Abstract: Dawsonite of Mesozoic strata in Northeast China and adjacent area distribute in Lower Cretaceous strata from Hailaer basin,Tamtsag basin, Erlian basin, Kailu basin and Fuxin basin, and Upper part of Lower Cretaceous and Lower part of Upper Cretaceous from southern Songliao basin. Optical microscope, scanning electron microscope and X-ray diffraction analysis have revealed that dawsonite mainly occur in the feldspar-rich sandstone and pyroclastic rocks, either as cements filling inter-grain pores as radical, bunchy, rosette, intricately trichoid, and platy collectives, or as replacement of feldspar and lithic grains with bunchy and paty shapes. More and more evidences suggest that dawsonite is a indicative mineral of CO₂rich fluids and record CO₂ and petroleum dual infilling. The infilling time of CO₂ and variation of partical pressure of CO₂ during infilling process can be determined from dawsonite-bearing clastic rocks.

Key words: dawsonite, distribution, occurrence, petroleum significance, Northeastern China and adjacent area