Metamorphic sole formation, emplacement and blueschist overprint:

(1)

Metamorphic sole formation, emplacement and blueschist overprint:

early obduction dynamics witnessed by W. Turkey ophiolites

A. Plunder ^1,* , P. Agard ^1,2 , C. Chopin ³ , M. Soret ¹ , A.I. Okay ⁴ and H. Whitechurch 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) Eurasia Institute of Earth Sciences and Department of Geology, Istanbul Technical University, (5) IPGS, Université de Strasbourg – UMR CNRS 7516

İTÜ Avrasya Yer Bilimleri Enstitüsü

ITU Eurasia Institute of Earth Sciences

1. Introduction & geological setting

study area

— 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 de- scribed) diversity of variably metamorphosed oceanic units (often called oceanic mélanges) also found below the ophiolites, which are rep- resenting an accretionary complex formed during the subduction?

During Cretaceous times, the convergence between the Anatolide Tauride block (fol- lowing the movement of Africa) and Eurasia lead to the closure of a branch of the Neo- tethyan 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 recon- structions. 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 ophi- olites in one group and the southern in ano- ther

OC1 Ophiolite

NE SE

Igdir

2. Data #1: ﬁeld observations

Dutluca peridotite / OC1 contact

perid OC2

zoom under

W E

Major differrence: presence of a blueschist overprint on ly to the north

Elmaağacı / sole

Iğdır / sole

sole

OC#1

N S

OC1 Ophiolite

OC2 Schematic situation

sole

chert

basalt tuff

OC1

OC2 OC3

Approximate modal amout of rocks in OC2 and OC1 along the NS transect of Western Anatolia

Pillow basalt near Iğdır

Radiolarian cherts near Aslapana Pillow breccia

Kınık

3. Data #2: petrology

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

Fe Mg

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

Methodology Pressure-Temperature pseudosection (i.e. phase diagram for ﬁxed bulk composition) were calculated using the software package Theriak/Dom- ino (de Capitani & Petrakakis, 2010). Two database were used: the da- tabase of Holland & Powell (1998) for maﬁc rocks with update for am- phibole 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 pre- sented 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 stability 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 EPSL 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

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

5. Conclusions

Blueschist-facies overprint?

0.3

0.25 0.2

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) ⁵⁵⁰ ⁶⁵⁰ ⁷⁵⁰ T (°C) 850

5 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

X_Prp

Ca_Cpx MnNaCaFMASH

+ H₂O 0.20

0.25 0.30

0.93

0.87

0.89

0.91

X_Prp

Na_Cpx 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.)

Çivili Kütahya Yeşilova

Bey Dağları

(De) T,K

E (Mu) (As) O,Ç

N S

50km

(Da) B Y (Du)

S I

+ -

-

+

Blueschist overprint in metam. sole Deformation at peridotite / OC1 interface

LN

T,K (De)

? ?

(a)

KU1308a 11TAV13a,b

KU1301 TAV110b

11TAV14b samples in Plunder et al., 2015

(c) E DU1108b

OR1028a

(Mu,As)

KU1314b

I,S

B

^YE1302b

YE1303

? (Du) O,Ç

(b)

KO1205

11OR33

KO1213 not to scale

~ 5 km

Afyon zone Tavşanlı zone OC3

OC2 OC1/1*

ophiolite metam. sole

Orhaneli granodiorite

no overprint minor overprint strong overprint

OC sample

formation of metam. sole

30 young - old

+

- metamorphic grade in the sole

850°C 750°C

hot mantle wedge

30 this study

400°C cooling of thermal regime

+

- ^cold

hot

30 400°C

... and slicing of OC2 cooling of thermal regime...

+

- ^cold

hot

30 Early stages: formation of the metamorphic sole

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 Travelling expenses were supported by the ERC Starting Grant 306810 SINK awarded to D.J.J. van Hinsbergen.

Bey Dağları Marmara sea

Aegean sea

Eskişehir Tavşanlı

Orhaneli Bursa

Muğla

Datça

Koyceğiz

Burdur

Antalya Afyon

Izm ir-A nka ra suture

Bornova flysch zone

İzmir

Denizli

Lycian nappes Menderes massif

Antalya nappes

27° 28° 29° 30° 31°

39°

38°

37°

40°

(Da) Y

B

S I

(Mu)

(As)

Ç O

(Du) E (De)

T K

Ophiolite Oceanic complex Tavşanlı zone (cont.) Afyon zone (cont.) Cycladic blueschsit Menderes massif Sample location:

- metamorphic sole - oceanic complexes Major tectonic contact

Age of metamorphic sole Tavşanlı area

86 90 94

age (Ma)

# ages

98 102

3

92 ± 4.4

age (Ma)

# ages

86 90 94 98 102

2 4 6

Age of metamorphic sole Lycian ophiolite 93 ± 1.8

30 km