Experimental quantification of permeability of partially molten mantle rock
Experimental quantification of permeability of partially molten mantle rock
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DOI：
10.1016/j.epsl.2013.12.003
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发表时间：
2014-02-15
影响因子：
5.3
通讯作者：
Gaetani, Glenn A.
中科院分区：
文献类型：
--
作者：
Miller, Kevin J.;Zhu, Wen-lu;Gaetani, Glenn A.
目前，地幔岩石中的熔体渗流受到的约束很差，特别是在低熔体分数下。例如，在大洋中脊，地球化学和地球物理观测对地幔中存在的熔化量及其移动速度产生了不同的估计。为了协调这些观测结果，必须准确估计地幔岩石中的渗透率和颗粒尺度熔体分布。我们展示了橄榄石-玄武岩聚集体的三维 (3-D)、700 nm 分辨率图像，其中标称熔体分数 (phi(n)) 介于 0.02 和 0.20 之间。样品由圣卡洛斯橄榄石和高铝玄武岩的粉末混合物制备，并在固体介质活塞缸装置中在 1350 摄氏度和 1.5 GPa 下热压。图像是使用阿贡国家实验室先进光子源的同步加速器 X 射线显微断层扫描 (SX mu T) 获得的。使用数字熔体体积作为数值域进行斯托克斯流模拟，确定当 phi(n) = 0.02 至 0.20 时，实验电荷的渗透率范围分别为 2 x 10(-16) 至 5 x 10(-13) m(2)。模拟结果很好地体现了渗透率 (k) 和熔体分数 (phi) 之间的幂律关系，k = phi(n)d(2)/C，其中 n = 2.6 +/- 0.2，并假设实验中的晶粒尺寸为 35 pm，C = 58(-22)(+36)。这些结果对地幔部分熔融区域内的熔体迁移和熔体提取速率提出了重要的新限制。 (C) 2013 Elsevier B.V. 保留所有权利。
Melt percolation in mantle rocks is currently poorly constrained, especially at low melt fractions. At mid-ocean ridges, for example, geochemical and geophysical observations produce divergent estimates of how much melt is present in the mantle and how quickly it moves. Accurate estimates of permeability and grain-scale melt distribution in mantle rock are necessary to reconcile these observations. We present three-dimensional (3-D), 700 nm-resolution images of olivine-basalt aggregates, containing nominal melt fractions (phi(n)) between 0.02 and 0.20. Samples were prepared from a powdered mixture of San Carlos olivine and high-alumina basalt and hot-pressed in a solid-medium piston-cylinder apparatus at 1350 degrees C and 1.5 GPa. Images were obtained using synchrotron X-ray microtomography (SX mu T) from the Advance Photon Source at Argonne National Laboratory. Stokes flow simulations, conducted using the digital melt volume as the numerical domain, determine that the permeabilities of experimental charges range from 2 x 10(-16) to 5 x 10(-13) m(2) for phi(n) = 0.02 to 0.20, respectively. The simulation results are well represented by the power-law relation between permeability (k) and melt fraction (phi), k = phi(n)d(2)/C, where n = 2.6 +/- 0.2, and assuming a grain size of 35 pm in the experiments, C = 58(-22)(+36). These results place important new constraints on rates of melt migration and melt extraction within partially molten regions of the mantle. (C) 2013 Elsevier B.V. All rights reserved.