Workshop on Tectonic and geodynamic evolution of Eastern Iran (3-6 nov. 2015 - Birjand, Iran)
Tectono-metamorphic processes beneath an obducted ophiolite:
evidence from metamorphic soles and accreted units from western Turkey
A. Plunder 1,* , P. Agard 1,2 , C. Chopin 3 , H. Whitechurch 4 and A.I. Okay 5
Institut des Sciences de la Terre de Paris
É C O L E N O R M A L E S U P É R I E U R E
(*) Presenting author - (1) ISTeP UPMC – UMR CNRS 7193, Paris, France (now @ Earth Sciences dept, Utrecht Univ. . The Netherlands - a.v.plunder@uu.nl), (2) IUF, Paris, France, (3) Laboratoire de géologie, École Normale Supérieure – UMR CNRS 8538, (4) IPGS, Université de Strasbourg – UMR CNRS 7516, (5) Eurasia Institute of Earth Sciences and Department of Geology, Istanbul Technical University
28 37
38 39
29 30
Marmara sea
N
Tavşanlı
Murat dağ
Kütahya Bursa
Burdur Orhaneli
Marmaris Aegean sea
YE1302 YE1313
YE1314
YE1306 YE1309 YE1310 YE1311 YE1312 LN1306
LN1307 LN1308 LN1309
LN1310
KU1312 KU1313 KU1314
DR1209 KU1301
KU1302 KU1303 KU1304 TAV1101
KU1315 KO1213
KO1203 KO1205
DE1201 DE1202
OR1307 TU1021
Marmara sea
N
Tavşanlı
Kütahya Bursa
Burdur Orhaneli
Marmaris
Aegean sea
Ophiolite Oceanic complex Tavsanli
Afyon
KU1307 KU1308 KU1309
YE1302 YE1313
YE1314
YE1306 YE1309 YE1310 YE1311 YE1312 LN1306
LN1307 LN1308 LN1309
LN1310
Marmara sea
N
Eskişehir Tavşanlı
Kütahya Bursa
Burdur Orhaneli
Marmaris Aegean sea
KU1307 KU1308 KU1309
LN1304 LN1305
YE1305
YE1307 YE1308
Menderes massif (not mapped)
L yc ia n na
p pe s
Lycian ophiolites
Tavşanlı ophiolites
metam. sole samples OC samples
metamorphic sole sample used fot PT calculations
1. Introduction & geological setting
study area
86 90 94 98 102
2 4 6
Age of metamorphic sole Lycian ophiolite
age (Ma)
# ages
93 ± 1.8
Age of metamorphic sole Tavşanlı area
86 90 94
age (Ma)
# ages
98 102
3
92 ± 4.4
— how can metamorphic soles be preserved along a 200 kilometre-long transect parallel to ophiolite transport in regard to the short-lived event they supposedly represent (cf Oman)?
— how can the blueschist overprint observed in several metamorphic sole locations (unlike for Oman) be found in the same structural position and supposedly of the same age?
— how can one account for the (so far poorly described) diversity of variably metamorphosed oceanic units (often called oceanic mélanges) also found below the ophiolites, which are representing an ac- cretionary complex formed during the subduction?
Methodology Pressure-Temperature pseudosection (i.e. phase diagram for fixed bulk composition) were calculated using the software package Theriak/Domino (de Capitani & Petrakakis, 2010). Two database were used: the database of Holland & Powell (1998) for mafic rocks with update for amphibole and clinopyroxene (Diener et al., 2007;
Green et al., 2007). The database by Berman (1988) was used for carpholite-bearing rocks (see discussion in Pourteau et al., 2014). Part of the calculation were presented in plunder et al. (2015).
High pressure overprint in metamorphic sole is estimated on the basis of the paragenesis and on reaction observed in the samples (ab = jd + qtz). The activity of jadeite in clinopyroxene is extrapolated from Liu &
Bohlen (1994) and need to be taken with care. Lawsonite stability curve after Evans (1990). Carpholite stabili- ty after Vidal et al. (1992).
