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Using hyperspectral imaging to vector towards mineralization at the Canadian Malartic gold deposit, Québec, Canada

Published on May 1, 2019in Ore Geology Reviews 3.39
· DOI :10.1016/j.oregeorev.2019.102945
Philip Lypaczewski2
Estimated H-index: 2
,
Benoit Rivard33
Estimated H-index: 33
+ 4 AuthorsRobert L. Linnen23
Estimated H-index: 23
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Abstract
Abstract Canadian Malartic is a large-tonnage, low-grade Archean gold deposit (16.3 Moz, 1.08 g/t Au) located in the Abitibi region of Quebec, Canada. A large part of the mineralization is hosted in the Pontiac Group metasedimentary rocks, which consist of mudstones to greywackes at upper greenschist to amphibolite facies. In exploration and production environments, these lithologies are challenging to characterize by conventional core logging methods, while in a research setting thin section-sized samples (2 cm × 4 cm) do not capture the full extent of mineralogical variability, which can extend from centimeters to meters away from mineralized zones. Here, high-resolution hyperspectral imagery (0.2–1.0 mm/pixel) in both shortwave infrared (SWIR, 1000–2500  nm) and longwave infrared (LWIR, 8000–12000 nm) is acquired for over two thousand meters of drill core, and is used to visualize changes in mineralogy and mineral chemistry related to metamorphism and hydrothermal alteration. Unaltered metasedimentary rocks contain metamorphic white mica with Al VI contents varying between 1.90 and 1.75 apfu (2195 to 2203 nm), depending on metamorphic grade. Hydrothermal alteration is characterized by white mica which becomes progressively more phengitic with increasing alteration intensity, with Al VI contents ranging from 1.70 to 1.50 apfu (2204 to 2212 nm). Phengitic white mica extends from meters to tens of meters away from major mineralized zones, and can be used as a vector towards mineralization in an exploration setting. White mica composition is correlated to Au content, and can be used to discriminate between unmineralized ( 0.3 g/t Au, 2205–2208 nm), and highly mineralized (>1.0 g/t Au, >2208 nm) samples, which is a simple metric that can directly be applied to sort ore in a production environment. The Mg# (molar Mg/[Mg + Fe]) of biotite, on the other hand, is unaffected by metamorphic grade, and consistently is Mg# 55–60 (2251–2250 nm) in unaltered samples. In mineralized samples, biotite is Mg-rich (Mg# >65,
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Published on Jun 1, 2019in Mineralium Deposita 3.40
Stéphane Perrouty9
Estimated H-index: 9
(Laurentian University),
Robert L. Linnen4
Estimated H-index: 4
(UWO: University of Western Ontario)
+ 5 AuthorsRandolph J. Enkin24
Estimated H-index: 24
(Geological Survey of Canada)
Ore-forming hydrothermal fluids react differently with different country rocks, but few studies have applied this knowledge with the specific goal of expanding the size of hydrothermal footprints in mineral exploration. To develop this concept, 122 metamorphosed mafic dykes from the world-class Canadian Malartic gold district (18.6 Moz Au) were sampled and analyzed for mineralogy, physical properties, and lithogeochemistry (partial and total digestion). The mafic dykes intrude mainly metasedimen...
Published on Jan 1, 2019in Precambrian Research 3.83
Nicolas Piette-Lauzière2
Estimated H-index: 2
(Laval University),
Carl Guilmette14
Estimated H-index: 14
(Laval University)
+ 6 AuthorsGema R. Olivo14
Estimated H-index: 14
(Queen's University)
Abstract The Pontiac Subprovince is located in the Superior Province, south of the Abitibi Subprovince. The metasedimentary rocks of the Pontiac Group are characterized by a Barrovian metamorphic gradient increasing from north to south from biotite- through garnet- to staurolite-zone conditions. The Pontiac Subprovince has been interpreted as an accretionary wedge or alternatively as an exotic terrane that was tectonically docked to the Abitibi Subprovince during Archean subduction. However, few...
Philip Lypaczewski2
Estimated H-index: 2
(U of A: University of Alberta),
Philip Lypaczewski1
Estimated H-index: 1
,
Benoit Rivard33
Estimated H-index: 33
Abstract Shortwave infrared (SWIR, 1000–2500 nm) reflectance spectra of biotite and chlorite were investigated to establish quantitative relationships between spectral metrics and mineral chemistry, determined by electron microprobe analysis (EMPA). Samples spanning a broad range of mineral compositions were used to establish regression equations to Mg#, which can be estimated to ±3 and ±5 Mg#, and to Al VI content, which can be estimated to ±0.044 Al VI (11 O) and ±0.09 Al VI (14 O), respective...
