Research Note : Structural analysis of dyke emplacement directions as an aid to palaeomagnetic studies: an example from northern Chile
Research Note : Structural analysis of dyke emplacement directions as an aid to palaeomagnetic studies: an example from northern Chile
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研究笔记：堤坝安放方向的结构分析作为古地磁研究的辅助：智利北部的一个例子
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发表时间：
2000
期刊：
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通讯作者：
E. Randall
中科院分区：
文献类型：
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作者：
K. Taylor;E. Randall
侵入岩古地磁研究的一个主要问题是确定这些岩石是否遭受过侵位后倾斜。对岩脉侵位方向进行结构分析，可以反映岩脉群延伸方向的当前走向。如果能从地质证据中推断出炮位就位时的原始延伸方向，那么这就为炮位就位后堤群及其宿主岩的倾斜提供了现场试验。在智利北部给出的例子中，我们能够对侵入同样年轻的岩体的三个连续较年轻的岩脉群进行古地磁研究和结构分析。三个堤群的延伸方向均接近水平，但方位角差异明显。认为伸展方向上的倾突相似性不可能是巧合，岩脉及其主岩并没有在侵位后发生明显的倾斜。这种简单的方法可广泛应用于古地磁研究中岩脉就位后倾斜度的评价。
SUMMARY A major problem in palaeomagnetic studies of intrusive rocks lies in determining whether or not such rocks have been subjected to post-emplacement tilting. Structural analysis of dyke emplacement directions can be used to show the current attitude of the extension direction for the dyke swarm. If the original extension direction, at the time of emplacement, can be deduced from geological evidence, this then provides a field test for post-emplacement tilting of the dyke swarm and its host rocks. In the example given from northern Chile, we were able to make a palaeomagnetic study of and structurally analyse three successively younger dyke swarms that intrude similarly younging plutons. All three dyke swarms yielded extension directions close to horizontal but with markedly diVerent azimuths. It is argued that the similarity in the plunge of the extension directions cannot be coincidental and that the dykes and their host plutons have not suVered significant post-emplacement tilting. This simple technique should be widely applicable in the assessment of post-emplacement tilting of dykes in palaeomagnetic studies.