Geoscience and Exploration

Hydrothermal Fluid Sources and Pathways in a World Class Mississippi Valley-Type Lead-Zinc District: Pine Point

Thursday, November 22, 2018 - 15:00 Theatre 1


M. Steele-Macnnis (Presenting)
University of Alberta

M. Szmihelsky
University of Alberta

S. Clemmer
Pine Point Mining Limited

H. Falck
NWT Geological Survey

R. Adair
Osisko Metals Incorporated

Pine Point is a world class carbonate-hosted lead-zinc district, comprising at least 100 known occurrences of lead-zinc mineralization, spanning over 1600 km2. Lead-zinc mineralization at Pine Point is hosted in Devonian reefal carbonate rocks. The district constitutes a major fraction of Canada's total lead and zinc potential, and accounted for a significant proportion of the total lead and zinc produced in Canada during its production years. The mineralizing system at Pine Point is thought to reflect regional-scale flux of sedimentary-derived brines. However, several key questions remain as to the ultimate sources of fluids, metals and sulfur, and the fluid pathways that led to focusing at Pine Point.

The Pine Point district contains two main types of mineralization: "tabular" bodies, which are stratabound and karstic, and "prismatic" bodies, which are cross-cutting, chimney-like pipes with breccia features. The spatial and genetic relationships between these two types are not entirely clear, as some of the prismatics are apparently rooted in tabular karst, whereas others are not. The geometries and spatial relationships between these two types give rise to the interpretation that mineralizing fluids derived from a common source variably made use of both stratabound karstic horizons and structurally controlled breccia pipes along their flow path. Nevertheless, questions remain as to whether regional fluid flux primarily followed the host carbonate package, or involved deeper circulation that may have accessed the carbonate section via discordant fluid pathways, perhaps represented in part by the prismatics. Available data indicate multiple fluid sources represented in different paragenetic stages, which may imply a role of fluid mixing in sulfide deposition. In addition, lead-zinc mineralization tends to be spatially associated with marcasite, although questions remain as to the paragentic relationship between marcasite and lead-zinc sulfides.

This presentation will provide a summary of the geologic context and hydrothermal features of the Pine Point District, and an overview of our ongoing geochemical studies of mineralizing fluid systems and paragenesis in both tabular- and prismatic-style mineralization. The presentation will highlight some of the interesting mineralogical and geochemical features of Pine Point and provide some preliminary hypotheses on the physical and chemical processes governing lead-zinc mineralization here and in general.