Rhyolitic volcanic corridors in magmatic arcs: comparing North Wales and North Island, New Zealand

Abstract

Exceptionally voluminous arc‐related rhyolitic eruptions from clusters of caldera complexes, as seen in Snowdonia, North Wales (mid‐Caradoc), and North Island, New Zealand (late Neogene‐Quaternary), are characteristically confined within transient, fault‐controlled corridors in continental crust. New Zealand rhyolitic corridors (Coromandel, Central, Taupo) have developed in response to the spearheading of an oceanic arc into continental crust, combined with subduction rollback‐induced extension during clockwise rotation pivoting around central North Island. Inherited high heat flow from earlier arc magmatism, intracrustal plastic deformation, and mantle‐derived magma ponding and fractionation beneath a less dense, fracture‐toughened crust, all contribute synergistically to crustal fusion and catastrophic volcanism. A similar scenario is suggested for the Snowdonia volcanic corridor where at least six major rhyolitic centres were restricted in space and time (Soudleyan‐Woolstonian). After the climactic Snowdonian eruptions, arc magmatism was extinguished in Wales: a fate predicted for New Zealand rhyolitic volcanism as subduction rollback continues.