Origin of a rhyolite that intruded a geothermal well while drilling at the Krafla volcano, Iceland

W.A. Elders; G.O. Fridleifsson; R.A. Zierenberg; E.C. Pope; A.K. Mortensen; A. Gudmundsson; Jacob B. Lowenstern; N.E. Marks; L. Owens; D.K. Bird; M. Reed; N.J. Olsen; Peter Schiffmant

doi:10.1130/g31393.1

USGS · 70035895

Origin of a rhyolite that intruded a geothermal well while drilling at the Krafla volcano, Iceland

W.A. Elders·G.O. Fridleifsson·R.A. Zierenberg·E.C. Pope·A.K. Mortensen·A. Gudmundsson·Jacob B. Lowenstern·N.E. Marks·L. Owens·D.K. Bird·M. Reed·N.J. Olsen·Peter Schiffmant

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Abstract

Magma flowed into an exploratory geothermal well at 2.1 km depth being drilled in the Krafla central volcano in Iceland, creating a unique opportunity to study rhyolite magma in situ in a basaltic environment. The quenched magma is a partly vesicular, sparsely phyric, glass containing ∼1.8% of dissolved volatiles. Based on calculated H 2 O-CO 2 saturation pressures, it degassed at a pressure intermediate between hydrostatic and lithostatic, and geothermometry indicates that the crystals in the melt formed at ∼900 °C. The glass shows no signs of hydrothermal alteration, but its hydrogen and oxygen isotopic ratios are much lower than those of typical mantle-derived magmas, indicating that this rhyolite originated by anhydrous mantle-derived magma assimilating partially melted hydrothermally altered basalts.

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Source-reported bounding extent: 65.47650756256367° to 66.06263291952231° latitude; -17.05078125° to -15.831298828124998° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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W.A. Elders, G.O. Fridleifsson, R.A. Zierenberg, E.C. Pope, A.K. Mortensen, A. Gudmundsson, Jacob B. Lowenstern, N.E. Marks, L. Owens, D.K. Bird, M. Reed, N.J. Olsen, Peter Schiffmant. 2011. Origin of a rhyolite that intruded a geothermal well while drilling at the Krafla volcano, Iceland. https://doi.org/10.1130/g31393.1

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