Intracratonic stability: A comparison of paleomagnetic data from the north and the south of Dharwar Craton, India
Intracratonic stability: A comparison of paleomagnetic data from the north and the south of Dharwar Craton, India
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DOI：
10.1016/j.precamres.2020.105858
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发表时间：
2020-07
影响因子：
3.8
通讯作者：
A. Pivarunas;J. Meert
中科院分区：
文献类型：
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作者：
A. Pivarunas;J. Meert
印度达尔瓦尔克拉通的显著弯曲最近被认为是通过约30°的逆时针垂直轴克拉通内旋转来确定克拉通“稳定”阶段的时间。初步facieevidence为这一旋转是重新调整后的堤坝趋势推断变形校正。这一提议似乎也与在宿主太古代基底中观察到的结构颗粒相一致。我们认为，使用的趋势岩墙群是不是理想的方法来评估克拉通内旋转，而是我们使用的变化，古地磁确定decompensation数据从这些堤坝。我们发现，多个早期古元古代岩墙群（2367年，2216年和2082年马代）保留了一个系统的偏移有很大的不确定性。平均古地磁允许反时针旋转为19° ± 17°。在~1888 Ma LIP期间就位的堤坝没有显示出相同的偏移，这表明在此之前发生了旋转。因此，2082-1888 Ma的时间段是发生任何变形和构造作用的窗口，这些变形和构造作用使达尔瓦尔克拉通弯曲约20°。没有大规模的变形事件记录在Dharwar克拉通在这个关键的间隔除了最早阶段的Cuddapah盆地形成。我们认为，“观察到的”旋转结果与如何的趋势的堤坝和他们的磁方向编译时，年龄数据是有限的偏见。达尔瓦尔克拉通地质特征的弯曲可能是新太古代西达尔瓦尔克拉通和东达尔瓦尔克拉通碰撞的构造继承。
The prominent bend of Dharwar craton, India was recently suggested to post-date the ‘stabilization’ phase of the craton via a ~30°, anticlockwise, vertical-axis intracratonic rotation. Theprima facieevidence for this rotation was the realignment of dyke trends following correction of the inferred deformation. The proposal also appeared to be consistent with the observed structural grain in the host Archean basement. We argue that using the trend of dyke swarms is not the ideal method to assess intracratonic rotation and instead we use variations in paleomagnetically determined declination data from these dykes. We find that multiple early Paleoproterozoic dyke swarms (the 2367, 2216, and 2082 Ma generations) preserve a systematic offset with a large uncertainty. The mean paleomagnetically permissible anticlockwise rotation is 19° ± 17°. Dykes emplaced during the ~1888 Ma LIP do not show the same offset, which suggests that rotation occurred prior to this time. Therefore, the 2082-1888 Ma interval brackets the window for any deformation and tectonism required to bend the Dharwar craton by about ~20°. No large-scale deformational events are documented in the Dharwar craton during this critical interval apart from the earliest stages of Cuddapah basin formation. We argue that the ‘observed’ rotation results from biases associated with how trends of dykes and their magnetic directions are compiled when age data are limited. The curvature of geological features in Dharwar craton is likely the tectonic inheritance of the Neoarchean collision between the Western Dharwar and Eastern Dharwar cratons.