1. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
Mr.Choengchai KRAIKHONG
Department of Mineral Resources, Bangkok, Thailand
E-mail: choengchai@dmr.mail.go.th
The International Atomic Energy Agency’s
“Technical Meeting on the Origin of Sandstone Uranium Deposits: A Global
Perspective”
29 May – 1June 2012 at IAEA Headquarter Vienna, Austria

2. Content
 Overview Geographic Information of
Thailand
 Sandstone Uranium Deposits in Phu
Wiang Basin
 Genesis of The Phu Wiang Uranium
Mineralization
 Controls of Uranium Distribution
 The results of the Phu Wiang
Uranium Prospecting

3. Overview Geographic Information of
Thailand
 Area
513,115
sq.km
 Highest
Peak
El.2565
MSL.
 Provinces
76
Changwat

4. Geographic Significant
Topographic significant
1 -N,W mountainous
2 -Phetchabun range
3 -NE plateau 4
4 -Central plain
5 -E-Thailand
6 -S-peninsular
7 -Gulf of Thailand
8 -Andaman sea

5. The Geology of Thailand
: Regional Geology
Regional geology of Thailand
was described as the following of
 The sedimentary rocks sequence
from the Cambrian to Cenozoic.
 The metamorphic rocks was
described the older rocks as
Precambrian to Lower Paleozoic.
 The Igneous rocks was described
as Carboniferous, Permo -
Triassic, Triassic, Jurassic,
Cretaceous, and Quaternary.

6. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
 The uranium mineralization in the
Phu Wiang basin near the western
edge of Korat Plateau, Thailand
was discovered in 1970 after the
recognition by an unusual
concentration of uranium in ground
water.
 The outcrop of uranium minerals
associated with malachite in

7. Location map of Phu Wiang Uranium Prospect Area
17o
16o45’
U-Prospect
16o30’
101o45’ 102o 102o15’ 102o30’ 102o45’

8. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
 The Department of Mineral
Resources (DMR),Thailand started
to study the mineralized beds in
cooperation with the US
Geological Survey (USGS) in 1974
 And International Atomic Energy
Agency (IAEA) in 1976

9. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
 The first results revealed :
• a favorable environment for uranium
deposits related to the geological
similarity between the Khorat Plateau
and the Colorado Plateau.
• granites as sources rocks of the ‘red
bed’ sandstones and the uranium
mineralization.
• the occurrence of carnotite and
pitchblende (uraninite) associated

10. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
 Based on these promising results
• the DMR stared a drilling
programme in August 1976,
supervised by an IAEA expert. Until
mid 1980
• 26 hammer downholes and 85
diamond drill holes penetrated the
potential ore beds in the Sao Khua
Formation (Unit B), discovering 3
small ore lenses

11. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
 In 1978, the DMR and the German
team discussed the objectives of
the joint research programme and
determined 5 fields of activities :
1. Structural interpretations of
satellite imagery and aerial
photographs in order to prepare a
detailed tectonic map of the Phu
Wiang Basin.

12. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
2. Sedimentological studies of the
Sao Khua Formation in order to
provide detail information on the
host rock.
3. Economic geological
investigations in order to identify
the uranium minerals, the uranium
distribution and the genesis of the
ore.

13. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
4. Geochemical studies of magmatic
rocks around the Korat Plateau in
order to search for the possible
source rocks of the uranium
mineralization.
5. Prospecting tests in order to
provide information for
hydrogeochemical uranium
prospecting as well as for
radiometric borehole logging.

14. Sandstone Uranium Deposits
in Phu Wiang Basin, Thailand
 The Thai-German research project
was implemented between 1979 –
1981. The field work was
concentrated on
• sampling and investigating drill cores
• sampling of sandstone outcrops of the Sao
Khua Formation
• mapping and sampling of Paleozoic
sediments in the Petchabun province
• sampling of groundwater from drillholes

15. structural interpretations of satellite
imagery and aerial photographs in order to
prepare a detailed tectonic map of the
Phu Wiang Basin.

16. Jpk
JKpw
Kpp
Ksk
Qa
Kkk
TRnp
Geologic map of the Phu Wiang Uranium Prospecting area

17. Khorat Group

18. Sedimentological studies of the Sao Khua Formation
In order to provide detail information on the host rock.

19. Detailed geologic map of the uranium
mineralization in Phu Wiang Prospect area

20. Outcrop of uranium in sandstone at Pra Tu Tee Ma, Ban Nong Kham,
Amphoe Phu Wiang, Khon Kaen Province.

21. economic geological investigations
in order to identify the uranium minerals,
the uranium distribution and the genesis of the ore.

22. geochemical studies of magmatic rocks around the Korat Plateau
in order to search for the possible source rocks of the uranium mineralization.

23. prospecting tests in order to provide information for hydrogeochemical
uranium prospecting as well as for radiometric borehole logging.

