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Precambrian geology of the Lumby Lake greenstone belt
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THESE TERMS GOVERN YOUR USE OF THIS PRODUCT
Your use of this electronic information product (“EIP”), and the digital data files contained on it (the “Content”), is governed by the terms set out on this page (“Terms of Use”). By opening
the EIP and viewing the Content , you (the “User”) have accepted, and have agreed to be bound by, the Terms of Use.
EIP and Content: This EIP and Content is offered by the Province of Ontario’s Ministry of Northern Development, Mines and Forestry (MNDMF) as a public service, on an “as-is” basis. Recommendations and statements of opinions expressed are those of the author or authors and are not to be construed as statement of government policy. You are solely responsible for your use of the EIP and its Content. You should not rely on the Content for legal advice nor as authoritative in your particular circumstances. Users should verify the accuracy and applicability of any Content before acting on it. MNDMF does not guarantee, or make any warranty express or implied, that the Content is current, accurate, complete or reliable or that the EIP is free from viruses or other harmful components. MNDMF is not responsible for any damage however caused, which results, directly or indirectly, from your use of the EIP or the Content. MNDMF assumes no legal liability or responsibility for the EIP or the Content whatsoever. Links to Other Web Sites: This EIP or the Content may contain links, to Web sites that are not operated by MNDMF. Linked Web sites may not be available in French. MNDMF neither endorses nor assumes any responsibility for the safety, accuracy or availability of linked Web sites or the information contained on them. The linked Web sites, their operation and content are the responsibility of the person or entity for which they were created or maintained (the “Owner”). Both your use of a linked Web site, and your right to use or reproduce information or materials from a linked Web site, are subject to the terms of use governing that particular Web site. Any comments or inquiries regarding a linked Web site must be directed to its Owner. Copyright: Canadian and international intellectual property laws protect the EIP and the Content. Unless otherwise indicated, copyright is held by the Queen’s Printer for Ontario. It is recommended that reference to the Content be made in the following form: Buse, S., Lewis, D. and Magnus, S. 2010. Precambrian geology of the Lumby Lake greenstone belt; Ontario
Geological Survey, Preliminary Map P.3619, scale 1:20 000. Use and Reproduction of Content: The EIP and the Content may be used and reproduced only in accordance with applicable intellectual property laws. Non-commercial use of unsubstantial excerpts of the Content is permitted provided that appropriate credit is given and Crown copyright is acknowledged. Any substantial reproduction of the Content or any commercial use of all or part of the Content is prohibited without the prior written permission of MNDMF. Substantial reproduction includes the reproduction of any illustration or figure, such as, but not limited to graphs, charts and maps. Commercial use includes commercial distribution of the Content, the reproduction of multiple copies of the Content for any purpose whether or not commercial, use of the Content in commercial publications, and the creation of value-added products using the Content. Contact:
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SOURCES OF INFORMATIONDigital base map information derived from the Ontario Land InformationWarehouse, Land Information Ontario, Ontario Ministry of NaturalResources, scale 1:20 000, with modifications by staff of the Ministry ofNorthern Development, Mines and Forestry.
Mapping conducted using Universal Transverse Mercator (UTM)coordinates in North American Datum 1983 (NAD 83), zone 15.
Buse, S., Lewis, D. and Magnus, S. 2009. Field investigations in theLumby Lake greenstone belt, NW Ontario: New insights into the geology,structure and economic potential; in Summary of Field Work and OtherActivities 2009, Ontario Geological Survey, Open File Report 6240,p.15-1 to 15-15.
Davis, D.W. and Jackson, M.C. 1988. Geochronology of the Lumby Lakegreenstone belt: A 3 Ga complex within the Wabigoon Subprovince,northwest Ontario; Geological Society of America Bulletin, v.100,p.818-824.
Hollings, P. and Wyman, D. 1999. Trace element and Sm-Nd systematicsof volcanic and intrusive rocks from the 3 Ga Lumby Lake greenstonebelt, Superior Province: evidence for Archean plume-arc interaction;Lithos, v.46, p.189-312.
Jackson, M.C. 1985a. Geology of the Lumby Lake area, western part,districts of Kenora and Rainy River; Ontario Geological Survey,Open File Report 5534, 151p.
Jackson, M.C. 1985b. Geology of the Lumby Lake area, eastern part,districts of Kenora and Rainy River; Ontario Geological Survey,Open File Report 5535, 122p.
Kamineni, D.C., Stone, D. and Peterman, Z.E. 1990. Early Proterozoicdeformation in the western Superior Province, Canadian Shield;Geological Society of America Bulletin, v.102, p.1623-1634.
Ontario Geological Survey 2009. Airborne geophysical time domainelectromagnetic and magnetic survey, Lumby–Finlayson lakes area;Ontario Geological Survey, Geophysical Data Set 1060.
