

1.65

8

Mn2+

0.02

50.

025

0.02

50.

024

0.03

0.02

50.

027

0.02

0.02

0.02

40.

022

0.02

90.

039

0.01

90.

038

0.02

9

Mg

2.70

82.

773

2.70

72.

675

2.68

12.

747

2.74

92.

643

2.71

82.

759

2.72

62.

572

2.58

92.

612.

543

2.60

9

Ca

1.

883

1.86

1.86

61.

904

1.85

1.85

61.

832

1.87

41.

831

1.86

61.

842

1.88

91.

885

1.83

61.

874

1.82

6

Na

0.56

50.

567

0.60

40.

506

0.59

0.55

30.

545

0.62

10.

554

0.56

70.

561

0.58

70.

583

0.55

60.

625

0.56

5

K

0.11

60.

104

0.13

0.10

50.

139

0.11

0.13

20.

157

0.11

30.

135

0.14

0.10

20.

10.

102

0.12

40.

103

F

0.

004

0.04

80.

020.

021

0.05

90.

024

0.01

80.

017

0.03

80.

049

0.03

50.

023

0.01

50.

012

n.d

0.04

Cl

0.

008

0.00

50.

001

0.00

6n.

d0.

002

0.00

4n.

dn.

d0.

003

0.00

10.

002

0.00

40.

005

n.d

n.d

OH

1.98

81.

948

1.97

91.

972

1.94

11.

974

1.97

91.

983

1.96

21.

949

1.96

41.

976

1.98

11.

984

21.

96

Sum

Cat

#17

.564

17.5

3117

.596

17.4

6717

.575

17.5

1917

.509

17.6

3617

.498

17.5

6817

.543

17.5

7617

.568

17.4

9317

.606

17.4

94

X Mg

0.62

30.

648

0.61

70.

619

0.62

10.

641

0.63

90.

609

0.63

50.

627

0.62

90.

593

0.59

90.

610.

584

0.61

1

n.d

= n

ot d

etec

ted.

(c)

= c

alcu

late

d. c

= c

ore.

r =

rim

.


694

Tabl

e 4.

(Con

tinue

d)

Sam

ple

M-1

51-5

cM

-151

-6c

M-1

51-7

cM

-178

-1c

M-1

78-2

cM

-178

-3c

M-1

78-4

cM

-178

-5c

M-1

78-6

cM

-178

-7c

Min

eral

amph

ibol

eam

phib

ole

amph

ibol

eam

phib

ole

amph

ibol

eam

phib

ole

amph

ibol

eam

phib

ole

amph

ibol

eam

phib

ole

SiO

246

45.6

545

.31

45.2

846

.66

45.8

445

.44

44.8

845

.32

45.4

9

TiO

21.

811.

651.

951.

871.

822.

042.

081.

961.

881.

86

Al2O

39.

679.

659.

959.

949.

6610

.49

10.6

311

.11

10.0

310

.71

Fe2O

3(c)

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

3.07

n.d

FeO

(c)

14

.41

14.4

914

.48

13.3

112

.58

13.3

612

.72

13.1

310

.92

13.1

4

MnO

0.19

0.26

0.15

0.22

0.12

0.26

0.24

0.2

0.28

0.21

MgO

11.6

311

.45

11.4

812

.19

12.5

712

.28

12.3

411

.95

12.5

512

.42

CaO

12.0

712

.02

11.6

711

.83

12.2

312

.12

12.0

312

.211

.46

12.1

Na 2

O

1.

932.

132.

212.

041.

842.

032.

152.

121.

992.

06

K2O

0.6

0.67

0.7

0.65

0.63

0.7

0.69

0.77

0.64

0.73

F

n.

dn.

d0.

010.

040.

03n.

d0.

03n.

d0.

11n.

d

Cl

0.

010.

01n.

dn.

dn.

d0.

020.

03n.

d0.

030.

01

H2O

(c)

2.04

2.03

2.02

2.01

2.04

2.06

2.03

2.05

1.99

2.05

O=

Fn.

dn.

dn.

d0.

020.

01n.

d0.

01n.

d0.

05n.

d

O=

Cln.

dn.

dn.

dn.

dn.

dn.

d0.

01n.

d0.

01n.

d

Tota

l10

0.35

99.9

899

.92

99.3

710

0.16

101.

2110

0.38

100.

3610

0.21

100.

79

Si

6.

759

6.74

76.

698

6.69

76.

802

6.65

66.

638

6.57

96.

624

6.62

9

Ti

0.

20.

183

0.21

70.

208

0.19

90.

223

0.22

80.

216

0.20

60.

204

Al/A

lIV1.

241

1.25

31.

302

1.30

31.

198

1.34

41.

362

1.42

11.

376

1.37

1

AlVI

0.43

30.

428

0.43

10.

429

0.46

20.

451

0.46

90.

498

0.35

20.

469

Fe3+

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

0.33

7n.

d

Fe2+

1.77

1.79

11.

791.

646

1.53

31.

623

1.55

41.

609

1.33

41.

602

Mn2+

0.02

30.

032

0.01

90.

028

0.01

50.

032

0.03

0.02

40.

035

0.02

5

Mg

2.54

62.

522

2.53

2.68

82.

732

2.65

82.

686

2.61

12.

735

2.69

8

Ca

1.

91.

904

1.84

91.

875

1.91

1.88

51.

883

1.91

61.

795

1.89

Na

0.55

10.

610.

632

0.58

50.

519

0.57

20.

608

0.60

20.

564

0.58

3

K

0.11

30.

126

0.13

20.

123

0.11

70.

130.

129

0.14

40.

119

0.13

6

F

n.

dn.

d0.

004

0.01

70.

016

n.d

0.01

5n.

d0.

053

n.d

Cl

0.

002

0.00

2n.

dn.

dn.

d0.

004

0.00

7n.

d0.

007

0.00

2

OH

1.99

81.

998

1.99

61.

983

1.98

41.

996

1.97

82

1.94

1.99

7

Sum

Cat

#17

.537

17.5

9617

.617

.583

17.4

8717

.574

17.5

8717

.619

17.4

7817

.606

X Mg

0.59

0.58

50.

