黑龙江省东宁县五道沟金矿成矿流体特征及矿床成因

五道沟金矿位于太平岭金-铜多金属成矿带,矿体呈脉状赋存于下二叠统双桥子组碳质板岩中,并严格受NE向断裂控制。根据野外观察和岩相学研究,将五道沟金矿成矿划分为早期石英阶段、石英-黄铁矿阶段、石英-碳酸盐阶段3个阶段,其中石英-黄铁矿阶段为主要成矿阶段。石英流体包裹体显微测温和拉曼光谱分析表明,金成矿期流体为中低温、低盐度的含CO₂流体。氢氧同位素分析表明,成矿流体是岩浆水和大气降水的混合流体。黄铁矿微量元素特征表明矿区内黄铁矿为岩浆热液成因;矿石硫同位素数据显示其具有岩浆硫和地层硫的混合特征。铅同位素组成图上,矿石铅、围岩铅和岩浆岩铅三者呈线性关系,具有同源特征,矿石中²⁰⁷Pb/²⁰⁴Pb和²⁰⁸Pb/²⁰⁴Pb值明显高于围岩的相应值,暗示了矿石铅为围岩铅淋滤产物。矿石同位素特征表明双桥子组碳质板岩应为金矿矿源层。综合矿床地质特征、流体包裹体和H-O-S-Pb同位素分析,认为五道沟金矿为造山型金矿。

Ore-forming Fluid Characteristics and Genesis of the Wudaogou Gold Deposit in Dongning County,Heilongjiang Province

The Wudaogou gold deposit is located at Dongning County,Heilongjiang Province,south part of Taipingling Au-Cu polymetallic metallogenetic belt.Au mineralization is mainly presenting as vein type in Lower Paleozoic Shuangqiaozi Formation carbonaceous slate,the distribution of the orebodies is controlled by NE-trending ductile shear zones and faults.We have distinguished three paragenetic stages,i.e.,early quartz stage,followed by quartz-pyrite stage and quartz-carbonate stage,with gold being introduced mainly in the second stage.The ore-forming fluids of the Wudaogou deposit are characterized by moderate-low temperature,low salinity,belonging to an H2O-NaCl-CO2 system.Theδ18OH2O andδDH2O values for the gold-bearing quartz indicate that the ore-forming fluids were a mixture of magmatic and meteoric waters.The trace elements of pyrite from gold-bearing ores show a characteristic of hydrothermal origin.And theδ34 S values suggest a mixed source for sulfur,i.e.,the deep-seated magmatic and sedimentary rocks.The 206Pb/204 Pb,207Pb/204 Pb and 208Pb/204Pb values of gold-associated pyrite show a broad linear correlation with those of the local magmatic and countryrock,implying that lead and possibly gold relate to these sources.Whereas the lead isotope compositions of ores(especially the value of 207Pb/204Pb and 208Pb/204Pb)are higher than those of the Shuangqiaozi Formation slate and the diorite.This indicates that the lead may be a product of leaching of the hosted-carbonaceous slate,which suggests that the ore metals originated from the Shuangqiaozi Formation.Integrating the data obtained from this study on geology,fluid inclusions,and H-O-S-Pb isotope systematics,we suggest that the Wudaogou gold deposit is an orogenic gold deposit.