Sifangtai Formation, Daqing Placanticline, Songliao Basin, Inner Mongolia, Chinai

Regional Level Types
Sifangtai Formation	Formation
Daqing Placanticline	Anticline
Songliao Basin	Basin
Inner Mongolia	Autonomous Region
China	Country

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Lower Member of the Sifangtai Formation (K2s1): It represents a meandering river deposit formed in a humid climatic environment during the early sedimentary stage, with a thickness of 20~35 m. Its lithology is dominated by gray and grayish-green fine sandstone, medium-coarse sandstone and pebbly sandstone. It has an abrupt contact with the mudstone of the Nenjiang Formation at the base, with developed erosion surfaces and commonly observed trough and tabular cross-beddings. Carbonaceous laminae are widespread in the gray sandstones, while pyrite is rare. The sandstones locally contain abundant flat and subrounded mud gravels and gravels with unsorted sizes and oriented arrangement. The above characteristics indicate that the Lower Member of the Sifangtai Formation represents channel bottom lag deposits with well-developed sand bodies and abundant reducing media such as carbon fragments and organic matter. It has a close association with uranium mineralization and serves as the main uranium-bearing horizon in the study area.
Middle Member of the Sifangtai Formation (K2s2): It corresponds to shore-shallow lacustrine facies deposits, with flood plain deposits developed locally, and has a thickness of 35~55 m. Its lithology is dominated by light-grayish-green, light-gray, purplish-red and brownish-red argillaceous siltstones and silty mudstones, with thin-bedded sandstones intercalated in between. This member is dominated by fine-grained deposits with poor water permeability, serving as the upper aquiclude for the Lower Member of the Sifangtai Formation.
Upper Member of the Sifangtai Formation (K2s3): It corresponds to meandering river deposits formed under arid paleoclimatic conditions, with a thickness of 25~50 m. Its lower part is lithologically dominated by light-gray, light-grayish-green and brownish-red fine sandstones and siltstones, with grayish-white calcareous sandstone bands intercalated locally, and calcareous concretions, calcareous lumps and mud gravels are well developed. The upper part is dominated by fine-grained deposits such as brownish-red variegated argillaceous siltstones and silty mudstones intercalated with purplish-red, brown, light-gray and light-grayish-green facies, with thin layers of light-gray siltstones intercalated locally. The hydrodynamic force during the sedimentary stage of this member was stronger than that of the Middle Member of the Sifangtai Formation; sand bodies of a certain thickness are developed in some drill holes with good water permeability, which can also form favorable uranium reservoirs.
On the plane, uranium mineralization in the Sifangtai Formation has a wide distribution, forming three mineralization enrichment areas, namely Guqia, Toutai and Daxing. The industrial uranium orebodies are generally tabular and lenticular in shape. The buried depth of the top interface of the orebodies ranges from 206 to 407 m, and that of the bottom interface ranges from 209 to 412 m. The uranium orebodies in the Daxing area have the greatest buried depth, while those in the Guqia and Toutai areas are relatively shallowly buried. The uranium mineralization enrichment centers are obviously controlled by river channels, and industrial uranium mineralization is mainly hosted in the bottom channel lag and point bar microfacies. Combined with regional tectonics and hydrocarbon migration, sandstone-type uranium deposits in this area experienced two mineralization stages: supergene fluid mineralization and superimposed reworking by deep hydrocarbon-bearing reducing.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

5 valid minerals.

Rock Types Recorded