Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI53C07NW00025

Record: MDI53C07NW00025

General

Commodities

Primary Commodities: Iron

Location

Township or Area: Hewitt Lake Area

Latitude: 52° 29' 12.2"    Longitude: -92° 49' 34.6"

UTM Zone: 15    Easting: 511796.24   Northing: 5815189.34    UTM Datum: NAD83

Resident Geologist District: Red Lake

NTS Grid: 53C07NW

Point Location Description: General

Location Method: Data Compilation

Access Description: 170 KM NE of Red lake, 11 KM E of First Nations community of North Spirit Lake. All weather airport and winter road.

Exploration History

1954-1960: Crown Trust Ltd: explored for iron ore on the main iron formation on the current HTX Minerals property and drilled 10 DDH totalling 1123.5 m. 2008-09: HTX Minerals completed mapping, sampling, geochemical analysis and petrographic examinations concentrating on the Ni-Cu-PGE potential of the ultramafic rocks. 2010: HTX sampling program and magnetic separation test work to evaluate the economic potential of the iron formation located on the SE of North Spirit Lake.

Assessment Work on File

Geology

Province: Superior

Subprovince: Sachigo

Terrane: North Caribou

Belt: North Spirit Lake

Geological Age: Mesoarchean  

Geology Comments

May 23, 2007 (Mark Puumala) - The most notable structural feature in the southern portion of the North Spirit Lake Greenstone Belt is the Bear Head Fault Zone. This is a northwest-striking, regional-scale, dextral strike-slip structure that extends for approximately 515 km from Lake Winnipeg in the northwest to the north boundary of the Meen-Dempster Greenstone Belt in the southeast (Osmani and Stott (1988). Wood (1980) indicates that this deformation zone, which he refers to as the Favourable Lake-McDowell Lake Fault Zone, forms the western boundary of the greenstone belt. According to Osmani and Stott (1988), this fault zone is approximately 3 km wide in the McDowell Lake area at the south end of the North Spirit Lake Greenstone Belt. Wood (1980) has identified a minimum of six discrete faults within the fault zone that are characterized by extensive shearing and mylonitization. Wood (1980) has also identified a number of additional northwest-striking fault zones farther to the east within the central portions of the greenstone belt. These structures may represent splays related to the main Bear Head Fault Zone, and include the Wokokotai Lake and Roseberry River Faults. Wood (1980) has also identified a number of northeast-striking faults in the area. Two major isoclinal folds (South Bay Syncline and Hewitt Lake Anticline) having northwest-trending axes have been identified to the south of North Spirit Lake by Wood (1980). Wood (1980) also suggests the presence of a number of northeast-trending cross-folds to the south of North Spirit Lake. As is typical for most Archean-age greenstone belts in Ontario, the dips of stratigraphic marker horizons and foliation in the area south of North Spirit Lake is near-vertical (Wood 1980). Although the structural complexity of the area has resulted in variable bedding and foliation strike directions, mapping by Wood (1980 and 1988) indicates that orientations of these features are typically subparallel and that the dominant stike direction is northwest. These observations are not surprising given the presence of a major northwest-striking fault zone and northwest-trending isoclinal folds in the area.

