Provenance Analysis Of Jurassic Dameigou Formation In Dameigou Area,northern Margin Of Qaidam Basin

Jurassic Dameigou Formation in Northern margin of Qaidam Basin has a great potential for oil and gas exploitation,so it will be of great signiforcance for guiding the oil and gas exploration to have an in-depth study in provenance and distribution of sedimentary facies.Based on digesting the research result of predecessors,combined comprehensive analysis of field geological of outcrops,observation and description of geological profile,and geochemical analysis of sample,the characteristics of Sedimentary and source of Dameigou Formation in North of Qaidam Basin were discussed.It revealed the sedimentary facies and facies distribution pattern of Dameigou Formation and confiemed the source direction,tectonic setting and the nature of source rock.The Dameigou Formation developed a set of continental clastic rocks in the study area,which is divided into eight parts from bottom to top,in which conglomerate and sandstone are relatively developed.The conglomerate which is mainly gray is medium to thick layer with complex gravel,mainly sedimentary rock,quartzite,granite and so on.The sandstone type is mainly feldspar quartz sandstone,feldspar sandstone,lithic quartz sandstone and lithic sandstone.The granularity analysis of the sandstone of Dameigou Formation shows that the grain size of the sandstone is coarse and the medium coarse grain is dominant;the sorting is medium and good;the skewness focus on positive skewness.The cumulative probability curve is mainly two stages;the C-M diagram shows that the sample falls within the range of the traction flow.The study of petrological characteristics,sedimentary texture and structure of the Jurassic Dameigou formation in the study area shows that the Dameigou formation of sedimentary facies types include braided river delta facies,fan delta facies and lacustrine facies.The Dameigou formation has experienced the early Jurassic rift basin and the Middle Jurassic lake basin expansion period after the initial rifting.The comprehensive analysis of heavy mineral and paleoflow suggest that the main source of the first to fourth sections of the Dameigou formation is mainly from the western of the Zongwulong Mountain and the parent rock was mainly acidic magmatic and sedimentary rocks,containing a small amount of Metamorphic rocks.The analysis of Geochemistry indicates that the tectonic setting of the source area is mainly on the passive continental margin and the active continental margin,and the type of source rock is felsic rocks from the UCC,which is mainly clastic rock from Carboniferous zongwulong group of western of Zongwulong Mountain and mixed monzonitic granite and metamorphic rock from Late Ordovician of Qaidam Mountain.