scholarly journals Assessment of Gas Hydrate Resources in Ross Sea Area, Antarctica Based on Inversion of Gravity and Magnetic Data

2020 ◽  
Author(s):  
Wei Wang ◽  
Meng Wan ◽  
Miaojun Sun ◽  
Weijie Jiang ◽  
Ping Xu ◽  
...  
Keyword(s):  
Heat Flow ◽  
Gas Hydrate ◽  
Ross Sea ◽  
Thermal Structure ◽  
Magnetic Data ◽  
Moho Depth ◽  
Structure Information ◽  
Curie Depth ◽  
Pacific Side ◽  
Sea Area

Abstract Ross Sea is a large bay located in the fan-shaped area on the Pacific side of Antarctica. In this paper, the power spectrum method is used to invert the Curie depth of the Ross Sea area by(through) the magnetic anomaly data; the Parker-Oldenburg method is used to invert the moho depth; according to Curie depth and the moho depth, the heat flow of the Ross Sea area is inverted, obtained high-precision thermal structure information. According to the temperature-pressure equation for formation and storage of gas hydrate, the thickness of the gas hydrate stability zone is quantitatively calculated based on the heat flow data of the study area, and a integral method is used to estimate the resource prospects of gas hydrate in this area. The results show that the estimated volumes of gas hydrate resources in the Ross Sea are 2.77×1011 m3.

scholarly journals Assessment of Gas Hydrate Resources in Ross Sea Area, Antarctica Based on Inversion of Gravity and Magnetic Data

2021 ◽  
Author(s):  
wei Wang ◽  
meng Wan ◽  
miaojun Sun ◽  
weijie Jiang ◽  
ping Xu
Keyword(s):  
Heat Flow ◽  
High Precision ◽  
Gas Hydrate ◽  
Ross Sea ◽  
Magnetic Data ◽  
Moho Depth ◽  
Gravity And Magnetic ◽  
Curie Depth ◽  
Sea Area ◽  
Gravity And Magnetic Data

Abstract The Ross Sea is located between Victoria Land and Mary Bird Land in West Antarctica. In this paper, the published gravity and magnetic data in the Ross Sea area are fused with the high-precision gravity and magnetic data measured by the ship. Then, The gravity anomaly data is used to invert the Moho depth by the Parker-Oldenburg method; the magnetic anomaly data is used to invert the Curie depth of the Ross Sea area by the power spectrum method. Finally, according to the inversion results of the Moho depth and Curie depth, the high-precision heat flow distribution in the Ross Sea area is calculated. And compared with the actual measured heat flow value and other inversion results, it shows that this inversion result has obtained a higher resolution. At the same time, the geothermal gradient is calculated by heat flow and thermal conductivity. According to the temperature-pressure equation for formation and storage of gas hydrate, the thickness of the gas hydrate stability zone in the study area was quantitatively calculated.

scholarly journals Adjoint inversion of the thermal structure of Southeastern Australia

2019 ◽  
Vol 219 (3) ◽  
pp. 1648-1659 ◽  
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.

A Bayesian framework for simultaneous determination of susceptibility and magnetic thickness from magnetic data

2021 ◽  
Author(s):  
Jörg Ebbing ◽  
Wolfgang Szwillus ◽  
Yixiati Dilixiati
Keyword(s):  
Heat Flow ◽  
Covariance Function ◽  
Thermal State ◽  
Synthetic Data ◽  
Magnetic Data ◽  
Spatial Behaviour ◽  
Flow Measurements ◽  
Space Domain ◽  
Curie Depth ◽  
Magnetic Inversion

<p>The thickness of the magnetized layer in the crust (or lithosphere) holds valuable information about the thermal state and composition of the lithosphere. Commonly, maps of magnetic thickness are estimated by spectral methods that are applied to individual data windows of the measured magnetic field strength. In each window, the measured power spectrum is fit by a theoretical function which depends on the average magnetic thickness in the window and a ‘fractal’ parameter describing the spatial roughness of the magnetic sources. The limitations of the spectral approach have long been recognized and magnetic thickness inversions are routinely calibrated using heat flow measurements, based on the assumption that magnetic thickness corresponds to Curie depth. However, magnetic spectral thickness determinations remain highly uncertain, underestimate uncertainties, do not properly integrate heat flow measurements into the inversion and fail to address the inherent trade-off between lateral thickness and susceptibility variations.</p><p>We present a linearized Bayesian inversion that works in space domain and addresses many issues of previous depth determination approaches. The ‘fractal’ description used in the spectral approaches translates into a Matérn covariance function in space domain. We use a Matérn covariance function to describe both the spatial behaviour of susceptibility and magnetic thickness. In a first step, the parameters governing the spatial behaviour are estimated from magnetic data and heat flow data using a Bayesian formulation and the Monte-Carlo-Markov-Chain (MCMC) technique. The second step uses the ensemble of parameter solution from MCMC to generate an ensemble of susceptibility and thickness distributions, which are the main output of our approach.</p><p>The newly developed framework is applied to synthetic data at satellite height (300 km) covering an area of 6000 x 6000 km. These tests provide insight into the sensitivity of satellite magnetic data to susceptibility and thickness. Furthermore, they highlight that magnetic inversion benefits greatly from a tight integration of heat flow measurements into the inversion process.</p>

