1 / 21

Pavel Izbekov Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks

2006-2007 eruptions of Bezymianny volcano, Kamchatka: Petrological snapshots of the compositionally changing magma system. Pavel Izbekov Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks and PIRE team (http://www.gps.alaska.edu/PIRE). December 11, 2007.

berne
Download Presentation

Pavel Izbekov Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 2006-2007 eruptions of Bezymianny volcano, Kamchatka: Petrological snapshots of the compositionally changing magma system Pavel Izbekov Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks and PIRE team (http://www.gps.alaska.edu/PIRE) December 11, 2007

  2. Introduction • Volcanoes, which erupt frequently / continuously, are perfect targets to study processes in active magma systems. • Each individual eruption is a snapshot of magma system at a particular time. • The sequence of such snapshots show compositional changes in magma system as a function of time throughout the entire period of eruptive activity. • By looking at changes of magma composition we might be able to answer • What processes are behind compositional variations? • How composition of magma affects eruptive behavior? • How fast minerals crystallize in a particular magma system?

  3. Geological background and eruptive history RUSSIA ALASKA Bezymianny

  4. Bezymianny volcano is part of the Kluchevskoy group of volcanoes, located in the Northern part of the Central Kamchatkan Depression Geological background and eruptive history Shiveluch Kluchevskoy Ushkovsky Kamen Bezymianny Tolbachik View to the North from the Int. Space Station, NASA

  5. The oldest part of the stratovolcano was built by lavas, pyroclastic flows, and ash-fall deposits from 10,000-11,000 yr. BP to ca. 6,900 yr. BP. • The activity resumed at the same location in 4,700 yr. BP. Since then, the stratocone of the modern Bezymianny was built by intermittent eruptive activity, separated by long periods of dormancy (Braitseva et. al., 1991). • The most recent eruptive cycle of Bezymianny started in October 1955 after ca. 1000 years of quiescence. Years AD Years BC Geological background and eruptive history

  6. 2006 2006 1957 1957 1946 1946 1957 photo by Gorshkov 1946 photo by Piip Post-1956 trend in eruptive style

  7. Bezymianny dome in August 2007

  8. Trend in whole rock composition

  9. Trend in whole rock composition

  10. Trend in whole rock composition

  11. Trend in whole rock composition

  12. Trend in whole rock composition

  13. Trend in whole rock composition

  14. Trend in whole rock composition 1956 2007

  15. Hb Hb 0.4 mm 0.4 mm Hornblende core in a OPx-CPx-Mt Juvenile clast from the pyroclastic flow of the aggregate of the May 9, 2006 andesite 5/9/06 . Hornblende is exceptionally rare, however it’s remnants abaund. 0.4 mm Changes in mineral assemblage

  16. 1956 magma Plagioclase texture and composition B B E E A A A A C C F F D D 90

  17. 90 80 70 % . A l o B m 60 A , A n A 50 40 30 B B 0 100 200 300 400 500 600 700 Relative distance, core to rim, microns 90 A 80 70 % B . l o 60 m , n A A A 50 40 B B 30 0 100 200 300 400 500 Relative distance, core to rim, microns Plagioclase texture and composition December 24, 2006 May 12, 2007

  18. 6 5 4 CaO, wt.% 3 2 1 0 64 66 68 70 72 74 76 78 SiO , wt.% 2 Glass composition May 9, 2006 Dec. 24, 2006 May 12, 2007 Open symbols – inclusions Filled symbols – matrix glass

  19. Glass composition May 9, 2006 Dec. 24, 2006 May 12, 2007 Open symbols – inclusions Filled symbols – matrix glass

  20. Trend in whole rock composition 62 61 60 59 , wt. % 58 2 SiO 57 56 55 54 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Time of eruption, calendar years

  21. Summary of observations and conclusion Since 1956 Bezymianny erupts magma, which becomes progressively more mafic with time. On a smaller scale, there are periods, during which the erupted products become more silicic. These short-term variations are superimposed on the general trend. The sequence of 2006-2007 products may represent one of such examples, which is corroborated by our glass data. The composition of melt inclusions in the outermost “dusty” zones of plagioclase phenocrysts and the composition of matrix glass form a linear trend with time becoming more silicic. This suggests that the outermost “dusty” zones of plagioclase phenocrysts form immediately prior to each individual eruption. These observations are consistent with a view that Bezymianny magma system is frequently replenished by mafic inputs, which change overall composition of the magma system and may serve as eruption triggers.

More Related