586

0.62

0.64

0.62

10.

634

0.61

90.

672

0.62

7

Ö.F. ÇELİK

695

Tabl

e 5.

Amph

ibol

e an

alys

es f

rom

the

dol

erite

dyk

es c

ross

cutt

ing

the

met

amor

phic

sol

e ro

cks

of t

he M

ersi

n op

hiol

ite.

Sam

ple

M-7

7-1c

M-7

7-2c

M-7

7-3c

M-7

7-4c

M-7

7-4r

M-7

7-5c

M-7

7-6c

M-7

7-7c

M-7

7-8c

M-7

7-9c

M-7

7-10

cM

-77-

11c

M-7

7-12

cM

-77-

13c

M-7

7-14

c

SiO

255

.91

46.0

145

.07

44.7

447

.56

45.1

548

.53

44.6

447

.246

.64

47.9

447

.61

49.0

447

.21

45.8

7

TiO

20.

091.

051.

281.

40.

671.

350.

621.

420.

781.

330.

890.

590.

780.

951.

1

Al2O

31.

758.

328.

548.

896.

248.

246.

888.

767

7.89

6.82

7.21

6.45

7.6

8.17

Fe2O

3(c)

n.d

12.0

512

.23

12.2

27.

510

.51

10.9

210

.06

11.2

96.

578.

3311

.58

9.29

9.89

10.1

8

FeO

(c)

11

.52

11.9

512

.96

13.1

215

.17

14.2

710

.65

14.2

210

.27

12.9

211

.48

9.59

9.2

10.4

112

.53

MnO

0.22

0.38

0.46

0.39

0.58

0.37

0.43

0.33

0.24

0.36

0.34

0.33

0.37

0.35

0.43

MgO

16.5

8.7

7.79

7.36

9.01

7.5

10.4

27.

6110

.210

.33

10.8

310

.68

12.0

810

.95

8.64

CaO

13.0

610

.26

10.0

29.

7810

.62

1010

.52

10.3

510

.23

11.2

110

.89

10.3

610

.87

10.9

310

.17

Na 2

O

0.

21.

191.

41.

371.

271.

390.

91.

260.

981.

210.

991.

060.

821.

131.

23

K2O

0.03

0.06

0.06

0.07

0.42

0.07

0.04

0.06

0.04

0.07

0.05

0.07

0.06

0.04

0.05

F

n.

d0.

03n.

dn.

dn.

dn.

dn.

dn.

d0.

01n.

dn.

d0.

01n.

d0.

010.

01

Cl

n.

d0.

090.

10.

080.

040.

080.

060.

080.

030.

070.

070.

070.

030.

050.

1

H2O

(c)

2.13

2.02

2.01

22.

011.

992.

061.

992.

032.

022.

032.

042.

072.

051.

99

O=

Fn.

d0.

01n.

dn.

dn.

dn.

dn.

dn.

d0.

01n.

dn.

dn.

dn.

dn.

dn.

d

O=

Cln.

d0.

020.

020.

020.

010.

020.

010.

020.

010.

020.

010.

020.

010.

010.

02

Tota

l10

1.41

102.

0810

1.91

101.

410

1.08

100.

8910

2.02

100.

7810

0.29

100.

610

0.65

101.

1810

1.08

101.

5610

0.44

Si

7.

857

6.72

46.

647

6.63

7.05

26.

731

76.

661

6.93

16.

867.

007

6.91

77.

064

6.84

66.

799

Ti

0.

010.

115

0.14

20.

156

0.07

40.

151

0.06

70.

160.

086

0.14

70.

098

0.06

40.

085

0.10

40.

123

Al/A

lIV0.

143

1.27

61.

353

1.37

0.94

81.

269

11.

339

1.06

91.

140.

993

1.08

30.

936

1.15

41.

201

AlVI

0.14

70.

158

0.13

20.

183

0.14

20.

178

0.16

90.

202

0.14

30.

228

0.18

10.

151

0.16

0.14

60.

226

Fe3+

n.d

1.32

51.

357

1.36

30.

837

1.17

91.

185

1.13

1.24

70.

727

0.91

61.

266

1.00

71.

079

1.13

5

Fe2+

1.35

41.

461

1.59

91.

626

1.88

11.

779

1.28

51.

774

1.26

21.

591.

404

1.16

51.

108

1.26

21.

553

Mn2+

0.02

70.

047

0.05

80.

049

0.07

30.

046

0.05

30.

042

0.03

0.04

40.

042

0.04

10.

045

0.04

30.

054

Mg

3.45

61.

894

1.71

21.

625

1.99

21.

666

2.24

11.

693

2.23

22.

264

2.35

92.

314

2.59

52.

366

1.90

9

Ca

1.

966

1.60

71.

584

1.55

31.

687

1.59

71.

626

1.65

51.

611.

766

1.70

61.

613

1.67

81.

698

1.61

6

Na

0.05

40.

337

0.40

10.

394

0.36

60.

403

0.25

10.

366

0.28

0.34

60.

279

0.3

0.23

0.31

80.

355

K

0.00

50.

012

0.01

10.

013

0.07

90.

012

0.00

80.

012

0.00

70.

013

0.00

90.

012

0.01

20.

007

0.00

9

F

n.

d0.

012

n.d

n.d

n.d

n.d

n.d

n.d

0.00

6n.

dn.

d0.

005

n.d

0.00

30.

004

Cl

n.

d0.

023

0.02

60.

021

0.01

0.02

0.01

50.

020.

007

0.01

70.

016

0.01

70.

007

0.01

20.

026

OH

1.99

91.

965

1.97

41.

979

1.99

1.97

91.

984

1.98

1.98

71.

983

1.98

31.

979

1.99

31.

985

1.97

Sum

Cat

#17

.018

16.9

5616

.995

16.9

617

.132

17.0

1216

.885

17.0

3316

.897

17.1

2416

.994

16.9

2516

.92

17.0

2316

.979

X Mg

0.71

90.

565

0.51

70.

50.

514

0.48

40.

636

0.48

80.

639

0.58

80.

627

0.66

50.

701

0.65

20.

551

n.d

= n

ot d

etec

ted.

