Title: Sequence stratigraphy of the Upper Cretaceous and its relation to sandstone-type uranium mineralization in the southwest of Songliao Basin
Abstract: The Upper Cretaceous of the southwest of Songliao Basin is featured with fluvial,delta and lacustrine depositional systems in a large scale.The rocks are mainly composed of aubergine with mixed gray sandstone,siltstone and mudstone.The Upper Cretaceous in the area can be classified as 7 depositional sequences which can also be classified as 4 super-sequences.The formation of sequence and its internal system tracts is controlled by the relative lake-level change,of which the second class change controls the formation of super-sequence and development of large-scale sand bodies,and the third class change controls the formation of depositional sequence and the sand bodies distribution and their geometry and physical property.While the palaeo-climatical change affects the fabric and material composition of the rocks.The uranium mineralization in the area is mainly controlled by the sequence,depositional system and the physical and chemical properties of the sand bodies.The uranium bodies mainly occur in the thick and large sand bodies of the lower part of a super-sequence which are all older than the Nenjiang Formation.This kind of mineralization is closely related to the transgressive system tract of a depositional sequence,in which the delta sand bodies are the best host rocks.As the epigenetic alteration widely goes on,the enrichment of uranium takes place by the absorption of clay and co-precipitation of pyrite and pitchblende.
Publication Year: 2007
Publication Date: 2007-01-01
Language: en
Type: article
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