东乡盆地虎圩金多金属矿床金属沉淀机制:来自矿物组合和微量元素的限制  

Metal Precipitation Mechanism of Huxu Gold-polymetallic Deposit in Dongxiang Basin:Constraints from Mineral Paragenesis and Trace Elements

作　　者：陈加杰 李增华 许德如 邓腾 陈立泉 周先军[3] 抄尉尉 袁波 杨立飞 廖净 CHEN Jiajie;LI Zenghua;XU Deru;DENG Teng;CHEN Liquan;ZHOU Xianjun;CHAO Weiwei;YUAN Bo;YANG Lifei;LIAO Jing(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China;Geological Party of Jiangxi Nonferrous Metals Geological Exploration Bureau,Yingtan 335003,Jiangxi,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [2]东华理工大学地球科学学院,江西南昌330013 [3]江西有色地质勘查一队,江西鹰潭335003

出　　处：《大地构造与成矿学》2024年第4期737-753,共17页Geotectonica et Metallogenia

基　　金：江西省地质局专项研究项目(2019-1);江西省自然科学基金青年基金项目(20232BAB213064)联合资助。

摘　　要：钦杭结合带中部的虎圩金多金属矿床为东乡火山岩盆地内典型热液矿床,基础地质研究表明该矿床赋矿围岩为侏罗纪-白垩纪石英闪长玢岩和流纹质火山碎屑岩,矿体受断裂构造控制,呈NW向脉状展布,然而有关该矿床的成因类型、金属沉淀机制和成矿过程研究尚欠缺。本文针对该矿床开展详细矿相学和黄铁矿微量元素研究。结果显示,从早到晚,该矿床矿化过程可分为四个阶段:石英-黄铁矿阶段(S1)、石英-黄铁矿-赤铁矿阶段(S2)、石英-多金属硫化物阶段(S3)和石英-赤铁矿阶段(S4)。金主要以自然金的形式存在于S2和S4阶段中;S2阶段黄铁矿(Py2)明显富集Pb、Sb、Bi、W、V、Sc、U、Al和Ti等元素,不同阶段黄铁矿中不可见金含量均较低(均值0.8~1.7μg/g),As(均值517~931μg/g)与Au整体上正相关,局部存在解耦,微量元素变化主要受控于黄铁矿中不同类型矿物包裹体。综合地质特征、矿物组合、矿物结构、微量元素和热力学计算分析显示,该矿床为中硫型浅成低温热液矿床,流体沸腾和流体混合导致的氧逸度快速上升分别是S2和S3阶段自然金沉淀的关键因素,而黄铁矿中的不可见金主要受控于As对黄铁矿晶格的改变,局部受控于动力学过程控制的黄铁矿晶格缺陷。The Huxu gold-polymetallic deposit,located in the Dongxiang volcanic basin,is a typical hydrothermal deposit within the middle part of the Qinzhou Bay-Hangzhou Bay orogenic juncture belt.The host rocks of the deposit are Jurassic-Cretaceous porphyry quartz diorite and rhyolitic pyroclastic rocks.The ore bodies are fault-controlled and occur as NW-striking veins.However,research on the genesis,metal precipitation,and mineralization processes of the deposit is lacking.In this study,detailed mineralogical and trace element analyses of pyrite from the deposit were carried out.The results show that the mineralization of the deposit can be divided into four stages,i.e.,quartz-pyrite stage(S1),quartz-pyrite-hematite stage(S2),quartz-polymetallic sulfide stage(S3),and quartz-hematite stage(S4).Au mainly occurs as native gold in the S2 and S4 stages.Pyrites from S2(Py2)are enriched in Pb,Sb,Bi,W,V,Sc,U,Al,and Ti,which differ from those from S1(Py1).Pyrite of all stages has low invisible gold contents(averaging 0.8-1.7μg/g).The arsenic content(averaging 517-931μg/g)is positively correlated with Au content and is decoupled locally.Trace elements such as Pb,Zn,Cu,Ag,Bi,Sb,W,Al,Ti,and U are mainly controlled by hematite,chalcopyrite,sphalerite,galena,and silicate inclusions in pyrite.Based on the mineral paragenesis,mineral structure,trace elements,and thermodynamic calculations,a rapid rise of oxygen fugacity caused by fluid boiling and mixing was the key factor controlling natural gold precipitation in the S2 and S3 stages,respectively.The invisible gold in pyrite was mainly controlled by the lattice distortion of pyrite due to the intake of arsenic,and locally controlled by pyrite lattice defects resulting from the dynamic process.

关 键 词：中硫型 金多金属矿床 流体沸腾 流体混合 虎圩 钦杭结合带 

分 类 号：P611[天文地球—矿床学]