Breccia pipes in the Shoshone Range, Nevada

Gates, Olcott

doi:10.2113/gsecongeo.54.5.790

Cited by 16 publications

(11 citation statements)

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“…Fragments of pumice, tuff, and glass occur in the fine breccia of the Pipe Canyon pipe; the matrix is a dense siliceous, isotropic to devitrified glassy mass containing mineral fragments and rock flour. As interpreted by Gates (1959) and Gilluly and Gates (1965), this breccia formed by volatiles rising from a cupola of magma, penetrated the overlying rock and brecciated it, causing turbulence that resulted in abrasion and mixing of the fragments. Steam generated from ground water percolating into the fragmented rock may have aided the process ofbrecciation; the brecciation could have occurred in several pulses followed by periods of rock bursting and collapse stoping.…”

Section: Pipes and Plugsmentioning

confidence: 86%

Cauldron subsidence of Oligocene age at Mount Lewis, northern Shoshone Range, Nevada

Wrucke¹,

Silberman²

1975

Professional Paper

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In the Shoshone Range of north-central Nevada, a ring fault that dips vertically to 65° inward outlines a deeply eroded cauldron 16 km in diameter. Thrust faults of Early Mississippian and early Mesozoic age that cut Paleozoic and Mesozoic strata in the cauldron have been deformed by the subsidence and dip inward, steeply near the ring fault, more gently in the interior, where they form a concentric pattern around a centrally located cluster of plugs and breccia pipes. The plugs and breccia pipes are the largest intrusive bodies in the subsided block. Plugs of quartz monzonite, rhyolite porphyry, and pumiceous vitrophyre occupy central positions in each of three breccia pipes; a dacite plug and two rhyolite plugs occur several kilometers from the pipes. Other intrusive bodies include a subhorizontal mass of quartz latite breccia at the summit of Mount Lewis, many dikes in the western part of the cauldron, and an intrusive breccia in the ring fault. The intrusive deposits, some of which have been studied in detail by Gilluly and Gates, contribute only a few percent of the exposed rocks in the cauldron. Extrusive rocks in the vicinity of Mount Lewis are preserved mainly within the cauldron. One sequence of extrusive and inter layered volcaniclastic rocks crops out at the summit, on a few spurs that extend out from the summit, and in lowland east of the mountain. This sequence is composed of altered tuffs, dacite lava flows and agglomerate, rhyolite welded tuffs, conglomerate, and sandstone. There is another sequence at the north margin of the cauldron and in an extensive volcano-tectonic depression centered 25 km south of Mount Lewis. It consists of andesite lava flows and rhyolite welded ash-flow tuff of the Caetano Tuff. K-Ar dates and field relations provide a basis for determining only the general chronology of igneous events related to cauldron subsidence at Mount Lewis. Collapse occurred after the ring fault cut a 35.1-m.y.-old granodiorite pluton and before the fault was invaded by 33.2-m.y .-old intrusion breccia. Age determinations of 34.4 m .y. from the dacite plug and 34.7 and 33.2 m .y. from the quartz latite intrusion breccia record volcanism interpreted as occurring before collapse. Subsidence is thought to have resulted from eruption of some of the 33-31-m .y.-old Caetano Tufffrom the Mount Lewis cauldron. Uplift of volcanic and sedimentary rocks in the center of the cauldron 850 m relative to deposits near the ring fault, and the dips away from the summit in patches of these rocks on spurs flanking the mountain may result from mild resurgent doming. Volcanic activity in the northern Shoshone Range during an igneous cycle that existed from 38 to 31 m.y. ago began with intrusions of small granodiorite and quartz monzonite plutons, continued with emplacement of plugs and presubsidence tuffs at Mount Lewis, and ended with eruption of the Caetano Tuff from the volcano-tectonic depression and the Mount Lewis cauldron. The cauldron thus formed differs from many cauldrons in the western United States and fr...

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Section: Pipes and Plugsmentioning

confidence: 86%

Cauldron subsidence of Oligocene age at Mount Lewis, northern Shoshone Range, Nevada

Wrucke¹,

Silberman²

1975

Professional Paper

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“…A) "lasqueamento" ("spalling"), gerado pela diferença entre a pressão litostática na rocha encaixante, e a pressao menor que atua no conduto (em parte, exagerada pelo "efeito Venturi", que re~uz ainda mais a pressão no conduto, por efeito dos gases que escapam para a superficie); Gates (1959) discute os fenôme nos de lasqueamento descritos em túneis e minas profundas.…”

Section: Brechas De Colapsounclassified

“…B) explosões controladas pela expansão de gases magmaticos (Rust, 1937; cf. discussão em Gates, 1959). C) explosões de gases (e água!)…”

Section: Brechas De Colapsounclassified

As brechas de origem ígnea: revisão e proposta para uma classificação geológica

Ulbrich¹

1986

Bol. IG-USP, Publ. espec.

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“…The formation of these rocks was explained as due to gas activity in the vents which have mixed the rock fragments and the matrix by one or several of the following mechanisms : gas streaming, fluidization, or some form of explosion (Gates, 1959 ;Reynolds, 1954).…”

Section: Equivalent Normmentioning

confidence: 99%

New Magmatic Features in Makhtesh Ramon, Southern Israel

Garfunkel

Katz

1967

Geol. Mag.

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Six volcanic vents, trachybasaltic bosses, and new dykes replaced by kaolinite were discovered. The vents are built of trachybasaltictrachytic and basaltic plugs and of tuffisites and tuffs. In the trachybasalts, plagioclase and anorthoclase display complicated reaction phenomena, reflecting changes in crystallization conditions. The trachybasaltic and trachytic bodies were emplaced first and subsequently were altered to kaolinite (Upper Jurassic). Magmatic activity was resumed after an intense erosion period leading to the formation of the vents and of the Lower Cretaceous basaltic volcanic complex which was in part extruded through these vents.

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Breccia pipes in the Shoshone Range, Nevada

Cited by 16 publications

References 0 publications

Cauldron subsidence of Oligocene age at Mount Lewis, northern Shoshone Range, Nevada

Cauldron subsidence of Oligocene age at Mount Lewis, northern Shoshone Range, Nevada

As brechas de origem ígnea: revisão e proposta para uma classificação geológica

New Magmatic Features in Makhtesh Ramon, Southern Israel

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