Mineralization Of Uranium Deposits In The Quanzhou Ore Field In Guangxi Province

The Quanzhou uranium ore field is one of the typical carbon-silicon-shale uranium ore fields in the Huanan uranium metallogenic zone. Based on previous data collected, a detailed geological and geochemical study has been carried out on some typical uranium deposits in the ore field, with a focus on its metallogenic conditions and process. The following are the major achievements obtained in this thesis.Field geological survey and microscopic observation confirm that the host rocks in the Q uanzhou uranium field mainly include the Middle Devonian terrigenous clastic rocks of the Xindu Group with shallow marine carbonate rocks of the Tangjiawan Group and the Lower Devonian shallow marine carbonate rocks of the Liujiang Group. The stratified or lenticular ore bodies occur a long the F1 and F3 interlayer fracture zones, with occurrence consistent with that of the strata and structures. In the Quanzhou uranium ore field, the ore is predominated by siltstone and dolomite types. The ore minerals in the siltstone ores are mainly p itchblende, scheelite and a small amount of uranimite, and the gangue minerals mainly consist of quartz, chlorite, kaolinite and montmorillonite, etc. In contrast, the ore minerals in the dolomite ores are mainly pitchblend and scheelite, and the gangue minerals are mainly dolomite and calcite.Drilling and petrographic data show general occurrence of wall rock alterations of the Quanzhou uranium ore field in a narrow range near fault zones, with centralized and superimposed distribution of different types of alterations. The mineralization-related wall rock alterations include hematization, pyritization, galena-carbonation, chloritization, etc. According to vein interpenetrating, especially mineral assemblage and texture and structure of ores, the ore- forming process of the Quanzhou uranium ore field is divided into three periods, including sedimentation and rock-forming, hydrothermal and supergene periods, of which the hydrothermal period can be further divided into three stages, i.e. hematite-pitchblende, pitchblende-sulfide-calcite and calcite stages.The information obtained in this thesis supports an origin of the deposits in the Quanzhou uranium ore field via sedimentation superimposed by epithermal mineralization. In the sedimentation and rock-forming period, deposition with weathering and erosion of the Caledonian uranium-rich granite led to preliminary enrichment of uranium in the Middle to Upper Devonian strata of the area. In the hydrothermal period, uranium in the sedimentary rocks was activated and leached out by meteoric and ground water, forming ore-forming fluids. When the ore-bearing hydrothermal fluids migrated to the F1 and F3 interlayer fracture zones, the uranium finally precipitated because of the changes in Eh, temperature and pressure.