The Oligocene Lund Tuff, Great Basin, USA: a very large volume monotonous intermediate

Maughan, Larissa L; Christiansen, Eric H.; Best, Myron G.; Grommé, C. Sherman; Deino, Alan L.; Tingey, David G.

doi:10.1016/s0377-0273(01)00256-6

Cited by 78 publications

(62 citation statements)

References 47 publications

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“…The prodigious 'supervolcanic' volume of silicic calc-alkaline magmas erupted during the ignimbrite flareups in the Great Basin area and in the central Andes since the middle Miocene are believed to be a direct consequence of an unusually thick crust (Maughan et al 2002;de Silva et al 2006). Because the lower to middle crust was unusually hot, it was a fertile site for silicic magma generation as vast amounts of mantle-derived magma were intruded into it.…”

Section: Discussionmentioning

confidence: 99%

“…Because the lower to middle crust was unusually hot, it was a fertile site for silicic magma generation as vast amounts of mantle-derived magma were intruded into it. The unique monotonous intermediates, or crystal-rich high-K dacite tuffs, that constitute a significant proportion of the ignimbrites in both locales (Maughan et al 2002) are best explained by evolution in pancake-shaped magma chambers resulting from magma accumulation within a thickened crust, where compressive tectonic and gravitational stresses are more or less balanced.…”

Section: Discussionmentioning

confidence: 99%

“…150 -154, Figure 18a). Especially noteworthy is the occurrence in both of several thousands of cubic kilometres of crystal-rich, calc-alkaline high-K dacite ignimbrite -the monotonous intermediates of Hildreth (1981) and Maughan et al (2002) -together with lesser, but still prodigious, volumes of rhyolite ash-flow tuff. Such large scale, supervolcano melting events require unusually large inputs of mantle-derived magma into the continental crust to power the silicic magma-generating systems.…”

Section: Geology Of the Central Andean Plateau In Briefmentioning

confidence: 99%

“…At least a dozen very large volume (.1000 km 3 ), or 'supervolcanic ' (de Silva 2008;Miller and Wark 2008), eruptions as well as a greater number of large volume (100s of km 3 ) eruptions occurred from the latest Eocene to early Miocene from 36 to 18 Ma (Best et al 1989a(Best et al , 1989b(Best et al , 1995Best and Christiansen 1991;Maughan et al 2002;John et al 2008). This flareup occurred in a remarkably brief period of time relative to the span of some 200 million years through the Mesozoic and into the middle Cenozoic when subduction of oceanic crust beneath the western North American plate resulted in arc magmatism.…”

Section: Introductionmentioning

confidence: 99%

“…This flareup occurred in a remarkably brief period of time relative to the span of some 200 million years through the Mesozoic and into the middle Cenozoic when subduction of oceanic crust beneath the western North American plate resulted in arc magmatism. In addition to the widespread rhyolite, four of these supervolcanic eruptions were of crystal-rich dacite magma, the monotonous intermediates of Hildreth (1981) and Maughan et al (2002). Eruptions of these colossal volumes of rhyolitic and hotter dacitic magma, accompanied by extrusion of only very minor more mafic magma -and no true basalt until the waning stages of the ignimbrite flareup -imply unusual magma generation in the volcanic arc, requiring a prodigious amount of thermal energy.…”

Section: Introductionmentioning

confidence: 99%

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The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

