新疆哈密地区库姆塔格钼矿床地质特征和辉钼矿Re-Os同位素年龄

库姆塔格钼矿位于新疆东天山星星峡隆起区哈密库姆塔格沙垄的东侧,是一个产于基性岩中的辉钼矿矿床。区内目前已发现7条矿化体,这些矿化体围绕辉长岩与角岩/矽卡岩的接触带呈向北西突出的弧形展布。矿体内主要金属矿物有辉钼矿、黄铜矿、黄铁矿、磁铁矿等,辉钼矿、黄铜矿呈稀疏浸染状分布于辉长岩中。对辉长岩中的辉钼矿进行Re-Os同位素年龄测定,获得矿床形成的等时线年龄为(318±27)Ma,加权平均年龄为(319.1±4.5)Ma,成矿时代为早—中石炭世。这一测年结果与区域内的部分花岗岩的侵入时间一致,表明该矿床的形成与区内的酸性岩浆活动存在一定的联系,因此区内酸性岩体与中基性岩体的接触部位是寻找这类新型矿床的有利地段。库姆塔格钼矿的发现不仅打破了以往在酸性岩体内部和矽卡岩带内寻找钼矿床的勘探模式,同时也为在东天山地区内寻找铜钼多金属矿床开拓了思路。

Geological characteristics and molybdenite Re-Os isotopic dating of Kumutage Mo deposit, in Hami area, Xinjiang, China

Kumutage molybdenum deposit locates to the southeastern side of Kumutage sand ribbon, Hami area, Xinjiang. It is the first molybdenum deposit by far which molybdenite occurs in the basic rocks. Seven orebodies had been found in the district. All of them distribute around the arc contact zone between gabbro and hornstone/skarn. The main metal minerals are molybdenite, chalcopyrite, pyrite, magnetite, and so on. The molybdenite and chalcopyrite have the shape of sparse disseminated in the gabbro. This paper dates the age of molybdenite by Re-Os method. We obtain the isochron age of (318±27)Ma and the weighted average age of (319.1±4.5)Ma. These results imply that this deposit formed at Early-Middle Carboniferous. This age accorded with the intrusion time of granite in this area. So we infer that the metallogenesis is related with the activity of acid rocks in central Tianshan massif. The contact zone between acid rocks and intermediate to basic rocks is the favourable section for looking for this new type deposits. The discovery of Kumutage has important significance. Because it not only challenged to prospecting model for molybdenum deposits but also extended the prospecting ideas in the basement of eastern Tianshan.