To study the occurrence of absorbed organic matter in clay minerals

the bounding of organic matter and clay minerals

and thermostability of the organic matter

we took samples from the argillaceous hydrocarbon source rocks of the Neocene Shahejie Formation in Jiyang Depression and from mud on surface of the East China Sea continental shelf.Clay components (<2 μm) were obtained from theses samples for sequential treatments including soxhlet extract

base hydrolysis and acid hydrolysis.The original clay samples and their absorbed organic matters as well as that obtained during base hydrolysis and acid hydrolysis were compared in respects of microscopic shape (SEM)

specific surface area (BET)

X-ray diffraction (XRD) and thermal gravity/differential thermal gravity (TG/DTG).Results show that extracted organic matter mainly occurs on the outer surface and in micro-pores of clay minerals

base hydrolysed organic matter can be found near broken bound on margin of clay minerals

and acid hydrolayse organic matter mainly occurs in inter-layers of expandable smectite in clay minerals.The former is free organic matters with physical adsorption or bound and the latter two are the combined organic matter with chemisorption.The various associative relations between the organic matter and clay minerals caused difference in their thermostability and further affected the hydrocarbon generation in the area.A study on the absolute and relative contents of organic matters with various occurrences is therefore considered significant for understanding the hydrocarbon origin and its primary migration.