Abstract
Plagioclase in olivine metagabbros metasomatized by nepheline syenite magmas was replaced by intergrowths of nepheline and vesuvianite or salite together with smaller amounts of calcic amphibole. Olivine was simultaneously replaced by diopside. The survival of the gross features of protolith textures and clustering of line intersections in composition-volume diagrams suggest that nephelinization took place at approximately constant volume and oxygen content. Nephelinization involved the introduction of Na, K and Fe3+ in an infiltrating peralkaline fluid and depletion of Fe2+ and Fetot and was promoted by the primary mineral parageneses of the protoliths. Concurrent fenitization of quartzo-feldspathic gneiss without the generation of feld-spathoids shows that the processes of nephelinization and fenitization may result from the same fluid.
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Robins, B. Petrography and petrogenesis of nephelinized metagabbros from Finnmark, Northern Norway. Contr. Mineral. and Petrol. 86, 170–177 (1984). https://doi.org/10.1007/BF00381844
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DOI: https://doi.org/10.1007/BF00381844