A model for low‐pressure facies metamorphism during crustal thickening

Low‐pressure metamorphic facies (i.e. high T/P ratios) are widespread in a wide range of tectonic settings. Explanations offered for the occurrence of these facies include extensional and/or magmatic models. However, these fail to explain that the low‐ P facies metamorphism is commonly coeval with a phase of pervasive crustal thickening, with T/P ratios increasing during, or slightly lagging behind, the thickening. We propose an alternative explanation based on the approximate synchroneity of crustal thickening and erosion (thinning) of the mantle lithosphere.