[S-VC11] Volatiles and volcanoes: the role of volatiles in determining how and when volcanoes erupt

★ [SVC11-08] Chronology of degassing and magma mixing at Surtsey (Iceland, 1963-67)

*C ian SCHIPPER¹, VOYER, Marion LE², Yves MOUSSALLAM³, James d.l. WHITE⁴, Sveinn p JAKOBSSON⁵, Jun-ichi KIMURA⁶, Qing CHANG⁶ (1.SGEES, Victoria University of Wellington, New Zealand, 2.Carnegie Institute, USA, 3.ISTO-CNRS l'Universite d'Orleans, France, 4.Geology Department, University of Otago, New Zealand, 5.Icelandic Institute of Natural History, Iceland, 6.IFREE - JAMSTEC, Japan)

Keywords:volatiles, degassing, geochemistry, pyroclastic, subaqueous, Iceland

In 1963-67, Surtsey (Iceland) provided the type example of shallow-emergent explosive volcanism; however, magma ascent and degassing in this benchmark eruption remain unconstrained. We use major/trace elements and volatiles in olivine-hosted melt inclusions and glasses to show that multiple distinct melts were stored at 9.5-12 km and subsequently mixed at 6-8 km below Surtsey. The chronological contribution of each melt body to surface processes can be tracked by correlating volatile (H/C, S/C), trace element (HSFE/LILE), and rare earth element (LREE/HREE) ratios of inclusions to the time series of gas and lava compositions that were measured syn-eruptively. This captures progressive shallowing and mixing of melts through time, and allows time-stamped modeling of degassing and melt+gas redox evolution over a 3-year period. Novel correlation between inclusions from surface tephra and historical measurements permits temporal and spatial controls on activity at Surtsey to be determined >50 years after the eruption.