关键词: 方解石, 碳氧同位素, 3He/4He比值, 东胜铀矿

Abstract:

Research on calcite in Dongsheng uranium area is carried out including the enrichment characteristics, inorganic carbon
and oxygen isotopes, neighboring gas reservoirs inclusions trapping pressure, organic carbon isotopes and 3He/4He ratios. The results
show that there is a close relationship between Dongsheng uranium mineralization and deep natural gas. The δ13C values range
from -19.6‰ to -1.11‰ and the δ18O values range from -17.13‰ to -9.00‰ in calcite. The values of δ13C vary widely, maybe due to
the influence of surface water and deep natural gas. The gas reservoirs inclusion trapping pressures decreased from the deep to the
superficial part and from southwest to northeast in northern Ordos Basin, indicating that natural gas has supplied sufficient reducer for
the conversion of uranium necessary for the formation of large-scale uranium. The 3He/4He ratio in natural gas indicates that Dongsheng
Zhiluo uranium sandstone has no meaningful contribution from mantle fluids. The evidence shows that the calcite is a result of joint
actions of surface water and deep gas in Dongsheng uranium sandstone, suggesting that Dongsheng large-scale uranium deposit was
formed by the effect of cryogenically mixed mineralization.

Key words: calcite, carbon and oxygen isotopes, 3He/4He ratio, Dongsheng uranium deposit