Lithology

Lithology Comments

May 23, 2007 (Mark Puumala) - The supracrustal rocks in the area to the south of the North Spirit Lake Fault consist of a wide range of lithologies that have been assigned to five separate tectonic assemblages by Thurston et al. (1991). The oldest of these assemblages is the Disrupted Assemblage, which consists of a sequence of approximately 2900 to 2950 Ma migmatized metavolcanic rocks (basal mafic flows overlain by intermediate to felsic flows and pyroclastics) that is capped by a significant thickness of iron formation. The Disrupted Assemblage is overlain to the west by rocks of the <2896 Ma Nemakwis assemblage, which consists of a basal unit of quartz arenite overlain by a mafic to ultramafic (including spinifex textured and pillowed komatiites) metavolcanic-dominated sequence that also includes intercalated iron formation and tuff layers. Nemakwis Assemblage rocks have also been identified in the Central portion of the belt in the vicinity of Hewitt Lake. The Nemakwis Assemblage is unconformably overlain by rocks of the Makatiamik Assemblage, which is a thick, quartz-rich, generally fining-upward clastic metasedimentary rock-dominated sequence that is overlain by iron formation, marble and carbonatized mafic metavolcanic flows and serpentinite. The Makatiamik Assemblage is overlain by much younger (2735 Ma) rocks of the Hewitt Assemblage. The lower portions of the Hewitt Assemblage consist of mafic metavolcanic and dacitic flows and pyroclastic rocks. These metavolcanics are overlain by a metasedimentary rock sequence that is dominated by clastic sediments, but also contains minor iron formation, marble and chert. The youngest rocks that have been identified in this area (2731 Ma Bijou Point Complex) are located at the south end of North Spirit Lake and consist of intermediate to felsic metavolcanic rocks, associated metasedimentary rocks and a subvolcanic quartz diorite to granodiorite intrusion. The intrusive rocks of the Bijou Point Complex have been classified by Stone (1998) as belonging to the sanukitiod suite. Other late sanukitiod intrusions have been mapped by Stone (1998) near the southeast and western ends of the greenstone belt. The eastern boundary of the North Spirit Lake Greenstone Belt is marked by the Hawthorne Batholith, which is classified by Stone (1998) as a hornblende tonalite to granodiorite intrusion. The western portions of the belt are bounded by felsic intrusive rocks that have been given a number of classifications by Stone (1998). A notable intrusion is the peraluminous 2697 Ma Margo Pluton. This pluton parallels Margo Lake, and is located immediately adjacent to a wedge of metasedimentary rocks that extends westward from the greenstone belt.

Mineralization

Mineralization Comments

Jan 17, 2012 (Mark Puumala) - The Crown Trust banded magnetite-chert iron formation is located in the eastern portion of the North Spirit Lake Greenstone Belt in rocks of the Nemakwis Assemblage (Thurston et al. 1991). The deposit, which has never been fully delineated (Wood 1977), is located in an area that extends from Peridotite Bay of North Spirit Lake in the northwest, to Wapisipi Lake in the southeast. Low (1953) indicated that the deposit consists of irregular bands of iron formation within an area approximately 1220 m wide and greater than 1600 m long. The iron formation in this area is interlayered with mafic and ultramafic metavolcanic rocks (Wood 1977), and has been intruded by granitic rocks (Low 1953). Individual iron formation units are indicated by Low (1953) to be up to 305 m wide, while Wood (1977) indicates that the aggregate thickness of iron formation is on the order of 800 m. Based on the results of diamond drilling carried out on the deposit by Crown Trust prior to 1973 (including AFRI # 53C07NW0019), Wood (1977) indicates that the deposit is likely to contain approximately 1,300,000 tons of ore per vertical foot, to a minimum depth of 210 m. However, the deposit is located in an area of significant structural complexity which Wood (1977) indicates will necessitate additional detailed geological mapping and diamond drilling to allow for the accurate delineation of reserves. 2011: 34.16 wt % Fe average of a total of 17 grab samples

Mineral Record Details

References

Map - North Spirit Lake, Kenora District

Publication Number: M2362 Scale: 1:31,680    Date: 1977

Author: Wood J.

Publisher Name: Ontario Division of Mines

Location:

MonoMap - Precambrian Geology of the Berens River Area, Northwestern Ontario

Publication Number: OFR5963 Date: 1998

Author: Stone D.

Publisher Name: Ontario Geological Survey

Location:

MonoMap - Geology of North Spirit Lake area, District of Kenora (Patricia Portion)

Publication Number: R150 Page: 50-52  Date: 1977

Author: Wood J.

Publisher Name: Ontario Division of Mines

Location:

Part - Geology of the North Spirit Lake area

Publication Number: ARV47-07.002 Page: 54-56  Date: 1997

Author: Bateman J.D.

Publisher Name: Ontario Dept. of Mines

Location:

MonoMap - Geology of the Hewitt Lake area, District of Kenora (Patricia Portion)

Publication Number: R186 Page: 103-104  Date: 1981

Author: Wood J.

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:

Mono - Iron deposits of Ontario

Publication Number: MDC011 Page: 234  Date: 1968

Author: Shklanka R.

Publisher Name: Ontario Dept. of Mines

Location:

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For detailed information regarding this mineral record please contact the Red Lake Resident Geologist District Office