Crustal structure beneath the Archean–Proterozoic terrain of north India from receiver function modeling

Abstract

The shear velocity structure of the north Indian crust comprising of the Archean cratons (Aravalli–Bundelkhand) and Proterozoic Vindhyan basin is modeled and compared with the eastern Dharwar craton as well the global models for Archean and Proterozoic terrains. The velocity structure is deduced from joint inversion of teleseismic receiver function time series and surface wave group velocity measurements. The north Indian Archean crust is a simple two layered: an average Vs∼3.3±0.1km/s in the upper 10km increasing to 3.7±0.1km/s in the 26–28km thick lower crust. This upper crustal velocity is significantly less compared to those of either eastern Dharwar craton (3.5–3.6km/s) or the global average. These results suggest presence of a highly silica rich upper crust and an intermediate composition of the lower crust. The Moho is modeled at a depth of 36–38km with thin transition (∼2km) similar to those in eastern Dharwar craton. In contrast, the Proterozoic Vindhyan basin has significantly deeper Moho (44–46km) with a 4–10km thick underplated layer (Vs⩾4.0km/s) at the base of the crust. The sedimentary layer thickness is ∼2–4km. The results support the view that Proterozoic crust is thicker and underlain by a mafic layer at its base in contrast to a thin Archean crust with near absence of the basal layer as observed globally.