Towards a more complete record of magmatism and exhumation in continental arcs,using detrital fission-track thermochrometry |
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| Institution: | 1. Department of Geophysical Engineering, Suleyman Demirel University, Çünür 32260, Isparta, Turkey;2. Department of Geophysical Engineering, Istanbul University, Avc?lar 34320, Istanbul, Turkey;3. Department of Geological Engineering, Istanbul University, Avc?lar 34320, Istanbul, Turkey;1. Federal State Institution of Science Geological Institute of Russian Academy of Sciences, Pyzhevsky lane 7, Moscow 119017, Russian Federation;2. Federal State Unitary Enterprise “A.P.Karpinsky Russian Geological Research Institute”, 74, Sredny prospect, 199106 Saint-Petersburg, Russian Federation;3. GeoSep Service, 1521 Pine Cone Road, ID 83843, USA;4. Rosneft Oil Company, Dubininskaya str., 31A, 115054 Moscow, Russian Federation;5. Institute of Earth Sciences, St.-Petersburg State University, Universitetskaya emb., 7/9, St-Petersburg, Russian Federation;1. Dipartimento di Biologia, Ecologia e Scienze della Terra, Università della Calabria, 87036 Arcavacata di Rende, CS, Italy;2. Departamento de Ciencias de la Tierra y del Medio Ambiente, Universidad de Alicante, Ap. 99, E-03080 Alicante, Spain;1. Departamento de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, PO Box 644, E-48080 Bilbao, Spain;2. Departamento de Geodinámica, Facultad de Ciencia y Tecnología, PO Box 644, E-48080 Bilbao, Spain;3. Servicio General de Geocronología y Geoquímica Isotópica — SGIker-IBERCRON, PO Box 644, E-48080 Bilbao, Spain;4. Departamento de Geodinámica, Facultad de Farmacia Universidad del País Vasco, UPV/EHU, de la Universidad, 7, E-01006 Vitoria, Spain;5. Equipe de Géochimie — Laboratoire Magmas & Volcans UMR6524 CNRS & Université B. Pascal, 5 Rue Kessler, 63038 Clermont-Ferrand cedex, France |
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| Abstract: | The NE Asian margin was the locus of an Andean-style subduction zone during most of the Mesozoic and Cenozoic. The Ukelayat flysch is a 10 to 15 km thick section of marine turbidites that were deposited in a 500 km long forearc basin along the outboard edge of this convergent margin. It was structurally overridden during the early Tertiary by an obducted island arc, the Olytorsky terrane. We present new fission-track (FT) grain ages from unreset detrital zircons. These data provide precise information about depositional age of the Ukelayat and the temporal evolution of the Asian margin continental arc, which provided much of the sediment for the Ukalayat. Because all sandstones contain a large fraction of first-cycle volcanic zircons (euhedral, colorless), we infer that the youngest component of the FT grain age distribution, designated P1, closely approximates the time of deposition. Twenty-seven samples have yielded P1 ages ranging from ~44 to 88 Ma, which indicates continuous magmatic activity in the arc from the Late Cretaceous to Middle Eocene. A second component (P2) records progressive exhumation of the basement to the Okhotsk-Chukotka arc. The difference between P1 and P2 ages indicates steady exhumation at ~200–400 m/Myr from ~90 to 44 Ma. This finding implies the removal of 9 to 18 km of rock in the most deeply exhumed parts of the source region. A change in exhumation rates at ~70 Ma may coincide with an eastward shift in the locus of volcanism from the Okhotsk-Chukotka arc to the younger Western Kamchatka-Koryak arc. |
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