Alpine-type Serpentinites from the Auckland province—I. The Wairere Serpentinite

Abstract

The Wairere Serpentinite, exposed over 650 m along the trace of the Waipa Fault near Piopio, lies close to the boundary of the marginal and shelf facies of the New Zealand Geosyncline and hence close to Hatherton and Sibson's magnetic junction anomaly. The body shows faulted contacts against Hokonui, Te KuitI, Mahoenui, and Mokau rocks. Emplacement is believed to have occurred as a diapiric process, in response to a compressive stress system, penecontemporaneously with deposition of the Otorohanga Limestone (Lower Waitakian). The limestone suffered folding and formation of pinch and swell structures, local brecciation and recrystallisation, slickensiding, and jointing. Aragonite is widespread both at contacts and on shear planes throughout the serpentinite. Movement continued well into the Miocene with brecciation of Mokau sediments.