Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI53B09SW00008

Record: MDI53B09SW00008

General

Commodities

Primary Commodities: Gold

Location

Township or Area: Zeemel Lake Area, Skinner Lake Area

Latitude: 52° 36' .21"    Longitude: -90° 25' 14.26"

UTM Zone: 15    Easting: 674682.55   Northing: 5830906.28    UTM Datum: NAD83

Resident Geologist District: Thunder Bay North

NTS Grid: 53B09NW, 53B09SW

Point Location Description: Approximate location of DDH 08-WAT-007 from map in Assessment report 20000013696

Location Method: Data Compilation

Access Description: Access is gained by driving 130 km north of Pickle Lake Ontario along a large well-kept gravel highway.

Exploration History

1963: Kenpat Mines Ltd. carried out mapping and a magnetometer survey. 1973: A. Musselwhite and W Musselwhite carried out trenching and mapping. 1975-76: Canadian Nickel Company carried out magnetic and EM surveys. 1980: the West Anticline area was the first major discovery of gold mineralization on the south shore of Opapimiskan Lake. 1983: Construction of the winter access road was initiated to facilitate a bulk sampling program on the West Anticline area. 1984: A decline and bulk sampling program were completed. 1992: Placer Dome drilled 3 DDH totalling 501 m. 1996: Placer Dome drilled 23 DDH totalling 1468 m. 2003-04: Placer Dome carried out two drill programs totalling 10,020 m of surface drilling in 74 holes. 2008-09: Goldcorp drilled 30 DDH totaling 2760.2 m.

Assessment Work on File

Geology

Province: Superior

Subprovince: Berens River

Terrane: North Caribou

Domain: North Caribou Core

Belt: North Caribou

Geological Age: Mesoarchean  

Metamorphism Type: Regional

Metamorphism Grade: Amphibolite

Geology Comments

Mar 14, 2008 (Mark Puumala) - The Musselwhite West Anticline Deposit is hosted in the Opapimiskan Lake unit of the McGruer assemblage (Thurston, Osmani and Stone 1991), which is described by Breaks, Osmani and deKemp (2001) as an ultramafic to mafic metavolcanic rock dominated sequence containing numerous units of silicate and oxide-facies iron formation. The most significant iron formation horizon is a complexly-folded 30 km long unit (based on magnetic relief) known as the Opapimiskan Lake banded iron formation (Breaks, Osmani and deKemp 2001). The West Anticline Deposit is found in an area of great structural complexity that encompasses a relatively wide area (approximately 2.5 km east-west by 2.0 km north-south), and is comprised of four main gold mineralized zones that are referred to as the West Anticline, Bay, Camp, and Canoe Zones by Cheatle (2006). A fifth area of mineralization known as the No. 1 Zone was also identified by Hall and Rigg (1986). Gold mineralization in the West Anticline Deposit is reported by Hall and Rigg (1986) to be largely hosted within a deformed chert-magnetite iron formation horizon referred to as the middle ironstone. This iron formation horizon is located immediately above (i.e., to the northwest of) a mafic to ultramafic metavolcanic-dominated rock sequence (this sequence contains a thin iron formation called the southern ironstone), and immediately below a metasedimentary horizon referred to as the ¿hangingwall metasedimentary rocks.¿ The hangingwall metasediments consist of a thick (80 m) upper unit (northern ironstone) consisting of cm-wide bands of iron-rich pelitic sediments interlayered with minor quartz-magnetite iron formation, and a 5 to 20 m thick massive pelitic unit that immediately overlies the middle ironstone. All of the rocks in this area contain mineral assemblages characteristic of amphibolite facies metamorphism (Hall and Rigg 1986). The gold-bearing middle ironstone ranges in thickness from 5 to 15 m and has a well-developed internal stratigraphy (Hall and Rigg 1986). The upper 2 m of this unit consists of fine laminations of quartz and magnetite, which in turn grades downward into a rock consisting of quartz-magnetite laminae interlayered with thin, discontinuous layers containing mm-scale garnets in a hornblende and minor biotite-bearing matrix. The lower portions of the middle ironstone consist of quartz-grunerite (magnetite-poor) iron formation. The West Anticline is described by Hall and Rigg (1986) as an antiformal structure with the shape of an inverted canoe. The fold hinge plunges approximately 35 degrees to the northwest, with local plunge variations between 0 and 60 degrees. The most notable outcrop-scale structural features in the West Anticline Zone are 1 to 20 m similar folds that have a near-vertical 120-striking axial planar cleavage. These folds are interpreted by Hall and Rigg (1986) to represent a D2 folding event, which deformed previously-existing isoclinal folds, and developed Type 1 basin and dome interference patterns. The S2 cleavage planes sometimes show evidence of shear displacement. The S2 structures observed in the West Anticline Zone have been observed by Hall and Rigg (1986) to host the gold mineralization.

