Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc
Geologic, chronologic, and U–Th isotope data from Pleistocene–Recent basaltic to rhyolitic lavas and their phenocrysts constrain the long-term evolution of magmatic processes at Seguam Island, Aleutian Island arc, and suggest a model in which erupted magmas were derived from a single, deep seated re...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.552.2965 2023-05-15T13:14:41+02:00 Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc Brian R. Jicha Brad S. Singer Brian L. Beard Clark M. Johnson The Pennsylvania State University CiteSeerX Archives 2005 application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.552.2965 http://www.geo.mtu.edu/~raman/papers2/JichaetalEPSL05.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.552.2965 http://www.geo.mtu.edu/~raman/papers2/JichaetalEPSL05.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://www.geo.mtu.edu/~raman/papers2/JichaetalEPSL05.pdf text 2005 ftciteseerx 2016-01-08T11:36:54Z Geologic, chronologic, and U–Th isotope data from Pleistocene–Recent basaltic to rhyolitic lavas and their phenocrysts constrain the long-term evolution of magmatic processes at Seguam Island, Aleutian Island arc, and suggest a model in which erupted magmas were derived from a single, deep seated reservoir for ~130 kyrs of its eruptive history. The monotonic evolution in (230Th / 232Th)0 ratios is consistent with radiogenic ingrowth of 230Th in a long-lived magma reservoir between 142 and 9 ka. Internal U–Th mineral isochrons from seven lavas and one ignimbrite are indistinguishable from their eruption ages as constrained by 40Ar / 39Ar dating, which implies a short period (i.e., 103 yrs or less) of crystal residence in the magma prior to eruption. These results can be reconciled if small batches of magma are repeatedly extracted from a deep, thermally buffered, basaltic reservoir, followed by decompression-driven crystallization and differentiation in small chambers or conduits in the upper crust immediately prior to eruption. Stratovolcano collapse at 9 ka produced a 4 km diameter caldera and a 70 m thick dacitic ignimbrite covering ~12 km2. The ignimbrite, as well as subsequent rhyolitic and basaltic lava flows, signal a decrease in (230Th / 232Th)0 and 87Sr / 86Sr ratios. The abrupt change in magma composition at 9 ka most likely reflects disruption of the long-lived reservoir by rapid ascent of basaltic magma with low (230Th / 232Th) and 87Sr / 86Sr ratios and excess 226Ra. While the Text Aleutian Island Unknown |
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Geologic, chronologic, and U–Th isotope data from Pleistocene–Recent basaltic to rhyolitic lavas and their phenocrysts constrain the long-term evolution of magmatic processes at Seguam Island, Aleutian Island arc, and suggest a model in which erupted magmas were derived from a single, deep seated reservoir for ~130 kyrs of its eruptive history. The monotonic evolution in (230Th / 232Th)0 ratios is consistent with radiogenic ingrowth of 230Th in a long-lived magma reservoir between 142 and 9 ka. Internal U–Th mineral isochrons from seven lavas and one ignimbrite are indistinguishable from their eruption ages as constrained by 40Ar / 39Ar dating, which implies a short period (i.e., 103 yrs or less) of crystal residence in the magma prior to eruption. These results can be reconciled if small batches of magma are repeatedly extracted from a deep, thermally buffered, basaltic reservoir, followed by decompression-driven crystallization and differentiation in small chambers or conduits in the upper crust immediately prior to eruption. Stratovolcano collapse at 9 ka produced a 4 km diameter caldera and a 70 m thick dacitic ignimbrite covering ~12 km2. The ignimbrite, as well as subsequent rhyolitic and basaltic lava flows, signal a decrease in (230Th / 232Th)0 and 87Sr / 86Sr ratios. The abrupt change in magma composition at 9 ka most likely reflects disruption of the long-lived reservoir by rapid ascent of basaltic magma with low (230Th / 232Th) and 87Sr / 86Sr ratios and excess 226Ra. While the |
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The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
Brian R. Jicha Brad S. Singer Brian L. Beard Clark M. Johnson |
spellingShingle |
Brian R. Jicha Brad S. Singer Brian L. Beard Clark M. Johnson Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc |
author_facet |
Brian R. Jicha Brad S. Singer Brian L. Beard Clark M. Johnson |
author_sort |
Brian R. Jicha |
title |
Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc |
title_short |
Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc |
title_full |
Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc |
title_fullStr |
Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc |
title_full_unstemmed |
Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc |
title_sort |
contrasting timescales of crystallization and magma storage beneath the aleutian island arc |
publishDate |
2005 |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.552.2965 http://www.geo.mtu.edu/~raman/papers2/JichaetalEPSL05.pdf |
genre |
Aleutian Island |
genre_facet |
Aleutian Island |
op_source |
http://www.geo.mtu.edu/~raman/papers2/JichaetalEPSL05.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.552.2965 http://www.geo.mtu.edu/~raman/papers2/JichaetalEPSL05.pdf |
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Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
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1766264920215650304 |