HIGH-TEMPERATURE DENSITIES OF SOME MANTLE MELTS

Abstract

One-atmosphere density measurements at very high temperatures have been performed on four mantle melts in the FeO-Fe2O3-CaO-MgO-Al2O3-SiO2 system (FeO-rich peridotite, PHN 1611, komatiite, and fayalite), using the Ir-based double-bob Archimedean method in air. The one-atmosphere density of the investigated materials ranges from 2.6 to 3.6 g/cm3 from their respective melting points up to 2123 K. Combined with earlier high-pressure static experiments on the same compositions, the present one-atmosphere densities provide robust constraints on the isothermal compression curves of such Fe-bearing silicate melts and yield new values of the isothermal bulk modulus (KT) and its pressure derivative (K′T) through application of the third order Birch-Mumaghan equation of state. The present KT and K′T values are significantly different from those previously reported using the high-pressure dataset together with calculated one-atmosphere densities using existing schemes. Comparisons with KT - K′T systematics from the literature are also made.