大兴安岭中段有色金属矿床成矿物质来源探讨

大兴安岭中段是我国重要的铅锌银等有色金属成矿区,探讨其成矿物质来源对区内成矿预测及找矿工作具有重要意义。经广泛地质调查、典型矿床采样、岩矿鉴定、全岩地球化学分析,并在此基础上进行元素聚类分析,结果显示海西期成矿岩浆岩稀土总量偏低,负铕异常不明显,轻重稀土比值较大,与稀土总量呈正相关关系,与δEu值呈负相关关系,表明成岩物质以幔源为主。燕山期成矿岩浆岩则相反,显示壳源物质特征。铅锌银多金属矿以锌为主,铅锌矿石与幔源分异岩浆岩的稀土配分模式基本一致;聚类分析显示TFeO-Cu-Zn为独立群组,表明铁铜锌物质是从岩浆结晶晚期的岩浆中分异出来;TFeO-Cu-Zn独立群组显示区域内闪锌矿均为高温铁闪锌矿。研究认为,大兴安岭中段铅锌银矿成矿物质来自闪长岩,后期热液改造对铅银富集有一定作用,中基性岩浆岩形成铅锌银成矿系统,而酸性岩浆岩形成铜钼及铜锡成矿系统。

Ore-forming Material Source of Non-ferrous Metal Deposits in the Central Great Xing’an Range

The central Great Xing’an Range is an important non-ferrous metal province in NE China, such as lead, zinc and silver,and discussion on the ore-forming material source is important for metallogenic prediction and prospecting work in this region. Through extensive geological survey,typical deposits sampling,rock and mineral identification,the whole-rock geochemical compositions and element cluster analysis, the results show that the total REE content of the Hercynian magmatic rocks is low, and the negative Eu anomaly is indistinct, and the LREE/HREE ratio is large,which is positively correlated with the total amount of rare earth and negatively correlated with the δEu value, indicating that the diagenetic material is mainly derived from the mantle. Whereas the Yanshanian magmatic rocks show absolutely contrary characteristics,indicating the characteristic of crustal material. The lead-zinc-silver polymetallic deposit is dominated by zinc. The REE distribution pattern of the lead-zinc ores is basically consistent with that of the mantle-derived differentiated magmatic rocks. Cluster analysis shows that TFeO-Cu-Zn is an independent group, indicating that the TFeO-Cu-Zn material is separated from the magma from late magmatic crystallization. The TFeO-Cu-Zn independent group shows that the sphale-rite in the region is all high-temperature iron sphalerite. The results show that the ore-forming materials of lead-zinc-silver deposits in the region are diorite-derived. The later hydrothermal transformation has certain effects on the lead-silver enrichments. In terms of the ore-forming material source, an intermediate-mafic magmatic-related lead-zinc-silver metallogenic system and a felsic magmatic-related copper molybdenum and copper-tin metallogenic system is presented.