A high-resolution 40Ar/39Ar lava chronology and edifice construction history for Ruapehu volcano, New Zealand

Abstract

collapse events; and (6) estimating the long-term eruption rates of composite volcanoes. 2. Geologic setting 2.1. Regional geology Volcanism in central North Island, New Zealand, is associated with westward subduction of oceanic crust of the Pacific Plate at ~45 mm yr-1 beneath the Australian Plate along the Hikurangi Trench system (Fig. 1; Cole and Lewis, 1981; Reyners et al., 2006; DeMets et al., 2010). Most arc-related volcanism is manifested in the Taupo Volcanic Zone (TVZ), a rifting arc active since 2 Ma, which comprises northern and southern segments dominated by andesite-dacite composite cones and a rhyolite-dominated central segment (Wilson et al., 1995). The southern TVZ segment comprises the prominent Tongariro and Ruapehu composite volcanoes as well as several smaller inactive volcanic edifices, which collectively form the Tongariro Volcanic Centre (Fig. 1; Cole, 1978). Rifting and extension in the southern TVZ occurs at a direction of ~115° and a rate of 2.3 ± 1.2 mm yr-1 (Villamor and Berryman, 2006a). This motion is manifested by the 40 km-wide Mount Ruapehu graben, which is bounded by the Rangipo and Raurimu faults to the east and west, respectively, and by the NE-striking Karioi and the ENE-striking Ohakune fault sets to the south (Fig. 1; Villamor and Berryman, 2006b). Ruapehu volcano sits on late Tertiary sediments and Mesozoic basement rocks ('greywacke'). The latter are generally inferred to be part of the Kaweka Terrane, a Jurassic greywacke-argillite sequence of felsic composition that outcrops in the ranges east of the Rangipo Fault (Adams et al., 2009; Lee et al., 2011; Price et al., 2015). An index map of Ruapehu with geographical features referred to throughout the text is provided in Fig. 2. 2.2. Volcanological overview Ruapehu is New Zealand's largest active andesite volcano, with a ~150 km 3 edifice surrounded by a volcaniclastic ring plain of similar volume (Hackett and Houghton, 1989; Gamble et al., 2003). The flanks of the edifice are composed of lava flows and autobreccias

The geomagnetic field intensity in New Zealand: palaeointensities from Holocene lava flows of the Tongariro Volcanic Centre

“…All Ruapehu lava flows targeted in this study share similarities in composition (Price et al 2012;Conway et al 2016) and rock Greve et al 2016). Approximately 12 km north of Ruapehu, and 3 km southwest of site CC is the young cone of Mt Ngauruhoe, and about 3 km north of this the summit of Tongariro.…”

“…The Tongariro Volcanic Centre (TgVC) is a complex of several andesitic to dacitic composite volcanoes, located at the southern extremity of the Taupo Volcanic Zone, with effusive activity extending back at least 350 kyr (Tost & Cronin 2015) and lasting into recent centuries (e.g. Hobden et al 1996;Gamble et al 2003;Eaves et al 2015;Conway et al 2016;Greve et al 2016). Holocene eruptive activity around Ruapehu volcano was dominated by a voluminous pulse of activity lasting more than 1000 yr following a major sector collapse event at c. 10.5 ka (Eaves et al 2015;Conway et al 2016), while only a few effusive lava producing eruptions have occurred since 5 ky BP.…”

“…Hobden et al 1996;Gamble et al 2003;Eaves et al 2015;Conway et al 2016;Greve et al 2016). Holocene eruptive activity around Ruapehu volcano was dominated by a voluminous pulse of activity lasting more than 1000 yr following a major sector collapse event at c. 10.5 ka (Eaves et al 2015;Conway et al 2016), while only a few effusive lava producing eruptions have occurred since 5 ky BP. In contrast, around Mt Tongariro, effusive activity has occurred throughout the past few centuries (Hobden et al 1996(Hobden et al , 2002Hobden 1997;Greve et al 2016).…”

“…1; Greve et al 2016). Each flow is known to be of post-glacial age (<15 ka) due to its position within glacial moraines and millennial scale age-control from 40 Ar/ 39 Ar data (Conway et al 2016) or tephra bracketing. Greve et al (2016) further refined these ages by matching the individ-ual palaeomagnetic directions with the continuous palaeosecular variation (PSV) record of Turner et al (2015), for which a highresolution, radiocarbon based age model is available.…”

The Influence of Plumbing System Structure on Volcano Dimensions and Topography

“…Our results show that the volume erupted by a volcano is a function of the maximum height it can attain and the length of the largest lavas emitted, which in turn is controlled by the lava volume. Detailed chronological and volcano evolution studies (e.g., Clavero et al, ; Conway et al, ; Hildreth & Lanphere, ) show evidence that volcano activity occurs in pulses or cycles of peak activity followed by more quiet stages. Although the model presented here uses a continuous supply of magma and consequently a regular pattern of eruption frequency, it captures the observation that the cone building can be very fast.…”