The odyssey of the Cache Creek terrane,Canadian Cordillera: Implications for accretionary orogens,tectonic setting of Panthalassa,the Pacific superwell,and break-up of Pangea |
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| Institution: | 1. Geological Survey of Canada, 1500-605 Robson Street, Vancouver, BC V6B 5J3, Canada;2. Dept. Earth and Environmental Sciences, University of Waterloo, ON N2L 3G1, Canada;3. Geological Survey of Canada, 601 Booth St., Ottawa, ON K1A 0E8, Canada;4. Dept. Earth and Environmental Sciences, 115 Trowbridge Hall, University of Iowa, Iowa City, IA 52242, USA;5. Instituto de Ciencias Polares y Ambientales ICPA, Universidad de Tierra del Fuego-CONICET, Fueguia Basket 251, 9410 Ushuaia, Tierra del Fuego, Argentina;6. Department of Earth Sciences, Oxford University, Parks Road, Oxford 0X1 3PR, UK;7. Departament de Cristallografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona, C/Martí i Franquès, s/n, 08028 Barcelona, Spain;1. School of Earth, Atmosphere & Environment, Monash University, Melbourne, VIC 3800, Australia;2. Department of Earth Sciences, University of St. Andrews, St. Andrews KY16 9AL, UK;3. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;4. School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;5. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China |
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| Abstract: | The Cache Creek terrane (CCT) of the Canadian Cordillera consists of accreted seamounts that originated adjacent to the Tethys Ocean in the Permian. We utilize Potential Translation Path plots to place quantitative constraints on the location of the CCT seamounts through time, including limiting the regions within which accretion events occurred. We assume a starting point for the CCT seamounts in the easternmost Tethys at 280 Ma. Using reasonable translation rates (11 cm/a), accretion to the Stikinia–Quesnellia oceanic arc, which occurred at about 230 Ma, took place in western Panthalassa, consistent with the mixed Tethyan fauna of the arc. Subsequent collision with a continental terrane, which occurred at about 180 Ma, took place in central Panthalassa, > 4000 km west of North America yielding a composite ribbon continent. Westward subduction of oceanic lithosphere continuous with the North American continent from 180 to 150 Ma facilitated docking of the ribbon continent with the North American plate.The paleogeographic constraints provided by the CCT indicate that much of the Canadian Cordilleran accretionary orogen is exotic. The accreting crustal block, a composite ribbon continent, grew through repeated collisional events within Panthalassa prior to docking with the North American plate. CCT's odyssey requires the presence of subduction zones within Panthalassa and indicates that the tectonic setting of the Panthalassa superocean differed substantially from the current Pacific basin, with its central spreading ridge and marginal outward dipping subduction zones. A substantial volume of oceanic lithosphere was subducted during CCT's transit of Panthalassa. Blanketing of the core by these cold oceanic slabs enhanced heat transfer out of the core into the lowermost mantle, and may have been responsible for the Cretaceous Normal Superchron, the coeval Pacific-centred mid-Cretaceous superplume event, and its lingering progeny, the Pacific Superswell. Far field tensile stress attributable to the pull of the slab subducting beneath the ribbon continent from 180 to 150 Ma instigated the opening of the Atlantic, initiating the dispersal phase of the supercontinent cycle by breaking apart Pangea. Docking of the ribbon continent with the North American plate at 150 Ma terminated the slab pull induced stress, resulting in a drastic reduction in the rate of spreading within the growing Atlantic Ocean. |
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