云南牟定戌街地区铀矿化特征及成因探讨

云南牟定戌街1101铀矿区位于扬子地台西南缘,康滇地轴中南段,是我国西南地区产于元古界变质岩中的铀矿之一。通过对矿化区岩石及矿石的岩石学、矿物学、地球化学及年代学特征进行研究,分析了铀矿的形成条件,揭示了铀成矿规律。研究发现:①牟定戌街地区铀矿化赋存于斜长角闪岩、角闪斜长片麻岩和二云母石英片岩等变质混合岩中,主要铀矿物为晶质铀矿、钛铀矿及次生铀矿,含铀矿物有榍石、锆石,硫化物丰富,围岩蚀变主要为硅化、赤铁矿化、碱交代等;②牟定1101铀矿化地区混合岩化岩石的地球化学特征表现为高钾钙碱性-钙碱性系列岩石;③研究区混合岩形成于1 056 Ma左右,铀矿形成于845 Ma左右,为新元古代产物;④牟定1101地区铀成矿受构造、岩性控制,与混合岩化作用、构造热液活动及碱交代作用关系密切,属热液成因铀矿。

Uranium mineralization characteristics and genesis in Xujie area,Mouding, Yunnan province

The Muding Xujie 1101 uranium deposit,located in the south-west margin of the Yangtze platform,is one of the uranium deposits in proterozoic metamorphic rocks in southwestern China.In this paper,the petrological,mineralogical,geochemical and chronological characteristics of rocks and ores in the mineralized area are studied,the forming conditions of uranium deposits are analyzed,and the regularity of uranium mineralization is revealed.The results show that:1) Uranium mineralization occurs in metamorphic migmatites such as amphibolite,amphibole gneiss and mica quartz schist in Mouding Xujie area.The main uranium minerals are uraninite,brannerite and secondary uranium minerals.Uranium-bearing minerals include sphene,zircon,et al.Sulfides are very rich.The alteration of country rocks were mainly composed of silicification,hematitization,alkali metasomatism,et al;2) The geochemical characteristics of migmatized rocks in Mouding 1101 uranium mineralization area are characterized by high-K calc-alkaline-calc-alkaline series rocks;3) Migmatite in the study area was formed at about 1056Ma,uranium deposits were formed at 845 Ma,resulting from the beginning of Neoproterozoic;4) Uranium mineralization in Muding 1101 area is controlled by structure and lithology,closely related to migmatization,tectonic hydrothermal activity and alkali metasomatism,and belongs to hydrothermal uranium deposit.