Mechanics of mafic dyke swarms in the Deccan Large Igneous Province: Palaeostress field modelling

A numerical model – “rifts – plume or hot spot – drift model” – is proposed for the first time in this paper for the generation of the three regional-scale dyke swarms (the Narmada–Tapi dyke swarm, the Nasik–Pune dyke swarm and the West Coast dyke swarm) within the Deccan Large Igneous Province (LIP) on the basis of the geological evolution of Deccan LIP and the orientations of dyke swarms. The dyke swarms have been modelled with finite element method (FEM) in three stages (stages I–III) considering that there was about 20° counterclockwise rotation of the Indian subcontinent since 65 Ma. During stage I, the orientation of the horizontal maximum principal compressive stress (σ1) is ∼ENE–WSW, generating the ENE–WSW-trending Narmada–Tapi dyke swarm. In stage II, the σ1 orientations are weakly preferred in NW–SE and E–W which are in agreement with the orientations of Nasik–Pune dyke swarm. In stage III, the σ1 orientation is ∼N–S generating the nearly N–S-trending West Coast dyke swarm. The rifts, plume or hot spot and the northward counterclockwise motion of Indian subcontinent altogether contributed to the generation of Deccan LIP and its associated dyke swarms.

► The rifts, plume and rotational movement contribute for Deccan LIP and dyke swarms. ► The preexisting fracture systems are tensile, without shearing. ► There is an order among the three mafic dyke systems traversing Deccan LIP. ► The maximum principal compressional stress controls the dyke swarms’ orientation.