胶东焦家金矿床成矿过程热液蚀变化学反应数值模拟  

Numerical Simulation of Hydrothermal Alteration Chemical Reactions During Ore-forming Process of the Jiaojia Gold Deposit,Jiaodong Peninsula,China

作　　者：邹艳红[1,2] 张武桥 毛先成[1,2] 刘占坤 ZOU Yanhong;ZHANG Wuqiao;MAO Xiancheng;LIU Zhankun(Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education,Central South University,Changsha 410083,Hunan,China;School of Geosciences and Info-Physics,Central South University,Changsha 410083,Hunan,China)

机构地区：[1]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083 [2]中南大学地球科学与信息物理学院,湖南长沙410083

出　　处：《大地构造与成矿学》2023年第5期1158-1172,共15页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(41872249、42030809);湖南省科技创新计划项目(2021RC4055);中南大学中央高校基本科研业务费专项资金(2021zzts0799)联合资助。

摘　　要：焦家金矿床是胶东金矿集区中典型的破碎带蚀变岩型金矿床,存在明显的蚀变分带特征,然而,热液蚀变分带的形成条件及金沉淀化学反应的空间位置尚不够明确。本文利用TOUGHREACT软件对焦家金矿床含矿热液与围岩化学反应进行了模拟,旨在定量探讨该矿床热液蚀变过程。通过分析含矿热液与围岩发生的化学反应,构建热液蚀变成矿概念模型,模拟计算不同温压条件下成矿流体组分化学平衡浓度以及pH值的变化,研究成矿过程热液蚀变矿物的溶解与沉淀机制。模拟结果显示, Au+的化学平衡浓度在温度从280℃降至180℃的过程中呈明显下降趋势, Fe2+化学平衡浓度与Au+呈现相似的变化趋势,表明金矿物最佳成矿温度范围为180~280℃,成矿流体中Fe2+与[Au(HS)2]-络合物发生置换还原反应,促使金沉淀析出;不同温度和压力条件对成矿元素化学平衡浓度变化的影响表明,温度是控制金沉淀化学反应的关键因素,压力影响相对较小;而pH值模拟结果表明,热液蚀变反应过程中成矿流体pH值升高,成矿环境从酸性逐渐转变为中性、碱性,与传统地质手段分析结果一致,验证了模拟结果的有效性。上述研究结果表明,在温度驱动力作用下,成矿流体沿断裂侧向运移与围岩持续叠加的蚀变作用,形成了蚀变分带;在紧靠断裂带下盘的黄铁绢英岩化带,由于易发生多种蚀变的叠加以及成矿温度、pH值的变化,有利于金的沉淀富集。The Jiaojia gold deposit is featured by obvious alteration zonation,and is one of the typical altered-type gold deposits in the Jiaodong gold province.However,the formation conditions of hydrothermal alteration zonation and the spatial location of chemical reaction associated with gold precipitation are still unclear.To quantitatively discuss the hydrothermal process,we used the TOUGHREACT software to simulate the chemical reactions between ore-bearing fluids and wall rocks of the Jiaojia gold deposit.First,we constructed a conceptual mineralization model related to hydrothermal alteration by discussing the chemical reaction between ore-bearing fluids and wall rocks.Subsequently,we simulated the chemical equilibrium concentration of ore-forming fluids and pH changes under different temperature and pressure conditions,which was used to study the dissolution and precipitation mechanism of hydrothermal minerals during ore-forming processes.The simulation results show that the chemical equilibrium concentration of Au+significantly decreased with temperature from 280℃to 180℃,and the chemical equilibrium concentration of Fe2+showed similar trend,indicating that the favorable gold metallogenic temperature range is 180℃to 280℃,and Fe2+in ore-forming fluids reacts with[Au(HS)2]−to promote gold precipitation.The temperature and pressure conditions influence the chemical equilibrium concentrations of ore elements,nevertheless,temperature is a more critical factor controlling gold precipitation,while the influence of pressure is relatively weak.The pH simulation results show that the pH values of ore-forming fluids increased during the hydrothermal alteration reaction,which means that the ore-forming environment changes from acidic to neutral and/or alkaline.The pH variation during the ore-forming process is consistent with conventional geological observations,and thus validated the simulation results.The above results indicate that the temperature driving lateral migration of ore-forming fluids along the fault res

关 键 词：数值模拟 焦家金矿床 化学反应 热液蚀变 TOUGHREACT 

分 类 号：P618.51[天文地球—矿床学] P628.3[天文地球—地质学]