Petrological and Mineralogical Variations in 2500-2000 yr B.P. Lava Flows, Craters of the Moon Lava Field, Idaho

Stout, Mavis Z.; Nicholls, J.; Kuntz, Mel A.

doi:10.1093/petrology/35.6.1681

Cited by 30 publications

(42 citation statements)

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“…Mineral compositions in the Snake River Plains basalts Stout and Nicholls 1977;Stout et al 1994;Honjo andLeeman 1987, Putirka et al 2003;and Christiansen's (2005) unpublished data for Kimama and Rocky Buttes) suggest that the lavas erupted at temperatures near 1,200°C and were crystallizing on or below the QFM oxygen buffer. The rhyolites of the Snake River plain likewise crystallized at low oxygen fugacities near QFM and at high temperatures for rhyolites of about 1,050°C to as low as 850°C (e.g., Honjo 1990;Hildreth 1981;Perkins et al 1998;Cathey and Nash 2004).…”

Section: Intensive Parametersmentioning

confidence: 99%

“…However, the Nd isotopic ratios of rhyolites that lie on the Craters of the Moon-Cedar Butte trend (from Cedar Butte, Unnamed Butte, East Butte and Big Southern Butte) are the highest of all the rhyolites (Fig. 7), suggesting that assimilation of upper crustal materials was not required for the generation of the silicic rocks on the Craters of the Moon-Cedar Butte trend (Stout et al 1994;McCurry et al 2007). …”

Section: Craters Of the Moon-cedar Butte Trendmentioning

confidence: 99%

“…Augite is abundant in the groundmass along with plagioclase, magnetite, ilmenite, apatite, and olivine Stout and Nicholls 1977). Ferrobasalt to ferrolatite lavas in the Craters of the Moon volcanic field contain phenocrysts of clinopyroxene, apatite, and magnetite in the more silicic members of the suite Stout et al 1994). …”

Section: Petrography and Mineralogymentioning

confidence: 99%

“…As concluded by , these elemental variations are consistent with fractionation of plagioclase, apatite, olivine, clinopyroxene, magnetite (Crrich). Since clinopyroxene crystallizes at moderately high pressures (Thompson 1975) in Snake River Plain basalt, this trend may only form by mid-crustal differentiation Stout et al 1994). Oxide fractionation probably promotes the silica enrichment trend.…”

Section: Craters Of the Moon-cedar Butte Trendmentioning

confidence: 99%

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Contrasting origins of Cenozoic silicic volcanic rocks from the western Cordillera of the United States

2007

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Two fundamentally different types of silicic volcanic rocks formed during the Cenozoic of the western Cordillera of the United States. Large volumes of dacite and rhyolite, mostly ignimbrites, erupted in the Oligocene in what is now the Great Basin and contrast with rhyolites erupted along the Snake River Plain during the Late Cenozoic. The Great Basin dacites and rhyolites are generally calc-alkaline, magnesian, oxidized, wet, cool (<850°C), Sr-and Al-rich, and Fe-poor. These silicic rocks are interpreted to have been derived from mafic parent magmas generated by dehydration of oceanic lithosphere and melting in the mantle wedge above a subduction zone. Plagioclase fractionation was minimized by the high water fugacity and oxide precipitation was enhanced by high oxygen fugacity. This resulted in the formation of Si-, Al-, and Sr-rich differentiates with low Fe/Mg ratios, relatively low temperatures, and declining densities. Magma mixing, large proportions of crustal assimilation, and polybaric crystal fractionation were all important processes in generating this Oligocene suite. In contrast, most of the rhyolites of the Snake River Plain are alkaline to calc-alkaline, ferroan, reduced, dry, hot (830-1,050°C), Sr-and Al-poor, and Nb-and Fe-rich. They are part of a distinctly bimodal sequence with tholeiitic basalt. These characteristics were largely imposed by their derivation from parental basalt (with low f H 2 O and low f O 2 ) which formed by partial melting in or above a mantle plume. The differences in intensive parameters caused early precipitation of plagioclase and retarded crystallization of Fe-Ti oxides. Fractionation led to higher density magmas and mid-crustal entrapment. Renewed intrusion of mafic magma caused partial melting of the intrusive complex. Varying degrees of partial melting, fractionation, and minor assimilation of older crust led to the array of rhyolite compositions. Only very small volumes of distinctive rhyolite were derived by fractional crystallization of Fe-rich intermediate magmas like those of the Craters of the Moon-Cedar Butte trend.

