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Influence of the diagenetic water medium on the hydrogen isotope of sedimentary N-alkanes

The hydrogen isotopic composition of sedimentary n-alkanes can be used to study paleoclimate, organic matter sources and petroleum genesis. However, the hydrogen isotopic composition of sedimentary n-alkanes is affected by many factors, and studying them is mainly involves the isotopic fractionation relationship between the hydrogen isotopes of sedimentary n-alkanes and the rainwater in the study area.

At present, there are only a few studies reported on the relationship between sedimentary n-alkanes and thermal maturity. Besides, the extent of the influence of various diagenetic water media on the hydrogen isotopic composition of sedimentary n-alkanes at different evolution stages is still unclear.

In order to understand the influence of the diagenetic water medium on the hydrogen isotope of sedimentary n-alkanes, scientists from the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences carried out thermal simulation experiments involving the initial peat under the addition of alkaline saltwater, acidic freshwater and peat alone condition.

They analyzed the generated n-alkanes in terms of molecule composition and hydrogen isotopic composition of individual n-alkanes, and they found that the n-alkanes displayed significant heavier hydrogen isotopic composition from the alkaline saltwater added experiments, but obvious lighter hydrogen isotopic composition from the acidic freshwater added experiments.

This study provides information to understand of the genesis of sedimentary n-alkanes formed under the participation of diverse diagenetic water media at various stages of maturity.

This study has been published in the Fuel in an article entitled "Experimental simulation study on the influence of diagenetic water medium on sedimentary n-alkanes and their respective hydrogen isotopes".