西天山成矿带热液型金矿成矿地质条件及成矿物质来源对比

Comparative Study on Ore-forming Conditions and Sources of the Hydrothermal Gold Deposits in the Chinese Western Tianshan

西天山地区是我国重要的金成矿带，分布着许多类型的金矿床，主要包括穆龙套型、浅成低温热液型、斑岩型及石英重晶石脉型。本文分析了若干典型金矿床的地质特征，进行了金矿床流体包裹体显微测温及S、H、O稳定同位素测试。综合前人研究成果和有关测试数据，对比研究了不同类型金矿床的成矿地质条件、成矿流体及成矿物质来源特征。结果表明：西天山地区金矿床多受构造及相应的地层控制，矿床多形成于海西？印支期，成矿流体普遍具有低温、低盐度及低密度的特点，成矿物质中的硫主要为来源于地幔的深源硫。同时，西天山金矿床在南北两个成矿带存在着一定的差异。北部成矿带金矿床的形成与石炭系大哈拉军山组火山岩有着密切的关系，矿体主要受火山机构控制，成矿流体主要为大气降水，成矿深度小于1 km。南部成矿带金矿床普遍产于古生代含碳质浅变质细碎屑岩中，主要赋存于大断裂带或韧性剪切带内及其附近，成矿流体早期为岩浆水，后期随着成矿作用的进行混入了大气降水，成矿深度范围约在1.2～6.9 km之间。西天山地区古生代复杂的区域构造演化历史是造成西天山南北两个成矿带金矿床特征差异的主要原因。

The western Tianshan ore belt, one of the important gold metallogenic belts in China, hosts diverse types of gold deposit, including the Muruntau, epithermal gold deposit, quartz-barite vein and porphyry types of gold deposits. On the basis of the systematic analysis of geological characteristics, fluid inclusion, and stable isotopes of several typical gold deposits, this paper comparatively studied the ore-forming conditions and mineral sources of these deposits. The results indicate that these gold deposits are controlled by the geological structures and surrounding strata. The ore forming processes occurred mainly within Hercynian-Indosinian period. The ore-forming fluids are low-temperature, low-salinity, and low-density. The sulfur of these deposits mainly come from the mantle. However, differences exist between the northern and southern metallogenic belts in the western Tianshan. Gold deposits in the north metallogenic belt are associated with volcanic rocks of the Palaeozonic Dahalajunshan Formation, whose ore-forming fluid is mainly meteoric water and the metallogenic depth is less than 1 km. On the contrary, the deposits in the south metallogenic belt were hosted by slightly metamorphosed clastic rocks of the Palaeozoic and obviously controlled by the ductile shear or fault zone, of which the ore-forming fluid was mainly originated from deep-derived fluid for the early stage of ore-forming with input of meteoric water for the late stage, and the metallogenic depth of 1.2 to 6.9 km. The differences between two gold metallogenic belts may have been resulted from the complex tectonic evolution of the western Tianshan in Palaeozonic period.