The~1.4 GaA-type granitoids in the“Chottanagpur crustal block”(India),and its relocation from Columbia to Rodinia?  

作　　者：Nicole Sequeira Abhijit Bhattacharya Elizabeth Bell 

机构地区：[1]Department of Geology and Geophysics,Indian Institute of Technology,Kharagpur 721302,India [2]Department of Earth,Planetary and Space Sciences,University of California,595 Charles Young Drive East,Los Angeles,CA 90095-1567,USA [3]School of Earth,Ocean and Atmospheric Sciences,Goa University,Taleigao,Goa 403516,India

出　　处：《Geoscience Frontiers》2022年第2期405-429,共25页地学前缘（英文版）

基　　金：the financial support provided by UGC(India)fellowship;the financial support for fieldwork provided through the CPDA funding scheme by Indian Institute of Technology,Kharagpur;Invaluable support by Atreyee Bhattacharya(INSTAAR,Boulder)via internal educational initiative grants at University of Colorado;Boulder for the SIMS geochronology work at UCLA is greatly appreciated;The UCLA Ion Microprobe Laboratory is partially supported by a grant from NSF-EAR’s Instrumentation and Facilities Program(1734856)。

摘　　要：In paleogeographic reconstructions of the Columbia and Rodinia Supercontinents,the position of the Greater India landmass is ambiguous.This,coupled with a limited understanding of the tectonic evolution of the mobile belts along which the mosaic of crustal domains in India accreted,impedes precise correlation among the dispersed crustal fragments in supercontinent reconstructions.Using structural,metamorphic phase equilibria,chronological and geochemical investigations,this study aims to reconstruct the tectonic evolution of the Chottanagpur Gneiss Complex(CGC)as a distinct crustal block at the eastern end of the Greater Indian Proterozoic Fold Belt(GIPFOB)along which the North India Block(NIB)and the South India Block(SIB)accreted.The study focuses on two issues,e.g.dating the Early Neoproterozoic(0.92 Ga)accretion of the CGC with the NIB contemporaneous with the assembly of Rodinia,and documenting the widespread(>24,000 km^(2))plutonism of1.5-1.4 Ga weakly peraluminous,calc-alkalic to alkali-calcic and ferroan A-type granitoids(±garnet)devoid of mafic microgrannular enclaves and coeval mafic emplacements in the crustal block.These dominantly within-plate granitoids arguably formed by asthenospheric upwelling induced partial melting of garnetbearing anatectic quartzofeldspathic gneisses that dominate the Early Mesoproterozoic basement of the block.The major and trace element chemistry of the granitoids is similar to the 1.35-1.45 Ga A-type granitoids in Laurentia/Amazonia emplaced contemporaneous with the 1.5-1.3 Ga breakup of the Columbia Supercontinent.This study suggests the Chottanagpur Gneiss Complex occured as a fragmented crustal block following the breakup of the Columbia Supercontinent;the crustal block was subsequently integrated within India during the Early Neoproterozoic oblique accretion between the NIB and SIB contemporaneous with the Rodinia Supercontinent assembly.

关 键 词：Chottanagpur Gneiss Complex Rodinia accretion Columbia Supercontinent break up Mid-Mesoproterozoic ferroan A-type granitoids 

分 类 号：P588.3[天文地球—岩石学]