Experimental high-pressure granulites: some applications to natural mafic xenolith suites and Archean granulite terranes

High-pressure granulite assemblages have been produced as residues in partial melting experiments on a natural (alkalic basalt) amphibolite between pressures of 12 and 18 kbar. The experimental results help place additional pressure-temperature-a(H₂O) constraints on the source region for the natural high-pressure granulites. The experimental residue assemblage formed at 18 kbar has been described in natural xenolith suites from the Delegate Pipes in Australia in the Bearpaw Mountains, Montana. The combination of these data shows that the xenoliths may indeed represent lowermost continental crust and furthermore helps interpret the nature of the crust-mantle boundary in these areas. -from Author