Structural and Magmatic Controls on Late Variscan Metallogenesis: Evidences from Southern Sardinia (Italy)

The late Variscan post-collisional events in Sardinia generate two main types of ore deposits: (1) intrusion hosted/related deposits; (2) "orogenic", structurally-controlled deposits associated with shear zones. The former include Pb-Zn (Ag, Cu), Ni-Co-As-Bi and F-Pb veins, W and Sn veins, Mo greisens, Pb-Zn-Cu skarns; the latter are characterised by Au +/- Sb +/- W associations, and As-Zn-Cu-Pb-Ag veins, formed at different structural levels. Intrusion-hosted/related ores are relative to two intrusive phases: an early pre-300 Ma phase (mostly granodiorites and monzogranites), and a later 288-286 Ma phase (F-bearing leucogranites). New geological and radiometric data suggest time/space and genetic association of the "orogenic" mineralisation to the pre-300 Ma magmatic phase. The 304-286 Ma interval may be assumed as the age of the Variscan metallogenic peak in southern Sardinia. Partial melting of discrete portions of the lithosphere during late Variscan post-collisional extension should be regarded as the most reliable source of metals.