DUCTILE-BRITTLE SHEAR ZONES AND THEIR CONTROL TO GOLD MINERALIZATION IN TOMORITE GOLD DEPOSIT REGION, QINGHAI PROVINCE
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摘要: 矿区位于近NW-NWW向展布的断裂带内,并严格受其控制.控矿断裂带为一条韧-脆性剪切带,其形成主要经历了早期韧性变形、晚期脆性变形及后期改造破坏3个阶段,叠加于早期韧性剪切带之上的晚期脆性破裂带,是矿脉的主要产出位置,成矿与断裂带的韧-脆性转换密切相关.矿体形成于韧-脆性剪切带的转换带附近,后期由于抬升剥蚀而出露地表.矿体分布可能具有"两层楼"式的垂直分带,上部为石英脉型金矿体,品位较高,但规模不大;下部为糜棱岩型金矿体,规模较大,但品位稍低.因此本区以后的找矿工作中应注意挖掘深部糜棱岩型金矿的潜力.Abstract: The ore deposits in Tomorite gold deposit region in Qinghai Province are located in NW-NWW trend fault zones, which are the major ore-controlling structrues in the area. Through thorough analysis of the ore-controlling structures in the area, we found that formation of the fault zones can be divided into three stages, which are ductile shear deformation stage, brittle deformation stage and late reform-destruction stage. The brittle faults superimposed upon the early ductile shear zones are favorable regions for mineralization, and the formation of the ore deposits is related to the ductile-brittle transition of fault zones in the area.Study on ore-controlling structures shows that the ore veins are located near ductile-brittle transition in fault zones. Uplift and denudation after the formation of the ore bodies lead to their exposure near the ground. It is possible that some mylonite-type ore bodies would exit beneath the quartz vein ore bodies, but the tenor of ores would be a little lower. More attentions should be paid to the deep mylonite-type ore bodies in the future work.
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