班公湖—怒江成矿带商旭造山型金矿床Ⅲ号矿段深部找矿潜力研究

Prospecting Potential Analysis of Deep No.Ⅲ Ore Section in the Shangxu Orogenic Gold Deposit,Bangong Co—Nujiang Metallogenic Belt,Tibet

西藏双湖县商旭造山型金矿床位于班公湖—怒江缝合带中段,矿体受NWW向的脆—韧性断裂构造控制,呈似层状、脉状产于中—下侏罗统木嘎岗日群混杂岩中。围岩为炭质板岩、变石英砂岩等。矿石类型主要为石英脉型和构造蚀变岩型,矿石构造以细脉状和角砾状为主,矿石矿物为自然金。矿床学与同位素地球化学研究认为木嘎岗日群含金建造为商旭金矿提供了主要物质来源,NWW向脆—韧性断裂构造为含金热液的运移和金的沉淀供了运输通道和就位空间,羌塘南缘早白垩世构造—岩浆活动为含金热液的运移提供了热动力,矿区内NWW向构造破碎带中变形强烈,具黄铁矿化、硅化蚀变的地段,为本矿区的找矿有利地区。土壤地球化学调查显示,Ⅲ号矿段南部,T-4、T-5异常区域具有较好的找矿潜力;电法测深资料显示,Ⅲ号矿段的控矿构造在深部还有延伸,并可能与区域较深大的断裂相连。综合分析认为,Ⅲ_(1-2)号矿体在标高4200m以下还具有较大的找矿潜力,通过进一步地质勘查工作,有望提高金资源量,扩大矿床规模。同时,初步总结了商旭造山型金矿床"找矿三步组合拳"的勘查工作方法。

Shangxu orogenic-type gold deposit is located in the center of the Bangonghu-Nujiang suture zone, Shuanghu county of Tibet. The orebodies, controlled by the NWW-trending brittle-ductilefractures, occur as layer or veins in the mictite of the Middle-Lower Jurassic Mugagangri Group. The wall rocks are dominated by carbonaceous slate and metasandstone. The ores are mainly quartz vein type and tectonic alteration type. The ore structures are mainly veinlet and brecciated. The ore mineral is mainly native gold. Ore deposit and isotopic geochemical analysis show that ore forming materials were mainly derived from the Mugagangri gold bearing formation. The NWW trending brittle ductile structures provide transport corridor and space for ore deposition. Early Cretaceous tectonic magma in the southern margin of Qiangtang provided driving force for the transport of Au-bearing hydrothermal fluids. The strongly deformed areas in the NWW-trending fault, where is accompanied by pyritization and silication, are preferable for ore prospecting. Pedogeochemistry survey shows that the T-4 and T-5 abnormal areas in the south of the No. Ⅲ ore section are of further prospecting potential. Additionally, the electrical sounding data indicate that the ore controlling structures extend to the deep of the No. Ⅲ ore section and probably connects with deep faulting. In summary, we suggest that it is of great ore prospecting potential under the 4200 m elevation of the No.Ⅲ1-2 ore section. Further investigation work is needed to upgrade gold resources amount and enlarge the size of the deposit. At last, an exploration method “Three-step Method” is preliminarily summarized for the Shangxu orogenic gold deposit.