High Ba-Sr adakitic charnockite suite from the Nagercoil Block,southern India:Vestiges of Paleoproterozoic arc and implications for Columbia to Gondwana  

作　　者：Pin Gao M.Santosh Cheng-Xue Yang Sanghoon Kwon Mu.Ramkumar 

机构地区：[1]School of Earth Sciences and Resources,China University of Geosciences(Beijing),29 Xueyuan Road,Beijing 100083,PR China [2]Department of Earth Sciences,University of Adelaide,Adelaide,SA 5005,Australia [3]Department of Earth Sciences,Yonsei University,Seoul 03772,Republic of Korea [4]Department of Geology,Periyar University,Salem 636011,India

出　　处：《Geoscience Frontiers》2021年第3期577-596,共20页地学前缘（英文版）

基　　金：funded by Foreign Expert grants to M.Santosh from the China University of Geosciences Beijing,China;partially supported by NRF 2017R1A6A1A07015374 and NRF 2019R1A2C1002211supervised by the Ministry of Science and ICT,Korea to Sanghoon Kwon;funded the Fundamental Research Fund of Central Universities(Grant 2652019210)through CUGB,China。

摘　　要：The Nagercoil block is the southernmost crustal segment of the Southern Granulite Terrane(SGT)in India and is mainly composed of charnockitic rocks and felsic gneisses(charnockite suite).In this study,we present petrologic,geochemical,zircon U-Pb,REE,and Hf isotopic studies on the charnockites and leucogneiss from the Nagercoil block.Based on field investigations and petrologic studies,the charnockites can be divided into garnet-bearing and garnet-absent anhydrous granulite facies rocks with orthopyroxene.The charnockites and leucogneiss show transition from adakites to non-adakitic magmatic rocks,with enrichment in LREEs(light rare earth elements)and LILEs(large ion lithophile elements),and depletion in HREEs(heavy rare earth elements)and HFSEs(high field strength elements).Some of the charnockites and the leucogneiss show typical HSA(high silica adakite)characters,(high SiO_(2),Al_(2)O_(3),Ba-Sr,La/Yb,and Sr/Y).The HSA is considered to have formed from the interaction of slab derived melts and peridotitic mantle wedge.The high Ba-Sr features were possibly inherited from subducted oceanic crust melting under high thermal gradient during Precambrian.The magmas were underplated and subjected to fractional crystallization.Zircon grains from the charnockite and leucogneiss show zoned magmatic cores surrounded by structureless metamorphic rims.Magmatic zircon grains from the charnockites show ages ranging from 1983±8.8 Ma to 2046±14 Ma,and the metamorphic domains show an age range of 502±14 Ma to 547±8.7 Ma.Zircon from the leucogneiss yielded magmatic and metamorphic ages of 1860±20 Ma and 575.6±8.8 Ma.Both charnockites and leucogneiss show two prominent age peaks at 1987 Ma and 568 Ma.The REE data of the zircon grains show LREE depletion and HREE enrichment,with the metamorphic grains showing more depletion in HREE.Zircon Hf isotopic data of the magmatic cores of zircon grains from the charnockite yieldedε_(Hf)(t)values from-1.17 to 0.46 with T_(DM)and T_(DM)~C and age peaks at 2392 Ma and 2638 Ma,suggesting

关 键 词：CHARNOCKITE Adakitic rocks High Ba-Sr granitoids Geochemistry and zircon geochronology Nagercoil block Columbia and Gondwana supercontinents 

分 类 号：P534.3[天文地球—古生物学与地层学] P588.212.3[天文地球—地质学]