Lithology

Lithology Comments

Mar 14, 2008 (Q Unknown) - The stratigraphic sequence is somewhat a typical of archean greenstone terranes with a thick sequence of aluminous sedimentary rocks within a terrane of mafic and ultramafic rocks. This portion of th North Caribou Lake terrane consists primarily of a thick sequence of nonvesiclar mafic volcanic rocks with a minor component of ultramafic rocks. The very minor occurrence of posible felsic volcanic rocks indicates the Opap. Lake portion of the terane was at some distance from any major site of felsic volcanism. No medium or coarse grained clastic sedimentary rocks are observed in the Opap. Lake area. The thick sequence of iron rich pelitic sedimentary rocks interlaminated with chert-magnetite ironstone is unique to the Opap. Lake area. - There is no evidence to suggest the majority of the pelitic sedimentary rocks are the product of prograde metamorphism of hydrothermally altered volcanic rocks. There is, however, no obvious source for these aluminous sediments in this dominantly mafic and ultramafic and ultramafic volcanic terrane. These pelitic sediments are interpreted to preresent metamorphosed iron-rich clays. - These aluminous iron-rich sediments are coeval with the quartz-magnetite ironstone, as demonstrated by their fine varve like interlamination over a 50m thickness. The well-defined internal stratigraphy continues along strike at least 20km from the West Anticline area. - The (mm)-scale lamination, strike, length, and continuity of units along strike of this sedimentary sequence in association with non-vesicular mafic and ultramafic volcanic rocks suggests they were slowly deposited in a stable quiescent environment, such as a deep water marine basin.

Mineralization

Mineralization Comments

Mar 14, 2008 (Mark Puumala) - Hall and Rigg (1986) reported two principal styles of gold mineralization in the West Anticline Zone. These include sub-vertical quartz-pyrrhotite veinlets/lenses, and stratabound zones of disseminated mineralization. At the No. 1 showing, near the eastern end of the West Anticline Zone, Piroshco, Breaks and Osmani (1989) also noted gold mineralization hosted in shear zones, albite-pegmatite dikes, and metasomatic selvages adjacent to the dikes. The gold mineralized quartz veinlets, which comprise a minor portion of the economic mineralization, are typically 1 to 5 cm wide. The veins consist largely of saccharoidal blue-grey quartz with massive medium-grained pyrrhotite. Mineralization also includes minor arsenopyrite, galena, sphalerite and scheelite, and rare pyrite, chalcopyrite, native gold and altaite. The veinlets are typically enveloped by a narrow selvage of grunerite (Hall and Rigg 1986). Stratabound disseminated mineralization in the middle ironstone is reported by Hall and Rigg (1986) to occur as elongate lenses plunging parallel to the D2 fold axes. The gold occurs in zones characterized by high grunerite content (with corresponding decreases in magnetite), fine disseminated pyrrhotite, calcite, albite and garnet, with rare arsenopyrite and gold. Gold typically occurs as microscopic grains within pyrrhotite. At the No. 1 showing, Piroshco, Breaks and Osmani (1989) reported the presence of significant gold mineralization (up to 6.7 ppm) in a 1 to 1.8 m wide siliceous breccia of banded iron formation that is hosted in a shear zone. The shear zone trends northwest, parallel to the axial plane of the West Anticline structure, and is mineralized with 5 to 15% disseminated pyrrhotite, pyrite and arsenopyrite. An interconnecting system of 1 to 5 mm pyrrhotite veinlets also occurs in this zone. Piroshco, Breaks and Osmani (1989) also report anomalous gold assays of up to 1840 ppb in albite pegmatite dikes that cross-cut the mafic metavolcanics and southern ironstone near the No. 1 showing. Metasomatic selvages along the dike contacts also assayed up to 1740 ppb. The dikes and selvages are also reported to contain anomalous levels of the rare metals lithium, rubidium and tantalum. Hall and Rigg (1986) reported that these dikes are weakly deformed and sericitized. The West Anticline Zone is reported by Blower and Kiernan (2003) to host probable reserves of 308 312 tonnes grading 5.6 g/t Au, representing a total gold content of 1 736 105 g.

