Volcanic and sedimentary facies of the Huka Group arc-basin sequence, Wairakei–Tauhara Geothermal Field, New Zealand

Cattell, HJ; Cole, J. W.; Oze, Christopher

doi:10.1080/00288306.2015.1102748

Cited by 12 publications

(25 citation statements)

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“…There is thus no single zircon age determination (regardless of its precision) that can be uniquely defined as representing the onset of the Oruanui magmatic system. Third, during the ~200 kyr period prior to the Oruanui event, large volumes of volcanic products attest to the presence of compositionally unrelated magma systems (such as the NE dome system) active in the Taupo area (Sutton et al 1995;Leonard et al 2010;Cattell et al 2016). The onset of the Oruanui magma system in terms of surface eruptives is around 60 ka (Sutton et al 1995), and the commonality of a ~86-96 ka peak in zircon model ages for the Oruanui and earlier geochemically linked rhyolites (Charlier et al 2005;Wilson and Charlier 2009) suggests a common source that experienced an enhanced episode of cooling and crystallisation at that time.…”

Section: A Cascade Of Events and Their Associated Timescales As Infermentioning

confidence: 99%

A cascade of magmatic events during the assembly and eruption of a super-sized magma body

Allan

Barker

Millet

et al. 2017

Contrib Mineral Petrol

128

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Section: A Cascade Of Events and Their Associated Timescales As Infermentioning

confidence: 99%

A cascade of magmatic events during the assembly and eruption of a super-sized magma body

Allan

Barker

Millet

et al. 2017

Contrib Mineral Petrol

128

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“…Preservation of textures and mineral assemblages have been integral in establishing and refining the lithostratigraphy of Wairakei, Tauhara and several other TVZ fields (Kawerau, Ohaaki, Rotokawa) during their exploration or development. Although substantial changes to rock physical properties (porosity, permeability, compressibility) occur during hydrothermal alteration (Bromley et al, 2013;Lynne et al, 2013;Wyering et al, 2014;Mielke et al, 2015), original and often diagnostic textures in lavas and pyroclastic rocks are normally preserved to some degree (Rosenberg et al, 2009b;Prasetyo et al, 2012;Sanders et al, 2013;Cattell et al, 2016). In examining the material for this study, textures created by eruption and emplacement processes (e.g.…”

Section: Stratigraphic Principles and Nomenclaturementioning

confidence: 97%

“…The rocks are very diverse in lithology and origin, and include voluminous pyroclastic deposits, numerous (mainly rhyolitic) lava extrusions, and various sedimentary strata deposited in periods of volcanic quiescence. Although known throughout central TVZ, rocks of the Huka Group (comprising Huka Falls Formation and Waiora Formation) are best described in the Taupo-Reporoa Basin from outcrop and from subsurface interlayered ~400 m to >2100 m thick sequences in the geothermal fields (Grindley, 1961;Grindley, 1965;Cattell et al, 2016). Some parts of the group are described entirely from geothermal drill holes while others are surficial units with unknown subsurface equivalents.…”

Section: Introduction To the Huka Groupmentioning

confidence: 99%

“…Later work (Steiner, 1977) amalgamated the rhyolite lavas with the other parts of the Formation, and there were subdivisions that differed from Grindley's, which made the two schemes difficult to use together. The most recently published study (Cattell et al, 2016) takes a lithofacies approach in interpreting detailed core descriptions and proposes a three-part subdivision of the Huka Group: an essentially unchanged Huka Falls Formation, a new composite Waiora Volcaniclastic Member and a Waiora Ignimbrite Member that equates to Grindley's Waiora 1 member. Within the major divisions numerous facies are defined and described.…”

Section: Introduction To the Huka Groupmentioning

confidence: 99%

“…type section WK213), given its continuous and nearly complete 600 m core of all units (Rosenberg et al, 2009b;Cattell et al, 2016).…”

