Role of lithospheric-scale geological heterogeneity in continental lithosphere dynamics

Starting from our analysis of the Alpine orogen in 4D-MB (Spooner et al. 2022), we analysed how the Alps compare to other parts of the Alpine-Himalayan collision zone (AHCZ). We find that all orogens in the AHCZ exhibit characteristic diffused seismicity compared to the intraplate regions (Storchak et al. 2013). Interestingly, they also show a thicker-than-average silica-rich upper crust and total crustal thickness, while their lithosphere thickness has been shown to be similar to that of stable continental interiors (e.g., Tibet, Zagros Priestley et al. 2018). These observations provide a metric for the lithospheric-scale geological inheritance, the role of which we aim to understand in continental lithosphere dynamics over geologic timescales. We use data-driven modelling to compute the present-day thermomechanical state of the AHCZ lithosphere (Cacace & Scheck-Wenderoth 2016). To do so, we first compute 3D steady-state temperature distribution in the AHCZ considering variations in the crustal layers from published models with representative radiogenic heat production and thermal properties. The temperature boundary condition is fixed at the surface to 15oC and at the base of the model (200 km) is derived from the conversion of seismic tomography models. We then compute the differential stress distribution for the AHCZ using equilibrium 3D temperature distribution and laboratory-derived rheological properties representative for each layer in the model. Our results (Kumar et al. 2023) indicate the existence of a critical crustal thickness, which is thermodynamically controlled by the internal energy and chemical composition of the crust. The value of this critical crustal thickness matches the global average of continental crust thickness. Orogenic lithospheres with thicknesses above this critical value possess higher potential energy and are weakened by the internal energy from heat-producing elements, whereas continental intraplate regions with thicknesses close to the critical crustal thickness are stronger. Weaker orogenic lithospheres deform via dissipating this energy in a diffused deformation mode, leading to zones of deformation in contrast to focused deformation at the plate boundaries. The observed crustal differentiation in the AHCZ could be understood as perturbations to the critical crustal thickness caused by plate-boundary forces. The dynamic evolution of these perturbations (Houseman & Houseman 2010) indicates that the critical crustal thickness is a stable fixed-point attractor in the evolutionary phase space of the continental lithosphere. The exact characteristics of the evolutionary path depend on the amplitude of perturbations, the source of the initial driving energy, and the relaxation time scale of the active dissipative process (thermal diffusion and/or viscous deformation). Typical ranges of thermal properties and viscosities of the continental lithosphere suggest that the thermal diffusion always lags the viscous relaxation giving rise to a thermodynamic feedback loop between thermal and mechanical relaxation of the out-of-balance energy in the orogenic lithosphere. Exponentially growing energy states, leading to runaway extension are efficiently dampened by enhanced dissipation from radioactive heat sources. This eventually drives orogens with their thickened radiogenic crust towards a final equilibrium state

Beckenmodellierung : Temperatur in Sedimentbecken

The formation of mineral and energy resources involves the interaction of groundwater flow, mechanical deformation, mass and heat transport processes. Thereby, groundwater flow patterns, temperature field, and fluid-rock interactions are all interdependent. This calls for a unified description linking the coupling between the different scales and related physical phenomena involved. A mathematical formulation of the main driving processes affecting basin fluid and heat transport allows developing numerical models as tools to examine the interactions of simultaneously active processes and variable parameters within the constraints given by physical principles and taking into account proper temporal and three dimensional spatial scales. Therefore, the usage of mathematical models is justified by the help they bring in the understanding and verification of specific mechanisms acting in natural systems. In Section “Basin Analysis” at GFZ German Research Centre for Geosciences mathematical models of increasing degree of complexity are applied to the study of energy and mass transport processes in complex sedimentary basins

Modelling the Surface Heat Flow Distribution in the Area of Brandenburg (Northern Germany)

A lithosphere scale geological model has been used to determine the surface heat flow component due to conductive heat transport for the area of Brandenburg. The modelling results have been constrained by a direct comparison with available heat flow measurements. The calculated heat flow captures the regional trend in the surface heat flow distribution which can be related to existing thermal conductivity variations between the different sedimentary units. An additional advective component due to topography induced regional flow and focused flow within major fault zones should be considered to explain the spatial variation observed in the surface heat flow

Fault Control on a Thermal Anomaly: Conceptual and Numerical Modeling of a Low\u2010Temperature Geothermal System in the Southern Alps Foreland Basin (NE Italy)

