The Abundance of Serpentinites in the Oceanic Crust
The Abundance of Serpentinites in the Oceanic Crust
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DOI：
10.1086/627796
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发表时间：
1972-11
期刊：
影响因子：
--
通讯作者：
N. Christensen
中科院分区：
文献类型：
--
作者：
N. Christensen
本文报道了在北纬43°，北纬1°，S 4°的大西洋中脊蛇纹岩中纵波和横波速度在10kbar压力下的新测量结果。在洋壳压力下，蛇纹岩中纵波速度(Vp)在4.2~5.2公里/秒之间，横波速度(S)在2.1~2.5公里/秒之间。蛇纹岩的V_(P)与V_(8)之比远高于洋壳中其他岩石的测量结果。蛇纹岩的泊松比在0.34到0.38之间变化。蛇纹岩和部分蛇纹岩橄榄岩的速度和泊松比与地震折射研究确定的类似数据的对比表明，蛇纹岩不是洋壳的主要成分。因此，大洋蛇纹岩被解释为在断裂带中通过构造作用侵位到断裂带的橄榄岩的水化作用而形成的。洋壳主要由镁铁质火成岩及其变质对应物组成，与实验室测得的弹性性质与地震折射数据的对比更符合。
New measurements of compressional- and shear-wave velocities in serpentinites from the Mid-Atlantic Ridge at 43° N, 1° N, and 4° S are reported at pressures to 10 kbar. At oceanic crustal pressures, compressional-wave velocities ($$V_{p}$$) in serpentinites are between 4.2 and 5.2 km/sec and shear-wave velocities ($$V_{s}$$) range from 2.1 to 2.5 km/sec. The ratios of $$V_{p} to V_{8}$$ for serpentinites are much higher than those measured for other rocks believed to be abundant in the oceanic crust. Poisson's ratios of serpentinites vary between 0.34 and 0.38. Comparisons of velocities and Poisson's ratios of serpentinites and partially serpentinized peridotites with similar data determined by seismic refraction studies demonstrate that serpentine is not a major constituent of the oceanic crust. Consequently, oceanic serpentinites are interpreted as forming in fracture zones by the hydration of peridotites which have been emplaced into the fracture zones by tectonic processes. An oceanic crust composed primarily of mafic igneous rocks and their metamorphosed equivalents is in better agreement with comparisons of laboratory measured elastic properties with seismic refraction data.