Towards Deciphering Metamorphic Reaction Kinetics through Porphyroblastic Textural Analysis in the Bugaboo Contact Aureole (South Eastern British Columbia, Canada)

The relative rate of intergranular diffusion and interfacial attachment of chemical species during low-pressure metamorphic reactions is determined through analyzing the texture of porphyroblastic phases in the Bugaboo contact aureole. The observed mineral assemblages are predicted to be in equilibrium from 500-590°C at 1.60 kbar with graphite and a COH-bearing fluid. Porphyroblasts of Bt+And+Crd±Pl within the outer aureole display syn-kinematic growth textures while the inner aureole consists of pre-kinematic Bt+And+Crd+Kfs. Chemical homogeneity of Bt+Crd+prograde and retrograde Chl indicate retrograde chemical equilibration. Mineral chemistries therefore do not provide reliable P-T estimates for prograde metamorphism and the relative rate between reaction processes. The 3D spatial distribution of Bt+Crd from the outer aureole is obtained using XR-μCT to study the effects of metamorphic reaction processes on resultant porphyroblastic texture. Mineral texture is shown to be more reliable over mineral chemistry when deciphering the kinetics of metamorphic processes.