Summary: Petrology of some oceanic island basalts: PRIMELT2.XLS
software for primary magma calculation
Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, USA (email@example.com)
P. D. Asimow
Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
 PRIMELT2.XLS software is introduced for calculating primary magma composition and mantle
potential temperature (TP) from an observed lava composition. It is an upgrade over a previous version in
that it includes garnet peridotite melting and it detects complexities that can lead to overestimates in TP by
>100°C. These are variations in source lithology, source volatile content, source oxidation state, and
clinopyroxene fractionation. Nevertheless, application of PRIMELT2.XLS to lavas from a wide range of
oceanic islands reveals no evidence that volatile-enrichment and source fertility are sufficient to produce
them. All are associated with thermal anomalies, and this appears to be a prerequisite for their formation.
For the ocean islands considered in this work, TP maxima are typically $14501500°C in the Atlantic and
15001600°C in the Pacific, substantially greater than $1350°C for ambient mantle. Lavas from the
Gala´pagos Islands and Hawaii record in their geochemistry high TP maxima and large ranges in both TP
and melt fraction over short horizontal distances, a result that is predicted by the mantle plume model.
Components: 14,488 words, 12 figures, 1 table.
Keywords: mantle plumes; oceanic island basalts; mantle potential temperature; primary magma.
Index Terms: 3621 Mineralogy and Petrology: Mantle processes (1038); 3610 Mineralogy and Petrology: Geochemical