河南嵩县钾长石石英脉型钼矿矿床成因分析

Genesis of K-Feldspar-Quartz Vein Type Molybdenum Deposit in Songxian County,Henan

河南嵩县钾长石石英脉型钼矿顺层产出于中元古界熊耳群火山岩中，呈似层状、透镜状密集平行排列，与围岩整合产出。矿化石英脉两侧呈条带状蚀变，钼矿化均伴随着钾长石化、强硅化和黄铁矿化，远离石英脉则蚀变减弱，矿化也随之减弱。石英脉可以划分三期，早期无矿石英脉；中期石英脉含有辉钼矿-黄铁矿-黄铜矿-方铅矿-闪锌矿，构成石英脉型矿石。晚期属于石英-碳酸盐细脉，无矿化。文章对三期石英脉分别进行了地球化学分析，石英脉矿石和非矿石英脉稀土含量配分曲线及微量元素的差异反映成矿流体喷流结晶过程中发生了流体分异。成矿流体包裹体反映系高盐度富CO2的沸腾和不混溶流体成矿，成矿压力28×10^5-68×10^5Pa，属于低压浅成环境。测定了矿化石英脉的Ar／K年龄1352．95±27．06Ma。根据上述分析，认为嵩县钾长石石英脉型钼矿属于火山期后中高温热液矿床，成矿物质来自火山岩浆热液，在火山口及火山机构附近沿火山岩层间裂隙充填交代成矿。

The K - feldspar - quartz vein type molybdenum deposits in Songxian county of Henan province occurred along the volcanic rock strata of the Xiong＇ er Group of Middle Proterozoic. They appear stratiform - like, lenticular, parallel and dense, and have a conformable contact with wall rocks. Banded alteration halos developed at both sides of these mineralized quartz veins. Molybdenum mineralization usually occurs with k - silicate （ k - feldspar） alteration, strong silicification and pyritization. Alteration and mineralization become weaker with the distance farther from quartz veins. Quartz veins are formed in three stages. The quartz veins formed in early stage were not mineralized. The quartz veins formed in middle stage produce quartz vein - type ores containing molybdenite, pyrite, ehalcopyrite, galena and sphalerite. The ones of late stage are small quartz - carbonate veins without mineralization. The geochemical characteristics of quartz veins of three stages are analyzed respectively. The rare earth elements distribution pattern and trace element contents of ore - beating quartz veins and barren quartz veins are different. It shows that the fluid differentiated during mobilization and evolution process. Fluid inclusions in ore - bearing quartz veins show high salinity and rich in CO2 that might indicate the boiling and immiscibility of ore - forming fluids, at pressure varying between 28 × 10^5 - 68 × 10^5 Pa. The Ar/K age of mineralized quartz veins is about 1352.95±27.06Ma. It is concluded that the molybdenum mineralization in Songxian is mesothermal to hypothermal deposits related with volcanic - magmatic fluids, which fill the fissures among the strata near the crater and volcanic edifice, and alteration halos developed by metasomatism between fluid and host rocks.