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Section: Intensive Parametersmentioning

confidence: 99%

Section: Craters Of the Moon-cedar Butte Trendmentioning

confidence: 99%

Section: Petrography and Mineralogymentioning

confidence: 99%

Section: Craters Of the Moon-cedar Butte Trendmentioning

confidence: 99%

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Contrasting origins of Cenozoic silicic volcanic rocks from the western Cordillera of the United States

2007

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“…Top right panel illustrates coexisting phenocryst assemblages in lavas from Cedar Butte; line widths are proportional to the relative abundances of phenocrysts. Abbreviations are from Kretz 1983 (Ch chevkinite) 1982b; Menzies et al 1984;Hildreth et al 1991;Kuntz et al 1992;Stout et al 1994;Putirka et al 2003a;Whitaker et al 2007). …”

Section: Introductionmentioning

confidence: 99%

Genesis of post-hotspot, A-type rhyolite of the Eastern Snake River Plain volcanic field by extreme fractional crystallization of olivine tholeiite

et al. 2007

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Rhyolites occur as a subordinate component of the basalt-dominated Eastern Snake River Plain volcanic field. The basalt-dominated volcanic field spatially overlaps and post-dates voluminous late Miocene to Pliocene rhyolites of the Yellowstone-Snake River Plain hotspot track. In some areas the basalt lavas are intruded, interlayered or overlain by~15 km 3 of cryptodomes, domes and flows of high-silica rhyolite. These post-hotspot rhyolites have distinctive A-type geochemical signatures including high whole-rock FeO tot /(FeO tot +MgO), high Rb/ Sr, low Sr (0.5-10 ppm) and are either aphyric, or contain an anhydrous phenocryst assemblage of sodic sanidine ± plagioclase + quartz > fayalite + ferroaugite > magnetite > ilmenite + accessory zircon + apatite + chevkinite. Nd-and Sr-isotopic compositions overlap with coeval olivine tholeiites (ɛ Nd =−4 to −6; 87 Sr/ 86 Sr i =0.7080-0.7102) and contrast markedly with isotopically evolved Archean country rocks. In at least two cases, the rhyolite lavas occur as cogenetic parts of compositionally zoned (~55-75% SiO 2 ) shield volcanoes. Both consist dominantly of intermediate composition lavas and have cumulative volumes of several 10's of km 3 each. They exhibit two distinct, systematic and continuous types of compositional trends:(1) At Cedar Butte (0.4 Ma) the volcanic rocks are characterized by prominent curvilinear patterns of wholerock chemical covariation. Whole-rock compositions correlate systematically with changes in phenocryst compositions and assemblages. (2) At Unnamed Butte (1.4 Ma) the lavas are dominated by linear patterns of whole-rock chemical covariation, disequilibrium phenocryst assemblages, and magmatic enclaves. Intermediate compositions in this group resulted from variable amounts of mixing and hybridization of olivine tholeiite and rhyolite parent magmas. Interestingly, models of rhyolite genesis that involve large degrees of melting of Archean crust or previously consolidated mafic or silicic Tertiary intrusions do not produce observed ranges of Nd-and Sr-isotopes, extreme depletions in Sr-concentration, and cogenetic spectra of intermediate rock compositions for both groups. Instead, least-squares mass-balance, energyconstrained assimilation and fractional crystallization modeling, and mineral thermobarometry can explain rhyolite production by 77% low-pressure fractional crystallization of a basaltic trachyandesite parent magma (~55% SiO 2 ), accompanied by minor (0.03-7%) assimilation of Archean upper crust. We present a physical model that links the rhyolites and parental intermediate magmas to primitive olivine tholeiite by fractional crystallization. Assimilation, recharge, mixing and fractional melting occur to limited degrees, but are not essential parts of the rhyolite formation process.

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Reexamining the potential to classify lava flows from the fractality of their margins

Schaefer

Hamilton

Neish

et al. 2021

Preprint

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Can fractal analysis of a lava flow's margin enable classification of the lava's morphologic type (e.g., pāhoehoe)? Such classifications would provide insights into the rheology and dynamics of the flow when it was emplaced. The potential to classify lava flows from remotely-sensed data would particularly benefit the analysis of flows that are inaccessible, including flows on other planetary bodies. The technique's current interpretive framework depends on three assumptions: (1) measured margin fractality is scale-invariant; (2) morphologic types can be uniquely distinguished based on measured margin fractality; and (3) modification of margin fractality by topography, including substrate slope and confinement, would be minimal or independently recognizable. We critically evaluate these assumptions at meter scales (1-10 m) using 15 field-collected flow margin intervals from a wide variety of morphologic types in Hawai'i, Iceland, and Idaho. Among the 12 margin intervals that satisfy the current framework's suitability criteria (e.g., geomorphic freshness, shallowly-sloped substrates), we show that 5 exhibit notably scale-dependent fractality and all 5 from lava types other than 'a'ā or pāhoehoe would be classified as one or both of those types at some scales. Additionally, an 'a'ā flow on a 15°slope (Mauna Ulu, Hawai'i) and a spiny pāhoehoe flow confined by a stream bank (Holuhraun, Iceland) exhibit significantly depressed fractalities but lack diagnostic signatures for these modifications. We therefore conclude that all three assumptions of the current framework are invalid at meter scales and propose a new framework to leverage the potential of the underlying fractal technique while acknowledging these complexities.

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Petrological and Mineralogical Variations in 2500-2000 yr B.P. Lava Flows, Craters of the Moon Lava Field, Idaho

Cited by 30 publications

References 0 publications

Contrasting origins of Cenozoic silicic volcanic rocks from the western Cordillera of the United States

Contrasting origins of Cenozoic silicic volcanic rocks from the western Cordillera of the United States

Genesis of post-hotspot, A-type rhyolite of the Eastern Snake River Plain volcanic field by extreme fractional crystallization of olivine tholeiite

Reexamining the potential to classify lava flows from the fractality of their margins

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