Incremental growth of a large volume, chemically zoned magma body: a study of the tephra sequence beneath the Rainier Mesa ash flow sheet of the Timber Mountain Tuff

Huysken, Kristin T.; Vogel, Thomas A.; Layer, Paul W.

doi:10.1007/bf00326463

Cited by 10 publications

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“…Gradients in temperature, crystallinity and melt composition are common (e.g. Hildreth, 1981;Fridrich & Mahood, 1987;Vogel et al, 1989;Huysken et al, 1994). Chemical analyses of eruptive products including glass, minerals, pumice, fiamme and bulk tuff have documented compositional gaps in several tuffs and provided evidence for stepwise gradients in pre-eruptive reservoirs; physical (volcanological) evidence is consistent with simultaneous withdrawal of multiple discrete magma volumes during eruption (e.g.…”

Section: Introductionmentioning

confidence: 99%

The Cougar Point Tuff: Implications for Thermochemical Zonation and Longevity of High-Temperature, Large-Volume Silicic Magmas of the Miocene Yellowstone Hotspot

Cathey¹,

Nash²

2004

Journal of Petrology

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The 12Á7EEE10Á5 Ma Cougar Point Tuff in southern Idaho, USA, consists of 10 large-volume (410 2 EEE10 3 km 3 each), high-temperature (800EEE1000 C), rhyolitic ash-flow tuffs erupted from the BruneauEEEJarbidge volcanic center of the Yellowstone hotspot. These tuffs provide evidence for compositional and thermal zonation in pre-eruptive rhyolite magma, and suggest the presence of a long-lived reservoir that was tapped by numerous large explosive eruptions. Pyroxene compositions exhibit discrete compositional modes with respect to Fe and Mg that define a linear spectrum punctuated by conspicuous gaps. Airfall glass compositions also cluster into modes, and the presence of multiple modes indicates tapping of different magma volumes during early phases of eruption. Equilibrium assemblages of pigeonite and augite are used to reconstruct compositional and thermal gradients in the pre-eruptive reservoir. The recurrence of identical compositional modes and of mineral pairs equilibrated at high temperatures in successive eruptive units is consistent with the persistence of their respective liquids in the magma reservoir. Recurrence intervals of identical modes range from 0Á3 to 0Á9 Myr and suggest possible magma residence times of similar duration. Eruption ages, magma temperatures, Nd isotopes, and pyroxene and glass compositions are consistent with a long-lived, dynamically evolving magma reservoir that was chemically and thermally zoned and composed of multiple discrete magma volumes.

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Section: Introductionmentioning

confidence: 99%

The Cougar Point Tuff: Implications for Thermochemical Zonation and Longevity of High-Temperature, Large-Volume Silicic Magmas of the Miocene Yellowstone Hotspot

Cathey¹,

Nash²

2004

Journal of Petrology

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“…Subsequent detailed studies have lead many researchers to the conclusion that different units of the four major eruptions at Timber Mountain represent distinct magma batches [e.g., Schuraytz et al , 1989; Huysken et al , 1994]. Cambray et al [1995] suggested the existence of three distinct magma types that were resident in the magma chamber at the time of eruption.…”

Section: Discussionmentioning

confidence: 99%

Search for the cause‐effect relationship between Miocene silicic volcanism and hydrothermal activity in the unsaturated zone of Yucca Mountain, Nevada: Numerical modeling approach

Dublyansky¹,

Polyansky²

2007

J. Geophys. Res.

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[1] Elevated temperatures of waters that circulated through the thick unsaturated zone of Yucca Mountain and deposited secondary minerals have been explained by conductive heating of the rock mass by a magma body emplaced in association with the activity of the Timber Mountain silicic volcanic center (the ''conductive heating'' conceptual model). The model was evaluated by means of numerical modeling. Two-and three-dimensional simulations of the conductive heat transfer, as well as three-dimensional simulations considering convective flow of water, did not match the target temperature-time ''trajectory'' established from fluid inclusion studies and radiometric dating of secondary minerals at Yucca Mountain. This result was obtained despite the fact that the modeling was nonconservative in that the initial conditions, boundary conditions, and parameters of the models were selected so that they would return higher temperatures and longer cooling times. We conclude that the ''conductive heating'' conceptual model does not appear to constitute a plausible explanation for the circulation in the past of thermal waters (up to 70-90°C, according to fluid inclusion data) in the vadose zone of Yucca Mountain. The finding has important implications for the safety and expected performance of the proposed high-level nuclear waste disposal facility at Yucca Mountain.

