A study of fluid inclusions in sulfide and nonsulfide mineral phases from a carbonate-hosted Zn-Pb deposit

This paper reports on a detailed fluid inclusion study of synore (sphalerite, calcite) and postore (calcite, fluorite, quartz, barite) mineral phases at the Gays River Zn-Pb deposit (2.4 Mr, 8.6 % Zn, 6.3 % Pb), Nova Scotia, Canada. The deposit s hosted by dolomitized Visran carbonate rocks, in the basal part of the Windsor Group, that formed during a marine transgression on terrestrial clastics of the Tournaisian Horton Group. Mineralization is dominantly ofreplacement style, with lesser porosity infilling, and mainly occurs in the fore reef of a carbonate bank, the shallow ater equivalent ofthe laterally extensive, laminated algal and bituminous Macumber Formation. Paragenetically, constant volume dolomitization f the host rock is followed by euhe-dral, manganiferous dolomite cement, hen sphalerite and galena. Syn- to postore calcite with trace amounts of barite, fluorite, and quartz, occlude the remaining porosity. Fluid inclusions types include: (1) aqueous, L rich _+ solids, including halite, (2) methane, (3) H,20-CO.2, (4) monophase L and V types, and (5) liquid petroleum _ aqueous phase. Type I inclusions are most abundant, types 2and 3 are rare, and type 5 are postore. Type 4 inclusions are mostly related to postentrapment changes (e.g., necking). Thermometric data indicate that the mineralizing fluids were high-salinity, NaC1-CaC1.2-H.20 brines with 20 to 28 wt percent NaC1 equiv. Hydrohalite ice-melting relationships indicate considerabl