Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling
The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this stud...
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ftcdlib:oai:escholarship.org/ark:/13030/qt68g949q7 2023-05-15T16:48:18+02:00 Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling Saubin, E Kennedy, B Tuffen, H Nichols, ARL Villeneuve, M Bindeman, I Mortensen, A Schipper, CI Wadsworth, FB Watson, T Zierenberg, R 1815 - 1830 2021-01-01 application/pdf https://escholarship.org/uc/item/68g949q7 unknown eScholarship, University of California qt68g949q7 https://escholarship.org/uc/item/68g949q7 public Bulletin of the Geological Society of America, vol 133, iss 9-10 Geology Geochemistry Geophysics article 2021 ftcdlib 2021-10-18T17:16:15Z The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this study, we analyzed the complete time series of glass particles retrieved after magma was intersected, in terms of distribution, chemistry, and vesicle textures. Detailed analysis of the particles revealed them to represent bimodal rhyolitic magma compositions and textures. Early-retrieved clear vesicular glass has higher SiO2, crystal, and vesicle contents than later-retrieved dense brown glass. The vesicle size and distribution of the brown glass also reveal several vesicle populations. The glass particles vary in δD from −120‰ to −80‰ and have dissolved water contents spanning 1.3−2 wt%, although the majority of glass particles exhibit a narrower range. Vesicular textures indicate that volatile overpressure release predominantly occurred prior to late-stage magma ascent, and we infer that vesiculation occurred in response to drilling-induced decompression. The textures and chemistry of the rhyolitic glasses are consistent with variable partial melting of host felsite. The drilling recovery sequence indicates that the clear magma (lower degree partial melt) overlays the brown magma (higher degree partial melt). The isotopes and water species support high temperature hydration of these partial melts by a mixed meteoric and magmatic composition fluid. The textural evidence for partial melting and lack of crystallization imply that magma production is ongoing, and the growing magma body thus has a high potential for geothermal energy extraction. In summary, transfer of heat and fluids into felsite triggered variable degrees of felsite partial melting and produced a hydrated rhyolite magma with chemical and textural heterogeneities that were then enhanced by drilling perturbations. Such partial melting could occur extensively in the crust above magma chambers, where complex intrusive systems can form and supply the heat and fluids required to re-melt the host rock. Our findings emphasize the need for higher resolution geophysical monitoring of restless calderas both for hazard assessment and geothermal prospecting. We also provide insight into how shallow silicic magma reacts to drilling, which could be key to future exploration of the use of magma bodies in geothermal energy. Article in Journal/Newspaper Iceland University of California: eScholarship Krafla ENVELOPE(-16.747,-16.747,65.713,65.713) |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Geology Geochemistry Geophysics |
spellingShingle |
Geology Geochemistry Geophysics Saubin, E Kennedy, B Tuffen, H Nichols, ARL Villeneuve, M Bindeman, I Mortensen, A Schipper, CI Wadsworth, FB Watson, T Zierenberg, R Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling |
topic_facet |
Geology Geochemistry Geophysics |
description |
The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this study, we analyzed the complete time series of glass particles retrieved after magma was intersected, in terms of distribution, chemistry, and vesicle textures. Detailed analysis of the particles revealed them to represent bimodal rhyolitic magma compositions and textures. Early-retrieved clear vesicular glass has higher SiO2, crystal, and vesicle contents than later-retrieved dense brown glass. The vesicle size and distribution of the brown glass also reveal several vesicle populations. The glass particles vary in δD from −120‰ to −80‰ and have dissolved water contents spanning 1.3−2 wt%, although the majority of glass particles exhibit a narrower range. Vesicular textures indicate that volatile overpressure release predominantly occurred prior to late-stage magma ascent, and we infer that vesiculation occurred in response to drilling-induced decompression. The textures and chemistry of the rhyolitic glasses are consistent with variable partial melting of host felsite. The drilling recovery sequence indicates that the clear magma (lower degree partial melt) overlays the brown magma (higher degree partial melt). The isotopes and water species support high temperature hydration of these partial melts by a mixed meteoric and magmatic composition fluid. The textural evidence for partial melting and lack of crystallization imply that magma production is ongoing, and the growing magma body thus has a high potential for geothermal energy extraction. In summary, transfer of heat and fluids into felsite triggered variable degrees of felsite partial melting and produced a hydrated rhyolite magma with chemical and textural heterogeneities that were then enhanced by drilling perturbations. Such partial melting could occur extensively in the crust above magma chambers, where complex intrusive systems can form and supply the heat and fluids required to re-melt the host rock. Our findings emphasize the need for higher resolution geophysical monitoring of restless calderas both for hazard assessment and geothermal prospecting. We also provide insight into how shallow silicic magma reacts to drilling, which could be key to future exploration of the use of magma bodies in geothermal energy. |
format |
Article in Journal/Newspaper |
author |
Saubin, E Kennedy, B Tuffen, H Nichols, ARL Villeneuve, M Bindeman, I Mortensen, A Schipper, CI Wadsworth, FB Watson, T Zierenberg, R |
author_facet |
Saubin, E Kennedy, B Tuffen, H Nichols, ARL Villeneuve, M Bindeman, I Mortensen, A Schipper, CI Wadsworth, FB Watson, T Zierenberg, R |
author_sort |
Saubin, E |
title |
Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling |
title_short |
Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling |
title_full |
Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling |
title_fullStr |
Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling |
title_full_unstemmed |
Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling |
title_sort |
textural and geochemical window into the iddp-1 rhyolitic melt, krafla, iceland, and its reaction to drilling |
publisher |
eScholarship, University of California |
publishDate |
2021 |
url |
https://escholarship.org/uc/item/68g949q7 |
op_coverage |
1815 - 1830 |
long_lat |
ENVELOPE(-16.747,-16.747,65.713,65.713) |
geographic |
Krafla |
geographic_facet |
Krafla |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
Bulletin of the Geological Society of America, vol 133, iss 9-10 |
op_relation |
qt68g949q7 https://escholarship.org/uc/item/68g949q7 |
op_rights |
public |
_version_ |
1766038412115050496 |