Sm–Nd fluorite dating of Proterozoic low-sulfidation epithermal Au–Ag deposits and U–Pb zircon dating of host rocks at Mallery Lake, Nunavut, Canada
The Mallery Lake area contains precious metal-bearing quartzchalcedony stockworks that are pristine examples of ancient low-sulfidation epithermal deposits. Fluorite extracted from these epithermal deposits define a SmNd errorchron age of 1434 ± 23 Ma mean square of weighted deviates (MSWD) = 4.8. This date is interpreted to have age significance because (1) a simple linear trend does not exist between the 143Nd/144Nd ratios of the fluorite with respect to their 1/Nd concentrations as would be expected for mixing of two geochemical end members; (2) microthermometric studies indicate that the fluorite analysed in this study has an intimate association with a single high-salinity, calcic brinal fluid; and (3) the age determined from seven fluorite samples extracted from a single outcrop location yielded an identical age result (1434 ± 60 Ma; MSWD = 5.5) compared to the fluorite composite. Rhyodacites of the Pitz Formation and syenites from the Nueltin suite (intrusive equivalent to the rhyodacites) are th...