Petrography of the rhyolite lavas of Tarawera Volcanic Complex

Cole, J. W.

doi:10.1080/00288306.1970.10418209

Cited by 20 publications

(7 citation statements)

References 20 publications

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“…Magma bodies with contrasting physical properties may remain separate to produce compositionally bimodal rhyolite deposits such as those of the c. ad 1315 Kaharoa (Leonard et al 2002;Nairn et al 2004), the 17.7 ka Rerewhakaaitu (Cole 1972;Speed et al 2002;Shane et al 2003), and the c. 60 ka Rotoiti eruptive rocks (P. Shane, unpubl. data).…”

Section: Discussionmentioning

confidence: 99%

Reactivation of a rhyolitic magma body by new rhyolitic intrusion before the 15.8 ka Rotorua eruptive episode: implications for magma storage in the Okataina Volcanic Centre, New Zealand

Smith

Shane

Nairn

2004

JGS

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The 15.8 ka Rotorua rhyolite eruptive episode from the Okataina Volcanic Centre comprises a plinian pumice fall deposit followed by the extrusion of two rhyolitic lava domes or flows and their associated block-and-ash flows, with a total volume .1 km 3 (dense rock equivalent). Variations in mineralogy, wholerock, glass and mineral chemistry, and calculated magmatic properties suggest that two distinct rhyolitic magmas were sequentially tapped during the eruption. The first magma erupted (T1) is characterized by low SiO 2 (c. 76.5 wt% in glass), calcic feldspars (An 44 ), magnesian hornblendes (MgO c. 14.45 wt%), clinopyroxene, and high temperatures (c. 835 8C) and fO 2 (1.8-2.1˜FMQ (where FMQ is the fayalitemagnetite-quartz buffer)). The second magma (T2) was more evolved and is characterized by higher SiO 2 (c. 77.4 wt% in glass), Na-rich feldspars (An 24 ), less magnesian hornblendes (MgO c. 11.8 wt%), biotite, and low temperatures (c. 750 8C) and fO 2 (0.65-1.1˜FMQ). Both magmas are homogeneous, but evidence for some magma mingling indicates that they were in contact during eruption. However, there was only a minor degree of hybridization, perhaps reflecting the contrasting temperatures and viscosities of the two magmas. The crystal-rich, poorly vesicular nature of the T2 ejecta indicates that it originated from a cooling, high-level magma chamber that was reactivated by intrusion of hotter, volatile-rich T1 magma. The ponding of rhyolite magmas at shallow depth and their subsequent reactivation by later rhyolitic intrusion may be an important process in the compositional evolution and eruption dynamics of many Okataina Volcanic Centre rhyolite magma bodies.

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Section: Discussionmentioning

confidence: 99%

Reactivation of a rhyolitic magma body by new rhyolitic intrusion before the 15.8 ka Rotorua eruptive episode: implications for magma storage in the Okataina Volcanic Centre, New Zealand

Smith

Shane

Nairn

2004

JGS

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“…For comparison, Ruawahia Dome (near sample collection sites at Tarawera)rhyolitic lavas contain -72-75% glass as well as crystalline quartz (7-10%), plagioclase (13-16%), biotite (1-3%), and magnetite (<1.5%). The composition of the volcanic glass is-75% SiO2, ~4% each Na20 and K20 [Cole, 1970b]. The Al-rich basalts covering the fissure region are 77-80% glass (including pyroxene and magnetite), 16-17% plagioclase feldspar, and ~5% olivine [Cole, 1970c]…”

Section: Summary Of Tarawera Tephramentioning

confidence: 99%

Alteration processes in volcanic soils and identification of exobiologically important weathering products on Mars using remote sensing

