西藏冈底斯银多金属矿化带的基本特征与成矿远景分析

Characteristics and ore potentiality of Gangdese silver-polymetallic mineralization belt in Tibet

在冈底斯斑岩铜矿带的北侧,发育一条与之平行的银多金属矿化带。文章对该银多金属矿化带的成矿构造背景、矿床类型及矿化特点进行了初步分析与总结。研究结果表明,该矿化带受旁多—措勤逆冲系的控制,呈近EW向带状展布,带内矿床多位于EW向逆冲断裂与近NS向张性构造的交汇部位;主要矿化类型为矽卡岩型和热液脉型;据矿化特点差异,以念青唐古拉为界,可分为东、西2段,东段以矽卡岩型Cu-Pb-Zn-Ag矿化为主,西段以热液脉型Ag-Pb-Zn矿化为主,西段矿床的银含量明显高于东段。该矿化带是大陆碰撞造山晚期或后碰撞伸展早期(25～15Ma)热液活动的产物。综合对比分析显示,该矿化带具有良好的成矿条件及巨大的成矿潜力,有望发展成为一条规模巨大的银多金属成矿带。

A new silver-polymetallic mineralization belt in parallel with the Gangdese porphyry copper belt was discovered on the northern side of the Gangdese Range. This WE-trending silver-polymetallic mineralization belt is controlled by the Pangduo-Cuoqin thrust system. Most of the deposits in the belt occur at the junctions between the WE-striking thrust faults and the NS-striking tension faults. Two types of mineralization can be recognized in the belt. In the western part, i.e. to the west of Yangbajing rift, the deposits are dominated by hydrothermal veinlike silver-lead-zinc mineralization; in the eastern part, however, the deposits are characterized by skarn type copper-lead-zinc-silver mineralization. The silver content of ores in the western belt is obviously higher than that in the eastern belt. The silver-polymetallic deposits resulted from the hydrothermal process in the late period of the continent collisional orogenic activity or in the early stage of collision-extension （25-15 Ma）. An integrated analysis shows that the belt has favorable conditions for silver-polymetallic mineralization and possesses remarkable mineralization potentiality. The belt is therefore expected to develop into a large-size silver-polymetallic belt in Tibet.