Lateral Temperature Variations Research Articles

A preliminary assessment of regional CO2 storage potential in the onshore northern Perth Basin

The Geological Survey of Western Australia (GSWA) is creating a new carbon dioxide (CO2) geological storage atlas for Western Australia. The atlas will incorporate the latest state-wide datasets to provide a regional assessment of the potential for CO2 sequestration across the Perth, Southern Carnarvon, Northern Carnarvon (onshore and State waters), Canning and Officer basins. Multi-1D modelling of subsurface temperature in the northern Perth Basin incorporates newly collated temperature data, updated regional depth maps, and stratigraphic revisions. This modelling captures lateral subsurface temperature variations that are incorporated into isothermal depth and temperature maps identifying reservoir units within the optimum temperature–pressure window for CO2 storage. Isopach maps of associated sealing units indicate where they are of adequate thickness to contain CO2. Modelled present-day temperature maps of seven key reservoir units reveal promising CO2 storage prospectivity, with all postulated reservoir units having significant extents within optimum CO2 storage temperature and pressure ranges. Whereas older reservoir units are prospective for CO2 storage towards the margins of the basin, younger reservoir units in the shallower part of the succession are only prospective in or near the Dandaragan Trough, the deepest part of the basin. The critical upper temperature limit of 31.1°C is shallower in the north and west of the basin, where the modelled geothermal gradient is higher. All state-wide raw and interpreted datasets including temperature and depth maps will be published and available for download on the GSWA Western Australian Petroleum and Geothermal Information Management System website.

Receiver Function Analysis Reveals Lateral Variations in Temperature and Water Content in the Mantle Transition Zone Beneath Eastern North America

AbstractUsing recently collected high‐resolution seismic data along a dense linear transect across Ohio, West Virginia, and Virginia (called Mid‐Atlantic Geophysical Integrative Collaboration (MAGIC) profile), we analyze P‐to‐S receiver functions to investigate the undulations of the mantle transition zone (MTZ) discontinuities (410‐ and 660‐km) beneath the central Appalachian region. Our results incorporating the effects of local crustal and mantle structures suggest shallowing of both the 410‐ and the 660‐km discontinuities from the northwest (inland) to the southeast (coast) along MAGIC profile. Hydro‐thermal upwelling beneath the eastern U.S. coastal plain due to a hydrated MTZ and hot upwelling return flow associated with the descending lower mantle Farallon slab is consistent with our observations of MTZ structure considering 3D velocity heterogeneity. The inferred hydrous hot upwelling rising into the upper mantle may trigger dehydration melting atop the 410‐km discontinuity, which may help to explain the presence of a low velocity upper mantle anomaly beneath the region today.

Convection of snow: when and why does it happen?

Convection of water vapor in snowpacks is supposed to have a major impact on snow density and microstructure profiles with strong implications for the thermal regime and snow stability. However, the process has never been directly measured and only recently been simulated for idealized conditions. The analysis suggests that natural convection is not likely to happen in typical horizontally homogeneous polar or Alpine snow covers. This paper studies the potential impact of heterogeneity induced, e.g., by shrubs on convection of water vapor. We find that natural convection triggered by buoyancy occurs even with sub-critical Rayleigh number as low as 5 due to heterogeneity in snow density. This leads to complementing contributions of diffusive and convective flux divergence on snow density changes. The combined effect of diffusion and convection helps to generate the often-observed low density foot and high-density top of, e.g., Arctic snowpacks. The strongest effect of convection is not for very thin or thick snow covers but for snow covers with thickness in the order of 0.5 m. This scale facilitates the development of convection cells. Further work should address the additional effects of sub-snow lateral temperature variations and assess the effect of convective vapor fluxes on snow microstructure.

