Reaserch On Conditions Of Organic Matter Accumulation Of Rich Oil Shale Of Dalazi Formation, Lower Cretaceous, Luozigou Basin

The study area locates in Luozigou Basin which belongs to a compound synclinebasin that lies in Yanbian eugeosyncline fold zone, Jihei Fold System.The aimstratum is the oil shale bearing beds, Dalazi Fromation, Lower Cretaceous, anddevelops several industrially valuable oil shale beds.Up to now, research on thisbasin’s oil shale remains very low degree.Therefore, not only development andutilization but also the theoretical research of the oil shale, need to investigate theconditions of organic matter accumulation of rich oil shale of this basin.Based on the previous collection of the fundamental correlative geological data,the detailed geological survey is accomplished, including the observation andmeasurement of the field outcrop and trial trench, and the systemicsampling.Subsequently, the indoor work which be composed of mapping of outcropand other correlative contents and testing analysis of the samples including thinsection, trace elements, rare earth elements, X-ray diffractive, total organic carboncontent, sulfur content, rock pyrolysis, GC, GC-MS and the maceral composition ofthe muddy stones of the study area are completed.According to the foresaid data and analysis, the relationship between theaccumulation of rich oil shale and the characteristics of sedimentaryfacies,paleo-water and paleo-climate, respectively, is found out, and also the keyfactors which conrol accumulation of the organic matter of the whole sedimentarybasin.There are four types of sedimentary facies recognized in this basin, includingalluvial fan, nearshore subaqueous fan, fan delta and lacustrine, further composed of 11types of subfacies and15types of micro faices.The rich oil shale developes in thesemi-deep and deep lake facies, and interbeded by shore-shallow lacustrine faciesstones, and no coarse grain-size stone found vertically, and the position locates nearthe depocenter of the basin.The prospect area of industrial valuable rich oil shale bedsare predicted acoording to the distribution characteristics of the mineable oil shalebeds of known areas.From aspects of paleo-water and paleo-climate, conclude that theorganic matter of the rich oil shale deposited in a fresh and highly reduced waterenvironment when the climate was warm and humid.And also the key factors thatcontrolled the accumulation of organic matter of the whole basin are foundout:Paleo-climate, the warmer and more humid of the climate, the higher content ofthe organic matter of the muddy stone;and sedimentary facies and deposition position,the semi-deep and deep lake facies and depocenter can benefit the accumulation of theorganic matter; the lesser is the stability of the tectonic and the contemporaneoussandy deposits nearshore, because sandy deposits would decrease the concentration ofthe organic matter.