Aenigmetites from the Ilímaussaq intrusion, south Greenland: Chemistry and petrological implications

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    Abstrakt

    Aenigmatite in the Ilímaussaq intrusion shows a variety of textural relations to the other mafic minerals and an unusual range in chemical compositions. The saturated and oversaturated rocks contain zoned aenigmatities with Ca, Al, Fe2+-rich cores coexisting with katophorite, and near-ideal Ti-aenigmatite rims coexisting with arfvedsonite and aegirine. The aenigmatite substitutions are outlined, and the varying chemistry discussed. A no-oxide field seems to have existed in the (log fO2, T) space for the undersaturated magma, and an arfvedsonite-aenigmatite oxygen buffer equilibrium is suggested for the coexisting Fe3+-rich aenigmatite and katophorite. This buffer was later invalidated by the stabilisation of aegirine, whereby the Fe3+-aenigmatite component broke down, causing extensive recrystallisation into near-ideal Ti-aenigmatite.

    OriginalsprogEngelsk
    Sider (fra-til)257-270
    Antal sider14
    TidsskriftLithos
    Vol/bind10
    Udgave nummer4
    DOI
    StatusUdgivet - 15 okt. 1977

    Programområde

    • Programområde 4: Mineralske råstoffer

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