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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Variations in the electrical conductivity of the upper mantle beneath North America and the Pacific Ocean
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Variations in the electrical conductivity of the upper mantle beneath North America and the Pacific Ocean

机译：北美和太平洋下方上地幔的电导率变化

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Variations in the electrical conductivity of the mantle beneath Carty Lake in the Canadian Shield, Tucson in the southwest United States, and Honolulu and Midway in the north central Pacific were determined through the inversion of long-period magnetotelluric and geomagnetic depth sounding data. Inversion of computed response functions is carried out using a minimum structure, regularized approach. The upper mantle beneath Carty Lake is approximately an order of magnitude more resistive than the upper mantle beneath Tucson and nearly 1.5 orders of magnitude more resistive than Honolulu and Midway Island. Inversions were also carried out where the minimum structure constraint was removed at known upper mantle discontinuities. These models show a jump in conductivity of similar to 1.5 orders of magnitude across the 660 km discontinuity, a result that is consistent with laboratory experiments on realistic mantle assemblages. Mantle conductivity profiles at Carty Lake are significantly more resistive than those at Tucson, Honolulu, and Midway to depths of similar to 300-400 km. These observations likely reflect differing thermal states, the presence (or absence) of partial melt and volatiles, and may also be related to chemical differences between depleted and undepleted upper mantle. The observed conductivity variations may be interpreted as lateral variations in temperature, partial melt, and/or dissolved hydrogen in olivine. [References: 56]
机译：通过对长期大地电磁和地磁深度探测数据进行反演，确定了加拿大盾构中的卡蒂湖下方的地幔电导率，美国西南部的图森以及中北部太平洋中部的檀香山和中途的电导率变化。计算的响应函数的求逆使用最小结构的正则化方法进行。卡蒂湖下面的上地幔的电阻比图森下面的上地幔的电阻高大约一个数量级，比檀香山和中途岛的电阻高近1.5个数量级。在已知的上地幔不连续面去除最小结构约束的地方也进行了反演。这些模型显示，在660 km的不连续面中，电导率的跃迁接近1.5个数量级，这一结果与实际的地幔组合的实验室实验一致。卡蒂湖的地幔电导率曲线比图森，火奴鲁鲁和中途的地幔电导率曲线具有更大的电阻，深度约为300-400 km。这些观察结果可能反映了不同的热状态，部分熔融物和挥发物的存在（或不存在），并且还可能与贫化和未贫化的上地幔之间的化学差异有关。所观察到的电导率变化可以解释为温度，部分熔体和/或橄榄石中溶解的氢的横向变化。 [参考：56]

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