Sedimentary Features and Uranium Metallogenic Conditions of the Sifangtai Formation in the West Slope of the Songliao Basin, China

摘要

Songliao Basin is a Meso-Cenozoic terrigenous oil-bearing basin stretchingin a NNE direction, with an area of about 26 × 104 km~2. Songliao Basin can bedivided into the following six first-order tectonic units, which form the basicframework of the basin’s geological structure: -- central depression -- western slope -- northern pitching -- north-eastern uplift -- south-eastern uplift-- south-western uplift area. The west slope is situated in the northern Songliao Basin and is a secondarystructure unit of this area. Based on geological, well logging, seismic andother data on the west slope of the Songliao Basin, the Sifangtai Formationis widely distributed in the northern Songliao Basin. It is moderately buriedand its sedimentary system consists mainly of fluvial plain, braided river anddelta. It has a stable mud-sandstone-mud sequence structure and a stablethickness of sand bodies. The humid to semi-humid palaeoclimate in the sedimentation epoch of the Sifangtai Formation favoured the formation ofuranium rich strata. It is the key target layer in the west slope of the SongliaoBasin. The author emphasises that the delta facies and braided streamfacies should be principal target facies. This research lays a foundation forthe following evaluation on the metallogenic prospect of a sandstone-typeuranium deposit in the west slope of the Songliao Basin.