S. Tocco

The geological and metallogenic map of the Baccu Locci mine area (Sardinia, Italy)

Abstract Please click here to download the map associated with this article. The study area is in the nappe zone of the Sardinian Variscides in the southeast part of the Island of Sardinia (Italy), and extends between 39°33′14″/9°30′14″ (NW corner) and 39°30′09″/9°35′36″ (SE corner). The area shows a section of the Variscan orogen in Sardinia with three tectonic units that were stacked and folded during the Middle Carboniferous Variscan tectonics. The presented 1:10,000 scale geological map, the cross sections and the 3D models illustrate the complicated tectonic setting of the area, resulting from the polyphasic Variscan collisional evolution as well as from later extensional stages. The geometry resulting from progressive deformation is strongly noncylindrical; it is not balanceable because the polypahsic deformation with different tectonic transport directions and the loss in volume in the different formations occurred under greenschist facies metamorphism. The use of 3D modelling of geological surfaces greatly improved both the map and cross-sections. The Variscan basement of the study area hosts one of the most important mining zones of SE Sardinia (Baccu Locci mine area), which was active until 1961 for the extraction of AsPy, PbS and ZnS. Recent studies also found a noteworthy occurrence of Au. The Baccu Locci mine is assumed to be the eastern part of a mineralized corridor linked with the Variscan shear zone. A metallogenic map of the Baccu Locci mine area at 1:7,500 scale is included in this paper. The primary map associated with this paper actually represents a 4D model (spatial and time dimensions) of ore bodies hosted in a crystalline basement and highlights the overprinting of different paragenetic sequences of mineralizations and their relationships with pre-existing structures.