Appraisal of classification for metamorphosed mafic igneous rocks (MMIR): igneous petrologist’s perspective

Abstract

Although there are many text books on metamorphic petrology suggesting how to name or classify metamorphosed mafic igneous rocks (MMIR), there is no consensus on these aspects. Mostly available names/terms are suggested in terms of metamorphic facies/grades. Many times it is difficult to name a MMIR, particularly if one is interested to study MMIR to know their magmatic origin. This problem persists because of the IUGS recommendation that any rock (igneous or metamorphic) must be named or classified on the basis of its mineral composition and not on its chemistry. In many cases, more than one name/term is available to denote a particular type of MMIR, and for a similar mineral assemblage, different names/terms are used by different workers. This creates avoidable confusion. It is more difficult if one is studying a terrain having MMIR of different metamorphic facies. There is a need to evaluate available classifications for the MMIR and have a single classification scheme for MMIR. In this communication an attempt is made to propose a scheme for classifying MMIR. It is believed that this nomenclature/classification scheme would help to avoid some confusion while referring to MMIR.