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首页> 外文期刊>Acta Geologica Sinica - English Edition >A Kinematic Thermal Model for Descending Slabs with Velocity Boundary Layers: A Case Study for the Tonga Subducting Slab
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A Kinematic Thermal Model for Descending Slabs with Velocity Boundary Layers: A Case Study for the Tonga Subducting Slab

机译：具有速度边界层的平板下降的运动学热学模型：以汤加俯冲平板为例

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摘要

For the purpose of investigating the influence of metastable olivine (MO) phase transformations on both deep seismicity and stagnation of slabs, we constructed a 2-dimensional finite element thermal model for a 120 Ma-old 50° dipping oceanic lithosphere descending at 10 cm/yr with velocity boundary layers, which would mitigate the interference of constant velocity field for the slab. The resulting temperatures show that most of intermediate and deep earthquakes occurring within the Tonga slab are occurring inside the 800°C and 1200°C isotherm, respectively. The elevation of olivine transformation near ～410 km and respective persistence of metastable olivine and spinel within the transition zone and beneath 660 km would thus result in bimodal positive, zonal, negative density anomalies, respectively. These results together with the resulting pressure anomalies may reflect the stress pattern of the Tonga slab: (i) slab pull force exerts above a depth of ～230 km; (ii) MO existence changes the buoyancy force within the transition zone and facilitates slab stagnation at a depth of 660 km; (iii) as the subducting materials accumulated over 660 km, deepest earthquakes occur due to MO transformation; (iv) a flattened ‘slab’ may penetrate into the lower mantle due to the density increment of Sp transformation.
机译：为了研究亚稳橄榄石（MO）相变对深地震活动和平板停滞的影响，我们构建了一个120 Ma的，倾斜50°，倾角为10 cm /的海洋岩石圈的二维有限元热模型。带有速度边界层的yr，这将减轻板坯等速场的干扰。由此产生的温度表明，汤加板块内发生的大多数中级地震和深部地震分别发生在800°C和1200°C等温线内。约410 km附近橄榄石转变的抬高以及过渡带内和660 km以下亚稳态橄榄石和尖晶石的持续存在，将分别导致双峰正，纬向和负密度异常。这些结果以及所产生的压力异常可能反映了汤加板的应力模式：（i）板拉力在〜230 km深度以上施加； （ii）MO的存在改变了过渡带内的浮力，并促进了660 km深度的平板停滞； （iii）由于俯冲物质累积超过660公里，由于MO转换而发生了最深的地震； （iv）由于Sp转换的密度增加，扁平的“平板”可能会渗透到下地幔中。

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