摘要
位于江南造山带中段的湘东北地区是我国华南重要的金铅锌铜钴多金属矿产地之一,栗山铅锌铜多金属矿床是该区近年来找矿勘查新发现的一大型矿床。该矿床位于晚侏罗世—早白垩世幕阜山岩体南缘,矿体主要赋存于岩体及其与地层接触带的构造破碎带内,空间上与岩体关系密切,然而目前关于该矿床的研究十分薄弱。本文采用电子探针和激光剥蚀电感耦合等离子质谱仪开展了闪锌矿的原位微区微量元素分析。微量元素组成分析结果表明,闪锌矿以富集Co、Ga而贫Fe、Cd、Ge为特征,其中Fe、Mn、Cd、Co、Ga等元素以类质同象形式产出,而Cu、Pb、Ag和Sn等元素则还以包裹体形式赋存于闪锌矿中。根据不同微量元素间的相关关系,认为闪锌矿中可能存在Zn^2+←→Fe^2+、4 Zn^2+←→2 Fe^2++Ge^4++□(其中□表示空位)、3 Zn^2+←→2 Cu^++Ge^4+、2 Zn^2+←→Ag^++Sb^3+等简单和复杂替代关系。闪锌矿的Zn/Fe、Ga/Ge、Ge/In、Ga/In比值和Fe温度计等指示闪锌矿形成于中低温(240~250℃)、低硫逸度(lgf(S2)=-13.3^-9.6)环境。栗山矿区闪锌矿的微量元素组成特征有别于金顶砂岩型、SEDEX型、VMS型、MVT型和夕卡岩型铅锌矿,结合低的Cd/Fe(0.03~0.14,平均0.06)、Cd/Mn(1.54~6.30,平均2.91)比值和Ge含量,暗示该矿床成矿作用与岩浆活动有关。综合矿区地质特征和区域构造岩浆演化,认为该矿床是在太平洋板块俯冲后撤引起的伸展构造背景下形成的与燕山期幕阜山岩体有关的中低温岩浆热液充填交代型矿床。该类型矿床闪锌矿具有鲜明的微量元素组成特征,可为判别具相似地质特征的矿床成因提供借鉴。
The northeastern Hunan Province,located in the central segment of the Jiangnan Orogen,holds one of significant Au-Sb-W-Cu polymetallic metallogenic belts in South China.In recent years the large Lishan Pb-Zn-Cu polymetallic deposit was discovered in this area.The deposit is spatially associated with the Late JurassicEarly Cretaceous Mufushan granitoids,and orebodies are hosted within altered fracture zones.In this contribution,we analyzed the trace elemental composition of sphalerite using combined EPMA and LA-ICPMS methods.The results show that sphalerite in the Lishan deposit was enriched in Co and Ga,but depleted in Fe,Cd and Ge.Iron,Mn,Cd,Co and Ga elements occur as solid solution,while other elements,notably Cu,Pb,Ag and Sn are distributed as both solid solution and inclusions.Based on the correlation of different trace elements,we discovered some important coupled substitutions:Zn^2+←→Fe^2+,4Zn^2+←→2Fe^2++Ge^4++□(where□denotes a vacancy),3 Zn^2+←→2Cu^++Ge^4+,and 2Zn^2+←→Ag^++Sb^3+.The Zn/Fe,Ga/Ge,Ge/In and Ga/In ratios,together with Fe geothermometer,indicated a low to medium mineralizing temperature(240-250℃)and low sulfur fugacity(lgf(S2)ranging from-13.3 to-9.6).The trace elemental components of sphalerite in the Lishan deposit revealed a significant distinction from the Jinding,SEDEX,VMS,MVT,and skarn deposits.The low Cd/Fe(0.030.14,av.0.06)and Cd/Mn(1.546.30,av.2.91)ratios,as well as low Ge values,suggested an association of the Lishan Pb-Zn-Cu polymetallic deposit with magmatic hydrothermalism.Based on deposit geology and regional tectonic-magmatic evolution,we propose that the Lishan Pb-Zn-Cu polymetallic deposit formed from a hydrothermal system related to the Yanshanian Mufushan pluton,in an extensional setting related to the roll back of the subducting Paleo-Pacific plate.The trace elemental compositions in this study can provide a reference for the determination of deposit genesis.
作者
郭飞
王智琳
许德如
于得水
董国军
宁钧陶
康博
彭尔柯
GUO Fei;WANG Zhilin;XU Deru;YU Deshui;DONG Guojun;NING Juntao;KANG Bo;PENG Erke(MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,School of Geosciences and Info-Physics,Central South University,Changsha 410083,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;CAS Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;402 Geological Prospecting Party,Bureau of Geology and Mineral Resources Exploration and Development of Hunan Province,Changsha 410004,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2020年第4期66-81,共16页
Earth Science Frontiers
基金
国家重点研发计划“深地资源勘查开采”重点专项(2016YFC0600401)
国家自然科学基金项目(41672077,41302049)
中南大学研究生自主探索创新项目(2018zzts699)
关键词
闪锌矿
微量元素
栗山铅锌铜多金属矿床
幕阜山岩体
湘东北地区
sphalerite
trace element
Lishan Pb-Zn-Cu polymetallic deposit
Mufushan pluton
northeast of Hunan Province
