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The Sources and Origin of Magmas
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
E.V. Sharkov, O.A. Bogatikov, V.I. Kovalenko
The essential feature of K–Na alkali-basalt magmatism is often the presence of mantle xenoliths in lavas and pyroclastics. It is very important that, irrespective of whether this area is located within a continental plate, a back-arc basin or an ocean, the composition of xenoliths is practically identical — the most common here are green spinel, and more rarely garnet–spinel lherzolites and websterites (the “green” or Cr-diopside series), black wehrlites, clinopyroxenites, homblendites and glimmerites as well as megacrysts of Al-titanaugite, kaersutite, phlogopite and sanidine (the “black” or Al-titanaugite series). The detailed characteristics of these formations are described in numerous publications (Kornprobst, 1987; Laz’ko and Sharkov, 1988; etc.), where these rocks have been shown to be generally similar to those observed in the ultramafic complexes of ophiolite assemblages, oceanic peridotites and tectonic blocks of high-pressure ultramafic rocks of fold belts.
Ruapehu and Tongariro stratovolcanoes: a review of current understanding
Published in New Zealand Journal of Geology and Geophysics, 2021
Graham S. Leonard, Rosie P. Cole, Bruce W. Christenson, Chris E. Conway, Shane J. Cronin, John A. Gamble, Tony Hurst, Ben M. Kennedy, Craig A. Miller, Jonathan N. Procter, Leo R. Pure, Dougal B. Townsend, James D. L. White, Colin J. N. Wilson
The TVZ is divisible into three segments. The northern and southern segments are dominated by andesitic volcanism and a central segment is dominated by extraordinarily vigorous rhyolitic volcanism (Wilson et al. 1995). The boundary between the central and southern segments of the TVZ lies just south of Lake Taupo. North of this transition there is a markedly higher rate of mantle melt supply into the central TVZ, leading to a higher heat flow and rates of magmatism and volcanism (Barker et al. 2020). Within the southern segment of the TVZ, mounts Tongariro (including the prominent Ngāuruhoe cone) and Ruapehu are two large andesite-dacite stratovolcano complexes that are central features of Tongariro National Park (TNP; Figures 2 and 3; Townsend et al. 2017). Coinciding and interacting with the TVZ is a similarly-sized and -orientated tectonic structure, the Taupo Rift (Villamor et al. 2017). Ruapehu and Tongariro lie within the southernmost extent of this rift, which is locally represented by nested grabens occupied by the two mountains and their ring-plains.
Taupō: an overview of New Zealand's youngest supervolcano
Published in New Zealand Journal of Geology and Geophysics, 2021
Simon J. Barker, Colin J.N. Wilson, Finnigan Illsley-Kemp, Graham S. Leonard, Eleanor R.H. Mestel, Kate Mauriohooho, Bruce L.A. Charlier
In the Taupō area, post-Whakamaru volcanism covers a broad area (Figures 2C and 11), with multiple dome systems extending well beyond the lake to the south and towards Maroa in the north (Wilson et al. 1986; Sutton et al. 1995; Leonard 2003). Many of these domes have uniquely definable chemical compositions, suggesting that multiple magmatic systems were operating at the time, although some spatially associated domes have geochemical and mineralogical affinities (Sutton et al. 1995; Leonard 2003). At some stage around 100 ka, volcanism at Maroa and in the Taupō-Reporoa Basin declined significantly with <5% of volcanism being <100 ka and most of the younger volcanism being focussed southwards (Leonard 2003; Downs et al. 2014b; Milicich et al. 2020). The boundary between Maroa and Taupō is considered to be both temporal and geographical but in an migrating fashion. Maroa magmas are, however, generally geochemically distinctive when compared to those at Taupō (Sutton et al. 1995; Leonard 2003). As volcanism (and magmatism?) waned at Maroa it appears to have increased towards Taupō. Activity became concentrated around the northern rim of the present Lake Taupō to form the Whakaroa dome complex and Te Kauwae Point domes (Figure 2C). How far this activity extended into the region now occupied by the lake is unknown. The Whakaroa dome complex area may have been active through to at least 54 ka, with the Rotoehu tephra being locally interbedded with associated pyroclastic deposits (Sutton et al. 1995).
Recognition of mid-Paleozoic volcanism in New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2018
Rose E. Turnbull, Quinten H. A. van der Meer, Andy J. Tulloch, Jahandar Ramezani, Martin J. Whitehouse, Tom H. Andersen, Tod E. Waight
The main conclusions of this paper are: Rhyolite clast P81091 from the Permian Pupu Conglomerate (Parapara Group) represents c. 362 Ma volcanism likely associated with S-type Ridge Suite magmatism. Along with the 363 Ma Merrie Granite, this is the oldest episode of Ridge Suite magmatism so far recognised within New Zealand;Dacite clast P42694 from the Cretaceous Seek Cove Formation (Puysegur Group) represents 359 Ma volcanism that was also likely associated with Ridge Suite magmatism;The U–Pb ages of between 359 and 362 Ma of the volcanic clasts reveal that S-type silicic magmatism occurred between the two major episodes of currently recognised S-type plutonism of the Karamea (371–368 Ma) and Ridge (355–340) suites. These results indicate that the current age limits of Ridge Suite magmatism need to be revised, and that this episode of volcanic magmatism likely represents the fore-runner of Ridge Suite activity;