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Petrology,geochemistry and geodynamics of basic granulite from the Altay area,North Xinjiang,China
Authors:Li Zi-long  Chen Han-lin  Yang Shu-feng  Dong Chuan-wan  Xiao Wen-jiao
Institution:(1) Department of Earth Sciences, College of Science, Zhejiang University, 310027 Hangzhou, China;(2) Institute of Geology and Geophysics, Chinese Academy of Sciences, 100029 Beijing, China
Abstract:The basic granulite of the Altay orogenic belt occurs as tectonic lens in the Devonian medium- to lower-grade metamorphic beds through fault contact. The Altay granulite (AG) is an amphibole plagioclase two-pyroxene granulite and is mainly composed of two pyroxenes, plagioclase, amphibole and biotite. Its melano-minerals are rich in Mg/(Mg Fe2 ),and its amphibole and biotite are rich in TiO2. The AG is rich in Mg/(Mg Fe2 ), Al2O3 and depletion of U, Th and Rb contents. The AG has moderate ∑REE and LREE-enriched with weak positive Eu anomaly. The AG shows island-arc pattern with negative Nb, P and Ti anomalies, reflecting that formation of the AG -05 be associated with subduction. Geochemical and mineral composition data reflect that the protolith of the AG is calc-alkaline basalt and formed by granulite facies metamorphism having peak P-T conditions of 750 ℃-780 ℃ and 0.6-0.7 Gpa. The AG formation underwent two stages was suggested. In the early stage of oceanic crustal subduction, calc-alkaline basalt with island-arc environment underwent granulite facies metamorphism to form the AG in deep crust, and in the late stage, the AG was thrust into the upper crust.
Keywords:Basic granulite  Petrology and geochemistry  Geodynamics  Altay orogenic belt  North Xinjiang
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