Fredj Chaabani

Aptian sedimentation: an example of interaction between tectonics and eustatics in Central Tunisia

Abstract To reconstruct the sequence evolution and distribution of deposits during the Aptian in the Central Tunisian platform, the present study was mainly based on a sedimentological approach. The palaeogeographical reconstruction shows an inner and an external platform separated by the highs of the Central Tunisian islands. These are characterized by carbonate-dominated deposits evolving towards the north into a pelagic marl-dominated sedimentation. The NW-SE-to east-west-directed faults show an important sedimentary control. In fact, a system of tilted blocks located towards the SW characterizes a large part of the platform. The subsidence evolution during the Aptian was marked by a recovery of extensional tectonics. Finally, some halokinetic vertical movements were responsible for several highs during the latest Barremian. The Central Tunisian platform evolution was controlled by drift of the African platform during the opening of the Atlantic Ocean.

Atmospheric dust deposition on soils around an abandoned fluorite mine (Hammam Zriba, NE Tunisia).

Abstract The present study focuses on the eolian dispersion and dust deposition, of major and trace elements in soils in a semi‐arid climate, around an old fluorite (CaF2) and barite (BaSO4) mine, located in Hammam Zriba in Northern Tunisia. Ore deposits from this site contain a high amount of metal sulphides constituting heavy metal pollution in the surrounding environment. Samples of waste from the surface of mine tailings and agricultural topsoil samples in the vicinity of the mine were collected. The soil samples and a control sample from unpolluted area, were taken in the direction of prevailing northwest and west winds. Chemical analysis of these solids was performed using both X‐ray fluorescence and X‐ray diffraction. To determine the transfer from mine wastes to the soils, soluble fraction was performed by inductively coupled plasma and ionic chromatography. The fine grained size fraction of the un‐restored tailings, still contained significant levels of barium, strontium, sulphur, fluorine, zinc and lead with mean percentages (wt%) of 30 (calculated as BaO), 13 (as SrO), 10 (as SO3), 4 (F), 2 (Zn) and 1.2 (Pb). Also, high concentrations of cadmium (Cd), arsenic (As) and mercury (Hg) were found with an averages of 36, 24 and 1.2 mg kg−1, respectively. As a result of the eolian erosion of the tailings and their subsequent wind transport, the concentrations of Ba, Sr, S, F, Zn and Pb were extremely high in the soils near to the tailings dumps, with 5%, 4%, 7%, 1%, 0.8% and 0.2%, respectively. Concentration of major pollutants decreases with distance, but they were high even in the farthest samples. Same spatial distribution was observed for Cd, As and Hg. While, the other elements follow different spatial patterns. The leaching test revealed that most elements in the mining wastes, except for the anions, had a low solubility despite their high bulk concentrations. According the 2003/33/CE Decision Threshold, some of these tailings samples were considered as hazardous. Furthermore, other waste samples, considered non hazardous, were not inert. In contrast, the SO42‐, Ba, Pb and Sb leachable contents measured in most of the soil samples were relatively high, exceeding the inert threshold for landfill disposal of wastes. Graphical abstract Figure. No Caption available. HighlightsTailings dumps and associated windblown materials contain high contaminants load.Eolian dust arising from dumps dispersed pollutants and contaminated soils.Contents of mining‐related elements exceeded allowable concentrations by guideline.The majority of harmful pollutants, except anions, have low leachable potential.