Volcanic-sedimentary metal deposition in paleomargin environmenta: the "protore" of Castello Medusa, Central Sardinia

The metallogenic periods took place at different moments of the geological evolution of Sardinia, but at places they interacted: the close correlation between the metal parageneses in the Ordovician - Silurian sequences outcropping in the central part of the island, and the veins and masses associated with the Hercynian magmatism is depicted. The volcanic-sedimentary mixed-sulphide lenses contained in Silurian occurrences show clear sedimetary structures, and the connection with coeval volcanics seems evident. These mineralizations are thought to be the protores for the subsequent hercynian orogenesis which had a strong effect as a promoter of the remoulding of preexisting mineral concentrations to give new ore and industrial minerals. A new prospecting programme has been started in Central Sardinia following the ore-bearing horizon along the Ordovician-Silurian boundary with the purpose to better understand these primary metal depositions, their relationship with geodynamic structures, and ore mobilisations caused by the Hercynian granites. The geochemical anomalies of this horizon detected in the area of "Castello Medusa " support detailed prospecting works.