Effect of lateral straggle parameter on Hetero Junction Dual Gate Vertical TFET

In this Article, the effects of lateral straggle parameter variation and Temperature variation have been investigated on Hetero Junction Dual Gate Vertical TFET. Although the TFET is a viable alternative to the MOSFET, the performance of the device is dependent on the accuracy of the fabrication process. The ion implantation technology is applied for the regions of Source/Drain during the fabrication process to realise the variation in tilt angle. As a result of this process, Dopants from the source and drain areas are extended into the channel, which has a substantial impact on the device's performance. The impact of lateral straggle is implemented by considering it in the TCAD simulation. The performance of the Hetero Junction Dual Gate Vertical TFET is examined by the 0–6 nm variation in the lateral straggle parameter. When the lateral straggling parameter (σ) is set at higher values, the greater electron tunnelling rate results in an increase in the on current. Various parameters such as intrinsic capacitances like gate to source capacitance (Cgs), gate to drain capacitance (Cgd), and total capacitance (Cgg), gate charge, electric field, surface potential, transconductance are studied in Hetero Junction Dual Gate Vertical TFET for various σ values.

Mantle thermochemical variations beneath the continental United States through petrologic interpretation of seismic tomography

The continental lithospheric mantle plays an essential role in stabilizing continents over long geological time scales. Quantifying spatial variations in thermal and compositional properties of the mantle lithosphere is crucial to understanding its formation and its impact on continental stability; however, our understanding of these variations remains limited. Here we apply the Whole-rock Interpretive Seismic Toolbox For Ultramafic Lithologies (WISTFUL) to estimate thermal, compositional, and density variations in the continental mantle beneath the contiguous United States from MITPS_20, a joint body and surface wave tomographic inversion for Vp and Vs with high resolution in the shallow mantle (60–100 km). Our analysis shows lateral variations in temperature beneath the continental United States of up to 800–900°C at 60, 80, and 100 km depth. East of the Rocky Mountains, the mantle lithosphere is generally cold (350–850°C at 60 km), with higher temperatures (up to 1000°C at 60 km) along the Atlantic coastal margin. By contrast, the mantle lithosphere west of the Rocky Mountains is hot (typically >1000°C at 60 km, >1200°C at 80–100 km), with the highest temperatures beneath Holocene volcanoes. In agreement with previous work, we find that the chemical depletion predicted by WISTFUL does not fully offset the density difference due to temperature. Extending our results using Rayleigh-Taylor instability analysis, implies the lithosphere below the United States could be undergoing oscillatory convection, in which cooling, densification, and sinking of a chemically buoyant layer alternates with reheating and rising of that layer.

Geodynamic predictions of seismic structure and discontinuity topography of the mantle transition zone

SUMMARYThe mantle transition zone (TZ) is expected to influence vertical mass flow between upper and lower mantle as it hosts a complex set of mineral phase transitions and an increase in viscosity with depth. Still, neither its seismic structure nor its dynamic effects have conclusively been constrained. The seismic discontinuities at around 410 and 660 km depth (‘410’ and ‘660’) are classically associated with phase transitions between olivine polymorphs, the pressure of which is modulated by lateral temperature variations. Resulting discontinuity topography is seismically visible and can thus potentially provide insight on temperature and phase composition at depth. Besides the olivine phase changes, the disassociation of garnet may additionally impact the 660 at higher temperatures. However, the volume of material affected by this garnet transition and its dynamic implications have not yet been quantified. This study presents hypothetical realizations of TZ seismic structure and major discontinuities based on the temperature field of a published 3-D mantle circulation model for a range of relevant mineralogies, including pyrolite and mechanical mixtures (MM). Systematic analysis of these models provides a framework for dynamically informed interpretations of seismic observations and gives insights into the potential dynamic behaviour of the TZ. Using our geodynamic-mineralogical approach we can identify which phase transitions induce specific topographic features of 410 and 660 and quantify their relative impact. Areal proportions of the garnet transition at the 660 are ∼3 and ∼1 per cent for pyrolite and MM, respectively. This proportion could be significantly higher (up to ∼39 per cent) in a hotter mantle for pyrolite, but remains low (<2 per cent) for MM. In pyrolite, both slabs and plumes are found to depress the 660—with average deflections of 14 and 6 km, respectively—due to the influence of garnet at high temperatures indicating its complex dynamic effects on mantle upwellings. Pronounced differences in model characteristics for pyrolite and MM, particularly their relative garnet proportions and associated topography features, could serve to discriminate between the two scenarios in Earth.

