Geothermal gradient and heat flow data in and around Japan (II): Crustal thermal structure and its relationship to seismogenic layer

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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Terrestrial heat flow and crustal thermal structure in the northern slope of Tazhong uplift in Tarim Basin

Geothermics ◽

10.1016/j.geothermics.2019.101709 ◽

2020 ◽

Vol 83 ◽

pp. 101709

Author(s):

Yuchen Liu ◽

Nansheng Qiu ◽

Huili Li ◽

Anlai Ma ◽

Jian Chang ◽

...

Keyword(s):

Heat Flow ◽

Tarim Basin ◽

Thermal Structure ◽

Northern Slope ◽

Terrestrial Heat Flow ◽

Crustal Thermal Structure ◽

Tazhong Uplift

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Terrestrial heat flow and crustal thermal structure of the Gonghe-Guide area, northeastern Qinghai-Tibetan plateau

Geothermics ◽

10.1016/j.geothermics.2017.11.011 ◽

2018 ◽

Vol 72 ◽

pp. 182-192 ◽

Cited By ~ 22

Author(s):

Chao Zhang ◽

Guangzheng Jiang ◽

Yizuo Shi ◽

Zhuting Wang ◽

Yi Wang ◽

...

Keyword(s):

Heat Flow ◽

Tibetan Plateau ◽

Thermal Structure ◽

Terrestrial Heat Flow ◽

Crustal Thermal Structure

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Towards a global lithospheric thermal model

10.5194/egusphere-egu2020-19005 ◽

2020 ◽

Author(s):

Sheona Masterton ◽

Samuel Cheyney ◽

Chris Green ◽

Peter Webb

Keyword(s):

Heat Flow ◽

Curie Temperature ◽

Thermal Structure ◽

Magnetic Layer ◽

Surface Heat ◽

Local Context ◽

Magnetic Data ◽

Flow Data ◽

Surface Heat Flow ◽

Temperature Depth

Temperature and heat flow are key parameters for understanding the potential for source rock maturation in sedimentary basins. Knowledge of the thermal structure of the lithosphere in both a regional and local context can provide important constraints for modelling basin evolution through time.In recent years, global coverage of heat flow data constraints have enhanced scientific understanding of the thermal state of the lithosphere. However, sample bias and variability in sampling methods continues to be a major obstacle to heat flow-derived isotherm prediction, particularly in frontier areas where data are often sparse or poorly constrained. Consideration and integration of alternative approaches to predict temperature at depth may allow interpolation of surface heat flow in such data poor areas. &#160;&#160;We have attempted to integrate three independent approaches to modelling temperature with depth. The first approach is based on heat flow observations, in which a 1D steady-state model of the lithosphere is constructed from quality-assessed surface heat flow data, crustal thickness estimates and associated lithospheric thermal properties. The second approach is based on terrestrial (airborne, ground and shipborne) magnetic data, in which the maximum depth of magnetisation within the lithosphere is estimated using a de-fractal method and used as a proxy for Curie temperature depth. The third approach is based on satellite magnetic data and estimates the thickness of the magnetic layer within the lithosphere based on the varying amplitudes of satellite magnetic data, accounting for global variations in crustal magnetisation. Curie temperature depth results from each of these approaches have been integrated into a single global grid, then used to calculate temperature-depth variations through the crust.We have evaluated our isotherm predictions by comparing them with temperature-depth control points and undertook qualitative and quantitative analyses of discrepancies that exist between different modelling approaches; this has provided insights into the origin of such discrepancies that can be integrated into our models to generate a better controlled global temperature-depth result. &#160;We present details of our methodology and the results of our integrated studies. We demonstrate areas where the independent results are in good agreement, providing vital information for high-level basin screening. We also highlight areas of disagreement and suggest possible causes for these discrepancies and potential resolutions.

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Thermal data collection in and around Japan and its implications for lithospheric rheology and deformation

10.5194/egusphere-egu2020-21030 ◽

2020 ◽

Author(s):

Akiko Tanaka

Keyword(s):

Heat Flow ◽

Data Collection ◽

Depth Distribution ◽

Thermal State ◽

Thermal Structure ◽

Geothermal Gradient ◽

Geological Processes ◽

Thermal Data ◽

Lithospheric Thermal Structure ◽

Geochemical Constraints

Heat flow data contribute to the imaging the lithospheric thermal structure, which greatly influences tectonic and geological processes and constrains the strength of the lithosphere, the modes of deformation, and the depth distribution of earthquakes. To provide more reliable estimation of the lithospheric thermal structure, some complementary approaches are possible. One of approaches is to update and incorporate the existing thermal data. A new version of database &#8220;Thermal Data Collection in and around Japan&#8221;, which contains continuously updated of heat flow and geothermal gradient data and adds thermal conductivity data in and around Japan, has been released in March 2019 [https://www.gsj.jp/data/G01M/GSJ_MAP_TDCJ_2019.zip]. This provides an opportunity to revisit the thermal state of the lithosphere along with other geophysical/geochemical constraints and on the lithospheric rheology and deformation, which is sensitive to temperature.

