1. Introduction

Pyrometamorphism, from the Greek pyr/pyro = fire, meta = change; morph = shape or form, is a term first used by Brauns (1912a, b) to describe high temperature changes which take place at the immediate contacts of magma and country rock with or without interchanges of material. The term was applied to schist xenoliths in trachyte and phonolite magma of the Eifel area, Germany, that had undergone melting and elemental exchange (e.g. Na₂O) with the magma to form rocks consisting mainly of alkali feldspar (sanidine, anorthoclase), cordierite, spinel, corundum, biotite, sillimanite and (relic) almandine garnet ± andalusite. Brauns (1912a, b) considered the essential indicators of pyrometamorphism to be the presence of glass with the implication that temperatures were high enough to induce melting, the formation of pyrogenic minerals (i.e. crystallized from an anhydrous melt), replacement of hydrous minerals by anhydrous ones, the preservation of the crystal habits of reacted minerals and of rock textures.