Petrological Data Allow Estimating the Amplitudes of Crustal Uplifts Caused by Retrograde Metamorphism

Abstract

Analysis of the morphology of the recent uplifts on Precambrian cratons and geological–geophysical data on the structure of the crust and mantle indicate that these structures were formed due to expansion of the crustal rocks as a result of retrograde metamorphism. This occurred due to the contribution of large volumes of deep fluids to the complexes of the Early Proterozoic rocks, which underwent high-grade metamorphism in the lower crust. Later, these complexes were moved to the shallower depths after denudation of thick overlap sequences from the craton’s surfaces. The calculation of the volumetric expansion effects using P–T diagrams for the main types of metamorphic rocks shows that this mechanism could have prompted the uplifts of the Precambrian crust in recent time with amplitudes from 100–200 to 1000–1500 m.