New occurrence of deerite in the western Alps

Deerite has been found in the Cu-Fe sulfide deposit of Viafiorcia, Western Alps, associated with the Piemonte ophiolite nappe. This hydrous, ferrous, ferric silicate occurs together with Na-amphibole, stilpnomelane+/- white mica, albite and carbonate, and with pyrite, chalcopyrite, bornite, pyrrothite, magnetite +/- sphalerite, mackinawite, linneite, tennantite, chalcocite, digenite and covellite within a post-Triassic silica-rich deposit above a flattened lens of metagabbro and minor serpentinite which is interbedded in the calcschist sequence. This Cu-Fe-Si deposit is believed to have formed by precipitation from a hydrothermal system occurring in the extensional Piemonte margin. Electron microprobe analyses (three points) of deerite yield the following structural formula: (Mg0.87Fe2+ 11.23Mn0.15)12.25(Fe3+5.95Al0.18)6.13Si11.72O39.78(OH)10.2