On convective instabilities in a rotating fluid with stably stratified layer and thermally heterogeneous boundary

The onset of convection in a rotating plane layer due to a vertical temperature gradient is studied in this paper. The background stratification is modulated by lateral temperature variations and stable stratification aimed at understating the Earth's outer core convection subject to thermal core–mantle interaction. At the top boundary, sinusoidal and Gaussian temperature variations are imposed apart from the reference case of isothermal condition used in the classical Rayleigh–Benard convection. The additional modulating conditions break the top–bottom flow symmetry leading to flow localization and asymmetry that exhibit modified temporal dynamics unlike that of the classical Rayleigh–Benard cells. The threshold for convection is lowered with flows occurring in surplus heat flux regions caused by the imposed conditions. Despite flow suppression in the stable layer, rapid rotation favors the penetration of convection rolls with smaller wavelengths. The lateral variations in temperature imposed at the top boundary enhance such axial penetration with a laterally varying penetrative extent resulting in a modified clustered flow structure unlike the reference case. With both modulating conditions imposed, the onset of overstable modes is favored for low Prandtl numbers, a regime which is relevant to the Earth's core conditions. With rapid rotation, a novel mode of traveling wave instability occurs at the onset of convection, the propagation direction of which is controlled by the lateral temperature gradients at the top boundary. The onset of oscillatory modes is suppressed by the imposition of the modulating conditions indicated by the significant lowering of the transition Prandtl number.

Topographic response to ocean heat flux anomaly on the icy moons of Jupiter and Saturn

Recent studies of ocean dynamics suggest that the long-wavelength topography of some icy moons may reflect the phase transitions (melting/freezing) at the interface between the ice shell and the water ocean. Despite the obvious importance of phase changes in the evolution of icy moons, very little is known about how these processes influence their shape, gravity and near-surface stress. Here we address this issue by performing a series of numerical experiments in which we explore the thermo-mechanical response of an ice layer to heat flux variations imposed at the bottom (phase) boundary. We assume that the heat flux from the ocean consists of two components: the heat flux originating in the deep ocean and associated with the global ocean circulation, and the heat flux due to the flow of water generated by variations in the melting temperature along the deformed ice–water interface. The effect of salinity on the heat flux from the ocean is neglected. We demonstrate that the mass exchange between the ocean and the ice layer is a natural consequence of the ice–water phase transition and it occurs in both convection and conduction modes, regardless of whether the system is in equilibrium or not. The magnitude of the heat-flux induced topography strongly depends on the viscosity of ice and the flow of water controlled by the melting temperature. When heat transfer in the ice shell occurs by convection, the surface topography is dominated by small-scale convective features varying in time and its large-scale component does not exceed 10 m. When the viscosity of the ice shell is high (≳1016 Pas) and the heat is transferred by conduction, the topography is negatively correlated with the heat flux from the ocean and its amplitude increases with increasing viscosity. Topographic amplitudes comparable to those observed on Titan, Enceladus and Dione are obtained only if the water flow associated with lateral variations in the melting temperature is neglected. This suggests that this flow may be too weak to reduce the variations in ice shell thickness and the motion of water along the phase boundary is more likely to be controlled by other factors, such as variations in salinity and the presence of non-ice material. In addition, we show that the standard formulation of Airy isostasy can lead to an error of 5%–15% in determining the variations in ice thickness and we propose a new formulation that takes into account the effect of thermal expansion.

Response to Comment on "Discovery of davemaoite, CaSiO3-perovskite, as a mineral from the lower mantle".

Walter et al. issue a number of critical comments on our report about the discovery of davemaoite to the end that they believe to show that our results do not provide compelling evidence for the presence of davemaoite in the type specimen and that the hosting diamond had formed in the lithosphere. Their claim is based on a misinterpretation of the diffraction data contained in the paper, an insufficient analysis of the compositional data that disregards the three-dimensional distribution of inclusions, and the arbitrary assumption that Earth's mantle shows no lateral variations in temperature, inconsistent with state-of-the-art assessments of mantle temperature variations and with their own published results.

