Open File Report 1994-06

Open File Report 1994-06

OFR 1994-06

Mapping and Resource Evaluation of the Tertiary and Preglacial Sand and Gravel Formations of Alberta

Author(s) Edwards, W.A.D. Scafe, D. Date 1996-03-31

The objectives of the project are to describe and correlate preglacial deposits, evaluate the mineral aggregate and placer gold potential of preglacial deposits, and identify diamond indicator minerals in preglacial deposits. Preglacial deposits are valuable sources of mineral aggregate with an annual production of about $50 million and are a source of by product placer gold worth an additional $1 million annually. Locating preglacial deposits and developing a stratigraphy will identify future aggregate and gold resources and facilitate the location of diamond-bearing intrusives.

A total of 221 preglacial deposits have been identified. Fifty seven samples were collected for grain size analyses, petrographic analyses, placer gold measurement, and indicator mineral identification. Nineteen crushed gravel samples were taken for Petrographic Number analyses. Forty one deposits were described in the field or from the literature.

The preglacial deposits are divided into six groups. These groups are based on location, lithologic similarity and gold content. The group should reflect the source area of the rocks and minerals and the extent of the fluvial basin. The deposits also are divided into four stratigraphic units based on age and elevation. These units are: the Cypress Hills Formation and equivalents (about early Oligocene), the Hand Hills Formation and equivalents (about Pliocene), the Upland Gravels (Pleistocene?), and the Saskatchewan Sands and Gravels (late Wisconsinan). These units reflect the erosional history of the plains and facilitate cross-group correlation.

Ninety three deposits have mapped (published) mineral aggregate potential. Two deposits are unmapped but have aggregate potential. The other 126 deposits have little potential or await assessment. Seven crushed gravel samples have been analyzed: six are above average in hardness and one is average.

Placer gold values have been determined for samples from all groups. Samples from central Alberta (Group 3/4) and northwestern Alberta (Group 6) have values that are extrapolated to exceed 50 oz of gold per 100,000 tons of sand and gravel processed. Garnet, chromite, and picroilmenite with potential diamond affinities were found in samples from the Edmonton region. Chrome diopsides were found in the Peace River region but the grain compositions are yet to be substantiated by microprobe analyses. For the final report, the available mineral aggregate potential, gold, and microprobe data will be presented.