Mobilization of Cu in the continental lower crust:A perspective from Cu isotopes  

作　　者：Chen-Hao Luo Rui Wang Yun Zhao Jian Huang Noreen J.Evans 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources,and Institute of Earth Sciences,China University of Geosciences,Beijing 100083,China [2]State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing,China [3]SinoProbe Laboratory of Chinese Academy of Geological Sciences,Beijing,China [4]State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China [5]CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China [6]John de Laeter Centre,Curtin University,GPO Box U1987,Perth,WA 6845,Australia

出　　处：《Geoscience Frontiers》2023年第5期17-38,共22页地学前缘（英文版）

基　　金：supported by National Key R&D Program of China(2022YFF0800902);National Natural Science Foundation of China(No.42121002);the Open Research Project from the State Key Laboratory for Mineral Deposits Research,Nanjing University(2022-LAMD-K11);SinoProbe Lab 202204,State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(GPMR202110);the 111 Project(B18048);the Fundamental Research Funds for the Central Universities(2-9-2019-034).

摘　　要：Recent studies have shown that Cu-rich sulfide accumulates in the lower continental crust and serves as a critical reservoir to balance Cu depletion in the upper crust.Recycling of Cu in the lower crust is also assumed to be a major metal source for non-arc setting porphyry Cu deposits.To test this hypothesis and further explore the behavior of Cu in the lower crust,we analyzed the elemental and Cu isotopic compositions of lower crustal rocks from different geological domains.The collected samples include hornblendites from the Kohistan arc,granulite xenoliths and hornblendites from the Gangdese arc,hornblendites and gabbros from the Laiyuan complex in the North China Craton,and hornblendite xenoliths from the western margin of the Yangtze Craton.These lower crustal rocks have experienced varying degrees of primary or secondary sulfide accumulation,with significantly varied Cu contents(11.2 to 145 ppm)andδδ^(65)(1.05‰to 1.40‰).Petrography and geochemistry reveal varying degrees of metasomatism and fluid interaction in these rocks,and based on this,they can be further divided into three groups:Group I includes the Gangdese granulites and Yunnan hornblendites,which perhaps experienced significant metasomatism.This suite of rocks shows enrichment ofδ^(65)(dδ^(65)=0.01‰to 1.40‰),positively correlated with metasomatism(dδ^(65)vs.Ce/Pb).We suggest the secondary sulfides which transformed from sulfates during the interaction between lower crust and arc magma are dominant in these rocks,so the feature of heavy isotope enrichment is inherited.Group II includes Laiyuan hornblendites and gabbros,derived from the same parental magma and emplaced at different depths(hornblendites,23.3–28.1 km;gabbros 8.4–11.1 km).The Cu isotopic compositions are strongly fractionated between these two kinds of rocks,with low dδ^(65)in the hornblendites(0.00‰to 0.28‰)and highly polarized dδ^(65)in the gabbros(1.05‰to 0.81‰).Geochemical indicators and mineral assemblages reveal that fluid interaction is most likely re

关 键 词：Cu isotope of lower continental crust Cu mobilization METASOMATISM Fluid interaction Partial melting 

分 类 号：P542[天文地球—构造地质学]