新疆东天山康古尔剪切带西段金矿床的成矿流体特征及其地质意义

东天山觉罗塔格地区沿着康古尔韧性剪切带发育众多金矿床,已经成为新疆重要的黄金产地之一。文章对位于该剪切带西段储量较大、勘查程度较高的红石、康古尔和马头滩3个金矿床进行了地质特征、流体包裹体和氢氧同位素研究,结果表明,这3个矿床含矿石英脉流体包裹体的均一温度分别为294.4~468.0℃(红石)、236.9~441.0℃(康古尔)、150.9~444.7℃(马头滩);盐度w(NaCleq)分别2.7%~10.5%(红石)、4.2%~9.1%(康古尔)和6.4%~8.4%(马头滩);密度分别为0.54~0.83 g/cm3(红石)、0.80~0.86 g/cm3(康古尔)和0.57~0.80 g/cm3(马头滩)。本文和前人数据表明,这3个矿床的δDSMOW值分别为-104‰~-63‰(红石)、-72‰~-45‰(康古尔)和-55‰~-45‰(马头滩),与石英相平衡的水的δ18OH2O值分别为-1.7‰~7.4‰(红石)、-8.3‰~5.0‰(康古尔)和2.5‰~2.6‰(马头滩)。以上特征表明,红石、康古尔和马头滩金矿床成矿流体具有中-高温、低盐度、较高CO2含量,其中红石金矿床的成矿流体中岩浆水比例比康古尔和马头滩两个矿床相对要高。综合地质、流体和年代学特征表明,沿康古尔韧性剪切带分布的金矿床可能具有较为一致的成因,可能是295~280 Ma和260~240Ma两个成矿期叠加作用的产物,分别与早二叠世拉张背景下的中-酸性岩浆的侵入和晚二叠世—早三叠世(260~240 Ma)挤压背景下康古尔剪切带的韧性剪切变形及抬升作用相对应。

Ore-forming fluids of main Au deposits in western Kangguer shear zone of Eastern Tianshan Mountains and their geological implications

There exist many Au deposits or ore spots along the Kangguer shear zone in Qol Tag area of Eastern Tianshan Mountains,which is one of the most important Au metallic zones in Xinjiang.This paper focuses on geological characteristics,ore-forming fluid inclusions and H-O isotopic compositions of three Au deposits which have experienced fairly high degrees of exploration(Hongshi,Kangguer and Matoutan from east to west) in the west segment of the shear zone.The homogenization temperatures of quartz fluid inclusions range from 294.4℃ to 468.0℃ for Hongshi,from 236.9℃ to 441.0℃ for Kangguer and from 150.9℃ to 444.7℃ for Matoutan;the salinities(w(NaCleq))range from 2.7% to 10.5% for Hongshi,from 4.2% to 9.1% for Kangguer and from 6.4% to 8.4% for Matoutan;the densities range from 0.50 g/cm3 to 0.83 g/cm3 for Hongshi,from 0.80 g/cm3 to 0.86 g/cm3 for Kangguer and from 0.57 g/cm3 to 0.80 g/cm3 for Matoutan respectively.According to data obtained from this study and previous researches,the δDSMOW isotopic values range from 104‰ to-63‰ for Hongshi,from-72‰ to-45‰ for Kangguer and from-55‰ to-45‰ for Matoutan,and δ18OH2O values range from-1.7‰ to 7.4‰ for Hongshi,from-8.3‰ to 5.0‰ for Kangguer and from 2.5‰ to 2.6‰ for Matoutan respectively.These analytical data combined with data available suggest that the ore-forming hydrothermal fluids of Hongshi,Kangguer and Matoutan Au deposits were mixed fluids of magmatic and meteoric water,characterized similarly by middle-high temperature,low salinity and high CO2 content.The ore-forming hydrothermal fluids of the Hongshi Au deposit probably had more magmatic water than Kangguer and Matoutan Au deposits.Combining these characteristics with geology,ore-forming fluids and chronology,the authors hold that the Au deposits distributed along the Kangguer ductile shear belt were probably formed by early Permian(295~280 Ma) and late Permian-early Triassic(260~240 Ma) two-stage mineralization,corresponding to the granitoid intrusion in the extension background and the ductile shearing action in the extrusion background respectively.