Intensity of Magnetization of Subaerial and Submarine Basalts and its Possible Change with Time
Intensity of Magnetization of Subaerial and Submarine Basalts and its Possible Change with Time
复制标题
陆上和海底玄武岩的磁化强度及其随时间可能的变化
DOI：
10.1111/j.1365-246x.1975.tb07047.x
复制
发表时间：
1975
影响因子：
2.8
通讯作者：
S. Gromme
中科院分区：
文献类型：
--
作者：
M. Prévôt;S. Gromme
总结
对从历史时间到 10 My 的 177 个陆上玄武岩流和来自北大西洋基底的 204 个海底玄武岩样本编制的自然剩磁强度表明，陆上玄武岩的平均强度（减少到赤道当量值）为 36 × 10−4 emu cm−3，比海底玄武岩（89.6 × emu）弱约 2.5 倍。厘米−3）。由于粘性成分占稳定剩磁的约五分之一，正常磁化流的 NRM 明显高于反向流。 Brunhes 玄武岩和较古老的正常玄武岩之间的平均强度，或者历史玄武岩部分退磁后的强度与 0-01 至 1、1 至 2、2 至 3 或 3 至 4 My 范围内的玄武岩的强度之间没有显着差异。这似乎表明（i）地面玄武岩的磁化强度在数百万年的时间内没有发生明显的下降，（ii）布伦赫斯时期地磁场强度的可能增加并不是造成大洋中脊轴向磁异常幅度更大的原因。
对于海洋基底，从中谷底部的玄武岩到山脊顶部和侧翼的玄武岩，平均强度降低了约三分之二。这种减少可能是由钛磁铁矿的强烈低温氧化造成的，与远离洋脊轴时在北大西洋观察到的磁异常的减少相当。
Summary
Intensities of natural remanent magnetization compiled for 177 subaerial basaltic flows ranging from historical time to 10 My and for 204 submarine basalt samples from the North Atlantic basement show that subaerial basalts have a mean intensity, reduced to an equatorial equivalent value, of 36 × 10−4 emu cm−3, about 2.5 times weaker than for submarine basalts (89.6 × emu cm−3). Normally magnetized flows have significantly greater NRM than reversed flows owing to a viscous component that represents about one-fifth of the stable remanence. No significant difference appears in the mean intensity between the Brunhes basalts and the older normal basalts or between the intensity, after partial demagnetization, of historic basalts and those ranging from 0–01 to 1, 1 to 2, 2 to 3, or 3 to 4 My. This seems to indicate (i) that no important decrease of the intensity of magnetization of subaerial basalts takes place for periods of several million years, and (ii) that a possible increase of the intensity of the geomagnetic field during the Brunhes epoch is not responsible for the larger amplitude of the axial magnetic anomaly over mid-ocean ridges.
For the oceanic basement, the mean intensity decreases by about two-thirds from the basalts of the bottom of the median valley to the basalts from the crests and flanks of the ridge. This diminution, probably produced by intensive low-temperature oxidation of titanomagnetite, is comparable to the decrease of the magnetic anomalies observed in the North Atlantic when going away from the ridge axis.