Synmetamorphic structural evolution of the Seward Peninsula blueschist terrane,Alaska |
| |
| Institution: | 1. Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, Modena, Italy;2. Department of Biomedical, Metabolic and Neurosciences, University of Modena and Reggio Emilia, Modena, Italy;3. Department of Earth, Environment and Life Sciences, University of Genova, Genova, Italy;4. Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy;5. Asbestos TEM Laboratories, 600 Bancroft Way, Suite A, Berkeley, CA, USA;6. Department of Environmental Engineering Sciences, University of Florida, Gainesville, USA;1. Laboratoire Chrono-environnement UMR CNRS 6249, Université Bourgogne Franche-Comté, F-25000 Besançon, France;2. Sorbonne Universités, UMR 7193, UPMC Univ. Paris VI, ISTEP, F-75005 Paris, France;1. Geological Institute, Basel University, Bernoullistrasse 32, 4055 Basel, Switzerland;2. Department of Geology, Tromsø University, Dramsveien 201, 9037 Tromsø, Norway;3. Institut des Sciences de la Terre d''Orléans (ISTO), Université d''Orléans, 45071 Orléans, France;1. Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS)/GEMOC, Department of Earth and Planetary Sciences, Macquarie University, Sydney NSW 2109, Australia;2. Géosciences Environnement Toulouse (GET), CNRS, CNES, IRD, Université Toulouse III, 14 avenue E. Belin, 31400 Toulouse, France;3. Department of Geophysics, Division of Earth and Planetary Sciences, Kyoto University, Kyoto 606-8502, Japan;4. Institute for Earth Sciences (ISTE), University of Lausanne, UNIL Mouline, Géopolis, 1015 Lausanne, Switzerland;1. College of Material Science & Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, China;2. Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology, Nanjing Institute of Technology, Nanjing 211167, China |
| |
| Abstract: | Blueschist-facies rocks of the central Seward Peninsula cropout over 8000 km2. Protoliths were Lower Paleozoic-Precambrian(?) shallow-water miogeoclinal sediments that were metamorphosed during the Middle Jurassic. Thermobarometric estimates yield ‘peak’ metamorphic conditions of 10–12 kbar at 460 ± 30°C. Crystallization of blueschist-facies minerals was synkinematic with development of a transposition foliation. This foliation is parallel to lithologic contacts and is axial planar to recumbent mesoscopic isoclinal folds. These folds are refolded by larger scale recumbent tight to isoclinal folds. Both fold sets have hinges parallel to a well-developed N—S stretching lineation. Sheath folds are also present. The long axes of the sheath folds also parallel the stretching lineation. This deformation was non-coaxial as indicated by microstructures and quartz c-axis fabrics. Folds nucleated, then rotated into parallelism with the stretching direction. Kinematic indicators show unequivocal top-to-the-north shear sense, compatible with blueschist formation during mid-Jurassic collision between the Brooks Range continental margin and a N-facing island arc (Yukon-Koyukuk). Convergence of these two plates is believed to have been nearly N—S (in present co-ordinates). |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
