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
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
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DOI：
10.1111/j.1440-1738.2006.00513.x
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发表时间：
2006-03-01
期刊：
影响因子：
1.5
通讯作者：
Iwano, H
中科院分区：
文献类型：
--
作者：
Anma, R;Armstrong, R;Iwano, H
晚中新世-上新世泰陶蛇绿岩由一个完整的经典大洋岩石圈序列组成，暴露在智利三联结处东南约50公里处，智利海脊俯冲到南美板块之下。辉长岩和超镁铁质岩石被折叠成复杂的模式，但只有在覆盖层状岩墙杂岩中有块体旋转的证据。本文采用高质量分辨离子探针U-Pb和裂变径迹测年方法对辉长岩和片状岩墙中的锆石晶体进行了研究。辉长岩的两套放射性年龄介于5.9±-0.4 Ma和5.6±-0.1 Ma之间。这些年龄在误差范围内重合，暗示辉长岩的快速侵入和冷却。侵入片状岩墙杂岩的英安岩墙的U-Pb值为5.2+/-0.2 Ma。这些资料表明，太陶蛇绿岩的岩浆形成于6 Ma智利山脊碰撞事件期间，侵位时间比以往认为的要短。智利大洋中脊的一小段一定是在6 Ma事件期间侵位的。
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 +/- 0.4 and 5.6 +/- 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 +/- 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.