WINTERC-G: mapping the upper mantle thermochemical heterogeneity from coupled geophysical–petrological inversion of seismic waveforms, heat flow, surface elevation and gravity satellite data

SUMMARYWe present a new global thermochemical model of the lithosphere and underlying upper mantle constrained by state of the art seismic waveform inversion, satellite gravity (geoid and gravity anomalies and gradiometric measurements from ESA's GOCE mission), surface elevation and heat flow data: WINTERC-G. The model is based upon an integrated geophysical–petrological approach where seismic velocities and density in the mantle are computed within a thermodynamically self-consistent framework, allowing for a direct parametrization in terms of the temperature and composition variables. The complementary sensitivities of the data sets allow us to constrain the geometry of the lithosphere–asthenosphere boundary, to separate thermal and compositional anomalies in the mantle, and to obtain a proxy for dynamic surface topography. At long spatial wavelengths, our model is generally consistent with previous seismic (or seismically derived) global models and earlier integrated studies incorporating surface wave data at lower lateral resolution. At finer scales, the temperature, composition and density distributions in WINTERC-G offer a new state of the art image at a high resolution globally (225 km average interknot spacing). Our model shows that the deepest lithosphere–asthenosphere boundary is associated with cratons and, also, some tectonically active areas (Andes, Persian Gulf). Among cratons we identify considerable differences in temperature and composition. The North American and Siberian Cratons are thick (>260 km) and compositionally refractory, whereas the Sino-Korean, Aldan and Tanzanian Cratons have a thinner, fertile lithosphere, similar to younger continental lithosphere elsewhere. WINTERC-G shows progressive thickening of oceanic lithosphere with age, but with significant regional differences: the lithospheric mantle beneath the Atlantic and Indian Oceans is, on average, colder, more fertile and denser than that beneath the Pacific Ocean. Our results suggest that the composition, temperature and density of the oceanic mantle lithosphere are related to the spreading rate for the rates up to 50–60 mm yr–1: the lower spreading rate, the higher the mantle fertility and density, and the lower the temperature. At greater spreading rates, the relationship disappears. The 1-D radial average of WINTERC-G displays a mantle geothermal gradient of 0.55–0.6 K km–1 and a potential temperature of 1300–1320 °C for depths >200 km. At the top of the mantle transition zone the amplitude of the maximum lateral temperature variations (cratons versus hotspots) is about 120 K. The isostatic residual topography values, a proxy for dynamic topography, are large (>1 km) mostly in active subduction settings. The residual isostatic bathymetry from WINTERC-G is remarkably similar to the pattern independently determined based on oceanic crustal data compilations. The amplitude of the continental residual topography is relatively large and positive (>600 m) in the East European Craton, Greenland, and the Andes and Himalayas. By contrast, central Asia, most of Antarctica, southern South America and, to a lesser extent, central Africa are characterized by negative residual topography values (>–400 m). Our results show that a substantial part of the topography signal previously identified as residual (or dynamic) is accounted for, isostatically, by lithospheric density variations.

Liquid Flow Forced Convection in Rectangular Microchannels With Nonuniform Heating: Toward Analytical Modeling of Hotspots

Abstract The heat generated by microprocessors has an extremely nonuniform spatial distribution with hotspots that have heat fluxes several times larger than the background flux. Hence, for an accurate design of microchannel heat sinks used for cooling of micro-electronic devices, models are required that can take such a nonuniform distribution of wall heat flux into account. In this study, analytical solutions are obtained for hydrodynamically fully developed but thermally developing mixed electro-osmotic and pressure-driven (PD) flow in a rectangular microchannel with a peripherally uniform but axially nonuniform distribution of the wall heat flux. It is assumed that the heat flux is applied over a finite length, to mimic a physically more realistic situation, and the Péclet number is small so that lateral temperature variations are negligible as compared to the axial variations of temperature. By comparing the results with those of full numerical simulations for exponential (EHF), sinusoidal (SHF), and stepwise (STHF) distributions of wall heat flux, it is demonstrated that the solutions obtained are accurate up to a Péclet number of 10. Fortunately, this value is larger than the maximum Péclet number of electro-osmotic microflows. Furthermore, it is shown that smoother distributions of wall heat flux give rise to higher heat transfer rates. The model developed in this study can pave the way for modeling of hotspots in more complicated microfluidic devices.

