METAMORPHISM AND DEFORMATION
The realtionship between the two may be
syn- pre-, post or intertectonic or inter-metamorphic.
inclusion pattern is random, indicating no foliation at time of porphyroblast growth and younger foliation may be deflected around the porphyroblast giving rise to the situation of schistosity wrapping around porphyroblasts.
inclusions are aligned according to a foliation that was overgrown by the porphyroblast, and inclusion pattern bears no relation with the foliation outside the porphyroblast. Younger foliation may be deflected around the porphyroblast inclusion trails and outside foliation are discontinuous.
Inclusion trails and outside foliation are continuous inclusion pattern and outside foliation are similar, but inclusion trails may preserve outside foliation in an early stage of development. gradual transition of pattern and orientation of inclusion trails from core to rim of porphyroblast
orientation of inclusion trails in core of porphyroblast may have different orientation due to rotation of porphyroblast during its growth (e.g., snowball garnets)
possible deflection of foliation outside porphyroblast
Inclusion trails and outside foliation are completely continuous and similar
no deflection of foliation outside porphyroblast. Post-tectonic minerals in outcrop are unlineated and (some places) unfoliated.
Effects of Deformation on Metamorphism
Grain-size reduction through cracking or dislocation creep produces more grain-boundary area, which aids metamorphic reactions by adding interfacial free energy and diffusive pathways.
The motion of dislocations through crystals can act as sweeps to change crystal composition.