砂岩型铀矿集聚区成矿背景与成矿条件——以东胜砂岩型铀矿床为例

成矿大地构造背景、盆地形成地质环境及其盆地类型、后期构造改造等是砂岩型铀矿形成前提条件;砂岩型铀矿主要受外生沉积条件、后成水文条件及物理化学环境制约;以东胜大型砂岩型铀为例,对砂岩型铀矿成矿机制与演化、铀矿床空间分布特点及规律等方面进行讨论;探讨了鄂尔多斯盆地地质背景、成矿条件、矿床地质特征、控矿因素及成矿作用,提出砂岩型铀矿成岩、后生、低温热液成矿阶段形成的特态相矿物群,论述了低温成矿作用的矿物学及物理化学证据,认为东胜大型砂岩型铀矿具有沉积预富集-古层间氧化淋滤-后生二次还原与交代的成因特征.

THE BACKGROUND AND CONDITION OF THE SANDSTONE URANIUM DEPOSIT-CONCENTRATED AREA AND MINERALI ZATION——EXAMPLE OF DONGSHENG SANDSTONE URANIUM DEPOSIT

The paper elaborates the geotectonic background and puts forth that the geological setting and the basin type and the late tectonic rework are the prerequisites of the formation of sandstone uranium deposits.The deposits are constrained by exogeneous sedimentary condition,subsequent hydrological condition and physio-chemical environment.Ore mechanism and evolusion of the sandstone uranium deposits and their spatial distribution pattern etc.are discussed.Taking Dongsheng large size uranium deposit as an example geological background of Ordos basin and metallogenic condition and geological characteristics,metallogenesis and ore-control factors of uranium deposits in the basin are discussed and the specially-phased mineral group formed in the diagenetic,subsequent,low temperature hydrothermal ore-forming stages are pointed out and mineralogical,physio-chemical evidences of uranium metalloogenesis are also discussed.Dongsheng large size sandstone uranium deposit is characterized by the pre-concentration of sedimentary uranium-paleo interformation oxidation and leaching-subsequent secondary reduction and replacement genesis.