桂西北金牙金矿床成矿流体性质与成矿机制  

Metallogenic Fluid Properties and Mineralization Mechanism of Jinya Gold Deposit in Northwest Guangxi

作　　者：李欣航 白令安[1] 胡乔帆[1,2] 谢兰芳 庞保成[1] 岳志恒[1] Li Xinhang;Bai Ling’an;Hu Qiaofan;Xie Lanfang;Pang Baocheng;Yue Zhiheng(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541004,Guangxi,China;China Nonferrous Metals(Guilin)Geology and Mining Co.,Ltd.,Guilin 541004,Guangxi,China)

机构地区：[1]桂林理工大学广西隐伏金属矿床勘查重点实验室,广西桂林541004 [2]中国有色桂林矿产地质研究院有限公司,广西桂林541004

出　　处：《吉林大学学报（地球科学版）》2023年第3期840-852,共13页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(41762007,41362006);广西自然科学基金项目(2014GXNSFBA118213)

摘　　要：金牙金矿床是滇黔桂“金三角”地区典型的卡林型金矿床之一,矿体明显受断裂构造控制,主要呈似层状、豆荚状、透镜状产于中三叠统百逢组的泥质粉砂岩和粉砂质泥岩中。为探讨成矿流体性质与成矿机制,对研究区流体包裹体进行岩相学研究、显微测温以及激光拉曼成分分析。结果表明,该矿床成矿热液过程可以划分为3个阶段:石英-黄铁矿阶段(Ⅰ)、黄铁矿-毒砂阶段(Ⅱ)和石英-碳酸盐阶段(Ⅲ),其中Ⅱ阶段为主成矿阶段。流体包裹体岩相学研究显示:成矿期流体包裹体主要为气液两相包裹体,液相成分主要为H_(2)O;气体成分主要为CO_(2)、N_(2)、SO_(2)及CH_(4),从早阶段到晚阶段平均均一温度分别为189、157、137℃;平均w(NaCleq)依次为6.01%、4.18%、2.01%,初始成矿流体具有中低温、低盐度、低密度的特征,含CO_(2)、N_(2)和SO_(2)等挥发分的H_(2)O-NaCl体系流体。成矿早期中高温、还原性的盆地热卤水与周围地层发生了强烈的水岩反应,活化迁移其中的Au和S;主成矿期成矿流体在异常高压与断裂活动驱使下不断向上流动,并与白云石中的Fe等元素反应生成黄铁矿和毒砂,同时与大气降水相混合,温度和盐度快速降低,Au等成矿元素大量卸载;成矿晚期,流体中的成矿元素消耗殆尽,大气降水持续混入,温度和盐度明显下降,成矿作用结束。成矿机制为流体混合与水岩反应。Jinya gold deposit is one of the typical Carlin-type gold deposits in the“Golden Triangle”area of Yunnan,Guizhou and Guangxi provinces.The ore bodies are obviously controlled by fault structures and are mainly layered,pod-shaped,and lenticular in argillaceous siltstone and silty mudstone of the Middle Triassic Baifeng Formation.In order to explore the metallogenic fluid properties and mineralization mechanism,the petrographic study,micro temperature measurement and Laser Raman spectroscopy analysis on the fluid inclusions in the study area were carried out.The metallogenic hydrothermal process of this deposit can be divided into three metallogenic stages:Quartz-pyrite stage(Ⅰ),pyrite-arsenopyrite stage(Ⅱ)and quartz-carbonate stage(Ⅲ),and stageⅡis the main metallogenic stage.The petrographic study of fluid inclusions shows that the fluid inclusions in the metallogenic period are mainly two-phase vapor inclusions,and the liquid phase is mainly water;The gas composition is mainly CO_(2),N_(2),SO_(2) and CH_(4),and the average homogenization temperature fromⅠstage toⅢstage is 189,157,and 137℃,respectively;The average w(NaCleq)is 6.01%,4.18%,and 2.01%in sequence.The initial ore-forming fluid is characterized by H_(2)O-NaCl system fluid with medium-low temperature,low salinity,low density and contains volatile components such as CO_(2),N_(2) and SO_(2).In the early stage of mineralization,the hot brine in the basin with medium-high temperature and reducibility had a strong water-rock reaction with the surrounding strata,activating and migrating Au and S;In the main metallogenic period,the ore-forming fluid continuously flows upward driven by abnormally high pressure and faulting activities,and reacts with Fe and other elements in dolomite to form pyrite and arsenopyrite.At the same time,it mixes with atmospheric precipitation,the temperature and salinity drop rapidly,and Au and other ore-forming elements are unloaded in large quantities.In the late stage of mineralization,the ore-forming elements in t

关 键 词：流体包裹体 成矿流体来源 矿床成因 金牙卡林型金矿床 滇黔桂“金三角” 

分 类 号：P618.51[天文地球—矿床学]