Controls on volcanogenic massive sulphide mineralization
Controls on volcanogenic massive sulphide mineralization in the Kamiskotia area, Ontario, Canada: insights from lithogeochemical analysis and mineral prospectivity modelling
Samuel E. K. Tetteh1*, Stefanie M. Brueckner1,2, Lionel Bonhomme3, John Ayer2, Jeff Harris2, Ross Sherlock2
1 University of Manitoba, Department of Earth Sciences, Winnipeg, Canada; 2 Laurentian University, Harquail School of Earth Sciences, Mineral Exploration Research Centre, Sudbury, Canada; 3 International Explorers & Prospectors Inc., Timmins, Ontario, Canada
*Corresponding author: tettesek@myumanitoba.ca
1. Geological context
The Kamiskotia area, Ontario, Canada, is dominated by the Blake River (2704 – 2696 Ma) and Kidd Munro (2719 – 2711 Ma), bimodal assemblages of tholeiitic basalts intercalated with abundant high-silica FIII rhyolites (Fig. 1). Other Neo-Archean assemblages in the area include the Deloro, Tisdale, and Porcupine. The area is one of Abitibi’s VMS hosting districts.
2. Background
Bimodal mafic Cu-Zn ± Au ± Ag VMS deposits in the area share similarities regarding (i) their host lithologies (i.e., bimodal assemblage), (ii) alteration (i.e., proximal chloritic - distal sericitic alteration), (iii) morphology (numerous small dipping lenses), (iv) stratigraphy (i.e., restricted < 150 m stratigraphic interval), and (v) ore assemblage (i.e., pyrite, pyrrhotite, chalcopyrite, sphalerite) (Barrie, 2000; Hathway et al., 2008).
Based on these observations, it is likely that the Kamiskotia Volcanic Complex (correlated to the Blake River Assemblage) hosts yet unidentified VMS deposits that would contribute to the increasing metal demand of Cu and Zn. However, given the extensive overburden cover and the fact that most near-surface deposits have been discovered and exploited, new approaches such as mineral prospectivity modelling are required to increase the effectiveness of exploration.
This study seeks to address this need using a large geochemical dataset with other geoscience data to outline controls on VMS mineralization in the Kamiskotia area. Also, the project will constrain ore assemblage, lithogeochemistry, and potentially geochronology on the Genex deposit to contribute to age, lithology, tectonic setting and mineralogy of the Kamiskotia Volcanic Complex
3. Approach
Identify key geochemical features (e.g., magmatic affinity, rhyolite type) through analysis of a lithogeochemical database with 10357 samples.
Identify alteration trends (e.g., boxplot, molar K/Al vs Na/Al plot), especially in units that are geochemically and stratigraphically similar to known VMS host units.
Produce 3D models (metal grades, alteration and geology).
Produce mineral prospectivity maps through machine learning techniques to delineate potential exploration targets
4. Results
The units are tholeiitic to transitional basalts, basaltic andesites, and rhyodacites. The mafic units have contaminated (i.e., Th/Nb ratio) MORB-like magma affinities (Fig. 2) and Fe-Ti signatures (i.e., P2O5 > 0.3 wt %, TiO2 > 2.2 wt %; Fig. 3). Rhyolites are of high-silica and high-Zr FIII-FII type (Fig. 4). These geochemical signatures are similar for all sampled assemblages. Cu, Zn, alteration indices, and the key geochemical signatures have strikingly similar spatial distributions (Fig. 5). 40 evidence layers (i.e., predictors maps) were generated from available geoscience data, in binary and continuous forms (Fig. 6). A Random Forest (RF) algorithm was employed to integrate these layers using 44 known mineralization locations. The resulting probability maps are used as prospectivity maps (Fig. 7).
5. Conclusions
Mafic and felsic rock geochemistry reveals a favourable setting for significant VMS mineralization. >Contaminated MORB signature: shallow-rifted setting, high heat flow, interaction with existing hydrated crust.
>Fe-Ti mafics: restricted to the immediate hanging wall of VMS mineralization.
>Felsic rock signatures: within-plate signatures, HFSE and REE enrichment, and high-silica FIII-FII affinities.
Evidence layers show good spatial relationships with known VMS mineralization sites.
Preliminary RF prospectivity maps accurately predict known VMS sites and outline new areas.
Next: finalize RF modelling and evaluate model performance using area-under-curve in Area-Frequency curves
References
• Barrie (2000). Geology of the Kamiskotia area. OGS Study 59.
• Hathway et al. (2008). Economic Geology, 103(6), 1185-1202.
• Pearce (2008). Lithos. Vol. 100, pp. 14-48.
• Lesher et al. (1986). Canadian Journal of Earth Sciences, Vol. 23, pp. 222-237.
Acknowledgments
This work has been funded by the Metal Earth at MERC and NSERC Discovery grant to SMB. The project has also been supported by IEP and Melkior. The lithogeochemical database for this project was prepared by Timothy Barrett.
IEP collaborates with MERC, Newmont and Pan American Silver
News Release 2020-09-17
MERC leads fall geophysical survey in Timmins-Cochrane region.
Laurentian University’s Mineral Exploration Research Centre (MERC) is leading a geophysical survey in the Timmins and Cochrane area from October 7 to November 15, 2020. The goal is to advance geoscientific knowledge about the underlying geologic architecture, structures, and mineral resource potential of the Earth’s crust approximately 30 kilometres below the surface.
The project is part of MERC’s $104 million Metal Earth project, which is Canada's most extensive exploration research program and involves a consortium of industry partners.
Quantec Geoscience will use electromagnetic technology, specifically magnetotelluric (MT) and audio magnetotelluric (AMT) instruments, to survey selected stations within a corridor of approximately 130 kilometres by 50 kilometres. The corridor stretches from Highway 11 in the north to 50 kilometres south of Timmins. Surveyors will be active in some residential areas. Interactive maps of the area and proposed stations are available at https://merc.laurentian.ca/TimminsMT.
High-resolution AMT surveys in the Timmins gold camp are made possible with consortium partner support. Newmont Corp is funding surveying from Tisdale to Matheson townships. International Explorers and Prospectors Inc. and Lake Shore Gold (a subsidiary of Pan American Silver) are funding surveys from Loveland to Thorneloe townships, west of Timmins.
MERC associate director, Dr. John Ayer, an expert in the region’s geology, is leading the project. Ayer said the fall survey adds data to previous seismic and ongoing MT and AMT surveys conducted through the Metal Earth project in Ontario and Quebec.
“Seismic surveys were completed as part of the Discover Abitibi project, managed by the Timmins Economic Development Corporation, in 2004," Ayer explained, adding that MT and AMT surveys were not previously conducted in the planned survey area.
"This fall’s surveying will create unique regional and high-resolution images integrated with seismic, gravity, and magnetic data to better evaluate the geology and economic potential of an historic and world-class gold camp," Ayer said.
All data collected will be made publicly available, providing a richer understanding of the region's resources and geologic structure. Members of the public and media are encouraged to visit merc.laurentian.ca/TimminsMT for details about the project.
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'IEP is excited to participate in this cutting edge research' says Lionel Bonhomme. ' This survey should be able to help us unlock the sources of the many base metal deposits we have been exploring west of Timmins in the Blake River Assemblage. As well, the survey could help unlock the gold potential of the Hoyle Pond Mine extension on our Matheson Twp JV property.'