Controls on Fluid Flow Systems in Northern Alberta as Related to MVT Mineralization: A Contribution to the Carbonate-Hosted Pb-Zn (MVT) Targeted Geoscience Initiative

Large-scale fluid migrations control the mobilization, transportation and mineralization events that form Mississippi Valley-type (MVT) lead-zinc ore districts within a basin. Therefore, an analysis of the favourable features and components that control fluid flow related to possible MVT mineralization in the Alberta portion of the Western Canada Sedimentary Basin allows for the delineation of high probability areas for exploration.

For northern Alberta, the potential flow mechanisms responsible for MVT mineralization are reviewed, and the literature about past and present flow systems is summarized. Definition of the regional hydrostratigraphic framework and associated permeability values show that, the Keg River Formation, Presqu'ile barrier complex and Grosmont Formation represent the most favourable conduits for MVT ore-forming fluids in northern Alberta. Within these more prospective rock packages, more localized conduits of focused fluid flow, such as faults, breccias, shear zones, structural highs or stratigraphically thick to thin zones, have been identified and evaluated in the context of prospectivity for MVT mineralization. Some examples include the Great Slave Lake Shear zone and the Peace River Peace River arch area where there are a large number of pre-Carboniferous faults. As well, along the south-eastern portion of the study area some large faults are also associated with local structural highs. Lithogeochemical analyses of basement rock, a potential source of MVT metals, show an area of coincident high Pb and Zn concentrations east of the Peace River Arch and south of the Great Slave Lake shear zone in the Ksituan region. Finally, mapping of formation water salinity in the Elk Point and Beaverhill Lake Groups identified high salinity water (>150 g/l C1)needed for metal-mobilization around the Peace River Arch in the Beaverhill Lake Group and along the edge of the Prairie Evaporite in the Elk Point.

In conclusion, investigation of hydraulic heterogeneities, formation water salinity and metal sources suggests that around the Peace River Arch, along the Great Slave Lake Shear zone, between 118� and 116�W and at the margin of the basin, between 56.5� and 57.5�N would be good target areas for MVT exploration in northern Alberta.