학술논문
Zircon sensitive high mass-resolution ion microprobe U-Pb and fission-track ages for gabbros and sheeted dykes of the Taitao ophiolite, Southern Chile, and their tectonic implications
Document Type
Author abstract
Source
Island Arc. March, 2006, Vol. 15 Issue 1, p130, 13 p.
Subject
Language
English
ISSN
1038-4871
Abstract
To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1440-1738.2006.00513.x Byline: Ryo Anma (1), Richard Armstrong (2), Toru Danhara (3), Yuji Orihashi (4), Hideki Iwano (3) Keywords: emplacement; fission-track dating; ridge collision; ridge subduction; sensitive high mass-resolution ion microprobe; SHRIMP; Taitao ophiolite Abstract: Abstract The Late Miocene-Pliocene Taitao ophiolite is composed of a complete sequence of classic oceanic lithosphere and is exposed approximately 50 km southeast of the Chile triple junction, where the Chile Ridge subducts beneath the South American Plate. Gabbros and ultramafic rocks are folded into a complex pattern, but only evidence for block rotation has been reported in the overriding sheeted dyke complex. In the present study, sensitive high mass-resolution ion microprobe U-Pb and fission-track dating methods were applied to zircon crystals separated from gabbros and sheeted dykes. Two sets of radiometric ages of gabbros range between 5.9 [+ or -] 0.4 and 5.6 [+ or -] 0.1 Ma. These ages coincide within their error ranges and imply rapid intrusion and cooling of gabbros. The U-Pb age of a dacite dyke intruded into the sheeted dyke complex was determined to be 5.2 [+ or -] 0.2 Ma. These data indicate that the magmas of the Taitao ophiolite were formed during the 6 Ma Chile Ridge collision event and emplaced in a shorter period than previously thought. A short segment of the Chile Mid-oceanic Ridge must have been emplaced during the 6 Ma event. Author Affiliation: (1)Graduate School of Life and Environmental Sciences, University of Tsukuba, Ten-nodai 1-1-1, Tsukuba 305-8572, Japan (email:anma@arsia.geo.tsukuba.ac.jp), (2)Research School of Earth Sciences, Mills Road, Australian National University, Canberra 0200, Australian Capital Territory, Australia, (3)Kyoto Fission-Track Co. Ltd, Oomiya-Minami-Tajiri 44-4, Kita-Ku, Kyoto 603-8832, Japan and (4)Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, 113-0032, Japan Article History: Received 31 October 2005; accepted for publication 1 December 2005.