Evolution of host‐inclusion systems: a visco‐elastic model

A visco‐elastic model is suggested to recover the P−T−t paths of spherically symmetrical host‐inclusion systems from residual pressure patterns. For a coesite–garnet, aragonite–garnet and diamond–garnet system with partial transition of high pressure polymorphs to low pressure ones, the model predicts that the exhumation history of ultra‐high pressure metamorphic rocks from depths below 90 km began with pressure decrease to ∼1 GPa (∼40 km depth), while the temperature remained high (>800 C); then the system cooled and decompressed to ambient conditions. Non‐spherical inclusion shapes in the 3‐D model lead to heterogeneities in residual pressure and shear stress distributions as well as to significant gradients of shear stress, which may affect the kinetics and thermodynamics of phase transformation in the inclusions.