Master Thesis Geochemical Evaluation of the BirTlacsin Formation at Ghat Area Murzuq Basin, SW Libya.

Abstract

The objective of the present study is the geochemical assessment of the Bir Tlacsin Formation at Ghat area, SW Libya. This assessment includes the depositional environment, paleo-oxygenation, paleoclimate, paleosalinity, provenance, tectonic setting, organic matter richness, kerogen type and thermal maturity. The field trips included five surface sections for the formation (Wadi Maghidat, Wadi Tashat, Wadi Anlakm, Wadi Iggiten, and Wadi Awzarq). This formation consists of sandstone and shale units. The sandstones are mainly greywackes. The observed clay minerals in the studied shales are smectite, kaolinite, gibbsite and chlorite. These minerals are the main carrier of TOC. The Th/Cr, Th/Sc and Th/Co ratios and the provenance discrimination diagrams indicated that the felsic (granitic) rocks found in the Air Mountains, central Niger, may be the possible source of the Bir Tlacsin Formation. Based on the ICV values, the shales are thermally immature whereas the sandstones are thermally submature to mature. Moreover, the organic geochemical data showed that the organic matter are thermally immature. The organic matter are essentially of marine origin. The Zr/Hf, Hf/Ta, Zr/Ta and B/Ga ratios indicated that the Bir Tlacsin Formation was deposited in a high salinity marine environment. Based on the trace element, Pr/Ph, Pr/n- C17 and Ph/n-C18 ratios the anoxic conditions were prevalent during deposition. The paleoclimate prevailing in the source area was almost semi-arid to semi-humid. The tectonic environment is essentially continental (active continental margin (C) and passive continental margin (D)). Generally, the shales are good source rocks. The discrimination diagrams showed that kerogen type II is the basic type in the shale samples. The hydrocarbons are mainly migrated (nonindigenous).