Thermal structure beneath Tohoku, northeast japan
Thermal structure beneath Tohoku, northeast japan
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日本东北部东北部地下的热结构
DOI：
10.1016/0040-1951(85)90173-8
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发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
S. Honda
中科院分区：
文献类型：
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作者：
S. Honda
结合地球物理观测和岩石学的考虑，我们研究了东北（日本东北部）俯冲带的热模型。地幔楔较深部分的温度受到岩石学要求的限制，要求火山带下方有一个高温区（> 1400°C）。为了满足这一条件，即解释东北俯冲带的弧火山活动，需要日本海下的高温上地幔（在浅于100 km的深度可能为1400°C）。热流分布制约着浅部的温度结构，在海沟和火山锋面之间分布着20 ~ 50 mW/m2的低热流值，而在火山锋面的向陆区域（包括日本海）则持续存在着高热流值（80-120 mW/m2）。最近的热流测量结果表明，从低到高的热流转换发生在火山前缘和火山前缘之间。这种热流分布限制了地幔楔中热流的形式和作用于板块边界的剪应力。一个刚性（非移动）的三角形区域的俯冲板和垂直面下方的无源锋是必要的，以解释低热流区之间的沟槽和无源锋。在俯冲板片和刚性三角形地幔之间的界面上作用有约500 ~ 1000巴的剪应力。我们还认为，为了解释火山前缘附近的热流峰值，（> 120 mW/m2），岩浆迁移速率约为0.05 cm ~ 3 cm ~（-2）年~（-1）。表明南美洲中部地幔楔的温度可能低于东北俯冲带。这种差异可能导致火山岩性质的差异。
Combined with geophysical observations and petrological considerations, we have studied the thermal models of the Tohoku (northeast Japan) subduction zone. The temperature of the deeper part of the mantle wedge is constrained by the petrological requirements that demand a high-temperature region (> 1400°C) beneath the volcanic zone. To satisfy this condition, namely to explain the arc volcanism in the Tohoku subduction zone, a high-temperature upper mantle beneath the Japan Sea (possibly 1400°C at the depth shallower than 100 km) is required. Heat flow distribution, which constrains the temperature structure at shallower depth, shows that low heat-flow values ranging from 20 to 50 mW/m2are distributed between the trench and aseismic front and consistently high heat flow values (80–120 mW/m2) prevail in the area landward of the volcanic front including the Japan Sea. Recent heat flow measurements indicate that the transition from low to high heat flow occurs between the aseismic front and volcanic front. This heat flow distribution restricts the form of the flow in the mantle wedge and shear stress acting at the plate boundary. A rigid (non-moving) triangular region bounded by the subducting slab and the vertical plane beneath the aseismic front is necessary to explain the low-heat-flow zone between the trench and aseismic front. Shear stress of about 500 to 1000 bar is supposed to act at the interface between the subducting slab and rigid triangular mantle. We also suggest that, to explain the peak of heat flow near the volcanic front (> 120 mW/m2), magma migration rate of about 0.05 cm3cm−2year−1is necessary.A comparison of the thermal structure of the Tohoku subduction zone with that of the central South America, which was preliminary calculated by the similar scheme, shows that the temperature in the mantle wedge of the central South America is probably lower than that of the Tohoku subduction zone. This difference may result in that of the nature of volcanic rocks.