The petrology of the Auckland Basalts

Abstract

The rocks of the Auckland volcanoes (late-Pleistocene and Recent) include the following types: olivine basalts; augite-rich picrite basalts; nepheline basanite. Less common varieties described are: basalts with noteworthy biotite; amphibole (cummingtonite) basalt, and rutile-bearing scoriaceous basalts associated with dykes intruding scoria cones and spatter cones. Ultrabasic nodules, interpreted as fragments of border facies crystallate, occur in tuff rings surrounding phreatic craters and supply xenolithic inclusions to minor flows associated with adjacent vents.