The Optimization of Geochemical Exploration for Gold using Glacial Till

Abstract Exploration in most areas of Canada has to contend with problems posed by glacial overburden. In many areas exploration for gold has been based on the sampling of tills, frequently by deep overburden drilling, and analyses of heavy mineral concentrates. Notwithstanding the significant role that till geochemistry has played in the discovery of some important gold deposits over the last few years, increased appreciation of the nature of the glacial history and stratisgraphy and the character of gold within till has led to the recognition of a number of ways whereby the effectiveness of exploration can be improved upon.
In order for till geochemistry to be useful in exploration, a number of conditions must be fulfilled, including:
1. mineralization, or alteration halo related to mineralization, subcropping at the bedrock/over-: burden interface;
2. glacial erosion and dispersal of a recognizable signature of mineralization into the glacial
sediments;
3. preservation of glacial sediments containing this geochemical component (trace metal or mineral) , at positions subsequently selected for sampling (normally drill sites);
4. correct identification of specific till units and associated ice movement history;
5. collection of adequately large and representative samples;
6. appropriate sample preparation and processing;
7. appropriate geochemical analysis; and
8. correct data processing and interpretation.
While we have no control over the first two geological conditions, and only limited control over till availability, we can control the quality and thoroughness of sampling, sample identification, sample preparation, analysis and interpretation. In particular attention needs to be focused on obtaining a large enough sample to be adequately representative, an unbiased sample must be collected, together with appropriate sample processing, analysis, data processing and interpretation. It is considered that by modifying or extending existing approaches to gold exploration, the chances of exploration success can be increased. In particular, analysis of both the heavy mineral and minus 63 /mi fractions of till is recommended because gold in till may occur in different size fractions.
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Summary: The Geological Society has its own quarterly journal called Exploration
and Mining Geology, for the publication of Canadian and international papers on
applied aspects of mineral exploration and exploitation, including mineral
deposit geology, geochemistry, and geophysics, mining geology, mineral resource
appraisal and estimation methods, environmental geology, and case histories. The
editor of the journal is Jeremy P. Richards
Publication: Exploration & Mining Geology
Issue: 4
Volume: 1
Year: 1992
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Summary: During the last two decades lamproites have joined kimberlites as the only two known primary sources of economic quantities of diamonds. This paper contrasts the petrography, primary and xenocrystic mineralogy and pipe geology of these petrogenetically separate rock types. The petrographic discrimination of kimberlites and lamproites from each other, as well as other rock types found during diamond prospecting, is discussed. Kimberlites and lamproites can be classified texturally and...
Publication: Exploration & Mining Geology
Author(s): BARBARA H. SCOTT SMITH
Issue: 4
Volume: 1
Year: 1992
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Summary: The early identification of a kimberlite dyke and the occurrence of pyrope garnet grains along a section of the Munro Esker north of Kirkland Lake encouraged the search for kim-berlites. Subsequent exploration using data from aeromagnetic surveys completed for the Kirkland Lake Initiatives Program (KLIP) resulted in the discovery of five kimberlite diatremes in the area north of Kirkland Lake and another one to the south. These are only a portion of the cluster of pipes found so far that...
Publication: Exploration & Mining Geology
Author(s): J.J. BRUMMER, D.A. MacFADYEN, C.C. PEGG
Issue: 4
Volume: 1
Year: 1992
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Summary: The first record of a kimberlite found in Canada (1946) was the identification of thin dykes intersected while drilling for gold in Michaud Township, Ontario.
Sampling of the Munro Esker (1964) in the Kirkland Lake area, Ontario, by the Geological Survey of Canada identified the occurrence of detrital grains of pyrope garnets along a length of 35 km of the 113 km tested. A search for the source of the garnets resulted in the identification (1968) of a narrow subsurface kimberlite dyke in the...
Publication: Exploration & Mining Geology
Author(s): J.J. BRUMMER
Issue: 4
Volume: 1
Year: 1992
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Summary: The Matheson area of northeastern Ontario is of great interest for mineral exploration because of its geological similarities with the adjacent Timmins, Kirkland Lake and Larder Lake gold camps. Exploration in the area, however, is hampered by the presence of an extensive and thick cover of glacial sediments. For this reason, till geochemistry has become an important exploration method. The Ontario Geological Survey's Black River-Matheson (BRiM) reconnaissance till sampling project, carried...
Publication: Exploration & Mining Geology
Author(s): M.B. McClenaghan
Issue: 4
Volume: 1
Year: 1992
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Summary: This paper documents the 1988 discovery and subsequent evaluation (to 1991) of diamond-bearing kimberlites in the Fort a la Corne area, Saskatchewan, by Uranerz Exploration and Mining Limited. Cameco Corporation began participating as a joint venture partner (50%) in mid-1989. The first indications that kimberlite-type intrusions might exist in the area came from Geological Survey of Canada aeromagnetic maps. Because of the overburden thickness (over 100 m), magnetometer surveys continue to...
Publication: Exploration & Mining Geology
Author(s): KLAUS LEHNERT-THIEL, ROLAND LOEWER, RODNEY G. ORR, PHIL ROBERT SHAW
Issue: 4
Volume: 1
Year: 1992
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Summary: The Argyle diamond mine is located in the Kimberley region in the northern part of Western Australia at approximately 16°43'S, 128°23'E in subtropical bush/shrub savannah. The 46 ha (113 acres) pipe is situated in the Halls Creek mobile zone, which was cratonized about 1800 Ma ago and adjoins the Kimberley Block, a plateau upheld by Early to Middle Proterozoic rocks underlain by presumably Archean basement. The crater and upper pipe zones of the diatreme have been preserved within tilted and...
Publication: Exploration & Mining Geology
Author(s): A.J.A. JANSE
Issue: 4
Volume: 1
Year: 1992
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