锆石和磷灰石原位地球化学成分对普朗斑岩铜成矿的指示意义  

In situ geochemical compositions of the zircon and apatite and their implications for the Pulang porphyry Cu mineralization

作　　者：冯乾 黄明亮 胥磊落[1] 毕献武[1] 张兴春[1] 王新松[1] FENG Qian;HUANG Ming-liang;XU Lei-luo;BI Xian-wu;ZHANG Xing-chun;WANG Xin-song(The State Key Laboratory of Ore Deposit Geochemistry,Institute ofgeochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵州贵阳550081 [2]中国科学院大学,北京100049

出　　处：《矿物学报》2019年第6期681-689,共9页Acta Mineralogica Sinica

基　　金：中国科学院战略先导科技专项(B类)(编号：XDB18000000);中国科学院“一带一路”团队项目;国家自然科学基金项目(批准号：41873052);贵州省百层次创新人才项目

摘　　要：普朗斑岩铜矿床是云南中甸地区最大的斑岩型铜矿床,其成矿作用与普朗复式岩体存在密切的成因联系。对普朗复式岩体成矿的第1期石英闪长玢岩和第2期石英二长斑岩,以及不成矿的第3期闪长玢岩开展了锆石原位微量元素和磷灰石原位主量元素成分的研究。结果表明,锆石Ce/Ce*值、Ce4+/Ce3+比值和Ce/Nd比值指示,不成矿的第3期闪长玢岩与成矿的第1期石英闪长玢岩的岩浆相对氧化状态大致相当,且明显高于成矿的第2期石英二长斑岩。磷灰石Cl、OH和SO3成分指示,普朗复式岩体3期斑岩具有相似的岩浆含水量,但成矿的第1期石英闪长玢岩和第2期石英二长斑岩较不成矿的第3期闪长玢岩具有更高的岩浆挥发分Cl含量和硫逸度。岩浆的高氧逸度和硫逸度、富水和富挥发分Cl均是形成斑岩铜矿床的关键因素,普朗不成矿的第3期闪长玢岩与成矿的第1期石英闪长玢岩和第2期石英二长斑岩均具有富水和高氧逸度特征,但第3期闪长玢岩较成矿的第1期石英闪长玢岩和第2期石英二长斑岩具有明显更低的岩浆挥发分Cl含量和硫逸度,这很可能是导致第1期石英闪长玢岩和第2期石英二长斑岩成矿,而第3期闪长玢岩不成矿的重要原因之一。The Pulang porphyry copper deposit is the largest one in the Zhongdian area,Yunnan Province,China.Its mineralization has closely genetic relationship with the Pulang complex,primarily composed of the mineralized quartz diorite porphyry(Phase 1)and quartz monzonite porphyry(Phase 2),and the barren diorite porphyry(Phase 3).In this study,the in-situ analysis of trace elements of zircon crystals,and the in-situ analysis of major elements of apatite grains from porphyries of the Pulang complex have been carried out.The Ce/Ce*values,Ce4+/Ce3+ratios,and Ce/Nd ratios of zircon grains indicate that the relative oxidation state of magma of the barren diorite porphyry is similar to that of magma of the mineralized quartz diorite porphyry,but clearly higher than that of magma of the mineralized quartz monzonite porphyry.Cl,OH and SO3 components of apatites indicate that magmas of all porphyries of three phases have similar H2 O contents,but magmas of mineralized quartz diorite porphyry(Phase 1)and quartz monzonite porphyry(Phase 2)have higher Cl contents and sulfur fugacities than magma of the barren diorite porphyry(Phase 3).The high oxygen and sulfur fugacities and enrichment of H2O and Cl in magmas of porphyries are all the key factors for the porphyry copper mineralization.Magmas of porphyries of three phases in the Pulang complex are all characterized with the high oxygen fugacity and enrichment of H2O.However,magma of the barren diorite porphyry(Phase 3)has clearly lower Cl contents and sulfur fugacity than magmas of mineralized quartz diorite porphyry(Phase 1)and quartz monzonite porphyry(Phase 2).The differences in Cl contents and sulfur fugacity between magmas of the mineralized and barren porphyries are most likely one of the significant causes leading to mineralization in the quartz diorite porphyry(Phase 1)and quartz monzonite porphyry(Phase 2),but no mineralization in diorite porphyry(Phase 3).

关 键 词：普朗复式岩体 锆石 磷灰石 原位地球化学成分 

分 类 号：P579[天文地球—矿物学] P611[天文地球—地质学]