Dyke emplacement in the Narmada rift zone and implications for the evolution of the Deccan Traps
Wei Ju, Guiting Hou, K. R. Hari, 2017. "Dyke emplacement in the Narmada rift zone and implications for the evolution of the Deccan Traps", Tectonics of the Deccan Large Igneous Province, S. Mukherjee, A. A. Misra, G. Calvès, M. Nemčok
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The 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.
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Tectonics of the Deccan Large Igneous Province
Understanding the Deccan Trap Large Igneous Province in western India is important for deciphering the India–Seychelles rifting mechanism. This book presents 13 studies that address the development of this province from diverse perspectives including field structural geology, geochemistry, analytical modelling, geomorphology and geophysics (e.g., palaeomagnetism, gravity and magnetic anomalies, and seismic imaging). Together, these papers indicate that the tectonics of Deccan is much more complicated than previously thought. Key findings include: the Deccan province can be divided into several blocks; the existence of a rift-induced palaeo-slope; constraints on the eruption period; rift–drift transition mechanisms determined for magma-rich systems; the tectonic role of the Deccan or Réunion plumes; sub-surface structures reported from boreholes; the delineation of the crust–mantle structure; the documentation of sub-surface tectonic boundaries; post-Deccan-Trap basin inversion; deformed dykes around Mumbai, and also from the eastern part of the Deccan Traps, documented in the field.