Metamorphism of tectonically thickened continental crust or subducted sediment wedges is likely to take place in a thermal regime where temperature increases by conductive relaxation whilst concurrently pressure decreases by erosion of the pile. The mineral facies of rocks reaching the surface do not reflect any one geotherm through the pile but lie on a locus of P–T conditions, the metamorphic geotherm, which will generally be concave towards the temperature axis. Maximum pressures on the metamorphic geotherm are significantly less than maximum pressures experienced by rocks during the early stages of recrystallization. The metamorphic geotherm is polychrome, points at lower temperatures reflecting conditions earlier in the development than those at higher temperature; crustal melts are developed after low-medium temperature metamorphism and the amount of such melts could be significant. Blueschists develop on the low temperature end of the metamorphic geotherm and are succeeded in exposure at the surface by greenschist- or amphibolite-facies rocks; the time-scale for this process is consistent with the virtual absence of Precambrian blueschists. Crust thickened by addition of hot magma is likely to yield a metamorphic geotherm convex towards the temperature axis. Recognition of differently curving metamorphic geotherms can be used to assess the part played by magmatic activity in older metamorphic terrains.

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Here, we report orbital-free density-functional theory (OF DFT) molecular dynamics simulations of the dynamic ion structure factor of warm solid density aluminum at T=0.5 eV and T=5 eV. We validate the OF DFT method in the warm dense matter regime through comparison of the static and thermodynamic properties with the more complete Kohn-Sham DFT. This extension of OF DFT to dynamic properties indicates that previously used models based on classical molecular dynamics may be inadequate to capture fully the low frequency dynamics of the response function.