巴里坤小加山钨矿床的成矿流体及矿床成因

小加山钨矿床位于新疆巴里坤地区,属石英脉型钨矿床。矿体赋存于邻近海西晚期花岗岩侵入体附近的中泥盆统大南湖组第一亚组第二段(D2d12)的变晶屑凝灰岩中。黑钨矿石英脉分为灰色含钨石英脉和白色含钨石英脉两种。岩相学观察认为,含矿石英脉中流体包裹体主要为两相水溶液包裹体, EW 走向的灰色石英脉包裹体气液比大, SN 走向的白色石英脉包裹体气液比较小。显微测温结果显示灰色石英脉均一温度(Th)范围为143~354℃,白色石英脉 Th 范围为154~312℃。激光拉曼探针显示小加山钨矿床含黑钨矿石英脉中流体包裹体含有少量 CO2组分。H、O 同位素研究表明：钨矿床成矿流体来源以岩浆水为主。成矿演化过程为：岩浆岩侵入活动→岩浆水运移分离→含钨络合物迁移搬运→冷却富集成矿,成矿晚期流体有大气降水的混合。与赣南钨矿的对比研究表明,小加山钨矿床与赣南钨矿床的成矿流体特征相似；在构造环境上,小加山钨矿床位于东准噶尔造山带和东天山成矿带的交汇复合部位,与位于武夷山和南岭两大成矿带的交汇复合部位的赣南钨矿床成矿环境相似。

Ore-forming Fluid and Genesis of Xiaojiashan Tungsten Deposit in Barkol District

The Xiaojiashan tungsten deposit, located in the Barkol region of Xinjiang, is a quartz vein type tungsten deposit. The ore bodies occur in a Late Hercynian granite intrusion near the metamorphic crystal tuff that consists of the second lithologic section of the first Dananhu Sub-group in Middle Devonian (D2d12). The tungsten-bearing quartz veins are divided into gray wolframite-quartz vein and white quartz vein. Based on petrography observation, fluid inclusions in both kinds of vein quartz are mainly aqueous type inclusions. The EW-trending gray quartz veins have higher vapor/liquid ratios than the SN-trending white quartz veins. Microthermometry shows that gray quartz veins have Th of 143 354? ℃, and white quartz veins have Th of 154 312? ℃. Laser Raman test shows that CO2 is rarely found in fluid inclusions of the wolframite-bearing quartz veins. Hydrogen and oxygen isotope compositions indicate that the ore-forming fluids of the tungsten deposit is magmatic water. During the ore-forming process, magmatic water separated from magmatic intrusion and brought tungsten complex to a position where tungsten-bearing ores could be deposited. The mixing of magmatic water and meteoric water took place in the late stage. The ore-forming fluids of the Xiaojiashan tungsten deposit are similar to those from the other tungsten deposits in the southern Jiangxi province in China. Tectonically, the metallogenic belt in Xiaojiashan locates at the intersection of the East Junggar orogenic belt and the two major metallogenic belts of the Eastern Tianshan Mountains, which is similar to the tungsten mining area in Southern Jiangxi in terms of metallogenic model.