24. Methods used in the uranium exploration project
Gamma-ray Spectrometer
survey
Diamond Drill Holes
Carborne Scintillometer
(CBS) Survey
Gamma-ray Borehole
Logging

25. Genesis of the Phu Wiang Uranium
mieralization
 The Phu Wiang Uranium Prospect
exemplifies a special subtype of uranium
deposits in the sandstones, The copper-
uranium mineralization is associated with
the mudstone pebbles forming layers in the
channel sandstones and is derived from
older pedogenic uranium accumulations.
The genetic importance of such deposits to
origin of deposits of main types is
postulated.

26. Genesis of the Phu Wiang Uranium
mieralization
 The Phu Wiang uranium deposit consists of
three laterally associated lenticular ore
layers with the minimum dimension of 30 x
10 m.,65 x 15 m. and 200 x 100 m. and
thickness ranging from 0.3 to 1.2 m. The
average grade is about 0.04 % eU3O8 (cutoff
: 0.01 % eU3O8). The typical subsurface
trend, shape and form of the ore-bodies in
the Phu Wiang are shown in the drilling
cross-sections As illustrated,the deposit is
tabular and lenticular, trending parallel to the
bedding and thus similar to the epigenetic,

27. Cross-sections of the uranium mineralization in Phu Wiang Prospect area

28. eU3O8

29. Genesis of the Phu Wiang Uranium
mieralization
 Due to a very fine grain size of
mineralization several analytical techniques
including electron microprobe, energy
dispersive spectrometry, electron scanning
microscopy, X-ray diffractometry and ore
microscopy have been applied in order to
identify the uranium minerals.
 The analytical data indicate that coffinite is
the principal uranium mineral and that a
considerable amount of the uranium is
bound in organic complexes or is absorbed
on clay.

30. Genesis of the Phu Wiang Uranium
mieralization
 Some electron microprobe data point to a
possible presence of uraninite or uraninite-
like mineral occurring in a submicroscopic
mixture with coffinite.
 The X-ray analysis, however, yielded
evidence of coffinite only.
 Other uranium minerals detected include
carnotite and torbernite. Both minerals are
extremely rare and their occurrence is
restricted to the outcrop of mineralized
sandstone.
 Associated ore minerals include

31. Genesis of the Phu Wiang Uranium
mieralization
 These minerals disseminate in the
mudstone chips as well as intragranular
filling and grain coating. The paragenesis of
ore minerals indicates clearly the
predominantly sulfide zone character and
low oxidation stage of the ore.

32. Drill holes location of the uranium mineralization in Phu Wiang Prospect area

33. Controls of Uranium Distribution
 The gamma-logging of the drill cores clearly
indicates that uranium is concentrated
preferentially in the gray to greenish
conglomeratic or pebbly sandstone at the
base of the ore bearing unit.
 The conglomeratic sandstone consists of
massive sandstone as typical for upper flow
regime in fluviatile environment and contains
variable amounts of scattered pebbles
(seams, galls, chips) of calcareous
mudstone.

34. Gamma-ray Spectrometer logging in drill hole DDH 63

35. Controls of Uranium Distribution
 The presence of coalified plant fragments
points to a surfacial origin of associated
mudstone pebbles. Genetically, the
conglomeratic sandstone can be used as an
indicator for a cyclic deposition in fluviatile
environment forming the best of a
depositional cycle.
 However, layers of conglomeratic sandstone
occurring in the middle and upper part of the
ore bearing unit are uranium free, regardless
of the content of coalified plant material.

36. Controls of Uranium Distribution
 The relationship between conglomeratic
sandstone and the uranium mineralization
indicates that the ore was controlled by
lithologic type and the initial depositional cycle
in a fluviatile channel environment.
 the results of economic geological investigation
of the Phu Wian Uranium Prospect indicate
little hope for the discovery of economic
uranium deposits, The main reasons for this
pessimistic outlook are that the mineralization
is low grade, the ore lensed are small, the
coffinite is very finely disseminated and a

37. Dinosaur remains were first found and reported in 1978 in the course of
Uranium prospecting at Phu Wiang from the Sao Khua Formation.

38. Phu Wiang Dinosaur Museum

39. Phu Kum Khao Dinosaur Museum

40. The nationwide airborne gamma-ray spectrometer survey
1984-1989

41. Magnetic K

42. U Th

43. Some of uranium occurrences in Pegmatite granite
In western part of Thailand

44. Conclusion
 The sandstone uranium deposit in Phu
Wiang basin contains low grade
uranium of about 30-60 cm. thick at an
average of 0.0407 % U3O8
 Calculate ore reserve is about 14.5 tons
of low grade ore in which about 1.7 tons
of U3O8 at 0.04 % could be extracted.
 The tendency to find a big uranium
deposit is rather rare

45. Conclusion
 Discovery of dinosaur remains in
uranium prospecting at Phu Wiang are
by products and led to the
establishment of several dinosaur and
geological museum in Thailand.
 The other uranium occurrences are too
small or only traces in fluorite viens in
granite and in pegmatite which can not
be classified as economic deposits.