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“…The injection of this low-silica, high-temperature magma into the high-silica, low-temperature magma body may have triggered the eruption of the large volume Rainier Mesa ash flow sheet . There is no evidence for a magma with less than 67% silica in the extensive pre-Rainier Mesa tephra sequences [Huysken et al, 1994], and this gives further support to the view that the injection of the more mafic magma resulted in the climactic eruption that produced the large volume ash flow sheet. [Brown 1994].…”

Section: Source Of the Magma Batchesmentioning

confidence: 99%

Origin of compositional heterogeneities in tuffs of the Timber Mountain Group: The relationship between magma batches and magma transfer and emplacement in an extensional environment

Cambray¹,

Vogel²,

Mills³

1995

J. Geophys. Res.

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Compositionally zoned ash flow sheets provide convincing evidence for chemically zoned magma bodies. Most workers have assumed that the high-silica portions of these magma bodies evolved largely by differentiation processes that occurred within the magma chamber. However, chemical heterogeneities within some ash flow sheets are not consistent with these differentiation processes. The chemical variation of pumice fragments in the large volume (>1200 km3), Rainier Mesa ash flow sheet ranges from 55 to 76.3% silica. These pumice fragments occur in three distinct chemical groups. A low-and high-silica group is separated by a compositional gap at about 72% silica, and within the high-silica group there are two distinct populations based on trace element variations. There is little overlap between populations. These three magma types have been resident in same magma chamber at the same time and cannot be produced by any differentiation process of a single magma body. They must reflect discrete magma batches generated in the source area. Furthermore, the lower silica portion (<72% SiOn) of the Rainier Mesa ash flow sheet is chemically distinct from the lower silica portion of the overlying Ammonia Tanks ash flow sheet, even though they erupted within 200,000 years of each other. These ash flow sheets from the SW Nevada volcanic field are associated in time and place with Basin and Range extension, and all models for extension involve detachment surfaces that extend to great depth. A model for the relationship of these compositional heterogeneities and the regional extension involves (1) the generation of magma batches by either continuous melting of the source at different temperatures, or by melting of different sources, (2) the use of faults (shears) as conduits for transport of magma, and (3) the use of a dilatant releasing step on a detachment as storage chamber for the magma. We first address the evidence for separately generated magma batches and then propose a model for their coalescence in a single chamber prior to eruption. [ 1981 ], Baker and McBirney [ 1985], and Trial and Spera [ 1990]). In almost all cases, the inferred trends toward the topCopyright 1995 by the American Geophysical Union. Paper number 95JB00515 0148-0227/95/95JB-00515505.00 of these magma bodies are increasing silica content, together with decreasing temperature and phenocryst content. Because of the occurrence of compositionally distinct pumice fragments within the upper portions of many large-volume ash flow sheets from the Southwest Nevada Volcanic Field, Vogel et al. [ 1987, 1989a], Flood et al. [ 1989a], Schuraytz et al. [1989], and Mills [1991] concluded that discrete compositional layers existed in their parental magma chamber. Regardless of the exact spatial configuration of these compositionally discrete magmas in a chamber, most workers generally accept the fact that large-scale zoning or layering was common. Most of these workers have assumed that an initial magma body evolved, to a large extent, by in situ differentiation from ...

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Incremental growth of a large volume, chemically zoned magma body: a study of the tephra sequence beneath the Rainier Mesa ash flow sheet of the Timber Mountain Tuff

Cited by 10 publications

References 10 publications

The Cougar Point Tuff: Implications for Thermochemical Zonation and Longevity of High-Temperature, Large-Volume Silicic Magmas of the Miocene Yellowstone Hotspot

The Cougar Point Tuff: Implications for Thermochemical Zonation and Longevity of High-Temperature, Large-Volume Silicic Magmas of the Miocene Yellowstone Hotspot

Search for the cause‐effect relationship between Miocene silicic volcanism and hydrothermal activity in the unsaturated zone of Yucca Mountain, Nevada: Numerical modeling approach

Origin of compositional heterogeneities in tuffs of the Timber Mountain Group: The relationship between magma batches and magma transfer and emplacement in an extensional environment

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