SULFUR ISOTOPES, IRON CONTENT OF SPHALERITES, AND ORE TEXTURES IN ANVIL ORE BODY, CANADA

The Anvil ore body is a massive strata-bound lead-zinc sulfide deposit enclosed in regionally metamorphosed Cambrian (?) sediments. An Upper Cretaceous granitic mass, the Anvil batholith, intrudes the sequence and abuts the ore body. The FeS content of sphalerites varies from 10 to 18 weight percent with a mean of 14.9. Highest values are associated with a pyrite-pyrrhotite-marcasite facies; they occur adjacent to the intrusion and extend outward in a zone confined to the central and upper part of the ore body. Lower values occur in the peripheral parts of the ore body, where pyrite is the only significant iron sulfide. Sulfur isotope analyses on coexisting phases gave δ34S values averaging +21.7 for pyrite, +21.2 for sphalerite, and +18.3 for galena. In all samples coexisting minerals have values with pyrite > sphalerite > galena, indicating an approach to isotopic equilibrium. These data support the interpretation of the ore body as a metamorphosed pre-Upper Devonian deposit, with sulfur derived from contemporaneous seas. The isotopic equilibration temperature is calculated to be about 300°C and the iron content of the sphalerite associated with pyrrhotite and pyrite suggests a pressure of slightly less than 2 kilobars. © 1974 Society of Economic Geologists, Inc.