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    Pb-Zn mineralization in a Miocene regional extensional context: The case of the Sidi Driss and the Douahria ore deposits (Nefza mining district, northern Tunisia).

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    Authors
    Decrée, S.
    Marignac, Ch.
    De Putter, Th.
    Deloule, E.
    Liégeois, J.-P.
    Demaiffe, D.
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    Discipline
    Earth and related Environmental sciences
    Subject
    Geodynamics and mineral resources
    Audience
    Scientific
    Date
    2008
    Publisher
    Elsevier
    Metadata
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    Description
    The Sidi Driss and Douahria sulfide ore deposits and showings are located in the Nefza mining district, northern Tunisia. The ores are hosted within Upper Miocene (Messinian) basins, within carbonate lenses composed of Fe Mn-enriched dedolomite partially or totally replaced by early barite and celestite. The ore mainly consists of galena and spherulitic/colloform sphalerite (partially replaced by later Fe-sulfides). It is present as disseminated or banded ores and has been deposited within the host-rock through dissolution/replacement process or through void infilling. The remaining voids are filled by late calcite/barite locally associated with a late oxidation event. In situ ion microprobe sulfur isotope analyses show significant variability for sphalerite (from − 43.9 to 1.2 ), galena (from − 30.3 to − 2 ) and marcasite ä34S (from − 35.9 to 25.8 ). These values are interpreted as the result of (i) the mixing of two sulfur end-members in the mineralizing fluids, corresponding to different reduction processes (bacterially-mediated sulfate reduction and thermochemical sulfate reduction, with early celestite and barite and/or contemporaneous Messinian seawater, together with Triassic sulfate, as sulfur sources, and (ii) Rayleigh fractionation process in a closed system. Several arguments (Fe Mn enrichment in early diagenetic carbonates, involvement of Messinian seawater as a sulfur source, low temperature of deposition and soft-style sedimentary figures within sulfides) suggest that the Sidi Driss and Douahria Pb Zn ore deposits are syn-diagenetic. Moreover, the properties of the ore deposits, with Fe Mn carbonates having a wider distribution than that of the base metal sulfides, and the characteristics of the mineralization, in which diagenetic sulfates are a sulfur source and Cd enrichment in sphalerite, support the classification of the Sidi Driss and Douahria Pb Zn deposits as SHMS-Sedex type. Late Miocene extension, comprising rifting dynamics and basalt emplacement, favored a thermally-driven fluid circulation origin for the Sidi Driss and Douahria deposits, enhancing inception of small-scale shallow convection cells. Such sulfide emplacement is significantly different from that of southernmost MVT ore deposits of Tunisia, which are associated with diapirs and are interpreted as the result of a Serravalian Tortonian gravity-driven fluid circulation event related to late Alpine convergence.
    Citation
    Decrée, S.; Marignac, Ch.; De Putter, Th.; Deloule, E.; Liégeois, J.-P.; Demaiffe, D. (2008). Pb-Zn mineralization in a Miocene regional extensional context: The case of the Sidi Driss and the Douahria ore deposits (Nefza mining district, northern Tunisia).. , Ore Geology Reviews, Vol. 34, 285-303, Elsevier, DOI: 10.1016/j.oregeorev.2008.01.002.
    Identifiers
    uri: https://orfeo.belnet.be/handle/internal/189
    doi: http://dx.doi.org/10.1016/j.oregeorev.2008.01.002
    Type
    Article
    Peer-Review
    Yes
    Language
    eng
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