Preliminary anisotropy of magnetic susceptibility studies on 2367 Ma Bangalore-Karimnagar giant dyke swarm, southern India: Implications for magma flow
Anisotropy of magnetic susceptibility (AMS) fabrics have been studied for the first time on a well constrained Paleoproterozoic Bangalore-Karimnagar giant mafic dyke swarm (43 samples from nine sites) at ca. 2367 Ma in the Dharwar craton, south India. Hysteresis loops, Isothermal remanent magnetisation (IRM), thermomagnetic properties and optical observations indicate that pseudo single domain (PSD) low-titanium magnetite particles dominate the low field susceptibility of samples. The principal AMS axes for samples from all the sites are tightly clustered on equal area plots, and two main fabrics were revealed in the Bangalore-Karimnagar giant dyke swarm. In the first, the maximum susceptibility axes is sub-horizontal and parallel to the dyke walls, minimum susceptibility axes plot near the pole of the dyke. It is interpreted as the primary magma flow direction. A second fabric with maximum susceptibility axis is sub-horizontal and perpendicular to the dyke walls, and is interpreted as a result of vertical compaction at a late stage of crystallization. Preliminary results suggest that dyke propagation in the Bangalore-Karimnagar giant dyke swarm preserve a flow-induced fabric slightly upwards to the NE and magma flow is sub-horizontal.
Figure Caption: Lower hemisphere projection of eigenvectors K1 (blue square), K2 (green triangle) and K3 (purple circle) from representative sites of Bangalore-Karimnagar giant dyke swarm. Dyke trends are shown as grey lines. Red line indicates the foliation trend.
Babu N. Ramesh, Nagaraju E., Parashuramulu V., Venkateshwarlu M.; 2020, Preliminary anisotropy of magnetic susceptibility studies on 2367 Ma Bangalore-Karimnagar giant dyke swarm, southern India: Implications for magma flow . Physics of the Earth and Planetary Interiors , Volume 306 , September 2020, 106540