(c)

= c

alcu

late

d. c

= c

ore.

r =

rim

.


696

Table 6. Pyroxene analyses from the metamorphic sole rocks and crosscutting dolerite dykes of the Mersin ophiolite.

Sample M-77-3 M-77-4 M-178-1 M-178-2 M-178-3 M-178-4 M-178-5 M-178-6 M-178-7Rock Type dolerite dolerite amphibolite amphibolite amphibolite amphibolite amphibolite amphibolite amphibolite

SiO2 52.8 52.89 52.42 52.11 51.9 52.6 52.87 52.89 53.03

TiO2 0.37 0.31 0.24 0.29 0.24 0.27 0.25 0.24 0.27

Al2O3 2.17 2.1 2.16 2.16 2.01 2.34 2.13 2.2 2.21

Cr2O3 0.08 0.12 0.03 0.08 0.06 0.12 0.1 0.08 0.16

Fe2O3(c) 0.66 n.d 0.74 0.25 1.18 0.16 n.d n.d n.d

FeO(c) 6.96 7.51 7.75 8.05 7.19 8.17 8.2 8.18 8.23

MnO 0.19 0.23 0.3 0.26 0.29 0.29 0.31 0.31 0.27

MgO 16.64 16.67 13.16 12.85 12.97 12.87 13.06 12.97 12.78

CaO 20.1 19.69 22.2 22.3 22.44 22.42 22.47 22.41 22.5

Na2O 0.19 0.16 0.64 0.6 0.63 0.65 0.61 0.63 0.64

Total 100.16 99.67 99.64 98.96 98.9 99.9 100 99.9 100.1

Si 1.939 1.951 1.958 1.961 1.954 1.960 1.967 1.969 1.971

Ti 0.01 0.009 0.007 0.008 0.007 0.008 0.007 0.007 0.007

Al/AlIV 0.061 0.049 0.042 0.039 0.046 0.04 0.033 0.031 0.029

AlVI 0.033 0.042 0.053 0.057 0.043 0.063 0.061 0.066 0.068

Cr 0.002 0.003 0.001 0.002 0.002 0.004 0.003 0.002 0.005

Fe3+ 0.018 n.d 0.021 0.007 0.033 0.005 n.d n.d n.d

Fe2+ 0.214 0.232 0.242 0.253 0.226 0.255 0.255 0.255 0.256

Mn2+ 0.006 0.007 0.009 0.008 0.009 0.009 0.01 0.01 0.009

Mg 0.911 0.916 0.733 0.721 0.728 0.715 0.724 0.72 0.708

Ca 0.791 0.778 0.888 0.899 0.905 0.895 0.896 0.894 0.896

Na 0.014 0.011 0.046 0.044 0.046 0.047 0.044 0.045 0.046

Sum Cat# 4.000 3.999 4.000 4.000 4.000 4.000 4.000 3.998 3.994

Wo(Ca) 41.283 40.407 47.685 48.002 48.688 48.000 47.764 47.842 48.182

En(Mg) 47.559 47.572 39.325 38.471 39.144 38.342 38.627 38.532 38.059

Fs(Fe2+) 11.159 12.021 12.989 13.528 12.168 13.658 13.609 13.626 13.759

XMg 0.81 0.798 0.752 0.74 0.763 0.737 0.739 0.739 0.734

n.d = not detected. (c) = calculated.

an albite (An2–4) composition. However, plagioclase withandesine and labradorite compositions was commonlyobserved in amphibolites from the other metamorphic solerocks of the Tauride Belt Ophiolites (Çelik 2002; Çelik &Delaloye 2006). Epidote, abundant in the upper part ofthe metamorphic sole rocks, occurs as both a primary andsecondary mineral in the amphibolites and is especiallyabundant in veinlets.

The lower part of the metamorphic sole rocks iscomposed mainly of quartz-feldspar-mica schist,amphibole-quartz-feldspar-mica schist, quartz-mica schistand quartzite. The most common texture of the micaschists is granolepidoblastic. The mineral assemblages in

the metamorphic sole rocks and their dolerite dykes aregiven in Table 2.

Dolerite dykes cutting the metamorphic sole rocksconsist of amphibole, pyroxene, plagioclase, secondaryminerals (e.g., epidote, quartz, chlorite), and accessoryminerals (titanite and ilmenite). The dykes show subophiticand microgranular textures. Some of the dykes have beenextensively affected by hydrothermal alteration. Whilequartz is a minor constituent of the dolerite dykes,amphibole is abundant: ferro-hornblende, magnesio-hornblende and actinolite were all observed. Plagioclasesexhibit alteration minerals such as kaolinite and epidote butfresh plagioclases in the same rocks are also observed,

Ö.F. ÇELİK

697

Tabl

e 7.

Fe

ldsp

ar a

naly

ses

from

the

am

phib

olite

s of

the

met

amor

phic

sol

e ro

cks

of t

he M

ersi

n op

hiol

ite.

Sam

ple

M15

4-1

M15

4-2

M15

4-3

M15

4-4

M15

4-5

M15

4-6c

M15

4-6r

1M

154-

6r2

M15

4-7c

M15

4-8c

M15

4-9c

M15

4-10

cM

154-

11c

M15

4-12

c

SiO

266

,45

66,5

369

,668

,17

68,6

969

,21

69,3

567

,88

68,7

566

,29

67,9

66,7

868

,11

69,3

5

Al2O

319

,85

20,2

320

,04

19,7

20,1

419

,99

19,9

19,9

520

,06

20,4

420

,47

20,1

720

,19

20,2

4

Fe2O

3n.

d0,

05n.

d0,

080,

10,

04n.

d0,

020,

010,

050,

02n.

