广西大厂矿田锡多金属矿床与矽卡岩型锌铜矿床地球化学特征差异及成因关系分析  

Different Geochemical Characteristics and Genetic Link between Sn-polymetallic Deposit and Skarn Zn-Cu Deposit in the Dachang Ore Field, Guangxi

作　　者：张健[1,2] 黄文婷 陈喜连[1,2] 伍静 任龙 梁华英 陈玲[4] ZHANG Jian;HUANG Wenting;CHEN Xilian;WU Jing;REN Long;LIANG Huaying;CHEN Ling(Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;College of Resources,Environment and Materials,Guangxi University,Nanning 530004,Guangxi,China;Guangxi Key Laboratory of Marine Disaster in the Beibu Gulf,Qinzhou University,Qinzhou 535011,Guangxi,China)

机构地区：[1]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 [2]中国科学院大学,北京100049 [3]广西大学资源环境与材料学院,广西南宁530004 [4]钦州学院广西北部湾海洋灾害研究重点实验室,广西钦州535011

出　　处：《大地构造与成矿学》2019年第6期1186-1199,共14页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(41772065、41421062);973项目(2015CB452602)联合资助

摘　　要：广西大厂矿田主要由锡多金属矿床和拉么矽卡岩型锌铜矿床组成,前者产于远离龙箱盖岩体的泥盆系中,而后者产于龙箱盖岩体内外接触带。过去多认为两者属于同一成矿系统,都与龙箱盖岩体有关。本文分析和总结了这两类矿床的成矿流体地球化学特征及硫化物原位铅同位素组成,探讨这两类元素组合不同的矿床是否属于同一成矿系统。锡多金属矿床主要发育含CO_(2)包裹体、水溶液包裹体和少量含石盐子晶包裹体,而拉么矽卡岩型锌铜矿床主要发育水溶液包裹体,表明锡多金属矿化流体比矽卡岩型锌铜矿化流体含有更多CO_(2)。锡多金属矿床流体包裹体的均一温度集中于270~410℃,而拉么矽卡岩型锌铜矿床流体包裹体的均一温度集中在240~325℃。远离岩体的锡多金属矿床矿化温度高于靠近岩体的矽卡岩型铜锌矿床矿化温度,这与同一岩浆成矿系统热液矿床的成矿温度一般从岩体往外逐渐降低不同。100号锡多金属矿床硫化物原位铅同位素组成为:^(208)Pb/^(204)Pb介于38.790~39.048之间、^(207)Pb/^(204)Pb介于15.677~15.752之间和^(206)Pb/^(204)Pb介于18.569~18.691之间。拉么矽卡岩型锌铜矿床硫化物的^(208)Pb/^(204)Pb、^(207)Pb/^(204)Pb和^(206)Pb/^(204)Pb分别为38.731~39.112、15.668~15.762和18.411~18.607。两类矿化铅同位素组成在^(207)Pb/^(204)Pb-^(206)Pb/^(204)Pb和^(208)Pb/^(204)Pb-^(206)Pb/^(204)Pb图解上位于不同的区域,表明两类矿化成矿物质源区不同。两类不同矿床成矿流体CO_(2)含量、He及B同位素组成也不同,其矿化流体来源有一定的差异。此外,龙箱盖岩体黑云母富锡,表明岩浆中的Sn主要为Sn^(4+)置换黑云母中的Ti^(4+),不利于Sn在残余岩浆中富集成矿。上述差异表明大厂矿田锡多金属矿床和矽卡岩型锌铜矿床不是同一岩浆-热液成矿系统的产物,拉么矽卡岩型锌铜矿床和龙箱盖岩体有关,锡多金属矿床可能The Dachang ore field in Guangxi province mainly consists of Sn-polymetallic deposit and skarn Zn-Cu deposit.The former is hosted in the Devonian strata away from the Longxianggai granite and the latter occurs in the contact zone between the strata and the Longxianggai granite.Both types of deposits were previously considered to be related genetically to the Longxianggai granite.In this paper,we analyzed the geochemical characteristics of ore-forming fluids and in-situ lead isotopic compositions of sulfide minerals from these two types of deposits to elucidate whether they belong to the same magmatic-hydrothermal system or not.The Sn-polymetallic deposit mainly contains CO_(2)-bearing and liquid-rich fluid inclusions(FIs)with few daughter-bearing FIs,whereas the skarn Zn-Cu deposit contains mainly liquid-rich FIs,indicating that the ore-forming fluids of the Sn-polymetallic deposit have much more abundant CO_(2) than those of the skarn Zn-Cu deposit.Homogenization temperatures of FIs from the Sn-polymetallic deposit mainly range from 270℃ to 410℃,while those for the skarn Zn-Cu deposit mainly range from 240℃ to 325℃.The ore-forming temperatures of the deposits in the Dachang ore field decrease as the distances between the deposit and the Longxianggai granite increase,indicative of links with a same magmatichydrothermal center.The ^(208)Pb/^(204)Pb,^(207)Pb/^(204)Pb and ^(206)Pb/^(204)Pb of the sulfide minerals from the No.100 Sn-polymetallic deposit range from 38.790 to 39.048,15.677 to 15.752 and 18.569 to 18.691,respectively,while those for the skarn Zn-Cu deposit range from 38.731 to 39.112,15.668 to 15.762 and 18.411 to 18.607,respectively.The different ^(206)Pb/^(204)Pb-^(207)Pb/^(204)Pb-^(208)Pb/^(204)Pb compositions suggest that ore metals of the two types of deposits likely have different sources.The ore-forming fluids of Sn-polymetallic and the skarn Zn-Cu deposits are also different in B and He isotopic compositions and CO_(2) contents,suggesting that their ore-forming fluids were not derived fr

关 键 词：大厂矿田 锡多金属矿床 矽卡岩型锌铜矿床 流体包裹体 原位铅同位素 

分 类 号：P612[天文地球—矿床学]