Deep decoupling in subduction zones: Observations and temperature limits
Deep decoupling in subduction zones: Observations and temperature limits
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DOI：
10.1130/ges02278.1
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发表时间：
2020-12-01
期刊：
影响因子：
2.5
通讯作者：
Wilson, Cian R.
中科院分区：
文献类型：
--
作者：
Abers, Geoffrey A.;van Keken, Peter E.;Wilson, Cian R.
板块界面在发震深度和次弧深度之间经历了两次过渡。在20-50公里深度发生脆性-韧性转变，随后在类似80公里深度发生与上覆地幔楔完全粘性耦合的转变。我们回顾了这两种转变的证据，重点是热流和地震衰减对更深转变的限制。随着温度的升高，中间的韧性剪切带可能会明显减弱，因此其流变学对俯冲带热结构的控制比摩擦剪切加热更强。我们通过解析近似和二维有限元模型对理想俯冲带和类似真实俯冲带的几何形状进行了评估。我们表明，在剪切区存在温度缓冲过程，导致温度被该剪切区材料的流变强度严格控制，从而导致浅层脆性区域的广泛剪切加热行为。较高的温度导致剪切带变弱，因此产生的热量减少，因此温度停止上升，剪切带停止减弱。许多流变学的最终结果是温度限制在
The plate interface undergoes two transitions between seismogenic depths and subarc depths. A brittle-ductile transition at 20-50 km depth is followed by a transition to full viscous coupling to the overlying mantle wedge at similar to 80 km depth. We review evidence for both transitions, focusing on heat-flow and seismic-attenuation constraints on the deeper transition. The intervening ductile shear zone likely weakens considerably as temperature increases, such that its rheology exerts a stronger control on subduction-zone thermal structure than does frictional shear heating. We evaluate its role through analytic approximations and two-dimensional finite-element models for both idealized subduction geometries and those resembling real subduction zones. We show that a temperature-buffering process exists in the shear zone that results in temperatures being tightly controlled by the rheological strength of that shear zone's material for a wide range of shear-heating behaviors of the shallower brittle region. Higher temperatures result in weaker shear zones and hence less heat generation, so temperatures stop increasing and shear zones stop weakening. The net result for many rheologies are temperatures limited to