Why the pounamu? Low- to medium grade metabasites and metaultrabasites of New Zealand from a geoheritage perspective

Abstract

Pounamu plays a very important role in Māori culture (New Zealand) and is a taonga (treasure) of the people. Pounamu is a result of the intricate, unique geological context of the Zealandia microcontinent in the SW Pacific successfully separated from Gondwana in the Late Mesozoic but cut half in a NE-SWE trending right-lateral strike-slip dominated plate boundary separating the Indo-Australian and Pacific Plates within the continental lithospheric segment of Zealandia. Along this nearly 500 km onshore structural zone, a set of narrow Paleozoic to Mesozoic lithospheric terrains assembled among ophiolite belts such as the Dun Mountain Terrain. Metasomatic influence on the ancient seafloor in combination with high-grade regional metamorphic forces along the evolving plate boundaries, a globally unique region with high geodiversity formed, giving way to the assemblage of metamorphosed ultramafic bodies to generate great variety of greenstones, referred as pounamu by Māori. The perfect physicochemical conditions of this rock made it to become a key geomaterial for tool-making and trade subjects within the Māori culture.