Mantle wedge hydration in Nicaragua from local earthquake tomography
Mantle wedge hydration in Nicaragua from local earthquake tomography
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DOI：
10.1111/j.1365-246x.2011.05041.x
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发表时间：
2011-07-01
影响因子：
2.8
通讯作者：
Taylor, Waldo
中科院分区：
文献类型：
--
作者：
Dinc, A. Nilay;Rabbel, Wolfgang;Taylor, Waldo
尼加拉瓜和哥斯达黎加大陆边缘具有显著的自北向南的横向变化特征，如板块倾角减小、岩浆产量减少和火山锋移动。为了研究这种转变，进行了陆上和海上局部地震断层扫描。桑迪诺盆地上地幔和下地壳具有低纵波速度和高V-p/V-s比的水化特征。据估计，南尼加拉瓜地下的地幔楔水化作用占2.5%。相比之下，哥斯达黎加北部的地幔楔是弱水合或不水合的。水化作用导致尼加拉瓜地震活动性出现局部间隙。水合区和非水合区之间的横向过渡发生在大约10公里的距离内。这种转变与地壳厚度的变化相一致，在5-10公里的范围内，向南加厚，并且在构造制度中。沿尼加拉瓜边缘向更强的伸展方向的构造体制的变化可能是理解观测结果的关键：伸展可能支持通过上覆板块的广泛流体迁移和水化通道的打开，这些通道被识别为低V-p、高V-p/V-s和低地震活动性区域。
The continental margin of Nicaragua and Costa Rica is characterized by significant lateral changes from north to south such as a decreasing dip of the slab, a decreasing magma production and a shift in the volcanic front. To investigate this transition, a joint on-and offshore local earthquake tomography was performed. Low P-wave velocities and high V-p/V-s ratios, indicative for hydration, were found in the upper-mantle and lowermost crust beneath the Sandino Basin. The mantle wedge hydration can be estimated to 2.5 wt. per cent beneath south Nicaragua. In contrast, the mantle wedge beneath north Costa Rica is weakly or not hydrated. The hydration leads to a local gap in the seismicity in Nicaragua. The lateral transition between the hydrated and non-hydrated areas occurs within a distance of about 10 km. This transition coincides with a change in the crustal thickness in the order of 5-10 km, thickening to the south, and in the tectonic regimes. The change in the tectonic regimes towards a stronger extension along the margin of Nicaragua could be the key for understanding the observations: the extension may support the opening of pathways for a wide zone of fluid migration and hydration through the overriding plate which are identified with areas of low V-p, high V-p/V-s and low seismicity.