The importance of lithology in determining response to metamorphism and tectonic forces*

Abstract Evidence from the Wellington region, the lower Pareora Gorge, and the Otago schist belt testifies clearly to the importance of lithology in determining response of rocks to metamorphism and tectonic forces. The order of decreasing response appears to be: volcanic argillites (claystones), argillites (siltstones), lavas, greywackes (sandstones), jaspers and cherts. It is, essential in regional metamorphic studies to distinguish between original lithology, metamorphic lithology, degree of internal reconstitution, and mineralogical changes. Both textural and mineralogical metamorphic rank should be based on the response of one rock type (greywacke). The “normal” or “standard” metamorphic sequence is that in which textural change of the selected rock type is accompanied by a full succession of mineralogical changes, and this is more nearly attained in south‐cast Nelson than in Otago. Just as metamorphic textural :md mineralogical rank should be based on greywacke so too should interpretations of regional structure be based on one lithology.