Kinetic modeling of the coesite–quartz transition in an elastic field and its implication for the exhumation of ultrahigh‐pressure metamorphic rocks

Abstract

The present paper examines a kinetic model of the coesite–quartz transition under an elastic field. This model is applied to discuss the possible exhumation path of ultrahigh‐pressure (UHP) metamorphic rocks. By incorporating the model of transition kinetics into a three‐shelled composite sphere model in linear elasticity, the internal stresses in coesite, quartz, and garnet shells were calculated for given external pressure (P)–temperature (T ) paths. The occurrence of rupture provides a constraint on the temperature and the amount of quartz inverted from coesite at the rupture for each P–T path. Comparison of calculated results and the natural occurrence of coesite inclusion from the Dora Maira Massif, containing ∼ 27% quartz at the rupture, enables us to constrain the possible exhumation path and possible transition kinetics. A steep decompression path with slow transition kinetics is most favorable, which is consistent with the estimated P–T path during exhumation for most UHP metamorphic rocks.