新疆包古图斑岩铜矿磁黄铁矿和毒砂成因及其成矿指示意义  

A Study on Genesis of Pyrrhotine and Arsenopyrite from Baogutu Porphyry Copper Deposit on Western Edge of the Junggar Basin,Xinjiang,and Its Geological Significance

作　　者：李文广 申萍[1,2,3] 潘鸿迪 李昌昊[1,2,3] 马阁[1,2,3] 曹冲 LI Wenguang1, 2, 3, SHEN Ping1, 2, 3 , PAN Hongdi4 , LI Changhao1, 2, 3 , MA Ge1, 2, 3 , CAO Chong1, 2, 3(1 . Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029; 2. Institute of Earth Sciences, Chinese Academy of Sciences, Bering, 100029 ; 3. University of Chinese Academy of Sciences, Beijing, 100049; 4. College of Earth Sciences, Chang＇ an University, Xi＇ an, 71005)

机构地区：[1]中国科学院矿产资源研究重点实验室,中国科学院地质与地球物理研究所,北京100029 [2]中国科学院地球科学研究院,北京100029 [3]中国科学院大学,北京100049 [4]长安大学地球科学与资源学院,西安710054

出　　处：《地质论评》2018年第6期1447-1471,共25页Geological Review

基　　金：国家重点研发计划(编号:2017YFC0601206);国家自然科学基金资助项目(编号:41390442、41272109、U1303293);国家支撑计划重点项目(编号:2011BAB06B01)的成果~~

摘　　要：新疆准噶尔盆地西缘包古图斑岩铜矿是中亚成矿域内首例确认的还原性斑岩铜矿,具有区别于氧化性斑岩铜矿的矿物学特征。包古图斑岩铜矿的成矿闪长岩发育钾硅酸盐蚀变和绢英岩化蚀变及少量青磐岩化蚀变,铜矿化主要集中在钾硅酸盐蚀变阶段和绢英岩化蚀变阶段。钾硅酸盐蚀变和绢英岩化蚀变两阶段发育不同的金属矿物共生组合:前者发育磁黄铁矿,具有黄铜矿+辉钼矿+黄铁矿+磁黄铁矿+钛铁矿+闪锌矿±毒砂组合,黄铁矿主要呈细粒—粗粒五角十二面体,富集Cu而亏损As;后者发育毒砂和碲铋矿物,出现与毒砂共结晶的碲化铋以及不含其他硫化物的独立毒砂脉体,具有辉钼矿+黄铜矿+黄铁矿+毒砂+闪锌矿±碲铋矿物组合,黄铁矿主要呈粗粒立方体,黄铁矿和毒砂中均富集Au+Ag+Te+Bi。钾硅酸盐蚀变和绢英岩化蚀变阶段的硫化物具有不同的组成、结构和成分,反映了绢英岩化蚀变阶段As—Au—Ag—Te—Bi矿化和钾硅酸盐蚀变阶段Cu—Mo—Au—Ag矿化叠加的关系。利用磁黄铁矿和毒砂成分反演了其形成温度和硫逸度,钾化蚀变阶段的温度和硫逸度分别为267~600℃和-1. 5^-9. 5;绢英岩化蚀变阶段的温度和硫逸度分别为209~325℃和-15. 8^-9. 7,同时构建了不同阶段的矿物组合相图,结果显示磁黄铁矿的形成和早期低氧逸度流体相关,毒砂的形成与流体温度降低和硫逸度降低相关。同时推断在早阶段Cu—Mo—Au—Ag矿化期和晚阶段As—Au—Ag—Te—Bi矿化期,由于温度和硫逸度存在差异,Cu和As经历了不同的反应沉淀过程。Objectives： Baogutu porphyry copper deposit is the first reduced porphyry copper deposit identified in central Asian metallogenic region,which shows different mineralogy characristics compared to oxidized porphyry copper deposit. Different metallic mineral assemblages are discovered in potassic alteration and phyllic alteration. With pyrrhotine,potassic alteration is characterized by chalcopyrite ＋ molybedenite ＋ pyrite ＋ pyrrhotine ＋ ilmentite ＋sphalerite ± arsenopyrite assemblage. phyllic alteration is characterized by molybedenite ＋ chalcopyrite ＋ pyrite ＋arsenopyrite＋sphalerite±Te—Bi minerals assemblage. pyrrhotine and arsenopyrite are resulted from different effects and show varied geological genetics.Methods： EPMA is employed to distinguish the chemical difference in sulfides. TerraSpec Halo is employed to identify minerals in advanced argillization. SEM is employed to identify the structural difference among sulfides in difference alteration stages.Results： Pyrite in different alteration stages shows difference in morphylogy. The chemical composition of pyrrhotine and arsenopyrite predicts its formation temperature（ potassic alteration： 267 ～ 600℃; phyllic alteration：209 ～ 325℃） and sulfur fugacity（ potassic alteration：-1.5 ～-9.5; phyllic alteration：-15.8 ～-9.7）. Kaolinite,illite and Magnetite are founded in advanced argillization stage.Conclusions： Combine the early research,we thought that there have different mineralization and sulfide assemblages in 1 B potassic alteration stage and 1 C sericite alteration stage. Pyrrhotine is precipatited in early reduced fluid. Arsenopyrite is resulted from the downturn of fS 2 and temperature. 1 B potassic alteration stage and1 C sericite alteration stage has experienced different chemical processes.

关 键 词：还原性斑岩铜矿 磁黄铁矿 毒砂 硫逸度 包古图斑岩铜矿 

分 类 号：P618.41[天文地球—矿床学]