北衙金矿外带似层状Pb-Zn-Ag多金属矿床地质特征及成因

北衙金多金属矿床地处金沙江-红河富碱斑岩带南段，是该带上成矿作用与富碱斑岩有关矿床的代表。通过对北衙金矿外围似层状Pb-Zn-Ag矿床地质特征及地球化学特征进行研究，得出了以下结论：①赋矿围岩为三叠系中统北衙组灰岩，相对富集Pb、Zn、Au、Ag等成矿元素，是铅锌银矿的有利矿源层；②成矿流体为NaCl-H₂O-CO₂体系，具有中-低温、中-低盐度的特征，来源于富碱斑岩体结晶分异的岩浆热液；③矿石S同位素含量-2.4‰～+2.8‰，指示矿床硫与斑岩体有相同的来源，均来自深部地幔，后期有部分地层硫的加入，矿石Pb同位素分析结果指示成矿物质来源于壳幔混合；④特定的北衙组碳酸盐岩地层条件、北衙-芹河NNW向向斜构造及斑岩的岩浆活动，构成了北衙金矿外带似层状Pb-Zn-Ag多金属矿床的主要控矿因素。综合该矿床地质特征、地球化学特征、控矿因素，对矿床成因进行了探讨，认为北衙金矿外带似层状Pb-Zn-Ag多金属矿床是富碱斑岩分异热液成矿作用的结果，是北衙富碱斑岩金多金属成矿系统外带的产物。

Geological Characteristics and Genesis of Layer-like Pb-Zn-Ag Polymetallic Deposit of the Periphery of Beiya Gold Deposit

Beiya Au-polymetallic mineral deposit is located at the southern segment of Jinshajiang-Honghe alkali-rich porphyry belt,it is the typical one of the mineral deposits metallogenesis related to related to alkali-rich porphyry.The geological characteristics and geochemical characteristics of layer-like Pb-Zn-Ag polymetallic deposit are researched in depth,the results show that:①the ore-hosting surrounding rocks of the Pb-Zn-Ag polymetallic deposit is consisted of the limestone within Beiya formation,middle triassic series,which is relatively rich in some mineralization elements such as Pb,Zn,Au etc and it is the advantageous ore-sourcing layer of Pb-Zn-Ag polymetallic deposit;②the ore-forming fluids of the Pb-Zn-Ag polymetallic deposit are NaCl-H₂O-CO₂ system characterized by medium-low temperature and salinity,which are derived from the magmatic hydrotherm differentiated by crystallization of the alkali-rich porphyritic body;③the contents of the S isotope of the ore-bodies is from -2.4‰ to +2.8‰,which indicates that the sulfur of this deposit has the same source from deep mantle as the porphyritic body,the partially strata sulfur is added in the later period,the Pb isotope analysis results show that the ore-forming materials are crust-mantle mixing in origin;④the specific Beiya formation carbonatite strata conditions,Beiya-Qinhe NNW-trending syncline tectonics and the magmatic activity of porphyry constitute the principal ore-controlling factors of the Pb-Zn-Ag polymetallic deposit.Based on the above research results,the genesis of mineral deposit of the Pb-Zn-Ag polymetallic deposit is analyzed,it show that the layer-like Pb-Zn-Ag polymetallic deposit is the results of alkali-rich porphyry differentiation hydrothermal mineralization,it is the periphery products of the Beiya alkali-rich porphyry-type gold polymetallic metallogenetic system.