Sep 11, 2019 (Therese Pettigrew) - The West Anticline area is a structurally complex environment comprised of numerous second- and third-order F2 minor fold closures. These structures display curvilinear plunge axes with a regional trend of 30° to 40° to the northwest. The area has been further subdivided into four principal exploration areas, the West Anticline, Bay, Camp, and Canoe zones. Within the West Anticline zone, quartz-pyrrhotite vein systems occur extensively throughout the middle iron formation, from the footwall to hanging wall contacts. Veining appears best developed in F2 antiformal closures. Throughout these favourable areas, the spacing of the veins is between 1.5 m and 2.5 m. The veins are well developed and display good lateral continuity. Strata-bound mineralization is extensive throughout the area, with the best zones developed within a garnet-biotite-chert-magnetite unit directly beneath a well-bedded, grunerite-rich iron formation domain. There is also relatively extensive strata-bound mineralization, lower in the stratigraphy; however, it is of lower grade and is more erratic in nature (Blower and Kiernan, 2003). The 2003-04 drill program returned gold values from 4 g/t Au over 0.66 m up to 32.76 g/t Au over 3.86 m (Assessment report 53B09NW2010). DDH 08-WAT-007 assayed up to 27.10 g/t Au over 1 m. DDH 08-WAT-008 assayed up to 11.0 g/t over 1 m. DDH 08-WAT-009 assayed up to 16.33 g/t Au over 0.4 m (Assessment report 20000013696).

Mineral Record Details

Mineral Zones - Size and Shape

References

Book - Geology of the West anticline zone, Musselwhite prospect, Opapimiskan Lake, Ontario, Canada; in Proceedings of Gold '86, Konsult International, Toronto, Ontario, p. 124-136.

Publication Number: Date: 1996

Author: Hall, R.S. and Rigg, D.M. 1986.

Publisher Name: Konsult International

Location: Thunder Bay RGP

Publication - Technical Report; Review of Musselwhite Mine Operations

Publication Number: Tech Rep 2003 Date: 2003

Author: Blower, S., and Kiernan, J.

Publisher Name: Kinross Gold Corp.

Location: https://www.miningdataonline.com

Book - Northern Miner 83/01/20

Publication Number: NMINER Date: 1996

Author:

Publisher Name: Northern Miner

Location:

Mono - The geology of gold prospects in the North Caribou Lake greenstone belt, District of Kenora, northwestern Ontario

Publication Number: OFR5698 Page: 4-8  Date: 1989

Author: Piroshco D.W., Breaks F.W., Osmani I.A.

Publisher Name: Ontario Geological Survey

Location:

Book - Resident Geologist files (Musselwhite 1989)

Publication Number: Date: 1996

Author:

Publisher Name:

Location:

MonoMap - Geology of the North Caribou Lake Area, Northwestern Ontario

Publication Number: OFR6023 Date: 2001

Author: Breaks F.W., Osmani I.A., de Kemp E.A.

Publisher Name: Ontario Geological Survey

Location:

Article - Northwestern Superior province: review and terrane analysis

Publication Number: SV04-01.005 Date: 1997

Author: Thurston P.C., Osmani I.A., Stone D.

Publisher Name: Ontario Geological Survey

Location:

Book - Musselwhite Mine: Technical report geology

Publication Number: Tech Rep Date: 2006

Author: Cheatle, A.M.

Publisher Name:

Location: Thunder Bay RGP

Article - A preliminary reconnaissance of the Weagamow-North Caribou Lake metavolcanic-metasedimentary belt, including the Opapimiskan Lake (Musselwhite) gold occurrence

Publication Number: MP100.032 Page: 204-209  Date: 1998

Author: Andrews A.J., Sharpe D.R., Janes D.A.

Publisher Name: Ontario Geological Survey

Location:

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For detailed information regarding this mineral record please contact the Thunder Bay North Resident Geologist District Office