Section: Introduction To the Huka Groupmentioning

confidence: 99%

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Volcanic and tectonic perspectives on the age and evolution of the Wairakei-Tauhara geothermal system

Rosenberg¹

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This thesis presents a revision and update of the geology of the Wairakei-Tauhara (WKTH) geothermal system. The research is focussed around the use of U-Pb dating of zircons in key stratigraphic units, coupled with presentation of a robust stratigraphic architecture to establish the timing of major volcanic and volcano-tectonic events, including those that help to constrain the broader scale evolution of the Whakamaru Caldera and Taupo-Reporoa Basin (TRB) and those that initiated or rejuvenated the geothermal system. The present day Wairakei-Tauhara geothermal system is much younger than previously estimated and is now proposed to be a <60 ka manifestation of the previously identified North East (NE) dome magma system. This system is represented by volcanic outputs spanning from contributions to the Mt Tauhara mixed-magma dacite at ~60 ka, to eruption of Puketarata rhyolite at ~16 ka. The earliest TVZ volcanism is represented locally by silicic pyroclastic units that were emplaced prior to 1.8 Ma on a basement now at >3 km depth (beyond the limits of drilled wells). At the Wairakei and Tauhara fields, these pyroclastics are intercalated with greywacke sediment, demonstrating that the area was within a long-lived basin westwards of the North Island axial ranges. At ~1.8 Ma, the earliest dated volcanism at Wairakei began with eruption of andesitic lavas at the eastern margin of TVZ. These lavas were later buried by sediments and rhyolitic pyroclastics, including the locally named Stockyard ignimbrite that is correlated by its U-Pb zircon age spectrum with 1.0 Ma Raepahu Formation ignimbrites erupted from the Mangakino Volcanic Centre. Magmatic activity in the following ~0.3- 0.4 Ma is represented locally by only two WK-TH volcanic episodes (at 0.95 Ma and 0.73 Ma). Wairakei well stratigraphy also highlights a major hiatus in local volcanism and deposition until the ~0.35 Ma Whakamaru eruptions. These and associated structural collapse were the events that may have initiated frequent volcanic and volcanotectonic episodes in the Wairakei-Tauhara area. Syn-eruptive piecemeal collapse of the caldera is inferred to have created the fault pathways for small batches of crystal-poor rhyolite, probably derived from a Whakamaru-like magma system, to intrude and erupt in much the same locations in the WK-TH area. This post-Whakamaru period (0.31 Ma until 0.22 Ma), overlaps with the age span of the majority of surficial rhyolitic volcanism in the Maroa Volcanic Centre, north and northwest of the WK-TH area. The Taupo-Reporoa Basin evolved in major volcano-tectonic episodes beginning around 0.35 Ma. In the south, displacement of Whakamaru Group ignimbrite across an elongate, central graben-like structure between the Wairakei and Tauhara fields is explained by 0.9-1.7 km subsidence of large NE-SW trending fault blocks, during piecemeal collapse of the Whakamaru Caldera. Further local collapse is proposed, which was nearly contemporaneous with 0.31 Ma eruptions that formed a ~10 x 12 km block faulted, newly recognised Waiora caldera and generated >30 km³ of Waiora Formation ignimbrites that syn-eruptively filled the new caldera. Rhyolite lava eruptions also starting at ~0.31 Ma on the eastern margin of the Tauhara Field and in the Wairakei Field, were the first of many spatially overlapping lavas and intercalated local pyroclastic units collectively mapped as the Waiora Formation. U-Pb and U-Th dating of zircons, zircon growth textures revealed by cathodoluminescence, and whole rock REE geochemistry are integrated with petrography to outline overlapping compositions of the lavas, several of which are also analytically indistinguishable in age. Correlations between Waiora Formation rhyolitic lavas and ignimbrites are equivocal with the available data, but the geochemistry suggests that early Waiora Formation ignimbrites may have been derived from a Whakamaru-like magma source that was distinct from contemporaneous Maroa rhyolite lavas. Infilling and subsidence of the Waiora caldera continued at varied rates until ~0.22 Ma. After 0.22 Ma there was a hiatus in volcanism in the local WK-TH area, during which lacustrine sediments accumulated in the local part of Lake Huka at ~1 mm/y. These fine grained Huka Falls Formation deposits became the impermeable cap rock of the modern WK-TH geothermal system. Volcanism did not wholly cease in the local area, or elsewhere in the TRB, however. There were shallow intrusions and subaerial dome extrusions of rhyolite at ~0.14-0.12 Ma, and at ~0.1 Ma there was the subaqueous eruption of middle Huka Falls Formation rhyolite. The new U-Pb ages reflect magma systems active in the local area at least at 1.8 Ma, 0.95 Ma, and 0.73 Ma, but there is no evidence of any associated geothermal system during one of these episodes. The Whakamaru eruptions and collapse episodes may have initiated the first geothermal system in the WK-TH area. The overlapping ages of Waiora Formation rhyolites, and spatial clustering beneath the Wairakei Field, show that underlying magmatism might have supported a geothermal system in more or less the same location at numerous times during the past ~0.3 Ma. Previously, the geothermal system was inferred to have been active since ~0.5 Ma, but in its modern state, the system is now interpreted to have begun at ~60 ka and has been sustained since then by the presence of an underlying NE dome magma system.

