河南省石寨沟金矿床成矿流体特征及硫铅同位素研究

Fluid inclusion and S, Pb isotope study of the Shizhaigou gold deposit in Henan Province

河南省石寨沟金矿床位于华北克拉通南缘华熊地块崤山地体内,矿区出露地层为中元古界熊耳群马家河组和许山组的中基性-中酸性火山岩,侵入岩为中酸性岩体,断裂破碎带控制着矿体的产出。矿石以块状、浸染状和角砾状构造为主,属蚀变岩型。围岩蚀变包括硅化、绢云母化、黄铁绢英岩化、碳酸盐化和绿泥石化。成矿过程初步划分为石英-黄铁矿阶段、石英-多金属硫化物阶段和石英-碳酸盐阶段,金主要沉淀于石英-多金属硫化物阶段。石英-多金属硫化物阶段发育富液两相包裹体、富气两相包裹体和含CO2三相包裹体,包裹体均一温度峰值介于260-320℃,盐度介于2.0%-9.0%NaCl eqv;石英-碳酸盐阶段仅发育富液两相包裹体,均一温度峰值介于140-200℃,盐度介于5.6%-8.1%NaCl eqv。流体不混溶作用是金沉淀的主要机制。该矿床矿石中硫化物的δ34S值变化于+3.7‰-+7.7‰,平均为+5.6‰。矿石的铅同位素比值变化较小,206Pb/204Pb=16.951-17.035,207Pb/204Pb=15.370-15.466,208Pb/204Pb=37.188-37.512。矿石铅同位素组成明显高于熊耳群火山岩,低于花山岩体铅同位素组成,而与太华群变质岩铅同位素组成相似,表明成矿物质主要来自太华群。

The Shizhaigou gold deposit,located in Xiaoshan terrain of Huashan-Xiong＇ershan massif on the southern margin of the North China Craton,is a small gold deposit discovered in recent years.The strata in the Shizhaigou gold orefield are composed of intermediate-basic and intermediate-acid volcanic rocks of the Majiahe and Xushan Formations of the Mesoproterozoic Xiong＇er Group.The intrusions only include minor intermediate-acid intrusive rocks.The fracture zone controls the distribution of the ore bodies.The ores are mainly of massive,disseminated and breccia structures,and classified as altered rock type.The wall rock alterations in the deposit include silicification,pyritization,sericitization,carbonatization and chloritization.The evolution of the hydrothermal mineralization system comprised the quartz-pyrite stage,quartz-polymetallic sulfides stage and quartz-carbonate stage,and gold was manly deposited in the quartz-polymetallic sulfides stage.Fluid inclusions of the quartz-polymetallic sulfides stage are mainly liquid-rich aqueous two-phase,vapor-rich aqueous two-phase and CO2-bearing three-phase inclusions,and their homogenization temperatures and salinities vary from 260°C to 320°C and from 2.0 wt% to 9.0 wt% NaCl equivalent,respectively.The fluid inclusions of the quartz-carbonate stage are mainly composed of liquid-rich aqueous two-phase inclusions,with homogenization temperatures being 140 - 200°C and salinities 5.6 wt% - 8.1 wt% NaCl equivalent,respectively.The immiscible action of ore-forming fluid was the dominant factor for metallic sulfide deposition.The δ34S values of sulfides within the ores vary from ＋3.7‰ to ＋7.7‰,with an average of ＋5.6‰.The 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb ratios of sulfide are in the range of 16.951 - 17.035,15.370 - 15.466 and 37.188 - 37.512,respectively.The composition of lead isotope in the ores are similar to that of the Taihua Group,and higher than that of the Xiong＇er Group but lower than that of the Huashan intrusive rock,indicating that the ore-forming material of the Shizhaigou gold deposit originated from the Taihua Group.