渗出砂岩型铀矿成矿预测与找矿标志OACSTPCD

Based on the innovative mechanism and model of exudative sandstone-type uranium deposit,it is considered that the exudative metallogeny is different from infiltrating one and has different signatures and indications.Two key conditions should be firstly identified:one is the primary origin of uranium-bearing red-mottled sedimentary formation,the other one is the secondary reduction origin of ore-controlling grey sandstone body within the formation.The new targeting methods used to identify uranium mineralization in red-mottled sandstone pointed out:(1)combining information derived from the upper red and lower dark sedimentary formations,(2)identifying the pathways connecting the upper red formation with lower dark formation,and(3)finding the grey-greenish sandstone units in red-mottled formation,which hosts uranium mineralisation.Furthermore,this paper clarifies the conditions and indications for the regional prediction and evaluation,including presence of uranium-and organic matter-rich source rocks below the ore-bearing beds,regional structures,sedimentary formation,radioactive anomalies,and comprehensive predictive techniques.It is also pointed out that a small-sizeed depression can produce a large deposit.In addition,systematic predictive indications for exudative sandstone-type uranium deposits have been concluded,particularly easy macroscopic ones in the field work,such as ore-controlling structures,sedimentary configurations,alteration and modification,the color of uranium-mineralized sandstone and the characteristics of external organic matter.To be understood better,those indications are compared with traditional ones related to infiltrative sandstone uranium mineralization system.The established conditions and indications are not only of very significace to identify the origins of both"infiltration"and"exudation"metallogenies,but also with great values to clarify key ore-controlling factors,guide metallogenic prediction and exploration for the uranium deposits.