Tephroite from the Val Graveglia metacherts (Liguria, Italy): mineral data and reactions for Mn-silicates and Mn-Ca-carbonates
published: Feb 21, 1991
manuscript accepted: Jul 19, 1990
manuscript received: Dec 18, 1989
ArtNo. ESP147050301002, Price: 29.00 €
Abstract Tephroite coexists with rhodonite and manganoan calcite in the Val Graveglia metacherts, replacing the braunite + quartz (± haematite) assemblages at decreasing oxygen fugacity, as a consequence of circulating CO2-bearing, Ca-rich, hydrous fluids. Tephroite is almost pure phase (99.25 mol % Te) and rhodonite has 82.4 mol % MnSiO3. Later fluid infiltration along fractures resulted in the replacement of the tephroite-rhodonitebearing assemblage by bementite and carbonate, possibly in response to increasing XCO2. In this study, tephroite is chemically analysed by electron microprobe and examined by X-ray diffraction, optical and DTA methods.