Fine fraction sampling was also applied to a regional uranium survey
in the Ordos Basin with an area of 23,104 km2 (Yao et al., 2012). The
Ordos sandstone-type U deposit occurs in Jurassic sandstone, and is covered
by Cretaceous strata and soil. The designed sampling density was 1
site/4 km2. The fine fraction (−100 mesh, b0.147 mm) of the catchment
soil samples at a depth of around 150 mm was collected in the
field and later sieved to −200 mesh (b 0.074 mm) in the laboratory
for total analysis and selective leach by XRF and ICP-MS (Yao et al.,
2012). Table 7 summarizes the statistics of geochemical data from fine
fraction soil samples at Ordos Basin, Inner Mongolia, northern China.
The resultant anomalies can be closely correlated to the belt of sandstone
uranium mineralization (dashed line in Fig. 12).