区域成矿流体的形成与演化

成矿流体是富含挥发份、碱金属的含矿卤水 ,其中碱金属来源于岩浆热液、变质热液、海水及通过水岩作用从岩石中萃取等 ;而挥发份来源于地幔、水岩作用与有机质分解作用。成矿流体中的硫也是多来源的 ,硫的活度与氧逸度有关 ,高温还原环境H2 S的活度降低 ;成矿流体的同位素分馏与水岩作用强度有关 ,控制同位素分馏的基本因素是温度及水岩比值。根据成矿流体的成分及物理化学性质 ,可以分类为高温硅钾卤水、中温碳酸盐卤水及低温硫酸盐型卤水。成矿流体没有固定的来源 ,在一定地质条件下 ,任何来源的热水流体都可以形成成矿流体。控制成矿流体形成的主要地质作用是岩浆作用、变质作用、地热增温作用及构造作用等。文中根据地质作用类型对区域地质流体进行划分 ,可分为岩浆作用区域成矿流体 (以高温硅钾卤水为主 ,可以有高温到中低温的流体分带 ) ,沉积作用区域成矿流体 (以中低温碳酸盐及硫酸盐型卤水为特征 ) ,大洋盆地区域成矿流体 (与岩浆岩区域成矿流体类似 ,有高温到低温的流体分带 )和变质作用区域成矿流体 (变质程度不同而有不同的流体类型混合 )。

THE FORMATION AND EVOLUTION OF REGIONAL ORE-FORMING FLUID

The ore-forming fluid is a kind of ore-bearing fluid full of alkaline metals that originate from magmatic and metamorphic hydrothermal fluid, seawater, water-rock action etc., and volatile gases that come from the mantle, the water-rock action and the decomposition of organic matter. The sulphur in ore-forming fluid is of multiple sources, and its activity is related to the oxygen fugacity. The activity of H_2S is down in the high temperature reduction environment. The isotopic distillation of ore-forming fluid is also associated with the intensity of water-rock action, and the basic factors controlling the isotopic distillation are the temperature and the ratio of water to rock action. The fluid, based on the composition of ore-forming fluid and its physical and chemical properties, can be divided into high temperature K-Si-bearing brine, moderate temperature carbonate brine and low temperature sulphate brine. There is not a fixed source for ore-forming fluid, but under a certain condition, any fluid can be converted into ore-forming fluid. The main geological functions are magmatism, metamorphism, geothermal gradient function and tectonism etc. Based on the types of geological functions, we divide the regional ore-forming fluid into: the magmatic rock area ore-forming fluid with predominant high temperature Si-K fluid and with fluid's zoning from high temperature to moderate or low temperature; the ore-forming fluid in sedimentary rock region with the characteristics of moderate/low temperature carbonate and sulphate brine; the ore-forming fluid in ocean basin area,which is similar to that of magmatic rock region,with fluid’s zoning depending on the temperature;and the ore-forming fluid in metamorphic rock area with mixed distribution of different type of fluids being greatly attributed to different extent of metamorphism.