They are typically 'coughed up' from the mantle as xenoliths, masses in other magmas, and probably form when mafic magmas mix with peridotite. Although they are rare, they are found all over the world. They are both highly alkaline, like carbonatite, lamprophyre and kimberlite. Nephelinite is essentially nepheline and clinopyroxene, plus olivine and iron and titanium oxides.
They are typically 'coughed up' from the mantle as xenoliths, masses in other magmas, and probably form when mafic magmas mix with peridotite. Although they are rare, they are found all over the world. They are both highly alkaline, like carbonatite, lamprophyre and kimberlite. Nephelinite is essentially nepheline and clinopyroxene, plus olivine and iron and titanium oxides.
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