广西金鸡盆地砂岩型铀矿成矿机理和成矿模式研究OACSTPCD

Jinji Basin is a Meso-Cenozoic continental fault basin with the earliest discovery of sandstone type uranium mineralization in Guangxi.Its uranium host layers are featured with typical gray colour in red colour.The study on its metallogenic mechanism and metallogenic model may provide reference for uranium exploration with similar area of tectonic setting and horizon.This thesis analyzed its geological conditions of uranium mineralization from five aspects,including lithofacies paleogeography,paleoclimate,redox zone,uranium reservoir and uranium source by combining analogy analysis etc.Based on ground investigation and drilling disclosure,the basin uranium metallogenic mechanism and metallogenic model were summarized through analysis on orebody morphology,surrounding rock alteration and ore lithology as well as alteration characteristics.The uranium metallogenic space in Jinji Basin is controlled by gray reduction sand body.The studies showed that uranium mineralization in Jinji Basin had experienced four stages:the formation of thick purplish red oxidized sand bodies deposited in the early Lower Cretaceous which provided storage space for pooled uranium;formation of gray reduction sand bodies deposited in the late Lower Cretaceous which provided necessary geological conditions for uranium mineralization;the migration of U6+ in the oxidized sand body with pore water during the compaction diagenetic process and the reduction to U4+ in the sand body which were adsorbed by carbonaceous clasts and organic-containing mudstones in gray sandstone;the limited superposition mineralization in the small porosity rocks on the both sides of the structural plane by the late tectonic fluid activities.