Petrology, geochemistry and geodynamics of basic granulite from the Altay area, North Xinjiang, China.
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 SigmaREE 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 may 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 degrees C-780 degrees C 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.
Li
Zi-Long
ZL
Department of Earth Sciences, College of Science, Zhejiang University, Hangzhou 310027, China.
Chen
Han-Lin
HL
Yang
Shu-Feng
SF
Dong
Chuan-Wan
CW
Xiao
Wen-Jiao
WJ
D000538:Aluminum Silicates / Q000737:chemistry*; D017636:Asbestos, Amphibole / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*
D000538:Aluminum Silicates; D017636:Asbestos, Amphibole; D005296:Ferrous Compounds; D008903:Minerals; D017640:Silicates; C060346:basalt; C092478:pyroxene; C047410:biotite