460火山岩盆地的地质发展与铀,钍演化

在总结460火山岩盆地地质特征和构造-岩浆活动发展历史的基础上。研究了各时代岩石中铀、钍的演化规律。提出该区晚太古代基底岩石的钾质混合岩化所引起的铀、钍增量是影响其后盖屋火山岩演化和铀成矿的物质基础;具有壳源重熔成因的上侏罗统酸性火山岩盖层,由于分布广泛,厚度巨大,有多种告石组台和多样的岩性序列,以及铀、钍含量高,构成了该区铀成矿有利的地层背景;燕山晚期沿区域断裂侵入的高铀酸性次火山岩或小侵入体,是该区成矿定位的决定因崇,它本身常成为赋矿的有刊围岩;后期热液铀成矿是使地层和岩体中铀和钍最终发生分离的主要地质作用。

GEOLOGICAL DEVELOPMENT AND URANIUM AND THORIUM EVOLUTIONS IN VOLCANIC BASIN NO. 460

On the basis of summarizing the geological features and the developmental history of tectono-magmatic activity, the uranium and thorium evolutional rules of rocks in different times are studied. It is suggested that the uranium and thorium increments caused by potassic migmatization of late Archean basement rocks in this area is the material base which affected the subsequent evolution of volcanic rocks and uranium mineraiization of the cover. The Upper Jurassic acid volcanic cover belonging to crustal remelting origin constituted the favorable stratigraphic background for uranium mineralization in this area due to its wide distribution, large thickness, various rock associations and littiological sequences, as well as high content of uranium and thorium. During the late Yanshanian stage acid subvolcanic rocks or small intrusions with high uranium intruded along the regional fractures are the decisive factors for the emplacement of uranium mineralization in this area, which often became the favorable wall rocks for preserving ores itself. During the Jute stage the hydrothermal uranium mineralization was the main geological process from which uranium and thorium in stratigraphy and terrain were finally separated.