d0,

040,

02

MgO

0,01

0,01

n.d

n.d

n.d

n.d

n.d

n.d

0,01

n.d

n.d

0,01

n.d

0,05

CaO

0,69

0,82

0,75

0,74

0,75

0,63

0,67

0,74

0,77

0,92

1,01

0,84

0,78

0,98

BaO

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

0,03

Na 2

O

11

,35

11,3

711

,23

11,1

111

,37

11,4

411

,49

11,2

11,3

411

,27

11,0

711

,31

11,3

811

,09

K2O

0,1

0,1

0,11

0,1

0,12

0,07

0,09

0,1

0,1

0,09

0,09

0,09

0,1

0,1

Tota

l98

,45

99,1

110

1,73

99,9

101,

1810

1,38

101,

5199

,88

101,

0499

,05

100,

5699

,21

100,

610

1,87

Si

2,

992,

977

2,98

72,

982

2,97

2,98

32,

986

2,97

12,

975

2,96

92,

987

2,98

32,

996

2,97

5

Al/A

lIV1,

007

1,02

11,

014

1,01

61,

026

1,01

51,

011,

029

1,02

31,

032

1,01

61,

016

1,00

31,

023

AlVI

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

n.d

Fe3+

n.d

0,00

2n.

d0,

003

0,00

30,

001

n.d

0,00

1n.

d0,

002

0,00

1n.

d0,

001

0,00

1

Mg

0,00

10,

001

n.d

n.d

n.d

n.d

n.d

n.d

0,00

1n.

dn.

d0,

001

n.d

0,00

3

Ca

0,

032

0,03

80,

034

0,03

50,

035

0,02

90,

031

0,03

50,

036

0,04

20,

046

0,03

90,

035

0,04

5

Na

0,94

70,

944

0,93

50,

942

0,95

40,

956

0,95

90,

950,

951

0,93

60,

904

0,93

70,

929

0,92

3

K

0,00

50,

005

0,00

60,

005

0,00

70,

004

0,00

50,

005

0,00

60,

005

0,00

50,

005

0,00

50,

006

Sum

Cat

#4,

982

4,98

74,

976

4,98

34,

995

4,98

94,

991

4,99

24,

992

4,98

54,

959

4,98

4,97

4,97

7

Ab96

,235

95,6

3395

,85

95,9

295

,845

96,6

6896

,386

95,9

3795

,84

95,2

3394

,729

95,5

3395

,816

94,7

39

An3,

227

3,82

73,

518

3,52

33,

493

2,93

3,10

13,

524

3,57

94,

275

4,78

3,94

23,

614

4,63

4

Or

0,53

70,

539

0,63

20,

557

0,66

10,

401

0,51

30,

539

0,58

10,

492

0,49

0,52

50,

565

0,58

3

n.d

= n

ot d

etec

ted.

c =

cor

e. r

= r

im.


698

indicating recrystallization during the hydrothermalalteration phase. Some pyroxenes in the dolerite dykesoccur as relict grains surrounded by reaction rims of green-brown to green hornblende. Pyroxene is more abundantin dykes over 30 cm thick. Pyroxenes from the doleritedyke sample M-77 are augite in composition. Ilmenite isgenerally observed as dendritic crystals in pyroxene-richdolerite dykes. The dykes range from 10 cm to 5–6 mthick and some exhibit well-developed chilled margins.

Geochemistry

Cr values of the amphibolites in the Mersin ophiolite rangefrom 55 ppm to 1292 ppm. All the amphibolites are ofigneous origin, based on the Cr-TiO2 diagram of Leake(Leake 1964) (Figure 2a), and are probably derived frommafic rocks such as basalts and gabbros. The mica schistswere derived from sedimentary and volcano-sedimentaryrocks, as are other mica schists from the metamorphic solerocks of the Lycian and Pozantı-Karsantı ophiolites (Çelik2007). On a Na2O + 31/47K2O – Al2O3 diagram (Fonteilles1976), the mica schists plot in the fields of lithic sandstoneand greywacke protoliths (Figure 2b).

In the SSZ systems, three different end-membercomponents can be considered to melt to form MORB, OIBand IAT basalt compositions and variable mixing betweenthese three end-member components may form lavacompositions between MORB-OIB and MORB-IAT (Leat etal. 2000, 2004). On a TiO2-MnO-P2O5 diagram (Mullen1983), amphibolites plot in the ocean island alkali andtholeiite (OIA, OIT) and island arc tholeiite (IAT) basaltfields, whereas the dolerite dykes plot mostly in the IATfield (Figure 3a). The arc signature of the dyke samples isshown on a Ti-V diagram (Figure 3b), where theamphibolites are represented by OIB, excluding twoamphibolites and one dolerite sample that exhibit a MORBsignature. On a TiO2-Zr diagram, amphibolites from themetamorphic sole rocks of the Mersin and other TaurideBelt ophiolites exhibit SSZ geochemical charactersitics, withIAT, MORB, and OIB-like affinities and probable mixing ofthese end-members (Figure 4a). On the same diagram,

dolerite dykes from the Mersin ophiolite clearly exhibit anarc-related origin, as do other dolerite dykes from theother Tauride Belt ophiolites. According to the Cr-Ydiagram, all the dolerite dykes and one amphibolite sample(M-157) from the metamorphic sole rocks of the Mersinophiolite plot in the IAT field, indicating subductioninfluence during their generation (Figure 4b). The doleritedykes and the metamorphic sole rocks of the Tauride BeltOphiolites thus have very similar geochemicalcharacteristics to the volcanic rocks of the active back-arcspreading centre (East Scotia Ridge) located to the westof the South Sandwich island arc, based on the Cr-Y andTiO2-Zr diagrams. The REE patterns of the amphibolitesfrom the Mersin ophiolite exhibit two different groups(Figure 5a). The first is characterized by LREE enrichmenttypical of WPB (or seamount). In this group, the LaN/YbN

ratio of one amphibolite sample (M-78) is 2.05. Thissample should be interpreted as N-MORB or a transitionrock from N-MORB to enriched MORB (E-MORB). Thesecond group of amphibolites, including the dolerite dykes,exhibits a relatively flat pattern. Slight depletion in LREEcould be interpreted by derivation from a MORB source.However, LaN/YbN ratios (0.56–1.29) of the dolerite dykes(except M-86) and the amphibolites from the second groupare similar to the LaN/YbN ratios (0.63–1.45) of the doleritedykes from the Lycian ophiolites, which are located furtherwest than the Mersin ophiolite. Lead isotope compositionsof the dolerite dykes from the Lycian ophiolites indicate asubduction-related origin and exclude their derivation solelyfrom a MORB source (Çelik & Chiaradia 2008). Thecrystallization age of the dolerite dykes of the Mersin andthe Lycian ophiolites is also similar (Çelik et al. 2006). Allthese data indicate that the dolerite dykes of the Mersinophiolite were formed in a subduction-relatedenvironment. On the N-MORB normalized spider diagram,the first group of amphibolites exhibits multi-elementpatterns more enriched than N-MORB (Figure 5b) andsimilar to OIB basalts. The second group of amphibolitesdisplays slight enrichment in large ion lithophile elements(LILE; Rb, Th) compared to Nb and REE. Theircompositions, however, are similar to N-MORB or

Table 8. K-Ar ages and analytical data for the amphibolite and dolerite dykes from the Mersin ophiolite.

