Thermoviscous remanent magnetism of Columbia River basalt blocks in the cascade landslide
Thermoviscous remanent magnetism of Columbia River basalt blocks in the cascade landslide
复制标题
梯级滑坡中哥伦比亚河玄武岩块的热粘剩磁
DOI：
10.1029/94gl02669
复制
发表时间：
1994
影响因子：
5.2
通讯作者：
K. Verosub
中科院分区：
文献类型：
--
作者：
Rebecca Smith;K. Verosub
我们研究了哥伦比亚河峡谷滑坡中的16个玄武岩样品，以确定它们是否自大约800年前滑坡就位以来获得了热粘性反磁性（TVRM）。所有样品在20个加热步骤下热退磁直到360°C，其中注意到磁化率的大变化。退磁过程中的方向变化的分析表明，样品包含多达四个TVRM组件，除了NRM组件。具有最低阻塞温度的TVRM分量紧密地聚集在当前场方向周围，而NRM方向与随机分布一致，正如预期的滑坡存款。样品的磁滞参数测量和热磁分析表明，玄武岩中的主要磁性矿物为单畴磁铁矿。除去第一TVRM组分的温度范围为70°C至100°C。该结果可以与将用于使TVRM去磁的时间和温度与获取TVRM的时间和温度相关联的列线图进行比较。与Middleton &施密特（1982）的列线图相比，我们的结果与Pullaiah等（1975）的列线图更为一致。
We studied sixteen basalt samples from a landslide in the Columbia River Gorge to determine if they had acquired a thermoviscous remanent magnetism (TVRM) since the slide was emplaced about 800 years ago. All samples were thermally demagnetized at 20 heating steps until 360°C, where a large change in susceptibilit y was noted. Analysis of the directional changes during demagnetization indicates that the samples contain up to four TVRM components, in addition to an NRM component. The TVRM components with the lowest blocking temperatures are tightly clustered around the present field direction while the NRM directions are consistent with a random distribution, as expected for a landslide deposit. Measurements of hysteresis parameters and thermomagnetic analyses of the samples demonstrate that the dominant magnetic mineral in the basalt is single- domain magnetite. The temperature at which the first TVRM component was removed ranges from 70°C to 100°C. This result can be compared to nomographs that relate the time and temperature used to demagnetize a TVRM with the time and temperature at which the TVRM was acquired. Our results are more consistent with the nomograph of Pullaiah et al. (1975) than with the nomograph of Middleton & Schmidt (1982).