THE PROBLEM OF SUBDIVISION OF METAMORPHIC ROCK SEQUENCES FOR GEOLOGICAL MAPPING

Abstract

Problems concerning the methodology of subdivision and mapping of metamorphic rock units, their taxonomy, and nomenclature are discussed. Several of the most important concepts are specified, and the necessity of elaborating the taxonomic system of metamorphic units and their nomenclature is substantiated. Regional subdivisions, such as metamorphic rock complexes, are considered to represent taxons of the highest hierarchic rank because of their significant role in the structure of major elements of the earth crust, such as structural-formational zones (regions). The main mappable units are taxons of a lower rank identified as metamorphic rock formations (stable parageneses of metamorphic rocks). Metamorphic units represent secondary geological bodies and should not be considered and mapped in general (not specialized) geological maps as units equal in rank to primary (stratigraphic and plutonic) units.