EVOLUTION OF ORGANIC MATTER AND ORIGIN OF SEDIMENTARY DEPOSITS(II)——HYDROCARBONS ORIGINATING FROM COAL AND STRATA-BOUND DEPOSITS

According to the domestic and foreign data and experimental results obtained from analysis,brief discussion have been gir-en on the amount and characteristics of gas and liquid hydrocarbons produced by organic m atter of coal-bearing strata during the different stages of coal formation,as well as the effect of macerals upon nature and composition of the products.In differentiation from hydrocarbons produced by source rocks, the liquid hydrocarbons originating from coal are composed of special oils,such as high war oil and lour mature light oil, especially the Latter does not erist in hydrocarbon originating from oil.The oil formation threshuld depth of high war oil is usually deeper than,but the threshold depth of low mature oil is shallower than that of typical sapropelic source rocks. All these characters are controlled by the nature and composition of macerals.Large amount of light oil rich in terpanes is produced from Fushun resins of low maturity in heating eyperiments. A scheme diagram of evolutionary stages of coal gas has been proposed.The relationships between pairs as reformation process and evolution of petroleum,metallic source strata and source rocks, host rock strata and reservoir rocks,migration of metallic elements and that of petroleum have been discussed in terms of grimary study of organic matter and lots of asphalts associated with some strata-bound ore deposits, as well as two eacamples of strata-bound ores.Solid asphalts can be divided into syngenetic-diagenetic asphalts,epigenetic (reformational) asphalts and hypergenetic asphalts.Epigenetic asphalts are also called reservoir (thermal metamorphosed) asphalts,representing one of the two thermal metamorphosed end products of oils within reservoirs.The significance of the study on origin of paleo-oil traps (thermal cracking methane gas field)and certain strata-bound ores has been discussed briefly. It has been proposed to predict the intensity and history of reformation process of strata-bound ores by the study of nature,composition and evolutionary- stage of organic matter and different kinds of asphalt in the ore deposits.