Case study of an extensive silicic lava: the Bracks Rhyolite, Trans-Pecos Texas

Mecanismos eruptivos y procesos depositacionales del Grupo Choiyoi en el área de Las Caletas, Cordillera Frontal de San Juan, Argentina

“…El análisis preliminar de datos geoquímicos indica valores comprendidos entre 771 y 818°C (Tabla 2), los que pueden ser considerados bajos en comparación con las temperaturas de otras lavas silícicas voluminosas (Henry et al, 1990;Vervoort y Green, 1997;Creaser y White, 1991). Como referencia, los valores de viscosidad para el rango de temperaturas considerado y para contenidos arbitrarios del 2% (porcentaje en peso) de H 2 O (este podría ser un valor máximo razonable, considerando también los valores de LOI<1,51, el que evitaría grandes erupciones explosivas y favorecería mecanismos efusivos; Manley, 1996b) arrojados por el modelo de Giordano et al (2008), oscilan entre 3,52x10 7 y 8,09x10 6 Pa s (Tabla 2), tres a cuatro órdenes de magnitud más bajos que en condiciones anhidras.…”

Extensive soft-sediment deformation and peperite formation at the base of a rhyolite lava: Owyhee Mountains, SW Idaho, USA

“…Rhyolite magmas typically extrude comparatively smallvolume lava domes of high viscosity, yet some rhyolitic volcanic fields produce voluminous lava flows, often hundreds of metres thick (Bonnichsen 1982;Henry et al 1990;Bonnichsen and Kauffman 1987;Branney et al 2008). Large volume silicic volcanism producing extensive, high temperature silicic lava flows and lava-like ignimbrites is characterised as BSR-type^, or BSnake River-type^volcanism by Branney et al (2008) and is typical of the bimodal Columbia River-Yellowstone Volcanic Province in the NW of the USA.…”

“…Thick rhyolite lava flows (>50 m) can impose huge amounts of downward force and heat on to the underlying substrate. When this substrate is soft, unconsolidated sediment, the effects of loading and heat can significantly modify the local stratigraphic architecture, either by local compaction and induration (Christiansen and Lipman 1966;Henry et al 1990) or sediment fluidisation and peperite formation (Kokelaar 1982). Exposure of the contact between rhyolite lava flows and underlying sediment is rare, notably because rhyolite lava domes tend to form as opposed to lava flows (Branney et al 2008) and can be poorly exposed either due to insufficient erosion or talus cover (Dadd 1992;Manley 1996).…”

“…Hanson and Schweickert 1982;Kokelaar 1982;Hanson and Wilson 1993;Hanson and Hargrove 1999;Dadd and Van Wagoner 2002;Donaire et al 2002;Skilling et al 2002;Németh et al 2008). In contrast, there have been very few studies on peperite formation and sediment fluidisation at the base of a rhyolite lava flow (Henry et al 1990;Tuffen et al 2001;Branney et al 2008), where the sediment substrate is often less confined and where surface topography and environmental setting (e.g. water-logged sediments) are important factors (Skilling et al 2002).…”

Volcanism of the Palaeoproterozoic Bushveld Large Igneous Province: The Rooiberg Group, Kaapvaal Craton, South Africa

“…Younger examples include the Snake River Plain (Bonnichsen and Kauffman, 1987;Manley, 1996;Branney et al, 2008), Trans-Pecos Texas (Henry et al, 1989(Henry et al, , 1990, Yellowstone National Park (Christiansen and Hildreth, 1989), and the Etendeka Igneous Province in Namibia (Milner, 1986;Milner et al, 1992).…”