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Detrital zircon Hf isotopic compositions indicate a northern Caledonian connection for the Alexander terrane
Stockholm University, Faculty of Science, Department of Geological Sciences.
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2013 (English)In: Lithosphere, ISSN 1941-8264, Vol. 5, no 2, 163-168 p.Article in journal (Refereed) Published
Abstract [en]

Various plate reconstructions predict that the Alexander terrane, a Neoproterozoic-Jurassic crustal fragment now located in the North American Cordillera, evolved in proximity to the northern Appalachian-Caledonian convergent margin during assembly of supercontinent Laurussia. To test stratigraphic connections with Laurussia that are implied by these plate reconstructions, we measured the Hf isotopic compositions of 176 detrital zircons from two relevant sedimentary sequences of the Alexander terrane. An older, Upper Silurian-Lower Devonian terrestrial to shallow-marine molasse sequence yields 405-490 Ma detrital zircons with negative epsilon(Hf(t)) values and Mesoproterozoic to Paleoproterozoic Hf model ages. In combination with paleomagnetic and biogeographic constraints, these Hf data argue for the molasse strata to be now-displaced equivalents of the Old Red Sandstone and primarily sourced from crustally contaminated granitoids in the Greenland, Svalbard, or British Caledonides. Late Silurian-Early Devonian orogenesis in the Alexander terrane is therefore likely related to the Scandian-Salinic phase of Appalachian-Caledonian mountain building. Younger, Middle Devonian sequences of the Alexander terrane are endowed in 390-490 Ma detrital zircons with positive epsilon(Hf(t)) values and Neoproterozoic Hf model ages. These isotopic signatures are consistent with the erosion of local basement rocks during the opening of the Slide Mountain-Angayucham backarc rift and tectonic separation of the Alexander terrane from northern Laurussia.

Place, publisher, year, edition, pages
2013. Vol. 5, no 2, 163-168 p.
National Category
Geophysics Geochemistry Geology
URN: urn:nbn:se:su:diva-93592DOI: 10.1130/L255.1ISI: 000322545600001OAI: diva2:647056


Funding Agencies:

Geo-mapping for Energy and Minerals program at Natural Resources Canada 2012270; National Science Foundation EAR-0948359,  EAR-1049368,   EAR-1032156 

Available from: 2013-09-10 Created: 2013-09-10 Last updated: 2013-10-21Bibliographically approved

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Beranek, Luke P.
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