1. IAEA TM On Origin of SUD: A global perspective
Origin of gray-green sandstone and new
exploration 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
2. IAEA TM On Origin of SUD: A global perspective
Outline
1 Geological setting
2 Unique features of the deposit
3 Origin of grey-green sandstone
4 Metallogenic and exploration model
14. 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
15. 2 Unique features of the deposit
(2) Coffinite dominant, not pitchblende
Coffinite crystal
16. 2 Unique features of the deposit
(3) Complex ore body shapes
Shape of ore body
Cross section of ore
body shape
17. 3 Origin of grey-green sandstone
Greenish sandstone originated from oil-gas
secondary reduction processes:
Secondary reduction processes: Took place
after the formation of uranium deposit
Green or gray-green sandstones: Paleo-
oxidation zone chloritization and
epidotization.
19. 3 Origin of grey-green sandstone
Geochemistry
Fe2O3/
Elements CaO CO2 S U
FeO
Greenish S. 3.96 2.83 0.04 0.41 3.4
Grey S. 1.64 1.02 0.75 0.12 14.3
21. 3 Origin of grey-green sandstone
Abundant oil and gas in greenish
sandstones
Oil-Gas Inclusions
22. 4 Metallogenic and exploration model
It can be concluded that the uranium
mineralization mechanism of the sandstone type
uranium deposit in the northeastern Ordos Basin
is very complicated, which underwent multiple
metallogenic processes, and superposition
metallogenic & exploration model established:
Preliminary enrichment process
Paleo-phreatic oxidation process
Paleo-interlayer oxidation process
Oil-gas secondary reforming process
Thermal modification process
23. 4 Metallogenic and exploration model
Superposition metallogenic & exploration model
(A) Preliminary enrichment stage
170Ma
24. 4 Metallogenic and exploration model
Superposition metallogenic & exploration model
(B) Paleo-phreatic oxidation stage
160~135Ma
25. 4 Metallogenic and exploration model
(1)Phreatic oxidation
process(J3)
Geochemically
Vertical Zonations:
U、V、Mo、Se、
Re
26. 4 Metallogenic and exploration model
(C) Paleo-phreatic+ Paleo-interlayer
oxidation stages 125~65Ma
27. 4 Metallogenic and exploration model
U
(2) Interlayer
oxidation
process (K1-E1)
Geochemically
Horizontal Zonations:
Mo
U、V、Mo、Re 、
S…
28. 4 Metallogenic and exploration model
(2)Interlayer S
oxidation
process
Horizontal
Zonations: Shape of
U 、 V 、 Mo 、 ore body
Re、S …
29. 4 Metallogenic and exploration model
Uranium found in the redox zone: formed
by both paleo-phreatic and interlayer
oxidation processes.
ilmenite
31. 4 Metallogenic and exploration model
Hydrothermal events:
Temperatures: 70oC to 170oC, Salinity from 8%
to 20%
148℃、
8.68Wt%NaCl
170℃、
3.39Wt%NaCl
32. 4 Metallogenic and exploration model
Hydrothermal process:
Hydrothermal mineral association:
Pyrite
Limonite Galena
Sphalerite
33. 4 Metallogenic and exploration model
Superposition Metallogenic Model
Superposition of metallogenic processes
Phreatic+interlayer Oxidation Oil-gas
reworking Hydrothermal reworking
Superposition of different U sources
Ore beds Provenence area Oil &Gas
Superposition of metallogenic fluids
U-bearing Water Oil-Gas Thermal Fluid
34. 4 Metallogenic and exploration model
New exploration indication
The Dongsheng deposit has unique features and
underwent complicated metallogenic processes,
among them oil-gas reforming process played
very important roles in uranium mineralization.
So correct identification on greenish sandstones
formed under paleo-oxidization and reformed
by oil-gas secondary reduction is very important
to explore for uranium deposits, especially in
those basin producing oil-gas…