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Anelasticity and thermal structure of the oceanic upper mantle: Temperature calibration with heat flow data

Journal of Geophysical Research Atmospheres ◽

10.1029/jb094ib05p05705 ◽

1989 ◽

Vol 94 (B5) ◽

pp. 5705 ◽

Cited By ~ 43

Author(s):

Hiroki Sato ◽

I. Selwyn Sacks

Keyword(s):

Heat Flow ◽

Upper Mantle ◽

Thermal Structure ◽

Temperature Calibration ◽

Flow Data ◽

Mantle Temperature

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Summary of heat flow studies in Nigeria

Journal of the Belarusian State University. Geography and Geology ◽

10.33581/2521-6740-2019-2-121-132 ◽

2019 ◽

pp. 121-132

Author(s):

Vladimir I. Zui ◽

Lukman Akinyemi

Keyword(s):

Magnetic Field ◽

Heat Flow ◽

Heat Conductivity ◽

Traditional Approach ◽

Geothermal Gradient ◽

Depth Interval ◽

Flow Density ◽

Flow Data ◽

Heat Flow Density ◽

Two Parameters

A traditional approach for heat flow determination requires two parameters. They are a geothermal gradient and heat conductivity of rocks comprising the considered depth interval. The geothermal gradient is determined from a thermogram recorded in a wellbore and the heat conductivity is obtained from the laboratory measurements of selected rock samp les. There are some variations of this approach to both get the gradient and heat conductivity values. However, there are many areas without boreholes to register their thermograms, or at least to have several temperature readings at intermediate positions of bottom holes and traditional methods of heat flow determinations cannot be used. Recently another method was proposed to estimate heat flow. It was derived from spectral analysis of magnetic field. During last years it was widely used in Nigeria for areas where deep boreholes are absent. It uses estimates of depths to the base and bottom of the causative body derived from analysis of the magnetic field maps. The base of the causative body corres ponds to the depth of the Curie surface at which rocks lose their magnetic properties. It is known that it happens at the temperature around 580 °C that slightly varies depending on the content of magnetite within the causative body. The temperature at the top of this body is estimated. The heat flow density can be calculated knowing the geothermal gradient within this depth interval and heat conductivity of rocks. A preliminary heat flow density map was compiled based on all accessible heat flow data. A comparison of heat flow data from several regions of the country, determined using both methods provides rather good agreement.

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Regional estimation of Curie-point depths and succeeding geothermal parameters from recently acquired high-resolution aeromagnetic data of the entire Bida Basin, north-central Nigeria

Geothermal Energy Science ◽

10.5194/gtes-5-1-2017 ◽

2017 ◽

Vol 5 (1) ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Levi I. Nwankwo ◽

Abayomi J. Sunday

Keyword(s):

High Resolution ◽

Heat Flow ◽

Curie Point ◽

Thermal Structure ◽

Geothermal Gradient ◽

North Central ◽

Geodynamic Processes ◽

Regional Estimation ◽

Heat Flow Variations ◽

Geothermal Parameters

Abstract. A regional estimation of Curie-point depths (CPDs) and succeeding geothermal gradients and subsurface crustal heat flow has been carried out from the spectral centroid analysis of the recently acquired high-resolution aeromagnetic (HRAM) data of the entire Bida Basin in north-central Nigeria. The HRAM data were divided into 28 overlapping blocks, and each block was analysed to obtain depths to the top, centroid, and bottom of the magnetic sources. The depth values were then used to assess the CPD, geothermal gradient, and subsurface crustal heat flow in the basin. The result shows that the CPD varies between 15.57 and 29.62km with an average of 21.65km, the geothermal gradient varies between 19.58 and 37.25°Ckm−1 with an average of 27.25°Ckm−1, and the crustal heat flow varies between 48.41 and 93.12mWm−2 with an average of 68.80mWm−2. Geodynamic processes are mainly controlled by the thermal structure of the Earth's crust; therefore this study is important for appraisal of the geo-processes, rheology, and understanding of the heat flow variations in the Bida Basin, north-central Nigeria.

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