Petrography of the Whakapapanui Gorge Andesites, Mount Ruapehu

Abstract

Petrological study of the andesite lavas exposed in Whakapapanui Gorge on the northern slopes of Mt. Ruapehu reveals constant mineralogical composition of flows. All are porphyritic andesites with phenocrysts of plagioclase, hypersthene, and augite set in a hyalopilitic groundmass. Slight variations in texture sometimes occur between and within flows of lava.