The Evolution of Arc Magmatism in the NE Honshu Arc, Japan
The Evolution of Arc Magmatism in the NE Honshu Arc, Japan
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日本本州弧东北部弧岩浆作用的演化
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发表时间：
2001
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通讯作者：
Takeyoshi Yoshida
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作者：
Takeyoshi Yoshida
东北大学研究生院理学研究科矿物学岩石学经济地质学研究所岛弧岩浆活动研究室，仙台，980-8578（2001年2月13日接收; 2001年3月30日接受）摘要：日本本州岛东北弧晚新生代火山岩的最新地质学和岩石学研究，揭示了岩浆作用方式的明显长期变化。火山活动有三个显著时期：陆缘期（66-21 Ma）、弧后盆地期（21-13 Ma）和岛弧期（13-0 Ma）。每个时期都有其独特的侧向碱变化模式，并与楔型地幔上部的热结构密切相关。岛弧阶段可分为4个阶段：海底火山作用阶段（13-8 Ma）、晚中新世破火山口形成阶段（8-5 Ma）、上新世破火山口形成阶段（5 ~ 1.7Ma）和挤压火山弧阶段（1.7 ~ 0 Ma）。岩浆活动方式的这些变化与以板块运动为主的应力状态和弧岩浆活动的演化阶段有关。地质学、岩石学和地球物理学的综合研究已成为揭示地壳内结构的宝贵工具。现今本州岛东北弧地壳中的热结构与晚新生代塌陷破火山口的分布密切相关。受岩浆库冷却的高温岩体现在一定存在于破火山口之下的中地壳深度，并且可能被观测为具有许多S波反射体的低速体。阐明晚新生代未出露岩体的破火山口与地震活动的密切关系将成为火山弧灾害性事件预测的主要目标之一.介绍
TAKEYOSHI YOSHIDAResearch Laboratory of Arc Magmatism, Institute of Mineralogy, Petrology and Economic Geology, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan (Received February 13, 2001 ; accepted March 30, 2001) Abstract : Recent geological and petrological studies for late Cenozoic volcanic rocks from the NE Honshu arc, Japan, revealed the presence of clear secular change of mode of magmatism. Three prominent periods of volcanic activity : continental margin (66-21 Ma), back-arc basin (21-13 Ma), and island-arc stage (13-0 Ma), are identical there. Each period has its unique pattern of lateral alkali variation that is closely related with the thermal structure of the uppermost wedge mantle. The island-arc stage can be divided into four phases : submarine volcanism (13-8 Ma), late Miocene caldera-forming phase (8-5 Ma), Pliocene caldera-forming phase (5-1.7 Ma) and compressional volcanic arc (1.7-0 Ma). These changes in the mode of igneous activity correlated with the stress regime mainly controlled by plate motion, and with the evolutional stage of arc magmatism. Combined geological, petrological, and geophysical studies have become a valuable tool in revealing intra-crustal structures. The thermal structures seen in the crust of the present NE Honshu arc are closely related to the distribution of the late Cenozoic collapse calderas. High temperature plutons under cooling from the magma reservoirs must be exist now at middle crustal depths under the calderas, and probably observed as low-velocity bodies with many S wave reflectors. To clarify the close relations between the late Cenozoic calderas with unexposed plutons and the seismicity will become one of the main target for predicting hazardous events at volcanic arcs.1. Introduction