scholarly journals A geothermal application for GOCE satellite gravity data: modelling the crustal heat production and lithospheric temperature field in Central Europe

2019 ◽  
Vol 219 (2) ◽  
pp. 1008-1031 ◽  
Author(s):  
A Pastorutti ◽  
C Braitenberg
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Heat Transport ◽  
Gravity Model ◽  
Heat Production ◽  
Crustal Thickness ◽  
Gravity Models ◽  
Conductive Heat ◽  
Flow Measurements ◽  
Global Gravity Models

SUMMARY Since the completion of the Gravity field and steady-state Ocean Circulation Explorer mission (GOCE), global gravity models of uniform quality and coverage are available. We investigate their potential of being useful tools for estimating the thermal structure of the continental lithosphere, through simulation and real-data test in Central-Eastern Europe across the Trans-European Suture Zone. Heat flow, measured near the Earth surface, is the result of the superposition of a complex set of contributions, one of them being the heat production occurring in the crust. The crust is enriched in radioactive elements respect to the underlying mantle and crustal thickness is an essential parameter in isolating the thermal contribution of the crust. Obtaining reliable estimates of crustal thickness through inversion of GOCE-derived gravity models has already proven feasible, especially when weak constraints from other observables are introduced. We test a way to integrate this in a geothermal framework, building a 3-D, steady state, solid Earth conductive heat transport model, from the lithosphere–asthenosphere boundary to the surface. This thermal model is coupled with a crust-mantle boundary depth resulting from inverse modelling, after correcting the gravity model for the effects of topography, far-field isostatic roots and sediments. We employ a mixed space- and spectral-domain based forward modelling strategy to ensure full spectral coherency between the limited spectral content of the gravity model and the reductions. Deviations from a direct crustal thickness to crustal heat production relationship are accommodated using a subsequent substitution scheme, constrained by surface heat flow measurements, where available. The result is a 3-D model of the lithosphere characterised in temperature, radiogenic heat and thermal conductivity. It provides added information respect to the lithospheric structure and sparse heat flow measurements alone, revealing a satisfactory coherence with the geological features in the area and their controlling effect on the conductive heat transport.

High Performance Dirichlet Parametrization Through Triangular Be´zier Surface Interpolation for Deformation of CAE Meshes

2007 ◽  
Author(s):  
Yifan Chen ◽  
Basavaraj Tonshal
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Heat Flow ◽  
Surface Deformation ◽  
Conductive Heat ◽  
3D Mesh ◽  
State Heat ◽  
Multiple User ◽  
Steady State Heat ◽  
Blending Function

We present a method that extends the physics-based Dirichlet parametrization for applications concerning deformation of CAE meshes. Developed for a geometric surface feature framework called Direct Surface Manipulation, Dirichlet parametrization offers a number of operational flexibilities, such as its ability to use a single polynomial blending function to control deformation of a surface region subject to multiple user-specified displacement conditions. Dirichlet parametrization considers the domain of deformation as 2D steady-state conductive heat flow and solves for unique temperature distribution over the deformation domain using the finite element analysis (FEA) method. The result is used for evaluation of the polynomial blending function during surface deformation. The original Dirichlet parametrization, however, suffers from two limitations. First, because the 2D FEA mesh required for solving the steady-state heat transfer problem is obtained by directly projecting the affected 3D mesh onto a plane (deformation domain), both parameterization quality and performance depend on the structural characteristics of the projected 2D mesh (type of elements, node density, etc.) rather than geometrical characteristics of the deformation domain. Second, projecting a 3D mesh to create a 2D FEA mesh can be problematic when multiple areas of a 3D mesh are projected on the plane and overlap each other. Improvement techniques are presented in this paper. Instead of projecting the 3D mesh onto the plane to form the 2D FEA mesh, an auxiliary mesh is created based on geometric characteristics of the deformation domain, such as its size and boundary shape. Delaunay triangulation with an area constraint is applied in meshing the deformation region. The result is used as the 2D FEA mesh for solving the steady-state heat flow problem using the finite element method. Temperature of an affected node of the 3D mesh is obtained by interpolation in two steps. First, the node is projected onto the 2D FEA mesh, and the intersecting triangle is found. Second, the temperature at the intersection is obtained by interpolating the temperatures at the three vertices of the triangle using the cubic, triangular Be´zier interpolant. The result is equated to the temperature of the node. The use of an auxiliary mesh eliminated mesh-dependency for Dirichlet parametrization. The use of triangular cubic Be´zier interpolant results in better continuity condition of the interpolating surface between adjacent elements than linear interpolation. This allows us to employ a moderate size FEA mesh for computational efficiency. Implementation of the method is discussed and results are demonstrated.

