麻豆传媒

听

The Smithfield (also Leadville) deposit (45^o14' North Latitude and 63^o04' West Longitude) is an irregular ore body composed predominantly of galena, sphalerite and pyrite distributed in brecciated carbonates of the Macumber and Pembroke members near the contact of the Mississippian Windsor Group with the disconformably underlying Horton Group, a predominantly clastic unit. Pyrite-rich ore is locally associated with poorly consolidated sands and the drill core recovery has been extremely poor. The observed features of the deposit suggest that it can be classified as a structurally-disrupted Mississippi Valley type deposit.

Homogenization temperatures of fluid inclusions in sphalerite, calcite and barite suggest that the minimum temperature of crystallization of these minerals was 140oC. Preliminary oxygen and carbon isotope data for calcite indicate values of 20.8 O18SMOW and -5.37 C13PDB respectively, similar to carbonates that have undergone mild metamorphism and suggest the alteration effects of hydrothermal fluids have lowered original O18 and C13 values of the primary limestones. The isotopic values determined for calcite are comparable with those reported for the Salton Sea geothermal field.

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