Liviu Matenco’s research while affiliated with Utrecht University and other places

Asthenospheric flow is a major driver of plate motions and lithosphere deformation. Previous studies have modelled the asthenospheric flow linked to the negative buoyancy of subducting slabs. However, orogenic systems associated with slab retreat are characterised by a more complex asthenospheric flow related to larger-scale processes including orogenic rotations, strain and flow partitioning or the along-strike variability of the subduction mechanics. Understanding deformation in such situations requires a bottom-up approach that simulates the asthenospheric flow and its effects on the overlying lithosphere. Here, we present a novel physical analogue modelling approach where gravity-driven asthenospheric flow is the main driver for lithospheric deformation. A constant volume asthenospheric flow is achieved by a novel inlet-outlet system that allows calibration of the flow velocity, which regulates the lithosphere-asthenosphere coupling. This approach induces asthenospheric flow, which provides an efficient mechanism for transferring deformation to a mechanically stratified lithosphere, where deformation can be studied at higher resolution compared to previous studies. Our approach is validated by a comparison with the slab retreat driven back-arc extension in the Carpathians-Pannonian system of Central Europe. Beyond slab retreat, our approach can be used for modelling asthenospheric flow in other plate tectonic settings.

Along-fault lithological heterogeneity is observed in all fault zones that cross-cut compositional layering. Numerical modelling studies on fault rupture nucleation, propagation and arrest often assume that the fault mechanical behaviour is governed by either the rheological weak phase or by a homogeneous gouge mixture of juxtaposing lithologies. However, the effects of spatial heterogeneity on fault gouge composition and hence its frictional behaviour are less known. In this study, we simulate a mixture of mechanically contrasting rheologies of claystones and sandstones in fault gouges by using lithologies available in the well-known Groningen gas field stratigraphy (Ten Boer and Slochteren members, respectively). Friction experiments were performed in a rotary shear configuration to accommodate the large displacements required to study mixing and clay smearing in faults with large offsets. A velocity stepping procedure was conducted to quantify the rate-dependence of friction and its evolution with displacement. A spatial heterogeneity was introduced by segmentation of the simulated gouge in claystone and sandstone patches. In contrast to previous studies, we show that Slochteren sandstone gouges can exhibit velocity-weakening behaviour related to strain-localization in a principal slip zone with reduced grain size. Our experiments on segmented gouges show displacement-dependent changes in the sliding friction and its rate-dependence. Clay smearing and shear localization on foliation planes cause weakening of the gouge and a shift from velocity-weakening to velocity-strengthening behaviour. Progressive shearing leads to juxtaposition of sandstone segments that are separated only by a thin clay smear. We propose that the associated increase in friction is caused by lithology mixing at the interfaces between the clay smear and the bulk Slochteren sandstone gouge, and by the disruption of continuous Y-shears. Progressive shearing does not lead to a decrease in the rate-sensitivity parameter (a-b). This observation suggests that shearing remains localized on phyllosilicate foliations, possibly accommodated by the increased width of the principal slip zone (PSZ) with displacement. Our results show that fault friction and its rate-dependence are not simply governed by the weakest lithology along a fault plane, nor that they can be simply represented by a homogeneous mixture of the juxtaposing lithologies. Detailed knowledge of the stratigraphic layering in combination with the fault offset is required to predict the macroscopic frictional behaviour of heterogenous fault gouges.

Understanding the formation, migration and emanation of deep CO2, H2O and noble gases (He–Ne) in deepseated deformation settings is crucial to understand the complex relationship between deep-originated fluids and lithospheric deformation. To gain a better insight into these phenomena, we studied the origin of H2O, CO2 and noble gases of gas-rich springs found in the Târgu Secuiesc Basin located in the southeasternmost part of the Carpathian-Pannonian region of Europe. This study area is one of the best natural examples to understand the connection between the deep sources of gas emanations and deep-seated deformation zones, providing an excellent analogue for regions worldwide with similar tectonic settings and fluid emanation properties. We studied the δ2H and δ18O stable isotopic ratios of the spring waters, and the δ13C, He and Ne stable isotopic ratio of the emanating CO2-rich gases dissolved in the mineral spring waters in Covasna town and its vicinity. Based on the δ2H, δ13C, δ18O stable isotopic ratios, the spring waters and the majority of the gases are released through two consecutive fluid infiltration events. The preservation of the metamorphic signal of the upwelling H2O is linked to the local groundwater flow and fault abundancy. Furthermore, the noble gas isotopic ratios show a high degree of atmospheric contamination in the dissolved water gasses that is most likely related to the local hydrogeology. Nevertheless, the elevated corrected helium stable isotopic ratios (Rc/Ra) of our filtered data suggest that part of the emanating gases have a potential upper mantle source component. Beneath the Southeastern Carpathians, mantle fluids can have multiple origin including the dehydration of the sinking slab hosting the Vrancea seismogenic zone, the local asthenospheric upwelling and the lithospheric mantle itself. The flux of the mantle fluids is enhanced by lithospheric scale deformation zones that also support the fluid inflow from the upper mantle into the lower crust. The upwelling CO2–H2O mantle fluids may induce the release of crustal fluids by shifting the pore fluid composition (X(CO2)) and, consequently, initiating decarbonisation and devolatilization metamorphic reactions as a result of carbonate and hydrous mineral destabilisation in the crust. Based on the p-T-X(CO2) conditions of calc-silicates and the local low geotherm, we emphasise the importance of the upwelling fluids in the release and upward migration of further H2O and CO2 in the shallower lower and upper crust. Our observations in the Southeastern Carpathians show a strong similarity to other deep-seated deformation zones worldwide (e.g., Himalayas, Alps, San Andreas Fault). We infer that migration of deep fluids may also play an important role in addition to temperature control on the generation of crustal fluids in deep-seated deformation zones.

