摘要
万古地区金矿床成矿流体的性质、来源和演化以及矿床成因类型尚存在争议.本次选择万古地区的江东金矿床,系统开展了不同阶段石英的SEM-CL分析、流体包裹体显微测温、激光拉曼光谱分析以及H-O同位素测试.流体包裹体测试结果表明,成矿流体由中温、中—低盐度的H2O-NaCl-CO2体系逐渐演化为中—低温、中—低盐度的H2O-NaCl体系.H-O同位素测试结果表明:岩浆流体是主要的成矿流体来源,可能来源于燕山期的岩浆活动.金在成矿流体中主要以Au(HS)-2形式运移,流体不混溶作用和水—岩反应可能是金沉淀的主要机制.综合江东金矿床地质特征、流体包裹体特征和H-O同位素研究结果,认为其属于与岩浆活动有关的岩浆热液型金矿床.
Abstract
The debate surrounding the source,properties and evolution of ore-forming fluids and the genesis of gold deposits in the Wangu area are still remains unresolved.To address this issue,the present study focuses on the Jiangdong gold deposit within the Wangu area,conducting a comprehensive analysis of quartz samples from different stages of the deposit.This analysis includes SEM-CL observation,microtemperature measurement of fluid inclusions,laser Raman spectroscopy,and H-O isotopic compositional analysis.Through examination of the relationship between the veins and the symbiotic combination between the minerals,four distinct mineralization stages have been identified.The mineralization stages at the study site are prioritized as follows:(1)quartz-scheelite stage,(2)quartz-pyrite stage,(3)quartz-pyrite-arsenopyrite-polymetallic sulfide stage,and(4)quartz-calcite stage,and the main mineralization stages are the second and third stages.Fluid inclusions within the quartz at each stage were categorized into three types,namely aqueous inclusions(TypeⅠ),aqueous and CO2 three-phase inclusions(TypeⅡ),and pure CO2 inclusions(TypeⅢ).The homogeneous temperatures of the four phases of fluid inclusions range from 264℃to 347℃,255℃to 329℃,194℃to 271℃,and 157℃to 235℃respectively,aand the salinities range from 2.82%to 8.56%NaCleqv,from 1.84%to 9.04%NaCleqv,from 2.24%to 11.23%NaCleqv,and from 1.87%to 8.71%NaCleqv.The H-O isotope analysis indicates that the ore-forming fluids in the Jiangdong gold deposit are predominantly sourced from magmatic fluids,likely associated with magmatic activities during the Yanshanian period.Fluid-rock interactions may have resulted in the early ore-forming fluids being influenced by partially metamorphic fluids.Over the course of mineralization from early to late stages,the composition of the ore-forming fluid transitioned from a medium-temperature and medium-low salinity H2O-NaCl-CO2 system to a medium-low temperature and medium-low salinity H2O-NaCl system.Gold is primarily transported in the form of Au(HS)-2 within ore-forming fluids,with fluid immiscibility and fluids-rock reaction likely serving as the primary mechanisms for gold precipitation.When considering the geological characteristics of the Jiangdong gold deposit,along with fluid inclusion studies and H-O isotope data,it can be classified as a magmatic hydrothermal deposit associated with magmatic activity.
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