Precise ages and isotopic constraints for the Lewis Hills (Bay of Islands Ophiolite): Preservation of an arc–spreading ridge intersection

Michaela Kurth,Klaus Mezger,Andreas Sassen,Günter Suhr

doi:10.1130/0091-7613(1998)026<1127:paaicf>2.3.co;2

Michaela Kurth, Klaus Mezger + Show 2 more

https://doi.org/10.1130/0091-7613(1998)026<1127:paaicf>2.3.co;2

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Research Article| December 01, 1998 Precise ages and isotopic constraints for the Lewis Hills (Bay of Islands Ophiolite): Preservation of an arc–spreading ridge intersection Michaela Kurth; Michaela Kurth 1Institut für Mineralogie und Geochemie, Universität Köln, Zülpicher Strasse 49b, 50674 Köln, Germany2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany Search for other works by this author on: GSW Google Scholar Andreas Sassen; Andreas Sassen 1Institut für Mineralogie und Geochemie, Universität Köln, Zülpicher Strasse 49b, 50674 Köln, Germany2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany Search for other works by this author on: GSW Google Scholar Günter Suhr; Günter Suhr 1Institut für Mineralogie und Geochemie, Universität Köln, Zülpicher Strasse 49b, 50674 Köln, Germany2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany Search for other works by this author on: GSW Google Scholar Klaus Mezger Klaus Mezger 2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany3Institut für Mineralogie, Universität Münster, Corrensstrasse 24, 48149 Münster, Germany Search for other works by this author on: GSW Google Scholar Author and Article Information Michaela Kurth 1Institut für Mineralogie und Geochemie, Universität Köln, Zülpicher Strasse 49b, 50674 Köln, Germany2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany Andreas Sassen 1Institut für Mineralogie und Geochemie, Universität Köln, Zülpicher Strasse 49b, 50674 Köln, Germany2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany Günter Suhr 1Institut für Mineralogie und Geochemie, Universität Köln, Zülpicher Strasse 49b, 50674 Köln, Germany2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany Klaus Mezger 2Max-Planck-Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany3Institut für Mineralogie, Universität Münster, Corrensstrasse 24, 48149 Münster, Germany Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1998) 26 (12): 1127–1130. https://doi.org/10.1130/0091-7613(1998)026<1127:PAAICF>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Michaela Kurth, Andreas Sassen, Günter Suhr, Klaus Mezger; Precise ages and isotopic constraints for the Lewis Hills (Bay of Islands Ophiolite): Preservation of an arc–spreading ridge intersection. Geology 1998;; 26 (12): 1127–1130. doi: https://doi.org/10.1130/0091-7613(1998)026<1127:PAAICF>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Lewis Hills, the southernmost massif of the Bay of Islands Ophiolite, exposes a prominent shear zone. The origin of this shear zone is pivotal with respect to the interpretation of the tectonic setting of the Lewis Hills and the genesis of the Bay of Islands Ophiolite. Different models suggest that the shear zone represents a fracture zone that separates either oceanic lithospheres of similar origin or the lithospheres of an island arc and a marginal basin. A contrasting model disputes the fracture zone setting. New U-Pb zircon ages of the Lewis Hills combined with Sm-Nd systematics are used to resolve this controversy. In the western part of the Lewis Hills (Western Lewis Hills), magmatic zircons from two trondhjemite bodies yield U-Pb ages of 500.6 ± 2.0 Ma and 503.7 ± 3.2 Ma. Initial ϵNd(502 Ma) values for trondhjemites and gabbros range from −1.5 to +2.0. Both the mineral ages and Nd signature are similar to those of the island-arc –related Little Port Complex, which is located to the north of the Western Lewis Hills. In contrast, apatite from a gabbro of the eastern part of the Lewis Hills (Eastern Lewis Hills) yields a concordant U-Pb age of 485.0 ± 1.0 Ma. This gabbro has an ϵNd(485 Ma) of +7.4. The age and isotope signature link the Eastern Lewis Hills with the northern marginal-basin–related massifs of the Bay of Islands Ophiolite. The significant differences of ages and isotope characteristics of the Western and Eastern Lewis Hills support the interpretation of the shear zone as the major tectonic boundary between an island arc and a marginal basin. This complex tectonic setting may have resulted in a wide spectrum of magma compositions that involved both island arc and marginal basin sources. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

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