柴达木盆地北缘石圈滩铀成矿地质特征、成矿规律及找矿标志OA

Shijuantan uranium deposit is the first medium-sized sandstone-type uranium deposit discovered in the northern margin of Qaidam Basin.In order to further understand its geological characteristics and metallogenic process,and guide the regional prospecting.This paper comprehensively studied the metallogenic geological background,ore-bearing layer characteristics,structural ore-controlling effect,orebody morphology,uranium mineral occurrence state,epigenetic alteration characteristics and the relationship between hydrocarbon fluid and uranium mineralization,based on the systematic collection and collation of previous research results,field exploration data and indoor core observation,geochemical analysis and mineralogical testing.The results show that Shijuantan uranium deposit mainly occurs in the fan delta front facies sand body of Lower Jurassic Xiaomeigou Formation,which is obviously controlled by the NW-trending fault structure and local monoclinic fault block.Uranium minerals are mainly pitchblende and coffinite,and some as uranophane and uranium accessory minerals.The ore-forming process has undergone multi-stage of fluid transformation and oxidation-reduction.Hydrocarbon fluid,as an important reducing medium,acted a key role in the precipitation and preservation of uranium.On this basis,the metallogenic regularity was summarized as"multi-source uranium supplystructural control-depositional limitation-hydrological drive-alteration uranium fixation"and the metallogenic model of"interlayer oxidation and structural transformation"was established.The four-in-one prospecting indicator system of"sand body framework-oxidation interface-rock response-geophysical anomaly"was proposed to provide theoretical basis and technical support for the uranium exploration in this and similar areas.