Comportement minéralogique et géochimique des formations géologiques de la région de Skikda, Nord Est Algérie (cas d’Azzaba).

Abstract

Our study area is located in the Numidian thrust slick, it is an uncomplicated geological domain; it is composed of two superimposed subunits, a first unit called sub-Numidian containing versicolored clays of reddish to purplish tints on which rests on a second unit called the Numidian unit which includes quarzitic sandstones with heterogeneous grains bound by a siliceous cement in the form metric beds alternating with greenish to reddish clay levels, the whole is surmounted by recent Quaternary formations. The aim of this work is to characterize the geological formations encountered from a lithological point of view as well as the determination of the chemical and mineralogical composition of the clays under Numidian. For this it was necessary to carry out field work and laboratory work. Fieldwork includes observation and sampling through geological formations in the Azzaba region. The clays were analyzed by various analytical techniques following international preparation protocols related to clays, namely: X-ray fluorescence (FRX), infrared spectroscopy (IR) and X-ray diffraction (XRD). The results obtained from mineralogical analyzes (XRD) evealed the major mineral phases entering into the composition of the clays studied (quartz, kaolinite, Smectite, illite, siderite, calcite) presenting varying contents from one site to another, associated with traces of hematite and siderite. Chemical analyzes of major elements show that the clays of the Azzaba region are mainly composed of silicon oxide (SiO2) and alumina (Al2O3) largely associated with iron hydroxide (Fe2O3) and alkalis (K2O) in high levels. Alkaline earths (CaO, MgO) have a relatively low content from a location to another.