Dyke emplacement in the Narmada rift zone and implications for the evolution of the Deccan Traps

Abstract

AbstractThe Deccan Large Igneous Province of India is the product of fissure eruptions, and contains vast lava fields and dyke–sill networks. It is associated with several rift zones in peninsular India, which reflect pre-existing major weaknesses in the Indian lithosphere. In rift-zone eruptions, magma is normally transported to the surface through dykes. However, some injected dykes do not reach the surface but are arrested at depth in the rift zone due to mechanical heterogeneity and anisotropy, or insufficient magma pressure. In the present work, the effects of mechanical layering and regional tension on dyke emplacement in the Narmada rift zone are studied. The results indicate that the distribution of maximum principal tensile stresses was altered by mechanical layering and/or regional tension, which has led to variations in potential dyke propagation pathways. Studies on dyke evolution and emplacement in the Narmada rift zone indicate four evolutionary stages: stage I – arrival of a mantle plume and pre-volcanic extension; stage II – formation of shallow magma chambers; stage III – vertical dyke injection and fissure eruption; and stage IV – the ‘blanket effect’ and lateral dyke propagation.