Mantle wedge temperatures and their potential relation to volcanic arc location
Mantle wedge temperatures and their potential relation to volcanic arc location
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DOI：
10.1016/j.epsl.2018.08.011
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发表时间：
2018-11
影响因子：
5.3
通讯作者：
A. Perrin;S. Goes;J. Prytulak;S. Rondenay;D. Davies
中科院分区：
文献类型：
--
作者：
A. Perrin;S. Goes;J. Prytulak;S. Rondenay;D. Davies
在俯冲带上方形成聚焦火山弧的机制存在争议。建议包括：（i）俯冲板块释放水，降低上覆地幔楔中的固相线;（ii）地幔楔熔融程度最高的位置;（iii）楔的冷浅角对熔体形成和迁移的限制。在这里，我们评估这三个建议的机制，使用一组运动驱动的二维热机械地幔楔模型，其中俯冲速度，板倾角和年龄，覆盖板厚度和深度的两个板块之间的去耦系统地变化。所有机制预测，模型几何形状的基础上，弧沟距离，D，强烈下降，倾角增加，与negativeD-倾角相关性在全球俯冲数据。如果楔形温度控制且上覆板厚不超过去耦深度50 km以上，则弧下板厚H随倾角的模型趋势为正，如果楔形温度控制，则为负。观察到的全球H值下降趋势总体上是积极的。随着覆盖板块厚度的增加，最大熔融的位置转移到smallerHandD，而熔融区的沟向极限的位置，由楔的冷角控制，转移到largerHandD，类似于海洋俯冲带的数据趋势。因此，由楔角对熔化和熔体迁移施加的限制似乎对电弧位置施加一阶控制。
The mechanisms underpinning the formation of a focused volcanic arc above subduction zones are debated. Suggestions include controls by: (i) where the subducting plate releases water, lowering the solidus in the overlying mantle wedge; (ii) the location where the mantle wedge melts to the highest degree; and (iii) a limit on melt formation and migration imposed by the cool shallow corner of the wedge. Here, we evaluate these three proposed mechanisms using a set of kinematically-driven 2D thermo-mechanical mantle-wedge models in which subduction velocity, slab dip and age, overriding-plate thickness and the depth of decoupling between the two plates are systematically varied. All mechanisms predict, on the basis of model geometry, that the arc-trench distance,D, decreases strongly with increasing dip, consistent with the negativeD-dip correlations found in global subduction data. Model trends of sub-arc slab depth,H, with dip are positive ifHis wedge-temperature controlled and overriding-plate thickness does not exceed the decoupling depth by more than 50 km, and negative ifHis slab-temperature controlled. Observed globalH-dip trends are overall positive. With increasing overriding plate thickness, the position of maximum melting shifts to smallerHandD, while the position of the trenchward limit of the melt zone, controlled by the wedge's cold corner, shifts to largerHandD, similar to the trend in the data for oceanic subduction zones. Thus, the limit imposed by the wedge corner on melting and melt migration seems to exert the first-order control on arc position.