Abstract This study summarizes a compilation of studies and cartographical work on seabed mineral deposit types in pan-European seas developed under the GeoERA-MINDeSEA project. In total, 692 occurrences and 1194 individual mineral samples of volcanogenic massive sulfides and hydrothermal mineralization, ferromanganese crusts, phosphorites, marine placer deposits, polymetallic nodules, and their associated strategic and critical raw material (CRM) elements have been characterized. The GeoERA-MINDeSEA project has been built based on extensive studies carried out previously, which include geophysical surveys, sampling stations, underwater photography and remotely operated vehicle (ROV) surveys, and mineralogical, geochemical and isotopic studies. This study develops pan-European and national databases, and expands strategic and CRM knowledge through a compilation of mineral potential and metallogenic studies of CRM resources in European seas. For the first time, the GeoERA-MINDeSEA portal publishes harmonized marine mineral resource information, case studies and maps, and identifies potential areas for responsible resource exploration and extraction, strategic management, and marine spatial planning. This study also provides recommendations for future target areas, studies and standards to be used across Europe as part of this project.

Abstract: Phosphorite, limestone, basalt, and breccia/conglomerate occur on the flanks of central Pacific Cretaceous seamounts. Phospbatization occurred during the Tertiary, at or immediately below the sediment-water interface, within thin bodies of porous carbonate sediment and within all rock types that occur on the seamounts. The phosphorites are composed of carbonate fluorapatite (CFA), which lines pores and replaces carbonate and silicate protoliths; protolith fabric is locally preserved in fine detail. Phosphatization is typically most pervasive adjacent to pores, fractures, and the outer surfaces of samples. In order of decreasing abundance, diagenetic minerals associated with seamount phosphorites (SMP) include: CFA, Fe-Mn oxyhydroxides, palagonite, smectite, phillipsite, and barite. This mineral assemblage indicates that CFA formed under conditions consistent with low-temperature, open-circulation seafloor alteration of basalt. The common association between CFA and precipitation of Fe-Mn oxyhydroxides indicates that SMP formed under oxic to suboxic conditions. Phosphatization is characterized by mineralization fronts; the angular superposition of those fronts (successive mineralizing fluids coming from different directions) locally leads to irregularly shaped domains that differ in pervasiveness of phosphatization, degree of fabric preservation, and abundance of secondary minerals. Phosphatization is, therefore, controlled by a variety of factors including protolith mineralogy and fabric, degree of pore-fluid saturation with respect to CFA, rate of pore-fluid/seawater circulation (rock-water ratio), and number of previous episodes of phosphatization.