High electrical conductivity in a model lower crust with unconnected, conductive, seismically reflective layers
High electrical conductivity in a model lower crust with unconnected, conductive, seismically reflective layers
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DOI：
10.1111/j.1365-246x.1992.tb03478.x
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发表时间：
1992-03
影响因子：
2.8
通讯作者：
A. Merzer;S. Klemperer
中科院分区：
文献类型：
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作者：
A. Merzer;S. Klemperer
摘要在本文中，我们推导出一个模型下地壳的电导率包含不连接的，高导电性层状高阻矩阵。地震反射剖面成像的薄层（几百米厚，几公里宽）横向重叠，垂直间隔很小，可以增加下地壳的电导率，从对干燥岩石进行实验室测量预测的低值增加到实地实验观察到的高值。该模型不依赖于薄层内高电导率的原因。然而，下地壳的层积作用可能提供一种在不渗透、不导电的基质内的可渗透、导电层中岩性地捕获盐水的方法，从而解决了在地质时期内维持高孔隙压力所需的低地壳渗透率与所观察到的高导电性所需的高度孔隙互连之间的明显矛盾。渗透性薄层和非渗透性基质的岩性可能非常不同，这是由下地壳反射的高振幅所暗示的。对于一个典型的例子，该模型给出的双折射率与修改后的阿尔奇定律相比毫不逊色。该模型还可以给出各向异性电阻率效应，这是从现场实验结果定量兼容。
SUMMARY In this paper we derive the electrical conductivity for a model lower crust containing unconnected, highly conductive lamellae within a highly resistive matrix. Lateral overlap, with small vertical separation, of lamellae of the dimensions imaged by seismic reflection profiling (a few hundred metres thick and a few kilometres across) could increase lower-crustal conductivity from the low values predicted by laboratory measurements on dry rocks to the high values observed in field experiments. The model does not depend on the cause of high conductivity within the lamellae. However, lamellation of the lower crust may provide a way of lithologically trapping saline water in permeable, conductive lamellae within an impermeable, non-conductive matrix, and so resolve the apparent contradiction between the low crustal permeabilities required for maintenance of high pore pressure over geological time periods and the high degree of pore interconnection required for the high observed conductivity. The permeable lamellae and impermeable matrix would be of very different lithologies, as implied by the high amplitudes of the lower-crustal reflections. For a typical example the model gives resistivities that compare favourably with the modified Archie's Law. The model can also give anisotropic resistivity effects, which are quantitatively compatible with results from field experiments.