IAEA TM On Origin of SUD: A global perspective Origin of gray-green sandstone and newexploration model for Dongsheng sandstone uranium deposit in oil-gas and coal productive Ordos basin, China Dr. Ziying LI Beijing Research Institute of Uranium Geology 2012.5.29-6.1 2007.11.1-10, Trivandrum
IAEA TM On Origin of SUD: A global perspectiveOutline1 Geological setting2 Unique features of the deposit3 Origin of grey-green sandstone4 Metallogenic and exploration model
Braided stream system Uranium in Braided distributary Channels
1 Geological SettingTectonics (J) The Dongsheng tectonic slope block: dipping southwards or SW with 2o-5o. Recharge-runoff- discharge hydrodynamic (K) system Dongsheng block provided the basic conditions for uranium mineralization.
2 Unique features of the deposit(1) Uranium mineralization controlled by the redox zone between grey and grey-green sandstones Greenish Sandstone Paleo-phreatic oxid. Interlayer oxid. Ore body Gray Sandstone
2 Unique features of the deposit(2) Coffinite dominant, not pitchblende Coffinite crystal
2 Unique features of the deposit (3) Complex ore body shapes Shape of ore bodyCross section of orebody shape
3 Origin of grey-green sandstoneGreenish sandstone originated from oil-gassecondary reduction processes:Secondary reduction processes: Took placeafter the formation of uranium depositGreen or gray-green sandstones: Paleo-oxidation zone chloritization andepidotization.
3 Origin of grey-green sandstoneAbundant oil and gas in greenish sandstones Oil-Gas Inclusions
4 Metallogenic and exploration model It can be concluded that the uraniummineralization mechanism of the sandstone typeuranium deposit in the northeastern Ordos Basinis very complicated, which underwent multiplemetallogenic processes, and superpositionmetallogenic & exploration model established: Preliminary enrichment process Paleo-phreatic oxidation process Paleo-interlayer oxidation process Oil-gas secondary reforming process Thermal modification process
4 Metallogenic and exploration modelHydrothermal events: Temperatures: 70oC to 170oC, Salinity from 8% to 20% 148℃、8.68Wt%NaCl 170℃、 3.39Wt%NaCl
4 Metallogenic and exploration model Hydrothermal process: Hydrothermal mineral association:PyriteLimonite GalenaSphalerite
4 Metallogenic and exploration modelSuperposition Metallogenic ModelSuperposition of metallogenic processes Phreatic+interlayer Oxidation Oil-gasreworking Hydrothermal reworkingSuperposition of different U sources Ore beds Provenence area Oil &GasSuperposition of metallogenic fluids U-bearing Water Oil-Gas Thermal Fluid
4 Metallogenic and exploration modelNew exploration indicationThe Dongsheng deposit has unique features andunderwent complicated metallogenic processes,among them oil-gas reforming process playedvery important roles in uranium mineralization.So correct identification on greenish sandstonesformed under paleo-oxidization and reformedby oil-gas secondary reduction is very importantto explore for uranium deposits, especially inthose basin producing oil-gas…