Eclogites and garnet clinopyroxenites in the Anrakhai complex, Central Asian Orogenic Belt, Southern Kazakhstan: P-T evolution, protoliths and some geodynamic implications

• Published in: Journal of Asian earth sciences 2018-03, Vol.153, p.325-345
• Main Authors: Pilitsyna, Anfisa V., Tretyakov, Andrey A., Degtyarev, Kirill E., Cuthbert, Simon J., Batanova, Valentina G., Kovalchuk, Elena V.
• Format: Article
• Language: English
• Subjects: Central Asian Orogenic Belt; Eclogite; Garnet pyroxenite; Geothermobarometry; HP metamorphism; Tectonics
• ISSN: 1367-9120; 1878-5786
• DOI: 10.1016/j.jseaes.2017.03.027

[Display omitted] •First HP derivation of metamorphic ultramafic rocks of Anrakhai complex is demonstrated.•Eclogites and garnet clinopyroxenites have evidently experienced a common metamorphic evolution.•Major and REE chemistry of HP rocks indicates an enriched source for their protolith melts.•Protolith for eclogites and garnet clinopyroxenites likely represented a group of differentiated tholeiitic igneous rocks. The Anrakhai Metamorphic Complex (AMC), located in the SE part of the Chu-Ili Mountains of Southern Kazakhstan in the western part of Central Asian Orogenic Belt, exhibits occurrences of HP metamorphic rocks in the form of eclogites and garnet clinopyroxenites with peak metamorphic conditions of 750–850° and 15–19kbar estimated with both conventional geothermobarometric methods and phase diagram modeling. P-T estimates as well as intimate field relations evidently imply a common metamorphic history for eclogites and garnet clinopyroxenites of the AMC. These high-pressure, medium temperature eclogite facies P-T conditions are indicative of a collision or subduction tectonic setting. Major and trace element geochemistry suggests that they probably had a common magmatic origin as part of a suite of differentiated tholeiitic intrusions. Furthermore, distinctive mineral and chemical compositions of these eclogites and garnet clinopyroxenites correspond to the Fe-Ti type of ultramafic rocks suggesting that they may have been derivatives of intraplate tholeiitic melts, introduced into continental crust before HP metamorphism.