Karymshina, a giant supervolcano caldera in Kamchatka: Boundaries, structure, volume of pyroclastics

Isotopic and Petrologic Investigation, and a Thermomechanical Model of Genesis of Large-Volume Rhyolites in Arc Environments: Karymshina Volcanic Complex, Kamchatka, Russia

“…Bindeman et al (2010) performed Ar-Ar and U-Pb zircon dating and demonstrated that the top and the bottom of the 1,000 m ignimbrite sheet (their Figure 4), have identical ages of 1.78 ± 0.02 Ma. Due to the great thickness and lateral extent of this deposit (Figure 2), these authors agreed with interpretation of Leonov and Rogozin (2007) that it represents a remnant of densely welded and relatively compositionally unzoned 1.78 Ma intracaldera ignimbrite, brought up by post 1.78 Ma uplift and erosion. The situation is analogous to the 2.8 Ma, two-km thick uplifted and dissected, intracaldera Chegem ignimbrite in the Caucasus and we take instruction from the study of that center by Lipman et al (1993) in describing and discerning field relations for Karymshina ignimbrite.…”

“…Using the dimensions of the caldera and the volume of intracaldera ignimbrites (275 km 3 ) given in Leonov and Rogozin (2007) it can be estimated that the total eruptive volume was about three times this number or close to 800 km 3 if ash and eroded extracaldera deposits are each 275 km 3 based on similar relationships proposed for the western USA calderas (Bacon, 1983). Lithic fragments in ignimbites and post caldera intrusions are represented by autholithic blobs consisting of elongated plagioclase in glass without quartz ( Figure 4F) and silicified hydrothermally altered materials in quantities not exceeding a few percent.…”

“…Abundant silicic rocks were first discovered in the area in the course of geologic mapping in the 1960s−1980s and were initially considered to represent several eruptive silicic vents collectively forming a volcano-tectonic depression (Sheimovich and Patoka, 1989;Sheimovich and Khatskin, 1996;Geological Map of the Russian Federation, 2000;Sheimovich and Golovin, 2003). A part of this complex around Tolsty Mys Mountain (1343 m), the highest topographic point in the area (Figure 2), was reinterpreted by Leonov and Rogozin (2007) as a resurgent dome inside an uplifted and dissected, hundreds of meters-thick intracaldera tuff, within the large 25 × 15 km Karymshina Caldera. Bindeman et al (2010) performed Ar-Ar and U-Pb zircon dating and demonstrated that the top and the bottom of the 1,000 m ignimbrite sheet (their Figure 4), have identical ages of 1.78 ± 0.02 Ma.…”

The analysis of spatial distributions, origins of caldera-forming eruptions with basaltic-andesitic magma compositions, and genesis of Miocene ignimbrites of the Eastern volcanic belt, Kamchatka

“…Егоров [Egorov, 2009] описывал Авачинско-Ганальский центр эндогенной активности. После появления в последние годы понятия о супервулканах и открытия первого супервулкана на Камчатке [Leonov, Rogozin, 2007] В.Л. Леоновым было сделано предположение, что в районе верховьев рек Авача и Кавыча на ВВП может быть выявлен еще один супервулкан, получивший в дальнейшем название «Верхнеавачинская кальдера» [Leonov et al, 2011].…”

“…Леонова велись работы по обнаружению древних кальдерных комплексов Камчатки, источников мощных игнимбритовых покровов [Melekestsev, 1974;Leonov, Grib, 2004]. Так, благодаря детальному геологическому картированию на Южной Камчатке удалось обнаружить кальдеру супервулкана Карымшина и реконструировать гигантский пирокластический поток, связанный с этой кальдерой [Leonov, Rogozin, 2007]. С 2009 г. ведутся работы по изучению обнаруженной Верхнеавачинской кальдеры, расположенной в верховье рек Левая Авача и Кавыча в Восточном вулканическом поясе (ВВП) Камчатки [Leonov et al, 2011].…”