Stress, strain, and B‐type olivine fabric in the fore‐arc mantle: Sensitivity tests using high‐resolution steady‐state subduction zone models
Stress, strain, and B‐type olivine fabric in the fore‐arc mantle: Sensitivity tests using high‐resolution steady‐state subduction zone models
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DOI：
10.1029/2006jb004544
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发表时间：
2007-04
影响因子：
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通讯作者：
E. Kneller;P. V. Keken;I. Katayama;S. Karato
中科院分区：
文献类型：
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作者：
E. Kneller;P. V. Keken;I. Katayama;S. Karato
[1]在几个俯冲系统的剪切波分裂观测表明，在弧前地幔沟平行的快速方向。地幔楔中B型橄榄石组构的存在可能为低温和水合条件下的各向异性模式提供了解释。敏感性测试，提供洞察B型织物的分布和规模，使用二维，高分辨率，运动学动态俯冲带模型。这些模型包括一个湿橄榄石流变学和一个模拟的弧前地幔与参数化的板和地幔楔之间的粘性耦合的aseperstic蠕变区。计算的热结构是在合理的协议与热流观测和Q层析成像少量的耦合和适量的剪切加热在孕震和无震蠕变区。这些少量的粘性耦合产生了一个缓慢流动的弧前地幔的热，应力和应变条件适合显着的B型织物的发展。在预测的B型区域中驱动地质显著流动所需的最小剪切应力对沿沿着无滑动蠕变区的剪切加热的大小敏感，范围从小于100到300 MPa。根据耦合和剪切加热的量，在B型区域产生足够的有限应变进行组构发展所需的最小时间约为1000万年。橄榄石织物的预测分布是一致的剪切波各向异性的模式与沟槽平行的快速偏振方向以上的前弧和快速旋转到沟槽垂直的弧和弧后。
[1] Shear-wave splitting observations at several subduction systems show trench-parallel fast directions in the fore-arc mantle. The presence of B-type olivine fabric in the mantle wedge may provide an explanation for this pattern of anisotropy under low-temperature and hydrated conditions. Sensitivity tests are shown that provide insights into the distribution and magnitude of B-type fabric using two-dimensional, high-resolution, kinematic-dynamic subduction zone models. These models include a wet olivine rheology and a simulated aseismic creep zone in the fore-arc mantle with parameterized viscous coupling between the slab and mantle wedge. The calculated thermal structure is in reasonable agreement with heat flow observations and Q tomography for small amounts of coupling and moderate amounts of shear heating in the seismogenic and aseismic creep zones. These small amounts of viscous coupling give rise to a slowly flowing fore-arc mantle with thermal, stress, and strain conditions suitable for significant B-type fabric development. The minimum shear stress necessary to drive geologically significant flow in the predicted B-type region is sensitive to the magnitude of shear heating along the aseismic creep zone and ranges from less than 100 to 300 MPa. The minimum time required to generate sufficient finite strain for fabric development in the B-type region is around 10 Myr depending on the amount of coupling and shear heating. The predicted distribution of olivine fabric is consistent with a pattern of shear wave anisotropy with trench-parallel fast polarization directions above the fore arc and a rapid rotation to trench-perpendicular in the arc and back arc.