Geochronology,Geochemistry,and Implications of Aplite Dyke in the Giant Jiama Porphyry Copper System,Tibet  

作　　者：QI Jing TANG Juxing LIN Bin YANG Hairui TANG Xiaoqian TANG Pan FANG Xiang ZHANG Tingting LI Faqiao SUN Miao WANG Mengdie CUI Hao XIE Jinling 

机构地区：[1]School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China [2]MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China [3]Institute of Mineral Research,China Metallurgical Geology Bureau,Beijing 101300,China [4]China Mining Federation of Beijing Consulting Center,Beijing 100044,China [5]Southwest University of Science and Technology,Mianyang,Sichuan 621000,China [6]Chinese Academy of Geological Sciences,Beijing 100037,China [7]Development and Research Center,China Geological Survey,Beijing 100037,China [8]Chengdu University of Technology,Chengdu 100059,China [9]Tibet University,Lhasa 850000,China

出　　处：《Acta Geologica Sinica(English Edition)》2023年第5期1406-1421,共16页地质学报（英文版）

基　　金：supported by the National Key Research and Development Program of China(Grant No.2022YFC2905001);National Natural Science Foundation of China(Grant Nos.42272093 and 42230813);Basic Research Fund of Chinese Academy of Geological Sciences(Grant Nos.JKYZD202316,KJ2102,KK2116,and JKY202208);Geological Survey Project(Grant No.DD20221684);China Scholarship Council(Grant No.CSC202206400059)。

摘　　要：Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetallic mineralization.These ore-bearing porphyries include monzogranite,granodiorite,and quartz diorite porphyries.A new granite aplite dyke was found in the south of Jiama.Its age,genesis,and relationship with ore-related magmatism are obscure.Here,its emplacement age and petrogenesis were determined using mineralogy,zircon U-Pb dating,geochemistry,and Sr-Nd-Pb isotope studies.The zircon LA-ICP-MS U-Pb age of the aplite dyke is 16.66±0.21 Ma(n=14,MSWD=0.66),earlier than that of the ore-bearing porphyries(~15 Ma)in Jiama.Furthermore,the aplite exhibits high amounts of silicon(SiO_(2)=73.39%-74.74%),potassium(K_(2)O=5.12%-6.61%),aluminum(Al_(2)O_(3)=14.25%-14.69%),and light/heavy rare earth elements(LREE/HREE=12.12-16.19)as well as negative europium(δEu=0.47-0.72)and weak negative cerium anomalies(δCe=0.84-0.93).The aplite dyke is characteristic of metaluminous-peraluminous I-type granite,which is rich in large-ion lithophile elements(Rb,Ba,Th and U)and depleted in high-field-strength elements(Nb,P and Ti).The aplite dyke and ore-bearing porphyries in the Jiama deposit are the results of a partial melting of the juvenile lower crust,according to whole-rock geochemistry and Sr-Nd-Pb isotope data,but the dyke and ore-bearing porphyries were emplaced from the same magma chamber at different times.Thus,the aplite dyke shows the composition of the early evolution stage of shallow magma in the Jiama deposit and is the product of rapid condensation and crystallization.

关 键 词：U-Pb age Sr-Nd-Pb isotope GEOCHEMISTRY aplite dyke JIAMA 

分 类 号：P618.41[天文地球—矿床学]