Towards a global lithospheric thermal model

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

<p>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.</p><p>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.   </p><p>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.</p><p>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.  </p><p>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.</p>

The Tibet lithosphere is not all hot

2020 ◽  
Author(s):  
Bing Xia ◽  
Irina Artemieva ◽  
Hans Thybo
Keyword(s):  
Heat Flow ◽  
Large Scale ◽  
North China ◽  
Receiver Function ◽  
Thermal Structure ◽  
Surface Heat ◽  
Moho Depth ◽  
Good Match ◽  
Isostatic Compensation ◽  
Surface Heat Flow

<p>We calculated the thermal lithosphere structure of Tibet and adjacent regions based on the new thermal isostasy method. Moho depth is constrained by the published receiver function results. The calculated surface heat flow in the surrounded Tarim, North China, and Yangtze cratons have a good match with the real measurements of surface heat flow. We recognize the northern Tibet anomaly where has a relatively thin lithosphere with a thermal thickness of <80 km and surface heat flow of >80 - 100 mW/m 2 may cause by the removal of lithospheric mantle and upwelling of asthenosphere. In Lhasa Block, the cold and thick lithosphere (>200 km) with a surface heat flow of 40 - 50 mW/m 2. In the east Tibet, the heterogeneous thermal lithosphere does not follow the widely spread large scale strike-slip faults and suggested that the faults do not cut down to the lithosphere. The surrounding cratons have different thermal lithosphere features. The Tarim and Yangtze cratons show typical cold and thick lithosphere with a lithosphere of >200km and surface heat flow of <50 mW/m2. The western North China Craton has an intermated lithosphere with a thickness of 120-200km and surface heat flow of 45-60 mW/m2. Our result suggested that high and flat Tibet has different isostatic compensation in different blocks. The heterogeneous lithosphere thermal structure of the Tibet suggested that the uplife force drive are difference in Tibet.</p><div> <div> </div> </div>

scholarly journals Constraining the geotherm beneath the British Isles from Bayesian inversion of Curie depth: integrated modelling of magnetic, geothermal, and seismic data

Solid Earth ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 839-850 ◽  
Author(s):  
Ben Mather ◽  
Javier Fullea
Keyword(s):  
Heat Flow ◽  
Flow Field ◽  
Mantle Plume ◽  
Heat Production ◽  
Surface Heat ◽  
Integrated Modelling ◽  
Moho Depth ◽  
British Isles ◽  
Surface Heat Flow ◽  
Curie Depth

Abstract. Curie depth offers a valuable constraint on the thermal structure of the lithosphere, based on its interpretation as the depth to 580 ∘C, but current methods underestimate the range of uncertainty. We formulate the estimation of Curie depth within a Bayesian framework to quantify its uncertainty across the British Isles. Uncertainty increases exponentially with Curie depth but this can be moderated by increasing the size of the spatial window taken from the magnetic anomaly. The choice of window size needed to resolve the magnetic thickness is often ambiguous but, based on our chosen spectral method, we determine that significant gains in precision can be obtained with window sizes 15–30 times larger than the deepest magnetic source. Our Curie depth map of the British Isles includes a combination of window sizes: smaller windows are used where the magnetic base is shallow to resolve small-scale features, and larger window sizes are used where the magnetic base is deep in order to improve precision. On average, the Curie depth increases from Laurentian crust (22.2±5.3 km) to Avalonian crust (31.2±9.2 km). The temperature distribution in the crust, and associated uncertainty, was simulated from the ensemble of Curie depth realizations assigned to a lower thermal boundary condition of a crustal model (sedimentary thickness, Moho depth, heat production, thermal conductivity), constructed from various geophysical and geochemical datasets. The uncertainty in the simulated heat flow field substantially increases from ±10 mW m−2 for shallow Curie depths at ∼15 km to ±80 mW m−2 for Curie depths >40 km. Surface heat flow observations are concordant with the simulated heat flow field except in regions that contain igneous bodies. Heat flow data within large batholiths in the British Isles exceed the simulated heat flow by ∼25 mW m−2 as a result of their high rates of heat production (4–6 µW m−3). Conversely, heat refraction around thermally resistive mafic volcanics and thick sedimentary layers induce a negative heat flow misfit of a similar magnitude. A northward thinning of the lithosphere is supported by shallower Curie depths on the northern side of the Iapetus Suture, which separates Laurentian and Avalonian terranes. Cenozoic volcanism in Northern Britain and Ireland has previously been attributed to a lateral branch of the proto-Icelandic mantle plume. Our results show that high surface heat flow (>90 mW m−2) and shallow Curie depth (∼15 km) occur within the same region, which supports the hypothesis that lithospheric thinning occurred due to the influence of a mantle plume. The fact that the uncertainty is only ±3–8 km in this region demonstrates that Curie depths are more reliable in hotter regions of the crust where the magnetic base is shallow.

