Shear-velocity structure of the Tyrrhenian Sea: Tectonics, volcanism and mantle (de)hydration of a back-arc basin
Shear-velocity structure of the Tyrrhenian Sea: Tectonics, volcanism and mantle (de)hydration of a back-arc basin
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第勒尼安海的剪切速度结构：弧后盆地的构造、火山活动和地幔（脱水）作用
DOI：
10.1016/j.epsl.2014.05.028
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发表时间：
2014
影响因子：
5.3
通讯作者：
Greve S
中科院分区：
文献类型：
--
作者：
Greve S
地中海的第勒尼安海是亚得里亚海和爱奥尼亚俯冲板块回滚的结果。它的下部大多是非常薄的大陆岩石圈，但在第勒尼安南部包含两个小的海洋盆地，最年轻的一个位于活跃的岩浆弧后面。该地区的台站覆盖密集，为利用台站间瑞利波频散测量得出弧后盆地及周边陆上区域的高分辨率三维剪切速度模型提供了独特的机会。我们的层析模型，延伸到大约160公里的深度，显示了一个明显的，近环状的低剪切速度带，在70和110公里的深度之间，它包围着古老的海洋Vavilov盆地。70 km深度处的速度急剧下降可以用相对干燥的岩石圈地幔向含水较多的软流圈地幔物质过渡来解释。该地区的构造演化及低速异常与俯冲相关火山活动的对比表明，低速异常反映了（现在或以前）地幔楔带的含水地幔物质。我们认为，瓦维洛夫盆地下没有低速带是由于MORB地壳形成引起的地幔脱水所致。虽然温度效应可能主导了各弧后盆地间软流圈剪切速度差异，但我们发现第勒尼安地区剪切速度结构的变化最好用地幔含水量的变化来解释。
The Tyrrhenian Sea in the Mediterranean formed as the result of roll-back of the Adriatic and Ionian subducting plates. It is mostly underlain by strongly thinned continental lithosphere, but contains two small oceanic basins in the southern Tyrrhenian, the youngest one located just behind the active magmatic arc. Its regional setting with dense station coverage provides a unique opportunity to derive a high-resolution, 3-D shear-velocity model of this back-arc basin and surrounding onshore areas using interstation Rayleigh-wave dispersion measurements. Our tomographic model, extending to a depth of approximately 160 km, displays a pronounced, nearly ring-shaped low shear-velocity zone between 70 and 110 km depth which surrounds the older oceanic Vavilov Basin. The sharp velocity decrease at 70 km depth can be explained by the transition from a relatively dry lithospheric mantle to more hydrous asthenospheric mantle material. The tectonic evolution of the region and the correlation of the low-velocity anomaly with subduction-related volcanism indicate that the low-velocity anomaly reflects hydrous mantle material in (present or former) mantle wedge regions. We suggest that the absence of the low-velocity zone beneath the Vavilov Basin is due to mantle dehydration caused by the creation of MORB crust. Whereas temperature effects may dominate the asthenospheric shear-velocity differences between various back-arc basins, we find that the variations in shear-velocity structure within the Tyrrhenian area are best explained by variations in mantle water content.
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