An experimentally constrained petrogenetic grid in the silica-saturated portion of the system KFMASH at high temperatures and pressures

Abstract

Experiments in the quartz-saturated part of the system KFMASH under fO₂ conditions of the haematite-magnetite buffer and using bulk compositions with X_Mg of 0.81, 0.72, 0.53 define the stability limits of several mineral assemblages within the P-T field 9-12 kbar, 850-1100°C. The stability limits of the mineral assemblages orthopyroxene + spinel + cordierite±sapphirine, orthopyroxene + garnet + sapphirine, sapphirine + cordierite + orthopyroxene and garnet + orthopyroxene + spinel have been delineated on the basis of P-T and T-X pseudosections. Sapphirine did not appear in the bulk composition of X_Mg=0.53. A partial petrogenetic grid applicable to high Mg-Al granulites metamorphosed at high fO₂, developed in our earlier work, was extended to higher pressures. The experimental results were successfully applied to several high-grade terranes to estimate P-T conditions and retrograde P-T trajectories.