Published on May 1, 2018in Ore Geology Reviews 3.39
Charles L. Bérubé3
Estimated H-index: 3
(École Polytechnique de Montréal),
Gema R. Olivo14
Estimated H-index: 14
(Queen's University)
+ 6 AuthorsRaphaël Thiémonge1
Estimated H-index: 1
(École Polytechnique de Montréal)
Abstract The Canadian Malartic deposit is a world class intrusion-related Archean gold deposit hosted in the Pontiac Subprovince, Superior Province, in Quebec, Canada. Laboratory petrophysical properties measurements were performed on 824 rock samples collected from the various rock types observed within the ore body and peripheral host rocks. The various rock types present in the Malartic District, mainly meta-sedimentary rocks, felsic-intermediate intrusive rocks and mafic dykes have contrasti...
Published on Mar 1, 2018in Economic Geology 3.29
Garth E. Graham4
Estimated H-index: 4
(USGS: United States Geological Survey),
Raymond F. Kokaly21
Estimated H-index: 21
(USGS: United States Geological Survey)
+ 3 AuthorsBernard E. Hubbard11
Estimated H-index: 11
(USGS: United States Geological Survey)
Published on Feb 1, 2018in Ore Geology Reviews 3.39
Nicolas Gaillard2
Estimated H-index: 2
(McGill University),
Anthony E. Williams-Jones43
Estimated H-index: 43
(McGill University)
+ 6 AuthorsRobert L. Linnen4
Estimated H-index: 4
(UWO: University of Western Ontario)
Abstract Canadian Malartic, with a total endowment of 16.3 Moz Au, is an important example of a large-tonnage, low-grade Archean gold deposit (current reserves of 204 Mt @ 1.08 g/t Au). It is located in the southern Superior Province in contact with, and immediately south of the east-west trending Cadillac-Larder Lake fault zone, which delineates the boundary between the Pontiac and Abitibi subprovinces. The deposit is hosted by Pontiac Group metaturbidites, Piche Group mafic-ultramafic metavolc...
Published on Jul 1, 2017in Canadian Mineralogist 1.40
David Turner5
Estimated H-index: 5
(UBC: University of British Columbia),
Lee A. Groat21
Estimated H-index: 21
(UBC: University of British Columbia)
+ 1 AuthorsPhilippe M. Belley2
Estimated H-index: 2
(UBC: University of British Columbia)
Abstract Baffin Island (Nunavut, Canada) is located in the remote arctic where geological exposure is high, terrain is expansive, and field seasons are short. Metacarbonates in the Lake Harbour Group, southern Baffin Island, are considered to be prospective for sapphire (corundum), lapis lazuli (lazurite), and spinel gem deposits. This research is an investigation of the hyperspectral signature of rocks from the Beluga sapphire occurrence near Kimmirut, Nunavut. Thirty-five rock and thin section...
Published on Jun 25, 2017in Economic Geology 3.29
Rui Wang10
Estimated H-index: 10
(CSIRO: Commonwealth Scientific and Industrial Research Organisation),
Thomas Cudahy16
Estimated H-index: 16
(CSIRO: Commonwealth Scientific and Industrial Research Organisation)
+ 9 AuthorsMalcolm Roberts10
Estimated H-index: 10
(UWA: University of Western Australia)
Patterns in white mica (muscovite, paragonite, and phengite) Al-Si chemistry (Tschermak substitution) were examined for the Archean Kanowna Belle and Sunrise Dam gold deposits in the Eastern Goldfields of Western Australia, using short-wave infrared (SWIR) spectrometry of drill core samples. Both of these deposits represent greenschist-facies, structurally controlled, >10-Moz gold systems with broadly similar host rocks and superimposed metasomatic hydrothermal alteration halos that extend for u...
Published on May 1, 2017in Minerals Engineering 3.31
M. Dalm1
Estimated H-index: 1
(TU Delft: Delft University of Technology),
M.W.N. Buxton3
Estimated H-index: 3
(TU Delft: Delft University of Technology),
F.J.A. van Ruitenbeek5
Estimated H-index: 5
(UT: University of Twente)
A recent study by Dalm et al. (2014) showed that alteration mineralogy acquired using SWIR point spectrometry could be linked to copper grade distribution for a group of samples from a South American copper mine. Since it was expected that SWIR hyperspectral imagery can provide more detailed information about the alteration mineralogy of these ores, we investigated whether this technique can be used to improve upon the indirect characterization of copper grades. Maps showing the distributions of...
Published on Apr 1, 2017in Ore Geology Reviews 3.39
Stéphane Perrouty9
Estimated H-index: 9
(UWO: University of Western Ontario),
Nicolas Gaillard2
Estimated H-index: 2
(McGill University)
+ 9 AuthorsCarl Guilmette14
Estimated H-index: 14
(Laval University)
Abstract The structural setting of the Pontiac Subprovince in the vicinity of the world-class Canadian Malartic gold deposit has been revisited by combining and reinterpreting airborne geophysical surveys together with a century of structural observations. Felsic-intermediate intrusive bodies are a key component of this deposit. Defining the regional and local favorable structural setting for intrusive rock emplacement within the clastic meta-sedimentary rocks of the Pontiac Group, south of the ...
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