Electrical conductivity imaging of the Philippine Sea upper mantle using seafloor magnetotelluric data
Electrical conductivity imaging of the Philippine Sea upper mantle using seafloor magnetotelluric data
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DOI：
10.1016/j.pepi.2010.09.010
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发表时间：
2010-11-01
影响因子：
2.3
通讯作者：
Tada, Noriko
中科院分区：
文献类型：
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作者：
Baba, Kiyoshi;Utada, Hisashi;Tada, Noriko
我们进行了为期三年的海底电磁调查，在菲律宾海，包括太平洋的西缘，图像的电特性的深地幔板停滞在过渡区和周围的地幔在三维（3-D）。该项目使用安装在18个地点的总共37个仪器，重复部署了一年的海底电磁仪。所获得的数据进行了分析，其恢复的顺序的基础上的大地电磁（MT）方法。在这项研究中，我们试图获得一个一维（1-D）的电导率模型下的菲律宾海和太平洋地区分别可以作为参考模型的第一步走向3-D分析。结果表明：（1）两地区上地幔浅层200 km处的电导率差异明显，这与岩石圈年龄的巨大差异是一致的; (2)在200-300 km深度，两个区域的电导率大致相同，约为0.3 S m（-1）。(3)菲律宾海地幔在400 km深度以下的电导率高于太平洋地幔。利用地幔矿物电导率的实验结果，可以从热结构、地幔水化作用和部分熔融的存在等方面解释电导率结构。如果将电导率简单地解释为温度的影响，菲律宾海下的地幔可能比地幔橄榄岩的干燥固相线更热，因此部分熔融。然而，在太平洋地区，目前的分析表明，部分熔融是不需要假设的橄榄岩组成下，即使我们考虑地幔水化。(C)2010 Elsevier B. V.保留所有权利。
We performed a three-year seafloor electromagnetic survey in the Philippine Sea, including the western edge of the Pacific Ocean, to image electrical features of a deep mantle slab stagnating in the transition zone and the surrounding mantle in three dimensions (3-D). The project iterated one-year deployment of ocean bottom electromagnetometers (OBEMs) using a total of 37 instruments installed at 18 sites. The data obtained have been analyzed in the order of their recovery based on a magnetotelluric (MT) method. In this study, we attempt to obtain a one-dimensional (1-D) electrical conductivity model beneath the Philippine Sea and the Pacific region separately that can be used as a reference model in the first step toward the 3-D analysis. The resultant 1-D models show three main features: (1) The conductivity in the shallower 200 km of the upper mantle depths of the two regions contrasts sharply, which is qualitatively consistent with the large difference in lithospheric age. (2) The conductivity at 200-300 km depth in both regions is more or less the same at approximately 0.3 S m(-1). (3) The conductivity just below 400 km depth is higher for the Philippine Sea mantle than for the Pacific mantle. The conductivity structure can be interpreted in terms of the thermal structure, mantle hydration, and existence of partial melt using experimental results for the conductivity of mantle minerals. If the conductivity is interpreted simply as the effect of temperature, the mantle beneath the Philippine Sea could be hotter than the dry solidus of mantle peridotite and thus partially molten. However, beneath the Pacific region, the present analysis suggests that the partial melting is not required under the assumed peridotitic composition even if we consider mantle hydration. (C) 2010 Elsevier B.V. All rights reserved.