Temperature structure of the Andean subduction zone as derived from the 3D geometry of crustal and upper mantle discontinuities

2020 ◽  
Author(s):  
Andres Tassara ◽  
Joaquín Julve ◽  
Iñigo Echeverría ◽  
Ingo Stotz
Keyword(s):  
Heat Flow ◽  
Heat Production ◽  
Thermal Structure ◽  
Surface Heat ◽  
Thermal Parameters ◽  
Continental Lithosphere ◽  
Flow Measurements ◽  
Study Region ◽  
Surface Heat Flow ◽  
Input Model

<p>The distribution of temperature inside active continental margins plays a fundamental role on regulating first order geodynamic processes as the isostatic balance, rheologic behavior of crust and mantle, magmagenesis, volcanism and seismogenesis. In spite of these major implications, well-constrained 3D thermal models are known for few regions of the world (Europe, Western USA, China) where large geophysical databases have been integrated into compositional and structural models of crust and lithospheric mantle from which a thermal model is derived. Here we present a three-dimensional representation of the distribution of temperature underneath the Andean active margin of South America (10°-45°S) that is based on a geophysically-constrained model for the geometry of the subducted slab, continental lithosphere-asthenosphere boundary (LAB), Moho discontinuity and an intracrustal discontinuity (ICD). This input model was constructed by forward modelling the satellite gravity anomaly under the constraint of most of the seismic information published for this region. We use analytical expressions of 1D conductive continental geotherms with adequate boundary conditions that consider the compositional stratification of crust and mantle included in the input model, and the advective thermal effect of slab subduction. The 1D geotherms are assembled into a 3D volume defining the thermal structure of the study region. We test the influence of several thermal parameters and structural configurations of the Andean lithosphere by comparing the resulting surface heat flow distribution of these different models against a database containing heat flow measurements that we compile from the literature. Our results show that the thermal structure and derived surface heat flow is dominantly controlled by the geometry of the thermal boundary layer at the base of the lithosphere, i.e. the slab upper surface below the forearc and LAB inland. Variations on the modeled configuration of the continental lithosphere (i.e. the way on which the geometry of the continental Moho and ICD are considered into the definition of a space-variable thermal conductivity or the length scale for radiogenic heat production) have an effect on surface heat flow that is lower than the average uncertainty of the measurements and therefore can be considered as second-order. The simplicity of our analytical approach allows us to compute hundreds of different models in order to test the sensitivity of results to changes on thermal parameters (conductivity, heat production, mantle potential temperature, etc), which provides a tool for discussing their possible range of values in the context of a subduction margin. We will also show how variations of these models impact on the Moho temperature and therefore in the expected mechanical behavior of crust and mantle in this geotectonic context</p>

A lightweight thermal modelling tool for physics-based continental heat flow interpolation

2020 ◽  
Author(s):  
Alberto Pastorutti ◽  
Carla Braitenberg
Keyword(s):  
Temperature Field ◽  
Heat Flow ◽  
Central Europe ◽  
Heat Production ◽  
Surface Heat ◽  
Gravity Models ◽  
Forward Modelling ◽  
Flow Data ◽  
Satellite Gravity ◽  
Surface Heat Flow

<p><em>Both energy applications, such as assessing one of the controlling factors of conductive geothermal plays, and geodynamics modelling, are influenced by the large uncertainties arising from uneven sampling of the direct observable of the Earth's thermal state, surface heat flow. Heterogeneity in structure and composition of the continental lithosphere complicate the temperature field even in stable provinces in thermal equilibrium. The measurements deviate from what simple relationships with geological and geophysical data predict, requiring more sophisticated schemes such as those based on multivariate inversion (e.g. Mather et al. 2018) and geostatistics (e.g. the similarity method employed by Lucazeau, 2019).</em></p><p><em>Recently, we aimed at assessing the performance of satellite-gravity-constrained modelling of surface heat flow [1], with the aim of employing the unparalleled spatial uniformity of global gravity models in the fill-in of sparsely sampled surface heat flow data. The model we obtained, in a test area in Central Europe, provided additional information on the lithospheric structure and revealed a satisfactory coherence with the geological features in the area and their controlling effect on the conductive heat transport. That test was based on a fit of radioactive heat production to available heat flow data, based on a misfit linearization and substitution strategy, which we have shown to be independently consistent with available heat production relationships (e.g. Hasterok and Webb, 2017). Furthermore, model validation techniques provide additional metrics on the predictability in areas devoid of heat flow measurements.</em></p><p><em>T</em><em>o reach those objectives, we developed a finite-difference based solver for the heat equation in conductive, stable lithosphere, relying on the assumption of steady state, 3-D heat conduction from the thermal base of the lithosphere to surface. It allows for non-homogeneous heat production and thermal conductivity, and non-flat upper and bottom boundaries. Concurrent joint forward modelling of the gravity field is also possible.<br>Through compromise between complexity and approximation, it was designed favouring easy and fast forward modelling, such as in assessing parameter sensitivity and performing grid searches or parameter fitting. Geological models and parameters can be defined using an user-friendly plain text layer-wise definition, which is then turned into a volume, on a rectangular mesh.<br>Computational requirements are lean: a 75 × 75 × 104 node model such as the one employed in [1] can be forward-modelled on an ordinary workstation in 135 seconds. A direct solver is employed to solve the FD system of linear equations: the Matlab built-in Cholesky decomposition for sparse arrays (Davis, 2006).</em></p><p><em>Albeit initially developed as an ad-hoc tool for a proof of concept, its ease of use and versatility suggest its potential in other applications. We therefore present the solver and the accompanying tool set, both openly available, along with a set of promising examples.<br><br>[1] Pastorutti, A., Braitenberg, C. (2019) "A geothermal application for GOCE satellite gravity data: modelling the crustal heat production and lithospheric temperature field in Central Europe." Geophysical Journal International, doi:10.1093/gji/ggz344</em></p>

