Deep crustal structure of the Indian shield from joint inversion of P wave receiver functions and Rayleigh wave group velocities: Implications for Precambrian crustal evolution

Abstract

[1] The S wave velocity structure of the crust and uppermost mantle of the Indian shield has been investigated by jointly inverting P wave receiver functions and Rayleigh wave group velocities at 38 broadband stations in the subcontinent. The Indian shield is an amalgamation of several terranes of Archean and Proterozoic age that were partly flooded by Deccan Trap volcanism during Cenozoic times and that make up a natural laboratory for assessing models of Precambrian crustal evolution. Our results reveal significant variations in crustal thickness and deep crustal velocities: 45-50 km thick under the Archean West Dharwar craton and Southern Granulite Terrane, with lower crustal velocities around 4.1 km/s; 32 -35 km thick beneath the Archean East Dharwar and Bundelkhand cratons, with lower crustal velocities around 3.8-3.9 km/s; 50-65 km thick under the Proterozoic Bhandara craton, with lower crustal velocities around 4.2-4.3 km/s; and $55 km thick under the Proterozoic Aravalli-Delhi belt, with lower crustal velocities around 4.2 km/s. S velocities in the 4.1-4.3 km/s range in the deep crust can be attributed to mafic lithologies, suggesting there has been no secular change in the Precambrian evolution of the south Indian shield. Moreover, pervasive mafic dike swarming throughout the Indian shield suggests that the layer of mafic cumulates is 2.5-1.6 Ga old and that it delaminated from some Archean terranes. Our interpretation is that mafic underplating of the terranes making up the Indian shield occurred in Proterozoic times and that a refractory root developed under the Archean terranes after the Proterozoic event.Citation: Julià, J., S. Jagadeesh, S. S. Rai, and T. J. Owens (2009), Deep crustal structure of the Indian shield from joint inversion of P wave receiver functions and Rayleigh wave group velocities: Implications for Precambrian crustal evolution,

Crustal structure of the eastern Borborema Province, NE Brazil, from the joint inversion of receiver functions and surface wave dispersion: Implications for plateau uplift

“…A quick examination confirms the general trends described in section 2.3. Crustal thicknesses were inferred from the velocity‐depth profiles by considering a cutoff velocity of ∼4.3 km/s to separate crust from uppermost mantle [see, e.g., Julia et al , ]. The inferred values are displayed in Figure , and are essentially the same that were reported in Luz et al [] from H ‐ κ stacking analysis of a similar receiver function data set.…”

Crustal structure of southern Madagascar from receiver functions and ambient noise correlation: Implications for crustal evolution

“…However, others consider the Antananarivo domain as an individual terrane (named Azania by Collins and Pisarevsky []) with African affinities [e.g., Kröner , ; Collins , ; Collins and Windley , ]. The crustal structure in India is well known from the joint inversion of receiver functions and Rayleigh surface wave dispersions [ Julià et al , ]. The crust in the Antananarivo domain (38–43 km) is relatively thicker compared to the crust (32–35 km) (Figure ) of the Eastern Dharwar Craton that—according to Tucker et al []—can be considered as the eastern equivalent to the Antananarivo domain rimming the former core of the Antongil‐Masora‐Western Dharwar craton as part of the former Greater Dharwar craton.…”

Crustal Structure Beneath India and Tibet: New Constraints From Inversion of Receiver Functions

“…A thickened crust beneath the NSL is seen, akin to the results from earlier studies (Jagadeesh & Rai, ; Kumar et al, ). Superimposing the crustal thickness estimates from earlier studies (Singh et al, ) over the CCP image reveals (Figure ) that the Moho is close to 65 km at two locales south of the NSL (from Julià et al, ). Although the possibility of continuation of the rift signature beneath the DVP exists, no definite conclusion can be drawn, at present.…”