河南银洞沟造山型银矿床碳硫铅同位素地球化学

河南内乡县银洞沟大型脉状银多金属矿床产于北秦岭造山带朱夏断裂北侧的二郎坪地体内,含矿围岩是二郎坪群火山岩-碎屑岩建造,矿体定位于断裂构造带内,产状受断裂构造控制,矿石组构、矿物组合、围岩蚀变类型和分带等地质特征均与典型造山型金矿一致,应属造山型银矿.矿床硫化物δ~(34)S介于+4.7～+8.1‰,高于有机物和岩浆岩.流体包裹体中CO_2的δ~(13)C介于-0.2～+0.9‰,与海相碳酸盐一致,高于其它所有地质体.矿石硫化(206)Pb/~(204)Pb=18.2026～18.4462,~(207)Pb/~(204)Pb=15.5835～15.7739,~(208)Pb/~(204)Pb=38.5478～39.0890,显示铀铅富集,钍铅微弱亏损.这些同位素地球化学特征均指示夹杂沉积硫酸盐的碳酸盐-碎屑岩沉积建造是最为理想的物源,对比研究东秦岭北坡相关地质单元,认为成矿物质和流体主要来自二郎坪群和秦岭群,尤其是雁岭沟组含碳酸盐岩地层对于成矿流体和物质的贡献不可替代.中生代华北与华南板块碰撞造山过程中,秦岭群沿朱夏断裂向北陆内俯冲到二郎坪地体之下,并通过俯冲变质脱水而为银洞沟矿床的形成提供了大量成矿物质和流体.朱夏断裂北侧依次出现银洞沟银矿、许瑶沟金矿、松垛隐伏花岗岩基、栾川斑岩钼矿带,构造-成岩-成矿空间格局与CMF模式(碰撞造山成岩成矿和流体作用模式)完全一致,证明了CMF模式的科学性和普适性和同位素示踪成矿物质和流体来源的有效性.银洞沟矿床的发现和研究结果证实了前人预测的朱夏断裂北侧"桑坪-米坪-许瑶沟铜金铅锌银等多金属矿化带"的客观存在,该带应作为银金多金属矿床勘查的重点区带.

C-S-Pb isotope geochemistry of the Yindonggou orogenictype silver deposit in Henan province

The Yindonggou silver(poly-metals)deposit,a large fault-controlled lode deposit in Neixiang County,Henan province,occurs in the Erlangping Terrane,northern East Qinling Orogen.The host-rocks are the lava-clastic assemblage of Erlangping Group.The occurrences of ore bodies were controlled by the subsidiary fault of Zhu-Xia fault and located in the faulted structure belt.All of the characteristics of the ore texture,mineral assemblage,the type and zonation of wall-rock alternation are similar to those of the orogenictype gold deposits as summarized by previous studies,which suggests it to be a typical orogenic-type silver deposit.The δ~(34)S values of the ore minerals are,+4.7～+8.1‰,higher than those of organic matter and magmatic rock.The δ~(13) C_(CO2) values of its ore-fluids vary from-0.2 to+0.9‰,which is consistent with marine carbonate and higher than all of other geologic bodies.The ore minerals have a uniform lead isotope compositions,with ~(206)Pb/~(204) Pb = 18.2026～18.4462,~(207)pb/~(204) Pb = 15.5835～15.7739,and ~(208)Pb/~(204)Pb = 38.5478～39.0890,indicating the richness in U-radioactive Pb and little lack of Th-radioactive Pb.The C-S-Pb isotope geochemistry suggests that the sedimentary formation of carbonate-clastic rock with sedimentary sulfate interbed was the most ideal source that provided the ore-forming fluid and materials to the Yindonggou deposit.This paper deduced that the metallogenic materials and fluids were mainly sourced from the Erlangping and Qinling groups,especially the Yanlinggou Formation of Qinling Group that consists of carbonate strata.During the collisional orogenesis process of the North and South China Cratons in Mesozoic,the Qinling Group northward underthrusted and located beneath the Erlangping terrane along the Zhu-Xia fault,and provided lots of oreforming materials and fluid to the Yindonggou deposit via metamorphic dehydration.In the north of Zhu-Xia fault,there were the Yindonggou Ag deposit,Xuyaogou Au deposit,Songduo buried granite pluton,Luanchuan porphyry Mo ore belt in turn,and such zonation is totally consistent with the Tectonic Model of Collisional Orogeny,Metallogeny and Fluid Flow(CMF model),which proves not only the CMF model is scientific and applicative but also the isotope geochemistry is effective to trace the source of metallogenic material and fluid.Additionally the discovery and study result of the Yindonggou Ag deposit approve the forecast is right that there was the Sangping-Miping-Xuyaogou Cu-Au-Pb-Zn-Ag ore belt in the north of Zhu-Xia fault,thus this belt should be a key area in silver poly-metals exploration.