四川大梁子铅锌矿成矿物质来源与成矿机制:硫、碳、氢、氧、锶同位素及闪锌矿微量元素制约  

Sources of metallogenic materials and metallogenic mechanism of Daliangzi Ore Field in Sichuan Province: Constraints from geochemistry of S,C,H,O,Sr isotope and trace element in sphalerite

作　　者：袁波[1] 毛景文[2] 闫兴虎[3] 吴越[4] 张锋[1] 赵亮亮[2] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价实验室 [3]金堆城钼业集团有限公司 [4]长江大学地球环境与水资源学院

出　　处：《岩石学报》2014年第1期209-220,共12页Acta Petrologica Sinica

基　　金：国家973项目(2014CB440903);国家自然科学基金项目(40902029);公益性行业专项项目(200911007)联合资助

摘　　要：大梁子铅锌矿床位于扬子地台西南缘,是川滇黔多金属成矿带中大型铅锌矿床之一,其金属储量(Pb+Zn)为180万吨,平均品位11.45%。本文在闪锌矿微量元素地球化学和系统总结S、H、O、C、Sr同位素研究结果的基础上,分析了成矿流体、金属的来源,并探讨了成矿机制。研究结果表明:大梁子矿区闪锌矿Ge/In、Ga/In的比值较大(远大于100),并富集As、Sb和Ag等元素,指示出了成矿温度属于中-低温范畴,有别于矽卡岩型、岩浆热液型铅锌矿床。成矿流体中δ18O水的变化范围为-6.02‰～3.31‰,δD的变化范围为-74.6‰～-40.3‰,推测成矿流体可能起源于大气降水和变质水(建造水)混合。主要脉石矿物热液方解石、白云石δ13C V-PDB值介于-3.5‰～+1.4‰之间,平均值为-1.23‰;δ18O V-SMOW值介于+11.6‰～+18.1‰之间,平均值为14.88‰;表明成矿流体中的CO2为震旦系碳酸盐岩的溶解成因,但受围岩有机碳及大气降水影响强烈。研究区矿石矿物方铅矿、闪锌矿、黄铁矿的δ34S众值出现在10‰～20‰之间;硫酸盐矿物的δ34S为20.2‰～38.7‰,表明还原硫主要来自地层中海相硫酸盐的还原。闪锌矿87Sr/86Sr i的变化范围为0.707137～0.714588,均值0.711951,高于赋矿围岩震旦系灯影组白云岩锶同位素比值(0.70834～0.70861),表明成矿流体可能流经了围岩碳酸盐岩层与基底地层,并与之进行了水岩反应及同位素交换。The Daliangzi Pb-Zn deposit located on the southwestern margin of the Yangtze Craton,with reserve of 1. 80Mt and averaging grade of 11. 45%（ lead ＋ zinc）,is one of the famous high-grade Pb-Zn ore fields in the Sichuan-Yunnan-Guizhou metallogenic belt. Geochemistry of Sr,C,H,O,S isotope and trace element in sphalerite is discussed in this paper in an effort to understand the sources of the ore metals and ore-fluids which cause many different opinions in understanding the genesis of the deposit. The results show that the Ge / In and Ga / In of sphalerites with As,Sb and Ag enriched are much bigger than 100 which indicate the metallogenic environment is of mid-low temperature. The origin of a mix of meteoric and metamorphic（ formation） water can be inferred after the datum that the δ18O H2O values range from- 6. 02‰ ～ 3. 31‰ and the δD values range from- 74. 6‰ ～- 40. 3‰ of the orefluids. δ13C V-PDB and δ18O V-SMOW values of the hydrothermal gangue minerals calcite and dolomite are- 3. 5‰ ～ ＋ 1. 4‰ and ＋ 11. 6 ～ ＋ 18. 1‰,indicating that the CO 2 in the ore-forming fluid was derived from the dissolution of Sinian carbonates and was greatly affected by the meteoric water and organic carbon in the ore bearing rock. The most of δ34S values of sulfides are 10‰ ～ 20‰,and the δ34S values of sulfates are 20. 2‰ ～ 38. 7‰,suggesting that the sulfur should be derived from the in-situ thermochemical reduction of sulfates from the sedimentary strata. The initial87Sr /86Sr values of the ore-forming fluid are 0. 707137 ～ 0. 714588 with the mean value of 0. 711951 which are higher than87Sr /86Sr values（ 0. 70834 ～ 0. 70861） of the host rock Sinian dolomite and lower than87Sr /86Sr values（ 0. 7249 ～ 0. 7288） of the basement and some part of the Sinian formation which had high87Sr /86Sr values,implying that the ore-forming fluid probably migrated through the basement and the Sinian formation and experienced water-rock reaction and isotope exchange among the ore flu

关 键 词：微量元素 同位素 闪锌矿 成矿机制 大梁子 

分 类 号：P595[天文地球—地球化学] P618.42[天文地球—地质学]