The partial melting of natural lherzolite KLB-1 at 1 GPa was studied for both H2O undersaturated and saturated conditions. The quenched glasses obtained at 1000 and 1050 °C are andesitic in composition, having 54.4–60.3 wt% SiO2, whereas partial melts formed at temperatures above 1100 °C have basaltic compositions. This suggests that high-magnesian andesites can be formed by direct partial melting of the hydrous upper mantle only at relatively low temperatures. These andesitic melts, together with those obtained at 1100 °C, contain more than 3 wt% H2O and have compositions characteristic of hydrous melts—high SiO2 and Al2O3 and low FeO*, MgO, and CaO. The results of melting studies on KLB-1 show a strong increase in the degree of melting when H2O is added to lherzolite at a given temperature.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.