Sample Rock Mineral % K 40Ar* moles/g × 10-11 % 40Ar* 40Ar/36Ar × 102 40K/36Ar × 104 Age in Ma

M-175 amphibolite hornblende 0.50 8.294 96.0 73.26 125.75 93.8 ± 3M-82 dolerite dyke whole rock 0.97 14.537 91.2 33.58 60.99 84.4 ± 3M-87 dolerite dyke whole rock 1.30 20.514 89.6 28.49 48.30 88.8 ± 2

transitional between N-MORB and E-MORB. The doleritedykes exhibit LILE enrichment (K, Rb, Sr, Ba) relative tosome high-field-strength elements (HFSE) such as Nb, Zr,Ti (Figure 5c), suggesting that they were formed as IAT-like dolerites in a subduction related environment.However, LILE are strongly affected by alteration andmetamorphic processes, therefore characterization anddiscrimination of metamorphic and magmatic suites hasbeen done using trace elements generally consideredrelatively stable (immobile) during alteration, such as HFSEand REE (Beccaluva 1979; Pearce 1982; Thompson1991). All the dolerite dykes have small negative Eu

Ö.F. ÇELİK

699

Na

2O

+31/4

7K

2O

Al2O3 (wt %)

0 5 10 15 200

1

2

3

4

5

6

7arkoses

lithic sandstones

greywackes

shales

100% 70

% 50%

33%

25%

(b)

0 0.8 1.6 2.4 3.2 4

1

10

100

1000

10000

TiO2 (wt %)

igneous field

sedimentary field

Cr

(pp

m)

(a)

CAB

IATM

OR

B

OIT

OIA

MnO*10 P2O

5*10

TiO2

(a)

amphibolites from the metamorphic sole

rocks of the Mersin ophiolites

mafic dykes cutting the metamorphic sole


(b)

0 5 10 15 20 25

0

100

200

300

400

500

60010

50

100

Ti/1000

VMORB

OIB

20

IATFigure 2. (a) Cr versus TiO2 for the amphibolites. Outside the ringed

area represents igneous protoliths; (b) alkalis versus Al2O3

diagram showing the original sedimentary lithologies of themica schists from the metamorphic sole rocks of the Mersinophiolite.

Figure 3. (a) TiO2-MnO-P2O5 discrimination diagram (Mullen 1983) forthe amphibolites and the dolerite dykes in the metamorphicsole rocks of the Mersin ophiolite; (b) Ti versus V diagramshowing tectonomagmatic environment of dolerite andamphibolite rocks in the metamorphic sole rocks of the Mersinophiolite, after Shervais (1982).

anomalies (Eu/Eu* = 0.98–0.87) suggesting plagioclasefractionation in their origin. However, the amphibolitesexhibit both small negative (0.98–0.87) and positive(1.13–1.09) Eu anamolies. The latter values should beconsistent with plagioclase accumulation in their protoliths.

The Sm/Yb-Ce/Sm ratio was used to characterizemantle source regions for the amphibolites and mafic dykes(Figure 6a). The high Sm/Yb and Ce/Sm ratios of theamphibolites beneath the Mersin ophiolite and in the maficdykes (pyroxenite and dolerite) cutting the amphibolites ofthe other Tauride Belt ophiolites suggest that they werederived from melting of OIB-like enriched mantle source,whereas the dolerite dykes and some of the amphiboliteswith low Sm/Yb and Ce/Sm ratios plot in the field oftholeiitic amphibolites from the Tauride Belt ophiolites.

Nb depletion and Th enrichment in volcanic rocks istypical of a subduction influence (Saunders & Tarney 1979,1984; Pearce et al. 1984). Moreover, Th is a key elementin subduction zone discrimination and is enriched in all arclavas, and so is mobilized in subduction zones, but it isimmobile until the temperature approaches the meltingtemperature (Johnson & Plank 1999; Pearce 2003).Nb/Nd versus Th/Nb ratios were used to show the mantlesource regions and the subduction influence for theamphibolites and mafic dykes (Figure 6b). Th/Nb ratios ofthe most of the amphibolites and mafic dykes are higherthan the average N-MORB and OIB values, suggesting thatthe subduction influence was common during thegeneration of the mafic dykes and the protoliths of theamphibolites.


700

arcbasalts

MORB

OIB

TiO

2(w

t%

)

0.1

1

10

10 100 1000

Zr (ppm)

(a)

amphibolite from the

metamorphic sole rocks of

the Mersin ophiolites

mafic dyke cutting the meta-

morphic sole rocks of the

Mersin ophiolites

amphibolite beneath the Tauride

Belt Ophiolites

mafic dyke cutting the

metamorphic sole rocks

of the Tauride Belt Ophiolites

boninite

IAT

MORB

1

10

100

1000

10.000

1 10 100

Cr

(ppm

)

Y (ppm)

(b)

lavas and volcanic glasses

from active back-arc spreading

centre of the East Scotia Ridge

(the segments from North to

South)

Figure 4. (a) TiO2 versus Zr tectonomagmatic discrimination diagram for the metamorphic sole rocks and their crosscutting mafic dykes fromthe Tauride Belt ophiolites and the East Scotia Ridge rock samples (shaded) from the South Sandwich arc-basin system. Fields forMORB, IAT and OIB after Pearce (1980); (b) Cr-Y plot after Pearce et al. (1981), showing fields for boninite, IAT, and MORB. Datafor the East Scotia Ridge are from Fretzdorff et al. (2002) and Leat et al. (2004). Data for the amphibolites and mafic dykes fromthe Tauride Belt Ophiolites are from Lytwyn & Casey (1995), Polat & Casey (1996), Dilek et al. (1999), Çelik & Delaloye (2003,2006), Çelik (2007).

