CGRG Bibliography of Canadian Geomorphology
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Author : Hall, G.E.M.; Hamilton, S.; McClenaghan, B.; and Cameron, E.M.
Date : 2004.
Title : Seeing through thick glacial overburden with geochemistry.
Publication : 49th Annual Meeting of the Geological Association and the Mineralogical Association of Canada. May 12-14, 2004. Brock University, St. Catharines, Ontario.
Issue :
Page(s) :
Abstract
Cross Lake, VMS (Zn-Cu-Pb-Ag) mineralisation of Archean age, continues to be a prominent site for studying partial leach geochemical signatures in near-surface soils and their genesis. Located ca. 50 km southeast of Timmins in the Abitibi Greenstone Belt of Ontario, this deposit is hosted by felsic pyroclastic rocks and is covered by thick glacial sediments (ca 8 Ka) to a depth of 30-50 m. It is currently the focus of an OMET (Ontario Mineral Exploration Technology)-funded project carried out by the Geological Surveys of Canada and Ontario. Two lines, Lines 6 and 40, studied in detail, provide the different surficial terrains typical of the region: clay, sand and peat. On Line 6, gleysolic soils formed on silty-clayey glaciolacustrine sediments, whereas on Line 40, podzolic soils formed on sandy glaciofluvial sediments. A trench, 200-300 m long, was centred over mineralisation on each line and samples taken every 5 m along its length. Samples (O, Ah, Ae, B) were collected with depth at 10-cm intervals, from surface to ca. 70 cm. The soils have been analysed for 50-60 elements following aqua regia, Enzymeh leach, ammonium acetate (at pH 5 and 7) and weak HCl digestions, and for various other parameters in addition to pH and oxidation-reduction potential (ORP). Principal component analysis helps to group the element patterns according to lithology, nature of terrain (e.g., reduced environments in water-saturated vs highly oxidised in sand), soil-forming processes, atmospheric deposition and the effects of the "reduced chimney" over oxidising mineralisation. Lead isotope analysis of partial extractions carried out on key samples indicates that this element has indeed moved from mineralisation through the glacial sediments to the near-surface. This presentation will focus on differentiating this response, due to element migration from the deposit at depth, from others such as those caused by terrain changes.
Bibliography of Canadian Geomorphology