河南磨沟金矿床成因：地质、流体包裹体和H-O-S稳定同位素约束

Genesis of the Mogou Au deposit,Henan Province,China:Constraints from geology,fluid inclusions and H-O-S isotopes

豫西熊耳山地区的磨沟金矿床赋存于熊耳群火山岩中,矿体受NE向断裂控制。通过对矿区的地质特征、流体包裹体以及H-O-S稳定同位素研究,探讨磨沟金矿床的成矿物质、流体来源及成因机制。成矿期可划分为石英-黄铁矿、石英-多金属硫化物以及石英-碳酸盐3个阶段。流体包裹体有纯CO_2型、CO_2-H_2O型和H_2O-NaCl型3种。成矿流体具有中温(210℃~310℃)、低盐度(NaCl质量分数为3%~12%)的特征,成矿深度小于9km。氢、氧同位素分别为-107‰^-88‰和-1.7‰~4.3‰,硫同位素为-0.98‰~5.62‰。磨沟金矿床成矿流体主要为变质流体来源,晚阶段有大气降水参与;成矿物质主要来自变质结晶基底;属于造山型金矿床。

The ore bodies of Mogou Au deposit in the Xiong＇er Mountains, western Henan Province, are controlled by the NE faults and hosted in volcanic rocks of the Xiong＇er Group. On the basis of the geological characteristics, fluid inclusions and H-O-S stable isotope data, the metal and fluid sources, and ore forming genesis of the Mogou Au deposit are studied. The hydrothermal activities of mineralization can be divided into three stages： quartz pyrite stage, quartz polymetallic sulfide stage and quartz carbonate vein stage. There are three types of fluid inclusions in the auriferous quartz veins, including the pure carbonic type, CO2 -H2O type and H2O NaCl type inclusions. Homogenization temperature values obtained from the inclusions range from 210℃ to 310℃, corresponding to salinity values of fluid inclusions of 3% -12%, and the ore forming depth is less than 9 km. The δD V-SMOW values range from- 107‰ to 88‰, corresponding to δO 11 2 O ovalues of 1.7‰-4. 3‰, and δ34 S CDT values range from -0. 98‰ to 5. 62‰ H- O isotope results indicate that the ore forming fluids are derived from metamorphic fluid, with minor meteoric water during the late stage, and S isotope data show that the ore forming material is originated from metamorphic crystalline basement. Geological and fluid features and stable isotope results suggest that the Mogou Au deposit is an orogenic type gold deposit.