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Titre : Geology and potentiality of basalts in Jabal Eghei area (Libya)

Geologija i potencijalnost bazalta područja Jabal Eghei (Libija)

Auteur : Abusahmin, Faisal

Université de soutenance  : University of Belgrade

Grade : Doctoral Dissertation 2020

Résumé
Basalts cover most of the Jabal Eghei area and are part of the Tibesti volcanic province. These are stratified basalts, covering Proterozoic metamorphites and granites and lithologically different rocks of Tertiary age. Basalts were formed during three separate phases of volcanic activity between 12 and 8 Ma (Phase I), 7- 4 Ma (Phase II) and less than 4 Ma (Phase III). The most abundant minerals in basalts are olivine, clinopyroxene and plagioclase, while the minor minerals are from the spinel group (magnetite ± ilmenite) and volcanic glass residues. In the basalts of the third volcanic phase, the presence of analcimitised leucite, analcime and rhoenite was detected, which has not been proven in the studied area so far. The predominant textures are porphyric and ophitic, while the structures are massive and vesicular. The physico-mechanical properties of basalt are within the expected limits, and from a geomechanical point of view, the tested basalts are quite homogeneous. From the results of these studies and tests by ultrasonic method, it can be concluded that the basalts of porphyric texture and massive structure exhibit the best properties in terms of stone quality as a rock mass. Basalt powder as a filler has been tested for the possibility of preparing a composite material suitable for cavitation exposure, and the results show that a hybrid composite material consisting of basalt powder and alumina particles has improved cavitation resistance over a pure matrix and a micro composite consisting of basalt powder and matrix material. This material has also very good aesthetic and abrasion-resistant properties. In the assessment of potentiality, three ore formations were identified, comprising basalts of all three volcanic phases. In terms of overall potential, the Jabal Eghei area is a high potential area for the discovery, exploration and definition of future basalt deposits as ore formations of large extent and of good qualitative characteristics, whether as building stone, basalt fiber raw materials and composite materials.

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