GUO Rui1, CHEN You-liang1,2*, LIU Kai-peng3, ZHENG Yu-wen1, HU Yang1
(1. College of Geosciences, Chengdu University of Technology, Chengdu 610059, China;
2. Key Laboratory of Nuclear Techniques in Geosciences, Chengdu University of Technology, Chengdu 610059, China;
3. No.203 Research Institute of Nuclear Industry, Xianyang 712000, China)
Abstract: Migmatite type uranium deposit is the most promising type for the exploration of uranium resources in the Kangdian Axis. The uranium mineralization in the Haita area is a typical representative of this type of uranium deposit. In this paper, fluid inclusions of the quartz in quartz-feldspar vein ores, uraninite-bearing quartz veins, and ore-bearing hydrothermal quartz veins in the Haita deposit have been studied. The results show that there are two stages of uranium mineralization of the migmatite type uranium deposit in the Haita area. The hydrothermal fluid of early ore-forming stage, sourced from the migmatization, is characterized with high temperature and medium-low salinity, with homogenization temperatures of fluid inclusions ranging mainly from 380 ℃ to 540 ℃, and salinities varying mainly from 16.15% to 23.18%NaCl eqv. The early ore-forming stage is the main stage of uranium mineralization in the area. The hydrothermal fluid of the late ore-forming stage, which is a superimposed transformation metallogenic stage, is characterized with medium-low temperature and low salinity, with homogenization temperatures of fluid inclusions ranging mainly from 140 ℃ to 220 ℃ and salinities varying mainly from 5.56% to 23.18%NaCl eqv. This late ore-forming stage is the formation stage of high grade uranium orebodies in the area. The analysis of gas phase compositions of fluid inclusions show that fluid inclusions of the quartz in quartz-feldspar veins contain dominated CH4 and CO2, and minor H2O and N2. Fluid inclusions of the quartz in uraninite-bearing quartz veins and ore-bearing hydrothermal quartz veins contain dominant H2 and partly minor CO2, CH4 and H2O. The hydrogen and oxygen isotopes show that the ore-forming fluid of the early migmatization metallogenic stage may be the mixture of magmatic water and metamorphic water, while that of the late hydrothermal superimposed transformation stage could contain a certain amount of meteoric water.
Keywords: fluid inclusion; microtermometry; laser Raman spectroscopy; hydrogen and oxygen isotopes; migmatite type uranium deposit; the Haita area
ACTA MINERALOGICA SINICA Vol. 40, No.2, 2020, page 137-148
