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Regional and local-scale gold grain and till geochemical signatures of lode Au deposits in the western Abitibi Greenstone Belt, central Canada

By
M. Beth McClenaghan
M. Beth McClenaghan
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1 A 0E8, Canada(e-mail: bmcclena@nrcan.gc.ca)
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Published:
January 01, 2001

Abstract

This paper is an overview of drift exploration methods for lode Au deposits in areas of thin and thick cover of glacial sediments within the Abitibi Greenstone Belt of central Canada. It summarizes a large volume of data produced by government regional surveys and case studies as well as that from industry-led gold exploration programs. Regional till surveys can be used as targeting mechanisms for further Au exploration. Anomalies are defined by a series of samples with elevated Au concentrations that lie along significant bedrock structures, occurring in clusters or as isolated samples in areas of low sample density. Thresholds between background and anomalous Au grain abundances or Au concentrations are variable and depend on location within the Abitibi Greenstone Belt. Case studies around known deposits provide examples of geochemical and mineralogical signatures of Au deposits that can be expected in till down-ice. These serve as sources of information on appropriate sampling methods and size fractions to analyse, and on ice flow patterns, local glacial stratigraphy and suitable till units for sampling. Two methods for measuring the Au content of till are commonly used: (1) a count of visible Au grains and (2) geochemical elemental analysis. Close to source, till contains thousands to hundreds of thousands ppb Au and several hundred Au grains. The Au grains vary from coarse sand to silt sizes and have pristine shapes. The presence of high Au concentrations in till indicates that the ore zones subcrop and that glacial processes have produced Au dispersal trains down-ice.

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Geological Society, London, Special Publications

Drift Exploration in Glaciated Terrain

M. B. McClenaghan
M. B. McClenaghan
Geological Survey of Canada, Canada
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;
P. T. Bobrowsky
P. T. Bobrowsky
British Columbia Geological Survey, Canada
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;
G. E. M. Hall
G. E. M. Hall
Geological Survey of Canada, Canada
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;
S. J. Cook
S. J. Cook
Hudson Bay Exploration and Development Co. Ltd., Canada
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Geological Society of London
Volume
185
ISBN electronic:
9781862394339
Publication date:
January 01, 2001

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