Thermobarometrical and GeochronologicalInvestigations

The amphibolites from the metamorphic sole rocks haverestricted mineral assemblages (e.g., hornblende andplagioclase) and provide only limited information abouttheir metamorphic conditions.

The Na content in the M4 site of amphibole may be auseful semi-quantitative geobarometer for amphibolitesformed in amphibolite and greenschist facies (Brown 1977;Laird et al. 1984). The pressure for the metamorphic solerocks, deduced from the proportions of NaM4-AlIV and AlVI-Si numbers of amphiboles, is less than 5 kb (Figure 7a, b).These pressure estimates are in agreement with thecompositions of all analysed amphiboles that plot in thelow-pressure (LP) to medium-pressure (MP) domain ofLaird et al. (1984) (Figure 7c). Similar pressure valueswere also obtained from the metamorphic sole rocks ofthe Beyşehir and Pozantı-Karsantı ophiolites (Çelik &Delaloye 2006; Çelik 2007). Temperature conditions atthe time of metamorphism for the metamorphic sole rockswere calculated using the hornblende-plagioclasethermometer of Holland & Blundy (1994). Sample M-154consists of hornblende, plagioclase, sphene and opaqueminerals. Since quartz is absent from the assemblage, theedenite-richterite thermometer was used on the formula.The calculated temperature is 522 ± 15 °C within a 1σconfidence interval.

K-Ar ages may be unreliable, due to mobility of Arand/or excess Ar, and should be treated with caution. Theeffects of excess Ar and of alteration can be minimizedusing the 40Ar/39Ar method. Therefore, K-Ar ages werecompared with more reliable 40Ar/39Ar ages in order toexplore their geochronological reliability. K-Ar agedetermination on hornblende from sample M-175(amphibolite) yielded 93.8 ± 3 Ma (2σ) (Table 8). Dilek etal. (1999) presented 40Ar-39Ar plateau ages of 91.3 ± 0.4and 93.8 ± 0.5 Ma for two amphibolites from Mersinophiolite, which they interpreted as cooling ages. Parlak etal. (1995) presented a K-Ar age of 93.4 ± 2 Ma foramphibolites from the Mersin ophiolite. Parlak & Delaloye(1999) calculated a weighted mean 40Ar-39Ar age ofamphibolites (hornblende) of 92.6 ± 0.2 Ma andinterpreted this as the age of the intra-oceanic thrusting,during which sub-ophiolitic metamorphic sole rocks weredeveloped. Thus the K-Ar age data (93.8 ± 3 Ma) in thisstudy agrees with previously obtained 40Ar-39Ar age data(Dilek et al. 1999; Parlak & Delaloye 1999). However,closure temperature of amphibole in the 40Ar-39Ar systemwas estimated to be approximately 500–550 °C formoderate cooling rates (Harrison 1981), and hence themetamorphic temperature in the sole rocks, calculated as522 ± 15 °C, corresponds to the closure temperature ofamphibole in 40Ar-39Ar system. Therefore ~ 91–93 Ma

Ö.F. ÇELİK

701

0.1

1

10

100

1000

Ro

ck

/N

-MO

RB

Rb Th Nb La Pr P Sm Hf Ti Dy Ho Tm Lu

Ba U K Ce Sr Nd Zr Eu Gd Y Er Yb

amphibolite

(b)

Rb Th Nb La Pr P Sm Hf Ti Dy Ho Tm Lu

Ba U K Ce Sr Nd Zr Eu Gd Y Er Yb0.1

1

10

100

1000

Ro

ck

/N

-MO

RB

dolerite

(c)

1

10

100

1000

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Sa

mp

le/

C1

Ch

on

drite

(a)field of amphibolites beneath the

Tauride Belt Ophiolites

field of mafic dikes in the

Tauride belt ophiolites

amphibolite beneaththe Mersin ophiolite

dolerite dyke cuttingthe Mersin ophiolite

Figure 5. (a) Chondrite-normalized REE plots for amphibolites and dykerocks from the metamorphic sole rocks of the Mersinophiolite. Normalizing values are from Sun & McDonough(1989). Data for the amphibolites and mafic dykes from theTauride Belt Ophiolites are from Dilek et al. (1999), Çelik &Delaloye (2003, 2006), Çelik (2007); (b, c) MORB–normalized trace element patterns of the amphibolites andcross-cutting dolerite dykes from the metamorphic sole rocksof the Mersin ophiolite.

could also be interpreted as the approximate metamorphicage of the amphibolites.

Dilek et al. (1999) obtained 40Ar/39Ar ages of 91.0 ±0.6 Ma from one dolerite dyke from the Mersin ophiolite.Parlak & Delaloye (1996) also dated dolerite dykes (aswhole rock analyses) from the Mersin Ophiolite using the40Ar/39Ar method. They obtained ages ranging from 63.8± 0.9 to 89.6 ± 0.7 Ma and interpreted these ages ascrystallization ages indicating the time of the dykeemplacement. Koepke et al. (2002) reported that both theage and remarkable similarity in composition and structureof the ophiolites of Karpathos and Rhodes (southernAegean islands) to ophiolite occurrences in southern Turkeydemonstrates that they also belong to the Cretaceousophiolite belt of the Taurides. They obtained K-Ar agesfrom dolerite dykes ranging from 74.5 ± 2.2 to 95.3 ±4.2 Ma, with a mean age around 87 Ma. In this study, K-Ar age determinations on the dolerite dykes cutting themetamorphic sole rocks yield ages between 88.8 ± 2 and84.4 ± 3 Ma (Table 8). As mentioned before, doleritedykes in the Mersin ophiolite do not cut the mélange andplatform carbonates. While some of the dykes have chilledmargins, others do not. All of these data from the dolerite

dykes suggest that dyke injections into the metamorphicsole rocks of the Mersin ophiolite were common atdifferent times after the generation of the metamorphicsole rocks, but predated the emplacement of the Mersinophiolite on to the Tauride platform carbonates.

