Podrobnosti záznamu

Název
    GEOCHEMICAL AND MINERALOGICAL CONSTRAINTS ON THE GENESIS OF THE OTJOSONDU FERROMANGANESE DEPOSIT, NAMIBIA: HYDROTHERMAL EXHALATIVE VERSUS HYDROGENETIC (INCLUDING SNOWBALL-EARTH) ORIGINS
Autor
    Cabral, Alexandre
    Koubová, Magdaléna
    Mapani, Benjamin
    MOORE, J.
    SATTLER, C.-
Jazyk
    anglicky
Typ dokumentu
    článek v periodiku
Zdrojový dokument - seriál
    South African Journal of Geology
Svazek/č.
    Roč. 114, č. 1
Strany
    20
Rok
    2011
Výraz tezauru
    ferromanganese deposit, hematitic iron formation, trace element associations of Ag-As-Cu-Co-Bi-B-P-REE with Mn and Sr-Mo-W with Ba, hyalophane, spessartine, barite
Klíčové slovo
    CONSTRAINTS
    DEPOSIT
    EXHALATIVE
    FERROMANGANESE
    GENESIS
    GEOCHEMICAL
    HYDROGENETIC
    HYDROTHERMAL
    INCLUDING
    MINERALOGICAL
    NAMIBIA
    ORIGINS
    OTJOSONDU
    SNOWBALL-EARTH
Abstrakt (anglicky)
   The Otjosondu ferromanganese deposit is located in a condensed stratigraphic sequence that indicates a basin-margin setting on the northern flank of the Khomas Trough. Association with the Chuos Formation of the Damara Sequence is equivocal as only sediments atypical of this formation are present. Three rock types, hematitic itabirite, braunite-rich gondite and coticule (spessartine-quartz rock), dominate the succession. Barite is a major component of some gonditic ores, whereas barite and hyalophane form important minor constituents of all rock types. Two broad metal associations are present in the ferromanganese rocks (gondite and coticule): Mn-Fe-Ag-As-P-Cu-Co-Bi-B and Ba-Sr-Mo-W-Ni. The three rock types, gondite, coticule and itabirite, represent variable mixtures of hydrothermal and detrital components. Values of barite ?34S are inversely correlated with whole-rock Fe contents and indicate mixing of hydrothermal and sea-water S sources. Cerium anomalies implicate oxic oceanic con
   ditions during deposition of the ferromanganese formations. The Otjosondu ferromanganese deposit is comparable to distal oxidised sediment-hosted exhalative deposits. It may loosely be related to the Rosh Pinah and Tsongoari deposits that occur in roughly similar stratigraphic positions towards the base of the Damara Sequence. The highly oxidised, sulfate-rich nature of the Otjosondu deposit, as opposed to the deep-water, anoxic, sulfate-poor conditions required for the development of glacially associated iron and manganese formations, argues against an association with a snowball-Earth episode.
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (RIV)
Zdrojový formát
    R
Datum importu
    15. 10. 2014