Teleseismic receiver functions modeling of the eastern Indian craton

Abstract

We estimate receiver functions (RFs) through the time-domain deconvolution using three-component broadband data of 100 teleseismic events (30°⩽∧⩽90°) from 15 seismographs in the eastern Indian craton. Estimated radial RFs show a positive phase at 4.6–5.8s delay time corresponding to the crustal thicknesses of 37–46km. Through the differential evolution (DE) waveform inversion modeling of radial receiver functions, we delineate the crustal structure at 15 broadband stations. On an average, the Archean Singhbhum Odisha Craton (SOC) is characterized by a thick crust of 43±3km in comparison to a relatively thin crust of 41±1km underlying the Proterozoic Chotanagpur Granite Gneissic terrain (CGGT). While, a thin crust of 38±1km characterizes the younger Eastern Ghats Mobile Belt (EGMB). The main results of our modeling reveal a 46km thick Archean crust underlying the Singhbhum granite (SG) of 3.6Ga, which is characterized by a 3km crustal thickening probably resulted from the Archean subduction process. Our modeling also detects a 2–3km crustal thinning with the thinnest crust of 37km below the region near South Singhbhum Shear Zone, which could be attributed to the 1.6Ga plume activity associated with Dalma volcanic. Our modeling also led to the delineation of a crustal thinning of 2–3km underlying the region in EGMB, which was influenced by a much younger (∼117Ma) Rajmahal magmatism associated with the Gondwana break-up episode. However, our study could not detect any age-dependent variation of crustal thicknesses in the eastern Indian craton. The main result of our modeling suggests a two-phase crustal evolution process for the SOC viz. older E-W crustal thickening due to E-W plate compression and later crustal thinning episodes associated with the Dalma volcanism in the north and the Rajmahal volcanism in the South.