THE WATER SOURCE FOR THE ORE FORMING HYDROTH ERMAL SOLUTION IN XIAZHUANG URANIUM FIELD
Liu Jinhui, Li Xueli, Shi Weijun, Sun Zhanxue (East China Geological Institute, Linchuan 344000)
On the basis of geological analysis in the Xiazhuang uranium field, this paper discusses, in more detail, the water sources of Xiazhuang ore forming hydrothermal solution, using hydrogen and oxygen isotopic compositions in fluid inclusions and water rock interaction principles. It is shown that δ 18 O=+6.90‰￣-9.80‰(SMOW), δ D=-30‰￣-85‰(SMOW) for Xiazhuang fossil ore forming hydrothermal solutions are in the range of the isotopic composition of meteoric water with “oxygen drift”. After water rock isotope exchange equilibrium, the δ 18 O values of rocks are evidently reduced. It indicates that the paleo groundwater reacted with rocks has very low δ 18 O value. The calculated results of isotope exchange equilibrium in different water/rock ratio prove that Xiazhuang ore forming fossil hydrothermal system has sufficient water sources and the calculated δ 18 O value (-8.26‰～+1.53‰) for hydrothermal solution after isotope exchange between meteoric water and rocks coincide with the δ 18 O(-6.54‰～+1.43‰) of hydrothermal ore forming solution. The recovered δ 18 O values by Craig meteoric line equation conform with the range of meteoric isotopic composition. These evidences suggest that the water source of hydrothermal ore forming solution in Xiazhuang uranium field are mostly derived from meteoric water.