3D radial anisotropic imaging of magma plumbing systems beneath the Malani silicic igneous province in northwestern India

Abstract Imaging the plumbing systems of ancient silicic large igneous provinces (SLIPs) is inherently challenging due to the decay of thermal anomalies associated with SLIPs, and the erosion or masking of surface expressions by sediments. The plumbing architecture of the Neoproterozoic Malani SLIP, remains unresolved, due to limited geophysical evidence of magma conduits or sill complexes. We present the first 3D crustal isotropic shear velocity and radially anisotropic models obtained through ambient noise tomography beneath northwestern India. The model reveals distinct zones of positive and negative radial anisotropy in the mid- to lower crust. Positive anisotropy, reaching up to + 8%, is interpreted as the signature of horizontally aligned mafic sills, while negative anisotropy, down to − 8%, indicates vertical, dyke-like structures. The lower crust beneath the Siwana caldera and the Barmer rift exhibits strong positive anisotropy, suggesting lateral magma transport and the development of sill complexes. In contrast, vertically oriented cylindrical zones of negative anisotropy correlate with exposures of Malani volcanics and Deccan-related alkaline complexes, suggesting rejuvenation of magma conduits. Our results suggest that mantle-derived lower crustal mafic sill complexes led to crustal melting and formation of horizontally layered silicic reservoirs in the shallow crust which erupted to form the Malani SLIP.