Modal mineralogy and chemical composition of the Uralide lower crust determined from physical properties data

Modeling of rock physical properties of the Uralide lower crust is carried out using the Physprops Excel worksheet, which calculates its P-wave (Vp), S-wave (Vs), Poisson's ratio (σ), and density (ρ). The mineral modal abundance and composition of mafic granulite, mafic garnet granulite, amphibolite, and gabbronorite is modeled, and the composition of each is determined by converting the aggregate mineralogy into wt.% oxides. The modeled wt.% oxide composition of mafic (+ garnet) granulite fit well with those estimated for post-Archean terrains, and all are within 1σ of the average of all lower crustal xenoliths. The modeled gabbronorite also shows a reasonable fit with these estimates. The modeled amphibolite compositions show variations in the wt.% SiO₂, FeO and MgO with respect to the estimates of mafic granulite and amphibolite. The differences in the composition across the Uralide lower crust are largely due to the presence or absence of garnet in the mafic granulite, which may be a result of higher temperatures having been reached in the interior part of the orogen.