Abstract Laterites are regoliths developed under tropical to subtropical conditions and are host to key deposit types, notably bauxites (major sources of Al, derived from weathering of aluminosilicate rocks) and Ni-Co laterites (derived from ultramafic rocks). Research on the western Tethys region, where bauxites and Ni-Co laterites developed during the Mesozoic and Cenozoic, probably peaking at the Paleocene-Eocene thermal maximum when geology, paleogeography, and climate were ideal for the deep weathering of favorable lithologies, is reported in this article. Bauxites were developed on the rocks forming the continental margins to the various branches of the Tethys Ocean and were already forming in the Triassic, whereas the Ni-Co laterites developed on fragments of obducted ophiolite from the Tethys Ocean, which were only uplifted and exposed to weathering after the Jurassic. Residual lateritic bauxites are known in the region but karst bauxites are much more common. Ni-Co laterites are found as residual profiles, ranging from oxide, to clay-silicate, to hydrous-silicate types, but are also represented by distinctive, extensively redeposited clay-oxide ores. This diversity of styles probably reflects differences in topography and uplift history because the deposits all formed within a similar, restricted climatic time window. The bauxite belt extends from Spain in the west, through the type locality of Les Baux in France, and intermittently through the Balkans, Greece, and Turkey to Iran and beyond. Bauxite resources in Europe constitute around 2% of the world’s current known stock. Significant Ni-Co laterites are found in a more restricted geographic area stretching from Serbia to Turkey. The bulk of both Al and Ni-Co production currently comes from Greece, today accounting for around 1% of world production of both Ni and bauxite, and with published resources on the order of 650 Mt @ >50% Al 2 O 3 ; other mines are located in Turkey, Albania, and Kosovo. Ferronickel plants are located in Greece, but also in the Former Yugoslav Republic of Macedonia, and Kosovo. The region has significant potential for the discovery of additional bauxite resources, although they would most likely be karst bauxites, less suited to large-scale mining efforts. Many undeveloped Ni-Co deposits are recorded in the region, with a recent focus to unlock the potential of oxide mineralization using novel hydrometallurgical technologies. Particularly noted is the potential for large low-grade redeposited lateritic Ni-Co-Fe deposits: Mokra Gora in Serbia, for example, has a resource of more than 1 Gt @ 0.7% Ni and 0.05% Co.

Abstract The Iglesiente-Sulcis area in southwestern Sardinia is one of the oldest mining districts in the world, with production dating to pre-Roman times. Exploitation in the district was initially for lead-silver-copper deposits and later for zinc and barium deposits. Most of the deposits occur within Lower Cambrian carbonates and, to a minor degree, in Upper Ordovician metasedimentary rocks. The ores can be subdivided into pre-Hercynian (stratiform/stratabound Zn>Pb>Ba) and post-Hercynian (Pb-Ba-Ag-Cu skarn, vein, paleokarst) deposits. The pre-Hercynian deposits have significantly greater economic importance relative to the post-Hercynian ores. Among the Cambrian-hosted ores, a group of variably graded, syngenetic-early diagenetic massive sulfides (pyrite≫sphalerite≫galena) and barite layers are located at the top of the Nebida Group, where there is a transition from terrigenous clastic rocks to shallow water dolomites. Deposition of these metal sulfides is related to onset of strong tensional tectonics during the Cambrian, which also isolated the carbonate platform. A second group of ores, with a greater Pb/Zn ratio and less pyrite, occurs as void-filling, breccia cement and as late diagenetic replacement bodies in lagoonal limestones of the overlying upper Gonnesa Group, below semi permeable calcareous slates of Middle Cambrian age. Economically less significant Ordovician-hosted deposits (Ba≫Pb) are associated with silicification of host rocks. This mineralization occurs as irregular, void fillings and replacement bodies along an angular unconformity between Cambrian carbonates and Upper Ordovician conglomerates and slates. The metals for the pre-Hercynian stratabound ores were derived from a crustal source, with the lead belonging to the same isotopie province as the lead in the mineral deposits of the southern Alps, Austro-alpine nappes, southern France and northern Spain. Sulfur in barite and sulfides is believed to be derived from a marine, variably reduced, lower Paleozoic sulfate source. Strontium in the Cambrian-hosted barite is believed to share similar source rocks. However, Sr in Ordovician-hostcd barite has a much greater range of values, indicating a distinct episode of mineralization. Other than later (syn- to post-Hercynian) remobilization of ores, ore deposits in the southwestern Sardinian district can be regarded as the result of a combination of favorable sedimentary environments with Cambrian and Ordovician-Silurian tensional tectonics. In fact, most ores are enriched along important tectonic lines which controlled the distribution of the sedimentary facies during the Lower Paleozoic. These tectonic lines have been reactivated many times up to the present.

Abstract The Lower to Middle Cambrian sequence of southwestern Sardinia shows different stages of platform evolution through time, from a ramp to an isolated carbonate platform: (1) terrigenous carbonate homoclinal ramp with algal-archaeocyathan mounds ( Epiphyton/Renalcis ) in the west and terrigenous, shallow-marine to tidal sequences in the east; (2) carbonate terrigenous ramp or rimmed shelf with an ooid shoal complex, prograding toward the west; the back-shoal area contains peloidal mudstones, algal-archaeocyathan biostromes ( Girvanella ), and increasingly tidal deposits (siliciclasts and carbonates) toward the east; (3) isolated platform, aggraded to sea level, with an intra-shelf basin in the southeast and slopes to the north and west; (4) isolated, flooded platform; barriers toward the open sea partly broken down; (5) isolated platform with raised margins and deep interior, often with thick breccia beds in uppermost parts; (6) segmentation and drowning of the platform with deposition of nodular limestones and intercalated limestones and shales; and (7) siliciclastic deposits covering the former platform. Evidence of tensional tectonics (slumping, debris flows, internal breccias, neptunian dykes, intraplatform basins and ponds) is abundant. Subsidence rates, however, are relatively low; the stratigraphic horizons are largely continuous. Rifting terminated by late Early Cambrian to Mid-Cambrian time, when plate-tectonic setting changed to a drift phase.