豫西熊耳山地区上道回钼矿床地质及流体包裹体研究

Characteristics of Ore Geology and Fluid Inclusions of the Shangdaohui Mo Deposit in the Xiong'ershan Region,Western Henan

上道回钼矿床位于华北克拉通南缘豫西熊耳山-外方山地区,受控于马超营断裂的次级断裂,赋矿地层为中元古界熊耳群中酸性火山岩,矿体呈多组脉状产出.金属矿物以辉钼矿、黄铁矿为主,热液蚀变为硅化、钾长石化、碳酸盐化.热液成矿过程从早到晚为石英-黄铁矿阶段、石英-辉钼矿-多金属硫化物阶段、石英-方解石阶段.包裹体类型为C型（CO2型）、W 型（NaCl-H2O型）、S型（子晶型）.早阶段发育W 型、C型和少量S型包裹体,中阶段发育C型、W 型、S型包裹体,晚阶段发育W 型包裹体.包裹体均一温度为210～390℃、180～300℃、120～220℃,盐度由早阶段1.0% ～13.4%和27.2% ～33.2%,经中阶段0.3% ～14.1%和27.3% ～28.5%,到晚阶段0.1%～14.2%.成矿流体由富CO2向贫CO2演化,流体沸腾使CO2等挥发分逃逸,造成流体pH值升高、氧化性降低,从而导致辉钼矿等硫化物沉淀.早、中阶段C型包裹体的捕获压力为148～371MPa、108～383MPa,对应的成矿深度为5～14km.

The Shangdaohui Mo deposit is located in the Xiong’ershan-Waifangshan region which is in the southern margin of the North China Craton.The orebodies,controlled by the secondary fault of the Machaoying fault,occur as veins and are hosted by the Mesoproterozoic intermediate to felsic volcanic rocks of the Xiong’er Group.The major metallic minerals are molybdenite and pyrite.The silicification,K-felsparization and carbona-tization are the main hydrothermal alteration types.The hydrothermal ore-forming process can be divided into three stages,quartz +pyrite stage (early stage),quartz +molybdenite +polymetallic sulfide stage (middle stage)and quartz +calcite stage (late stage).Three types of fluid inclusions can be identified in the Shangdao-hui Mo deposit,including aqueous (W-type),CO2-rich (C-type),daughter mineral-bearing (S-type)fluid in-clusions.The early stage quartz contains mostly W-type,C-type and minor S-type fluid inclusions,the middle stage quartz contains C-type,W-type and S-type fluid inclusions,and the late stage calcite only contains the W-type fluid inclusions.The homogenization temperatures of early-stage fluid inclusions range from 21 0 ℃ to 390 ℃,with salinity of 1 .0% -1 3.4% and 27.2% -33.2%.The middle-stage homogenization temperature is 1 80 ℃ to 300 ℃,with salinity of 0.3% -1 4.1 % and 27.3% -28.5%,and the last-stage homogenization temperature ranges from 1 20 ℃ to 220 ℃,with salinity 0.1 % -1 4.2%.The ore-forming fluid evolved from carbonic to aqueous from early to late mineralization stage.Fluid boiling occurred in both early and middle sta-ges,and resulted in release of CO2 ,which caused the precipitation of the MoS2 and other sulfides.Trapping pressures estimated according to the C-type fluid inclusions are 1 48 -371 MPa and 1 08 -383 MPa in the early and middle stages,corresponding to metallogenic depth of 5 -1 4 km.