甘肃北山地区白山堂铜矿地质特征及成矿流体研究

北山地区是我国重点成矿区带,蕴含很大的矿产资源潜力。以往工作发现斑岩型铜矿是北山地区重要的成矿类型,白山堂铜矿是其代表性斑岩型铜矿,但该矿至今一直未开展成矿流体的相关研究。本文进一步研究矿床地质特征,系统开展了矿床流体包裹体研究,发现其流体包裹体形态简单、多为气液两相,中低温(成矿期含矿石英脉均一温度230℃～260℃及160℃～170℃,共生黄铜矿爆裂温度约301℃)、低盐度w(NaCleq)]为11%～15%,均值11.32%及3.4%～7.7%,均值4.8%)、中等密度(约0.95～1.00 g/cm3)、中低压力(约5×103～101×103 kPa)等物理化学特征,综合认为流体具有中低温热液脉型矿化特征,结合地质特征及近矿外围一系列环绕石板泉二长花岗岩分布的中低温热液脉型-矽卡岩型-斑岩型Cu、Fe、Pb和Zn等矿化分带模式,认为白山堂铜矿为中低温热液脉型矿化类型,代表岩浆热液系统演化到晚期阶段的产物,并认为环绕石板泉二长花岗岩周缘的系列斑岩型-矽卡岩型-热液脉型矿化存在某种联系。

Geological Features and Ore-Forming Fluid of Baishantang Copper Deposit in Beishan Area,Gansu Province

The Beishan area in Gansu province is one of the most important metallogenic belts in China,with abundant mineral resources.Previous studies revealed that the porphyry copper deposit is the main metallogenic type in this area as represented by the Baishantang copper deposit,whereas there are rare studies on ore-forming fluid in this deposit.This work made a further study on geological characteristics of the deposit and its fluid inclusions.The results show that the fluid inclusions have simple shape,are mostly of gas-liquid two-phase type,medium to low temperature（230～260 ℃ and 160～170 ℃ of homogenization temperature in the ore bearing quartz veins and 301 ℃ of cracking temperature with chalcopyrite concomitant）,low salinity（11%～15% w（NaCleq）,averaged 11.32% w（NaCleq）;3.4%～7.7% w（NaCleq）,averaged 4.8% w（NaCleq））,moderate density（about 0.95～1.00 g/cm3） and medium to low press（about 5×103～101×103 kPa）.The deposit shows exothermal to epithermal vein type characteristics.Combined with geology feature and the series of hydrothermal vein-type,skarn-type,also porphyry-type Cu-Fe-Pb-Zn deposits distributed annularly center on the Shibanquan monzonitic granite surrounding nearby the Baishantang area,it is suggested that Baishantang copper deposit is the mineralization type of exothermal to epithermal vein type.It is the product to late stage of magmatic hydrothermal system evolution.There is some connection existed among the mineralization series surrounding Shibanquan monzonitic granite.