To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths
We have studied glass-bearing leucocratic (granitic to Qz-monzonitic) crustal xenoliths from the Tindfjoll Pleistocene volcanic complex, SW Iceland. The xenoliths consist of strongly resorbed relicts of anorthitic plagioclase, K-rich feldspar and rounded quartz in color-less through pale to dark-bro...
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ftpubman:oai:pure.mpg.de:item_2231283 2023-08-20T04:07:33+02:00 To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths Gurenko, A. Bindeman, I. Sigurdsson, I. 2015 http://hdl.handle.net/11858/00-001M-0000-0029-28D0-B unknown info:eu-repo/semantics/altIdentifier/doi/10.1007/s00410-015-1145-4 http://hdl.handle.net/11858/00-001M-0000-0029-28D0-B Contributions to Mineralogy and Petrology info:eu-repo/semantics/article 2015 ftpubman https://doi.org/10.1007/s00410-015-1145-4 2023-08-01T22:14:29Z We have studied glass-bearing leucocratic (granitic to Qz-monzonitic) crustal xenoliths from the Tindfjoll Pleistocene volcanic complex, SW Iceland. The xenoliths consist of strongly resorbed relicts of anorthitic plagioclase, K-rich feldspar and rounded quartz in color-less through pale to dark-brown interstitial glass. Spongy clinopyroxene and/or rounded or elongated crystals of orthopyroxene are in subordinate amount. Magnetite, ilmenite, zircon, apatite, allanite and/or chevkinite are accessory minerals. The xenoliths more likely are relicts of earlier-formed, partially melted Si-rich rocks or quartz-feldspar-rich crystal segregations, which suffered latter interaction with hotter and more primitive magma(s). Icelandic lavas are typically low in delta O-18 compared to mantle-derived, "MORB"-like rocks (similar to 5.6 +/- 0.2 %), likely due to their interaction with, or contamination by, the upper-crustal rocks affected by rain and glacial melt waters. Surprisingly, many quartz and feldspar crystals and associated colorless to light-colored interstitial glasses of the studied xenoliths are not low but high in delta O-18 (5.1-7.2 %, excluding three dark-brown glasses of 4-5 %). The xenoliths contain abundant, low-to high-delta O-18 (2.4-6.3 %) young zircons (U-Pb age 0.2-0.27 +/- 0.03 Ma; U-Th age 0.16 +/- 0.07 Ma), most of them in oxygen isotope equilibrium with interstitial glasses. The delta O-18 values >5.6 % recorded in the coexisting zircon, quartz, feldspar and colorless interstitial glass suggest crystallization from melts produced by fusion of crustal rocks altered by sea-water, also reflecting multiple melting and crystallization events. This suggests that "normal"-delta O-18 silicic magmas may not be ultimately produced by crystallization of mafic, basaltic magmas. Instead, our new single-crystal laser fluorination and ion microprobe O-isotope data suggest addition of diverse partial crustal melts, probably originated from variously altered and preconditioned crust. Article in Journal/Newspaper Iceland Max Planck Society: MPG.PuRe Contributions to Mineralogy and Petrology 169 5 |
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We have studied glass-bearing leucocratic (granitic to Qz-monzonitic) crustal xenoliths from the Tindfjoll Pleistocene volcanic complex, SW Iceland. The xenoliths consist of strongly resorbed relicts of anorthitic plagioclase, K-rich feldspar and rounded quartz in color-less through pale to dark-brown interstitial glass. Spongy clinopyroxene and/or rounded or elongated crystals of orthopyroxene are in subordinate amount. Magnetite, ilmenite, zircon, apatite, allanite and/or chevkinite are accessory minerals. The xenoliths more likely are relicts of earlier-formed, partially melted Si-rich rocks or quartz-feldspar-rich crystal segregations, which suffered latter interaction with hotter and more primitive magma(s). Icelandic lavas are typically low in delta O-18 compared to mantle-derived, "MORB"-like rocks (similar to 5.6 +/- 0.2 %), likely due to their interaction with, or contamination by, the upper-crustal rocks affected by rain and glacial melt waters. Surprisingly, many quartz and feldspar crystals and associated colorless to light-colored interstitial glasses of the studied xenoliths are not low but high in delta O-18 (5.1-7.2 %, excluding three dark-brown glasses of 4-5 %). The xenoliths contain abundant, low-to high-delta O-18 (2.4-6.3 %) young zircons (U-Pb age 0.2-0.27 +/- 0.03 Ma; U-Th age 0.16 +/- 0.07 Ma), most of them in oxygen isotope equilibrium with interstitial glasses. The delta O-18 values >5.6 % recorded in the coexisting zircon, quartz, feldspar and colorless interstitial glass suggest crystallization from melts produced by fusion of crustal rocks altered by sea-water, also reflecting multiple melting and crystallization events. This suggests that "normal"-delta O-18 silicic magmas may not be ultimately produced by crystallization of mafic, basaltic magmas. Instead, our new single-crystal laser fluorination and ion microprobe O-isotope data suggest addition of diverse partial crustal melts, probably originated from variously altered and preconditioned crust. |
format |
Article in Journal/Newspaper |
author |
Gurenko, A. Bindeman, I. Sigurdsson, I. |
spellingShingle |
Gurenko, A. Bindeman, I. Sigurdsson, I. To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths |
author_facet |
Gurenko, A. Bindeman, I. Sigurdsson, I. |
author_sort |
Gurenko, A. |
title |
To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths |
title_short |
To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths |
title_full |
To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths |
title_fullStr |
To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths |
title_full_unstemmed |
To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths |
title_sort |
to the origin of icelandic rhyolites: insights from partially melted leucocratic xenoliths |
publishDate |
2015 |
url |
http://hdl.handle.net/11858/00-001M-0000-0029-28D0-B |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
Contributions to Mineralogy and Petrology |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1007/s00410-015-1145-4 http://hdl.handle.net/11858/00-001M-0000-0029-28D0-B |
op_doi |
https://doi.org/10.1007/s00410-015-1145-4 |
container_title |
Contributions to Mineralogy and Petrology |
container_volume |
169 |
container_issue |
5 |
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1774719254436773888 |