Thickness, composition, and evolution of the Indian Precambrian crust inferred from broadband seismological measurements

The nature and thickness of lithosphere beneath the Archean Dharwar Craton, southern India: A magnetotelluric model

“…Other receiver function studies Ramesh et al, 2010) identified low velocity layers around 100 km. In view of variation of electrical resistivity around 120 km, we presume that the composition of the top part of the upper mantle is characterized by spinel peridotites underlain by garnet peridotites following the model given in Jagadeesh and Rai (2008). This is also in consistent with sections proposed by Griffin et al (2009) using xenolith data.…”

“…Gupta et al (2003) taking clues from this study and based on faster arrivals of teleseismic P and S waves, proposed a lithosphere thickness of 200 km for the EDC and about 260 km for the WDC. A more recent study (Jagadeesh and Rai, 2008) observed a positive phase with arrival time at 9-10 s while analyzing the receiver functions from a number of stations in the southern Indian shield and traced the Hales discontinuity -where phase transition from spinel peridotite to garnet peridotite occurs (Hales, 1969) -to be around 70-80 km. In another study, Kumar et al (2007) used shear-wave receiver functions and reported a lithospheric thickness of 80-100 km for the Indian tectonic plate, particularly to Dharwar Craton, in contrast to 180-300 km thick lithosphere in other crustal fragments of the Gondwana supercontinent assembly where southern Indian occupied a central position.…”

“…In the southern Indian shield region, a few MT studies have been carried out (Gokarn et al, 1992(Gokarn et al, , 2004; Patro and Sarma, Gokarn et al (1992Gokarn et al ( , 2004, Gupta et al (2003), Jagadeesh and Rai (2008), Patro andSarma (2009), Ramesh et al (2010)). Contours showing lithospheric thickness derived from heat flow studies are also shown (modified after Negi et al (1986)).…”

Crustal density structure across the Central Indian Shear Zone from gravity data

“…Recently, a similar upper mantle density beneath the Southern Granulite Terrain is hypothesized as a highly remobilised lithosphere due to crustal delamination (Singh et al, 2006, in press;Niraj Kumar et al, 2009a,b, 2010. Chemical stratification of the Indian lithospheric mantle with the upper lithosphere (up to 80 km) comprising of the spinel peridotite (of lower density) and the lower lithosphere with that of garnet peridotite composition (of higher density) may be the other distinct possibility (Jagadeesh and Rai, 2008). A detailed and high resolution integrated geophysical mapping of the region is therefore necessary to determine the nature of the upper mantle more conclusively.…”

Insights into the Crustal Structure and Geodynamic Evolution of the Southern Granulite Terrain, India, from Isostatic Considerations

“…A lower Poisson's ratio (0.25-0.28) than that expected for a high-grade metamorphic terrain indicates a felsic to intermediate crust beneath the SGT (GUPTA et al, 2003). The observation is hypothesized as a consequence of post-collision modification of the initial mafic lower crust through the process of lithospheric delamination leaving a felsic to intermediate component (JAGADEESH and RAI, 2008). An almost flat Moho along the Kuppam-Palani geotransect together with an upper crustal extensional regime convincingly indicates that the upper crust must have decoupled from the lower crust (RAO and PRASAD, 2006).…”