Comment on 'Mexican Peridotite Xenoliths and Tectonic Terranes: Correlations among Vent Location, Texture, Temperature, Pressure, and Oxygen Fugacity' by J. F. Luhr & J. J. Aranda-Gomez (1997)

Abstract

This comment addresses the interpretation of oxygen fugacity data for spinel peridotite xenoliths from five Mexican volcanic fields presented by Luhr & Aranda-Gomez (Journal of Petrology, 38, 1075–1112, 1997). The postulated east–west increase of the ΔFMQ (‘relative oxygen fugacity’, where FMQ is fayalite–magnetite–quartz) values is inherent to the method and therefore of questionable geological significance. Increases in ΔFMQ do not necessarily mirror oxidation processes in the mantle controlled by subduction-related fluids.