Rheologic controls on the dynamics of slab detachment
Rheologic controls on the dynamics of slab detachment
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DOI：
10.1016/j.tecto.2007.09.004
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发表时间：
2009-01
期刊：
影响因子：
2.9
通讯作者：
E. R. Andrews;M. Billen
中科院分区：
文献类型：
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作者：
E. R. Andrews;M. Billen
俯冲岩石圈（板块）的剥离已被提出在一些地方作为观察到的火山活动和区域构造演化的原因。例如，亚得里亚海隆起的沿走向进展和跨墨西哥火山带火山活动的自西向东进展可能是由俯冲板片的传播剥离引起的。了解板片脱离的动力学是必要的脱离的时间与地面观测。我们证明使用二维（2D）的数值模型，俯冲岩石圈的拆离的时间，发生，和表面的影响是强烈依赖于岩石圈的刚度（即应力粘性支持）和上地幔的流变性。特别是，在模型与牛顿上地幔塑性屈服是唯一的削弱过程中板，脱离不会发生。考虑非牛顿上地幔变形的模型表明了两种分离模式：（1）由板片加热控制的强板片（最大屈服强度为500 MPa或更大）的缓慢而深度的分离，以及（2）较弱板片（300 MPa）的快速而浅层的分离由板片内部的屈服控制。对于最大屈服强度为500 MPa的板，脱离的时间随板的年龄（年龄范围为40至120 My）而增加，表明脱离时间受板的综合刚度控制，这限制了下沉率。然而，较弱的板块（300 MPa）的剥离时间是独立的年龄，因为较弱的板块下沉迅速，剥离的时间是有限的周围地幔的流动速率。
The detachment of subducted lithosphere (slabs) has been proposed in a number of locations as the cause for observed volcanism and regional tectonic evolution. For example, along-strike progression of uplift in the Adriatic Sea and west-to-east progression of volcanism in the Trans-Mexican Volcanic Belt may be caused by propagating detachment of subducted slabs. An understanding of the dynamics of slab detachment is necessary to relate the timing of detachment to surface observations. We demonstrate using two-dimensional (2D) numerical models that the timing, occurrence, and surface effects resulting from the detachment of subducted lithosphere are strongly dependent upon the stiffness (i.e. stress supported viscously) of the lithosphere and rheology of the upper mantle. In particular, in models with a Newtonian upper mantle where plastic yielding is the only weakening process within the slab, detachment does not occur. Models accounting for non-Newtonian upper mantle deformation demonstrate two modes of detachment: (1) slow and deep detachment of strong slabs (500 MPa or greater maximum yield strength) controlled by heating of the slab, and (2) fast and shallow detachment of weaker slabs (300 MPa) controlled by yielding within the slab interior. For slabs with a maximum yield strength of 500 MPa, the time to detachment increases with slab age (for ages ranging from 40 to 120 My), indicating that detachment time is controlled by the integrated stiffness of the slab, which limits the sinking rate. However, the detachment time for weaker slabs (300 MPa) is independent of age because weaker slabs sink rapidly, and the time to detachment is limited by the rate of flow of the surrounding mantle.