Discovering the Critical and Strategic Raw Materials potential of historical mining dumps of Sardinia

Modern society bases its economic and industrial development on the use of advanced technologies, which are produced using materials and metals defined in the European Union as critical and strategic raw materials about the risk of their supply, linked to geological and geopolitical factors, and their relevance for the European chain of value. The CRM Act approved by the European Parliament addresses the future policies on CRM and SRM of the Member States, particularly for the development of primary (mining) and secondary (recycling) sources of these materials. In the context of recycling policies, particular emphasis is given to the necessary evaluation of the potential of waste from past extractive activities.  As a part of the wider Project Geoscience IR coordinated by the Italian Institute for Environmental Protection and Research (ISPRA), the University of Cagliari (UniCa) is carrying out a study on Sardinian mining dumps, which provides for their mapping and characterization through sampling and laboratory activities, to investigate their possible content in CRMs. The first studies focused on SW Sardinia districts, have produced encouraging results, with the identification of the presence of CRMs in different types of wastes of various localities. The first target area is that of Montevecchio, once one of the largest mine districts in Italy, which now hosts over 13 million cubic meters of mining and processing wastes from the exploitation of a large Pb-Zn hydrothermal vein field. The study highlighted the economic potential of some of these materials, rich in Zinc (2.6%), Lead (1%) and Rare Earth Elements (about 600 ppm). In the south of Montevecchio, a second area of inferred high potential is the Fluminese region, marked by several kinds of CRM-bearing hydrothermal ore deposits. In this area, the mine dumps of the old Santa Lucia fluorite-barite mine are currently under study. Apart from fluorite and barite, they are suspected to host Ni-Co minerals and some amount of REE, given the wide chromatic variety of fluorites and the presence of Agardite-Ce in the mineralization. A third target under study is the Sulcis district, a historical mining area with numerous mine dumps scattered over a wide territory. Among them, of particular interest are the wastes related to the exploitation of Fe (magnetite) and Pb-Zn-Cu sulfide skarn ores, often marked by W and Sn contents. The goal of the Project is to produce a database containing information on CRMs contents in the various Sardinian historical mining dumps, and a new metallogenic map of Sardinia that may include the waste deposits of possible economic interest, which were not reported in the two previous produced editions. The map will constitute a model for broader mapping of Italian resources at a national scale.