西秦岭温泉斑岩钼矿床复式岩体岩浆氧逸度对成矿的制约  

Constraints of magmatic oxidation state on mineralization in the Wenquan porphyry molybdenum deposit,West Qinling,China

作　　者：于皓丞 邱昆峰[1,2,3] 庞瑶 周俊烈 耿建珍 勾宗洋 王瑀 YU Haocheng;QIU Kunfeng;PANG Yao;ZHOU Junlie;GENG Jianzhen;GOU Zongyang;WANG Yu(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,School of Earth Sciences and Re sources,China University of Geosciences(Beijing),Beijing 100083,China;State Key Laboratory for Mineral Deposits Research,Nanjing University,Nanjing 210023,China;Department of Geology and Geological Engineering,Colorado School of Mines,Golden,CO 80401,USA;Sichuan Earthquake Administration,Chengdu 610041,China;Gansu Non-Ferrous Metals,Lanzhou 730000,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]南京大学内生金属矿床成矿机制国家重点实验室,江苏南京210023 [3]美国科罗拉多矿业学院地质与地质工程系,戈登80401 [4]四川省地震局,四川成都610041 [5]甘肃有色金属地质勘查局,甘肃兰州730000

出　　处：《地学前缘》2019年第5期255-269,共15页Earth Science Frontiers

基　　金：国家自然科学基金项目（41702069,41730426）;内生金属矿床成矿机制研究国家重点实验室开放研究基金项目（2017-LAMDK05）;西部矿产资源与地质工程教育部重点实验室开放基金项目（310826171109）;人力资源和社会保障部博士后国际交流计划派出项目（20170108）;教育部教师基本科研业务费项目（2652018125,2652018141）;科学技术部高等学校学科创新引智计划项目（BP0719021）

摘　　要：温泉斑岩钼矿床位于西秦岭东段,是该区发现的一个具有大型矿前景的斑岩型钼矿床。围岩温泉复式岩体发育5个岩相单元(Ⅰ~Ⅴ),钼矿体(化)主要赋存于复式岩体Ⅱ单元富含镁铁质包体的黑云母二长花岗斑岩和Ⅲ单元富含镁铁质包体的似斑状二长花岗岩及其接触带内,其余岩相(包括单元Ⅴ似斑状正长花岗岩)很少发育矿化。该研究使用全岩地球化学数据和锆石微量元素含量数据,计算得到不同岩相单元的氧逸度。Ⅱ单元和Ⅲ单元含矿斑岩相对氧逸度ΔFMQ分别为1.35和1.38。Ⅰ单元黑云母花岗岩和Ⅳ单元二长花岗斑岩相对氧逸度ΔFMQ分别为-0.61和-0.73,明显低于含矿斑岩。富集地幔物质的加入与否可能是造成不同岩相之间氧逸度差异的主要原因。高氧逸度的熔体可以将秦岭地区古生代富钼沉积物中的钼氧化萃取出来,并使钼与高价态硫络合,不断在熔体中高度富集,最终成矿。氧逸度较低的熔体很难萃取和保存足够的钼,因而很少发育矿化。The Wenquan porphyry Mo deposit,containing 0.12 Mt Mo at average Mo grade of 0.048%,is closely associated with the concentrically zoned multiphase Wenquan batholith in the West Qinling Orogen.The Wenquan batholith consists of five units:biotite granite(Ⅰ),biotite monzogranite porphyry(Ⅱ),porphyritic monzogranite(Ⅲ ),monzogranite porphyry(Ⅳ )and porphyritic syenogranite(Ⅴ ).The disseminated and veinlets Mo mineralization is genetically associated with the biotite monzogranite porphyry and porphyritic monzogranite phases and hosted mafic enclaves.We calculated the oxygen fugacity(f(O2))of the multiphase Wenquan batholith by using a relation for cerium redox equilibria in silicate melts and an internally-consistent model for zircon-melt partitioning of Ce.The ore-bearing porphyries had average f(O2) of ΔFMQ=1.35 and ΔFMQ=1.38 for unitsⅡ andⅢ,respectively,while the barren porphyries had lower f(O2)values ofΔFMQ=-0.61 and ΔFMQ=-0.73 for unitⅠ and Ⅳ,respectively.We therefore proposed that oxidized magmas can be associated with enriched mantle.Molybdenum can be extracted from high oxygen fugacity melt in the Paleozoic Mo-rich sediments in the Qinling Orogen.The increasing of oxygen fugacity is furthermore beneficial to concentrating Mo in the residual melt,favorable for Mo mineralization.

关 键 词：氧逸度 温泉钼矿床 斑岩型矿床 西秦岭 

分 类 号：P618.65[天文地球—矿床学] P611.1[天文地球—地质学]