Continuation of heat flow data: A method to construct isotherms in geothermal areas

Geophysics ◽  
1981 ◽  
Vol 46 (12) ◽  
pp. 1732-1744 ◽  
Author(s):  
Charles A. Brott ◽  
David D. Blackwell ◽  
Paul Morgan
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Surface Heat ◽  
Point Sources ◽  
Conductive Heat ◽  
Geothermal Systems ◽  
Flow Data ◽  
Additional Tool ◽  
Surface Heat Flow ◽  
Conductive Heat Flow

A continuation technique for conductive heat flow in a homogeneous isotropic medium is presented which utilizes observe surface heat flow data. The technique uses equivalent point sources and is developed for transient or steady‐state conductive heat flow problems for a homogeneons half‐space with plane surface and a surface with topographic relief. The technique is demonstrated by comparison with a steady‐state fault model and the terrain correction problem; it is also compared to observed heat flow data in two geothermal areas (Marysville, Montana, and East Mesa, Imperial Valley, California). Calculated subsurface temperature distributions are compared to analytical models and the results of geophysical studies in deep drillholes in geothermal systems. Even in geothermal systems, where convection is involved in the heat transfer, the boundaries of the “reservoir” associated with the convective system can be treated as a boundary condition and the depth and shape of this boundary can be calculated, since many geothermal systems are controlled by permeability barriers. These barriers may either be due to the natural development of a trap or to self‐sealing. Continuation of surface heat flow data is a useful technique in the initial evaluation of geothermal resources as well as an additional tool in the interpretation of regional heat‐flow data.

Heat flow in a back-arc environment: Intermontane and Omineca Crystalline belts, southern Canadian Cordillera

1984 ◽  
Vol 21 (6) ◽  
pp. 715-726 ◽  
Author(s):  
Earl E. Davis ◽  
Trevor J. Lewis
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Thermal Structure ◽  
Canadian Cordillera ◽  
Flow Measurements ◽  
Thermal Event ◽  
South Central ◽  
Back Arc ◽  
Glacial Climate ◽  
Reduced Heat Flow

A suite of 20 heat flow measurements has been completed across the Intermontane and Omineca Crystalline belts in south-central British Columbia at about 50°N. Values along the 200 km line are high (83 mW m−2, corrected for Pleistocene glacial climate; reduced heat flow is 67 mW m−2) and uniform (standard deviation = ± 10%). There appears to be no difference in the thermal structure of the two geologic belts. Two sources of heat are considered to explain the level of heat flow observed: a discrete thermal event in the Eocene, and a steady-state supply of heat maintained in the back-arc location by asthenospheric flow caused by nearby subduction. Both can account equally well for the elevated heat flow observed. However, in light of seismic, magnetic, electrical, and flexural data that suggest that the lithosphere may be as thin as 30–40 km, it is concluded that a steady supply of heat must exist since this thickness is much less than the thickness of lithosphere that would be present 50 Ma after even a major thermal event.

The thermal structure of the central Nova Scotia Slope (eastern Canada): seafloor heat flow and thermal maturation models

2017 ◽  
Vol 54 (2) ◽  
pp. 146-162 ◽  
Author(s):  
Eric Negulic ◽  
Keith E. Louden
Keyword(s):  
Heat Flow ◽  
Thermal Structure ◽  
Conductive Heat ◽  
Borehole Data ◽  
Eastern Canada ◽  
Flow Measurements ◽  
Seismic Reflection Data ◽  
Radiogenic Heat ◽  
Reflection Data ◽  
Hydrocarbon Maturation

