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)
amphibolite(hb+pl+spn)
quartzite(qtz+pl+ep+chl+bt+mu+opq)
amphibolite(hb+pl+spn)
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
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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.
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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
.
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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
.
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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.
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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
rocks of the Mersin ophiolites
(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.
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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
rocks of the Mersin ophiolites
mafic dykes cutting the metamorphic sole
rocks of the Mersin ophiolites
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
GEOCHEMISTRY AND GEOCHRONOLOGY OF MERSİN OPHIOLITE, S TURKEY
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