Methodology for High-Accuracy Infrared Calibration in Environments with Through-Wall Heat Flux

This paper describes a new method for accurate in situ infrared (IR) calibration in environments with significant through-wall heat flux and surface temperature non-uniformity. In the context of turbine research environments, conventional approaches for in situ IR calibrations rely on thermocouples embedded in the surface or bonded to the surface using an adhesive layer. A review of the literature points to lack of emphasis on the uncertainty in the calibration arising from the effect of the adhesive substrate and paint on the temperature measured by the thermocouple, namely that under diabatic conditions (i.e. with through-wall heat flux) the measured temperature deviates from the true surface temperature. We present a systematic study of the sensitivity of the thermocouple temperature to installation conditions seen in typical laboratory IR calibration arrangements, and under realistic conditions of through-wall heat flux. A new technique is proposed that improves the calibration accuracy by reducing the difference between the thermocouple measurement and the external wall temperature seen by the infrared camera. The new technique has the additional advantage of reducing the uncertainty associated with selecting an appropriate pixel in the IR image, by providing a region with greater temperature uniformity especially in environments with significant underlying lateral surface temperature variation. The new approach is experimentally demonstrated and compared to more conventional measurement techniques on a heavily film-cooled nozzle guide vane assembly operated at highly engine-representative conditions. The proposed technique is demonstrated to significantly improve the measurement accuracy for IR in situ calibrations in environment with through-wall heat flux and surface temperature non-uniformity.

Discontinuous Galerkin methods for multi-layer ocean modeling: Viscosity and thin layers

The work described here is part of a continuing project to develop, analyze, and test some procedures for using discontinuous Galerkin (DG) numerical methods in multi-layer, isopycnic models of ocean circulation. The steps taken in the present paper include the following.(1) Develop an implementation of horizontal viscosity for usage in DG methods for multi-layer models. This step involves a formulation of the local DG method that can be used in the context of barotropic-baroclinic splitting, a widely-used approach to handling the multiple time scales in ocean circulation models.(2) Develop techniques that enable a layered model to exhibit thin layers without computational failures. Layers with negligible thickness can develop in situations that include coastal upwelling, outcropping of surfaces of constant density to the upper boundary of the fluid due to lateral variations in temperature, or intersections of density surfaces with bottom topography. For the sake of DG computations involving thin layers, this paper develops (i) implementations of wind stress, bottom stress, and interfacial shear stress that do not provoke spuriously large velocities, and (ii) a limiter that maintains nonnegative layer thicknesses in DG solutions.(3) Test the above techniques in numerical experiments involving model problems.

Edge-driven convection and thinning of craton lithosphere: Two-dimensional thermal-mechanical modeling

There are usually abrupt changes in lithospheric thickness at the boundaries between ancient cratons and adjacent young mobile belts. Lateral variations in temperature and density between the two can trigger small-scale mantle convection (edge-driven convection, EDC). Here, we use two-dimensional thermal-mechanical simulations to explore the EDC caused by the lithospheric step between a craton and a mobile belt, and its role in the thinning of the craton lithosphere. The results show that the impact of EDC on a craton depends on the properties of the craton lithosphere and on their contrasts with the adjacent mobile belt, given the same initial condition. When the craton lithospheric density is relatively large, a high-strength craton has strong ability to resist EDC, and craton lithospheric thinning is limited to the edge. In contrast, the ability of a low-strength craton to resist EDC is weak, and the craton lithosphere is gradually eroded by the downward flow, eventually leading to large-scale thinning of the cratonic lithosphere. When the craton lithospheric density is relatively small, regardless of the strength of the cratonic lithosphere, the craton can well withstand the impacts of EDC. In this case, upwelling flow drives cratonic lithosphere materials to the base of the mobile belt, and lithospheric thinning only occurs at the edge of the craton lithosphere. The Archean North China Craton (NCC) was surrounded by Phanerozoic mobile belts, and its lithospheric thinning first occurred on the northern and eastern margins, a process that lasted for a long time. We suggest that EDC has played an important role in lithospheric thinning of the NCC, in particular the initiation of lithospheric thinning, but we cannot rule out the additional contributions from other mechanisms.

