Towards a more complete record of magmatism and exhumation in continental arcs, using detrital fission-track thermochrometry

Citation
Ji. Garver et al., Towards a more complete record of magmatism and exhumation in continental arcs, using detrital fission-track thermochrometry, PHYS CH P A, 25(6-7), 2000, pp. 565-570
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
PHYSICS AND CHEMISTRY OF THE EARTH PART A-SOLID EARTH AND GEODESY
ISSN journal
1464-1895 → ACNP
Volume
25
Issue
6-7
Year of publication
2000
Pages
565 - 570
Database
ISI
SICI code
1464-1895(2000)25:6-7<565:TAMCRO>2.0.ZU;2-K
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 th ick section of marine turbidites that were deposited in a 500 km long forea rc basin along the outboard edge of this convergent margin. It was structur ally overridden during the early Tertiary by an obducted island are, the Ol ytorsky 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 contine ntal are, which provided much of the sediment for the Ukalayat. Because all sandstones contain a large fraction of first-cycle volcanic zircons (euhed ral, colorless), we infer that the youngest component of the FT grain age d istribution, designated P1, closely approximates the time of deposition. Tw enty-seven samples have yielded P1 ages ranging from similar to 44 to 88 Ma , which indicates continuous magmatic activity in the are from the Late Cre taceous to Middle Eocene. A second component (P2) records progressive exhum ation of the basement to the Okhotsk-Chukotka are. The difference between P 1 and P2 ages indicates steady exhumation at similar to 200-400 m/Myr from similar to 90 to 44 Ma. This finding implies the removal of 9 to 18 km of r ock in the most deeply exhumed parts of the source region. A change in exhu mation rates at similar to 70 Ma may coincide with an eastward shift in the locus of volcanism from the Okhotsk-Chukotka are to the younger Western Ka mchatka-Koryak are. (C) 2000 Elsevier Science Ltd. All rights reserved.