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Anhydrous partial melting of MORB pyrolite and other peridotite compositions at 10 kbar: implications for the origin of primitive MORB glasses

journal contribution
posted on 2023-05-18, 08:26 authored by Trevor FalloonTrevor Falloon, David GreenDavid Green
Anhydrous partial melting experiments on four peridotite compositions have been conducted at 10 kbar providing a relatively internally consistent set of data on the character of primary melts expected from the oceanic upper mantle in the mid-ocean ridge setting. The four peridotite compositions are: "MORB pyrolite" (considered to be suitable for the production of primitive (Mg#≥0.68) MORB glasses at 10 kbar), "Hawaiian pyrolite" (representative of "enriched" upper mantle), Tinaquillo lherzolite (representative of more "depleted" upper mantle), and the spinel lherzolite KLB-1 which is a suitable composition for the production of primitive MORB glasses. The equilibrium liquids were determined by "sandwich" experiments. The primitive MORB glass DSDP 3-18-7-1 was used in experiments using MORB pyrolite and KLB-1, while a calculated 10 kbar liquid composition from Jaques and Green (1980) was used in experiments with Hawaiian pyrolite and Tinaquillo lherzolite. The results of the experiments are used to test a 10 kbar melt model for the generation of primitive MORB glasses, which are parental magmas to typical MORB compositions. The melt compositions from the four peridotites studied are significantly different from primitive MORB glasses in major element chemistry and plot away from the field of primitive MORB glasses in the CIPW molecular normative "Basalt tetrahedron". The results indicate that primitive MORB glasses are derivative compositions lying on olivine fractionation lines from picritic parents, which themselves are primary magmas at pressures greater than 10 kbar. The results of this study are integrated with previous 10 kbar experimental studies.


Publication title

Mineralogy and Petrology










School of Natural Sciences


Springer-Verlag Wien

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