Abstract

The IUGS international classification of granitic rocks is criticized for broadening the definition of granite and changing the generally accepted meaning of rock names like quartz monzonite and tonalite. This classification apparently sacrificed established or original usage for a more symmetrical classification scheme. Two-feldspar granite is proposed for part of the IUGS field of granite, and adamellite is proposed for the other part. The name “quartz monzonite” should be dropped entirely because it serves only to confuse the classification of granitic rocks. Tonalite and quartz diorite should be reversed in the IUGS scheme because the original meaning of the former rock indicates more affinities to diorite than to granodiorite.

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