Structure and kinematics of the Taupo Rift, New Zealand

Abstract

The structure and kinematics of the continental intra-arc Taupo Rift have been constrained by fault-trace mapping, a large catalogue of focal mechanisms (N = 202) and fault slip striations. The mean extension direction of~137°is approximately orthogonal to the regional trend of the rift and arc front (α = 84°a nd 79°, respectively) and to the strike of the underlying subducting Pacific Plate. Bending and rollback of the subduction hinge strongly influence the location, orientation, and extension direction of intra-arc rifting in the North Island. In detail, orthogonal rifting (α = 85-90°) transitions northward to oblique rifting (α = 69-71°) across a paleovertical-axis rotation boundary where rift faults, extension directions, and basement fabric rotate by~20-25°. Toward the south, extension is orthogonal to normal faults which are parallel to, and reactivate, steeply dipping basement fabric. Basement reactivation facilitates strain partitioning with a portion of margin-parallel motion in the overriding plate mainly accommodated east of the rift by strike-slip faults in the North Island Fault System (NIFS). Toward the north where the rift and NIFS intersect,~4 mm/yr strike slip is transferred into the rift with net oblique extension accommodating a component of margin-parallel motion. The trend and kinematics of the Taupo Rift are comparable to late Miocene-Pliocene intra-arc rifting in the Taranaki Basin, indicating that the northeast strike of the subducting plate and the southeast extension direction have been uniform since at least 4 Ma.

A review of the Rotokawa Geothermal Field, New Zealand

“…More localised stress field rotations are attributed to slip on fracture planes with the larger perturbations inferred to indicate the presence of a nearby, large scale, active fault. Overall, in situ stress field orientation measurements are consistent with an extensional tectonic regime in the Rotokawa Geothermal Field, and with previous studies of stress orientations in the TVZ (Hurst et al, 2002;Massiot et al, 2013;McLean and McNamara, 2011;Seebeck et al, 2014;Townend et al, 2012;Wallis et al, 2012) and with preliminary determinations of in situ stress magnitudes for the Rotokawa Geothermal Field .…”

“…The TVZ is an actively rifting, intra-arc basin associated with the Hikurangi subduction system, where the Pacific Plate subducts beneath the eastern side of the North Island (Cole and Spinks, 2009;Rowland and Simmons, 2012;Wilson et al, 1995). Rifting, which is thought to have begun ∼2 Ma (Wilson et al, 1995), occurs at varying rates along the ∼NE-SW rift axis, from ≤5 mm/year at the southernmost limit of rifting extension to 13-19 mm/year in offshore Bay of Plenty (Begg and Mouslopoulou, 2009;Seebeck et al, 2014;Berryman, 2001, 2006). The Rotokawa geothermal system itself has been suggested to be up to 20,000 years old based on knowledge of timing of hydrothermal eruptions (Krupp and Seward, 1987;Vucetich and Howorth, 1976).…”

The effect of crustal melt on rift dynamics: case study of the Taupo Volcanic Zone

“…The model is run for 10 mechanical/thermal iterations to allow the Seebeck et al (2014). B, As for A, but strength of partial melt is not allowed to drop below 10 18 Pas.…”

Contemporary tectonic stress pattern of the Taranaki Basin, New Zealand

“…The geometry of slab and strike of Taupo rift are from Seebeck et al . [, ]. All these azimuthal features are interrelated because they are caused by or are consequences of the in situ stress field and the plot shows that most of the data are consistent with each other.…”

“…Seebeck et al . [] also suggested a NE‐SW trend for active normal faults of the Taupo Rift Zone (east of the Taranaki Basin), where kinematic data show a mean extension of S43°E (±23). Generally, most of the studies in the Taranaki Basin, and active intra‐arc rift in the central North Island, suggest significant NW‐SE extension on the NE trending faults, which is consistent with the regional N68°E (±22°) S Hmax orientation determined in his study (Figure ).…”