Mantle discontinuities beneath the Deccan volcanic province

Kumar, M. Ravi; Gurusamy, Mohan

doi:10.1016/j.epsl.2005.06.034

Cited by 44 publications

(14 citation statements)

References 48 publications

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“…Lower crustal velocities under the EDC are consistently in the 3.8–3.9 km/s range, while lower crustal velocities under the Deccan Traps are in the 3.9–4.0 km/s range. A comparison to independent velocity‐depth profiles from receiver functions [ Ravi Kumar and Mohan , 2005; S. S. Rai et al , 2003; Ravi Kumar et al , 2001] is again provided in Figure 6 and, except for station KRD, the comparison is good. Crustal thicknesses under the Deccan Traps were reported in the 36–40 km range along the Koyna I and II DSS profiles [ Kaila and Krishna , 1992; Krishna et al , 1991, 1989], which is consistent with our inferred values.…”

Section: Crustal Structure Variationmentioning

confidence: 92%

“…Most recently, point estimates of the bulk Vp/Vs ratio and thickness of the crust have been obtained for a number of broadband stations from receiver functions [ Gupta et al , 2003a, 2003b; S. S. Rai et al , 2003, 2005, 2006; Jagadeesh and Rai , 2008; Ravi Kumar et al , 2001; Sarkar et al , 2003; Ravi Kumar and Mohan , 2005; Mohan and Ravi Kumar , 2004; Gaur and Priestley , 1997; Zhou et al , 2000; Kiselev et al , 2008; Rai et al , 2009]. The majority of these receiver function studies concentrate in the south Indian shield, and have reported significant changes in crustal thickness among its building terranes.…”

Section: Geology and Crustal Structurementioning

confidence: 99%

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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

Julià¹,

Jagadeesh²,

S.³

et al. 2009

J. Geophys. Res.

108

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[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,

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Section: Crustal Structure Variationmentioning

confidence: 92%

Section: Geology and Crustal Structurementioning

confidence: 99%

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

Julià¹,

Jagadeesh²,

S.³

et al. 2009

J. Geophys. Res.

108

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“…While the low‐density layer reported (Pandey et al 1996) is based on widely spaced gravity data and is modelled to be uniform, the LVZ delineated in the present study is non‐uniform and varies in magnitude between stations. The upper mantle image down to 700 km beneath DVP reveals that the LVZ is confined only to the shallow upper mantle and, therefore, maybe unrelated to any large scale processes such as the Deccan episode (Ravi Kumar & Mohan 2005). Low‐velocity zones are manifestations of thermal/chemical anomalies associated with regional/local causatives.…”

Section: Discussionmentioning

confidence: 99%

Crustal constraints on the uplift mechanism of the Western Ghats of India

Tiwari¹,

Surve²,

Gurusamy³

2006

Geophysical Journal International

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S U M M A R YOver 800 receiver functions (RFs) from three broadband and five short period stations deployed in the northern segment of the Western Ghats of India, were analysed to examine the crustal constraints on the rift flank uplift mechanism of the Ghats. Estimates of Moho depths, mean shear velocities and Poisson's ratios were determined and used as constraints to model the RFs. The study reveals that the crust beneath the Ghats varies in thickness between 31 and 39 km and is neither uniformly thin nor thick as required by existing hypotheses for uplift mechanism. The Poisson's ratio is 0.26 and the mean shear velocity is 3.65 km s −1 . The uncertainties in the estimates of the Moho depths and Poisson's ratios are ±2 km and ±0.01, respectively. The crust beneath the Ghats is 3-4 km thinner than that beneath the adjoining low-lying coastal plains suggesting block tectonics. Modelling the RFs using crustal constraints reveals sub-Moho low-velocity zones (LVZs) with velocity reductions of 0.5-0.65 km s −1 which are confined to shallow depths of about 50 km beneath the Ghats. The persistent relief of the Ghats may be attributed to the buoyancy forces of the possibly rift related shallow upper mantle LVZs beneath the Ghats.

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“…(Rathore et al 2000;Fig.3. Mean S-wave velocity variation beneath south Indian shield as computed from recently acquired seismic data (Rai et al 1999(Rai et al , 2003Ravi Kumar et al 2001;Sarkar et al 2003;Gupta and Rai, 2005;Ravi Kumar and Mohan, 2005). For comparison, crustal velocity distribution as predicted by average 1-D global model ak 135 (Kennett et al 1995) as well as that inferred for global shields and platforms (Christensen and Mooney, 1995) are also included.…”

Section: Deccan Volcanics Sedimentsmentioning

confidence: 99%

Shallowing of mafic crust and seismic instability in the high velocity Indian Shield

Pandey

2009

J Geol Soc India

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Indian shield has been frequented by number of large and moderate magnitude damaging earthquakes since historical times, including the recent disastrous ones like Latur Mw 6.3 in 1993, Jabalpur Mw 5.8 in 1997 and Bhuj Mw 7.7 in 2001. Seismogenesis of these events is still not understood well. Detailed study of nine such earthquake localities (as appended in Table 1), indicates quite high P-and S-velocities (6.2 -6.7 km/s and 3.65 -3.90 km/s respectively) at a shallow depth of almost surface to six kilometers. These seismogenic regions appear to be in a state of continuous uplift and erosion since geological times, which brought mafic (granulitic/amphibolitic) crust to significantly shallow levels in which stresses are accummulated due to ongoing local uplift and a high input of heatflow from the mantle. These stresses act over and above to the regional compressive stresses generated by India-Eurasia collision. As against common belief, the role played by fluids in nucleation of such earthquakes, in the relatively denser and high velocity Indian crust (compared to the other global stable continental regions), appears limited.

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Mantle discontinuities beneath the Deccan volcanic province

Cited by 44 publications

References 48 publications

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

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 constraints on the uplift mechanism of the Western Ghats of India

Shallowing of mafic crust and seismic instability in the high velocity Indian Shield

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