西藏班公湖-怒江成矿带及邻区铋矿化带的发现与意义

The Discovery of the Bismuth Mineralization Belt in the Bangong Co-Nujiang Metallogenic Belt of Tibet and its Adjacent Areas and Its Geological Significance

铋是一种稀有金属,在世界分布很不均匀,全世界铋资源绝大部分赋存在中国,我国的铋资源主要集中在湖南的柿竹园。本文通过系统的野外调查与样品采集、室内ICP-MS与扫描电镜及电镜能谱方法分析,确定班公湖-怒江成矿带12个矿床(点)单件样品铋含量达到边界品位的要求,9个矿床(点)单件样品达到工业品位的要求,最高达到9575×10?6。铋含量高的地质体东西向呈带状展布,为一铋的成矿带。确定材玛矽卡岩型铁矿、尕尔穷矽卡岩型铜矿、舍索矽卡岩型铜铅锌多金属矿-社样多金属矿-更乃矽卡岩型铜铁矿、拉屋矽卡岩型铜矿-尤卡浪脉状铅矿共4个铋矿找矿远景区。铋矿物种类为硫铜铋矿、自然铋、硫铋铜铅矿、硫铋银矿共4种。铋含量较高的样品主要分布于矽卡岩型矿床中,斑岩型矿床的铋含量较低。班公湖-怒江成矿带铋的矿化时代应为燕山期,为班公湖-怒江向南(即冈底斯地块)俯冲使之闭合后碰撞阶段所形成的。拉屋多金属矿床正在开采,其矿石含有较高的铋含量,由于铋的单位价值远远大于正在开采的铜与铅锌等资源,因此,该矿床开采时需加强铋资源的评价,以提高其资源的综合利用价值。

Bismuth is one of the rare metals,and its distribution is very uneven in the world,with the vast majority of the bismuth resources distributed in China.China＇s bismuth resources are mainly concentrated in Shizhuyuan,Hunan Province.Through systematic field survey,sample collection,indoor ICP-MS analysis and SEM energy spectrum analysis,the authors have reached the conclusion that along the Bangong Co-Nujiang metallogenic belt bismuth content of single samples in 12 ore deposits or ore spots can meet the requirement of the cut-off grade,and that in 9 ore deposits or ore spots can meet the requirement of the industrial grade.The geological body with high content of bismuth（up to 9575×10-6） is in zonal distribution.Four bismuth prospective areas were delineated,namely the Caima skarn iron ore deposit,the Gaerqiong skarn copper ore deposit,the Shesuo skarn copper-lezd-zinc polymetallic ore deposit-Shexiang polymetallic ore deposit-Genai skarn type copper iron ore deposit,and the Lawu skarn type copper ore deposit-Youkalang vein type lead ore deposit.There are four species of bis-muth minerals,i.e.,sulfur-bismuth-copper ore,natural bismuth,copper-bismuth-lead-sulfur ore,and sulfur-bismuth-silver ore.Bismuth samples of high grade is mainly seen in skarn deposits,whereas porphyry type deposits have relatively poor bismuth.The mineralization of bismuth in the Bangong Co-Nujiang metallogenic belt should have occurred at the collision stage after the southward subduction and closure of the Yanshanian Bangong Co-Nujiang.The Lawu polymetallic deposit which has a relatively high bismuth content is now being mined.Because the unit value of Bi is by far higher than that of copper,lead,zinc and some other resources,the evaluation of bismuth resources should be further emphasized in the exploration of the ore deposit so as to improve the comprehensive utilization of resources.