Mantle heat flow and thermal structure of the northern block of Southern Granulite Terrain, India

In this study, we calculated the present-day terrestrial heat flow of the Uliastai Depression in Erlian Basin by using systematical steady-state temperature data obtained from four deep boreholes and 89 thermal conductivity measurements from 22 boreholes. Then, we calculated the lithospheric thermal structure, thermal lithospheric thickness, and lithospheric thermo-rheological structure by combining crustal structure, thermal conductivity, heat production, and rheological parameter data. Research from the Depression shows that the present-day terrestrial heat flow ( qs) is 86.3 ± 2.3 mW/m2, higher than the average of 60.4 ± 12.3 mW/m2 of the continental area of China. Mantle heat flow ( qm) in the Depression ranges from 33.7 to 39.3 mW/m2, qm/ qs ranges from 40 to 44%, show that the crust plays the dominant position in the terrestrial heat flow. The thermal thickness of the lithosphere is about 74–88 km and characterized by a “strong crust–weak mantle” rheological characteristic. The total lithospheric strength is 1.5 × 1012 N/m under wet mantle conditions. Present-day geothermal regime indicates that the Uliastai Depression has a high thermal background, the activity of the deep-seated lithosphere is relatively intense. This result differs significantly from the earlier understanding that the area belongs to a cold basin. However, a hot basin should be better consistent with the evidences from lithochemistry and geophysical observations. The results also show the melts/fluids in the study area may be related to the subduction of the Paleo-Asian Ocean. The study of the geothermal regime in the Uliastai Depression provides new geothermal evidence for the volcanic activity in the eastern part of the Central Asian Orogenic Belt and has significant implications for the geodynamic characteristics.

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Paleogeothermal Gradients across an Inverted Hyperextended Rift System (Mauléon Fossil Rift,Western Pyrenees)

10.5194/egusphere-egu2020-22005 ◽

2020 ◽

Author(s):

Nicolas Saspiturry ◽

Abdeltif Lahfid ◽

Thierry Baudin ◽

Laurent Guillou-Frottier ◽

Philippe Razin ◽

...

Keyword(s):

Heat Flow ◽

Thermal Structure ◽

Ductile Deformation ◽

Rift System ◽

Alkaline Magmatism ◽

Distal Margin ◽

Geothermal Gradients ◽

The North ◽

Mantle Heat Flow ◽

Paleogeothermal Gradient

<p>Examples of fossil and present-day passive margins resulting from mantle exhumation at the ocean&#8211;continent transition appear to have developed under conditions of high mantle heat flow. The pattern of geothermal gradients along these hyperextended margins at the time of rifting is of interest for exploration of geothermal and petroleum resources, but is difficult to access. The fossil rift in the North Pyrenean Zone, which underwent high temperature&#8211;low pressure metamorphism and alkaline magmatism during Early Cretaceous hyperextension, was studied to explore the geothermal regime at the time of rifting. Data from a set of 155 samples from densely spaced outcrops and boreholes, analyzed using Raman spectroscopy of carbonaceous material, shed light on the distribution of geothermal gradients across the inverted hyperextended Maul&#233;on rift basin during Albian and Cenomanian time, its period of active extension. The estimated paleogeothermal gradient is strongly related to the structural position along the Albian-Cenomanian rift, increasing along a proximal-distal margin transect from ~34&#176;C/km in the European proximal margin to ~37&#8211;47&#176;C/km in the two necking zones and 57&#8211;60&#176;C/km in the hyperextended domain. This pattern of the paleogeothermal gradient induced a complex competition between brittle and ductile deformation during crustal extension. A numerical modeling approach reproducing the thermal evolution of the North Pyrenees since 120 Ma suggests that mantle heat flow values may have peaked up to 100 mW.m-2 during the rifting event. We demonstrate that the style of reactivation during subsequent convergence influences the thermal structure of the inverted rift system.</p>

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Entropy-information perspective to radiogenic heat distribution in continental crust

Nonlinear Processes in Geophysics ◽

10.5194/npg-20-423-2013 ◽

2013 ◽

Vol 20 (3) ◽

pp. 423-428

Author(s):

R. N. Singh ◽

A. Manglik

Keyword(s):

Heat Flow ◽

Continental Crust ◽

Heat Generation ◽

Depth Distribution ◽

Thermal Structure ◽

Generation Model ◽

Heat Sources ◽

Radiogenic Heat ◽

Entropy Principle ◽

Mantle Heat Flow

Abstract. Depth distribution of radiogenic heat sources in continental crust is an important parameter that controls its thermal structure as well as the mantle heat flow at the base of continental lithosphere. Various models for the depth distribution of radiogenic heat sources have been proposed. Starting from constant and exponential models based on linear heat flow–heat generation relationship the present-day layered models integrate crustal structure and laboratory measurements of radiogenic heat sources in various exposed rocks representing crustal composition. In the present work, an extended entropy theory formalism is used for estimation of radiogenic heat sources distribution in continental crust based on principle of maximum entropy (POME). The extended entropy principle yields a constant heat generation model if only a constraint given by total radiogenic heat in the crust is used and an exponential form of radiogenic heat sources distribution if an additional constraint in the form of a second moment is used in the minimization of entropy.

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Thermal regime of the lithosphere in the Canadian ShieldThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.

