Tracing remnant of subducted Indian felsic crust: Insight from zircon studies

Abstract

Zircon is a common mineral in nature that survives varied pressure and temperature conditions in the subduction process. It has excellent ability to reveal progressive metamorphic history. Hence it is useful in reconstruct the subduction tectonics in the collisional orogenic belts. In the Tso Morari Gneiss of Indus Suture Zone, Himalaya, eclogite boudins have registered imprint of subduction related ultrahigh-pressure (UHP) metamorphism, this imprint is however missing in the host gneisses. To search the missing link, zircons of the gneisses are studied. The zircons overgrowth and the numerous mineral inclusions indicating, metamorphic responses of the gneisses. The Raman spectra of minerals show, cores of the zircon consist of apatite and quartz, and in the surrounding overgrowth preserves quartz-coesite, c-polymorphs, and other metamorphic minerals. The distribution pattern of these minerals in the zircons is consistent with the Th/U ratios ranging 0.30 to 0.01 recognizes inner magmatic and outer metamorphic domains. The U-Pb ages from inner magmatic, at c. 500 Ma, and from outer metamorphic growth at c.45-42 Ma, suggests the former is the protolith age and later is metamorphic ages of the gneisses. The tectonic interpretation reveals, the subduction of Indian felsic crust to UHP depth (>100km) at c. 45 Ma. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change