西藏哈海岗钨钼多金属矿床地质特征及辉钼矿铼-锇同位素定年
Geological Characteristics and Re-Os Dating of the Hahaigang W-Mo Polymetallic Deposit, Tibet
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摘要: 西藏墨竹工卡县哈海岗钨钼多金属矿床是近年来新发现的以钨钼为主的多金属矿床,也是念青唐古拉成矿带发现的第一个钨钼多金属矿床。文章简要地介绍了该矿床基本地质特征,利用Re-Os同位素定年方法对采自哈海岗矽卡岩型钨钼矿体中的2件辉钼矿进行了成矿年代的测定,获得的辉钼矿Re-Os同位素模式年龄分别为(140.1±2.8) Ma和(143.3±5.2) Ma,平均值为(141.7±4) Ma。测年数据表明,矿床成矿时代属于早白垩世,可能系班公湖—怒江洋向南俯冲碰撞阶段成矿作用的产物,早于其东侧亚贵拉、洞中拉石英斑岩的成岩年龄(126 Ma左右)。矿床成矿时代的厘定丰富了冈底斯—念青唐古拉成矿带矿床成矿系列,指示冈底斯成矿带存在早白垩世的成矿作用,该带至少存在四期独立的钼成矿事件;同时对于研究区域岩浆演化与成矿作用以及区域找矿预测也具有十分重要的意义。Abstract: The Hahaigang W-Mo polymetallic deposit in Maizhokunggar County, Tibet, is a tungsten and molybdenum polymetallic deposit, which is the first one to be explored in the Nyainqentanglha metallogenic belt. The basic geological characteristics of this deposit have been briefly presented in this paper. The mineralization age of this deposit has been obtained by using Re-Os isotopic dating methods. The Re-Os model ages of the two molybdenite samples from the Hahaigang skarn-type W-Mo orebody are (140.1±2.8) Ma and (143.3±5.2) Ma, with an average age of (141.7±4) Ma. Dating results showed that the ore-forming age of this deposit is Early Cretaceous, and was probably the product of mineralization during the southward subduction and collision stage of the Bangong—Nujiang oceanic crust. The model age is earlier than the diagenetic age (about 126 Ma) of quartz porphyries from the Yaguila deposit and Dongzhongla deposit on its eastern side. The definition of this deposit's mineralization age has enriched the metallogenic series of the Gangdise—Nyainqentanglha metallogenic belt, indicating the fact of Early Cretaceous mineralization and at least four stages of molybdenum mineralization existing in the Gangdise metallogenic belt. Meanwhile, it has great significance on the study of regional magmatic evolution and mineralization, as well as on the regional prospecting prognosis.
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Key words:
- Re-Os /
- dating /
- early /
- Cretaceous /
- subduction /
- stage
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