Tidally induced lateral variations of Io's interior

Satellite and recent Earth-based observations of Io's surface reveal a specific spatial pattern of persisting hotspots and sudden high-intensity events. Io's major heat producing mechanism is tidal dissipation, which is thought to be non-uniformly distributed within Io's mantle and asthenosphere. The question arises to what extent Io's non-homogeneous heat production can cause long-wavelength variations in the interior and volcanic activity at the surface. We investigate dissipation patterns resulting from two different initially spherical symmetric visco-elastic rheological structures, which are consistent with geodetic observations. The spatial distributions of the time-averaged tidal heat production are computed by a finite element model. Whereas for the first rheological structure heat is produced only in the upper viscous layer (asthenosphere-heating model), the second rheological structure results in a more evenly distributed dissipation pattern (mixed-heating model) with tidal heating occurring in the deep mantle and the asthenosphere. To relate the heat production to the interior temperature and melt distribution, we use steady-state scaling laws of mantle convection and a simple melt migration model. The resulting long-wavelength thermal heterogeneities strongly depend on the initial tidal dissipation pattern, the thickness of the convective layer, the mantle viscosity, and the ratio between magmatic and convective heat transport. While for the asthenosphere-heating model a strong lateral temperature signal with up to 190 K peak-to-peak difference can remain, convection within a thick convective layer, as for the mixed-heating model, can reduce the lateral temperature variation to <1 K, if the mantle viscosity is sufficiently low. Models with a dominating magma heat transport preserve the long-wavelength pattern of tidal dissipation much better and are favoured, because they are better to explain Io's thick crust. The approach presented here can also be applied to investigate the effect of an arbitrary interior heating pattern on Io's volcanic activity pattern.

Constraints on D″ beneath the North Atlantic region fromPandStraveltimes and amplitudes

In this study, we discuss possible origins of the D″ reflector beneath the North Atlantic region based on a combined analysis of P and S wave data. We use over 700 USArray station recordings of the M_w 6.3 earthquake that occurred in April 2010 in Spain. In order to investigate the D″ layer we look for waves reflected off the top of it, namely PdP and SdS waves, and compare them to the core–mantle boundary (CMB) reflections used as reference phases. The differences in traveltimes and amplitudes are sensitive to D″ properties. Because the USArray installation generates a dense array, we are able to provide an almost continuous map of the detection or absence of PdP and SdS waves in the North Atlantic region. We use a Bayesian inversion for traveltimes, together with synthetic seismogram calculations, to find the best-fitting D″ properties, (Vp, Vs) jumps across the D″ interface and D″ thickness. We find that the best-fitting models are for a D″ layer of about 300 km thick, with or without a velocity gradient of about 30 km at the top of it. Regardless of the model type, positive and similar velocity increases in both P and S velocities at the D″ interface, ranging from 2.7 to 3.8 per cent, are required to fit the data well. Our data rule out velocity decreases in P and S waves at the D″ interface as well as no velocity reduction above the CMB. There are also regions where we do not observe PdP and SdS waves. Collectively, these observations suggest lateral variations in both chemistry and temperature, combined with phase transitions. For instance, ancient oceanic basalt debris from the Farallon slab could be modulating the detection of the D″ reflector in this region.