Bishop¹,

Fröschl²,

Mancinelli³

1998

J. Geophys. Res.

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Abstract. Determining the mineralogy of the Martian surface material provides information about the past and present environments on Mars which are an integral aspect of whether or not Mars was suitable for the origin of life. Mineral identification on Mars will most likely be achieved through visible-infrared remote sensing in combination with other analyses on landed missions. Therefore, understanding the visible and infrared spectral properties of terrestrial samples formed via processes similar to those thought to have occurred on Mars is essential to this effort and will facilitate site selection for future exobiology missions to Mars. Visible to infrared reflectance spectra are presented here for the fine-grained fractions of altered tephra/lava from the Haleakala summit basin on Maui, the Tarawera volcanic complex on the northern island of New Zealand, and the Greek Santorini island group. These samples exhibit a range of chemical and mineralogical compositions, where the primary minerals typically include plagioclase, pyroxene, hematite, and magnetite. The kind and abundance of weathering products varied substantially for these three sites due, in part, to the climate and weathering environment. The moist environments at Santorini and Tarawera are more consistent with postulated past environments on Mars, while the dry climate at the top of Haleakala is more consistent with the current Martian environment. Weathering of these tephra is evaluated by assessing changes in the leachable and immobile elements, and through detection of phyllosilicates and iron oxide/oxyhydroxide minerals. Identifying regions on Mars where phyllosilicates and many kinds of iron oxides/oxyhydroxides are present would imply the presence of water during alteration of the surface material. Tephra samples altered in the vicinity of cinder cones and steam vents contain higher abundances of phyllosilicates, iron oxides, and sulfates and may be interesting sites for exobiology.

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“…The mineralogy of the distal rhyolite is dominated by plagioclase, quartz and biotite phenocrysts with minor components of opaque minerals, orthopyroxene, hornblende, apatite and zircon (Richnow 1999 ). The crystal content is 23–25 vol.% in the vesicle-free rock (Cole 1970b ; Richnow 1999 ), and glass content approximates 75 vol.%. The plagioclase phenocrysts are typically euhedral to subhedral and fractured (Fig.…”

Section: Micro-scale Texturesmentioning

confidence: 99%

Conduit margin heating and deformation during the AD 1886 basaltic Plinian eruption at Tarawera volcano, New Zealand

et al. 2016

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During explosive eruptions, a suspension of gas and pyroclasts rises rapidly within a conduit. Here, we have analysed textures preserved in the walls of a pyroclastic feeder dyke of the AD 1886 Tarawera basaltic Plinian fissure eruption. The samples examined consist of basaltic ash and scoria plastered onto a conduit wall of a coherent rhyolite dome and a welded rhyolitic dome breccia. We examine the textural evidence for the response of the wall material, built of ∼75 vol.% glass and ∼25 vol.% crystals (pore-free equivalent), to mass movement in the adjacent conduit. In the rhyolitic wall material, we quantify the orientation and aspect ratio of biotite crystals as strain markers of simple shear deformation, and interpret juxtaposed regions of vesiculation and vesicle collapse as evidence of conduit wall heating. Systematic changes occur close to the margin: (1) porosity is highly variable, with areas locally vesiculated or densified, (2) biotite crystals are oriented with their long axis parallel to the margin, (3) the biotites have greater aspect ratios close to the margin and (4) the biotite crystals are fractured. We interpret the biotite phenocryst deformation to result from crystal fracture, rotation and cleavage-parallel bookcase translation. These textural observations are inferred to indicate mechanical coupling between the hot gas-ash jet and the conduit wall and reheating of wall rock rhyolite. We couple these observations with a simple 1D conductive heating model to show what minimum temperature the conduit wall needs to reach in order to achieve a temperature above the glass transition throughout the texturally-defined deformed zone. We propose that conduit wall heating and resulting deformation influences conduit margin outgassing and may enhance the intensity of such large basaltic eruptions.Electronic supplementary materialThe online version of this article (doi:10.1007/s00445-016-1006-7) contains supplementary material, which is available to authorized users.

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Petrography of the rhyolite lavas of Tarawera Volcanic Complex

Cited by 20 publications

References 20 publications

Reactivation of a rhyolitic magma body by new rhyolitic intrusion before the 15.8 ka Rotorua eruptive episode: implications for magma storage in the Okataina Volcanic Centre, New Zealand

Reactivation of a rhyolitic magma body by new rhyolitic intrusion before the 15.8 ka Rotorua eruptive episode: implications for magma storage in the Okataina Volcanic Centre, New Zealand

Alteration processes in volcanic soils and identification of exobiologically important weathering products on Mars using remote sensing

Conduit margin heating and deformation during the AD 1886 basaltic Plinian eruption at Tarawera volcano, New Zealand

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