The magma plumbing system of Bezymianny Volcano: Insights from a 54 year time series of trace element whole-rock geochemistry and amphibole compositions

• Published in: Journal of volcanology and geothermal research Vol. 263; pp. 108 - 121
• Main Authors: Turner, Stephen, Izbekov, Pavel, Langmuir, Charles
• Format: Journal Article
• Language: English
• Published: 01.08.2013
• Subjects: Amphiboles; Arrays; Liquids; Magma; Reservoirs; Silicon dioxide; Trace elements; Volcanoes
• ISSN: 0377-0273
• DOI: 10.1016/j.jvolgeores.2012.12.014

Samples from 33 individual eruptions of Bezymianny volcano between 1956 and 2010 provide an opportunity to study in detail the temporal evolution of an arc volcano. Major element and ICP-MS trace element analyses show that the eruptive products shifted progressively from relatively silicic magma in 1956 (~ 60.4% SiO2) to more mafic compositions (e.g. 56.8% SiO2 in 2010). Amphibole compositions changed concurrently from low-Al2O3 to high-Al2O3. Whole rock element-element variation diagrams show tight compositional arrays, some with a distinct kink in the late 1970s, which cannot be reproduced by fractionation of a single magma along a liquid line of descent. Amphibole thermobarometry indicates amphibole crystallization in two separate reservoirs, one between 200 and 300 MPa, and another between 500 and 750 MPa. Liquid compositions calculated from the amphibole analyses show that liquids stored in each reservoir become increasingly mafic from 1956 to 2010, suggesting that each reservoir received magma inputs from more mafic sources throughout the eruptive cycle.