Punctuated Arc Migration: Origins and Antecedents of the Taupo Volcanic Zone, New Zealand
Abstract
The modern Taupo Volcanic Zone (TVZ) is one of the most highly active continental arcs on Earth. Among many challenges is disentangling the Miocene to Recent volcanic and structural history of the North Island in order to understand why such a situation should arise in an otherwise conventional setting. This history is tied to the evolution of the Colville and Kermadec arcs and their onshore manifestation in the continental crust of New Zealand. The modern NNE-SSW subduction orientation dates from ca. 16 Ma, coeval with activity along the Colville Arc. Migration of the arc to the southeast into its modern position, manifest by the Kermadec Arc, occurred with offshore opening of the Havre Trough ca. 6 Ma. Subduction-related andesitic volcanism migrated southwards both in onshore Coromandel and offshore Taranaki areas but volcanism was conspicuously sparse from the intervening continental region until ca. 3 Ma. This anomalous situation may be explained by the concurrent activity on the back-thrust Taranaki Fault, which implies a compressive stress regime was present throughout central North Island up to ca. 4 Ma. There appears to be linkage over a period around 4 ± 2 Ma in: a) significant opening of the Havre Trough, b) rapid migration into and onset of major silicic volcanism in the early TVZ, c) cessation of thrusting on the Taranaki Fault, and d) diminution of offshore Taranaki volcanism. Prior to 4 Ma, north to south migration of ages in Coromandel is matched by migration of centers in offshore Taranaki, implying that from 16 Ma onwards, expression of the arc across the North Island was parallel to its modern orientation. Subsequent to 4 Ma, arc volcanism and magmatism has been focused in the TVZ (from 2 Ma onwards), and intraplate volcanism of gradually diminishing volume and intensity developed and moved northwards from the former alignment of the arc to where it now lies underneath Auckland. The modern fabric of volcanic and structural lineaments and crustal anisotropy in and below the central North Island is dominated by Mesozoic large scale terrane boundaries and block faults associated with the Cretaceous rifting of New Zealand from Australia. Within the history of TVZ, evidence suggests that the volcanic zone migrates by discrete jumps of the order of ca. 10 km in en echelon fashion, without significant rotation, exploiting these pre-existing structures at least in part. We suggest such a pattern may have been active since 16 Ma. The present-day TVZ is an actively rifting arc, with geodetically measured widening ranging from 7 mm/yr at the south end to 15 mm/yr at the Bay of Plenty coast line. Though this reflects rotation of the forearc region with respect to a fixed western North Island, it is accomplished by differential opening of arc parallel rift structures, not by rotation of the arc as a whole.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.V23E2173R
- Keywords:
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- 8178 TECTONOPHYSICS / Tectonics and magmatism;
- 8185 TECTONOPHYSICS / Volcanic arcs;
- 8413 VOLCANOLOGY / Subduction zone processes