钠长石与水云母型铀矿成矿特征对比与成矿机理探讨

COMPARISON IN METALLOGENETIC CHARACTERISTICS OF ALBITE-TYPE AND HYDROMICA-TYPE URANIUM DEPOSITS AND DISCUSSION ON THEIR METALLOGENETIC MECHANISM

本文以６２１与６７０地区为例，概述了钠长石与水云母型铀矿产出的地质背景及成矿前期岩石的蚀变特征，综合分析了这两类蚀变岩型铀矿矿石结构构造、矿物成分、共生元素、成矿温度、成矿时间、流体成分及放射性场等方面的差异性。探讨了这两类铀矿不同的成因机制：钠长石型铀矿成矿物质主要来自围岩，铀以碳酸铀酰络离子［ＵＯ２（ＣＯ３）３］４形式搬运，铀的析出富集主要由溶液成分、碱度发生突变所引起；而水云母型铀矿成矿物质主要来自富铀的火山期后热液，铀以钼酸钠酰络离子［ＵＯ２（ＭｏＯ４）２］２形式迁移，铀沉淀富集主要由溶液温度、压力降低所引起。

Taking the areas No. 621 and No. 670 as examples, this paper briefly expounds the geological setting for the occurrence of albite-type and hydromica-type uranium deposits andtheir near-ore alteration characteristics of pre-ore stage, synthesizes and analyses the differences between these two altered rock-type uranium deposits in terms of ore texture andstructure, mineralogical composition, associated elements, ore-forming temperatures andtime, composition of ore-forming fluids and radioactive fields. It has been probed into thatthese two types of uranium deposits possess different genetic mechanism: the ore-formingmatter in the albite-type uranium deposit mainly came from wall rocks, uranium was transported in the form of carbonate uranyl complex ion [UO2 (CO3 )3]4 and uranium precipitationand concentration mainly resulted from the sudden changes of solution compositions and alkalinity, whereas the ore-forming matter in the hydromica-type uranium deposit was mainlyoriginated from the uranium-rich postvolcanic hydrothermal solutions in the post-volcanic period, uranium was transported in the form of molybdate uranyl complex ion [UO2(MoO4)2]2-, and uranium precipitaion and concentration were mainly caused by the declinein solution temperature and pressure.