Tomlinson, K.Y., Davis, D.W., Stone, D. and Hart, T.R. 2003. U-Pb ageand Nd isotopic evidence for Archean terrane development and crustalrecycling in the south-central Wabigoon subprovince, Canada;Contributions to Mineralogy and Petrology, v.144, p.684-702.
Tomlinson, K.Y., Hughes, D.J., Thurston, P.C. and Hall, R.P. 1999. Plumemagmatism and crustal growth at 2.9 to 3.0 Ga in the Steep Rock andLumby Lake area, Western Superior Province; Lithos, v.46, p.103-136.
Woolverton, R.S. 1960. Geology of the Lumby Lake area; OntarioDepartment of Mines, Annual Report, v.69, part 5, 52p.
Wyman, D. and Hollings, P. 1998. Long-lived mantle-plume influence onan Archean protocontinent: Geochemical evidence from the 3 Ga LumbyLake greenstone belt, Ontario, Canada; Geology, v.26, no.8, p.719-722.
Assessment files from the GeologyOntario website.
Magnetic declination was approximately 1º32′W at the centre of the maparea in 2009.
Geology not tied to surveyed lines.
Users of OGS products are encouraged to contact those Aboriginalcommunities whose traditional territories may be located in the mineralexploration area to discuss their project.
Features 1d Spinifex textured 1e Dikes 1f Talcose 1g Cumulate 1h Organized
a This legend is based only on field investigations and is subject to change based on geochronological data.b The letter ‘G’ preceding a rock code indicates interpretation from geophysical data. The letter ‘C’ preceding a rock code indicates compilation from a previously published map.c Units 3 and 5 as drawn on the map are not the representative thicknesses of the units. Unit 3 ranges from 1 to 30 m thick and unit 5 is commonly only 1 m thick.d Interpreted to be synvolcanic and likely the same affinity as the unit 8 gabbros. These rocks were observed as coarse-grained flows, dikes or sills, but due to the scale and the scope of the project, not every one of the coarse-grained flows to gabbro dikes/sills are shown individually on the map.
Geochronology samplelocation, with age in Ma(keyed to table 1)
Mineral deposit(keyed to table 2)
Drill hole(keyed to table 4)
Powerline
Road (secondary,tertiary)
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10
10
10
10
101010
10
10
10
10
Y1: 3001±1
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Figure 2. Regional maps and associated stereonet diagrams showing the trajectory of the S1 foliation, S2 foliation and L1 lineation across the Lumby Lake greenstone belt.Equal Area
Candela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoT. JohansenCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdPinecone Mines LtdCandela Dev CoPinecone Mines LtdPinecone Mines LtdCominco LtdPinecone Mines LtdCanadian Nickel Co LtdCanadian Nickel Co LtdCan Nickel Co LtdCan Nickel Co Ltd
Univex ExplorationPremier Lake Resources LtdUnivex ExplorationKerr Addison Mines LtdUnivex ExplorationKerr Addison Mines LtdUnivex ExplorationUnivex ExplorationPremier Lake Resources LtdPremier Lake Resources LtdPremier Lake Resources LtdPremier Lake Resources LtdUnivex ExplorationFalconbridge Nickel Mines LtdC.L. BolandC.L. BolandJ.D. MacMillan (Canico)J.D. MacMillan (Canico)F. SandersFalconbridge Nickel Mines LtdJ.D. MacMillan (Canico)F. SandersF. SandersJ.D. MacMillan (Canico)F. SandersF. SandersFalconbridge Nickel Mines LtdCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCandela Dev CoCanadian Nickel Co Ltd
Marginal NotesThe Lumby Lake greenstone belt is composed of two tectonostratigraphicassemblages: the northern assemblage, comprising the Lumby North andPinecone depositional sequences; and the southern assemblage, comprising theLumby South and Bar Lake depositional sequences (Figure 1). The boundariesof these assemblages are based on new geologic mapping as well asgeochemical data (Tomlinson et al. 1999; Hollings and Wyman 1999; Wymanand Hollings 1998) and U-Pb geochronological data (Tomlinson et al. 2003;Davis and Jackson 1988). (See “Sources of Information” for all references.)U-Pb geochronology ages for the greenstone belt are summarized in Table 1and are plotted on the map.
The greenstone belt was first mapped by Woolverton (1960) who interpreted thebelt to be a large syncline with the east-trending axial plane in the centre of thegreenstone belt. The belt was later mapped by Jackson (1985a, 1985b) who alsointerpreted the greenstone belt to be a syncline. New mapping shows thatstratigraphy on the north and south sides of the greenstone belt is different, andinstead of a syncline there is a belt-scale thrust fault at the southern margin of thePinecone sedimentary sequence, with subsequent dextral shearing. For moreinformation on the stratigraphy, intrusive rocks, mineralization and alterationplease see Buse, Lewis and Magnus (2009).
