Distribution of Presqu'ile dolomite in the Great Slave Plain, Northwest Territories

This study was initiated to map out the extent and gross thickness of Presqu'ile dolomite in the Great Slave Plain of the Northwest Territories. Presqu'ile dolomite refers to a diagenetic replacive dolostone, often containing void- and fracture-filling white, coarse-crystalline sparry hydrothermal or saddle dolomite commonly associated with the Pine Point lead-zinc deposits. The lead-zinc mineralization process is still a matter of some debate; the distribution of Presqu'ile dolomite could yield some clues. It could also be useful for oil and gas exploration because of the high permeability of this dolomite. A prominent northeast-southwest trend of thick Presqu'ile dolomite appears to be centered between the inferred Tathlina and Hay River fault zones. Presqu'ile dolomite appears to be most abundant close to surface; it does not occur below depths of 850 m. No Presqu'ile dolomite was found below the Cretaceous cover in the study area.