Paleo‐Stress Regimes and Emplacement Dynamics of a Regional Fault‐Bounded Dyke System in Continental Flood Basalt Province: Insights From the Narmada‐Tapi Swarm, Deccan Volcanic Province, India

ABSTRACT Narmada‐Tapi dyke swarm is one of the two principal swarms within the Deccan Volcanic Province of India. This study presents new data on the field characters, geometry, and structure of mafic dykes of this giant swarm, housed in a mid‐continental fault zone of Precambrian heritage mimicking horst‐graben structure. We map 443 lineaments as dykes in an area of 7000 km 2 and validate 193 on ground. The braided map pattern in the swarm's densest parts indicates higher rates of fracture propagation and magma flow (movement) duly manifested by occasional incorporation of basement xenoliths and local contact‐melting of host basalt lava flows. During dyke emplacement, the principal stress axes made a prolate ellipsoid ( σ 1 >> σ 2 > σ 3) and the 3D Mohr's stress circles related the magma pressure (P m ) to the paleo‐stress regime as σ 2 > P m > σ 3. The swarm induced ~5% crustal extension. We estimate magma overpressure that drove the dyke‐melt upwards and laterally through the fractured granitic basement from ~10 to 12 km deep magma chamber, assisted by hydro‐fracturing of older basaltic flows at shallow levels. We also review the significance of the regional fault‐bounded dyke swarms in the emplacement of Deccan flood basalts.