Integrating Gravity and Surface Elevation With Magnetic Data: Mapping the Curie Temperature Beneath the British Isles and Surrounding Areas

In this work, we study the lithospheric structure of the British Isles using a methodology that allows for forward modelling of the Curie temperature depth based on seismic, elevation and gravity observations within an integrated geophysical-petrological approach (LitMod3D). We compute 3D thermal models and self-consistently determine the density in the mantle based on temperature, pressure and bulk composition. Finally, we derive Curie temperature depth maps and forward calculate magnetic anomalies at the airborne level using a spherical magnetic modelling software (magnetic tesseroids) to estimate the geothermal magnetic signal. Our results show lateral lithospheric variations across the model domain, with Great Britain being characterized in general by thicker and colder lithosphere, especially in the south-east, and the thinnest and warmest lithosphere being located beneath west Scotland, Northern Ireland and in the north-west oceanic area. Our estimated Curie temperature depth map resembles the values obtained using other techniques (spectral method and surface heat flow inversion) in some areas, but discrepancies are notable in general. We determine that the effect of typical lateral temperature variations (i.e., Curie isotherm depth) accounts for 5-15%, on average, and up to 70% locally of the crustal magnetic signal at the airborne level (5 km altitude). Our lithospheric models are in general agreement with published tomography models as well as other geophysical studies.

The effect of temperature-dependent thermal conductivity on the geothermal structure of the Sydney Basin

The thermal structure of continental crust is a critical factor for geothermal exploration, hydrocarbon maturation and crustal strength, and yet our understanding of it is limited by our incomplete knowledge of its geological structure and thermal properties such as hydrogeologic and thermo-mechanical feedbacks that come into play. One of the most critical parameters in modelling upper crustal temperature is thermal conductivity, which itself exhibits strong temperature dependence. In this study, we integrate new laboratory measurements of the thermal conductivity of Sydney Basin rocks under varying temperatures, with finite-element geothermal models of the Sydney Basin using deal.II (Bangerth et al. in ACM Trans Math Softw (TOMS) 33:24, 2007). Basin geometry and structure are adapted from Danis et al. (Aust J Earth Sci 58:517–42, 2011), which quantified the extent of Triassic sediment, Permian coal measures, Carboniferous volcanics and thickness of the crystalline crust. We find that temperature-dependent thermal conductivity results in lower lateral variations in temperature compared to constant thermal conductivity models. However, the average temperatures at depth are significantly higher when temperature-dependent thermal conductivity effects are included. A number of regions within the Sydney Basin demonstrate temperatures above 150 °C at depths of less than 2000 m in these models, for instance NW of Singleton, exhibits a strong thermal anomaly, demonstrating the potential for geothermal prospectivity of the region from experimentally constrained thermal parameters.

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

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.

3D modeling of crustal shortening influenced by along-strike lithological changes: Implications for continental collision in the Western and Central Alps

The European Alps show major along-strike variations in the partitioning of crustal shortening between the upper and the lower plates, either explained by lateral variation in temperature and rheology, or by along-strike changes in crustal-scale lithology. Here, we present the first 3D thermomechanical geodynamic model to test the potential impact of along-strike lithological (and associated rheological) changes and lateral temperature variations on crustal shortening during continental collision in the Western and Central Alps. Numerical modeling results suggest a minor impact of lateral thermal variations and lithological changes in the lower plate for the Alpine orogeny. In contrast, lateral lithological changes in the upper plate structure, defined by the presence of the buried Ivrea Body in the Western Alps, should play a major role in determining the present-day architecture of the Alpine belt. Our models suggest that the Ivrea Body acts as a strong, rigid buttress constraining crustal shortening to the lower plate, promoting the formation of the Jura fold-and-thrust belt, and supporting the higher surface elevation observed in the Western Alps. On the other hand, in the Central Alps where the Ivrea Body is absent, much broader distribution of crustal shortening results in lower surface elevation. Numerical modeling results also suggest that crustal shortening in the Central Alps is focused within the upper plate during the final stages of continental collision, favored by the indentation of thickened upper crust of the lower plate, and by detachment of the Adriatic upper crust from the underlying lithosphere.