闽西南大排铁铅锌多金属矿床O、S、Pb同位素组成及其成因意义  

Oxygen, sulfur and lead isotopic compositions of the Dapai iron-lead-zinc polymetallic deposit in southwestern Fujian Province and their ore-formation significance

作　　者：冯海滨[1] 张达[1] 狄永军[1] 袁远[1] Vatuva Absai 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质通报》2015年第5期930-943,共14页Geological Bulletin of China

基　　金：中国地质调查(编号:12120114028701;12120113089600;1212011085472)项目

摘　　要：对闽西南大排铁铅锌多金属矿床地质特征调查的基础上,分别开展了矿石中主要矿物磁铁矿、石榴子石的O同位素及黄铁矿、闪锌矿和方铅矿的S、Pb同位素测试.结果表明,石榴子石中δ18O值变化范围为3.4‰-6‰,反映了石榴子石矽卡岩可能继承隐伏花岗岩体的O同位素组成;根据磁铁矿的O同位素组成（2.2-4.3‰）所计算的磁铁矿阶段成矿流体的δ18O为9.23‰-11.34‰（500℃）或8.58‰-10.69‰（600℃）,暗示有富集δ18O的CO2融入到成矿流体中;矿石硫化物δ“S组成.变化范围较窄,变化范围为-2.6‰-1.5‰,多数集中在0值分布,具有岩浆硫（0±3‰）的特点;硫化物的Pb同位素组成206Pb/204Pb、207Pb/204Pb、208Pb/204Pb的数值分别为18.486-18.537、15.665-15.712、38.823-38.979,变化范围小,整体上具有壳幔混合且以壳源物质为主的特点.结合对闽西南马坑式铁多金属矿床及闽西南花岗岩年代学讨论认为,大排铁铅锌多金属矿床的形成主要与晚中生代花岗岩浆侵入接触交代作用有关.上述认识对于进一步明确闽西南地区铁多金属矿找矿方向具有重要的理论意义.In this paper, based on an analysis of ore-forming geological conditions of the Dapai iron-lead-zinc polymetallic deposit in southwestern Fujian, the authors chose magnetite and garnet to analyze oxygen isotopic compositions and pyrite, sphalerite and galena so as to determine sulfur and lead isotopic compositions. Studies show that the δ180 values of garnet vary from 3.4‰ to 6‰, in dicating that the oxygen isotopic compositions of garnet skarn might have inherited those of the concealed granite body. The oxygen isotopic compositions of magnetite were used to calculate the g 180 values of the oreforming fluid at the magnetitization stage. They were 9.23%0-11.34%0 at the assumed temperature of 500%2 or 8.58%0-10.69‰ at the assumed temperature of 600%2 respectively. These data indicate that the 1SO-enriched CO2 was dissolved in the ore-forming fluid. The 8 34S from ore sulfides has a small range of-2.6%0-1.5%0, the distribution of values is around the zero, （0±3%0） , a characteristic that implies a rnagmatic sulfur. The 206Pb/204Pb, 207Tpb/204pb and 207Pb/204pb ratios of sulfide ores vary in the ranges of 18.486-18.537, 15.665-15.712 and 38.823-38.979 re spectively. The lead isotopic ratios vary in a small range. A comprehensive analysis of the lead isotopic data indicates that the metallogenic materials of this deposit were closely related to magmatism, which was mainly derived from the lower crust with a bit crustmantle mixing. In combination with Makeng style iron polymetallic deposits of southwestern Fujian and chronologic discussion onMesozoic granites in southwestern Fujia, the authors hold that the formation of the Dapai iron-lead-zinc polymetallic deposit had connection with intrusion and metasornatism of Mesozoic granites. The above understanding has important theoretical significance for determination of prospecting direction of iron polymetaUic ores in southwestern Fujian Province.

关 键 词：O、S、Pb同位素 成矿物质来源 矿床成因 大排铁铅锌矿床 闽西南 

分 类 号：P618.2[天文地球—矿床学]