银额盆地拐子湖坳陷苏红图组地下水铀溶解-沉淀水文地球化学特征OA

The Guaizihu depression is a major secondary structural unit with prominent uranium metallogenic potential in the Yingen-Ejin basin.This study investigated hydrogeochemical characteristics of uranium dissolution and precipitation in groundwater.This paper systematically revealed the laws of uranium dissolution and precipitation in both ore-forming period paleo-groundwater and modern groundwater of the Suhongtu Formation in the Guaizihu depression,and quantitatively defines the hydrogeochemical boundary conditions for uranium mineralization.Based on field geological and hydrogeological surveys as well as sample collection,with water-rock interaction leaching tests and PHREEQC hydrogeochemical simulation,we quantitatively characterize the features of uranium dissolution and precipitation.In the study area,modern groundwater shows a pH range of 7.7～10.5,an Eh range of-100～136 mV,and uranium content of 0.05～12.16 μg·L-1.Paleo-groundwater during the ore-forming period had a pH range of 5.85～9.63,an Eh range of-250～92 mV,and uranium content of 0.02～0.616 mg·L-1.For modern groundwater of the Suhongtu Formation,the critical Eh values for pitchblende precipitation are-214.2～-41.83 mV,and the critical uranium concentrations are 1.52～2 241 mg·L-1.During the ore-forming period,the critical Eh values for uranium dissolution and precipitation were-95.50～167.29 mV,and the critical uranium concentrations were 0.1～463.37 μg·L-1.The sampling site YESY-120 is close to the critical conditions for uranium precipitation.The depth interval of 450～550 m in section ZKC9 presents favorable hydrogeochemical conditions for sandstone-type uranium mineralization.The above findings supply scientific references for quantitative discrimination of uranium dissolution and precipitation.It provides key support for delineating prospective areas and conducting prospecting prediction of sandstone-type uranium deposits.