Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska
Subduction zone processes are challenging to study because of the rarity of good exposures and the complexity of rock relationships within accretionary prisms. We report the results of field mapping and petrographic, geochemical, and geochronological analyses of the McHugh Complex accretionary prism...
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crcansciencepubl:10.1139/cjes-2018-0268 2023-12-17T10:30:29+01:00 Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska Barefoot, John Nadin, Elisabeth S. Newberry, Rainer J. Camacho, Alfredo 2020 http://dx.doi.org/10.1139/cjes-2018-0268 http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjes-2018-0268 http://www.nrcresearchpress.com/doi/pdf/10.1139/cjes-2018-0268 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 57, issue 6, page 709-724 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 2020 crcansciencepubl https://doi.org/10.1139/cjes-2018-0268 2023-11-19T13:39:25Z Subduction zone processes are challenging to study because of the rarity of good exposures and the complexity of rock relationships within accretionary prisms. We report the results of field mapping and petrographic, geochemical, and geochronological analyses of the McHugh Complex accretionary prism mélange in south-central Alaska that was recently exposed due to retreat of the Nelchina Glacier. Our new mapping and analyses of the mélange, as well as adjacent Talkeetna arc intrusives, suggests that the previously mapped trace of the Border Ranges fault should shift northward in this location. Detailed petrographic analysis places this mélange exposure with the Potter Creek assemblage of the McHugh Complex. Blocks of pillow lavas within the mélange have both mid-ocean ridge basalt and intra-plate geochemical affinities, attesting to the complex relations of subduction-zone inputs in an alternating erosive–accretionary margin. A new zircon U–Pb age and geochemical analyses of a set of felsic dikes that cross-cut the accretionary sequence provide constraints on the regional tectonic evolution, including near-trench plutonism associated with the migration of a subducting spreading ridge along the southern Alaska margin during the Paleocene–Eocene. The McHugh section and cross-cutting dikes in this location are pervasively hydrothermally altered, which we attribute to elevated temperatures related to ridge subduction. Late-stage motion along the Border Ranges fault system, which is also recorded in the area, may also have contributed to the widespread alteration. Our data indicate that the Talkeetna volcanic arc and associated accretionary prism sediments were in their current configuration by 55 Ma. Article in Journal/Newspaper glacier Alaska Canadian Science Publishing (via Crossref) Canadian Journal of Earth Sciences 57 6 709 724 |
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Open Polar |
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Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences Barefoot, John Nadin, Elisabeth S. Newberry, Rainer J. Camacho, Alfredo Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska |
topic_facet |
General Earth and Planetary Sciences |
description |
Subduction zone processes are challenging to study because of the rarity of good exposures and the complexity of rock relationships within accretionary prisms. We report the results of field mapping and petrographic, geochemical, and geochronological analyses of the McHugh Complex accretionary prism mélange in south-central Alaska that was recently exposed due to retreat of the Nelchina Glacier. Our new mapping and analyses of the mélange, as well as adjacent Talkeetna arc intrusives, suggests that the previously mapped trace of the Border Ranges fault should shift northward in this location. Detailed petrographic analysis places this mélange exposure with the Potter Creek assemblage of the McHugh Complex. Blocks of pillow lavas within the mélange have both mid-ocean ridge basalt and intra-plate geochemical affinities, attesting to the complex relations of subduction-zone inputs in an alternating erosive–accretionary margin. A new zircon U–Pb age and geochemical analyses of a set of felsic dikes that cross-cut the accretionary sequence provide constraints on the regional tectonic evolution, including near-trench plutonism associated with the migration of a subducting spreading ridge along the southern Alaska margin during the Paleocene–Eocene. The McHugh section and cross-cutting dikes in this location are pervasively hydrothermally altered, which we attribute to elevated temperatures related to ridge subduction. Late-stage motion along the Border Ranges fault system, which is also recorded in the area, may also have contributed to the widespread alteration. Our data indicate that the Talkeetna volcanic arc and associated accretionary prism sediments were in their current configuration by 55 Ma. |
format |
Article in Journal/Newspaper |
author |
Barefoot, John Nadin, Elisabeth S. Newberry, Rainer J. Camacho, Alfredo |
author_facet |
Barefoot, John Nadin, Elisabeth S. Newberry, Rainer J. Camacho, Alfredo |
author_sort |
Barefoot, John |
title |
Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska |
title_short |
Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska |
title_full |
Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska |
title_fullStr |
Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska |
title_full_unstemmed |
Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska |
title_sort |
rock and age relationships within the talkeetna forearc accretionary complex in the nelchina area, southern alaska |
publisher |
Canadian Science Publishing |
publishDate |
2020 |
url |
http://dx.doi.org/10.1139/cjes-2018-0268 http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjes-2018-0268 http://www.nrcresearchpress.com/doi/pdf/10.1139/cjes-2018-0268 |
genre |
glacier Alaska |
genre_facet |
glacier Alaska |
op_source |
Canadian Journal of Earth Sciences volume 57, issue 6, page 709-724 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/cjes-2018-0268 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
57 |
container_issue |
6 |
container_start_page |
709 |
op_container_end_page |
724 |
_version_ |
1785583450165608448 |