Petrographic studies of ironsands and associated sediments near Hawera, South Taranaki

Abstract Studies of ironsands near Hawera included detailed examinations of the mechanical and mineralogical properties of present‐day beach deposits and dune sands. Mineral assemblages of sands from the Rapanui Formation and heavy mineral suites from the underlying Waipipi Formation were also investigated. Whereas minerals of granitic‐metamorphic origin characterised the Waipipi Formation, minerals of recent volcanic (andesitic) origin were predominant in the bedded deposits of the Rapanui Formation and in recently formed ironsands. Measurements of the abundance of the principal ferromagnesian minerals in andesitic sands near Hawera indicate that they were ultimately derived from augite andesites and augite‐hornblende andesites from Mt Egmont. The complete absence of andesitic minerals in the Waipipi Formation clearly shows that either activity along the Egmont volcanic line had not yet begun or, if it had, the products of these eruptions had not been incorporated into the sedimentary record before the end of of the Waipipian.