The Service géologique du Luxembourg (Geological Survey of Luxembourg) SGL, a division of the Administration des ponts et chaussées (Roads and bridges administration), collects information about past and current mineral resource occurrence and extraction sites in Luxembourg. This information is assembled in a spatial database (about 800 records). The majority of these are building and dimension stone quarries (sandstone, limestone) and iron ore mines. Accessorily, there are slate quarries and a few other metallic ore mines. In the context of MINTELL4EU, about 550 validated records on quarries, gravel pits and mines were extracted and harmonized according to the MINTELL4EU guidelines.

Marine ferromanganese crust deposits are potential mineral resources that contain base metals and strategic and critical elements such as cooper (Cu), cobalt (Co), vanadium (V), nickel (Ni), titanium (Ti), platinum group elements (PGEs) or rare earth elements (REEs). Traditionally, marine precipitates are defined as: a) purely hydrogenetic when all constituents are derived from cold seawater, (b) diagenetic, when all constituents are derived from cold sediment pore water; and (c) hydrothermal when precipitation occurs in the vicinity of hydrothermal vent sites from fluids with temperatures higher than ambient bottom waters. Hydrogenetic Fe-Mn crusts occur throughout the global ocean on seamounts, ridges and plateaus, where currents have kept the rocks free of sediment for millions of years. Some ferromanganese (Fe-Mn) crusts exhibit a mixed origin, primarily either hydrothermal-hydrogenetic or hydrogenetic-diagenetic (Hein et al., 2000; 2003; 2013; Muiños et al. 2013; Bau et al., 2014; Marino et al., 2017). In many places, marine phosphorites are accompanied by Fe-Mn crust mineralisations on the seafloor of continental shelves and slopes along the western continental margins of the Atlantic Ocean. Some thick Fe-Mn crusts also contain carbonate fluorapatite, which was incorporated into the crusts during specific periods prior to middle Miocene during main Cenozoic episodes of phosphatization. These deposits are related to strong upwelling along the continental margins and seamounts. Marine phosphorites are known to concentrate rare earth elements and yttrium (REY) during early diagenetic formation (Hein et al., 1993; 2016; González et al., 2016). Although there are several references to ferromanganese crusts and their association with phosphorites in the literature, the genetic models for explaining their relationship and metal concentration are still poorly understood.

Seafloor massive sulphides (SMS) are modern equivalents of on-shore (ancient) volcanogenic massive sulphides (VMS) which have constituted important mining targets through history in many regions of Europe. VMS deposits are generally stratiform accumulations of sulphides formed at or just beneath the seafloor as a result of volcano-magmatic activity. The sulphides are precipitated from hot hydrothermal solutions when they come in contact with cold seawater. Deposits of this type that form today are known as seafloor massive sulphides, and the associated sulphurous plumes are called black and white smokers. Data from ancient VMS deposits are essential for the present-day understanding of the formation, structure and composition of SMS deposits. VMS deposits are among the most important deposit types for a number of commodities, including copper (Cu), zinc (Zn), lead (Pb), silver (Ag) and gold (Au). In addition, they may contain economic grades of cobalt (Co), tin (Sn), barium (Ba), sulphur (S), selenium (Se), indium (In), bismuth (Bi), tellurium (Te), gallium (Ga) and germanium (Ge). Several of these minor constituents are considered critical raw materials by the EU. The modern equivalents are found on the ocean floor, along present-day spreading ridges and volcanic centres, and are the target of steadily increasing attention as a possible source for both base, precious and special metals.

Spatial distribution of occurrences of Co in European land and sea and respective genetic types.