Diamond-bearing Kimberlites in Saskatchewan, Canada: The Fort a la Come Case History

Abstract 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 be the main exploration tool in defining pipe locations and sizes. Magnetometer surveys in varying levels of detail have outlined one main cluster and two sub-clusters, the main group being some 10 km by 50 km in size. In excess of 70 individual targets have been interpreted from the magnetics as probably representing kimberlites. The size range of the individual magnetically-defined bodies is between 1 ha and 74 ha. Proof that the magnetic anomalies were kimberlite intrusions came in 1989 when each of seven test holes, all drilled on different targets, intersected the potential diamond host rock. The majority of the targets tested were diamond-bearing, with the indicator mineral chemistries suggesting that both peridotitic and eclogjtic diamond parageneses could be expected. To date, 18 individual kimberlite bodies have been drill-tested. A total of 39 bulk samples, amounting to 1861 (representing 3601 of theoretical sample recoveries) were processed in 1990 and 1991. One hundred and sixty diamonds were recovered, averaging 0.04 carats in weight, the largest being 0.6 carats. Most of the bulk sample grades are less than 2 carats/100 t; only three bulk samples have higher grades, the best being approximately 10.5 carats/100 t. The diamonds are predominantly gem-quality stones.
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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: 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...
Publication: Exploration & Mining Geology
Author(s): IAN NICHOL, O.P. LAVIN, M.B. McCLENAGHAN, C.R. STANLEY
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: 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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