Susan R. Eaton

Dartmouth N.S.

Fluid inclusions in post-ore fluorite from the base metal deposit in Carboniferous carbonates at Gays River, Nova Scotia, homogenize at a mean temperature of 142 + 8^oC. Calcite in the deposit crystallized earlier, at a mean homogenization temperature of 172 + 2^oC. Freezing experiments indicate that the trapped hydrothermal fluids contained from 17.0 to 20.4 weight percent dissolved salts, a large proportion of which is NaCl.

Samples from the fluorite occurrence in Lower Ordovician carbonates at Boat Harbour, Newfoundland yield a mean homogenization temperature of 143 + 16^oC. The heavily saline hydrothermal solutions contained from 20.4 to 21.2 weight percent dissolved salts of predominantly NaCl composition.

The above homogenization temperatures and salinities are comparable with those reported for some Mississippi Valley type deposits, and enable speculation on the properties of the hydrothermal solutions during the late stages of mineralization in the two study areas. The conditions of fluorite deposition in carbonate environments can be approximated, on the basis of new experimental data, by the solubility of fluorite in the hydrous system NaCl - CaCl₂ - MgCl₂.

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Pages: 147
Supervisors: Marcos Zentilli