Paleomagnetic evidence for cold emplacement of eruption-fed density current deposits beneath an ancient summit glacier, Tongariro volcano, New Zealand

Leonard, Graham; Ohneiser, Christian; White, James D. L.; Townsend, Dougal; Leonard, Graham S.

doi:10.1016/j.epsl.2019.07.004

Cited by 9 publications

(11 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Group 3 clasts did not demagnetize until heated to medium and high temperatures (HTs; 250°C–500°C), so they likely contain magnetic grains of similar size or composition and almost no magnetic grains with low‐intermediate unblocking temperatures (possibly magnetite and Ti‐poor magnetite; e.g., R. P. Cole et al., 2019). For these samples, it is not possible to identify a clear T r .…”

Section: Discussionmentioning

confidence: 99%

Deposit‐Derived Block‐and‐Ash Flows: The Hazard Posed by Perched Temporary Tephra Accumulations on Volcanoes; 2018 Fuego Disaster, Guatemala

et al. 2022

View full text Add to dashboard Cite

Pyroclastic density currents (PDCs) are flowing mixtures of hot gas and volcanic particles. They are the dominant single cause of fatalities around volcanoes (S. K. Brown et al., 2017) and can be generated by the fountaining of eruption columns, lateral blasts, and growing lava domes (Branney et al., 2021;Druitt, 1998). They transport large volumes of hot, ash-rich pyroclastic debris rapidly across the landscape, and span a wide range of scales, particle concentrations and grain-sizes (Branney & Kokelaar, 2002). A key factor in the hazard they present is the distance they travel (the "runout distance") over a given topography, and this is significantly affected by the current's mass flux at the source (e.g., Bursik & Woods, 1996; Shimuzu et al., 2019;Williams et al., 2014). In many cases, it can be assumed that the mass flux of the pyroclastic current derives directly from the vent discharge rate (mass flux) of the eruption (e.g., Roche et al., 2021;Sparks et al., 1997). However, PDCs are known to entrain loose substrate

show abstract

Section: Discussionmentioning

confidence: 99%

Deposit‐Derived Block‐and‐Ash Flows: The Hazard Posed by Perched Temporary Tephra Accumulations on Volcanoes; 2018 Fuego Disaster, Guatemala

et al. 2022

View full text Add to dashboard Cite

show abstract

“…GNS Science photo by Dougal Townsend. (Conway et al 2016;Townsend et al 2017;Cole et al 2018Cole et al , 2019Pure et al 2020). C: Chronological variations in K 2 O for Tongariro (dark crosses) and Ruapehu (red boxes and crosses).…”

Section: Ring-plains: Pyroclastic Lahar and Sectorcollapse Depositsmentioning

confidence: 99%

“…B: Benthic δ 18 O global climate proxy record fromLisiecki and Raymo (2005) with approximate positions of Marine Isotope Stage (MIS) periods shown. Blue shading indicates periods of valley-filling glaciers and ephemeral summit ice caps on Tongariro and Ruapehu as inferred by field geology(Conway et al 2016;Townsend et al 2017;Cole et al 2018Cole et al , 2019Pure et al 2020). C: Chronological variations in K 2 O for Tongariro (dark crosses) and Ruapehu (red boxes and crosses).…”

mentioning

confidence: 99%

Ruapehu and Tongariro stratovolcanoes: a review of current understanding

Leonard

Christenson

et al. 2021

New Zealand Journal of Geology and Geophysics

Self Cite

View full text Add to dashboard Cite

Ruapehu (150 km 3 cone, 150 km 3 ring-plain) and Tongariro (90 km 3 cone, 60 km 3 ring-plain) are iconic stratovolcanoes, formed since ∼230 and ∼350 ka, respectively, in the southern Taupo Volcanic Zone and Taupo Rift. These volcanoes rest on Mesozoic metasedimentary basement with local intervening Miocene sediments. Both volcanoes have complex growth histories, closely linked to the presence or absence of glacial ice that controlled the distribution and preservation of lavas. Ruapehu cone-building vents are focused into a short NNE-separated pair, whereas Tongariro vents are more widely distributed along that trend, the differences reflecting local rifting rates and faulting intensities. Both volcanoes have erupted basaltic andesite to dacite (53-66 wt.% silica), but mostly plagioclase-two pyroxene andesites from storage zones at 5-10 km depth. Erupted compositions contain evidence for magma mixing and interaction with basement rocks. Each volcano has an independent magmatic system and a growth history related to long-term (>10 4 years) cycles of mantlederived magma supply, unrelated to glacial/interglacial cycles. Historic eruptions at both volcanoes are compositionally diverse, reflecting small, dispersed magma sources. Both volcanoes often show signs of volcanic unrest and have erupted with a wide range of styles and associated hazards, most recently in 2007 (Ruapehu) and 2012 (Tongariro).

