安徽天井山金矿成矿流体特征及成矿过程初探

Atentative discussion on the characteristics of ore-forming fluid and ore-forming process of the Tianjingshan gold deposit in Anhui Province

本文在矿床地质调研的基础上，通过主要矿石和蚀变岩石的岩矿相、SEM／EDS、流体包裹体岩相学、显微测温和成分分析，对天井山金矿成矿流体特征、流体来源及成矿过程进行了研究。结果表明，金矿化主要发育于石英脉中，少数产于蚀变围岩中，矿区蚀变以硅化、绢云母化最为发育，另发育含铁碳酸盐化、绿泥石化、黄铁矿化、黄铜矿化、方铅矿化、闪锌矿化等。金矿化发生于石英脉形成后的脆性变形阶段，与之相关的蚀变以绢云母化为主，其次为含铁碳酸盐化和硫化物矿化。金主要以自然金的形式与绢云母共生于石英脉的裂隙中或蚀变围岩中。通过与绢云母同期的流体包裹体研究表明，与金矿化有关的成矿流体为富水、含C02的中高温（286～380℃）、低盐度流体（3．0％-5．1％，NaClcq，质量分数），单个流体包裹体的LA-ICP—MS成分分析表明，成矿流体中富含Pb、Zn、Cu、Bi、Mo、Sb等金属元素。综合流体包裹体中水的H同位素组成和流体成分特征，成矿流体主要为岩浆水的贡献。含Co，的岩浆流体沿活化的先期断裂上升并发生流体沸腾，在流体沸腾过程中CO2进入气相而改变了流体的pH值，造成金和其它金属硫化物的沉淀，同时形成石英裂隙中和围岩中的绢云母化、含铁碳酸盐化等蚀变。

place after the formation of quartz veins and took place during the brittle deformation stage of quartz. Native gold has been found together with sericite as infillings in quartz fractures or as cement of quartz breccia. Fluid inclusion analyses indicate that the ore-forming fluid is a water-rich and CO2-bearing fluid characterized by middlehigh temperature （286-380℃） and low salinity （3.0% --5.1% Nacleq）. The LA-ICP-MS analyses of fluid in- clusions in quartz reveal high Pb, Zn, Cu, Bi, Mo and Sb in the fluid. The H isotope measurements together with the enrichment of polymetallic components in ore-forming fluid imply an obvious magrnatic origin. The up- ward migration of the magmatic fluid along the reactivated fault and the decreasing of temperature and pressure caused the boiling of the fluid. During the boiling process, the CO2 preferentially went into the vapor phase and resulted in pH change of the ore-forming fluid. The change of pH caused the precipitation of gold and sulfides and also generated sericitization and Fe-carbonation.