康滇地轴大田地区铀成矿与重大地质事件

康滇地轴混合岩型铀成矿与混合岩化、构造以及脉岩的关系一直以来存在较大的争议,而大田地区分布的混合岩、长英质脉岩(构造蚀变带内)以及辉绿岩/花岗质脉岩,尤其是富含石墨矿物的石英片岩的年代学特征成为解决这一问题的理想研究对象。在结合研究团队前期年代学研究工作的基础上,本文对大田地区辉绿岩/花岗质脉岩、富石墨石英片岩进行了系统的年代学研究,并获得以下认识:(1)大田地区混合岩化作用发生于840～860 Ma,其原岩形成时代为中元古代;(2)晶质铀矿形成年龄约为775 Ma,与混合岩化作用并无直接的关系,其形成年代与辉绿岩/花岗质脉岩、构造蚀变带内脉岩形成年代较为接近,表明可能为一期产物;(3)锆石中U含量结果分析表明U元素在混合岩化过程中发生了明显的富集现象,表明混合岩是最可能的铀源之一;(4)粗粒晶质铀矿的形成与Rodinia大陆的裂解具有一定的耦合关系,期间断裂活动和脉岩活动提供了成矿热源、流体以及储矿空间。

Significant geological events related to uranium mineralization in the Datian area, Xikang-Yunnan Geo-Axis

The relationship between migmatite-type uranium mineralization and migmatization, structure and dykes in the Xikang-Yunnan Geo-axis remains controversial. The geochronological characteristics of migmatite, felsic dykes (within tectonic alteration zone) and diabase /granitic dykes distributed in the Datian area, especially graphite -rich quartz schist, are ideal research targets for solving this problem. Based on the previous geochronological work of the research team, this paper conducts a systematic geochronological study of the diabase/granitic dykes, felsic dykes and graphite-rich quartz schist in the Datian area. Results show that (1) the migmatization in the Datian area occurred in 840~860 Ma when the original rock was formed in Mesoproterozoic. (2) The formation age of uraninite is about 775 Ma, which is not directly related to migmatization, while close to that of diabase/granitic dykes and felsic dykes, indicating that it may be the product of the same period. (3) The analysis of the U content in zircon shows that the U element in migmatite is significantly enriched compared to the diabase /granitic dykes and felsic dykes, implying that the migmatite is one of the possible sources of uranium mineralization. And (4) the formation of uraninite has a certain coupling relationship with the breakup of the Rodinia continent, during which triggered fault and dykes activities provided the heat source, fluid and storage space for uranium mineralization.