新疆萨尔托海石英菱镁岩中发育的韧性剪切带及其对金矿的控制  

Identification of a ductile shear zone in quartz-magnesitite and its controlling on gold deposits in the Sartohay region,western Junggar,Xinjiang

作　　者：邱添[1] 朱永峰[1] 

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871

出　　处：《岩石学报》2012年第7期2250-2256,共7页Acta Petrologica Sinica

基　　金：国家国际科技合作项目(2010DFB23390)资助

摘　　要：萨尔托海金矿产在达拉布特蛇绿混杂岩带中。本文首次在该金矿区厘定出韧性剪切带,糜棱岩或者糜棱岩化石英菱镁岩中构成糜棱面理的矿物(铬云母、石英)形成于韧性剪切变形过程中,而切割糜棱面理的方解石-石英-黄铜矿-白云母脉代表脆性变形阶段的流体活动。根据矿物组合相互切割关系,识别出三期构造变形:早期NE向韧性变形(形成铬云母-石英组合)之后,发生了应力方向显著不同的破裂,形成NNW向分布的方解石-石英-黄铜矿-白云母脉;再晚期,应力方向又恢复到NE向,发育了浅层次的脆性构造破坏,形成了白云母-石英细脉。韧性剪切变形向脆性变形转换期间形成了石英-碳酸盐脉,其中往往含硫化物和自然金,此阶段是萨尔托海金矿的主要成矿时期。韧性剪切带控制着萨尔托海地区的金矿分布,成矿作用主要受沿剪切带迁移流体的控制,穿切糜棱面理的方解石-石英-黄铜矿-白云母脉是主要的找矿标志。韧性剪切带对金矿的显著控制表明,韧脆性转换期间形成的含硫化物石英碳酸盐脉以及相伴生的热液蚀变使金富集成矿,矿体一般赋存在断裂构造复杂的膨胀部位。萨尔托海金矿的成因与蛇绿岩的形成和演化没有关系。对韧性剪切带的系统研究是在该地区取得找矿勘探突破的关键。The Sartohay gold deposit is located in the Darbut ophiolitic m61ange, western Junngar, Xinjiang. It is the first time to recognize the ductile shear zone in this ore district. Fuchsite and quartz, representing the foliation of mylonite or mylonitized quartz- magnesitite, formed during ductile shearing deformation process. The calcite-quartz-chalcopyrite-muscovite vein, cutting off the mylonite foliation, represents the fluid activity during brittle deformation. On the basis of the correlation of mineral assemblages, three structural deformation stages could be recognized： early ductile deformation forming fuchsite-quartz assemblage, stress fracture in an obviously different direction filled with calcite-quartz-chalcopyrite-muscovite vein, and brittle structural deformation at shallow level in the direction similar to the direction of the early ductile deformation formed muscovite-quartz veinlets （ or micro-veins ）. Quartz- carbonate vein containing sulfide and native gold frequently was formed during the period of transformation from a ductile to brittle deformation regime, which represents the main ore-forming period. The distribution of gold deposits in the Sartohay district is controlled by shear zone. The calcite-quartz-chalcopyrite-muscovite vein cross-cutting mylonite foliation is a major ore prospecting indicator. The ductile shear zone controlling gold deposit indicates that, sulfide-quartz-carbonate vein formed during ductile-brittle transformation and associated hydrothermal alteration, induced gold enrichment and ore formation. Ore bodies always occur in the expansion part of fracture structure. The genesis of the Sartohay gold deposit has no relation with the Darbut ophiolite and its evolution. A systematic study on ductile shear zone in this area is the critical factor to make a breakthrough in further exploration.

关 键 词：韧性剪切带 石英菱镁岩 蛇绿混杂岩 达拉布特断裂 萨尔托海 新疆 

分 类 号：P542.3[天文地球—构造地质学] P618.51[天文地球—地质学]