References
Agard, P., Yamato, P., Soret, M., Prigent, C., Guillot, S., Plunder, A., Dubacq, B., Chauvet, A., & Monié, P. Subduction infancy: mantle resistance to slab penetration and metamorphic sole formation controlled by plate interface rheological switches. subm to EPSLv Berman, 1988. Internally-Consistent Thermodynamic Data for Minerals in the System Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-SiO2-TiO2-H2O-CO2. Journal of Petrology, 29:445-522
Diener, J.F.A., White, R., Powell, R. & Holland, T..J.B. 2007. A new thermodynamic model for clino- and orthoamphiboles in the system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O-O. Journal of metamorphic geology, 25:631-656.
de Capitani, C. & Brown, T., 1987. The computation of chemical equilibrium in complex systems containing non-ideal solutions. Geochimica et Cosmochimica Acta, 51:2639–2652 Evans, B. 1990. Phase relations of epidote-blueschists. Lithos, 25:3-23.
Green, E., Holland, T.J.B. & Powell, R. 2007. An order-disorder model for omphacitic pyroxenes in the system jadeite-diopside-hedenbergite-acmite, with applications to eclogitic rocks. American Mineralogist 92:1181-1189 Holland, T. J. B. & Powell, R. 1998. An internally consistent thermodynamic data set for phases of petrological interest. Journal of metamorphic Geology, 16:309–343.
Liu, J. & Bohlen, S. 1995. Mixing properties and stability of jadeite-acmite pyroxene in the presence of albite and quartz. Contributions to Mineralogy and Petrology, 119:433-440
Plunder., A., Agard, P., Chopin, C., Pourteau, A., and Okay A. I., Accretion, underplating and exhumation along a subduction interface: from subduction initiation to continental subduction (Tavşanlı zone, W. Turkey). Lithos, 226:233-254
Pourteau A., Bousquet, R., Vidal, O., Plunder, A., Duesterhoeft, E., Candan, O., Oberhänsli, R., 2014. Multistage growth of Fe–Mg–carpholite and Fe–Mg–chloritoid, from field evidence to thermodynamic modelling. Contribution to Mineralogy and Petrology 168:1–25 Şengör, A. M. C., &Yılmaz, Y. 1981. Tethyan evolution of Turkey: a plate tectonic approach. Tectonophysics, 75:181–241.
Vidal, O., Goffé, B. & Theye, C. 1992. Experimental study of the stability of sudoite and magnesiocarpholite and calculation of a new petrogenetic grid for the system FeO-MgO-Al2O3-SiO2-H2O. Journal of metamorphic geology, 10:603-614
SUMMARY
İTÜ Avrasya Yer Bilimleri Enstitüsü
ITU Eurasia Institute of Earth Sciences
Izmir
During Cretaceous times, the convergence between the Anatolide Tauride block (following the movement of Africa) and Eurasia lead to the closure of a branch of the Neotethyan ocean and to ophiolite obduction.
Since the classical paper of Şengör and Yılmaz, (1981) it is widely assumed that all western Anatolian ophiolites are derived from the same Tethyan realm (northern branch of Neotethys), leading to a variety of similarly looking palaeogeographic reconstruc- tions. Their common origin, however, is not well established: the absence of crustal sequences in both regions hinders correla- tions, the geographic distribution only allows the association of the northern ophiolites in one group and the southern in ano- ther
N S
OC1 Ophiolite
OC2
(Devlez) Tavşanlı ,Kütahya
OC1 Ophiolite
NE SE
Igdir Belkaya
Salda Iğdir
(Datça) Yayla
(Dutluca) Orhaneli,Çivili
Elmaağacı (Murat dağ)
2. Data #1: field observations
Dutluca peridotite / OC1 contact
perid OC2
zoom under
W E
(Da) NE S (Mu) T,K E (De) O,Ç N
SW
50km
Y B S I (Du)
Lycian thrust sheets
Menderes cover + basement Afyon zone Tavşanlı zone
Major differrence: presence of a blueschist overprint on ly to the north
W E
Schematic situation
Oceanic eclogite worldwide distribution modified after Agard et al., 2009
T An PlP
Pl
U B
A
E
30-40 km
~80 km
relative volume exhumed Lws +
QtzCs
Jd/Qtz + P(kbar)
T(°C) 20
10 15
5
600 800
400 200
25 30
Car Cld
Tavşanlı (this study)
Corsica New Caledonia Oman Western Alps Franciscan complex
?