The thermal history and maturation potential of the central Scotian Slope is constrained using a combination of 47 recently acquired seafloor heat flow measurements, two-dimensional (2D) seismic reflection data, available well data, simple lithospheric rift models, and thermal and petroleum systems modelling. Consistent heat flow values of 41–46 mW·m−2 were measured seaward of the salt diapiric province and across the slope away from the influence of salt structures. Significant but highly variable increases in heat flow were measured for stations overlying salt diapiric structures, reaching values upwards of 72 mW·m−2. Simple models of conductive heat transfer with static salt geometries constrained from reflection profiles indicate that two of the four models fit the data, whereas two indicate much higher values suggestive of additional, convective effects. Dynamic 2D thermal models were developed to incorporate the effects of lithospheric rifting, crustal stretching, and radiogenic heat production in the sediment and basement. These models help constrain the hydrocarbon maturation potential of the central Scotian Slope, where deep borehole data are lacking. Our results suggest that a potential Late Jurassic source rock interval rests primarily within the late oil window and that salt structures act primarily to reduce maturation in the adjacent deep sediment layers.

scholarly journals Comparison and testing of GOCE global gravity models in Central Europe

2011 ◽  
Vol 1 (4) ◽  
pp. 333-347 ◽  
Author(s):  
Juraj Janák ◽  
Martin Pitoňák
Keyword(s):  
Reference Frame ◽  
Gravity Model ◽  
Central Europe ◽  
Terrestrial Reference Frame ◽  
Gravity Models ◽  
Direct Solution ◽  
Model Solutions ◽  
Global Gravity ◽  
Global Gravity Models ◽  
Global Gravity Model

Comparison and testing of GOCE global gravity models in Central EuropeThree different global gravity model solutions have been released by the European GOCE Gravity Consortium: a direct solution, a time-wise solution and a space-wise solution. To date, two releases of each solution have been issued. Each of these solutions has specific positives and weaknesses. This paper shows and analyzes the differences between each solution in Central Europe by means of comparison with respect to the EGM2008 and GOCO02S global gravity models. In order to make an independent comparison, the global GOCE models are tested by the SKTRF (Slovak Terrestrial Reference Frame) network in Slovakia.

scholarly journals Evolution of heat flow, hydrothermal circulation and permeability on the young southern flank of the Costa Rica Rift

2019 ◽  
Vol 220 (1) ◽  
pp. 278-295 ◽  
Author(s):  
Kannikha Parameswari Kolandaivelu ◽  
Robert N Harris ◽  
Robert P Lowell ◽  
Adam H Robinson ◽  
Dean J Wilson ◽  
...  
Keyword(s):  
Costa Rica ◽  
Heat Flow ◽  
Heat Loss ◽  
Seismic Velocity ◽  
Conductive Heat ◽  
Hydrothermal Circulation ◽  
Flow Measurements ◽  
Conductive Heat Flow ◽  
The Mean ◽  
Southern Flank

SUMMARY We analyse 67 new conductive heat-flow measurements on the southern flank of the Costa Rica Rift (CRR). Heat-flow measurements cover five sites ranging in oceanic crustal age between approximately 1.6 and 5.7 Ma, and are co-located with a high-resolution multichannel seismic line that extends from slightly north of the first heat-flow site (1.6 Ma) to beyond ODP Hole 504B in 6.9 Ma crust. For the five heat-flow sites, the mean observed conductive heat flow is ≈85 mW m−2. This value is approximately 30 per cent of the mean lithospheric heat flux expected from a half-space conductive cooling model, indicating that hydrothermal processes account for about 70 per cent of the heat loss. The advective heat loss fraction varies from site to site and is explained by a combination of outcrop to outcrop circulation through exposed basement outcrops and discharge through faults. Supercritical convection in Layer 2A extrusives occurs between 1.6 and 3.5 Ma, and flow through a thinly sedimented basement high occurs at 4.6 Ma. Advective heat loss diminishes rapidly between ≈4.5 and ≈5.7 Ma, which contrasts with plate cooling reference models that predict a significant deficit in conductive heat flow up to ages ≈65 ± 10 Ma. At ≈5.7 Ma the CRR topography is buried under sediment with an average thickness of ≈150 m, and hydrothermal circulation in the basement becomes subcritical or perhaps marginally critical. The absence of significant advective heat loss at ≈5.7 Ma at the CRR is thus a function of both burial of basement exposure under the sediment load and a reduction in basement permeability that possibly occurs as a result of mineral precipitation and original permeability at the time of formation. Permeability is a non-monotonic function of age along the southern flank of the CRR, in general agreement with seismic velocity tomography interpretations that reflect variations in the degree of ridge-axis magma supply and tectonic extension. Hydrothermal circulation in the young oceanic crust at the southern flank of CRR is affected by the interplay and complex interconnectedness of variations in permeability, sediment thickness, topographical structure, and tectonic and magmatic activities with age.

Sign in / Sign up

Export Citation Format

Share Document