Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions |
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Authors: | B?rje Dahren Valentin R Troll Ulf B Andersson Jane P Chadwick Màiri F Gardner Kairly Jaxybulatov and Ivan Koulakov |
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Institution: | (1) Department of Earth Sciences, CEMPEG, Uppsala University, Uppsala, Sweden;(2) Department of Petrology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands;(3) Department of Geology, University College Cork, Cork, Ireland;(4) Institute for Petroleum Geology and Geophysics, SB RAS, Novosibirsk, Russia;(5) Research Department, Swedish Museum of Natural History, Stockholm, Sweden |
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Abstract: | Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing
at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite
of thermobarometric models. These include clinopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, clinopyroxene
composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage
in the region of 2–8 km beneath Krakatau, while existing seismic evidence points towards mid- to deep-crustal storage zone(s),
at 9 and 22 km, respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7–12 km,
while plagioclase records both shallow crustal (3–7 km) and sub-Moho (23–28 km) levels of crystallization. These magma storage
regions coincide with well-constrained major lithological boundaries in the crust, implying that magma ascent and storage
at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified
a separate upper crustal (<7 km) and a lower to mid-crustal magma storage region (>7 km). Both petrological and seismic methods
are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological
surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes. |
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