The interest on low\u2010temperature geothermal resources is progressively increasing since their renewability and widespread availability. Despite their frequency, these resources and their development have been only partially investigated. This paper unravels the major physical processes driving a low\u2010temperature geothermal resource in NE Italy (Euganean Geothermal System) through conceptual and numerical modeling. Dense fracturing associated to regional fault zones and a relay ramp enhances regional to local flow of thermal waters. Their rapid upwelling in the Euganean Geothermal Field is favored by open extensional fractures deforming the relay ramp. The water (65\u201386 \ub0C) is intensively exploited for balneotherapy, rendering it a profitable resource. Three\u2010dimensional coupled flow and heat transport numerical simulations based on this conceptual model are performed. Despite the presence of a uniform basal heat flow, a thermal anomaly corresponding to field observations develops in the modeling domain reproducing the relay ramp. Intensive fracturing extending across a wide area and a slightly anomalous heat flow favors a local increase in convection that drives the upwelling of deep\u2010seated hot waters. The simulations corroborate and refine the conceptual model, revealing that water of up to 115 \ub0C is likely to be found in the unexplored part of the thermal field. This study furthers knowledge on fault\u2010controlled low\u2010temperature geothermal resources where the geological setting could enhance local convection without anomalous heat flows, creating temperatures favorable for energy production. Conceptual and numerical modeling based on solid geological and hydrogeological reconstructions can offer a support tool for further detailed explorations of these prominent resources

Unravelling the importance of fractured zone in regional fluid flow: insights from the hydrothermal modelling of the Euganean geothermal system (ne Italy)

Euganean Geothermal System, fault system, 3D coupled flow and heat transport numerical model

Influence of chemical and mineralogical soil properties on the adsorption of sulfamethoxazole and diclofenac in Mediterranean soils

Abstract Background The irrigation with treated wastewaters can be a way for the introduction of organic contaminants in soils. However, their adsorption onto soils can allow a control of their bioavailability and leaching. The adsorption is influenced by properties of contaminants (water solubility, chemical structure) and soils (organic matter content, pH, mineralogy). This study aimed to investigate the effect of mineralogical composition, organic matter content and others parameters of soils on the adsorption of sulfamethoxazole (SMX) and diclofenac (DCF), two contaminants of emerging concerns (CECs), in real cases (Altamura, Sibari and Noci soils). Results The isotherms data showed that the adsorption of the two CECs closely matched the Freundlich model, even if the DCF could also fit the linear one. The only exception was the adsorption of SMX on the soil of Sibari, for which Langmuir's model fitted better. In all cases, the Kd values were the highest for Altamura soil according mainly to its content of organic carbon. Positive correlations were found between Kd value of DCF and the soil organic carbon and Al oxyhydroxides content, suggesting their roles in its adsorption, while SMX showed only a slight positive correlation with the soil organic carbon content. Finally, between the two CECs studied, DCF was more adsorbed than SMX also because of the lower water solubility of the former. Conclusions The good interaction between DCF and soil organic carbon suggests the organic amendment of soils before the application of treated watewaters. The low adsorption of SMX onto soils suggests greater leaching of this compound which is, therefore, potentially more dangerous than DCF. For this reason, the application of a filtration system with appropriate adsorbent materials before the application of wastewater to soils should be expected. Graphical Abstrac

DEFORM – Deformation patterns in relation to the deep configuration of the lithosphere of the Alps and their forelands

Present-day surface deformation in the Alps in terms of uplift and crustal seismicity has been attributed to surface (i.e., climatic) and tectonic processes (i.e., subduction, slab detachment/break-off, mantle flow). Quantifying the relative contribution of these forces and their interplay is fundamental to understand their role in mountain building. The present-day 3D configuration of the lithosphere and upper-mantle is a prerequisite to assess the contribution of tectonic processes. In the first phase of 4D-MB, INTEGRATE project produced a multidisciplinary data-integrated crustal model of the Alps and its forelands (Spooner et al., 2019, 2020, 2022). In the follow-up project DEFORM, we use these results to quantify how the active forces originating from the internal heterogeneity in the lithosphere and upper-mantle (i.e., lithospheric thickness and slabs in the asthenosphere) can provide some insights into the present-day mechanical set-up of the study area. To objectively interpret the upper-mantle configuration, we convert the results of regional shear-wave tomography models to temperature using an in-house developed tool (Kumar, 2022) based on Gibbs-free energy minimization algorithm (Connolly, 2005). Our results showcase a shallow/attached slab in the Northern Apennines as a common feature in the different tomography models, as also consistent with recent AlpArray seismic data-derived tomography models. They also highlight some differences among the different tomography models beneath the Alps. We quantitatively address these differences by statistically clustering tomography models into three end-members corresponding to the mean and 67% confidence intervals. These end-member models represent scenarios ranging from shallow/attached slabs to almost no slabs in the northern Apennines and Alps. End-member scenarios of the mantle configuration are tested with the new pan-Alpine gravity anomaly by 3D density modelling (IGMAS+, Götze et al., 2023), surface uplift from GNSS, AlpArray seismicity catalogue, mantle flow inferred from the shear-wave splitting measurements of the AlpArray seismic experiment, and resulting topography. As a first step, we model topography and deformation velocities as resulting from buoyancy-forces driven by a quasi-instantaneous flow resulting from the first-order rheological structure of the lithosphere-asthenosphere system using the open-source geodynamic simulator LaMEM (Kaus et al., 2016). We found that detached slab beneath the Alps, but attached beneath the Northern Apennines captures first-order patterns in topography, vertical surface velocities, and mantle flow (Kumar et al., 2022). The presence of an attached slab beneath the northern Apennines can also explain the observed sub-crustal seismicity compared to the upper-crustal seismicity in the Alps. Data-derived scenario-based modelling approach allowed us to capture the first-order characteristics of the lithosphere and upper-mantle configuration in the Alps and corresponding forelands. Although we have been able to explain first-order observations with respect to the end member variations in viscosity and density contrasts, we additionally carried out a global sensitivity analysis to quantify associated uncertainties as well as the degree of parameter correlation within a solid density-effective viscosity phase space. This was done using physics-preserving surrogate models (model order reduction via reduced basis, Degen et al., 2022) to effectively run ensemble models of the dynamic state of the system (Denise et al., 2023). Using surrogate models, we explore deformation velocities and stresses, guiding boundary conditions to reconstruct the loading/unloading history of the last glacial cycle

