Geothermal gradient was low in Paleozoic and Early Mesozoic in Dongsheng area

Yimeng uplift

resulting in a low level of thermal evolution of source rocks

and it increased up to 3.3℃/100m in Late Mesozoic.The Late Mesozoic tectonic thermal events and the later continuous uplifting in Dongsheng area would have resulted in the active movement of thermal fluid.As a result

the coalification of Permo-Carboniferous

Triassic and Jurassic in the study area mainly occurred during Middle Jurassic to Early Cretaceous.Gas was mainly ge-(nerated) from the Paleozoic coal measure strata in Early Cretaceous

and the humic gas have mainly migrated and dissipated since Early Cretaceous

which is also the main mineralization period of the sandstone uranium impregnations in the area.Based on analyses of tectonic evolution and hydrocarbon generation history in the study area by using vitrinite reflectance and apatite fission track data

the hydrocarbons acting as the reducing agents for enrichment of uranium can only be sourced from the Permo-Carboniferous coal measure strata in the area with relatively high maturity to the south of Yimeng uplift

because the Permo-Carboniferous and Jurassic coal measure strata in the study area are still in immature to low mature evolutionary stages.