P-T Conditions and Geothermal Gradients of Gneiss--Enderbite Rocks: Dharmapuri Area, Tamil Nadu, India

Rao, D. R. K.; Narayana, B. L.; Charan, S. N.; Natarajan, R.

doi:10.1093/petrology/32.3.539

Cited by 28 publications

(11 citation statements)

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“…Due to the loss of most of its lithospheric mass, the thin Indian plate buckled, followed by erosion. Geothermobarometry studies indicate that the maximum pressure and temperature reported in the southern part of Indian continent can reach up to ~8 ± 1.5 kb and 775 ± 30°C [ Rao et al ., ], respectively, suggesting the exhumation of intermediate to lower parts of the crust. The geotectonic history, geochemistry, and geophysical signatures all along the Indian plate are quite different.…”

Section: Discussionmentioning

confidence: 99%

Imaging the lithosphere‐asthenosphere boundary of the Indian plate using converted wave techniques

Kumar

Srijayanthi

et al. 2013

JGR Solid Earth

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[1] The lithospheric structure of the Indian plate has been investigated using converted wave techniques (P and S receiver functions) and a novel stacking analysis technique (without using deconvolution) applied to a large seismological data set from permanent and temporary broadband seismic stations. We observe coherent energy from at least two seismic discontinuities, i.e., the crust-mantle (Moho) and lithosphere-asthenosphere boundary (LAB) in the uppermost mantle. Here we provide a novel seismic image of the Indian lithosphere showing definitive evidence of its flexure, which is interpreted to be primarily caused by the hard collision at~55 Myr resulting in the world's highest mountain chain-the Himalayas and the Tibetan plateau. Results from geoidal and gravity studies do suggest postcollisional flexuring of the Indian plate; however, the flexure lacks observational constraints. The observed wavelength of the flex is~1000 km with the thickness of the Indian shield lithosphere varying from~70 km to 140 km; such a low value for a continent implies that the Indian plate has been reworked in the past. The plate deepens in the Himalayan region to a depth of~170 km. Further, the converted phases are interpreted to be resulting from the bottom of the lithosphere. We clearly demonstrate that these are distinct and different from the midlithospheric discontinuity. For a large number of stations, the midlithospheric discontinuity and LAB are clearly separated in depth. Our observations suggest that the Archaean lithosphere is no longer intact and is prone to deformation.

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Section: Discussionmentioning

confidence: 99%

Imaging the lithosphere‐asthenosphere boundary of the Indian plate using converted wave techniques

Kumar

Srijayanthi

et al. 2013

JGR Solid Earth

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“…The DP shows a general increase in the grade of metamorphism from greenschist through amphibolite facies, from the north to the south. South of the orthopyroxene isograd, in the granulites, there is a well-documented, systematic increase in metamorphic pressure in some sectors (e.g., Dharmapuri-Namakkal), culminating in the highest pressures of 10-11 kbar just north of a major lineament designated as Palghat-Cauvery lineament (PCL) [Hansen et al, 1984Drury et al, 1984;Raith et al, 1983Raith et al, , 1990Raase et al, 1986;Rameshwar Rao et al, 1991a;Eckert and Newton, 1993;Bhaskar Rao et al, 1996]. The PCL with E-W strike serves as a notional divide between two blocks in the SGP, namely, the northern block (NB) and the southern block (SB) [Harris et al, 1994].…”

Section: Geologymentioning

confidence: 99%

High mantle heat flow in a Precambrian granulite province: Evidence from southern India

et al. 2003

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[1] Twelve new heat flow values determined at nine sites and heat production estimated from radioelemental measurements at 330 sites in the southern granulite province (SGP) bring out contrasting crustal and subcrustal thermal characteristics between the SGP and the adjacent Archaean Dharwar greenstone-granite-gneiss province (DP) in south India. A twolayer granulitic crust of Late Archaean charnockites and gneisses characterizes the northern block (NB), north of the Palghat-Cauvery lineament (PCL). The heat production of the upper, 7-10 km thick, metasomatized granulitic layer ranges between 0.2 and 0.75 mW m À3 (mean 0.5 ± 0.3 (SD) mW m À3 ). This layer overlies radioelement-depleted granulites characterized by very low heat production ranging from 0.14 to 0.2 mW m À3 (mean 0.16 ± 0.07(SD) mW m À3). In a large sector of the NB, erosion of the upper metasomatized granulite layer has laid bare the depleted granulitic rocks, which represent one of the lowest heat-producing crustal sections. The mean heat flow in the NB is 36 ± 4 mW m À2 (N = 10). The southern block (SB), south of PCL, in contrast to the NB, comprises complexly interlayered charnockites, gneisses, granites, khondalites, and leptynites, which have variable and much higher levels of heat production ranging between 1.11 and 2.63 mW m À3 . The heat flow in the SB is 47 ± 8 mW m À2 (N = 3). Overall, the range of heat flow values in the SGP is within the range for the DP. Mantle heat flow in the NB, both from the lowest heat-producing sector and other areas, is deduced in the light of heat production and heat flow data, at 23-32 mW m À2 , whose values are distinctly higher than 11-16 mW m À2for the adjacent DP. The higher mantle heat flow in the NB appears to be a consequence of higher heat production in the subjacent mantle.

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“…These are collectively referred to as the ''Peninsula Gneisses" and form most of the Dharwar Craton although the protolith is more ancient and Na-rich sialic crust was present here in early Archaean times (3400-3000 Ma) prior to formation of the schist belts (Beckinsale et al, 1980;Taylor et al, 1984). Low to medium metamorphic grades ranging from upper greenschist to upper amphibolite are typical of this region and were uplifted from depths of 10-15 km (Rameshwar Rao et al, 1991) prior to formation of the Cuddapah Basin in the NE (Fig. 1).…”

Section: Geological Frameworkmentioning

confidence: 88%

Palaeomagnetic and rock magnetic study of charnockites from Tamil Nadu, India, and the ‘Ur’ protocontinent in Early Palaeoproterozoic times

Mondal

Piper

Hunt

et al. 2009

Journal of Asian Earth Sciences

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P-T Conditions and Geothermal Gradients of Gneiss--Enderbite Rocks: Dharmapuri Area, Tamil Nadu, India

Cited by 28 publications

References 0 publications

Imaging the lithosphere‐asthenosphere boundary of the Indian plate using converted wave techniques

Imaging the lithosphere‐asthenosphere boundary of the Indian plate using converted wave techniques

High mantle heat flow in a Precambrian granulite province: Evidence from southern India

Palaeomagnetic and rock magnetic study of charnockites from Tamil Nadu, India, and the ‘Ur’ protocontinent in Early Palaeoproterozoic times

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