The Etendeka Igneous Province: magma types and their stratigraphic distribution with implications for the evolution of the Paraná-Etendeka flood basalt province

Marsh, Julian S; Ewart, A.; Milner, Simon; Duncan, A. R.; Miller, R. McG.

doi:10.1007/s004450000115

Cited by 158 publications

(108 citation statements)

References 25 publications

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“…Most, though not all, examples involve large-volume eruptions of intracontinental, high-temperature and relatively anhydrous, potassic and high-Fe, metaluminous rhyolites and dacites (or latites, e.g. Marsh et al 2001) in a bimodal association with voluminous basaltic magmatism. In many cases, the physical volcanology of the deposits, particularly of the non-welded tephras, is poorly understood.…”

Section: Other Possible Occurrences Of Sr-type Silicic Volcanismmentioning

confidence: 98%

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

et al. 2007

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A new category of large-scale volcanism, here termed Snake River (SR)-type volcanism, is defined with reference to a distinctive volcanic facies association displayed by Miocene rocks in the central Snake River Plain area of southern Idaho and northern Nevada, USA. The facies association contrasts with those typical of silicic volcanism elsewhere and records unusual, voluminous and particularly environmentally devastating styles of eruption that remain poorly understood. It includes: (1) largevolume, lithic-poor rhyolitic ignimbrites with scarce pumice lapilli; (2) extensive, parallel-laminated, medium to coarsegrained ashfall deposits with large cuspate shards, crystals and a paucity of pumice lapilli; many are fused to black vitrophyre; (3) unusually extensive, large-volume rhyolite lavas; (4) unusually intense welding, rheomorphism, and widespread development of lava-like facies in the ignimbrites; (5) extensive, fines-rich ash deposits with abundant ash aggregates (pellets and accretionary lapilli); (6) the ashfall layers and ignimbrites contain abundant clasts of dense obsidian and vitrophyre; (7) a bimodal association between the rhyolitic rocks and numerous, coalescing lowprofile basalt lava shields; and (8) widespread evidence of emplacement in lacustrine-alluvial environments, as revealed by intercalated lake sediments, ignimbrite peperites, rhyolitic and basaltic hyaloclastites, basalt pillow-lava deltas, rhyolitic and basaltic phreatomagmatic tuffs, alluvial sands and palaeosols. Many rhyolitic eruptions were high mass-flux, large volume and explosive (VEI 6-8), and involved H 2 O-poor, low-δ 18 O, metaluminous rhyolite magmas with unusually low viscosities, partly due to high magmatic temperatures (900-1,050°C). SR-type volcanism contrasts with silicic volcanism at many other volcanic fields, where the fall deposits are typically Plinian with pumice lapilli, the ignimbrites are low to medium grade (non-welded to eutaxitic) with abundant pumice lapilli or fiamme, and the rhyolite extrusions are small volume silicic domes and coulées. SR-type volcanism seems to have occurred at numerous times in Earth history, because elements of the facies association occur within some other volcanic fields, including Trans-Pecos Texas, EtendekaParaná, Lebombo, the English Lake District, the Proterozoic Keewanawan volcanics of Minnesota and the Yardea Dacite of Australia.

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Section: Other Possible Occurrences Of Sr-type Silicic Volcanismmentioning

confidence: 98%

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

et al. 2007

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“…The Etendeka Province is exposed onshore as eroded remnants of thick basaltic sequences, intrusive subhorizontal dolerite sills and a number of large subvolcanic ring intrusions, as the Damaraland Complexes (Milner et al, 1995. These ring complexes represent the eroded roots of ancient volcanoes, which were active 6 during flood volcanism (Marsh et al, 2001). South of the Walvis Ridge, offshore Namibia and R.S.A.…”

Section: Subsequent In the Damara Orogeny A Large Network Of Proteromentioning

confidence: 99%

Deep structure of the western South African passive margin — Results of a combined approach of seismic, gravity and isostatic investigations

