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It is widely known that the subsurface will play a crucial role in the transition towards a carbon-neutral society, with the aid of technologies like geothermal energy, CO2-storage, .... Nevertheless, still a lot of aspects concerning the subsurface, its structure and characteristics remain to be investigated to facilitate the use of underground space in an efficient and safe way. In-depth investigation of the subsurface with conventional techniques such as seismic campaigns or drillings requires high investments, and it is not always straightforward to determine the success-rate upfront. This leads to geodata collections typically displaying a large variety and scatter, both concerning data (type) availability and in spatial distribution. Additionally, incorporating subsurface knowledge from neighboring countries often is challenging, but at the same time indispensable to increase understanding of the own subsurface, not least because some projects may display cross-border influences. It is clear that subsurface exploration benefits from a cross-border and cross-thematic data collection and interpretation approach. One way to organize such data centralization was explored in the framework of the European Horizon2020-project GeoConnect³d, by means of constructing a Structural Framework (SF) and a database of Geomanifestations (GM) for several pilot study areas. The Structural Framework defines geological units by its limits (e.g., faults, terrane boundaries, ...). All known limits and associated parameters are structured in a uniform and inter-connected way. Furthermore, the SF is designed on multiple zoom-levels, hence it can serve as a real backbone to integrate multiple other subsurface models of various scale and resolution together. Geomanifestations are anomalous observations covering a wide range of geo-disciplines, including —but not limited to— temperature, geochemistry, mineralogy and even geophysics data. Such irregularities are too often excluded or ignored in view of the larger cloud of ‘normal’ datapoints. Nevertheless, precisely these anomalies can be of great value for identifying subsurface processes and serve as an excellent pathway for communication to non-experts, and also as guideline for further research. In addition to GIS- and attribute-information, Factsheets summarize the relations between individual geomanifestations, and, if applicable, their connection to the Structural Framework. Especially the latter, the combination of the (independent) elements SF and GM, gives a powerful tool that allows exploring the subsurface in an original and cost-efficient way. The newly gained insights can be directly linked and are extremely relevant to the use of the subsurface, either as storage space or as renewable/green energy-source. But it goes further than that. The overall usability of the SF and GM database is far more fundamental, as it gives innovative clues about characteristics and processes at play in the subsurface, such as fault permeability and connectivity, the presence of advection cells in the upper crust, or gas origin and migration pathways. To quote just one example; in the area of Spa, Belgium, elevated 3He/4He-ratios were analyzed (Griesshaber et al., 1992), a parameter that can highlight mantle gas contribution in gas seeps (White, 2013). This observation was unexpected given the far distance from any volcanic activity, but suggests the presence of deep-seated, transcrustal faults and/or a large-distance connectivity till the Eifel area where mantle-derived magma was involved in recent volcanism. When indirect indications like this are not considered further, such valuable subsurface knowledge is easily overlooked and not at all taken into account for investigating in more detail in the future. Even when limited resources or funding is available, the above-illustrated SF+GM approach can shed new light on properties and processes of the subsurface, given its novel and multidisciplinary approach. An inherent drawback, however, is that such a database is never complete and includes information from a variety of sources. Not only does this demands careful consideration on which data is included (or not), it also has to be taken into account for future database expansion as well as for data interpretation. Simple visualizations on a map without further (geological) background, e.g., combining both surface and at depth data as is the case for Wiesbaden, Germany (Mittelbach & Siebert, 2014), may lead to false conclusions. However, the provided Factsheets and metadata can help in this. Furthermore, at this moment, a large proportion of the entries depends on the availability of literature data, which implies some data source bias is unavoidable. For example, CO2-data typically is measured for springs and streams, while dry CO2-seeps easier remain unnoticed and therefore are reported less consistently. New data collection campaigns, possibly including bio-indicators like plants or ants (e.g., Berberich & Schreiber, 2013), can provide a good starting point for this. The uniform and well-designed structure of the database allows very easy expansion, be it for newly discovered faults, additional geomanifestation types, or parameter updates of either part. In addition, as demonstrated in the GeoConnect³d project, the SF+GM approach is fully transferable to other study areas. This clears the way for a cost-efficient cross-border exploration of the subsurface with wins for both the academic world and common public (geoheritage, education, ...), and significantly contributes to a more data-supported outline for subsurface management. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166. References Berberich, G., & Schreiber, U., 2013. GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany). Animals, 3, 475-498. Griesshaber, E., O'Nions, R.K. & Oxburg, E.R., 1992. Helium and carbon isotope systematics in crustal fluids from the Eifel, the Rhine Graben and Black Forest, F.R.G. Chemical Geology, 99, 213-235. Mittelbach, G. & Siebert, S., 2014. Gutachten zur Festsetzung eines Heilquellenschutzgebietes für die Heilquellen (Große und Kleine Adlerquelle, Schützenhofquelle, Kochbrunnen, Salmquelle und Faulbrunnen) von Wiesbaden, Stadt Wiesbaden (WSG-ID 414-005), Wiesbaden, pp. 1-52. White, W.M., 2013. Chapter 12: Noble Gas Isotope Geochemistry, Isotope Geochemistry course notes. Cornell University.

