Research On Distribution And Mineralizing Mechanism Of Oil Shale In Minhe Basin

Minhe Basin is a inter-mount fault depression basin,which located in the east part of Qilian mountain fold Series(Caledonian geosyncline)and is the continental coaly and petroliferous basin developed during the Mesozic. Basement of the basin mainly consists of the Pre-Cambrian metamorphic rocks and the granites of the Caledonian fold Series . The sedimentary cover of the basin is made up of Jurassic system , Cretaceous system, Paleogene System and Neogene System. According to the study in this article and previous data, Jurassic system,which is a set of dark coal-bearing and oil shale clastic rocks sedimentary system,is a sequence of fluvial facies ,swamp facies and lacustrine facies,and is considered as the only fairly good coal-forming and oil-forming rocks series in Minhe basin at present.Minhe basin can be divided into four first-order tectonic units extending from NE towards SW, including successively Gaolan uplift,Yongdeng fault depression, Zhoujiatai low uplift and Bazhou fault depression from north towards south. There are much nomal faults and converse faults in the basin, the strike of which mostly are extending along NE and approximately EW. These faults are distributed along the edge of basin and inside. They control not only the formation and evolution of basin but also the local structures to some extent. The formation and evolution of basin went through four stages, including the fault depression prophase of uplift stage of the Triassic period, the fault subsidence stage of the Jurassic period-Early Cretaceous period (mainly development period of the basin), the depression stage of the Late Cretaceous period-Neogene Period, the subduction of the basin of the Pleistocene.According to data of research region and study degree in the basin , on the basis of core, outcrop and testing analysis indoor data etc. , the author analyzing sedimentary feature and sequence stratigraphy feature of the basin ,using sedimentology and sequence stratigraphy as chief study method, integrating palaeontology, geochemistry, mineralogy and so on as auxiliary study method. Studied result indicate that Minhe basin went through three sedimentary stages in the Jurassic: 1) Fault subsidence type rapid filling sedimentation in Early Jurassic period; 2) Fault lacustrine basin sedimentation in Middle Jurassic period; 3)...