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Physical volcanology of continental large igneous provinces: update and review

White, James D. L.; Bryan, Scott E.; Ross, Pierre-Simon; Self, Stephen; Thordarson, Thorvaldur (2009). Physical volcanology of continental large igneous provinces: update and review In: Studies in Volcanology : The Legacy of George Walker. Special Publications of IAVCEI (2). Geological Society Of London, United Kingdom, p. 291-321.

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Résumé

Large igneous provinces (LIPs) form in both oceanic and continental settings by the emplacement and eruption of voluminous magmas ranging from basalt to rhyolite in composition. Continental basaltic LIPs are the best studied, and consist of crustal intrusive systems, extensive flood lavas and ignimbrites, and mafic volcaniclastic deposits in varying proportions. Intrusive rocks are inferred to represent the solidified remnants of a plumbing system that fed eruptions at the surface, as well as themselves representing substantial accumulations of magma in the subsurface. The vast majority of intrusive rock within the upper crust is in widespread sills, the emplacement of which may structurally isolate and dismember upper crustal strata from underlying basement, as well as spawning dike assemblages of complex geometry. Interaction of dikes and shoaling sills with near-surface aquifers is implicated in development of mafic volcaniclastic deposits which, in better-studed provinces, comprise large vent complexes and substantial primary volcaniclastic deposits. Flood lavas generally postdate and overlie mafic volcaniclastic deposits, and are emplaced as pahoehoe flows at a grand scale (up to10⁴ km²) from eruptions lasting years to decades. As with modern Hawaiian analogues, pahoehoe flood lavas have erupted from fissure vents that sometimes show evidence for high lava fountains at times during eruption. In contrast to basaltic provinces, in which volcaniclastic deposits are significant but not dominant, silicic LIPs are dominated by deposits of explosive volcanism, although they also contain variably significant contributions from widespread lavas. Few vent sites have been identified for silicic eruptive units in LIPs, but it has been recognised that some ignimbrites have also been erupted from fissure-like vents. Although silicic LIPs are an important, albeit less common, expression of LIP events along continental margins, the large volumes of easily erodible primary volcaniclastic deposits result in these provinces also having a significant sedimentary signature in the geologic record. The inter-relationships between between flood basalt lavas and volcaniclastic deposits during LIP formation can provide important constraints on the relative timings between LIP magmatism, extension, kilometre-scale uplift, and palaeoenvironmental changes.

Type de document:
Mots-clés libres: volcanologie; provinces ignées continentales
Centre: Centre Eau Terre Environnement
Date de dépôt: 08 août 2014 12:07
Dernière modification: 11 janv. 2017 20:52
URI: http://espace.inrs.ca/id/eprint/1912

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