CGRG Bibliography of Canadian Geomorphology
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Author : Barnett, P.J.; and Crabtree, D.C
Date : 2007.
Title : Glacial dispersion of a lamprophyric heterolithic breccia from the Engagement zone, Wawa, Ontario, Canada.
Publication : Yellowknife 2007. Annual Conference of the Geological Association of Canada - Mineralogical Association of Canada. May 23-25, 2007. Yellowknife, Northwest Territories, Canada.
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Abstract
A study was undertaken to determine if till sampling and analysis could be used for the exploration of diamonds hosted by Archean rocks in the Wawa area; some of the oldest diamond deposits in the world. The harder, relatively more erosion-resistant Archean diamond-bearing rocks do not produce the same indicator mineral signatures as the kimberlitic rocks that are the common target of diamond exploration in Canada. The area of the West Timmins Mining Inc. Engagement zone was selected for study as the lamprophyric heterolithic breccia exposed there is diamond-bearing, its mineralogy has been studied, it is easily accessible and there is a thick cover of till in and around the occurrence to sample. The direction of ice flow associated with the deposition of the till in the area was toward the south (175°-185°). Till samples for heavy mineral concentrate (HMC) analysis (methylene iodide, S.G. 3.2), till matrix geochemistry and pebble lithology studies were collected at 11 sites up-ice flow, over and down-ice of the Engagement zone. HMC samples collected from till contained few kimberlite indicator minerals (<18 grains/10 kg of sample). However, samples closest to the diamond-bearing heterolithic breccia contained the greater amounts. Heavy minerals that appear to indicate the presence of the breccia include: pyrope garnet, chromite, low-chrome diopside, forsterite, chalcopyrite, pyrite, gold (total and pristine grains) and goethite. For all heavy minerals studied the glacial dispersal trains are short. The best defined train is of gold grains that extends for more than 400 m in length. Actinolite, an S.G. 3.2 light mineral, is abundant in the breccia and the dispersion of this mineral is being investigated. Geochemical analysis of the fine fraction (<0.74 mm) of till matrix samples returned elevated levels of in Cr, Ni, Mg and Zn (ICP-MS) in the immediate vicinity of the Engagement zone. The grain-size distribution of the till matrix samples changes down-ice flow of the breccia and may have promise as an exploration method in locating diamond-bearing Archean rocks.
Bibliography of Canadian Geomorphology