Substitution pattern in perylenes and other polycyclic hydrocarbons of North Cambay Basin and their geochemical significance

摘要

Perylenes and substituted polyaromatic hydrocarbons (PAH) in the oils and sediments of North Cambay Basin were analysed to evaluate the nature of the source organic matter, deppsitional environment and time-temperature history. The studies reveal the predominance of terrestrial source organic matter in the entire Cambay Shale sequence. The redox conditions and the thermal history of these sediments control the relative distribution of perylene and other PAH compounds. These studies further indicate the existence of two different types of substitution patterns in PAH compounds, which are mainly governed by thermal stress in both younger (YCS) and older (OCS) subunits of Cambay Shale. In YCS sediments alkyl substitution seems to be responsible for formation of 2-methyl perylene, however, the occurrence of peri condensed perylene/ PAH compounds in these sediments indicates the possibility of formation of these compounds, either by aromatization of saturated ring structures or by one ring buildup mechanism. While in OCS aromatization seems to play major role in formation of peri-condensed perylene/PAH compounds.