Compositions of anhydrous and hydrous melts coexisting with plagioclase, augite, and olivine or low-Ca pyroxene from 1 atm to 8 kbar; application to the Aleutian volcanic center of Atka

Phase relations and partial melt compositions have been determined for a suite of high-alumina basalts and andesites from the Aleutian island of Atka and from the Mariana islands. Experimental conditions varied from anhydrous, at P from 1 atm to 8 kbar, to hydrous (2% H2O in the melt) at 2 and 5 kbar, although not all compositions were studied at all conditions.