MELILITOLITES - A NEW SCHEME OF CLASSIFICATION

A new scheme of classification is proposed for melilite-bearing pluton ic rocks with more than 10% melilite and less than 50% primary carbona te phases, based on the absolute modal abundances of the dominant mine rals. Melilitolite is retained as a ''general'' root-name for all such rocks, previous definitions of terms used in the classification of th ese rocks, including afrikandite, kugdite, okaite, turjaite and uncomp ahgrite, are modified in order to provide ''specific'' root-names for melilitolites. A new rock-name, ''ultramelilitolite'', is proposed as a specific root-name for samples with more than 65% melilite. The use of multiple root-names and the problems associated with the use of min eral modifiers in rock nomenclature are discussed.