A systematic nomenclature for metamorphic rocks: 1. HOW TO NAME A METAMORPHIC ROCK Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: Web version 1/4/04. Rolf Schmid 1 , Douglas Fettes 2 , Ben Harte 3 , Eleutheria Davis 4 , Jacqueline Desmons 5, Hans- Joachim Meyer-Marsilius† and Jaakko Siivola 6 1 Institut für Mineralogie und Petrographie, ETH-Centre, CH-8092, Zürich, Switzerland, [email protected] 2 British Geological Survey, Murchison House, West Mains Road, Edinburgh, United Kingdom, [email protected] 3 Grant Institute of Geology, Edinburgh, United Kingdom, [email protected] 4 Patission 339A, 11144 Athens, Greece 5 3, rue de Houdemont 54500, Vandoeuvre-lès-Nancy, France, [email protected] 6 Tasakalliontie 12c, 02760 Espoo, Finland ABSTRACT The usage of some common terms in metamorphic petrology has developed differently in different countries and a range of specialised rock names have been applied locally. The Subcommission on the Systematics of Metamorphic Rocks (SCMR) aims to provide systematic schemes for terminology and rock definitions that are widely acceptable and suitable for international use. This first paper explains the basic classification scheme for common metamorphic rocks proposed by the SCMR, and lays out the general principles which were used by the SCMR when defining terms for metamorphic rocks, their features, conditions of formation and processes. Subsequent papers discuss and present more detailed terminology for particular metamorphic rock groups and processes. The SCMR recognises the very wide usage of some rock names (for example, amphibolite, marble, hornfels) and the existence of many name sets related to specific types of metamorphism (for example, high P/T rocks, migmatites, impactites). These names and name sets clearly must be retained but they have not developed on the basis of systematic classification. Another set of metamorphic rock names, which are commonly formed by combining mineral names with structural terms (for example, quartz-mica schist, plagioclase- pyroxene granofels) is capable of being used in a systematic way. The SCMR recommends that such compound names are systematically applied using three root names (schist, gneiss and granofels), which are defined solely by structural criteria. Such systematic names are considered particularly appropriate when specific names are unknown or uncertain. A flow chart on ‘How to Name a Metamorphic Rock’ enables any earth scientist to assign a name to a metamorphic rock, following this scheme. The paper further gives guidelines on the appropriate use of these systematic names and on the use of possible alternatives based on the protolith and other specific names. INTRODUCTION Constitution of the SCMR The Subcommission on the Systematics of Metamorphic Rocks (SCMR) is a branch of the IUGS Commission on the Systematics in Petrology (CSP). It started operating in 1985, with douglas fettes Page 1 25/05/2004SCMR_HOW_R4.doc 1
HOW TO NAME A METAMORPHIC ROCK
Jun 23, 2023
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