The origin and P-T conditions of the metamorphic sole rocks beneath the Late Cretaceous Pınarbaşı Ophiolite, Eastern-Central Anatolia

ABSTRACT

Metamorphic sole rocks of the Pınarbaşı Ophiolite are one of the best-preserved rock units observed along the Tauride Ophiolite Belt in Turkey. The metamorphic sole rocks observed as tectonic slices at the base of mantle tectonites as well as blocks in the mélange units consist mainly of garnet-clinopyroxene-amphibolite, garnet-amphibolite, amphibolite, epidote-amphibolite, quartz-amphiboleschist and metabasalt. The amphibolites display a wide range of geochemical signatures such as those of N-MORB, E-MORB, OIB and IAT. The metabasalts exhibit OIB geochemical characteristics. P-T estimates indicate that the garnet-clinopyroxene-amphibolites reached peak metamorphic conditions of 790-840 °C and 12-14 kbar. High-grade metamorphism is followed by a stage of decompression, which is indicated by the presence of symplectitic growth of amphibole and plagioclase over garnet in garnet-clinopyroxene-amphibolites. P-T estimates for garnet-clinopyroxene-amphibolites suggest that they were metamorphosed under granulite-facies conditions (ca. 35-40 km). High temperature estimated from granulite facies rocks should be ascribed to the occurrence of the sole rocks during the inception of the intra-oceanic subduction, beneath young or relatively hot oceanic lithosphere. On the other hand, mineral paragenesis of the metabasalts suggest greenschist facies metamorphic conditions. Protoliths of the metabasalts were probably metamorphosed during final stages of subduction where they were very close to sea floor as the subduction zone was probably clogged by a seamount. The greenschist- and granulite-facies sole rocks were metamorphosed probably beneath the hot oceanic lithosphere at different depths of the subduction zone. Considering all these data are important to better understanding intra-oceanic subduction and final obduction events of the Tethys Ocean.

Graphical abstract

KEYWORDS:

• Ophiolite
• metamorphic sole rocks
• P-T conditions
• pseudosection modelling
• subduction zone

Highlights

- The amphibolites have a wide range geochemical signatures such as (E-MORB, N-MORB, OIB, and SSZ).

- The protolith of the metabasalts is related to seamounts.

- Granulite facies metamorphic sole rocks were metamorphosed (790–840°C 12–14 kbar) at about 35–40 km depth in the subduction zone.

- The mineral paragenesis of the metabasalts suggests that they were metamorphosed in green-schist facies conditions.

- The granulite- and green-schist facies metamorphic sole rocks were metamorphosed separately in the subduction zone.

Acknowledgments

This research presented in this article was funded by TUBITAK Project No: 117Y392 and Kocaeli University Research Foundation (KOU-BAP 2017/099 HD). The authors thank Andrea Risplendente for his assistance during electron microprobe analyses. We collectively express our gratitude to two anonymous reviewers whose comments have strengthened the paper, and to Prof. Dr. Robert Stern for his excellent editorial handling.

Disclosure statement

No potential conflict of interest was reported by the author(s).

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Additional information

Funding

This work was supported by the Kocaeli Üniversitesi [KOU-BAP 2017/099 HD]; Türkiye Bilimsel ve Teknolojik Arastirma Kurumu [Project No:117Y392].