Economic Geology Vol. 84, 1989, pp. 1277-1292 Tourmalinite-Associated Pb-Zn-Ag Mineralization at Bottino, Apuane Alps, Italy: Geologic Setting,Mineral Textures,and SulfideChemistry MARCO BENVENUTI, PIERFRANCO LATTANZI, Dipartimentodi Scienze della Terra della Universitd di Firenze, via G. La Pira 4, 1-50121Firenze,Italy AND GIUSEPPE TANELLI Dipartimento di Scienze della Terra della Universitd di Napoli: Mineralogia, V. Mezzocannone 8, 1-80138 Napoli,Italy Abstract The Pb-Zn-Ag deposits of Bottino, Italy, are among the most significant in the Apuane Alps (NW Tuscany) mining district and were actively exploited in the past. The orebodies constitute a system of veins hosted withinPaleozoic sedimentary andvolcano-sedimentary sequences. These rocks were metamorphosed in thegreenschist facies (350ø-450øC, 3-4 kbars) during Tertiary Apenninic metamorphism (27-12 Ma). The orebodies are closely associated with tourmalinites andappear to be mostly conformable to the mainwall-rock foliation (S1) that developed during the first regional deformation (Di). Locally, a relic pre-Apenninic foliation is recognizable both in the host rocks andin tourmalinites. The mineralogy of tourmalinites includes variableamounts of tourmaline, quartz, white mica, carbonates, chlorite, apatite, zircon, rutile,pyrrhotite, pyrite,arsenopyrite, and galena. Tourmalinites show a variable bulk-rock chemistry andare consistently enriched in Au, Ag, Sn, and W withrespect to thehost rocks. Tourmaline crystals show variable size and distribution, strong pleochroism, and irregular optical zoning.Their compositions belong to the schorl- dravite series andare similar to tourmalines fromexhalative tourmalinites, whereas theydiffer significantly from granite-related tourmalines. The mineralogy of the ore veins is especially complex. Galena, sphalerite, pyrrhotite,ar- senopyrite, pyrite,chalcopyrite, meneghinite, and Ag-rich tetrahedrite arethe most widespread ore minerals. The occurrence of Ni minerals such as ullmannite andgersdorfflte establishes a nickeliferous character for the Apuane Alpsminingdistrict, in contrast to other districts of the Tuscan metallogenic province. Textural features of the orebodiesand ore minerals, and their inferred correlation with regional-scale deformational events, indicatethat the mineralization at Bottinoresultedfrom a complex, multistage process spanning at leastthe entire time of Apenninic metamorphism. Arsenopyrite geothermometry indicates an evolution of the ore-forming environment from temperatures close to peak metamorphic conditions (•--450øC), decreasing in a later stage to about 350øC. The lateappearance of monoclinic pyrrhotite replacing earlier hexagonal pyr- rhotite indicates that temperatures eventually dropped to <250øC. In earlier literature, the Bottinodeposits were considered to be the productof fluids em- anating froma synorogenic, deep-seated granitic body,the existence of whichhas neverbeen proven. As an alternative hypothesis, we suggest that the mineralization may have resulted from multistage synmetamorphic mobilization andconcentration of metals. Tourmalinites may be interpreted asindicators of pre-Apenninic, premetamorphic boronandmetalenrichment, possibly in an exhalative environment. Theserocks may have been the source bed for the metamorphicore concentration at Bottino. Introduction 'THE Apuane Alps (NW Tuscany, Italy) have been the focus of mineral exploitation since ancient times (Cipriani and Tanelli, 1983; Tanelli, 1983; Cortecci et al., 1985; Tanelli and Lattanzi, 1986). In the Bot- tino-Gallena area,Pb-(Zn)-Ag mineralization was ac- tively exploited especially duringthe 19th century. Production in the years 1860 to 1880 was onthe order of 30 to 100 metrictons/yr Pb, and 500 to 900 kg/ yr Ag. Some production of Pb, Zn, and Ag occurred also in the 1920s. Mining activity was abandoned about20 years ago. The mineralization at Bottino has been widely knownandseveral scientific papers were published during the exploitation of the deposits. The reader isreferred especially to Pelloux (1922), Dessau (1935), and Carmignani et al. (1972) for detailed in- formation on the previous mininghistoryandlitera- ture of the district. The mineralization consists of veinlike bodies hosted by Paleozoic sedimentary and volcano-sedi- mentary rocks, which were affected by the Tertiary 0361-0128/89/963/1277-16$3.00 12 77