Understanding the interactions between surface and deep Earth processes is important for research in many diverse scientific areas including climate, environment, energy, georesources and biosphere. The TOPO-EUROPE initiative of the International Lithosphere Program serves as a pan-European platform for integrated surface and deep Earth sciences, synergizing observational studies of the Earth structure and fluxes on all spatial and temporal scales with modelling of Earth processes. This review provides a survey of scientific developments in our quantitative understanding of coupled surface-deep Earth processes achieved through TOPO-EUROPE. The most notable innovations include (1) a process-based understanding of the connection of upper mantle dynamics and absolute plate motion frames; (2) integrated models for sediment source-to-sink dynamics, demonstrating the importance of mass transfer from mountains to basins and from basin to basin; (3) demonstration of the key role of polyphase evolution of sedimentary basins, the impact of pre-rift and pre-orogenic structures, and the evolution of subsequent lithosphere and landscape dynamics; (4) improved conceptual understanding of the temporal evolution from back-arc extension to tectonic inversion and onset of subduction; (5) models to explain the integrated strength of Europe’s lithosphere; (6) concepts governing the interplay between thermal upper mantle processes and stress-induced intraplate deformation; (7) constraints on the record of vertical motions from high-resolution data sets obtained from geo-thermochronology for Europe’s topographic evolution; (8) recognition and quantifications of the forcing by erosional and/or glacial-interglacial surface mass transfer on the regional magmatism, with major implications for our understanding of the carbon cycle on geological timescales and the emerging field of biogeodynamics; and (9) the transfer of insights obtained on the coupling of deep Earth and surface processes to the domain of geothermal energy exploration. Concerning the future research agenda of TOPO-EUROPE, we also discuss the rich potential for further advances, multidisciplinary research and community building across many scientific frontiers, including research on the biosphere, climate and energy. These will focus on obtaining a better insight into the initiation and evolution of subduction systems, the role of mantle plumes in continental rifting and (super)continent break-up, and the deformation and tectonic reactivation of cratons; the interaction between geodynamic, surface and climate processes, such as interactions between glaciation, sea level change and deep Earth processes; the sensitivity, tipping points, and spatio-temporal evolution of the interactions between climate and tectonics as well as the role of rock melting and outgassing in affecting such interactions; the emerging field of biogeodynamics, that is the impact of coupled deep Earth – surface processes on the evolution of life on Earth; and tightening the connection between societal challenges regarding renewable georesources, climate change, natural geohazards, and novel process-understanding of the Earth system.

This book includes the abstracts accepted to be part of the technical programme of the ILP-GEOSCIENCE 2022, the joint event of the 16th Workshop of the International Lithosphere Program Task Force Sedimentary Basins & 7th Geoscience Symposium of the Romanian Society of Applied Geophysics, organized in Bucharest, Romania The ILP-GEOSCIENCE 2022 joint event took place under the theme: The coupling between sedimentary basins, orogenic areas, and their underlying lithosphere in applied and theoretical geosciences. In advance of the technical presentation days, a pre-event field trip in the SE Carpathians (4-5 October 2022) was organized. Technical presentations, extended over two days, brought along speakers from United Arab Emirates, Poland, France, Italy, Spain, Morocco, Hungary, Serbia, Norway, Netherlands, Turkey, Egypt, and researchers from all continents who assisted on-site or virtually. The event concluded with a one-day post-event field trip to one of the largest salt mines in Europe, at 208 m below the earth surface and was an opportunity to discuss about mining-triggered hazards and geophysics. A selection of the works presented during the ILP-GEOSCIENCE 2022 (6-7 October 2022) will also appear as extended papers within a forthcoming book under the aegis of the Romanian Society of Applied Geophysics.