THE COMPOSITION OF BASE METAL MINERALIZING AND NON-MINERALIZING FLUIDS, PINE POINT, NORTHWEST TERRITORIES, CANADA
The main ore stage sulfides include galena, sphalerite, marcasite and pyrite. Fluid inclusion data from ore stage sphalerites and saddle dolomites indicate the mineralizing fluids are low temperature (<100°C), saline brines (25-35wt% CaCl2 + NaCl equivalent), with high Ca:Na ratios (20:1). Texturally late stage calcite, native sulfur and bitumen are also commonly observed in the deposits. Calcite is formed from a similar temperature, but lower salinity NaCl-CaCl2 fluid (15wt%).
Halogen, major and trace cation data were analysed from sphalerite, saddle dolomite and late calcite from the Pine Point deposit and nearby Westmin property. The halogen compositions of the mineralizing fluids indicate that the bulk of the fluids originated from highly evaporated seawater. The Na, K and Li compositions of the fluids have been modified on the flow path, possibly by interaction with feldspar-bearing sequences. The Ca, Sr and Ba compositions of the fluids are significantly higher than the concentrations expected for evaporated seawater. Ca has been added to the fluids either by dolomitization or by the dissolution of gypsum on the flow path.