Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan
<p>Zircon grains preserve records of crystallization, growth, and/or deformation that can be envisaged from their internal structures and through the U–Pb isotope analysis. Electron backscatter diffraction (EBSD) is a non-destructive method for visualizing undeformed domains to differentiate t...
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| Format: | Article |
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Copernicus Publications
2023-12-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/35/1079/2023/ejm-35-1079-2023.pdf |
| _version_ | 1797404179705102336 |
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| author | H. U. Rehman T. Kagoshima T. Kagoshima N. Takahata Y. Sano Y. Sano F. Barou D. Mainprice H. Yamamoto |
| author_facet | H. U. Rehman T. Kagoshima T. Kagoshima N. Takahata Y. Sano Y. Sano F. Barou D. Mainprice H. Yamamoto |
| author_sort | H. U. Rehman |
| collection | DOAJ |
| description | <p>Zircon grains preserve records of crystallization, growth, and/or deformation that can be envisaged from their internal structures and through the U–Pb isotope analysis. Electron backscatter diffraction (EBSD) is a non-destructive method for visualizing undeformed domains to differentiate them from those that are plastically deformed. In this study, we report EBSD analyses conducted on zircon grains, in thin sections with available textural information, from Himalayan eclogites. The studied eclogite samples show no petrographic evidence of shearing or mylonitization. However, several zircon grains preserve plastically deformed domains. These deformed domains display several degrees of misorientation relative to the undeformed domain and yielded geologically reset ages when analysed for U–Pb isotope ratios using nanoscale secondary ion mass spectrometry (NanoSIMS), in contrast to most undeformed domains which retained the protolith age. The degree of resetting is positively correlated with the extent of misorientation. These pieces of evidence indicate that plastic deformation in zircon grains, equilibrated at higher pressure–temperature conditions, affected the primary geochemical and geochronological records. Based on these observations, we assume that not only regional shearing/mylonitization in metamorphic rocks affects the geochemical records, but also that zircon grains in apparently unsheared high-grade metamorphic rocks behave plastically. The micro-scale intra-grain plastically deformed domains can easily be identified through EBSD analysis in the form of crystallographic misorientations. To extract meaningful geochronological results, it is necessary to identify undisturbed domains in zircon grains before applying any destructive analytical method.</p> |
| first_indexed | 2024-03-09T02:51:12Z |
| format | Article |
| id | doaj.art-6a125e95e5a34ef4979c1a0c059eac78 |
| institution | Directory Open Access Journal |
| issn | 0935-1221 1617-4011 |
| language | English |
| last_indexed | 2024-03-09T02:51:12Z |
| publishDate | 2023-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | European Journal of Mineralogy |
| spelling | doaj.art-6a125e95e5a34ef4979c1a0c059eac782023-12-05T11:02:16ZengCopernicus PublicationsEuropean Journal of Mineralogy0935-12211617-40112023-12-01351079109010.5194/ejm-35-1079-2023Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, PakistanH. U. Rehman0T. Kagoshima1T. Kagoshima2N. Takahata3Y. Sano4Y. Sano5F. Barou6D. Mainprice7H. Yamamoto8Graduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, JapanAtmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, JapanGraduate School of Science and Engineering, University of Toyama, Toyama, 930-8555, JapanAtmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, JapanAtmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, JapanCenter for Advanced Marine Core Research, Kochi University, Kochi, 783-8502, JapanGéosciences Montpellier UMR CNRS 5243, Université de Montpellier, Montpelier, 34095, FranceGéosciences Montpellier UMR CNRS 5243, Université de Montpellier, Montpelier, 34095, FranceGraduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, Japan<p>Zircon grains preserve records of crystallization, growth, and/or deformation that can be envisaged from their internal structures and through the U–Pb isotope analysis. Electron backscatter diffraction (EBSD) is a non-destructive method for visualizing undeformed domains to differentiate them from those that are plastically deformed. In this study, we report EBSD analyses conducted on zircon grains, in thin sections with available textural information, from Himalayan eclogites. The studied eclogite samples show no petrographic evidence of shearing or mylonitization. However, several zircon grains preserve plastically deformed domains. These deformed domains display several degrees of misorientation relative to the undeformed domain and yielded geologically reset ages when analysed for U–Pb isotope ratios using nanoscale secondary ion mass spectrometry (NanoSIMS), in contrast to most undeformed domains which retained the protolith age. The degree of resetting is positively correlated with the extent of misorientation. These pieces of evidence indicate that plastic deformation in zircon grains, equilibrated at higher pressure–temperature conditions, affected the primary geochemical and geochronological records. Based on these observations, we assume that not only regional shearing/mylonitization in metamorphic rocks affects the geochemical records, but also that zircon grains in apparently unsheared high-grade metamorphic rocks behave plastically. The micro-scale intra-grain plastically deformed domains can easily be identified through EBSD analysis in the form of crystallographic misorientations. To extract meaningful geochronological results, it is necessary to identify undisturbed domains in zircon grains before applying any destructive analytical method.</p>https://ejm.copernicus.org/articles/35/1079/2023/ejm-35-1079-2023.pdf |
| spellingShingle | H. U. Rehman T. Kagoshima T. Kagoshima N. Takahata Y. Sano Y. Sano F. Barou D. Mainprice H. Yamamoto Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan European Journal of Mineralogy |
| title | Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan |
| title_full | Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan |
| title_fullStr | Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan |
| title_full_unstemmed | Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan |
| title_short | Electron backscatter diffraction analysis combined with NanoSIMS U–Pb isotope data reveal intra-grain plastic deformation in zircon and its effects on U–Pb age: examples from Himalayan eclogites, Pakistan |
| title_sort | electron backscatter diffraction analysis combined with nanosims u pb isotope data reveal intra grain plastic deformation in zircon and its effects on u pb age examples from himalayan eclogites pakistan |
| url | https://ejm.copernicus.org/articles/35/1079/2023/ejm-35-1079-2023.pdf |
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