Characterization of the magma flow direction in the Nandurbar-Dhule Deccan dyke swarm inferred from magnetic fabric analysis

Abstract

The Deccan volcanic province (DVP; ~65 Ma old) of India is one of the classic examples of continental flood basalts. One of the most favoured hypotheses for DVP emplacement is “eruption through fissures” facilitated by major pre or syn-Deccan crustal extension. Determination of magma flow direction in its feeder dyke system provides clues on its possible association with a mantle plume, depth and number of the feeder chambers and other important geodynamic information on magma emplacement relevant in arguing about such hypotheses. In this paper, we have studied Dhule-Nandurbar Deccan (DND) dyke swarm (~210 mappable dykes) from Western India, that intruded compound basaltic (older than dykes) Deccan lava flows. Magnetic fabric which is commonly used as a proxy for magma flow fabric, was analysed in multiple oriented dyke samples using Anisotropy of Magnetic Susceptibility (AMS) technique. AMS analysis suggests that the studied dykes display dominantly subvertical to inclined flow and occasional sub-horizontal/lateral flow. The cumulative flow geometry further suggests the presence of multiple sub-surface magma centres (polycentric flow) from which magma pulses got injected through crustal fissures forming this magnificent dyke swarm that ultimately fed significant volume of the DVP.