Vergleichende mineralogische Untersuchungen an zwei tunesischen Phosphorit-Vorkommen
Abstract:The paper compares the mineralogy and fabric of two Tunisian phosphorite deposits, which have been formed during the late Palaeocene and early Eocene as part of the large, 6000 km long “North African Phosphorite Belt”. The deposits Kefschwaier (Metlaoui Region) and Sra Ouertane are situated south resp. north of the Tertiary “Ile de Kasserine”. While the southern deposit Kefschwaier is characterised by several metastable and weak mineral phases (additional to francolite, calcite, quartz and some “normal” clay minerals like illite and kaolinite), e.g. opal- CT, chalcedony, (Cu-) Fe-sulfides and Mg-silicates (palygorskite, sepiolite), these minerals are absent in Sra Ouertane. There, the former francolite oöids are deformed and the fossil relics are mainly broken and recrystallised, and several authigenic minerals (e.g. Fe-dolomite, albite, K-feldspar, montmorillonite) have been newly formed. The observed differences in mineralogy and fabric are interpreted as caused by the influence of low-grade regional metamorphism which has occurred during the orogenesis of the nearby Atlas mountains and the associated processes of salt diapirism in the Atlas foreland.
Document Type: Research Article
Affiliations: Institut für Mineralogie und Geochemie, Universität Karlsruhe, Deutschland
Publication date: September 1, 2003