Magma batches in the Timber Mountain magmatic system, Southwestern Nevada Volcanic Field, Nevada, USA

Mills, J. G.; Saltoun, Benjamin W.; Vogel, Thomas A.

doi:10.1016/s0377-0273(97)00015-2

Cited by 44 publications

(22 citation statements)

References 60 publications

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“…Lipman 1971;Hildreth 1981) or batches within some eruptive units (Mills et al 1997). Some units display systematic trends of increasing T and fO 2 toward the top of the unit, reflecting an inverted magmatic gradient.…”

Section: Variability Within Eruptive Eventsmentioning

confidence: 95%

Correlation of rhyolitic pyroclastic eruptive units from the Taupo volcanic zone by Fe-Ti oxide compositional data

Shane¹

1998

Bulletin of Volcanology

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Grain-specific analyses of Fe-Ti oxides and estimates of eruption temperature (T) and oxygen fugacity (fO 2 ) have been used to fingerprint rhyolitic fall and flow deposits that are important for tephrostratigraphic studies in and around the Taupo volcanic zone of North Island, New Zealand. The analysed Fe-Ti oxides commonly occur in the rims of orthopyroxene crystals and appear to reflect equilibrium immediately prior to eruption because of geochemical correlation with the co-existing glass phase. The composition of the spinel phase is particularly diagnostic of eruptive centre for post-65 ka events and can be used to distinguish many tephra beds from the same volcano. The 29 different units examined were erupted over a wide range in T (690-990°C) and D log fO 2 (-0.1 to 2.0). These parameters are closely related to the mafic mineral assemblage, with hydrous mineral-bearing units displaying higher fO 2 . Such trends are superimposed on larger differences in fO 2 that are related to eruptive centre. At any given temperature, all post-65 ka Okataina centre tephra have higher fO 2 values than post-65 ka Taupo centre tephra. This provides a useful criterion for identifying the volcanic source. There are no temporal T and fO 2 trends in the tephra record; over intervals >20 ka, however, tephra sequences from Taupo centre form characteristic T-fO 2 buffer trends mirroring the glass chemistry. Individual eruptive events display uniform spinel and rhombohedral phase compositions and thus narrow ranges in T (± <20°C) and log fO 2 (± <0.5), allowing these features to identify individual magma batches. These criteria can help distinguish tephra deposits of similar bulk or glass composition that originated from the same volcano. Distal fall deposits record the same T-fO 2 conditions as the proximal ignimbrite and enable distal-proximal correlation. Lateral and vertical compositional and T-fO 2 variability displayed in large volume (>100 km 3 ) ignimbrites, such as the Oruanui, Rotoiti and Ongatiti, is similar to that found in a single pumice clast and thus mainly reflects analytical error; however, thermal gradients of ca. 50°C may occur in some units.

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Section: Variability Within Eruptive Eventsmentioning

confidence: 95%

Correlation of rhyolitic pyroclastic eruptive units from the Taupo volcanic zone by Fe-Ti oxide compositional data

Shane¹

1998

Bulletin of Volcanology

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“…Models for generation of chemical gradients within voluminous rhyolites erupted as ignimbrites have ranged from differentiation within single magma chambers (e.g., Hildreth 1979;Mahood 1981;Michael 1983;Cameron 1984;Streck and Grunder 1997) to juxtaposition of separate rhyolite magma batches shortly prior to eruption (e.g., Mills et al 1997). Workers who proposed models operating in single reservoirs have invoked a wide variety of differentiation processes, although mineral-liquid equilibria have regained overwhelming acceptance in recent years as the dominating process to induce elemental enrichment or depletion patterns.…”

Section: Fig 5 Microprobe Traverse Data For Clinopyroxene and Alkalimentioning

confidence: 99%

Phenocryst-poor rhyolites of bimodal, tholeiitic provinces: the Rattlesnake Tuff and implications for mush extraction models

Streck

Grunder

2007

Bull Volcanol

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“…This interpretation is not unique to the Tiribí Tuff. There is petrologic evidence (reviewed in Mills et al 1997;Eichelberger et al 2000) that many magma bodies may have had distinct compositional groups that cannot be related to each other by fractionation processes alone.…”

Section: Discussionmentioning

confidence: 99%

“…Based on the map of Tournon and Alvarado (1997) and amplified further by Eichelberger and co-workers (Eichelberger and Izbekov 2000;Eichelberger et al 2000). There is petrologic evidence, reviewed in Mills et al (1997) and Eichelberger et al (2000), that many magma bodies may have had distinct compositional groups that cannot be related by crystal fractionation from a homogeneous magma body. Chemically distinct magma batches that are unrelated by fractionation can result from melting and extraction processes (Sawyer 1994).…”

Section: Introductionmentioning

confidence: 99%

Origin of silicic volcanic rocks in Central Costa Rica: a study of a chemically variable ash-flow sheet in the Tiribí Tuff

Hannah

Vogel

Patino

et al. 2002

Bulletin of Volcanology

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Chemical heterogeneities of pumice clasts in an ash-flow sheet can be used to determine processes that occur in the magma chamber because they represent samples of magma that were erupted at the same time.The dominant ash-flow sheet in the Tiribí Tuff contains pumice clasts that range in composition from 55.1 to 69.2 wt% SiO 2 . It covers about 820 km 2 and has a volume of about 25 km 3 dense-rock equivalent (DRE). Based on pumice clast compositions, the sheet can be divided into three distinct chemical groupings: a low-silica group (55.1-65.6 wt% SiO 2 ), a silicic group (66.2-69.2 wt% SiO 2 ), and a mingled group (58.6-67.7 wt% SiO 2 ; all compositions calculated 100% anhydrous). Major and trace element modeling indicates that the lowsilica magma represents a mantle melt that has undergone fractional crystallization, creating a continuous range of silica content from 55.1-65.6 wt% SiO 2 . Eu/Eu*, MREE, and HREE differences between the two groups are not consistent with crystal fractionation of the low-silica magma to produce the silicic magma. The low-silica group and the silicic group represent two distinct magmas, which did not evolve in the same magma chamber. We suggest that the silicic melts resulted from partial melting of relatively hot, evolved calc-alkaline rocks that were previously emplaced and ponded at the base of an over-thickened basaltic crust. The mingled group represents mingling of the two magmas shortly before eruption. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.

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Magma batches in the Timber Mountain magmatic system, Southwestern Nevada Volcanic Field, Nevada, USA

Cited by 44 publications

References 60 publications

Correlation of rhyolitic pyroclastic eruptive units from the Taupo volcanic zone by Fe-Ti oxide compositional data

Correlation of rhyolitic pyroclastic eruptive units from the Taupo volcanic zone by Fe-Ti oxide compositional data

Phenocryst-poor rhyolites of bimodal, tholeiitic provinces: the Rattlesnake Tuff and implications for mush extraction models

Origin of silicic volcanic rocks in Central Costa Rica: a study of a chemically variable ash-flow sheet in the Tiribí Tuff

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