The transition towards a clean and low carbon energy system in Europe will increasingly rely on the use of the subsurface. Despite the vastness of subsurface space, only a fraction of it is suitable for the exploitation of geo-resources. The distribution and fitting combination of required conditions is determined by geological processes. We are, therefore, constrained in where we can develop resources and capacities. Moreover, increased subsurface use in a restricted area will inevitably lead to high chances of interferences and conflicts of interest. This means that sound geological information is essential to optimise the subsurface contribution to a safe and efficient energy transition. Within this scope, the main goal of the GeoConnect³d project is to convert existing geological data into an information system that can be used for various geo-applications, decision-making, and subsurface spatial planning. This is being accomplished through the innovative structural framework model, which reorganises, contextualises, and adds value to geological data. The model is primarily focused on geological limits, or broadly planar structures that separate a given geological unit from its neighbouring units. It also includes geomanifestations, highlighting any distinct local expression of ongoing or past geological processes. These manifestations, or anomalies, often point to specific geologic conditions and, therefore, can be important sources of information to improve geological understanding of an area. Geological data in this model are composed of spatial data at different scales, with a one-to-one link between geometries and their specific attributes (including uncertainties), and of semantic data, with data organised conceptually and categorised and/or linked using SKOS hierarchical and generic schemes. Concepts and geometries are linked by a one-to-many relationship. The combination of these elements then results in a multi-scale, harmonised and robust model. The structural framework-geomanifestations methodology has now been applied to different areas in Europe. The focus on geological limits brings various advantages, such as displaying geological information in an explicit, and therefore more understandable, way, and simplifying harmonisation efforts in large-scale geological structures crossing national borders. The link between spatial and semantic data is the essential step adding conceptual definitions and interpretations to geometries. Additionally, geomanifestation data successfully validates or points to inconsistencies in specific areas of the model, which can then be further investigated. The model demonstrates it is possible to gather existing geological data into a comprehensive knowledge system. We consider this as the way forward towards pan-European integration and harmonisation of geological information. Moreover, we identify the great potential of the structural framework model as a toolbox to communicate geosciences beyond our specialised community. This is an important step to support subsurface spatial planning towards a clean energy transition by making geological information available to all stakeholders involved. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166.

The battery market for electric vehicles and renewable energy storage is dominated by rechargeable lithium-ion batteries, making lithium supply essential to climate action through decarbonization. In 2019, more than half of the world's lithium was sourced from lithium pegmatites of the Li-Cs-Ta (LCT) family, predominantly from Australia. Current global lithium supply involves long diesel-fueled maritime transport routes, which counteracts lithium's role in climate action. Responsible consumption and production require shorter supply chains from deposit to battery. Reading the mineralogical record of LCT pegmatite deposits can help address the challenge of reducing the climate impact of lithium production, by informing deposit models, mineral exploration, and geometallurgy, therefore promoting local supply. Our research focuses on a belt of LCT pegmatites, which is located along the eastern margin of the late-Caledonian S-type Leinster Batholith, southeast Ireland. The LCT pegmatites are hosted by a major regional shear zone and are part of a tin-lithium province that stretches subparallel to the Iapetus suture from Europe through Nova Scotia to North and South Carolina. We investigated crystal chemical zoning in muscovite, cassiterite, and columbite-tantalite using petrography, scanning electron microscopy, and LA-ICP-MS chemical mapping. The zoning patterns record that pegmatite rare element mineralization resulted from an interplay of magmatic crystallization, metasomatism, and hydrothermal processes. Late-stage metasomatic alteration led to partial resorption of early minerals including the lithium ore-mineral spodumene, followed by dispersion of lithium and other rare elements into country rocks, mostly within dark mica. Dispersion led to formation of geochemical halos around the LCT pegmatites with the potential to use country-rock lithogeochemistry and mica composition as geochemical vectoring tools. Geochemistry of mica in the granite host analyzed by handheld LIBS has been found to exhibit coherent spatial patterns occurring adjacent to and above LCT pegmatites known at depth from drilling. These channels of mineral-specific geochemical information are distinct from soil geochemical patterns and are not influenced by the same secondary, surface processes such as dilution. As outcrop is virtually absent in the study area, regional stream sediment geochemistry data (Geological Survey Ireland) was assessed as an LCT pegmatite exploration tool. After correcting for geologic background using a linear regression approach, catchments containing LCT pegmatites show high residuals for concentrations of both tantalum and tin. The mineralogy of stream sediment samples from a subsample of these catchments was subsequently analyzed to characterize the host minerals of tin and tantalum. Cassiterite and columbite-tantalite were identified, and both show geochemical and textural signatures that correspond to the zoning patterns mentioned above, which indicates that these minerals were derived from the local LCT pegmatites. These results suggest that, when regional geology and tectonic setting are prospective, lithium pegmatite prospectivity can be further assessed for tin-tantalum associations in (often publicly available) regional stream sediment data. Following geospatial analysis, stream sediment samples could be obtained from individual prospective catchments and their mineralogy analyzed. Local-scale geochemical surveys could follow where stream sediments of prospective catchments contain tin and tantalum oxides with chemistries and textures indicative of a lithium pegmatite source.