Δρ<0
W. Turkey
Elmaağacı / sole
Iğdır / sole
Iğdır / sole
sole
OC#1
carpholite-bearing layer mafic blueschist
collected sample
Çayıroluk / OC2
OC#2 sole
chert
basalt tuff
OC1
OC2 OC3
Approximate modal amout of rocks in OC2 and OC1 along the NS transect of Western Anatolia
slicing of OC2
(i) dragging the metam. sole at depth (i’) dragging the metam. sole at depth
+ cooling via HP rocks (ii) partial BS overprint (ii’) partial BS overprint
tectonic slicing + dragging @ depth young - old
decreasi ng m etam .
CONTINENT OCEAN
HT / 800°-10kbar sole
30 km 15 0
Initiation of subduction:
intra-oceanic setting
1 2
Formation of metamorphic sole:
cold crust welded to hot mantle
H
2O
TAV AF
?
possible setting @ ca. 52 Ma
mantle delamination magmatism intrusion in
Tavsanli rocks
600 700 800 900
7 8 9 10 11 12
fsp grt cpx amph
fsp cpx amph
fsp grt opx cpx amph
fsp opx cpx amph fsp grt atz
cpx amph
0.1
0.08
Na Cpx 0.12 0.14
XPrp
0.08
0.10 0.12 0.14
0.16 0.18
0.20 0.22 0.24
0.06
4. PT estimates
Incipient subduction: the metamorphic sole
Mature subduction: high pressure slices 3. Data #2: petrology
5. Mechanism in the subduction zone
Early stages: formation of the metamorphic sole
How to explain the blueschist-facies overprint?
Into the subduction zone
Ep P hg P
g
Trem Gln Q tz Ep Grt Omp Lws Phg Gln Qtz
Ep Grt Omp Lws Phg Pg Gln Qtz Grt Omp
Phg Gln Lws Qtz Grt Omp Phg Gln Lws
Grt Omp Phg Gln Lws Chl Qtz
Omp Phg Gln Lws Chl Qtz
Omp Phg Gln Lws Ep Chl Qtz Phg Gln Lws Ep Chl Qtz Omp Phg Gln Lws Chl
Omp Grt Phg Gln
Lws Chl Grt 2 Omp
Phg Gln Lws Qtz
Ep Chl Phg Gln Qtz
Ep Grt Chl Phg Gln Qtz
Ep Grt Chl Phg Gln Pg Qtz
Ep Chl Phg Gln Pg Qtz
Ep Grt Phg Pg Trem Qtz Ep Grt Phg Gln Qtz Ep Lws Grt Phg Gln Qtz
Ep Grt Phg Pg Trem Gln Qtz Ep Grt Omp Phg Pg Gln Qtz Ep Grt Phg Pg Gln Qtz
Ep Omp Phg Pg Trem Qtz
Plg Ep Omp Phg Trem Qtz 3.5 3.4
3.6 3.7
0.70 0.68 0.74 0.72
10–20% Omp
NaCaKFMASHO + H2O
HP98+
Si Phg XFe3+ Omp 10–20% Omp
10 12.5 15 17.5 20 22.5 25
P(kbar)
300 400 500 T (°C) 600
OC3
0.3
0.25 0.2
0.15
0.15
Plg Ilm Grt Amp H2O Plg Ilm Grt
Ep Amp H2O
Plg Ilm Grt Cpx Ep Amp H2O
Plg Ilm Grt Ep Amp
Plg Ilm Grt Amp
Plg Ilm Grt Amp Cpx H2O
600 700 800 900
7 8 10 9 11 12 13
NaCaTFMASHO + H2O
P(kbar) P(kbar) P(kbar)
XGrs
T (°C) T (°C) 5 550 650 750 T (°C) 850
7 9 11 13 15
T h e
r i a k - D o m i n o
Cpx Grt Amph Plg
Opx Cpx Grt Amph Plg Grt Amph Plg
Grt Amph Qtz Plg
Grt Amph Qtz Plg Cpx Grt Amph Qtz Cpx
Grt Amph Ep Qtz
XPrp
CaCpx MnNaCaFMASH
+ H2O 0.20
0.25 0.30
0.93
0.87
0.89
0.91
XPrp
NaCpx NaCaFMASH
+ H2O
Metamorphic sole of western Anatolia show very similar peak PT conditions (i.e. 9-11 kbar and 750-800°C). Those results are similar to what is proposed for the other sole of worldwide ophiolite (Agard et al., subm.) and for Oman (Soret, comm. pers.)
