广西大厂矿田100号锡多金属矿体石英阴极发光与微量元素特征及其对成矿过程的指示  

Cathodoluminescence and Trace Elements of Quartz in No.100 Sn-polymetallic Orebody in Dachang Orefield,Guangxi,and Their Implications for Ore-forming Processes

作　　者：张健 廖娟[2] 黄文婷 伍静[3] 陈喜连 梁华英 ZHANG Jian;LIAO Juan;HUANG Wenting;WU Jing;CHEN Xilian;LIANG Huaying(MOE Key Laboratory of Environment Change and Resources Use in Beibu Gulf,Nanning Normal University,Nanning 530001,Guangxi,China;Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;College of Resources,Environment and Materials,Guangxi University,Nanning 530004,Guangxi,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China)

机构地区：[1]南宁师范大学北部湾环境演变与资源利用教育部重点实验室,广西南宁530001 [2]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [3]广西大学资源环境与材料学院,广西南宁530004 [4]东华理工大学,核资源与环境国家重点实验室,江西南昌330013

出　　处：《大地构造与成矿学》2024年第3期621-636,共16页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(42002080);中央引导地方科技发展资金项目(桂科AD20238013);2020年度广西高校中青年教师科研基础能力提升项目(2020KY09024);南宁师范大学科研启动经费项目(0819-2019L08)联合资助。

摘　　要：广西大厂矿田100号锡多金属矿体赋存于中泥盆统生物礁灰岩中,其品位高(Sn 1.9%、Sb 5.78%、Zn 12.4%、Pb 6.55%、Ag 235 g/t)、规模大(矿石量超过1300万吨),是广西大厂锡多金属矿田中非常重要的矿床。本文分析了该矿体中石英的阴极发光(CL)特征、流体包裹体组合及微量元素含量,探讨该巨型特富矿体的成矿过程。矿体成矿过程可划分为成矿前(Q1a石英及稍晚的Q1b石英+细粒方解石)、锡成矿(Q2石英+锡石+毒砂+黄铁矿)、锌铅锑成矿(Q3石英+闪锌矿+磁黄铁矿+脆硫锑铅矿)和成矿后(Q4石英+方解石+白铁矿细脉)四个阶段。Q1a石英CL发浅蓝绿‒蓝紫色光,发育生长环带,含临界均一的流体包裹体,其Al含量为48~265μg/g;Q1b石英CL发淡紫色光,CL结构复杂,显示破裂‒溶解‒再沉淀特征,含有不混溶流体包裹体组合,其Al含量为942~4357μg/g;Q2石英CL发淡蓝紫色光,发育生长环带,与其共生的锡石含有不混溶流体包裹体组合,其Al含量为159~1768μg/g;Q3石英CL发棕褐色光,CL结构均一,含有不混溶流体包裹体组合,其Al含量为53~122μg/g;Q4石英CL不发光,含有低气液比(~15%)水溶液流体包裹体,其Al含量低于检测限(<50μg/g)。Q1a石英发育的临界均一的流体包裹体可能代表深部超临界岩浆流体的出溶。矿体深部最近发现的砂岩角砾及Q1b石英破碎的CL结构和不混溶流体包裹体组合表明成矿前超临界岩浆流体在深部发生了隐爆。Al含量从Q1a石英到Q1b石英急剧上升可能与隐爆引起的晶体生长速率加快有关。而Al含量从Q1b石英到Q2石英到Q3石英逐渐降低暗示了持续的流体不混溶过程中酸性气体(CO_(2)、HCl)的逸失及礁灰岩消耗了流体的H+,导致流体pH值逐渐升高,该过程对锡石及硫化物的沉淀起到了促进作用。Q4石英中发育的低气液比水溶液流体包裹体可能代表成矿后大气降水的加入。The No.100 Sn-polymetallic orebody is a very important deposit in the Dachang tin-polymetallic orefield.It occurs in the Middle Devonian reef limestone with high ore grades(Sn 1.9%,Sb 5.78%,Zn 12.4%,Pb 6.55%,Ag 235 g/t)and giant resource(>13 Mt ores).This paper used cathodoluminescent(CL)features,fluid inclusion assemblages(FIAs),and trace elements of quartz in the orebody to constrain the ore-forming processes that led to the formation of the ore shoot.The mineralization processes include pre-mineralization(Q1a quartz and later Q1b quartz+fine-grained calcite),Sn-mineralization(Q2 quartz+cassiterite+arsenopyrite+pyrite),Zn-Pb-Sb-mineralization(Q3 quartz+pyrrhotite+sphalerite+jamesonite),and post-mineralization(Q4 quartz+calcite+marcasite veinlet)stages.Q1a quartz is characterized by a pale-bluish-green to bluish-violet CL emission,subtle growth zone,critical-homogenization FIAs,and Al contents of 48-265μg/g.Q1b quartz shows a pale purple CL emission and complex CL textures,indicative of crack,dissolution,and reprecipitation processes,and it contains immiscible FIAs and Al contents of 942-4357μg/g.Q2 quartz exhibits pale bluish-violet CL emission with growth zone,with Al contents of 159-1768μg/g.Cassiterite associated with Q2 quartz hosts immiscible FIAs.Q3 quartz is characterized by a light to dark brown CL emission with homogenous CL textures,with immiscible FIAs and Al contents of 53-122μg/g.Q4 quartz shows no CL emission and hosts aqueous FIAs with low vapor/liquid ratios(ca.15%)with Al contents below the limit of detection(<50μg/g).The critical-homogenization FIAs in Q1a quartz likely represent supercritical fluids exsolved from the granite at depth.The sandstone breccias recently found at the bottom of the ore shoot,together with the cracked CL textures and immiscible FIAs of Q1b quartz indicate that crypto-explosion of the supercritical magmatic fluids occurred before mineralization.The sharp increase in Al content from Q1a quartz to Q1b quartz may be related to the increase in crystal growth rates ca

关 键 词：阴极发光 石英微量元素 成矿过程 100号锡多金属矿体 广西大厂矿田 

分 类 号：P612[天文地球—矿床学]