Geochemistry of Artificially Heated Humic and Sapropelic Sediments: Protokerogen: ABSTRACT

Abstract

Artificial heating experiments have provided information on the early diagenetic relation of classes of organic constituents in recent sapropelic and humic sediments. Lipids, humic acids, and kerogens isolated from heated Laguna Mormona algal mat and Staten Island peat have been studied by varied techniques including elemental element analysis, gas chromatography, programmed temperature pyrolysis, and stable isotope ratios. A temperature and time dependent set of constructive and destructive reactions plays a role in the quantity and quality of kerogen isolated from each heated sample. For humic kerogen the dominant constructive process is conversion of humic acid to new kerogen. The dominant constructive process for sapropelic kerogen is the grafting of lipids onto exist ng kerogen. Short-term, high-temperature laboratory simulations of burial maturation result in a dominance of destructive over constructive reactions. Part of the volatiles lost from sapropelic sediment during these experiments is isotopically light, hydrogen-rich lipids which might otherwise be grafted onto the kerogen during slow burial maturation. These results explain the common lack of agreement in evolution paths followed by laboratory-heated protokerogens and natural kerogens at progressively greater depths in cores. End_of_Article - Last_Page 763------------