0.48
3.3 3.25 3.5 3.45
0.49
0.5 0.51 3.35 0.52 3.4
Cld Phg Chl St
Phg Chl Ky
Bt +
Car Chl Phg
Car Cld Chl Phg
Cld Chl Phg Cld Chl Grt Phg
Phg Prl Chl Phg Prl Cld Chl
Phg Ky Cld Chl
Phg Chl
Phg Chl St PhgChl
St Ky
Phg Chl St Grt
Phg St And
Grt + Ky +
not reccorded on Earth
P(kbar)
13 18
3 20
5.5 8 10.5 15.5
XMg Car Si Phg
KFMASH + qtz + H2O
Berman 88+
OC2
200 300 400 500 600
Lws +
QtzCs
ajd=1
ajd=0.5
P(kbar)
T(°C) 20
10 15
5
600 800
400 200
25 30
Car Cld Δρ<0
OC 1 - 1.5 BS sole OC 2
OC 3
HT sole
Çivili Kütahya Yeşilova
?
~30°C/k m
~7°C/k m
HT green core
HP blue rim HT green core
HP blue rim
KU1301 200 µm
[for OC #3 see Plunder et al., 2015]
500 µm
DU1206
Rt Chl Ttn
Gln rim Hbl core
Grt Phg
Fe-Mg carpholite was also observed in OC
#2 coexisting with quartz, phengite and chlorite
KO1213 (OC2) 500 µm
Car
Qtz Phg
Amphiboles - OC2
Fe-Gln Gln
Rbk other samples
MRbk
YE1303 TAV1101b
LN1305
KU1301 OC #2 KU1314b
OC #1.5?
OC #1 Al
Fe Mg
Fe
Pumpellyite
Pu-(Al) Al
Pu-(Fe) Pu-(Mg)
Mg 50
Samples from OC #2 show the developpemnet of pumpellyite associated with sodic amphibole, lawsonite and sodic pyroxene (OC #2).
Some samples apparently related to OC #1 show the developpement of lawsonite related to pumpellyite. They can be assigned to OC #1.5
Samples from OC #1 consist manly of incipient metamorphosed rocks. The magmatic texture might still be observed. Some- times magmatic mineral are preserved. OC #1 rocks are strongly hydrothermalized. They show typical albite-epidote-chlorite paragenesis. In some samples volcanic glass can be observed. Some other samples show the developpement of pumpellyite.
10 µm ab
pmp
lws
LN1305
LN1305 relictual mag cpx
200 µm
KO1205 (OC1)
500 µm matrix Chl
30 µm ttn
chl pmp
ab
KU1314b(OC1) 30 µm
KU1314b(OC1) Ab pmp
ttn
chl
pmp
gln ab
Metabasite... ...and Fe-Mg carpholite bearing samples
OC #1.5?
Aug
Grt
Hbl
Cpx
250 µm YE1302
OC #1
sole OC #2
OC #2
Infra ophiolitic mélange Oceanic complex 1 Oceanic complex 2 Oceanic complex 3
Blueschist overprint of metam. sole strong overprint
overprint incipient overprint no overprint
Fe Mg
Mn
Mn
carpholite
phengite
11OR16 KO1213 DU1215
DU1216p DU1216l DE1201 DE1201c Samples (OC2)
XMg 0.4 0.5 0.6 0.7 0.8 0.9 3.1
3.2 3.3 3.4 3.5 3.6 3.7 Si(p.f.u)
Retrograde Phg Peak Phg
