白秧坪铅锌多金属矿集区东矿带成矿地球化学作用与成矿年龄

通过成矿期方解石的C、O、Sr和含硫矿物的S、Pb同位素，成矿期方解石Sm-Nd测年研究，探讨白秧坪矿集区东矿带矿床成因。测试结果表明，白秧坪矿集区东矿带方解石δ13C_PDB值变化范围-4.0‰~2.3‰，平均值-0.2‰，δ18O_PDB值范围-27.2‰~20.4‰，平均值-14.1‰，δ18O_SMOW值范围2.9‰~24.4‰，平均值16.4‰；方解石Sr同位素值变化范围0.707669~0.710115，平均值0.709320；硫化物δ34S_V-CDT值分布范围-20.2‰~1.3‰，平均值约-8.8‰，天青石δ34S_V-CDT值分布范围为17.1‰~19.4‰，平均值约18.0‰；Pb同位素测试结果中，206Pb/204Pb的变化范围为18.553~18.857，207Pb/204Pb变化范围为15.501~15.826，208Pb/204Pb变化范围为38.54~39.456；成矿阶段方解石Sm-Nd等时线年龄为29.5±1.7 Ma。对测试结果的研究表明，白秧坪矿集区东矿带碳质的来源较为均一，矿石中热液方解石碳质源自地层中碳酸盐岩溶解，成矿流体来自地层水和大气降水，属于盆地卤水流体系统；成矿物质硫来自海水硫酸盐的还原作用，成矿早期以有机质还原硫为主，成矿后期以生物还原硫为主；金属成矿物质来自沉积地层和盆地基底；测定白秧坪矿集区东矿带铅锌成矿年龄为29.5±1.7 Ma，与地质年龄限定的较为吻合。 

GEOCHEMICAL CHARACTERISTICS AND METALLOGENIC AGE OF THE EAST ORE BELT IN BAIYANGPING POLYMETALLIC ORE CONCENTRATION AREA

By studying the C, O and Sr isotopic characteristics of calcites in ore-forming stage, the S and Pb isotopic characteristics of sulfides, and the Sm-Nd dating of calcite in mineralization period, we discussed the ore genesis of the east belt in Baiyangping ore concentration area. Test results show that the δ13C_PDB values of calcite range from -4.0‰ to -2.3‰ with the average of -0.2‰, the δ18O_PDB values range from -27.2‰ to 20.4 ‰ with the average of -14.1‰, the δ18O_SMOW values range from 2.9‰ to 24.4‰ with the average of 16.4‰, and the Sr isotopic values of calcite are between 0.707669 and 0.710115 with the average of 0.709320. The δ34S_V-CDT values of sulfides distribute in the range of -20.2 ‰ to 1.3 ‰ with the average of about -8.8‰, and the δ34S_V-CDT values of celestine distribute in the range of 17.1‰ to 19.4‰ with the average of about 18.0‰. The Pb isotope test results yield 206Pb/204Pb values of 18.553~18.857, 207Pb/204Pb values of 15.501~15.826 and 208Pb/204Pb values of 38.54~39.456, and the Sm-Nd isochron age of calcite in mineralization stage is 29.5±1.7 Ma. The results indicate a homogeneous carbon source in the east ore belt, and the carbon in hydrothermal calcite is derived from the dissolution of carbonate rock strata. The ore-forming fluids are from formation water and precipitate water, which are belonged to the basin brine fluid system. The sulfur is from organic thermal chemical sulfate reduction in the early mineralization stage and biological sulfate reduction in the late mineralization stage. And the metal mineralization material is from sedimentary strata and basement. The dating results show that the Pb-Zn mineralization of the east ore belt occurred at 29.5±1.7 Ma ago, which is consistent with the constrainted geological age.