Several new occurrences were identified as a result of the geologic mapping in2009. These are summarized with the Mineral Deposit Inventory (MDI) locationsin Table 2. The majority of the new occurrences are nickel occurrences fromwithin ultramafic intrusive rocks and represent an under-explored commodity inthe Lumby Lake greenstone belt. Another new occurrence is a zinc occurrencethat is consistent with other historic Cu-Zn-Pb-Ag occurrences along the base ofthe greenstone belt. For more information about the mineral potential in thegreenstone belt please see Buse, Lewis and Magnus (2009).
Structural Geology
There are three main deformational events within the Lumby Lake greenstone belt, assummarized in Table 3. The D1 deformational event is represented by an east-trendingpenetrative foliation with an associated northeast-trending stretching lineation (Figure 2).The foliation is commonly defined by chlorite in the mafic metavolcanic rocks and other micasin the felsic metavolcanic rocks. This foliation and its associated lineation are deformed aroundthe plutons that intrude the greenstone belt, due to strain during plutonic emplacement. Theintensity of the S1 foliation ranges from weak to strong and becomes subparallel to D2 shearzone margins. There is weak structural evidence for a D1 north-side-up thrust fault, located atthe southern margin of the Pinecone depositional sequence, that was reactivated during D2faulting. However, stratigraphy to the north and south of this fault is quite different and thereis no evidence for folding in the area, suggesting the synclinal model of Woolverton (1960)and Jackson (1985a, 1985b) is no longer relevant.
The D2 deformational event is related to the northeast-trending Red Paint Fault Zone, locatedon the western margin of the Lumby Lake greenstone belt. D2 faults are sinistral strike-slipfaults that trend northeast. They include the Red Paint Fault Zone and the numerous splaysand corresponding faults that extend from the fault zone. The Red Paint Fault Zone is a 600 mwide zone of intensely foliated mafic metavolcanic rocks, bounded to the west by the relativelyundeformed Dashwa Lake batholith. The smaller D2 splay and corresponding faults are not aswide, but are associated with a similar intensification of the northeast-trending S2 foliation(Figure 2). A northwest-trending, moderately plunging crenulation lineation is also associatedwith this deformational event.
East-trending D2 dextral shear zones are found locally along the base of the greenstone beltas well as in the centre of the greenstone belt at the boundary between the north and southtectonostratigraphic assemblages. This D2 dextral shearing represents the reactivation of theD1 thrust fault at the centre of the greenstone belt. Folding in the Lumby Lake greenstone beltis rare and generally associated with D2 generation faulting. The D3 deformational event isrepresented by a discrete north-trending S3 foliation that may be associated with latemovement in the Red Paint Fault Zone or the emplacement of intrusions following faulting.
Table 2. Mineral occurrences in the Lumby Lake greenstone belt. All coordinates are in NAD83, UTMzone 15; all data for geochemical analyses were provided by the Geoscience Laboratories, OntarioGeological Survey, Sudbury, Ontario.
Table 1. Summary of geochronological data for the Lumby Lake greenstone belt.All coordinates are in NAD83, UTM zone 15; all ages are U-Pb zircon thermal ionizationmass spectrometry (TIMS) ages.
CREDITSGeology by S. Buse, D. Lewis and S. Magnus, with assistance fromC. Purdy, A. Hills, A. Berger and E. Rock.
Digital drafting by J. Webb, S. Buse and D. Lewis.
Cartographic production by A. Evers.
To enable the rapid dissemination of information, this map has notreceived a technical edit. Discrepancies may occur for which the OntarioMinistry of Northern Development, Mines and Forestry does not assumeliability. Users should verify critical information. Sources include both thereferences listed here and information on file at the Resident Geologists’and Mining Recorders’ offices nearest the map area.
The Atikokan Mineral Development Initiative is a Township of Atikokan project managed by the Ontario Prospectors Association. The Initiative is intended to provide a better understanding of the mineral resource potential of targeted areas in the vicinity of the Atikokan community through the collection and analysis of geoscience data and through the marketing of these data to the minerals industry. The geophysical component of the Initiative includes flying new airborne magnetic and electromagnetic surveys in the region and producing the results in digital and hardcopy formats suitable for publication. The Initiative is supported by the Township of Atikokan, Northern Ontario Heritage Fund Corporation, FedNor and the Ontario Geological Survey.
Issued 2010.
Information from this publication may be quoted if credit is given. It isrecommended that reference to this map be made in the following form:
Buse, S., Lewis, D. and Magnus, S. 2010. Precambrian geology of the Lumby Lake greenstone belt; Ontario Geological Survey, Preliminary Map P.3619, scale 1:20 000.