河南省西峡县水地沟金矿地质特征及S、Pb同位素示踪

Geological Features and S and Pb Tracer Isotopes of the Shuidigou Gold Deposit in Xixia County,Henan Province

水地沟金矿是河南省北秦岭高庄-二郎坪金多金属矿成矿带内新发现的金矿,为探讨其成矿物质来源及成矿物质释放机制,对水地沟金矿矿石进行了S、Pb同位素分析。4件黄铁矿样品的δ^(34)S值介于0. 5‰～4. 5‰,平均值为2. 5‰,具有塔式分布特征,峰值在2‰～4‰之间,显示幔源硫特征。7件样品的^(206)Pb/^(204)Pb、^(207)Pb/^(204)Pb和^(208)Pb/^(204)Pb的比值范围分别为15. 80～18. 32、15. 11～15. 68和35. 17～38. 39,它们的μ值、△α值、Δβ值和Δγ值的范围依次为8. 97～9. 85、32. 93～74. 31、-1. 98～30. 64和4. 10～50. 61。在^(206)Pb/^(204)Pb-^(207)Pb/^(204)Pb比值图解中,水地沟金矿样品点位于下地壳铅演化趋势线和上地壳铅演化趋势线之间,在^(206)Pb/^(204)Pb-^(208)Pb/^(204)Pb比值图解中,它们集中于上地幔和造山带铅演化趋势线两侧,铅同位素Δβ-Δγ图解表明它们位于地幔Pb、上地壳Pb和上地壳与地幔混合的俯冲带Pb三个源区内。S、Pb同位素特征表明水地沟金矿成矿物质来源于上地幔-下地壳,成矿过程中有上地壳物质加入。水地沟金矿床的形成与北秦岭燕山期陆内(板内)造山过程密切相关,它是区域岩石圈拆沉作用的产物。在这一区域岩石圈灾变过程中,不仅使水地沟岩石圈-软流圈系统内不同源区的流体混合,造成了"宽泛"的S、Pb同位素示踪结果,而且有利于深部流体的大规模快速释放,说明水地沟金矿及其邻区具有大的成矿潜力。

The newly-discoved Shuidigou gold deposit is located in the Gaozhuang-Erlangping Au polymetallic mineralization belt,northern Qingling Mountains,Henan Province. S and Pb isotopes of ores from this deposit were analyzed to reveal the source of ore metals and deep process of deep ore fluids discharge for this deposit. Results show that the δ34SV-CTDvalues of four pyrite samples range from 0. 5‰ to 4. 5‰ with an average value of 2. 5‰. They are distributed in a tower shape in the δ34S histogram with peaks 2‰ to 4‰,implying a mantle source. The ranges of 206Pb/204Pb,20 7 Pb/204Pb and208Pb/204Pb of seven samples are 15. 80 ~ 18. 32,15. 11 ~ 15. 68 and 35. 17 ~ 38. 39,respectively. The values ranges of μ,△α,Δβ and Δγ of them are8. 97 ~ 9. 85,32. 93 ~ 74. 31,-1. 98 ~ 30. 64 and 4. 10 ~ 50. 61,respectively. Sample points are located between lower crust and upper crust lines in the206Pb/204Pb-207Pb/204Pb diagram and close to upper mantle line and orogenic line in the206Pb/204Pb-208Pb/204Pb diagram,respectively. In the Δβ-Δγ of Pb isotope diagram,seven sample points of the Shuidigou Au deposit fall into a mantle source,upper crust source and mixed source of upper crust and mantle,respectively. These S and Pb isotopic features suggest that the metalogenic material is derived from lower crust and upper mantle,and the upper crust material has been added in the deposit formation process. The Shuidigou Au deposit is related to Yanshanian intracontinental( intraplate)orogenesis of northern Qinling Mountains,and it is one of products of regional lithosphere delamination. This lithosphere-asthenosphere dynamic process has affected upper mantle and lower crust of the Shuidigou area. It made deep fluids of different sources in the lithosphere-asthenosphere system mixed,resulting in widespread S and Pb isotopes,favorable for rapid discharge of fluids at depth,suggesting that the Shuidigou area possesses endogenetic metalogenic potential.