Depth and degree of melting of komatiites

Details Depth and degree of melting of komatiites Depth and degree of melting of komatiites

Apr 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992jgr....97.4521h&link_type=abstract

Journal of Geophysical Research (ISSN 0148-0227), vol. 97, no. B4, April 10, 1992, p. 4521-4540.

Physics

52

Earth Mantle, Geochemistry, Igneous Rocks, Magnesium Oxides, Volcanoes, Geophysical Fluids, Melting, Peridotite, Planetary Evolution, Pyroxenes

Scientific paper

High pressure melting experiments have permitted new constraints to be placed on the depth and degree of partial melting of komatiites. Komatiites from Gorgona Island were formed by relatively low degrees of pseudoinvariant melting involving L + Ol + Opx + Cpx + Gt on the solidus at 40 kbar, about 130 km depth. Munro-type komatiites were separated from a harzburgite residue (L + Ol + Opx) at pressures that were poorly constrained, but were probably around 50 kbar, about 165 km depth; the degree of partial melting was less than 40 percent. Secular variations in the geochemistry of komatiites could have formed in response to a reduction in the temperature and pressure of melting with time. The 3.5 Ga Barberton komatiites and the 2.7 Ga Munro-type komatiities could have formed in plumes that were hotter than the present-day mantle by 500 deg and 300 deg, respectively. When excess temperatures are this size, melting is deeper and volcanism changes from basaltic to momatiitic. The komatiities from Gorgona Island, which are Mesozoic in age, may be representative of komatiities that are predicted to occur in oceanic plateaus of Cretaceous age throughout the Pacific (Storey et al., 1991).

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