Age dependence of continental heat flow—fantasy and facts

Rao, R. U. M.; Rao, Gang; Reddy, G. K.

doi:10.1016/0012-821x(82)90132-7

Cited by 42 publications

(17 citation statements)

References 24 publications

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“…The data re-emphasize the observation made from previous studies that the greenstone-granite-gneiss terrain of the Dharwar Craton is characterized by low heat flow in the range 25-50 mW m -2 and the variations within the craton are attributable to variations in heat production in the upper crust (Rao et al 1976(Rao et al , 1982Gupta et al 1991;Roy andRao 2000, 2003;Rao et al 2003).…”

Section: Discussionsupporting

confidence: 81%

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Roy

Ray

Bhattacharya

et al. 2007

Int J Earth Sci (Geol Rundsch)

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The Late Archaean Closepet Granite batholith in south India is exposed at different crustal levels grading from greenschist facies in the north through amphibolite and granulite facies in the south along a *400 km long segment in the Dharwar craton. Two areas, Pavagada and Magadi, located in the Main Mass of the batholith, best represent the granitoid of the greenschist and amphibolite facies crustal levels respectively. Heat flow estimates of 38 mW m -2 from Pavagada and 25 mW m -2 from Magadi have been obtained through measurements in deep (430 and 445 m) and carefully sited boreholes. Measurements made in four boreholes of opportunity in Pavagada area yield a mean heat flow of 39 ± 4 (s.d.) mW m -2 , which is in good agreement with the estimate from deep borehole. The study, therefore, demonstrates a clear-cut heat flow variation concomitant with the crustal levels exposed in the two areas. The mean heat production estimates for the greenschist facies and amphibolite facies layers constituting the Main Mass of the batholith are 2.9 and 1.8 lW m -3 , respectively. The enhanced heat flow in the Pavagada area is consistent with the occurrence of a radioelement-enriched 2-km-thick greenschist facies layer granitoid overlying the granitoid of the amphibolite facies layer which is twice as thick as represented in the Magadi area. The crustal heat production models indicate similar mantle heat flow estimates in the range 12-14 mW m -2 , consistent with the other parts of the greenstone-granite-gneiss terrain of the Dharwar craton.

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Section: Discussionsupporting

confidence: 81%

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Roy

Ray

Bhattacharya

et al. 2007

Int J Earth Sci (Geol Rundsch)

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“…The data from late Paleozoic, early Paleozoic, late Proterozoic, and early Proterozoic sites indicate similar distributions of heat flow values within these provinces, but for Archean sites the average heat flow is lower, and the apparent scatter of the data is about half that of Proterozoic and Paleozoic sites. These basic features of the global continental heat flow data set are also apparent in a more detailed analysis of the data by Rao et al [1982]. With reference to the present study, the data indicate that heat flow is, on average, lower and more consistent at Archean sites than at younger sites.…”

Section: Introductionsupporting

confidence: 73%

“…Continental heat flow data compiled by Chapman and Furlong [1977] as a function of "tectonothermal" age (the age of the last major tectonic and/ or magmatic event in an area) are shown in Figure 1. The use of normal distribution statistics in this plot may not have any true statistical meaning since examination of the data sets in each group indicates that they are multimodal [Rao et al, 1982;, but the apparent standard deviations of the means do give some indication of the relative scatters of the data sets in each age group. Data from Cenozoic and Mesozoic sites indicate that, on average, heat flow is higher at these sites than at older sites and that the data are more scattered than from older sites.…”

Section: Introductionmentioning

confidence: 99%

Crustal radiogenic heat production and the selective survival of ancient continental crust

