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Distal skarns form by the metasomatic reactions of a host rock induced by far-traveled hydrothermal fluids. Physical and structural characteristics and geochemical patterns of distal Pbsingle bondZn skarn bodies were studied at the Petrovitsa deposit in southern Bulgaria. Skarn bodies formed from the interaction of hydrothermal fluids with reactive host lithologies (marble and gneiss). These fluids were transported along sub-vertical feeder structures and lithological contacts. Epidote skarn developed in gneiss protolith, and pyroxene (johannsenite) skarn developed in marble. Detailed geological mapping, complimented by measurements of the internal structure of the skarn body using pyroxene growth versors, quantifies the propagation direction of the skarn body: 1) away from the major local fluid conduit (feeder structure), and 2) away from lithological contacts between aluminosilicate rock and marble. Such growth suggests that fluid flow was generally orthogonal to the skarn front propagation direction in the pyroxene skarn. Textural, mineralogical and geochemical data from skarn samples reveal multiple growth generations of major skarn calc-silicates epidote and pyroxene. The epidote skarn is characterized by limited spatial distribution and fine-grained epidote/clinozoisite growth associated with massive replacement and sulfide mineralization. The pyroxene skarn consists of acicular clinopyroxene crystals which form spheroidal aggregates with discrete growth banding. These bands are the physical representation of the cyclic fluid pulses which resulted in rhythmic skarn growth marked by geochemical banding. In situ geochemical analyses in the epidote skarn reveal early Al-rich epidote overprinted by Fe-rich epidote associated with higher Mn and Sr contents and irregular compositional banding. Clinopyroxene (Jo60–95) shows general increase in Na, Al, Mn, and REE + Y with distance from the feeder structure and lithologic contacts. These elements correlate with the distance traveled by the hydrothermal fluid from the feeder to the site of skarnification, which we define using a proxy based on the Al content of pyroxene crystals. This reflects an increasing degree of fluid “contamination” by interaction with the aluminosilicate host rocks and functions as a proxy for fluid transport distance. The spatial distribution of trace-elements in pyroxene on an outcrop scale is indicative of discrete pulses of hydrothermal fluid resulting in precipitation of skarn calc-silicates along the increasingly tortuous fluid pathway between the feeder structure and the skarn front, resulting in both the macro- and micro-scale chemical and textural variability of the skarn body., Lithos, 400-401, ISSN:0024-4937

International audience; The two main types of mineralisation in the Co-Ni-As Bou Azzer district, i.e., “contact” mineralisation” and “cross-cutting” structures have been re-defined based on new field, structural, textural and mineralogical observations. The main orebodies consists of elongated lenses of massive Ni-Co-Fe arsenide minerals. These lenses occur in a core of carbonate or siliceous gangue and are almost exclusively located along the contact between serpentinite and a quartz diorite intrusion. Vein systems, cross-cutting the different lithologies, are ore-bearing only along segments in contact with the serpentinite and/or the massive mineralisation. The two orebody types share a rather similar mineralisation history, starting with a Ni-rich arsenide stage (mainly expressed within the massive mineralisation), followed by a massive Co-arsenide stage recognised in both mineralisation styles, and ending with Fe-rich arsenide and base metal sulphide stage.Detailed field observations, microstructural, tectonic, textural and mineralogical analyses led us to propose a genetic model for the Bou Azzer ore district in which massive mineralisation was formed by alteration and transformation of previously formed breccia levels composed of serpentinite (transformed to gangue) and magnetite/spinel (transformed to Co-Ni arsenide minerals) fragments. Inversely, a tectono-hydrothermal event controlled by a NE oriented transtension generated the vein system, associated certainly with partial leaching and reconcentration of metals from the massive mineralisation because veins are principally mineralised when crossing massive orebodies. We discuss a possible temporal continuum between the two mineralisation styles: massive mineralisation, coeval with serpentinisation (serpentine neoformation), is related to the transformation of brecciated lenses and vein mineralisation is formed as an infill of large fractures during transtensive tectonics. This model has significant tectonic implications, because serpentinite breccia lenses, favourable high-permeability environment for the massive mineralisation formation, can be compared to ophicalcic rocks developed in a context of mantle exhumation by detachment. Two types of textures can be differentiated within the massive mineralisation: i) Brecciated Massive Mineralisation, developed in the core of ophicalcic levels, and ii) Laminated Massive Mineralisation, supposed to form within ancient mylonitic serpentinite levels corresponding to intensive deformation zones. Although the geodynamic significance will not be addressed in this article, we propose and discuss an alternative model in which the presence of exhumed mantle rocks allows the formation of specific massive arsenide deposits.

This roadmap is the product of a grassroots effort by the Swiss Geosciences community. It is the first of its kind, outlining an integrated approach to research facilities for the Swiss Geosciences. It spans the planning period 2025-2028. Swiss Geoscience is by its nature leading or highly in-volved in research on many of the major national and global challenges facing society such as climate change and meteorological extreme events, environmental pol-lution, mass movements (land- and rock-slides), earth-quakes and seismic hazards, global volcanic hazards, and energy and other natural resources. It is essential to under- stand the fundamentals of the whole Earth system to pro-vide scientific guidelines to politicians, stakeholders and society for these pressing issues. Here, we strive to gain efficiency and synergies through an integrative approach to the Earth sciences. The research activities of indivi- dual branches in geosciences were merged under the roof of the 'Integrated Swiss Geosciences'. The goal is to facilitate multidisciplinary synergies and to bundle efforts for large research infrastructural (RI) requirements, which will re-sult in better use of resources by merging sectorial acti- vities under four pillars. These pillars represent the four key RIs to be developed in a synergistic way to improve our understanding of whole-system processes and me- chanisms governing the geospheres and the interactions among their components. At the same time, the roadmap provides for the required transition to an infrastructure adhering to FAIR (findable, accessible, interoperable, and reusable) data principles by 2028.The geosciences as a whole do not primarily profit from a single large-scale research infrastructure investment, but they see their highest scientific potential for ground-break-ing new findings in joining forces in establishing state-of-the-art RI by bringing together diverse expertise for the benefit of the entire geosciences community. Hence, the recommendation of the geoscientific community to policy makers is to establish an integrative RI to support the ne- cessary breadth of geosciences in their endeavor to ad-dress the Earth system across the breadth of both temporal and spatial scales. It is also imperative to include suffi-cient and adequately qualified personnel in all large RIs. This is best achieved by fostering centers of excellence in atmospheric, environmental, surface processes, and deep Earth projects, under the roof of the 'Integrated Swiss Geosciences'. This will provide support to Swiss geo-sciences to maintain their long standing and internatio- nally well-recognized tradition of observation, monitor-ing, modelling and understanding of geosciences process-es in mountainous environments such as the Alps and beyond.