韧-脆性剪切带构造控矿演化模式--以青海省乌兰县托莫尔日特金矿区为例

通过对青海省乌兰县托莫尔日特金矿区韧－脆性剪切带变形特征、成矿物质与热液来源及运移条件分析，提出了该区构造控矿演化的四阶段模式。该模式认为，早期的韧性剪切变形导致了成矿物质的由深部向浅部、由韧性剪切带外部向韧性剪切带内部的活化迁移，成矿热液在韧性剪切带上部（即韧脆性转换带附近）得以大量聚集。韧性变形后期温压条件降低，韧性变形转化为脆性变形，地表大气降水沿贯通性较强的脆性破裂带大量下渗，到达韧－脆性转换带附近，与该处积聚的成矿热液充分混合，热液性质发生改变，在相对张性或较薄弱的构造有利部位大量沉淀。由于断裂带的周期性活动，成矿物质得到多次沉淀而不断富集，最终形成金矿体。矿体形成后的构造隆升及剥蚀作用，使韧－脆性剪切带出露地表，金矿床也随之出露到近地表处。因此在矿区石英脉型金矿体的下部，可能会存在糜棱岩型金矿体，但品位可能会有所下降。

ORE-CONTROLLING MODEL OF DUCTILE-BRITTLE SHEAR ZONES --EXAMPLES FROM THE GOLD DEPOSITS IN TOMORITE REGION ,WULAN COUNTY ,QINGHAI PROVINCE

Based on the thorough analysis of the ore controlling structures, source of ore forming material and transportation characteristics in Tomorite gold deposit region, the paper proposed a four stage ore controlling model of ductile brittle shear zones in the area.The early ductile shearing led to the activation of ore forming fluid and pre accumulation of ore forming materials. In the late stage of ductile shear deformation, the temperature and pressure became low, which led to ductile brittle transition in fault zones. Because of the formation of brittle faults,meteoric water permeated downward along the brittle faults. When the water reached the ductile brittle transition zone, it mixed with the accumulated fluids in the ductile shear zones. Because of the mixture of different fluids, the character of the ore forming fluids had been greatly changed,resulting crystallization and precipitation of the ore forming fluids. In the cyclic activity of fault zones, crystallization and precipitation of the ore forming fluids could last for a very long time and repeated for many times, which led to the accumulation of ore forming materials and formation of ore bodies in structural advantageous regions.Subsequent uplift and erosion brought the ore bodies to shallow part of the ground. It is possible that some mylonite hosted ore bodies would exit beneath the quartz vein ore bodies, but the grade of ores would be a little lower.