Morgan

1985

J. Geophys. Res.

104

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If the oldest terrestrial rocks are to be used as a representative sample of the early terrestrial crust, it is important to consider the possibility that they may represent a biased sample. Chemical data indicate that Archean crust is on average depleted in potassium, uranium, and thorium relative to younger crust. Radiogenic isotopes of these elements produce a significant portion of surface heat flow from continents, and low mean heat flow in Archean terrains relative to younger terrains also indicates that these elements are relatively depleted in Archean crust. In stable continental lithosphere the primary variable controlling variations in the geotherm is crustal radiogenic heat production. Qualitative evidence suggests that terrains with low radiogenic heat production, and thus a relatively cool geotherm, are less susceptible to magmatic and tectonic reactivation than terrains with higher heat production and a hotter geotherm. Since crustal radiogenic isotope abundances must have been greater in the past if the isotopes were immobile in stable crust, the relative effect of crustal heat production must have been greater, and thus the range in geotherms must have been greater for the same mantle heat flow. It is suggested that crust with low heat production is less susceptible to orogenic reworking than high heat production crust, and thus there may have been selective stabilization of low heat production (low potassium, uranium, and thorium) crust early in earth history. Either Archean crustal generation was by a mechanism that perhaps fortuitously produced only low heat production crust, or all high heat production crust was reworked by orogenesis during the Archean and did not stabilize in significant volumes until the earliest Proterozoic, perhaps in association with a reduction in mantle temperatures and mean heat flow. If selective crustal reworking did operate during the Archean, surviving Archean terrains may represent a biased sample of the early terrestrial continental crust.

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“…The main feature of this study is the delineation of a high‐velocity (7.5 km/s) and high‐density (3.05 g/cm 3 ) layer above the Moho, which is attributed to the emplacement of mafic underplating material at the base of the crust via mantle diapirism in this pull‐apart rift basin. The underplating is supported by anomalous high heat flux (77 mW/m 2 ) in the region as compared to that (average 30 mW/m 2 ) of the stable shield and other cratonic regions of India [ Rao et al , 1982]. The reduced crustal thickness (35–37 km) compared to the average Moho depth (∼42 km) of adjacent areas of the shield, Godavari graben, and east of Narmada lineament in central India [ Kaila and Sain , 1997] also bolster the crustal underplating in the Mahanadi delta.…”

Section: Discussionmentioning

confidence: 99%

“…A careful study indicates that the heat flux values in the Indian Gondwana basins surrounding the Mahanadi basin range from 49 to 107 mW/m 2 with a mean value of 77 mW/m 2 [ Rao and Rao , 1980, 1983]. This is very high compared to that (average of 30 mW/m 2 ) of the stable shield and other cratonic regions of India [ Rao et al , 1982]. Magmatic underplating has been invoked in recent years as a mechanism of crustal growth in which new material is added to the base of existing crust during the periods of high heat flow and crustal extension [ Furlong and Fountain , 1986; White and McKenzie , 1989].…”

Section: Introductionmentioning

confidence: 99%

Evidence of underplating from seismic and gravity studies in the Mahanadi delta of eastern India and its tectonic significance

2004

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We have imaged the crustal configuration of the Mahanadi delta of eastern India by modeling both wide‐angle seismic and Bouguer gravity data. This delta has undergone several stages of rifting, subsidence, sedimentation, and uplift. It is one of the important Gondwana sedimentary basins of India where widespread volcanic activity occurred during the Early Cretaceous along the rift zones. This volcanic activity corresponds to the breakup of greater India from east Gondwana (e.g., present Antarctica and Australia). We have derived a five‐layer crustal model with velocities of 6.0, 6.5, 6.0, 7.0, and 7.5 km/s having estimated densities of 2.7, 2.8, 2.65, 2.9, and 3.05 g/cm3, respectively. The velocity‐density relation along with heat flux and other geological/geochronological information indicates typical rift‐related evolution of the delta with a midcrustal low‐velocity (6.0 km/s) and low‐density (2.65 g/cm3) zone and a ∼10 km thick high‐velocity (7.5 km/s) and high‐density (3.05 g/cm3) layer at the base of the crust, presumably due to underplating. The Moho upwarping or crustal thinning in the rift zone and emplacement of thick, high‐velocity material at the base of the crust strongly suggests basaltic underplating probably due to the Kerguelen hot spot activity. These activities are synchronous with ∼117 Ma Rajmahal volcanism in northeast India and the Lambert graben in East Antarctica and are closely associated with the Gondwana breakup in the India‐Antarctica sector. The rifting stages are closely correlated with the sedimentation phases of the lower and upper Gondwana deposits in the Mahanadi delta, which evolved parallel to the Lambert graben in East Antarctica.

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Age dependence of continental heat flow—fantasy and facts

Cited by 42 publications

References 24 publications

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Crustal radiogenic heat production and the selective survival of ancient continental crust

Evidence of underplating from seismic and gravity studies in the Mahanadi delta of eastern India and its tectonic significance

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