Special Report 009

Special Report 009

SPE 009

The Geological and Geochemical Setting of the Mid-Cretaceous Shaftesbury Formation and Other Colorado Group Sedimentary Units in Northern Alberta

Author(s) Dufresne, M.B. Eccles, D.R. Leckie, D.A. Date 2001-06-01

The geological setting of the mid-Cretaceous Shaftesbury Formation and other Colorado Group sedimentary rocks is similar to many productive metalliferous districts of the world, where formation or emplacement of mineral deposits is often partially controlled by one or more of coeval volcanism, extensional faults or fracture zones associated with regional fault systems and arches, and other structural zones that transect either the basement or overlying Phanerozoic cover rocks. A variety of minerals and metals, including diamonds in kimberlitic pyroclastics (e.g., Fort a la Corne area, Saskatchewan), and base and precious metal-bearing sulphidic horizons (e.g., McIvor River area, northern Alberta) have been found in the Shaftesbury Formation or its age equivalent rocks. During deposition of the Cretaceous Colorado Group sediments, and particularly during deposition of the Shaftesbury Formation, there was localized deposition of volcanic deposits from local centers in Alberta (e.g., Crowsnest Formation of southwest Alberta) and abundant bentonic horizons throughout the Shaftesbury Formation across much of Alberta. Therefore, because Shaftesbury Formation rocks display potential for hosting selected types of ore deposits (e.g., diamondiferous pyroclastics and diatremes; stratiform lead-zinc � precious metal-bearing shales; disseminated sediment-hosted gold; and volcanogenic massive sulphides), a rigorous geological/geochemical assessment is warranted.

Dufresne, M.B., Eccles, D.R. and Leckie, D.A. (2001): The geological and geochemical setting of the mid-Cretaceous Shaftesbury Formation and other Colorado Group sedimentary units in northern Alberta; Alberta Energy and Utilities Board, EUB/AGS Special Report 9, 654 p.