湘中成矿带杏枫山Au-W矿床白钨矿特征及地质意义  

Geochemical characteristics of scheelite from Xingfengshan Au-W deposit in Xiangzhong metallogenic belt:Implications on ore genesis

作　　者：雷金泽 张宇[1,2] 时承华[3] 赵廉洁 成玉亮 沈鸿杰 LEI JinZe;ZHANG Yu;SHI ChengHua;ZHAO LianJie;CHENG YuLiang;SHEN HongJie(Key Laboratory ofMetallogenic Prediction of NonferrousMetals and Geological EnvironmentMonitoring,Ministry of Education,Central South University,Changsha 410083,Hunan,China;School of Geosciences and Info-Physics,Central South University,Changsha 410083,Hunan,China;Investment Group of Hunan Nonferrous Metals Industry Co.,Ltd,Changsha 410000,Hunan,China;Hunan Research Academy of Environmental Science,Changsha 410000,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 [3]湖南有色产业投资集团有限责任公司,湖南长沙410000 [4]湖南省环境保护科学研究院,湖南长沙410000

出　　处：《矿床地质》2023年第3期618-638,共21页Mineral Deposits

基　　金：湖南省科技创新计划资助项目(编号:2021RC4055)资助。

摘　　要：杏枫山Au-W矿床位于湘中Au-Sb-W成矿带西部,以发育矽卡岩型钨矿化和席状石英脉型金矿化两套成矿系统为典型特征,明显有别于区域其它Au-W矿床,为进一步研究区域金、钨成矿机制提供了理想对象。文章根据野外穿切关系、矿物共生组合以及结构特征,将杏枫山白钨矿按次序划分为早期矽卡岩型钨矿化中具振荡环带的Sch-1、内部结构均一的Sch-2、多孔状的Sch-3和晚期席状石英脉型金矿化中结构均一的Sch-4。Sch-1和Sch-2的Mo含量和Eu异常(δEu)分别呈现逐渐降低(47.5×10^(-6)→0.044×10^(-6))和升高(1.74→3.18)的趋势,暗示其成矿热液氧逸度的逐步降低,这可能与其富Sr特征(251×10^(-6)~4916×10^(-6))和与矽卡岩矿物共生所指示的强烈水岩反应相关。同时,Sch-1至Sch-3整体上与白马山印支期岩体具有相似的Y/Ho比值,结合前人的年代学研究指示其成矿热液可能来自白马山印支期岩体。Sch-4的低Mo含量(0.014×10^(-6)~0.068×10^(-6))、高δEu(平均值3.96)和与磁黄铁矿的共生关系均揭示席状石英脉型金矿化成矿热液的低氧逸度特征,其高Sr含量(2319×10^(-6)~5329×10^(-6))也说明其形成受到明显的水岩反应控制,这与其脉侧明显的黑云母蚀变晕特征吻合,也揭示水岩反应及其相关的氧逸度下降可能是杏枫山金沉淀的重要控制因素。另外,席状石英脉中电气石的发育及其脉侧的黑云母蚀变晕显示其具高温岩浆热液成矿特征,揭示矽卡岩型钨矿化与席状石英脉型金矿化应分属两次不同的成矿事件,可能对应白马山复式岩体不同时期的岩浆活动,其中矽卡岩型钨矿化与白马山晚三叠世侵入岩相关,石英脉型金矿化则可能与白马山早侏罗世岩浆活动相关,而杏枫山矿床属于早期矽卡岩型钨矿化和晚期席状石英脉型金矿化的叠加复合成矿。The Xingfengshan Au-W deposit,located in the West part of the Xiangzhong Au-Sb-W metallogenic belt,Hunan Province,is characterized by skarn W mineralization and sheeted quartz-vein Au mineralization,which is markedly different from the coexisting Au and W mineralization of other Au-W deposits in this district,and provides a window for the further study of regional Au-W ore-forming mechanism.Four generations of scheelite(Sch-1,Sch-2,Sch-3,and Sch-4)were identified based on the cross-cutting relationship of veins,mineral assemblages,and internal texture of scheelite,namely the skarn tungsten mineralization Sch-1 with oscillating zone,homogeneous Sch-2,and porous Sch-3 in the skarn W mineralization,and Sch-4 with homogeneous texture in the late sheeted quartz-vein gold mineralization.The decreased Mo contents(47.5×10^(-6) to 0.044×10^(-6))and elevated Eu anomalies(δEu,1.74 to 3.18)from Sch-1 to Sch-2 indicate the decreased oxygen fugacity of ore-forming fluids,which may have been related to the intense fluid-rock interaction revealed by the high Sr contents(251×10^(-6)~4916×10^(-6))of scheelite and the coexistence between scheelite and skarn minerals.Meanwhile,the similar Y/Ho ratios of Sch-1 to Sch-3 to the Indosinian plutons of Baimashan imply that the ore-forming hydrothermal of skarn W mineralization may have been derived from the Indosinian Baimashan granite.The low Mo content(0.014×10^(-6)~0.068×10^(-6)),highδEu(average 3.96),and intergrowth with pyrrhotite of Sch-4 reflect low oxygen fugacity of the ore-forming hydrothermal for sheeted quartz-vein gold mineralization.The high Sr contents(2319×10^(-6)~5329×10^(-6))also indicate that the precipitation of Sch4 may be controlled by the intense fluid-rock interaction,conforming to the obvious biotite alteration halo of sheeted quartz veins.Hence,the fluid-rock reaction and the resulting decreased oxygen fugacity may play an important role in the Xingfengshan gold precipitation.Moreover,the occurrence of tourmaline and biotite alteration halo in the sheet

关 键 词：地质学 白钨矿 成矿流体来源 成矿物理化学条件 湘中成矿带 杏枫山Au-W矿床 

分 类 号：P618.67[天文地球—矿床学] P618.51[天文地球—地质学]