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Subaqueous felsic volcanic sequence and its contribution to the ancient alkaline lacustrine deposits in the Mahu Sag, Junggar Basin, NW China

Zhang

et al. 2023

Geological Journal

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Subaqueous eruptions alter the chemical conditions of the lake by intensifying the interaction between hot volcanic rocks and water, resulting in the exchange of alkalis. The lower part of the Fengcheng Formation in the Mahu Sag, NW China, has abundant rhyolitic welded tuff and related pyroclastic deposits, which were deposited under ancient alkaline lacustrine deposits of the Fengcheng Formation. Despite this, the effect of the eruption process on the formation of the alkali lake remains unclear. To gain a better understanding of the eruptive behaviour and emplacement processes, detailed drilling core descriptions, microscopic observations, and interpretations of textural characteristics of rhyolitic welded tuff units and adjacent volcano‐sedimentary associations have been conducted. The rhyolitic welded tuff can be categorized into seven lithofacies units based on the degree of welding, devitrification characteristics, pore development, and filling characteristics. The age of eruption was determined through zircon U–Pb dating of the rhyolitic welded tuff, revealing it to be approximately 300 Ma, thereby providing constraints on the deposition time of alkaline lacustrine deposits. Mudstones that encase the welded tuff unit and quenched structures such as perlitic fractures, quench cracks of spherulite and lithophysae, and chalcedony spherules indicate that the welded tuff unit was formed through subaqueous eruption. Alkali fractionation (sodium and potassium) occurs in the spherulite and lithophysae zone and at the top condensation boundary, demonstrating that the subaqueous eruption process significantly enhanced devitrification and hydration, causing sodium to escape from the welded tuff and released into the lake water as sodium ions. The rhyolitic welded tuff provides evidence of the evolution of a subaqueous felsic eruption where the water‐rock reaction played a fundamental role in alkalizing the lake by providing the lake with sodium ions in Mahu Sag.

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Volcanic and sedimentary facies of the Huka Group arc-basin sequence, Wairakei–Tauhara Geothermal Field, New Zealand

Cited by 12 publications

References 66 publications

A cascade of magmatic events during the assembly and eruption of a super-sized magma body

A cascade of magmatic events during the assembly and eruption of a super-sized magma body

Volcanic and tectonic perspectives on the age and evolution of the Wairakei-Tauhara geothermal system

Subaqueous felsic volcanic sequence and its contribution to the ancient alkaline lacustrine deposits in the Mahu Sag, Junggar Basin, NW China

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