New evidences of hydrothermal fluids circulation at the Devonian Kess Kess mounds, Hamar Laghdad (eastern Anti-Atlas, Morocco)

Fulvio Franchi, Barbara Cavalazzi, Catherine Pierre, Roberto Barbieri

    Research output: Contribution to journalArticle

    13 Citations (Scopus)

    Abstract

    New evidences based on a combination of field and laboratory investigations reinforce the hypotheses that the circulation of warm fluids has remarkably contributed to the origin and development of the Devonian Kess Kess mounds of the Hamar Laghdad Ridge (eastern Anti-Atlas, Morocco). The limestones of the Hamar Laghdad Ridge were deposited above a structural high generated by calc-alkaline volcanic activity that has probably fuelled the circulation of warm fluids throughout the overlying carbonate units. The geological and palaeontological attributes described throughout the succession of the Hamar Laghdad Ridge (from the Lochkovian to Frasnian intervals) are interpreted as the result of hydrothermal processes related to a volcanic system. In particular, these attributes seem consistent with a chemo-physical environment fuelled by the circulation of warm and late magmatic fluids. These attributes include a very low oxygen stable isotope signature (δ18Õ-10‰) for carbonates. Evidences for a late magmatic fluid circulation consist of volcanic glass and pyroclasts replacement with hydrothermal minerals such as quartz, anatase and clinochlore. Fluids circulating through veins and pores into sediments, and venting to the seafloor, probably induced the formation of cavities where monospecific trilobite communities were detected. The partially silicified trilobite remains are associated with traces of goethite. This iron-bearing oxide mineral is also present in the upper part of the Hamar Laghdad Ridge. All these attributes are here interpreted as possible evidences for a low-temperature hydrothermal venting system active during the Lochkovian-Frasnian time span. This study combines an updated revision with new petrographic, geological and geochemical results aimed at providing an overall framework on the origin and early diagenesis of the Devonian succession of Hamar Laghdad.

    Original languageEnglish
    Pages (from-to)634-650
    Number of pages17
    JournalGeological Journal
    Volume50
    Issue number5
    DOIs
    Publication statusPublished - Sep 1 2015

    Fingerprint

    hydrothermal fluid
    atlas
    fluid
    Lochkovian
    Frasnian
    venting
    trilobite
    clinochlore
    carbonate
    volcanic glass
    anatase
    mineral
    goethite
    diagenesis
    oxygen isotope
    cavity
    stable isotope
    seafloor
    replacement
    limestone

    All Science Journal Classification (ASJC) codes

    • Geology

    Cite this

    Franchi, Fulvio ; Cavalazzi, Barbara ; Pierre, Catherine ; Barbieri, Roberto. / New evidences of hydrothermal fluids circulation at the Devonian Kess Kess mounds, Hamar Laghdad (eastern Anti-Atlas, Morocco). In: Geological Journal. 2015 ; Vol. 50, No. 5. pp. 634-650.
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    abstract = "New evidences based on a combination of field and laboratory investigations reinforce the hypotheses that the circulation of warm fluids has remarkably contributed to the origin and development of the Devonian Kess Kess mounds of the Hamar Laghdad Ridge (eastern Anti-Atlas, Morocco). The limestones of the Hamar Laghdad Ridge were deposited above a structural high generated by calc-alkaline volcanic activity that has probably fuelled the circulation of warm fluids throughout the overlying carbonate units. The geological and palaeontological attributes described throughout the succession of the Hamar Laghdad Ridge (from the Lochkovian to Frasnian intervals) are interpreted as the result of hydrothermal processes related to a volcanic system. In particular, these attributes seem consistent with a chemo-physical environment fuelled by the circulation of warm and late magmatic fluids. These attributes include a very low oxygen stable isotope signature (δ18{\~O}-10‰) for carbonates. Evidences for a late magmatic fluid circulation consist of volcanic glass and pyroclasts replacement with hydrothermal minerals such as quartz, anatase and clinochlore. Fluids circulating through veins and pores into sediments, and venting to the seafloor, probably induced the formation of cavities where monospecific trilobite communities were detected. The partially silicified trilobite remains are associated with traces of goethite. This iron-bearing oxide mineral is also present in the upper part of the Hamar Laghdad Ridge. All these attributes are here interpreted as possible evidences for a low-temperature hydrothermal venting system active during the Lochkovian-Frasnian time span. This study combines an updated revision with new petrographic, geological and geochemical results aimed at providing an overall framework on the origin and early diagenesis of the Devonian succession of Hamar Laghdad.",
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    New evidences of hydrothermal fluids circulation at the Devonian Kess Kess mounds, Hamar Laghdad (eastern Anti-Atlas, Morocco). / Franchi, Fulvio; Cavalazzi, Barbara; Pierre, Catherine; Barbieri, Roberto.

    In: Geological Journal, Vol. 50, No. 5, 01.09.2015, p. 634-650.

    Research output: Contribution to journalArticle

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