Subsurface andesite lavas and plutonic rocks in the Rotokawa and Ngatamariki geothermal systems, Taupo Volcanic Zone, New Zealand

A review of the Rotokawa Geothermal Field, New Zealand

“…Overlying the basement is a laterally extensive, thick (up to 2200 m), andesite unit, the Rotokawa Andesite (Browne et al, 1992;Grindley et al, 1985;Rae, 2007;Rae et al, 2011;Wyering et al, 2014). Regional geological modelling of the Taupo-Reporoa Basin suggests that the Rotokawa Andesite complex is centred on the Rotokawa Geothermal Field, with limited lateral extent to both the north and south (Downs et al, 2014;Eastwood et al, 2013).…”

“…Regional geological modelling of the Taupo-Reporoa Basin suggests that the Rotokawa Andesite complex is centred on the Rotokawa Geothermal Field, with limited lateral extent to both the north and south (Downs et al, 2014;Eastwood et al, 2013). The initial andesitic volcanism would have involved magmas migrating through faults and fractures to the surface >∼1.9 Ma, constructing a large volcano under Rotokawa, potentially centred along the western border of the Rotokawa Geothermal Field based on lateral variation in thickness of the andesite (Anderson, 2011;Browne et al, 1992;Chambefort et al, 2014). A thick andesite unit overlying greywacke basement in the Ngatamariki Geothermal Field is likely to be part of the Rotokawa andesite complex (Chambefort et al, 2014;Downs et al, 2014), but petrographical and geochemical comparison of these two units indicates possible separate eruptive centres, with basaltic andesite present at Rotokawa, and more dacite/andesite composition volcanism at Ngatamariki (Anderson, 2011;Browne et al, 1992).…”

“…The surface geology, hydrothermal features, and subsurface stratigraphy and petrology of the Rotokawa Geothermal Field are detailed in numerous works and have been refined with subsequent field development and drilling stages (Anderson, 2011;Arehart et al, 2002;Browne, 1989;Browne et al, 1992;Browne and Lawless, 2001;Collar and Browne, 1985;Eastwood et al, 2013;Grindley et al, 1985;Krupp and Seward, 1987;Leonard et al, 2010;Milicich and Hunt, 2007;Pochee, 2010;Price et al, 2011;Rae, 2007;Rae et al, 2010Rae et al, , 2011Ramirez and Hitchcock, 2010;Schinteie et al, 2004;Siratovich et al, 2012Siratovich et al, , 2014Wallis et al, 2013;Wyering et al, 2014).…”

A “least complex” dynamic model for late Cenozoic volcanism in the North Island, New Zealand

“…2). The Rotokawa Andesites (Browne et al 1992) were probably erupted at times and localities between those of the above two pairs of lateral andesitic volcanoes, but were subsequently destroyed or overwhelmed by rhyolitic activity (e.g., fromTaupo).…”

Petrography and geochemistry of lithic fragments in ignimbrites from the Mangakino Volcanic Centre: Implications for the composition of the subvolcanic crust in western Taupo Volcanic Zone, New Zealand

“…Geophysical modelling by Stern (1987) suggested that all the subvolcanic basement of the TVZ was of "andesitic" composition. Deeper metamorphic and plutonic rocks have been postulated by Graham et al (1988) and Browne et al (1992).…”