Discussion and Conclusion

The Western Pacific is a natural laboratory for investigatingsubduction models and their link to ophiolites. CenozoicSSZ systems of the Western Pacific basins include matureand immature SSZ systems, such as Tonga-Kermadec,Mariana-Izu-Bonin and Lau. Backarc basin crust forms atspreading centres that in many backarc basins, erupttholeiitic melts with mineral and chemical signaturesranging from N-MORB to IAT (Hawkins & Melchior 1985;Gribble et al. 1988, 1996; Hawkins 1995a, b). Seamountsin the backarc basins range in composition from island arcchemistry to OIB (Hawkins 2003). The Lau and MarianaTrough backarc basins contain a wide range of rockcompositions with N-MORB, IAT, BABB and enrichedbasalts including OIB, as well as fractionated rocks of theseseries (Hawkins 2003). One source of SSZ magmas ismantle material convectively entrained above a subduction


702

0

1

2

3

4

5

6

7

0 2 4 6 8 10 12 14 16

Sm

/Yb

Ce/Sm

OIB

MORB

(a)

field of mafic dykes

cutting the Tauride

Belt Ophiolites

field of amphibolites

beneath the Tauride

Belt Ophiolites

average MORB

and OIB

MORB

OIB

Nb/N

d

Th/Nb

0.1

1

10

0.01 0.1 1 10

(b) amphibolites beneath

the Tauride Belt Ophiolites

mafic dykes cutting the

metamorphic sole rocks

of the Tauride Belt Ophiolites

average MORB

and OIB

amphibolites from the metamorphic sole


mafic dykes cutting the metamorphic sole


Figure 6. (a) Sm/Yb versus Ce/Sm diagram, after Pearce (1982), showing source characteristics for the dolerite dykes and the amphibolites.Fields of OIB and MORB are from Sun & McDonough (1989). Data for the metamorphic soles and mafic dykes from the TaurideBelt Ophiolites are from Lytwyn & Casey (1995), Parlak et al. (1995), Polat & Casey (1996), Dilek et al. (1999), Çelik & Delaloye(2003, 2006), Çelik (2007); Çelik & Chiaradia (2008), (b) Nb/Nd versus Th/Nb diagram showing source characteristics andsubduction influence for the amphibolites and the dolerite dykes of the metamorphic sole rocks from the Tauride Belt Ophiolites.Fields of OIB and MORB are from Sun & McDonough (1989). Data for the metamorphic sole rocks and dolerite dykes from theTauride Belt ophiolites are from Polat & Casey (1996), Dilek et al. (1999), Çelik & Delaloye (2003, 2006), Çelik (2007), Çelik& Chiaradia (2008).

zone by viscous drag exerted by the subducted plate, andbrought in under the backarc basin (Ewart & Hawkesworth1987). This ‘new’ mantle may be relatively fertile andcapable of generating N-MORB, E-MORB, or OIB (Hawkins1976, 1995a, b; Ikeda & Yuasa 1989; Hawkins et al.1990; Volpe et al. 1990).

As indicated in the geochemistry section, theamphibolites of the metamorphic sole rocks from TaurideBelt Ophiolites, including the Mersin ophiolite, are generallymetamorphosed equivalents of IAT-, MORB-, E-MORB- andOIB-type basaltic rocks. Petrographic and geochemical

results of ophiolite-related intrusives and extrusivessuggest that the Late Cretaceous ophiolites of the Tauridebelt were formed in a SSZ environment (Pearce et al.1984; Parlak et al. 1996, 2002; Çelik et al. 2006) (Figure8a, b). Protoliths of the IAT-, OIB- and MORB-likeamphibolites, as well as fractionated rocks of these seriesfrom the metamorphic sole rocks of the Tauride BeltOphiolites are probably generated in the SSZ environment,as can be observed in the Lau and Mariana Trough fromWestern Pacific or in the South Sandwich arc-basin systemof South Atlantic ocean.

Ö.F. ÇELİK

703

actinoliteedenite

pargasite

~ 5 kb

1.2

1.0

0.8

0.6

0.4

0.2

0

(b)

0 0.4 0.8 1.2 1.6

0.4

0

0.2

0.3

0.1

HPMP

LP

(c)

M-151M-178M-154

(a)

0 0.5 1 1.5 20

0.5

1

1.5

2

7kb

6kb

5kb

4kb3kb2kb

NaM

4

AlVI

AlIV

Na(a.p.f.u )

M4

Si5.5 Si7.5Si7Si6.5Si6

Al + Fe 2Ti + Cr (a.p.f.u.)VI +3

Figure 7. (a) Comparison of NaM4 and AlIV for amphibole from amphibolites of the metamorphic sole rocks, after Brown (1977); (b) AlVI

versus Si diagram (Raase 1974) for amphiboles in the amphibolites; (c) Amphiboles from the metamorphic sole rocks of theMersin ophiolite plotted in the pressure discrimination diagram of Laird et al. (1984).

Previous models for generation of the metamorphicsole rocks and their mafic dykes, as well as the TaurideBelt Ophiolites in the Neotethyan ocean envisaged only onesubducted oceanic lithosphere (Lytwyn & Casey 1995;Polat et al. 1996; Parlak & Delaloye 1996, 1999; Önen &Hall 2000). Most of these studies did not explain the IAT-like amphibolites in the metamorphic sole rocks, andinstead generally mentioned amphibolites with OIB andMORB geochemical signatures. IAT-like amphibolites in themetamorphic sole rocks were recently reported by Çelik(2007), Çelik & Delaloye (2003, 2006), and Parlak et al.(2006), who identified IAT-like amphibolites in themetamorphic sole rocks of the Divriği ophiolite. Theysuggested that during intraoceanic subduction (Figure 8a,i), protoliths of the IAT-like amphibolites detached fromthe front of the overriding SSZ-type crust and protoliths ofthe OIB-like amphibolites from the top of the subducting

plate were initially subducted and metamorphosed up toamphibolite facies (Figure 8a, ii). In their tectonic model,it seems difficult to subduct the protoliths of IAT-likeamphibolites into the subduction zone if they remain partof the younger and buoyant oceanic lithosphere. Asmentioned earlier, the age of the metamorphic sole rocksis around 92 Ma and the oldest age data obtained from thedolerite dykes for the Mersin ophiolite yields 91.0 ± 0.6Ma, so the formation ages of the two different rock typesare very close (~ 1 or 2 Ma) to one another. Although themetamorphic sole rocks show highly ductile deformation(e.g. folding structures), the cross-cutting dolerite dykes donot (Figure 8b, iii). This means that, when themetamorphic sole rocks were intruded by the doleritedykes, they were no longer in a metamorphic environment.The dolerite dykes cross-cutting the metamorphic solerocks in all the Tauride Belt ophiolites show neither ductile