Canadian Journal of Earth Sciences ◽

10.1139/e09-059 ◽

2010 ◽

Vol 47 (4) ◽

pp. 389-408 ◽

Cited By ~ 17

Author(s):

Claire Perry ◽

Carmen Rosieanu ◽

Jean-Claude Mareschal ◽

Claude Jaupart

Keyword(s):

Heat Flow ◽

Heat Generation ◽

Seismic Refraction ◽

Surface Heat ◽

Canadian Shield ◽

P Wave ◽

Seismic Velocities ◽

Flow Measurements ◽

Surface Heat Flow ◽

Mantle Heat Flow

Geothermal studies were conducted within the framework of Lithoprobe to systematically document variations of heat flow and surface heat production in the major geological provinces of the Canadian Shield. One of the main conclusions is that in the Shield the variations in surface heat flow are dominated by the crustal heat generation. Horizontal variations in mantle heat flow are too small to be resolved by heat flow measurements. Different methods constrain the mantle heat flow to be in the range of 12–18 mW·m–2. Most of the heat flow anomalies (high and low) are due to variations in crustal composition and structure. The vertical distribution of radioelements is characterized by a differentiation index (DI) that measures the ratio of the surface to the average crustal heat generation in a province. Determination of mantle temperatures requires the knowledge of both the surface heat flow and DI. Mantle temperatures increase with an increase in surface heat flow but decrease with an increase in DI. Stabilization of the crust is achieved by crustal differentiation that results in decreasing temperatures in the lower crust. Present mantle temperatures inferred from xenolith studies and variations in mantle seismic P-wave velocity (Pn) from seismic refraction surveys are consistent with geotherms calculated from heat flow. These results emphasize that deep lithospheric temperatures do not always increase with an increase in the surface heat flow. The dense data coverage that has been achieved in the Canadian Shield allows some discrimination between temperature and composition effects on seismic velocities in the lithospheric mantle.

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Heat Flow, Geotherms, Density and Lithosphere Thickness in SW of Iberia (South of Portugal)

10.31214/ijthfa.v1i1.9 ◽

2018 ◽

Vol 1 (1) ◽

pp. 18-22 ◽

Cited By ~ 1

Author(s):

Maria Rosa Alves Duque

Keyword(s):

Heat Flow ◽

Thermal Structure ◽

Average Density ◽

Ore Deposits ◽

Flow Density ◽

The South ◽

Lithosphere Thickness ◽

Structure Density ◽

Using Data ◽

Lateral Variations

Thermal structure, density distribution and lithosphere thickness in the SW part of the Iberian Peninsula are studied using data obtained in the South Portuguese Zone (SPZ) and SW border of the Ossa Morena Zone (OMZ) in the South of Portugal. Five different regions were defined, and models were built for each region. Geotherms were obtained using average density values from data published. The high values of heat flow density in these regions are attributed to occurrence of anomalous heat sources due to radioactivity content and exothermic chemical reactions associated to ore deposits in the zone. The results obtained with models based on isostasy in the region led to lithosphere thickness values between 95 and 96 km in the SPZ and a lower value of 94.5 km in the SW border of the OMZ. Analysis of geotherms shows lateral variations of temperature at the same depth. These lateral variations are compared with information obtained with seismic data.

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Heat flow distribution and thermal structure of the Nankai subduction zone off the Kii Peninsula

Geochemistry Geophysics Geosystems ◽

10.1029/2011gc003623 ◽

2011 ◽

Vol 12 (10) ◽

pp. n/a-n/a ◽

Cited By ~ 24

Author(s):

Hideki Hamamoto ◽

Makoto Yamano ◽

Shusaku Goto ◽

Masataka Kinoshita ◽

Keiko Fujino ◽

...

Keyword(s):

Heat Flow ◽

Subduction Zone ◽

Thermal Structure ◽

Flow Distribution ◽

Kii Peninsula ◽

Nankai Subduction Zone

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Surface heat flow and lithosphere thermal structure of the Rhenohercynian Zone in the greater Luxembourg region

Geothermics ◽

10.1016/j.geothermics.2015.03.007 ◽

2015 ◽

Vol 56 ◽

pp. 93-109 ◽

Cited By ~ 6

Author(s):

Tom Schintgen ◽

Andrea Förster ◽

Hans-Jürgen Förster ◽

Ben Norden

Keyword(s):

Heat Flow ◽

Thermal Structure ◽

Surface Heat ◽

Surface Heat Flow ◽

Rhenohercynian Zone

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Adjoint inversion of the thermal structure of Southeastern Australia

Geophysical Journal International ◽

10.1093/gji/ggz368 ◽

2019 ◽

Vol 219 (3) ◽

pp. 1648-1659 ◽

Cited By ~ 1

Author(s):

B Mather ◽

L Moresi ◽

P Rayner

Keyword(s):

Thermal Properties ◽

Heat Flow ◽

Heat Production ◽

Thermal Structure ◽

Surface Heat ◽

Flow Data ◽

Data Set ◽

Surface Heat Flow ◽

Southeastern Australia ◽

Curie Depth

SUMMARY The variation of temperature in the crust is difficult to quantify due to the sparsity of surface heat flow observations and lack of measurements on the thermal properties of rocks at depth. We examine the degree to which the thermal structure of the crust can be constrained from the Curie depth and surface heat flow data in Southeastern Australia. We cast the inverse problem of heat conduction within a Bayesian framework and derive its adjoint so that we can efficiently find the optimal model that best reproduces the data and prior information on the thermal properties of the crust. Efficiency gains obtained from the adjoint method facilitate a detailed exploration of thermal structure in SE Australia, where we predict high temperatures within Precambrian rocks of 650 °C due to relatively high rates of heat production (0.9–1.4 μW m−3). In contrast, temperatures within dominantly Phanerozoic crust reach only 520 °C at the Moho due to the low rates of heat production in Cambrian mafic volcanics. A combination of the Curie depth and heat flow data is required to constrain the uncertainty of lower crustal temperatures to ±73 °C. We also show that parts of the crust are unconstrained if either data set is omitted from the inversion.

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