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Aridic crusts and vein mineralisations in the playa Areg el Makrzene, South Tunisia |
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| Authors: | Roman Fromm Tarek Hachicha Werner Smykatz-Kloss |
| Institution: | aInstitut für Mineralogie und Geochemie der Universität (T.H.), D-76128 Karlsruhe, Germany bEcole Superieure d’Horticulture, Chott Meriam, Sousse, Tunisia |
| Abstract: | The playa Areg el Makrzene is situated in the north of the escarpment of the Djebel Rehach in southern Tunisia. It is characterised by more than 70 spring mounds which are bound to faults in the Triassic sandstone, and by (sub-) recent calcareous and iron hydroxide precipitations. The artesian spring water contains high amounts of Na+, Ca2+, Mg2+ and Cl?, SO42?, and HCO3, shows slightly alkaline character and a temperature of 25 °C. The spring mounds consist of porous travertine (calcite), goethite, gypsum and of Na–Mg evaporites and are up to 10 m high. Few metres away from the springs the amorphous iron hydroxides have altered to badly ordered goethite and ferrihydrite and finally to well ordered goethite. The muddy precipitate has altered to hard crusts (calcrete, ferricrete). The source of the precipitated material is discussed. The faults in the sandstone are filled with (hydr-)oxides of iron and manganese, e.g. with goethite, hollandite and pyrolusite. The amount of Mn-oxides may reach 60 mass%. |
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