河南栾川地区铅锌矿床地质和硫同位素地球化学

河南栾川地区是我国著名斑岩钼矿集区,近年铅锌矿勘查取得重要进展,但对铅锌矿成因认识分歧颇多。研究表明,栾川地区铅锌矿产在燕山期斑岩钼矿床外围,矿区地层为中元古界官道口群和新元古界栾川群碳酸盐岩-碎屑岩沉积变质建造,地层中侵入有晋宁期辉长岩、正长岩和燕山期酸性斑岩,铅锌矿呈脉状或透镜状,发育3种类型:受燕山期斑岩与元古界钙质地层接触带控制的夕卡岩型铅锌矿、受北西西向层间断裂构造控制的脉状铅锌矿和受北东或近南北向张-张扭性断裂控制的脉状铅锌矿。铅锌矿石中硫化物δ~(34)S_(V-CDT)为近零的正值(骆驼山0.37‰～4.20‰、赤土店-0.32‰～8.30‰、百炉沟-1.20‰～10.90‰、冷水北沟0.70‰～12.10‰),岩浆来源硫特征明显;夕卡岩型铅锌硫化物的δ~(34)S_(V-CDT)与本地斑岩型钼矿石中硫化物的δ~(34)S_(V-CDT)(1.24‰～3.30‰)极为相近,脉状铅锌硫化物的δ~(34)S_(V-CDT)与斑岩型钼矿石中硫化物重合,但有地层中硫(δ~(34)S_(V-CDT)为12.43‰～18.63‰)的影响。总体上δ~(34)S_(黄铁矿)>δ~(34)S_(闪锌矿)>δ~(34)S_(方铅矿),指示矿石中主要硫化物矿物硫同位素分馏基本达到平衡,赤土店铅锌矿石中共生方铅矿与闪锌矿的硫同位素温度计指示硫化物矿物沉淀温度较高(388.29℃)。河南栾川地区铅锌矿主体应为受燕山期构造-岩浆作用控制的中高温热液铅锌矿床。

Geology and sulfur isotope geochemistry of lead-zinc deposits in Luanchuan district, Henan Province, China

The Luanchuan district in Henan Province is known as a porphyry molybdenum concentrated area in China. Recently, numerous lead-zinc lodes have been found there. However, there are many divergent opinions on the genesis and controlling-factors of these lead-zinc deposits. The lead-zinc deposits in Luanchuan district are distributed around the Yanshannian porphyry molybdenum intrusions and hosted in a metamorphic sedimentary formation consisting of terrigenous clastic rock and carbonatite of either meso-proterozoic age (the Guandaokou group) or neo-proterozoic age (the Luanchuan group), which is intruded by neo-proterozoic (Jinning stage) gabbro and syenite and Yanshannian acidic porphyries. The lead-zinc deposits are of vein or lenticular shape, and can be divided into three types: (1) the skarn type lead-zinc deposits controlled by the contact zone between Yanshannian porphyries and proterozoic calcareous strata;(2) the vein-type lead-zinc deposits controlled by the WNW interlayer fault;(3) the vein-type lead-zinc deposits controlled by the NE-NNE extensional torsional fault. The sulfur isotope compositions of sulfides suggest the following points of information: (1) the δ~(34)S_(V-CDT) of sulfides in lead-zinc ores are positive values that close to 0‰, which appear obviously to have had a source of magmatic sulfur (Luotuoshan deposit=0.37‰ - 4.20‰, Chitudian deposit=-0.32‰ - 8.30‰, Bailugou deposit=-1.20‰ - 10.90‰, Lengshuibeigou deposit=0.70‰ - 12.10‰);(2) the δ~(34)S_(V-CDT) of the sulfides of skarn lead-zinc ore are very close to that of the sulfides in porphyry molybdenum ore (1.24‰ - 3.30‰), and the δ~(34)S_(V-CDT) of the sulfides of vein-type lead-zinc ore overlap mostly with that of the sulfides in porphyry molybdenum ore but influenced by the sulfur in the wall-rock (δ~(34)S_(V-CDT)=12.43‰ - 18.63‰);(3) as a whole, δ~(34)S_(pyrite)>δ~(34)S_(sphlaerite)>δ~(34)S_(galena), which shows the sulfur isotope fractionations of the dominating sulfides in lead-zinc ore basically reach equilibria, and a pair of paragenetic sphalerite and galena from Chitudian deposit gives a high sulfur isotope equilibrium temperature of 388.29 ℃. All the above suggest that the lead-zinc deposits in Luanchuan district, Henan Province, are principally meso- to hypo-thermal lead-zinc deposits controlled by Yanshannian structural-magmatic activity.