N. Jb. Miner. Abh. 180 2 149 –169 Stuttgart, Juli 2004 Bi–Ag-bearing tetrahedrite-tennantite in the Kapsalina copper mineralisation, Thasos island, Northern Greece M. Vavelidis and V. Melfos, Thessaloniki With 10 figures and 3 tables Vavelidis, M. & Melfos, V. (2004): Bi–Ag-bearing tetrahedrite-tennantite in the Kapsalina copper mineralisation, Thasos island, Northern Greece. – N. Jb. Miner. Abh. (180): 149–169; Stuttgart. Abstract: The mineralogy, chemistry and fluid inclusions of the Bi–Ag-copper miner- alisation of the Kapsalina area, at the southwestern part of the Thasos island, is studied for the first time. The ore mineralisation is hosted in quartz veins and consists mainly of chalcopyrite and pyrite, as well as bismuthinite, Bi–Ag-bearing tetrahedrite-tenna- tite and gersdorffite. The ore bodies contain up to 740 ppm Ag. Tetrahedrite contains Bi up to 2.98 wt% and Ag up to 2.05 wt%, while tennantite is poorer in Bi (up to 1.18 wt %) and Ag (up to 1.24 wt %). Calculation of the cell sizes of fahlores show that they increase with the increasing of the Bi and Ag contents. The microthermometric study shows that the mineralisation was formed at temperatures varying mainly from 120 to 280 ˚C, with a peak at 200 ˚C. The pressures of the hydrothermal fluids are estimated between 10 and 90 bars and indicate that the mineralisation was formed in a shallow depth. A mixing between ascending hydrothermal fluids and downward migrating di- lute meteoric water is probably the main process which caused the mineralisation de- position. Key words: tetrahedrite, tennantite, chemical composition, bismuth, cell size, fluid in- clusions, gersdorffite, Thasos island, Greece. Introduction Tetrahedrite-tennantite solid-solutions, known as “fahlore” group, are the most widespread among all sulphosalts. Their chemical composition and optical pa- rameters have been studied by many authors, such as Mishra & Mookherjee (1991), Vavelidis & Melfos (1997), Gregurek & Raith (1997), Arlt & Di- amond (1998), Trudu & Knittel (1998), Foit & Ulbricht (2001), Sack et al. (2002). Many others, among them Skinner et al. (1972), Tatsuka & Mo- rimoto (1977), Johnson et al. (1988), Karup-Møller & Makovicky (1999), DOI: 10.1127/0077-7757/2004/0180-0149 0077-7757/04/0180-0149 $ 5.25 © 2004 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart