四川冕西岩体岩石地球化学特征及铀成矿条件分析

冕西花岗岩体位于康滇地轴北段,区内已发现铀矿点3个、铀矿化点4个以及大量铀异常(带)。收集整理了该岩体以往地质资料,开展了岩石地球化学分析及电子探针测试等工作,对其铀成矿条件进行了综合分析。结果表明: 冕西岩体SiO₂含量偏高,一般为73%~78%,平均达75.09%,碱度高,K₂O+Na₂O平均含量大于8%,是在伸展构造环境下形成的A型花岗岩,为多期多阶段形成的复式花岗岩体,岩浆分异演化程度较高,岩体内断裂构造发育,并广泛发育以煌斑岩脉为代表的基性岩脉。区内存在煌斑岩脉型、碱交代型和碎裂蚀变岩型3种铀矿化类型,铀矿化受断裂构造、煌斑岩脉及热液蚀变的控制,并提出岩体北段具有较好的铀成矿条件,可作为下一步铀矿勘查的重点地段。

Analysis of Geochemical Characteristics and Uranium Metallogenic Conditions of Mianxi Pluton in Sichuan

Mianxi granitic pluton is located in the northern segment of the Xikang-Yunnan Axis. In the area, there has been the occurrence of three uranium deposits, four uranium mineralization sites, and a large number of uranium anomalies (zones). With a collection of previous geological data about this granitic pluton, the paper has made a comprehensive analysis on its uranium mineralization conditions through demonstrative geochemical study and electron probe test, etc. The results show that Mianxi granitic pluton has a high content of SiO₂ averaged at 75.09% (typically 73%-78%) and high alkalinity with an average content of K₂O+Na₂O greater than 8%. It belongs to type A granite formed in the setting of extensional structure and is identified as a composite granitic pluton developed in multiple phases and stages.With a high degree of magmatic differentiation and evolution, the pluton has developed a fracture structure and extensive basic dikes represented by lamprophyre veins. There are three types of uranium mineralization in the area, i.e., lamprophyre veins, alkalic metasomatism and fractured alteration. Besides, uranium mineralization is subject to the fracture structure, lamprophyre veins and hydrothermal alteration. As proposed in the paper, the northern segment of the pluton has better conditions for uranium mineralization, so it can be targeted as the key area for further uranium exploration.