东疆中天山红星山铅锌(银)矿床地质特征及区域成矿作用对比

A discussion on geological characteristics of Hongxingshan Pb-Zn (Ag) deposit in Middle Tianshan massif,eastern Xinjiang,with reference to regional metallogenesis

红星山铅锌矿床位于东疆中天山地块的东段。矿体赋存于青白口系天湖群红星山组第三亚组地层内,并受断裂构造的控制,主要呈脉状、透镜状顺层产出,含矿岩石为大理岩和碳质糜棱岩。金属矿物组合为方铅矿、闪锌矿、黄铁矿、磁黄铁矿、辉银矿,围岩蚀变主要有硅化、黄铁矿化、白云石化、碳酸盐化。矿石中硫化物的δ34S值为8.76‰～12.65‰;矿石的铅同位素组成与地层岩石铅的相似,并具有较好的相关性,显示出同源关系。流体包裹体的th集中于220～250℃,成矿流体的w(NaCleq)为3.39%～11.81%。区域岩石地球化学特征表明,青白口系天湖群内的大理岩、片麻岩及各类花岗岩中Pb、Ag的丰度值较高,可能是该区铅锌矿的矿源层,矿石的铅和硫同位素特征也指示成矿物质可能来源于地层。此外,该矿区内华力西期中酸性岩浆活动也可能提供了部分成矿物质。通过与同一成矿带内的彩霞山铅锌矿床、玉西银(铅锌)矿床对比,总结了东疆中天山地块内铅锌(银)矿的成矿特征及成矿规律。笔者认为,区域内铅锌(银)成矿与前寒武纪基底变质岩关系密切,矿体产于特定的地层层位和岩性建造(大理岩、含碳碎屑岩)内,并受一定构造部位的控制,华力西期岩浆活动对成矿具有改造变富作用,矿床成因类型属沉积变质-热液改造型层控矿床。

The Hongxingshan Pb-Zn （Ag） deposit is located in the eastern part of Middle Tianshan massif within eastern Xinjiang. Ore bodies are hosted by 3rd Subformation of Hongxingshan Formation in Tianhu Group of Qingbaikou System, with the host rocks composed of carbonaceous mylonite and impure marble. Ore bodies are mainly in the lenticular and veinlike forms, controlled by fracture structure. The ore mineral assemblage comprises galena, sphalerite, pyrite, pyrrhotite and argentite. The main types of wall rock alterations are silicification, pyritization, dolomitization and carbonatization. δ^34S values of sulfides range from 8.76 ‰ to 12.65 ‰, and ores and strata show similar lead isotopic characteristics. Homogenization temperature and salinity w（NaCleq） of fluid inclusions range from 220℃ to 250℃ and from 3.39 % to 11.81%, respectively. Regional petrogeochemical features indicate that the abundances of Pb, Zn, Ag in marble, gneiss and granite are relatively high, suggesting that the Tianhu Group strata might have served as the ore source bed and the Variscan intermediate-acid intrusion probably provided some of the ore- forming materials. Based on a comparison with Caixiashan and Yuxi deposits, the authors have summarized the ore-forming characteristics and regularity of Pb-Zn （Ag） deposits in this region. As the three typical deposits have some common characteristics, they must be governed by the same ore-forming regularity. The regional ore-forming process was closely related to the Pre-Cambrian crystalline basement. Ore bodies occurred in strata with favorable lithologic character （marble and carbonaceous clastic rock） and were controlled by certain structural positions, and mineralization resulted from the Variscan magmatichydrothemal activity. The Pb-Zn deposits belong genetically to the metasedimentary-hydrothermal reformed stratabound type. It is thus suggested that areas that have fracture structure in the Precambrian ore-bearing strata together with Variscan intermediate-acid magmatic activity are favorable places for ore prospecting.