Original paper

Fractional melting the determining factor in the origin of the tephrite basanite nephelinite rock suite: evidence from western Makhtesh Ramon, Israel

Samoilov, Valery S.; Vapnik, Yevgeny

Abstract

Early Cretaceous alkaline magmatism occurred in Makhtesh Ramon (Southern Israel) with the formation of a rock suite including tephrite, basanite, basanitic nephelinite and olivine and melilite - olivine nephelinite. Alkaline magma genesis took place in a mantle setting; the source of magma is an enriched mantle that was similar to HIMU-ocean island basalts. Basanite, basanitic nephelinite, and olivine nephelinite represent portions of magma that formed as a result of different degrees of fractional melting of an enriched mantle source within the boundary conditions from garnet lherzolite to spinel lherzolite stability fields. The increase in magma alkalinity involved silica depletion and the enrichment in basic components (Ca, Mg, and Fe), phosphorus and numerous trace elements, including both compatible (Co, Ni, Cr, and V) and incompatible (Sr, Ba, Nb, Ta, Zr, Hf, Pb, REE, and Y) elements.Crystallization of alkaline melts was accompanied by their differentiation with the formation mainly of coupled rock unit associations, such as tephrite - basanite, basanite - basanitic nephelinite and olivine nephelinite - melilite - olivine nephelinite.

Keywords

tephrite - basanite - nephelinite suitepartial mantle meltingpetrologygeochemistryisrael