| Abstract: | In contrast to the granitoids of the ultrametamorphic basement of northern Sardinia, Hercynian intrusive granites exist in southern Sardinia in low-grade metamorphic surroundings. In this area, endogenous cassiterite-bearing vein deposits and molybdenumtungsten mineralizations occur adjacent to the granite massifs of the Quirra (3), Arburese (4) and Monte Linas (5). In comparison, the intrusives of the Sarrabus (1) and San Vito (2) seem to be barren.Petrochemically these granitoids represent a spatial and temporal suite of calc-alkaline magmas with biotite-muscovite granite as a latest product of the magmatic evolution. The formation of the massifs was governed mainly by in situ differentiation. Only locally is there evidence of emanative differentiation processes which also caused post-magmatic metasomatic alteration of the granite and the formation of the hypothermal mineralization.According to their trace element geochemistry there exist normal and anomalous leucogranites. Thus, the Quirra (3), Monte Linas (5) and Arburese (4) massifs exhibit the highest grade of geochemical specialization. However, compared with highly tin-bearing granites in other regions, these massifs show only a slight specialization. Structural arguments suggest that the Arburese Massif (4) could have lost its higher specialized cupola and some possible deposits by erosion. In addition, only the drainage system of the Monte Linas Massif (5) exhibits anomalous tin concentrations in the alluvial sediments of recent channels. |