show abstract

“…Crucially, the presence and absence of ice masses have been demonstrated elsewhere to control the locations at which lavas are preserved (Lescinsky and Sisson, 1998;Lescinsky and Fink, 2000;Conway et al, 2015). At Tongariro, the applicability of lava-ice models is corroborated by explicit textural evidence for lava-ice interaction, in the form of cooling structures preserved on the peripheries of lavas (Cole et al, 2018(Cole et al, , 2019this thesis). The absence of contemporaneous glacial and volcanic interplay as part of Tongariro's existing edifice construction model suggests that interpreted vent locations, lava sequencing (and consequential geochemical sequencing), geomorphological evolution, estimated lava volumes and eruption rates are all open to re-examination.…”

Section: Previous Edifice Studies Of Tongariromentioning

confidence: 96%

“…Explicit evidence for lava-ice interaction at previously-glaciated stratovolcanoes indicates that the presence and absence of ice strongly controls where erupted material can and cannot be preserved (Lescinsky and Sisson, 1998;Conway et al, 2015;Vallance and Sisson, 2017). On Earth, glaciovolcanic deposits have been identified on all continents except Australia (Edwards et al, 2015) but are potentially under-recognised at many stratovolcanoes around the world, as demonstrated by the recent recognition of previously unrecognised glaciovolcanic deposits on Tongariro volcano (Townsend et al, 2017;Cole et al, 2018Cole et al, , 2019.…”