Best

Barr

Christiansen

et al. 2009

International Geology Review

108

125

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Uncertainty surrounds the fate of the orogenic plateau in what is now the Great Basin in western Utah and Nevada, which resulted from the Mesozoic and earliest Cenozoic contractile deformations and crustal thickening. Although there is some consensus regarding the gravitational collapse of the plateau by extensional faulting and consequent crustal thinning, whether or not the plateau existed during the middle Cenozoic Great Basin ignimbrite flareup -one of the grandest expressions of continental volcanism in the geologic record -had remained in doubt. We use compositions of contemporaneous calc-alkaline lava flows as well as configurations of the ignimbrite sheets to show that the Great Basin area during the middle Cenozoic was a relatively smooth plateau underlain by unusually thick crust. We compare analyses of 376 intermediate-composition lava flows in the Great Basin that were extruded at 42 -17 Ma with compositions of .6000 analyses of the late Cenozoic lava flows in continental volcanic arcs that correlate roughly with known crustal thickness. This comparison indicates that the middle Cenozoic Great Basin crust was much thicker than the present ca. 30 km thickness, likely as much as 60 -70 km. If isostatic equilibrium prevailed, this unusually thick continental crust must have supported high topography. This high terrain in SE Nevada and SW Utah was progressively smoothed as successive ignimbrite outflow sheets were emplaced over areas currently as much as tens of thousands of square kilometres to aggregate thicknesses of as much as hundreds of metres. The generally small between-site variations in the palaeomagnetic directions of individual sheets lend further support for a relatively smooth landscape over which the sheets were draped. We conclude that during the middle Cenozoic, especially towards the close of the ignimbrite flareup, this Great Basin area was a relatively flat plateau, and because it was also high in elevation, we refer to it as an Altiplano. It was not unlike the present-day Altiplano-Puna in the tectonically similar central Andes, where an ignimbrite flareup comparable to that in the Great Basin occurred at ca. 9-3 Ma. Outflow ignimbrite sheets that were deposited from 35 to 23 Ma on the progressively smoothed Altiplano in south-eastern Nevada were derived from source calderas to the west. Of the 12 major sheets from seven sources, nine are distributed unevenly east of their sources while the remaining three sheets are spread about as far east as west of their sources. This eccentricity of sources near the western margin of 75% of the sheets indicates the existence of a NS-trending topographic barrier in central Nevada that restricted westward dispersal of ash flows. In a symmetric manner, eastward dispersal of ash flows from sources farther west seemed to have been impeded by this same topographic barrier. The westward dispersal was controlled in part by westward-draining stream valleys incised in the sloping flank of the Great Basin Vol. 51, Nos. 7 -8, July-August 2009, 589-633 A...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Geology Of the Central Andean Plateau In Briefmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

Best

Barr

Christiansen

et al. 2009

International Geology Review

108

125

View full text Add to dashboard Cite

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Zircon U‐Pb geochronology of the Mount Givens Granodiorite: Implications for the genesis of large volumes of eruptible magma

Frazer

Coleman

Mills³

2014

JGR Solid Earth

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The Mount Givens Granodiorite, a large pluton in the central Sierra Nevada batholith, California, is similar in area to zoned intrusive suites yet is comparatively chemically and texturally homogenous. New zircon U-Pb geochronology indicates that the pluton was constructed over at least 7 Ma from 97.92 ± 0.06 Ma to 90.87 ± 0.05 Ma. Combining the new geochronology with the exposed volume of the pluton yields an estimated magma flux of <0.001 km 3 /a. The geochronologic data are at odds with the previously speculated links between plutons such as the Mount Givens Granodiorite and large-volume homogeneous ignimbrites (often termed monotonous intermediates). Existing data indicate that large plutons accumulate at rates of ≤0.001 km 3 /a, 1-2 orders of magnitude less than fluxes calculated for dated monotonous intermediates. If monotonous intermediates are remobilized, erupted plutons accumulated at rates comparable to dated examples, they should preserve a record of zircon growth of up to 10 Ma. Alternatively, the long history of zircon growth recorded in plutons may be erased during the processes of reheating and remobilization that precede supervolcano eruption. However, zircon dissolution modeling, based on hypothetical temperature-time histories for preeruptive monotonous intermediates, indicates that rejuvenation events would not sufficiently dissolve zircon. We suggest that eruptions of monotonous intermediates occur during high magmatic flux events, leaving little behind in the intrusive rock record, whereas low fluxes favor pluton accumulation.

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Seismic Detection and Characterization of the Altiplano-Puna Magma Body, Central Andes

Zandt¹,

Leidig²,

Chmielowski³

et al. 2003

Seismic Motion, Lithospheric Structures, Earthquake and Volcanic Sources: The Keiiti Aki Volume

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The Oligocene Lund Tuff, Great Basin, USA: a very large volume monotonous intermediate

Cited by 78 publications

References 47 publications

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

Zircon U‐Pb geochronology of the Mount Givens Granodiorite: Implications for the genesis of large volumes of eruptible magma

Seismic Detection and Characterization of the Altiplano-Puna Magma Body, Central Andes

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