scholarly journals Curie depth and heat flow analysis of Ikot Ekpene and environs, Eastern Niger Delta Basin, using airborne magnetic data

2020 ◽  
Vol 8 (2) ◽  
pp. 263
Author(s):  
Uche Iduma ◽  
Stephen Stephen Onyejiuwaka ◽  
Nwokeabia Charity Nkiru
Keyword(s):  
Heat Flow ◽  
Spatial Data ◽  
Niger Delta ◽  
Average Power ◽  
Hydrocarbon Exploration ◽  
Computational Method ◽  
Magnetic Data ◽  
Geothermal Gradients ◽  
Curie Depth ◽  
Niger Delta Basin

Aeromagnetic dataset over Ikot Ekpene and environs, Eastern Niger Delta Basin, was processed to compute the basement depth, Curie isotherm depth, geothermal gradient and heat flow within the area in order to investigate the depth to magnetic sources, geothermal prospect and the hydrocarbon potential of the place. The adopted computational method transformed the spatial data into frequency domain and provided a relationship between radially average power spectrum of the magnetic anomalies and the depths to respective sources.  The results of the analysis showed that the depths to centroids and top boundaries range from 7.84 to 13.38 km and 0.233 to 0.459 km respectively. Curie depths within the basin undulate and vary between 15.42 and 26.49 km. The geothermal gradients range between 20.758 and 35.649 ⁰C/km while the corresponding heat flow is about 51.896 mWm⁻² within east of Ikono, north of Mbak and west of Abak Areas and 89.124 mWm⁻² within Amawum, Ndoro, Isiala, Ogbuebule and east of Uyo Areas. Based on the computed sedimentary thicknesses, high geothermal gradients and delineated major faults and fractures which could serve as migratory pathway for hydrocarbon or hydrothermal fluid, some parts of the study area have been demarcated for geothermal prospect and detail hydrocarbon exploration.  

scholarly journals Constraining the geotherm beneath the British Isles from Bayesian inversion of Curie depth: Integrated modelling of magnetic, geothermal and seismic data

2019 ◽  
Author(s):  
Ben Mather ◽  
Javier Fullea
Keyword(s):  
Heat Flow ◽  
Flow Field ◽  
Mantle Plume ◽  
Heat Production ◽  
Surface Heat ◽  
Integrated Modelling ◽  
Moho Depth ◽  
British Isles ◽  
Surface Heat Flow ◽  
Curie Depth

Abstract. Curie depth offers a valuable constraint on the thermal structure of the lithosphere, based on its interpretation as the depth to 580 °C, but current methods underestimate the range of uncertainty. We formulate the estimation of Curie depth within a Bayesian framework to quantify its uncertainty across the British Isles. Uncertainty increases exponentially with Curie depth but this can be moderated by increasing the size of the spatial window taken from the magnetic anomaly. The choice of window size needed to resolve the magnetic thickness is often ambiguous, but based on our chosen spectral method, we determine that significant gains in precision can be obtained with windows sizes 15–30 times larger than the deepest magnetic source. Our Curie depth map of the British Isles includes a combination of window sizes: smaller windows are used where the magnetic base is shallow to resolve small-scale features, and larger window sizes are used where the magnetic base is deep in order to improve precision. On average, the Curie depth increases from Laurentian crust (22.2 ± 5.3 km) to Avalonian crust (31.2 ± 9.2 km). The temperature distribution in the crust, and associated uncertainty, was simulated from the ensemble of Curie depth realisations assigned to a lower thermal boundary condition of a crustal model (sedimentary thickness, Moho depth, heat production, thermal conductivity), constructed from various geophysical and geochemical data sets. The uncertainty of the simulated heat flow field substantially increases from ± 10 mW m−2 for shallow Curie depths ~ 15 km to ± 80 mW m−2 for Curie depths > 40 km. Surface heat flow observations are concordant with the simulated heat flow field except in regions that contain igneous bodies. Heat flow data within large batholiths in the British Isles exceed the simulated heat flow by ∼ 25 mW m−2 as a result of their high rates of heat production (4–6 μW m−3). Conversely, heat refraction around thermally resistive mafic volcanics and thick sedimentary layers induce a negative heat flow misfit of a similar magnitude. A northward thinning of the lithosphere is supported by shallower Curie depths on the northern side of the Iapetus Suture, which separates Laurentian and Avalonian terranes. Cenozoic volcanism in Northern Britain and Ireland has previously been attributed to a lateral branch of the proto-Icelandic mantle plume. Our results show that high surface heat flow (> 90 mW m−2) and shallow Curie depth (∼ 15 km) occur within the same region, which supports the hypothesis that lithospheric thinning occurred due to the influence of a mantle plume. That the uncertainty is only ± 3–8 km in this region, demonstrates that Curie depths are more reliable in hotter regions of the crust where the magnetic base is shallow.

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