The Physical Properties of Oceanic Basement Rocks From Deep Drilling on the
The Physical Properties of Oceanic Basement Rocks From Deep Drilling on the
复制标题
深钻大洋基底岩石的物理性质
DOI：
10.1029/jb081i023p04042
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发表时间：
1976
影响因子：
5.2
通讯作者：
R. Hyndman
中科院分区：
文献类型：
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作者：
R. Hyndman
在北纬37°N附近的大西洋中部海脊上钻取了大量玄武岩样品和少量辉长岩和蛇纹状橄榄岩，测量了岩石的纵横速度、电阻率、体积密度、颗粒密度、孔隙度和含水率以及热导率等物理性质，其中一个孔的样品深达582m，另一个孔的岩石可能代表下地壳。5.94kmS−-1玄武岩的平均挤压速度与以前的新鲜未风化海底玄武岩吻合得很好。然而，它可以与低得多的上地壳第二层地震折射速度相一致，通常只有在地壳中存在广泛的大规模破裂和空洞时才能观察到。辉长岩的实验室速度与上层第三层或海洋层的折射速度是一致的。较低的第三层折射速度与辉长岩和未蛇纹石化橄榄岩的混合成分一致。少量风化玄武岩的实验室样品的泊松比随速度的降低而系统地减小。玄武岩的平均电阻率在25°C时为220欧姆。电阻率与孔隙度密切相关，电阻率随压力适度增加，表明主要通过孔隙流体传导。玄武岩的电阻率随温度的升高而迅速下降，100℃时平均为20欧姆，150℃时约为5欧姆。玄武岩的平均体积密度为2.795 g cm−3，平均孔隙率为7.8%，21℃时的平均导热系数为3.97mcal cm−1 S−1°C−1。
The physical properties of compressional and shear velocity, electrical resistivity, bulk and grain density, porosity and water content, and thermal conductivity have been measured on a large collection of basalt samples and a few gabbros and serpentinized peridotites recovered by drilling on the mid-Atlantic ridge near 37°N. Samples were recovered to 582 m into basaltic basement in one hole, and rocks that may be representative of the lower crust were recovered from another hole. The mean compressional velocity of the basalts of 5.94 km s−1 agrees well with previous fresh unweathered sea floor basalts. It, however, can be reconciled with the much lower average upper crustal layer 2 seismic refraction velocities generally observed only by the presence of extensive large-scale fracturing and voids in the crust. The laboratory velocities of the gabbros are consistent with upper layer 3, or oceanic layer, refraction velocities. Lower layer 3 refraction velocities are consistent with a composition of a mix of gabbro and unserpentinized peridotite. Poisson's ratio for little-weathered laboratory samples of basalt is found to decrease systematically with decreasing velocity. The mean electrical resistivity of the basalts is 220 ohm m at 25°C. A close dependence of resistivity on porosity and a moderate increase in resistivity with pressure suggest conduction primarily through pore fluid. The basalt resistivity decreases rapidly with increasing temperature, the mean becoming about 20 ohm m at 100°C and about 5 ohm m at 150°C. The mean basalt bulk density is 2.795 g cm−3, the mean porosity is 7.8%, and the mean thermal conductivity at 21°C is 3.97 mcal cm−1 s−1 °C−1.