2009

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The passive margin of the South Atlantic shows typical features of a rifted volcanic continental margin, encompassing seaward dipping reflectors, continental flood basalts and high-velocity/density lower crust at the continentocean transition, probably emplaced during initial seafloor spreading in the Early Cretaceous.The Springbok profile offshore western South Africa is a combined transect of reflection and refraction seismic data. This paper addresses the analysis of the seismic velocity structure in combination with gravity modelling and isostatic modelling to unravel the crustal structure of the passive continental margin from different perspectives.The velocity modelling revealed a segmentation of the margin into three distinct parts of continental, transitional and oceanic crust. As observed at many volcanic margins, the lower crust is characterised by a zone of high velocities with up to 7.4 km/s. The conjunction with gravity modelling affirms the existence of this body and at the same time substantiated its high densities, found to be 3100 kg/m³. Both approaches identified the body to have a thickness of about 10 km. Yet, the gravity modelling predicted the transition between the highdensity body towards less dense material farther west than initially anticipated from velocity modelling and confirmed this density gradient to be a prerequisite to reproduce the observed gravity signal. 2Finally, isostatic modelling was applied to predict average crustal densities if the margin was isostatically balanced. The results imply isostatic equilibrium over large parts of the profile, smaller deviations are supposed to be compensated regionally. The calculated load distribution along the profile implies that all pressures are hydrostatic beneath a depth of 45 km.3

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“…The high-Ti magma-types are represented by Nil Despeandum, Nadas, Sechomib and Hoarusib latites and also by Sarusas, Ventura, Khoraseb, Naudé and Elliott quartz latites (Marsh et al 2001). The geochemical equivalences of major and trace elements between the two counterparts of Paraná-Etendeka CFB were recognized as Santa Maria→Fria, Ourinhos→Khoraseb and Guarapuava→Sarusas (Marsh et al 2001) or Guarapuava→Ventura and Tamarana→Sarusas (Bryan et al 2010).…”

Section: Introductionmentioning

confidence: 99%

The role of viscosity in the emplacement of high-temperature acidic flows of Serra Geral Formation in Torres Syncline (Rio Grande do Sul State, Brazil)

Simões¹,

Rossetti²,

Lima³

et al. 2014

Braz. J. Geol.

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ABSTRACT:The acidic flows from Serra Geral Formation in Torres Syncline, Rio Grande do Sul, Brazil, are on the top of a volcanic sequence composed by a complex facies association of compound, simple and rubbly pahoehoe basic flows, acidic lava domes, and tabular acidic lava flows. The origin and emplacement conditions of the acidic volcanic rocks are discussed in this paper based on petrology, on calculated apatite saturation thermometry temperatures, and on estimated viscosity data. The liquidus temperatures for metaluminous rhyodacite to rhyolite samples are about 1,067.5 ± 25ºC in average. The viscosity (η) values vary from 10 5 to 10 6 Pas for anhydrous conditions, suggesting the emplacement of high-temperaturelow-viscosity lava flows and domes. The occurrence of acidic lava domes above simple pahoehoe flows as flow-banded vitrophyres was under low effusion rates, in spite of their high temperature and low viscosities, which are reflected in their small height. The emplacement of lava domes has continued until the eruption of rubbly pahoehoe flows and the geometry of these deposits rugged the relief. Presence of tabular acidic lava flows covering the landscape indicates that it was under high effusion rates conditions and such flows had well-insulated cooled surface crusts. The capacity to attain greater distances and overpass relief obstacles is explained not only by high effusion rates, but also by very low viscosities at the time of emplacement.

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The Etendeka Igneous Province: magma types and their stratigraphic distribution with implications for the evolution of the Paraná-Etendeka flood basalt province

Cited by 158 publications

References 25 publications

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

‘Snake River (SR)-type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual, high-temperature silicic super-eruptions

Deep structure of the western South African passive margin — Results of a combined approach of seismic, gravity and isostatic investigations

The role of viscosity in the emplacement of high-temperature acidic flows of Serra Geral Formation in Torres Syncline (Rio Grande do Sul State, Brazil)

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