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Abstract. The largest tract of ultrahigh-pressure rocks, the Dabie-Hong'an area of China, was exhumed from 125 km depth by a combination of normal-sense shear from beneath the hanging wall Sino-Korean craton, southeastward thrusting onto the footwall Yangtze craton, and orogenparallel eastward extrusion. Prior to exhumation the UHP slab extended into the mantle a downdip distance of 125-200 km at its eastern end, whereas it was subducted perhaps only 20-30 km at its far western end ~200 km away. Structural reconstructions imply that the slab was > 10 km thick. In the Hong'an area (Figures 1 and 2), blueschist-facies rocks are more widespread, and a distinct eclogite-retrogressed-toamphibolite unit has been mapped, in addition to quartz eclogite and coesite eclogite. Also, a wider variety of Paleozoic metamorphic rocks crop out in E-W trending fault-bounded units

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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

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