Section: Stratovolcano Geomorphologymentioning

confidence: 99%

The volcanic and magmatic evolution of Tongariro volcano, New Zealand

Pure¹

View full text Add to dashboard Cite

<p>Detailed mapping studies of Quaternary stratovolcanoes provide critical frameworks for examining the long-term evolution of magmatic systems and volcanic behaviour. For stratovolcanoes that have experienced glaciation, edifice-forming products also act as climate-proxies from which ice thicknesses can be inferred at specific points in time. One such volcano is Tongariro, which is located in the southern Taupō Volcanic Zone of New Zealand’s North Island. This study presents the results of new detailed mapping, geochronological and geochemical investigations on edifice-forming materials to reconstruct Tongariro’s volcanic and magmatic history which address the following questions: (1) Does ice coverage on stratovolcanoes influence eruptive rates and behaviour (or record completeness)? (2) What is the relationship between magmatism, its expression (i.e. volcanism) and external but related processes such as tectonics? (3) How are intermediate-composition magmas assembled and what controls their diversity? (4) What are the relative proportions of mantle-derived and crust-derived materials in intermediate composition arc magmas? (5) Do genetic relationships exist between andesite and rhyolite magmas in arc settings? Samples from 250 new field localities in under-examined areas of Tongariro were analysed for major oxide, trace element and Sr-Nd-Pb isotope compositions. Analyses were performed on whole-rock, groundmass and xenolith samples. The stratigraphic framework for these geochemical data was established from field observations and 29 new 40Ar/39Ar age determinations, which were synthesised with volume estimates and petrographic observations for all Tongariro map units. Mapping results divide Tongariro into 36 distinct map units (at their greatest level of subdivision) which were organised into formations and constituent members. New 40Ar/39Ar age determinations reveal continuous eruptive activity at Tongariro from at least 230 ka to present, including during glacial periods. This adds to the discovery of an inlier of old basaltic-andesite (512 ± 59 ka) on Tongariro’s NW sector that has an unclear source vent. Hornblende-phyric andesite boulders, mapped into the Tupuna Formation (new), yield the oldest 40Ar/39Ar age determination (304 ± 11 ka) for materials confidently attributed to Tongariro. Tupuna Formation andesites are correlated with Turakina Formation debris flows that were deposited between 349 to 309 ka in the Wanganui Basin, ~100 km south of Tongariro, which indicates that Ruapehu did not exist at this time, at least not in its current form. Tongariro has a total edifice volume of ~90 km3, 19 km3 of which is represented by exposed mapped units. The total ringplain volume immediately adjacent to Tongariro contains ~60 km3 of material. The volume of exposed glacial deposits are no more than 1 km3. During periods of major ice coverage, edifice-building rates on Tongariro were only 17-21 % of edifice-building rates during warmer climatic periods. Because shifts in edifice-building rates do not coincide with changes in erupted compositions, differences in edifice-building rates reflect a preservation bias. Materials erupted during glacial periods were emplaced onto ice masses and conveyed to the ringplain as debris, which explains reduced preservation rates at these times. MgO concentrations in Tongariro stratigraphic units with ages between 230 and 0 ka display successive and irregular cyclicity that occurs over ~10-70 kyr intervals, which reflect episodes of enhanced mafic magma replenishment. During these cycles, more rapid (≤10 kyr) increases in MgO concentrations to ≥5-9 wt% are followed by gradual declines to ~2-5 wt%, with maxima at ~230, ~160, ~117, ~88, ~56, ~35, ~17.5 ka and during the Holocene. Contemporaneous variations in Tongariro and Ruapehu magma compositions (e.g. MgO, Rb/Sr, Sr-Nd-Pb isotope ratios) for the 200-0 ka period coincide with reported zircon growth model-ages in Taupō magmas. This contemporaneity reflects regional tectonic processes that have externally regulated and synchronised the timings of elevated mafic replenishment episodes versus periods of prolonged crustal residence at each of these volcanoes. Isotopic Sr-Nd-Pb data from metasedimentary xenoliths, groundmass separates and whole-rock samples indicate that two or three separate metasedimentary terranes (in the upper 15 km of the crust) were assimilated into Tongariro magmas. These are the Kaweka terrane and the Waipapa or Pahau terranes (or both). Subhorizontal juxtapositioning of these terranes is indicated by the coexistence of multiple terranes in the same eruptive units. Paired whole-rock and groundmass (interstitial melt) samples have effectively equal Sr-Nd-Pb isotope ratios for the complete range of Tongariro compositions. Despite intra-crystal isotopic heterogeneities that are likely widespread, the new data show that crystal fractionation and assimilation occur in approximately equal balance for essentially all Tongariro eruptives. Assimilated country rock accounts for 22-31 wt% of the average Tongariro magma. Initial evolution from a Kakuki basalt-type to a Tongariro Te Rongo Member basaltic-andesite reflects the addition of 17 % assimilated metasedimentary basement with a mass assimilation rate/mass crystal fractionation rate ratio—a.k.a. ‘r value’ of 1.8-3.5. Subsequent evolution from a Te Rongo Member basaltic-andesite to other Tongariro eruptive compositions represents 5-14 % more assimilated crust (r values of ~0.1-1.0). Magma evolution from high (>1) to lower (0.1-1.0) r values can explain the dearth of andesitic melt inclusions in (bulk) andesite magmas observed globally. High relative assimilation rates characterise rapid evolution from basalt to basaltic-andesite bulk compositions which contain andesitic interstitial melts. Thus, andesitic melt inclusions have a reduced chance of being preserved in crystals which can explain their low representation in global datasets.</p>

show abstract

Paleomagnetic evidence for cold emplacement of eruption-fed density current deposits beneath an ancient summit glacier, Tongariro volcano, New Zealand

Cited by 9 publications

References 32 publications

Deposit‐Derived Block‐and‐Ash Flows: The Hazard Posed by Perched Temporary Tephra Accumulations on Volcanoes; 2018 Fuego Disaster, Guatemala

Deposit‐Derived Block‐and‐Ash Flows: The Hazard Posed by Perched Temporary Tephra Accumulations on Volcanoes; 2018 Fuego Disaster, Guatemala

Ruapehu and Tongariro stratovolcanoes: a review of current understanding

The volcanic and magmatic evolution of Tongariro volcano, New Zealand

Contact Info

Product

Resources

About