A Preliminary Study On Tuffaceous Source Rocks Of Pingdiquan Formation In Huoshaoshan Region,Junggar Basin

The source rocks of Permian Pingdiquan formation in Huoshaoshan Region, Junggar basin is composed of volcanic material and terrigenous clastic. Deposits of Volcanic ash reflect a important sedimentary and tectnic events, which play a profound role to the source rocks of Pingdiquan formation. This paper systematically study on the ptrological, geochemical, organic geochemistry and bio marker, to exploring the capacity and mechanism of hydrocarbon generation of Pingdiquan formation.The high content of gammacerane, predomination of phytane and the detection of ?-carrotanes, show that Pingdiquan formation was formed in semi-saline water of deep lake anoxic environments.The source rock of Pingdiquan formation mainly consist of tuffaceous shale and tuffites. Geochemical component show that the parent rock is acidic rocks and mafic magmatic rocks, and the mafic composition comes from the volcanic activity.Organic geochemical data show that the source rocks of Pingdiquan formation contain high organic matterials abundance, but the heterogeneity of organic matterials abundance in different third tectonic units is severe. Overall, Huoshaoshan anticline and Huonan anticline has higher organic matterials abundance than Huodong syncline and Huobei fault The source rocks of Pingdiquan formation dominated by kerogen type ?.Tmax, vitrinite reflectance and bio marker maturity indicators indicate that source rocks of Pingdiquan formation are mainly during the low-mature and mature stage, Huodong syncline and Huobei fault has higher thermal evolution stage than Huoshaoshan anticline.The distribution of nalkanes with light carbon predominance of show that organic matterials mainly derived from aquatic bacteria algae,but all the sample have a higher content of C29 steranes(35.25%?46.91%) than C27 steranes(9.63%?27.49%), some researches show that C29 steranes derived from cyanobacteria or terrigenous higher plants, so we think that the C29 steranes in Pingdiquan formation mainly derived from cyanobacteria. Volcanic ash provide the nutrient, thriving the aquatic organisms, and volcanic ash would cause the earlier hydrocarbon generation of source rocks, with the catalytic process of transitive metal and heating of organic matterials. Moreover, tuffites isolate the organic matterials from the fluid, providing the favourable condition for the preservation of organic materrials.