黑龙江省老柞山矽卡岩-热液脉型金矿成矿流体演化模式

Evolution Mode for the Ore-forming Fluid System of the Laozuoshan Skarn-Magmatic Hydrothermal Vein Gold Deposit,Heilongjiang Province,China

黑龙江省老柞山金矿床位于兴蒙造山带东段佳木斯地块的中北部,矿体主要赋存于华力西期花岗岩和燕山期闪长玢岩中,断裂控矿明显。老柞山金矿床属于矽卡岩-热液脉型金矿床,热液成矿期分为4个阶段,前3个成矿阶段均一温度和盐度变化范围分别为287~472℃,3.21%~50.85%NaCleqv;156~412℃,2.73%~42.65%NaCleqv;155~412℃,2.73%~8.13%NaCleqv。(铁)金矿化集中在Ⅱ阶段,金(铜)矿化集中在Ⅲ阶段,Ⅲ阶段是主成矿阶段。初始流体为含CO_2的盐水体系,随着温压条件、pH值的变化,发生CO_2、H_2S等气体逃逸为特征的沸腾作用,而演化为盐水体系。前3个阶段流体沸腾作用以及后2个阶段岩浆驱动的大气降水溶液的作用导致金矿化。华力西期、燕山期岩浆活动导致成矿流体聚集,裂隙中发育的花岗岩和闪长玢岩在成矿过程中提供了一定的热液和物质来源。

The Laozuoshan gold deposit,located in the Jiamusi Massif uplift zone of eastern Hercynian Xingmeng geosyncline,is hosted in Hercynian granitoids,and Yanshanian granodiorite and diorite porphyrite,which has been obviously controlled by the fracture.This gold deposit belongs to a skarn-magmatic hydrothermal vein deposit,and the hydrothermal ore-forming process can be divided into four stages.For the fluid inclusions from the former three stages,their homogenization temperatures range from 287℃ to 472℃,from 156℃ to 412℃ and from 155℃ to412℃,while their salinities vary from 3.21% NaCl equiv to 50.85 wt.% NaCl equiv,from2.73% NaCl equiv to 42.65 wt.% NaCl equiv and from 2.73 wt.% NaCl equiv to 8.13 wt.%NaCl equiv,respectively.The(Fe)Au mineralization was mainly occurred in the stageⅡ,whilethe Au(Cu)mineralization was dominated by the stageⅢ,and this stage serves as the main mineralization stage.The heat source for the formation of this gold deposit was provided by the original hydrothermal magmatic waters,the deposition of Au,Cu,and Fe was caused by the escape of CO2 and H2S,as well as the input and mixing of meteoric water.Thus,the rapid precipitation of sulfides and gold was caused by the fluid unmixing,boiling and mixing.The fractures were infilled with Hercynian gneissic granite and gneissic granodiorite,and Yanshanian granodiorite and diorite porphyrite,supplying the ore-forming space.Therefore,the evolutionary processes observed in the ore-forming fluid system of this deposit is different from the presented regional crustal continuous mineralization mode,orogenic gold deposits and epithermal gold deposits formed in the geodynamic settings.