704

(I) Early-Late

Cretaceous

N S

(SSZ type crust)Taurides

Neotethys(seamount)

(III)Late Cretaceous

mélange

dolerite dyke

injections (IAT)?

(II) Late Cretaceous

(SSZ type crust)IAT

roll-back

metamorphicsole rocks

(a)

(II)

Late Cretaceous

low angle subduction in SSZ

type crust or thrusting of young

oceanic lithosphere to generate

the metamorphic sole rocks

(I) Early-Late

Cretaceous

N S

(SSZ type crust)Taurides

Neotethys(MORBtype crust)

dolerite dyke injections

(IAT) following the metamorphism

(III)

Late Cretaceous

mélange

dolerite dyke

injections (IAT)

amphibolites

(IAT, MORB,

E-MORB

and OIB)dolerite

dyke (IAT)

?

(b)

(seamount)

Figure 8. (a) Tectonic model for the generation of the metamorphic sole rocks and their cross-cutting mafic dykes from the Tauride Belt ophiolites(modified after Parlak et al. 2006); (b) alternative tectonic diagram illustrating a double subduction model for the generation of themetamorphic sole rocks and cross-cutting mafic dykes from the Tauride Belt ophiolites.

deformation nor metamorphism. The metamorphicpressure estimation (~5 kb) suggests depths of around 17km. Accordingly, the metamorphic sole rocks weretectonically exhumed from ~17 km towards the oceanicfloor before extensive dyke injections in the Neotethyanocean. In the commonly accepted tectonic model, IAT-likedyke injections into the metamorphic sole rocks (not shownin the model of Parlak et al. 2006) should be generated viaroll-back and retreat of the subducted lithosphere (Figure8a, iii). However, it is unclear whether the time periodbetween the two events (1–2 Ma) is sufficient for theexhumation of the metamorphic sole rocks and for the roll-back and retreat of the subducted lithosphere allowingdolerite dyke injection into the metamorphic sole rocks.

OIB-, IAT- and MORB-like geochemistry from themetamorphic sole rocks were exclusively observed togetherin the same section and at the base of the Lycian ophiolitesin the Köyceğiz area (Çelik & Delaloye 2003; Çelik et al.2006). This is very important field evidence from themetamorphic sole rocks that proves that their protolithswere accreted and metamorphosed together beneath thesame oceanic lithosphere. The age data from themetamorphic sole rocks also supports their metamorphismat the same time. The cooling and/or generation ages of themetamorphic sole rocks exhibiting IAT-, MORB- and OIB-like geochemistry are similar (Çelik 2002) and range from91 to 93 Ma (Parlak et al. 1995; Dilek et al. 1999; Parlak& Delaloye 1999; Çelik et al. 2006). These age data alsosuggest that the SSZ-type ophiolite generation in theNeotethyan ocean is older (> 93 Ma) than that of themetamorphic sole rocks, since there are 93 Ma IAT-likeamphibolites in the Lycian ophiolites. As the weakest partof the SSZ, the axial ridge of the backarc basin would beemplaced as young, hot, ocean crust on a low-angle thrustover colder ocean crust and set up conditions for invertedmetamorphic gradients on the sole of the thrust zone(Hawkins 2003). Geothermobarometric studies for themetamorphic sole rocks from the Mersin ophiolite suggest

that the metamorphic temperature during themetamorphism was 522 ± 15 °C and the pressure wasless than 5 kb. Mineral paragenesis and mineral chemistryboth show that the metamorphic sole rocks from theTauride Belt ophiolites were metamorphosed in theamphibolite facies (Parlak et al. 1995, 2006; Çelik &Delaloye 2006; Çelik 2002, 2007). Moreover, absence ofeclogite or any high-grade metamorphic rocks in themetamorphic sole rocks of the Tauride Belt ophiolitessuggest a low-angle of subduction or thrusting in the SSZenvironment. Hence, protoliths of the IAT-likeamphibolites, together with OIB- and MORB-likeamphibolites would all be metamorphosed in the SSZenvironment following low-angle subduction or thrustingof the hot oceanic lithosphere on to the relatively coolupper part of the underlying oceanic lithosphere (Figure8b, ii). As mentioned above, the unmetamorphosed doleritedykes cutting the metamorphic sole rocks of the Mersinophiolite were emplaced after the generation of themetamorphic sole rocks. As the metamorphic sole rocksformed in subducted oceanic lithosphere, probablybelonging to the SSZ, the dolerite dykes with IAT chemistryshould be derived from the older subducted slab which alsogenerated SSZ-type ophiolites (Figure 8b, ii, iii). Therefore,the dolerite dykes exhibiting IAT chemistry provide furtherevidence for double subduction in the Neotethyan ocean.

Acknowledgments

The author thanks Michel Delaloye and Luis Fontbote formaking available laboratory facilities at the University ofGeneva, Switzerland. The author thanks Fabio Capponi forperforming major and trace element analyses. OsmanParlak is thanked for fruitful discussions in the field.Guidance by Georges Moritz during the microprobeanalyses at the University of Lausanne is greatlyappreciated. John A. Winchester edited the English of thefinal text.

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Received 17 September 2007; revised typescript received 22 February 2008; accepted 31 March 2008

detailed geochemistry and k-ar geochronology of the...

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