Mélanges and associated rocks, Livingstone Mountains, Southland, New Zealand

Abstract

Four parallel belts of rocks west of North Mavora Lake, northern Southland, New Zealand, are mapped and described. The easternmost belt, the West Burn semischists, consists of reconstituted spilites, phyllites, and semischists, whose textural grade of metamorphism increases up-section to the west. The two central belts are melanges, one with serpentinite matrix and small tectonic inclusions (Upukerora melange), while the other has a spilitic matrix and large (up to several kilometres) tectonic inclusions (Windon mélange). The westernmost belt consists of overturned volcanogenic Upper Permian sediments (Bryneira Group). Regional metamorphism ranges from pumpellyite-actinolite facies, over most of the area, to lawsonite-albite-chlorite facies in Bryneira Group. Localised bodies of greenschist facies rocks occur in fault zones. Metasomatism is very pronounced in the serpentinite melange. Pectolite occurs abundantly as a low temperature metasomatic vein and replacement mineral. The area has been complexly faulted, with few unfaulted primary contacts remaining. The largest fault, Livingstone Fault, is of regional significance.