Are olivine-poor nephelinites a primary melt product from the mantle?

Bas, Le

doi:10.1007/bf02597379

Cited by 4 publications

(1 citation statement)

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“…The lowest SiO 2 content that has been obtained in recent high-pressure melting experiments to 3-5 GPa is ~46 wt.% (Jacques & Green, 1980;Takahashi & Kushiro, 1983;Falloon & Green, 1988;Falloon et al, 1988). It has been proposed, however, that melting under volatile-saturated conditions with high H 2 O and CO 2 contents and a high CO 2 /H 2 O ratio could generate highly undersaturated liquids (Brey & Green, 1977;Brey, 1978;Le Bas, 1978). The association of carbonatites with isotopically similar nephelinites, ijolites, and basanites on the neighboring island of Fuerteventura (Hoernle & Tilton, 1991) supports the derivation of the undersaturated mafic volcanics from sources rich in C-bearing species.…”

Section: The Role Of Major Mantle Phases and Volatilesmentioning

confidence: 99%

The Role of Partial Melting in the 15-Ma Geochemical Evolution of Gran Canaria: A Blob Model for the Canary Hotspot

Hoernle

Schmincke

1993

Journal of Petrology

215

101

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The subaerial portion of Gran Canada, Canary Islands, was built by three cycles of volcanism: a Miocene Cycle (8-5-15 Ma), a Pliocene Cycle (1-8-60 Ma), and a Quaternary Cycle (1-8-0 Ma). Only the Pliocene Cycle is completely exposed on Gran Canaria; the early stages of the Miocene Cycle are submarine and the Quaternary Cycle is still in its initial stages. During the Miocene, SiO 2 saturation of the mafic volcanics decreased systematically from tholeiite to nephelinite. For the Pliocene Cycle, SiO 2 saturation increased and then decreased with decreasing age from nephelinite to tholeiite to nephelinite. SiO 2 saturation increased from nephelinite to basanite and alkali basalt during the Quaternary. In each of these cycles, increasing melt production rates, SiO 2 saturation, and concentrations of compatible elements, and decreasing concentrations of some incompatible elements are consistent with increasing degrees of partial melting in the sequence melilite nephelinite to tholeiite. The mafic volcanics from all three cycles were derived from CO 2-rich garnet lherzolite sources. Phlogopite, ilmenite, sulfide, and a phase with high partition coefficients for the light rare earth elements (LREE), U, Th, Pb, Nb, and Zr, possibly zircon, were residual during melting to form the Miocene nephelinites through tholeiites; phlogopite, ilmenite, and sulfide were residual in the source of the Pliocene-Quaternary nephelinites through alkali basalts. Highly incompatible element ratios (e.g.

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