Levin Vadim, Shapiro Nikolai, Park Jeffrey, Ritzwoller Michael
Department of Geology and Geophysics, Box 208109, Yale University, New Haven, Connecticut 06520, USA.
Nature. 2002 Aug 15;418(6899):763-7. doi: 10.1038/nature00973.
In the northwest Pacific Ocean, a sharp corner in the boundary between the Pacific plate and the North American plate joins a subduction zone running along the southern half of the Kamchatka peninsula with a region of transcurrent motion along the western Aleutian arc. Here we present images of the seismic structure beneath the Aleutian-Kamchatka junction and the surrounding region, indicating that: the subducting Pacific lithosphere terminates at the Aleutian-Kamchatka junction; no relict slab underlies the extinct northern Kamchatka volcanic arc; and the upper mantle beneath northern Kamchatka has unusually slow shear wavespeeds. From the tectonic and volcanic evolution of Kamchatka over the past 10 Myr (refs 3-5) we infer that at least two episodes of catastrophic slab loss have occurred. About 5 to 10 Myr ago, catastrophic slab loss shut down island-arc volcanic activity north of the Aleutian-Kamchatka junction. A later episode of slab loss, since about 2 Myr ago, seems to be related to the activity of the world's most productive island-arc volcano, Klyuchevskoy. Removal of lithospheric mantle is commonly discussed in the context of a continental collision, but our findings imply that episodes of slab detachment and loss are also important agents in the evolution of oceanic convergent margins.
在西北太平洋，太平洋板块与北美板块边界处的一个急转弯，将沿着堪察加半岛南半部延伸的俯冲带与阿留申弧西段的转换运动区域连接起来。在此，我们展示了阿留申 - 堪察加交界点及周边区域下方的地震结构图像，结果表明：俯冲的太平洋岩石圈在阿留申 - 堪察加交界点处终止；已熄灭的堪察加半岛北部火山弧下方不存在残留板块；堪察加半岛北部上地幔的剪切波速度异常缓慢。从堪察加半岛在过去1000万年（参考文献3 - 5）的构造和火山演化过程中，我们推断至少发生了两次灾难性的板块损失事件。大约在500万至1000万年前，灾难性的板块损失导致阿留申 - 堪察加交界点以北的岛弧火山活动停止。自大约200万年前以来的较晚一次板块损失事件，似乎与世界上最活跃的岛弧火山克柳切夫斯科伊火山的活动有关。岩石圈地幔的移除通常是在大陆碰撞的背景下进行讨论的，但我们的研究结果表明，板块脱离和损失事件在海洋汇聚边缘的演化过程中也是重要因素。
