摘要
公家坪金矿是北秦岭新近勘查的一处中型金矿床,矿体以石英脉型为主,产于中—晚三叠世花岗(斑)岩的NW-NWW向脆韧性断层中。矿石以富Au-Ag-Te-(Bi)矿物为特征,然而关于其矿物共生组合、成矿物理化学条件及金的富集机理尚不清楚。显微矿相学观察和电子探针分析表明:公家坪金矿床的碲化物有碲金银矿、碲银矿、六方碲银矿、碲铅矿、碲铋矿、辉碲铋矿和硫碲铋矿B;金矿物以含金碲化物和自然金为主,且自然金成色为835~889,平均值为855。矿物共生关系、流体包裹体及热力学相图研究结果显示:主成矿阶段石英中的原生流体包裹体主要有3种类型,即H_(2)O-NaCl包裹体(W型)、CO_(2)-H_(2)O-NaCl包裹体(C型)和纯CO_(2)包裹体(PC型);成矿流体总体属于中温(180~320℃)、低盐度(0.7%~8.7%)、中酸性、低氧逸度、高碲逸度及相对低硫逸度的偏还原CO_(2)-H_(2)O-NaCl±CH_(4)体系。其中,热液成矿期Ⅱ阶段以富铋(硫)碲化物(碲铋矿+辉碲铋矿+硫碲铋矿B)为特征,含矿热液的pH=4.1~6.2、log f O_(2)=-42.0~-36.5、log f Te_(2)=-13.2~-10.5和log f S_(2)=-14.4~-11.1;Ⅲ阶段发育大量Au-Ag-(Pb)-Te矿物(自然金+碲金银矿+碲银矿+六方碲银矿+碲铅矿),成矿流体的pH=4.1~5.7、log f O_(2)=-42.0~-36.5、log f Te_(2)=-10.5~-9.5和log f S_(2)=-14.4~-11.9。富Au-Ag-Te熔体对热液中金的抽提,可能是导致金发生富集沉淀的关键机制。
The Gongjiaping is a recently defined,middle-sized gold deposit in the North Qinling terrane.Ore bodies occur primarily as quartz veins within the NW-to NWW-trending brittle-ductile faults.The ores are characterized by an Au-Ag-Te-(Bi)mineral assemblage;however,the textures of this assemblage,the ore-forming physicochemical conditions,and the mechanisms of gold enrichment remain poorly constrained.Integrated micro-mineralogical observations and electron microprobe analysis reveal that tellurides are predominately petzite,hessite,stützite,altaite,tellurobismuthite,tetradymite,and joseite-B.Gold occurs mainly in gold-bearing tellurides and as native gold,with a fineness of 835889(mean of 855).The physicochemical conditions of the metallogenic fluids at different stages were reconstructed based on mineral equilibria diagrams and fluid inclusion analysis.Three primary types of fluid inclusions were identified in main-ore stage quartz:H_(2)O-NaCl inclusions(type W),CO_(2)-H_(2)O-NaCl inclusions(type C),and pure CO_(2)inclusions(type PC).The ore-forming fluids are characterized by medium temperature(180320℃),low salinity(0.7%8.7%),medium-to-low pH,low oxygen fugacity,high tellurium fugacity,relatively low sulfur fugacity,and belonged to a reduced CO_(2)-H_(2)O-NaCl±CH_(4)system.The metallogenic fluid of stageⅡhas pH,log f O_(2),log f Te_(2),and log f S_(2)values ranging from 4.1 to 6.2,-42.0 to-36.5,-13.2 to-10.5,and-14.4 to-11.1,respectively,with typical Bi-Te-(S)mineral assemblages of tellurobismuthite+tetradymite+joseite-B.Nevertheless,plenty of Au-Ag-(Pb)-Bi minerals(native gold+petzite+hessite+stützite+altaite)are present in the stageⅢveins,which formed at the conditions of pH=4.15.7,log f O_(2)=-42.0-36.5,log f Te_(2)=-10.5-9.5,and log f S_(2)=-14.4-11.9.Our results suggest that the scavenging of Au from hydrothermal fluids by Au-Ag-Te-rich melts was a key mechanism for gold enrichment and precipitation in the Gongjiaping gold deposit.
作者
葛战林
高永宝
章永梅
顾雪祥
郑艳荣
马承
郝迪
董阳阳
冯李强
GE Zhanlin;GAO Yongbao;ZHANG Yongmei;GU Xuexiang;ZHENG Yanrong;MA Cheng;HAO Di;DONG Yangyang;FENG Liqiang(Xi’an Mineral Resources Survey,China Geological Survey,Xi’an 710100,China;Technology Innovation Center for Gold Ore Exploration,China Geological Survey,Xi’an 710100,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;National 305 Project Office,People’s Government of the Xinjiang Uygur Autonomous Region,rümqi 830000,China;Command Center of Natural Resources Comprehensive Survey,China Geological Survey,Beijing 100055,China)
出处
《地学前缘》
北大核心
2026年第2期105-126,共22页
Earth Science Frontiers
基金
自然资源综合调查指挥中心科技创新基金项目(KC20240006)
陕西省自然科学基础研究计划资助项目(2024JC-YBQN-0349)
国家自然科学基金重点项目(42130804)
中国地质调查局项目(DD20251166,DD20230060)
新疆维吾尔自治区重点研发计划项目(2023B03016)
新疆维吾尔自治区“天池英才”计划项目。
关键词
富集机制
矿物共生组合
碲化物
公家坪金矿床
北秦岭
enrichment mechanism
mineral association
tellurides
Gongjiaping gold deposit
North Qinling terrane
