Porphyry Cu deposits linked to episodic growth of an underlying parental magma chamber  

作　　者：Yuanchuan ZHENG Lu WANG Chuandong XUE Bo XU Abdul GHAFFAR Zhusen YANG Yongjun LU Limin ZHOU William L.GRIFFIN Zengqian HOU 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources,and School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China [2]ARC Centre of Excellence for Core to Crust Fluid Systems(CCFS)-GEMOC,Macquarie University,New South Wales 2109,Australia [3]Department of Earth Sciences,Kunming University of Science and Technology,Kunming 650093,China [4]Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China [5]Geological Survey of Western Australia,East Perth 6004,Australia [6]Centre for Exploration Targeting and Australian Research Council Centre of Excellence for Core to Crust Fluid Systems(CCFS),School of Earth Sciences,the University of Western Australia,Crawley 6009,Australia [7]National Research Centre for Geoanalysis,Chinese Academy of Geological Sciences,Beijing 100037,China [8]Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China

出　　处：《Science China Earth Sciences》2020年第11期1807-1816,共10页中国科学（地球科学英文版）

基　　金：supported by the National Key Research and Development Program of China(Grant No.2016YFC0600310);the National Natural Science Foundation of China(Grant Nos.41872083 and 41702091);the Program of the China Geological Survey(Grant No.DD20160024-07);the China Fundamental Research Funds for the Central Universities(Grant No.2652018133);the 111 Project of the Ministry of Science and Technology(Grant No.BP0719021)。

摘　　要：Saindak is one of the typical porphyry Cu deposits(PCDs)in the Chagai magmatic arc in Pakistan.Ore-forming porphyries at Saindak PCD are mainly composed of tonalite.Here,we use geochemistry of apatite enclosed in plagioclase phenocrysts from the ore-forming tonalite to constrain the releasing and recharging processes of S and Cl in the underlying parental magma chamber during PCD mineralization.Although apatite inclusions have homogeneous intra-grain S and Cl compositions,there is significant inter-grain S and Cl variations in apatite inclusions located from core to rim in the hosting plagioclase.Such inter-grain S and Cl variation in apatites are coupled with the core-to-rim trends of An,FeO and Mg contents of the hosting plagioclase phenocryst.It indicates that the Saindak PCD likely formed by episodic injection of primitive magmas during the growth of an underlying magma chamber,rather than by one major injection or by addition of mafic melt derived from different source region.Each primitive melt injection introduced essential ore-forming materials such as S and Cl,which were rapidly and effectively released to the coexisting fluids,causing mineralization.Once primitive melt injection stops,signaling the end of growth of underlying magma chamber,mineralization will cease quickly although the hydrothermal system can still survive for a long time.However,the later released fluids are relatively depleted in ore-forming materials,and thus have lower capability to generate mineralization.Accordingly,predominant porphyry-type mineralizations occurred during the growth rather than waning stage of a magmatic system.

关 键 词：APATITE PLAGIOCLASE Episodic injection Parental magma chamber Porphyry Cu deposit 

分 类 号：P618.41[天文地球—矿床学]