Structural Pattern of Ghyrian Domes, Nafusa Uplift, Northwest Libya: Relation to Sirte Basin Rifting and Volcanic Activities

The origin of the Gharyan Domes, situated at the junction of the Nafusa Uplift with the Sirte Basin Rift (SBR) in the northwestern Libyan coastal margin, has remained contentious with debates differentiating between magmatic diapirism, related to Tertiary phonolitic intrusions along the SBR’s northwestern margin and Alpine-age dextral wrench tectonics forming the crustal fracture system of the SBR since Late Cretaceous. Neither model fully reconciles the geospatial-temporal interplay of domal structures, rift fault systems, and magmatism—a gap undermining full explanations of the tectonic evolution of the northern Libyan coastal margin. The present study resolves this paradox through a detailed field-based geological mapping of the Gharyan domes; the dip magnitudes and orientations of the folded surfaces and the patterns of the associated fracture systems demonstrate that these domes are typically composed of southwestward-plunging folds. Their asymmetries indicate that they verge southerly while their hinge-lines align in an en-echelon fold pattern that is bounded by two eastward-trending dextral marginal faults; a structural pattern incompatible with vertical magmatic diaprism models. The orthogonal alignment of the rift-parallel fractures of the SBR to the fold hinges, coupled with magmatic emplacement postdating fold evolutions, establishes a temporal-sequence of the Alpine-age transpressional wrenching that induced the primary fold architecture. Hence, the SBR and the magma migration to its western margin are subsequently localized wherever the stress-induced crustal dilation occurred.