Page "Syenite" Paragraph 11

The process which results in SiO < sub > 2 </ sub > depletion can be termed episyenitization.

This process is only referring to the macroscopic result of relative SiO < sub > 2 </ sub > depletion in a rock.

The actual physical process leading to this SiO < sub > 2 </ sub > depletion may vary in a given metamorphic environment.

Diffusion of chemical components in a stagnant fluid, related to differences in chemical potential or pressure as well as advection of a SiO < sub > 2 </ sub >- undersaturated fluid may lead to the dissolution of quartz from the un-altered rock, thus depleting it of this component.