New seismological constraints on growth of continental crust in the Izu-Bonin intra-oceanic arc
New seismological constraints on growth of continental crust in the Izu-Bonin intra-oceanic arc
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DOI：
10.1130/g23901a.1
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发表时间：
2007-11
期刊：
影响因子：
5.8
通讯作者：
S. Kodaira;Takeshi Sato;N. Takahashi;S. Miura;Y. Tamura;Y. Tatsumi;Y. Kaneda
中科院分区：
文献类型：
--
作者：
S. Kodaira;Takeshi Sato;N. Takahashi;S. Miura;Y. Tamura;Y. Tatsumi;Y. Kaneda
大陆地壳的形成过程并不十分清楚，尽管这种地壳大多形成于今天的板块边缘。因此，必须研究现代洋内弧，如西太平洋常见的洋内弧。沿着具有代表性的伊豆-小笠原洋内弧的沿着新的地震研究提供了弧壳和上地幔的独特的沿走向图像，以补充早期的跨弧岩石圈剖面。这揭示了两个尺度（1000-10公里尺度）的变化，一个是伊豆与小笠原弧壳（厚与薄）的尺度，另一个是火山间（1050公里）的尺度。这些图像显示：（1）伊豆-小笠原弧壳的整体成分比典型的陆壳更基性，（2）地震速度与陆壳相似的中地壳主要位于玄武岩弧火山之下，（3）玄武岩弧火山之下的整体成分在厚弧段和薄弧段变化不大，（4）下地壳成分返回地幔的过程，如拆沉，是弧壳演化为陆壳的必要条件。伊豆-小笠原地壳的继续增厚，伴随着最低地壳的拆沉，可以产生典型的大陆地壳速度结构。
The process by which continental crust has formed is not well understood, though such crust mostly forms at convergent plate margins today. It is thus imperative to study modern intra-oceanic arcs, such as those common in the western Pacific Ocean. New seismic studies along the representative Izu-Bonin intra-oceanic arc provide unique along-strike images of arc crust and uppermost mantle to complement earlier, cross-arc lithospheric profiles. These reveal two scales (1000–10 km scale) of variations, one at the scale of the Izu versus Bonin (thick versus thin) arc crust, the other at the intervolcano (∼50 km) scale. These images show that: (1) the bulk composition of the Izu-Bonin arc crust is more mafic than typical continental crust, (2) the middle crust with seismic velocities similar to continental crust is predominantly beneath basaltic arc volcanoes, (3) the bulk composition beneath basaltic volcanoes changes little at thick and thin arc segments, and (4) a process to return lower crustal components to the mantle, such as delamination, is required for an arc crust to evolve into continental crust. Continued thickening of the Izu-Bonin crust, accompanied by delamination of lowermost crust, can yield velocity structure of typical continental crust.