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Book Chapter

Sampling techniques

Published:
January 01, 2001

Abstract

Till is a favoured sample medium for locating mineral deposits in glaciated shield terrains of Canada and Fennoscandia because it best reflects the primary composition of the bedrock source area. In the sampling phase, an important and costly component of till surveys, sample density, sample depth and sample method must be chosen according to the needs of the exploration program. Surface till sampling methods in forested areas differ from those used in permafrost terrain. However, in both areas, concentrations of labile ore minerals and their products of decomposition can be detected in the fine fraction (< 2 mm) of weakly oxidized till. In thin drift-covered areas, till samples are collected by hand excavation or trenching at < 5 m depth. In areas of thicker drift, more expensive methods such as reverse circulation rotary drills, rotasonic drills and portable drills are used to collect till samples at depth and to determine lateral and vertical variations in till geochemistry. Laboratory methods are an essential part of till geochemical surveys. The choices of the size fraction and analytical methods are determined by the nature and composition of the expected bedrock target, and by costs.

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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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