The youngest eclogite in central Himalaya: P-T path, U-Pb zircon age and its tectonic implication

Relict omphacite inclusions have been discovered in mafic granulite at Dinggye of China, confirming the existence of eclogite in central Himalayan orogenic belt. Detailed petrological studies show that relict omphacite occur as inclusions in both garnets and zircons, and the peakmineral assemblage of eclogite-facies should be garnet, omphacite, rutile, muscovite and quartz whichwas strongly overprinted by granulite-facies minerals during the exhumation. Phase equilibriamodeling and associated geothermometer predict that the minimum P-T conditions for peak eclogite-facies stage are 720-760 degrees C and 20-21 kbar, and those of overprinted granulite-facies are 750 degrees C and 7-9 kbar in water-undersaturated condition. Thus, a near isothermal decompression P-T path for central Himalayan eclogite has been obtained. Zircon SHRIMP U-Pb dating of two studied eclogite samples at Dinggye yields the peak metamorphic ages of 13.9 +/- 1.2 Ma and 14.9 +/- d 0.7 Ma, respectively, which indicates that the Dinggye eclogite should be the youngest eclogite in Himalayan orogenic belt. Geochemical characteristics and zircon analyses showthat the protoliths of eclogite in Dinggye are predicted to be continental rift-related basaltic rocks. The eclogite at Dinggye in central Himalaya should be formed by the crustal thickening during the long-lasting continental overthrusting by Indian plate beneath Euro-Asian continent, and its exhumation process may be related with channel flow and orogen-parallel extension. In themiddleMiocene (similar to 14 Ma), Indian continental crust had reached at least similar to 65 km depth in southern Tibet. (C) 2015 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.