Fenitization of some mafic igneous rocks in the Seiland province, northern Norway

Against alkaline pyroxenite dykes, metamorphosed picrites in gabbro are converted into amphibole-clinopyroxene fenites. Increases in Al, Ti, Fe3, Ca, K and Mn accompanied fenitization, Mg fell, and Cu, Sr, Y, Zr, Nb, La, Ce, and Nd were augmented. Mafic rocks against litchfieldite pegmatites were fenitized to mafic carbonatite or ijolite, felsic rocks to aegirine-augite syenites. Carbonatitic fenites developed by the introduction of Fe3, Ca, K, Mn, P, and C, and the abstraction of Si and Al. Zn, Rb, Y, Zr, Nb, and the light REE increased during fenitization. Ijolitization was caused by increases in Na, K, Al, and Fe3, while Si, Fe2, Mg, and Ca decreased. Fenitization was probably achieved through the agency of strong chloride brines.