Mineralogical and geochemical signatures of clays associated with rhyodacites in the Nefza area (northern Tunisia)

Abstract

Acid volcanic rocks underwent transformations subsequent to their emplacement. The transformations included ferruginations, silicifications and clayey alterations. The primary minerals were affected by hydrothermal and meteoric weathering. The nature of the clays is depends on the intensity of the transformations. Neoformed smectites are classified in the field of ferroan beidellites-nontronite. The geology of northern Tunisia is marked by magmatic extrusion that occurred during the Middle Miocene (Langhian-Lower Tortonian), which led to the outcrops of rhyodacites in the Nefza-Tabarka region. This event is contemporaneous with the Alpine compressional phase, which is well-characterised in the western Mediterranean area, where intense fracturing and hydrothermalism occurred with evidence of metallogenic consequences.In this paper, a detailed study is presented on the acid volcanic rocks that outcrop at the core of the Oued Belif structure in the Nefza area of northern Tunisia. The...