河南内乡北部铅锌银矿床成矿物质来源的S、Pb同位素制约

摘要

The large-scale Pb-Zn-Ag deposit in the northern Neixiang County in Henan Province is found in the Erlangping Terrain which is on the north side of Zhu-Xia fault in North Qinling orogenic belt, which formed in deterioration volcano-sediment of the back-arc environment during the Late Proterozoic-Early Paleozoic. Nearly 100 mineral veins have been found, most of which are filled in fault structure of vertical orogenic belt and present layered and bedded single veins, in which the large-scale Yl, Y3, Y6, Y10 and Z2 are typical. We select the sphalerite mineral of Yl, Y3, Y6, and Z2 together with galena mineral of Y10 to test S isotope, and ξ34SV-CDT ranges from 1. 89‰ to 7. 34‰, which indicating that sulfur is mainly from the thermo-chemical sulfate reduction of Paleozoic marine host strata; Pb isotope from galena shows that 206Pb/204 Pb, 207Pb/204Pb and 208Pb/204Pb are 18. 229,4 - 18. 384,5, 15. 608,9 -15. 643,4 and 38. 516,0-38.715,2, respectively, μ value is between 9. 50 and 9. 55, and ω value is between 37. 45 and 38. 35, all above shows that metal ore sources from Paleozoic metamorphic volcano-sedimentary host strata. Studies show that the ore sources of Pb-Zn-Ag deposit in the northern Neixiang County, may come from the Qinling Group and Erlangping Terrain.%河南省内乡县北部大型铅锌银矿床产于北秦岭造山带朱夏断裂北侧的二郎坪地体内,形成于晚元古代—早古生代弧后盆地环境的(变质)火山-沉积建造.矿区已发现铅锌银矿(化)脉近百条,矿脉多呈板状、脉状充填于近垂直造山带的断裂构造中,其中以较大规模的Y1、Y3、Y6、Y10和Z2号脉为代表.在矿床地质研究的基础上,选取Y1、Y3、Y6和Z2号矿脉中闪锌矿矿石和Y10号矿脉中方铅矿矿石进行了S同位素组成分析,δ34SV-CDT范围为1.89‰～7.34‰,指示硫主要来源于赋矿的古生界海相地层中硫酸盐的热化学还原；矿石中方铅矿的Pb同位素组成206Pb/204Pb范围为18.2294～18.3845,207Pb/204Pb范围为15.6089～15.6434,208Pb/204Pb范围为38.5160～38.7152,矿石铅μ值范围为9.50～9.55,ω值范围为37.45～38.35,指示成矿金属物质来源于赋矿的古生界变质火山-沉积地层.研究表明内乡北部铅锌银矿区的成矿物质可能来自秦岭群和二郎坪地层.