Origin and differentiation of picritic arc magmas, Ambae (Aoba), Vanuatu

Article Abstract:

A study of the Ambae volcano, Vanuatu, reveals a low-titanium and high-titanium suite based on phenocryst mineralogy, geochemistry and stratigraphy. Low-titanium suites have a varied composition, from picritic to high-alumina basalts. The crystallization process of the low-titanium suite lava is systematic with the petrographically-determined order of crystallization. The geochemical difference and heterogeneity of the major lava suites are determined by samples obtained from the ocean crust either in the form of a silicate melt or as a fluid. The variation of the melting degree or the ratio in the depletion of the incompatible element of the peridotitic mantle wedge may differ in the two titanium suites.

Composition, Volcanoes

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Phase equilibria constraints

Article Abstract:

Evidence of the initial magma differentiation in the Hawaiian region lies in the magnesian olivine phenocrysts in tholeiites. These olivines crystalized from picritic melts with around 16% magnesium oxide on a weight basis. Experimental studies show that these melts were saturated with peridotite a number of times at a pressure lower than that at which garnet liquefies and at a temperature of 1450C. Inferences on the sources of the enriching materials and the differentiation of magma are presented.

Research, Environmental aspects, Magma, Porphyry

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Aspects of dynamic segregation

Article Abstract:

Dynamic melt segregation is a possible solution in the integration of the conflict between the trace element composition and evidence for phase equilibria during the generation of Hawaiian magma. Present models explaining the dynamics of melting were evaluated to verify this. Results indicate that more complex models involving dynamic melting in three dimensions are needed in order to get a satisfactory explanation of magma genesis in the Hawaiian region.

Models

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