[1] In a general sense, talc carbonate metamorphic assemblages are diagnostic of the magnesium content of the ultramafic protolith.
It is common to see serpentinites which contain talc, amphibole and chloritic minerals in small proportions which infer the presence of carbon dioxide in the metamorphic fluid.
Felsic and mafic rocks tend to be less affected by carbon dioxide due to their higher aluminium content.
Advanced carbonation of felsic and mafic rocks, very rarely, creates fenite, a metasomatic alteration caused particularly by carbonatite intrusions.
Fenite alteration is known, but very restricted in distribution, around high-temperature metamorphic talc-carbonates, generally in the form of a sort of aureole around ultramafics.