投稿时间：2013-04-26
修订日期：2014-12-20
网络发布日期：2015-03-04
中文摘要:龙江亭矿床地处福建省紫金山矿田的西南部,矿体受北西向断裂控制,产于燕山早期中细粒花岗岩中。含矿岩体整体遭受硅化-绢云母化-伊利石化-蒙脱石化,浅部为强硅化-迪开石化,深部保留有钾化;后期蚀变主要分布在地表,为硅化-高岭土化和褐铁矿化,偶见萤石化、重晶石化、石膏化。矿物组合和穿插关系显示,成矿前为无矿石英脉;成矿期脉体矿物组合为石英-绢云母-黄铁矿-铜硫化物;成矿后脉体矿物组合为石英-方解石±石膏。根据矿石组构和铜硫化物类型,成矿期脉体可细分为3个亚类或阶段:早阶段为黄铁矿-黄铜矿组合,浸染状和网脉浸染状构造,见于矿体深部;中阶段为黄铁矿-黄铜矿-斑铜矿-硫砷铜矿组合,具梳状、胶状或皮壳状构造,见于矿体中部;晚阶段为蓝辉铜矿-铜蓝组合,浸染状或晶簇构造,见于浅部坑道和地表。早阶段脉体矿物含大量富液相包裹体,少量富气相包裹体,均一温度为262~403℃,w(NaCleq)介于0.2%~18.6%,显示中-高温热液的特征;中阶段脉体中的包裹体几乎全部均一到液相,完全均一温度为201~302℃,峰值为250℃,w(NaCleq)介于0.2%~10.1%,总体显示中-低温热液的特征;晚阶段包裹体全部均一到液相,均一温度为117~250℃,w(NaCleq)介于0.4%~9.5%之间,表现出低温、低盐度大气降水热液的特征。根据蚀变类型确定成矿期logf(O2)=-42~-38,pH值=3~5;根据金属矿物组合估算出中阶段logf(S2)=-9±,晚阶段logf(S2)=-6.5±。龙江亭矿床硫逸度-温度变化规律不同于世界上其他岩浆-流体成矿系统,可能经历了2次成矿事件,后期的高硫型浅成低温热液成矿作用叠加在早期的斑岩型矿床之上,一方面造成了复杂多样的蚀变类型、矿物组合和矿石组构,另一方面继承、残留了斑岩型矿床的特征。因此,其属于叠合成因的斑岩型-浅成低温热液型矿床,而非斑岩型与浅成低温热液型之间的过渡。
Abstract:The Longjiangting Cu deposit is located in the southwest of the Zijinshan orefield, Fujian Province. It is hosted in the Early Yanshanian granites and structurally controlled by the NW-trending faults. The ore-hosting granite was wholly altered by quartz-sericite-illite-montmorillonite association, with limited quartz-potassic feldspar zone at depth, but strong quartz-dickite alteration in the shallow part. The post-ore silicification, Kaolinite and limonites alteration are mainly present at the surface. Crosscutting relationships show that the pre-ore, syn-ore and post-ore veins are dominated by mineralogical associations of sulfide-barren quartz, quartz-sericite-pyrite-copper sulfides and quartz-calcite±gypsum, respectively. On the basis of the ore structure and mineral assemblages, the syn-ore veining period can be subdivided into three stages. The early-stage veins mainly occur in the deep part of the orebody, containing pyrite and chalcopyrite as ore minerals which occur as spotted disseminations, disseminated veinlets and stockworks. The middle-stage veins contain pyrite, chalcopyrite, bornite and enargite, and show comb, colloform and crustiform structures. The late-stage veins are represented by the assemblage of digenite-covellite, and show dissemination and drusy structures. The early stage minerals contain aqueous fluid inclusions with variable vapor/liquid ratios, with homogenization temperatures of 262~403℃ (peak around 250℃) and salinity of 0.2%~18.6%. Only liquid-rich aqueous inclusions can be observed in minerals of middle and late stages, which yield homogenization temperatures of 201~302℃ for middle stage, and 117~250℃ for late stage, corresponding to salinities of 0.2%~10.1% and 0.4%~9.5%, respectively, indicating that the epithermal NaCl-H2O system was dominated by meteoric water. According to the types of hydrothermal alterations, the logf(O2) and pH values are estimated to be -42 to -38, and 3 to 5, respectively. The logf(S2) (sulfur fugacity) values in the fluids, estimated from sulfide assemblages, were ca. -9 in middle stage and ca. -6.5 in late stage, respectively. Hence the logf(S2)-T evolution of the Longjiangting mineral system is different from the worldwide porphyry-epithermal systems, suggesting that the Longjiangting Cu deposit was formed by two hydrothermal events, i.e., the early porphyry-type mineralization and the late high-sulfidation epithermal process. It is the epithermal overprinting of a porphyry Cu system that resulted in the complexity in mineral assemblages, alteration types and ore structures and textures in the Longjiangting deposit. On the other hand, the characteristics of the porphyry-type mineralization were partly inherited in the epithermal process. The deposit is a combination of porphyry-type and high-sulfidation epithermal type, rather than a transition from porphyry to epithermal types.
keywords:geochemistry geological characteristics fluid inclusion Longjiangting Cu deposit Zijinshan orefield
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中图分类号：P618.41
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基金项目:本文得到国家科技支撑计划(编号:2009BAB43B04)的资助
引用文本：
陈静,陈衍景,钟军,孙艺,祁进平,李晶.2015.福建省紫金山矿田龙江亭矿床地质和成矿流体特征及成因意义[J].矿床地质,34(1):98~118CHEN Jing,CHEN YanJing,ZHONG Jun,SUN Yi,QI JinPing,LI Jing.2015.Geological and ore-fluid characteristics of Longjiangting Cu deposit in Zijinshan Orefield, Fujian Province, and their genetic implications[J].Mineral Deposits34(1):98~118
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