The influence of mantle hydration and flexure on slab seismicity in the southern Central Andes

Knowledge of the causative dynamics of earthquakes along subduction-zone interfaces and within oceanic slabs is relevant for improving future seismic hazard assessments. Here, we combine the analysis of seismic tomography, the 3D structure of the slab and seismicity to investigate the controlling factors driving slab seismic activity beneath the southern Central Andes. We evaluate the ratio distribution between compressional and shear-wave seismic velocities (Vp/Vs) as a proxy for the hydration state of the lithospheric mantle, oceanic slab, and plate interface. Regions of high Vp/Vs, i.e. areas of hydrated mantle, are principally caused by compaction effects and dehydration reactions. In contrast, slab seismicity in areas of low Vp/Vs and inferred lower fluid content in the overriding plate is facilitated by enhanced flexural stresses due to changes in the subduction angle of the oceanic plate. Plate-interface background seismicity correlates with areas of higher Vp/Vs (hydrous interface) at depths <50 km, while areas of most pronounced plate-locking coincide with regions of low Vp/Vs (anhydrous interface). The regions of anhydrous plate interface are likely candidates for future great megathrust events due to their higher potential for elastic energy accumulation compared to more hydrated regions

The influence of mantle hydration and flexure on slab seismicity in the southern Central Andes

Knowledge of the causative dynamics of earthquakes along subduction-zone interfaces and within oceanic slabs is relevant for improving future seismic hazard assessments. Here, we combine the analysis of seismic tomography, the 3D structure of the slab and seismicity to investigate the controlling factors driving slab seismic activity beneath the southern Central Andes. We evaluate the ratio distribution between compressional and shear-wave seismic velocities (Vp/Vs) as a proxy for the hydration state of the lithospheric mantle, oceanic slab, and plate interface. Regions of high Vp/Vs, i.e. areas of hydrated mantle, are principally caused by compaction effects and dehydration reactions. In contrast, slab seismicity in areas of low Vp/Vs and inferred lower fluid content in the overriding plate is facilitated by enhanced flexural stresses due to changes in the subduction angle of the oceanic plate. Plate-interface background seismicity correlates with areas of higher Vp/Vs (hydrous interface) at depths <50 km, while areas of most pronounced plate-locking coincide with regions of low Vp/Vs (anhydrous interface). The regions of anhydrous plate interface are likely candidates for future great megathrust events due to their higher potential for elastic energy accumulation compared to more hydrated regions

Modelling of multi-lateral well geometries for geothermal applications

Well inflow modelling in different numerical simulation approaches are compared for a multi-lateral well. Specifically radial wells will be investigated, which can be created using Radial Jet Drilling (RJD). In this technique, powerful hydraulic jets are used to create small diameter laterals (25&ndash;50&thinsp;mm) of limited length (up to 100&thinsp;m) from a well. The laterals, also called radials, leave the backbone at a 90° angle. In this study we compare three numerical simulators and a semi-analytical tool for calculating inflow of a radial well. The numerical simulators are FE approaches (CSMP and GOLEM) and an FV approach with explicit well model (Eclipse®). A series of increasingly complex well configurations is simulated, including one with inflow from a fault. Although all simulators generally are reasonably close in terms of the total well flow (deviations &lt;&thinsp;4&thinsp;% for the homogeneous cases), the distribution of the flow over the different parts of the well can vary significantly. Also, the FE approaches are more sensitive to grid size when the flow is dominated by radial flow to the well since they do not include a dedicated well model. In the FE approaches, lower dimensional elements (1-D for the well and 2-D for the faults) were superimposed into a 3-D space. In case the flow is dominated by fracture flow, the results from the FV approach in Eclipse deviates from the FE methods.</p