Millennial timescale resolution of rhyolite magma recharge at Tarawera volcano: insights from quartz chemistry and melt inclusions |
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| Authors: | Phil Shane Victoria C Smith Ian Nairn |
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| Institution: | (1) School of Geography, Geology and Environmental Science, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand;(2) Department of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK;(3) 45 Summit Rd, RD 5, Rotorua, New Zealand;(4) GNS Science, Wairakei Research Centre, Taupo, New Zealand |
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| Abstract: | Most rhyolite eruption episodes of Tarawera volcano have emitted several physiochemically distinct magma batches (∼1–10 km3). These episodes were separated on a millennial timescale. The magma batches were relatively homogeneous in temperature and
composition at pumice scale (>4 cm), but experienced isolated crystallisation histories. At the sub-cm scale, matrix glasses
have trace element compositions (Sr, Ba, Rb) that vary by factors up to 2.5, indicating incomplete mixing of separate melts.
Some quartz-hosted melt inclusions are depleted in compatible trace elements (Sr, Ti, Ba) compared to enclosing matrix glasses.
This could reflect re-melting of felsic crystals deeper in the crystal pile. Individual quartz crystals display a variety
of cathodoluminescence brightness and Ti zoning patterns including rapid changes in melt chemistry and/or temperature (∼50–100°C),
and point to multi-cycle crystallisation histories. The Tarawera magma system consisted of a crystal-rich mass containing
waxing and waning melt pockets that were periodically recharged by silicic melts driven by basaltic intrusion.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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| Keywords: | Rhyolite Okataina Recharge Quartz Melt inclusions Magma |
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