河南嵩县七亩地沟金矿床成矿机制研究
发布时间：2018-09-19 12:54
【摘要】：河南嵩县七亩地沟金矿床位于华北克拉通南缘的熊耳山地区。矿床赋存在中元古代熊耳群中酸性火山岩中,矿体严格受构造断裂带控制,主要呈脉状产出,矿石以石英脉型占主导,少量蚀变岩型;主要矿石矿物为黄铁矿、少量方铅矿、闪锌矿、黄铜矿等。围岩蚀变以硅化、绢云母化、绿泥石化和碳酸盐化为主。成矿过程从早到晚可分为3个阶段:石英-黄铁矿阶段、黄铁矿-石英-多金属硫化物阶段和石英-方解石阶段。不同成矿阶段的石英和/或方解石中广泛发育流体包裹体。早阶段和中阶段石英中CO_2型流体包裹体、NaCl-H_2O型流体包裹体、含子矿物流体包裹体均有发育,晚阶段方解石中主要发育NaCl-H_2O型流体包裹体。从早阶段到晚阶段,流体包裹体均一温度分别为254℃-397℃、221℃-397℃、162℃-237℃,盐度从早阶段双峰盐度值3.52-21.88wt.%NaCl.eqv和34.95-45.33wt.%NaCl.eqv,经中阶段双峰盐度值0.42-13.83wt.%NaCl.eqv和29.11-42.48wt.%NaCl.eqv,到晚阶段盐度为0.35-5.86wt.%NaCl.eqv。早阶段和中阶段CO_2型包裹体估算的捕获压力为93-199MPa、47-169MPa,晚阶段W型包裹体估算的捕获压力为28-64MPa,相应的成矿深度为3.4-7.2km、1.7-6.2km和2.9-6.5km,指示成矿发生在地壳隆升过程中,区域应力场由挤压向伸展转变。流体沸腾作用是导致硫化物和金等成矿物质快速沉淀的主要机制,通过沸腾和大气降水的混合,成矿流体系统由富CO_2向贫CO_2演化,由变质流体向大气降水演化。本研究在不同中段内系统采集了不同成矿阶段的蚀变岩型和石英脉型矿石样品,利用电感耦合等离子体质谱(ICP-MS)方法分析样品内黄铁矿、全岩微量元素和稀土元素,以此反映成矿流体演化。与碳质球粒陨石相比,各阶段黄铁矿的LREE比HREE更富集,Hf/Sm和Th/La值总体小于1,表明成矿流体中富Cl-,F-含量低。与大陆上地壳相比,黄铁矿微量元素特征表明成矿流体富集亲硫元素Cu、Pb和铁族元素Co、Ni。各阶段黄铁矿Ce异常较弱(δCe值0.60-1.08),表明在成矿过程中物理化学条件为还原环境。Eu~(2+)易于在高温条件下存在,形成正异常,黄铁矿内Eu无异常,早阶段δEu值0.71-1.29,变化范围较大,个别样品δEu值大于1,中阶段δEu值0.89-0.92,变化范围减小,分布在0.90左右,晚阶段δEu值为1.13,δEu值变化特征表明成矿前期流体温度总体较低,成矿后期流体温度较低,可能有较高温度的热液混入。同一热液体系中Y/Ho和Zr/Hf比较稳定,七亩地沟金矿床各成矿阶段Y/Ho和Zr/Hf值变化范围较大,表明成矿各阶段热液体系可能受到干扰,发生了交代作用或有外来热液加入。δ~(18)O水的平均值从早阶段的5.8‰,经中阶段的3.5‰,到晚阶段的-4.4‰,δD值介于-79‰和-96‰之间。成矿流体中的δ13CCO_2值介于-0.9‰和-22.2‰之间,平均为-13.0‰。C、H、O同位素研究表明七亩地沟金矿床的成矿流体可能最初来自变质热液作用,随着时间的推移,逐渐与大气降水混合。
[Abstract]:The Qimu Digou gold deposit in Songxian, Henan Province is located in Xiong'er Mountain area on the southern margin of North China Craton. The ore body is strictly controlled by tectonic fault zone and mainly occurs in vein shape. The ore is dominated by quartz vein type with a small amount of altered rock type, and the main ore mineral is pyrite, a small amount of galena, the ore body is mainly controlled by tectonic fault zone, and the ore body is dominated by quartz vein type with a small amount of altered rock, and the main ore mineral is pyrite with a small amount of galena. Sphalerite, chalcopyrite, etc. The main alteration of surrounding rock is silicification, sericite, green mud petrifaction and carbonization. The metallogenic process can be divided into three stages from early to late: quartz-pyrite stage, pyrite-quartz-polymetallic sulfide stage and quartz-calcite stage. Fluid inclusions are widely developed in quartz and / or calcite at different metallogenic stages. The CO_2 fluid inclusions of CO_2 type and the submineral fluid inclusions of CO_2 type are developed in the early and middle stages of quartz, and the NaCl-H_2O type fluid inclusions are mainly developed in the late stage of calcite. From early stage to late stage, the homogenization temperature of fluid inclusions was 254 鈩，
本文编号：2250180
[Abstract]:The Qimu Digou gold deposit in Songxian, Henan Province is located in Xiong'er Mountain area on the southern margin of North China Craton. The ore body is strictly controlled by tectonic fault zone and mainly occurs in vein shape. The ore is dominated by quartz vein type with a small amount of altered rock type, and the main ore mineral is pyrite, a small amount of galena, the ore body is mainly controlled by tectonic fault zone, and the ore body is dominated by quartz vein type with a small amount of altered rock, and the main ore mineral is pyrite with a small amount of galena. Sphalerite, chalcopyrite, etc. The main alteration of surrounding rock is silicification, sericite, green mud petrifaction and carbonization. The metallogenic process can be divided into three stages from early to late: quartz-pyrite stage, pyrite-quartz-polymetallic sulfide stage and quartz-calcite stage. Fluid inclusions are widely developed in quartz and / or calcite at different metallogenic stages. The CO_2 fluid inclusions of CO_2 type and the submineral fluid inclusions of CO_2 type are developed in the early and middle stages of quartz, and the NaCl-H_2O type fluid inclusions are mainly developed in the late stage of calcite. From early stage to late stage, the homogenization temperature of fluid inclusions was 254 鈩，
本文编号：2250180
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