المستخلص: |
Tricyclic terpanes to hopanes Ratios calculated from individual biomarkers to delineate their distribution, identifications, mixing ratios and biological precursor in a suite of crude oils (n = 24) from the East Sirt Basin. Geochemical application of Tricyclic terpane and Hopane biomarkers is divided studied oils into five groups (I, II, III, IV and V) based on the different ratios between Tricyclic terpanes to hopanes. Percentages of C23 Tricyclic terpanes/17α (H), 21β(H)-hopanes (C30αβ) and C28 Tricyclic terpane/17α (H), 21β (H)-30 hopanes (C31) have divided crude oils into 2 main individual groups in addition to 3 mixed groups. Group I, characterized by the dominance and extension of the tricycle terpane series (≈ C45 Tricyclic terpane). Group V, distinguished with the dominance of 17α (H), 21β (H) hopanes series. Groups II, contained a domination Tricyclic terpanes and hopanes, considered as a mixed group. The group III demonstrated equivalent ratios of Tricyclic terpanes to hopanes. The Group IV revealed a reduced amount of Tricyclic terpanes with enrich of hopanes. Tricyclic terpanes derived from tricyclohexaprenol precursors and attributed to a marine depositional environment and algal matter. Hopanes in obtained from bacteriohopane polyols and aminopolyols and distinguished to a depositional bacterial environment.
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