三江中北段夏塞Ag-Pb-Zn矿床红锑镍矿的发现及地质意义

Identification and Geological Significance of Breithauptite in the Xiasai Ag-Pb-Zn Deposit,Central-northern Sanjiang Metallogenetic Belt

夏塞Ag-Pb-Zn矿床为三江中北段义敦地区一个典型的大型岩浆热液脉型矿床,本次研究首次发现了镍矿物。银铅锌矿床中发育镍矿物的报道甚少,且含镍流体来源也存在争论。本文通过对镍矿物进行电子探针成分测试及元素面扫描分析,探讨了Ni元素的赋存状态及其地质意义。研究表明,这些矿物主要由Ni和Sb组成,少量矿物含较低含量的Fe和S。矿物名称为红锑镍矿(NiSb),主要以矿物包裹体形式赋存于磁黄铁矿或以微细矿物与磁黄铁矿伴生。结合前期矿床学研究成果,表明夏塞Ag-Pb-Zn矿床成矿作用与早白垩世晚期壳幔混合成因的二长花岗岩关系密切。

The large-scale Xiasai Ag-Pb-Zn deposit is located in the central Yidun Terrane,Sanjiang metallogenetic belt,and is a typical magmatic-hydrothermal vein deposit.This paper reports our first identification of nickel minerals in this deposit.Nickel minerals are rarely reported in Ag-Pb-Zn deposits,and the source of nickel-bearing ore-forming fluids is actively debated.In this contribution,we studied the occurrence of nickel element and the geological significance of nickel minerals through Electron Probe Microscopy(EPM)analysis and mapping.Breithauptite(NiSb)is the major Ni-bearing mineral which is enriched in Ni and Sb,with minor Fe and S.Breithauptite grains either occur as inclusions in pyrrhotite or as irregular intergrowth with pyrrhotite.The appearance of breithauptite in the Xiasai deposit indicates that the Ag-Pb-Zn mineralization has a close genetic relationship with the Xiasai monzogranite which formed by mixing of crust-and mantle-derived magmas during the late stage of the Early Cretaceous.