Open File Report 1994-21

Open File Report 1994-21

OFR 1994-21

Reconnaissance Mineral and Geochemical Survey with Emphasis on Northern Alberta; Year 2

Author(s) Fenton, M.M. Pawlowicz, J.G. Dufresne, M.B. Date 1994-06-30

The overall objectives of the project are: to determine the regional variations to be expected in the indicator minerals, geochemistry and texture of till to assist exploration by the mineral industry for diamondiferous kimberlite and lamproite, gold placers, and other minerals, and to determine the provenance of at least the surface till in northern Alberta. This is the interim report for the second year of a three year project.

Fieldwork focused principally on northwestern Alberta (north of 55 and west of 115 degrees) with a short visit to the Marguerite River - Firebag River area of NE Alberta. Sixty two surface till sample sites and three stream sediment sample sites were visited. Six coreholes were augered in the High Level - Fort Vermilion region. Selected surface and auger corehole samples collected by the staff from the associate project on the Quaternary Stratigraphy and surficial geology in the Peace River Winagami regions (M93-04-35) were also analysed. The samples were also analysed for indicator mineralogy and matrix geochemistry.

At present, minerals indicative of kimberlites, such as G1 orG2 garnets and picroilmenites, are rare. However a few samples in the Peace River area contain G9 or G11 garnets and chrome diopsides which possibly are indicative of peridotitic source rocks. The most common and perhaps the most important group of indicator minerals that have been recovered from the northern Alberta tills, are the low iron and high magnesium G3 and G5 garnets. These may be indicative of eclogitic source rocks, and some of these could have been derived from rock formed within the diamond stability field based on a comparison of their chemical composition with that of diamond inclusion eclogitic garnets obtained from elsewhere in the world. No picroilmenites of major interest were recognized in the grains analysed so far.

Although the sample distribution in northern Alberta is irregular three geographic trends, based on the number and quality of eclogitic and other indicator minerals, have been recognized in northern Alberta. These include: (a) a southwesterly trend from just north of the townsite of Peace River to the Birch Hills northeast of Grande Prairie. (b) a southerly trend form the lower Wabasca River to the Loon River, and a southwesterly trend in the Marguerite River to Fort MacKay area.