Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000001311

Record: MDI000000001311

General

Commodities

Primary Commodities: Lithium

Secondary Commodities: Tantalum

Location

Township or Area: Root Bay Area

Latitude: 50° 55' 28.58"    Longitude: -91° 34' 18.96"

UTM Zone: 15    Easting: 600367   Northing: 5642411.99    UTM Datum: NAD83

Resident Geologist District: Thunder Bay North

NTS Grid: 52J13NE

Point Location Description: Grab sample of outcrop

Location Method: Field Visit with GPS

Exploration History

2006-07: R. Ross carried out prospecting. 2011: Rockex flew heliborne EM and magnetic geophysical surveys. 2016: Ardiden carried out channel sampling. 2022: Solstice Gold Corp. optioned the property to Green Technology Metals Ltd. 2023: Green Technology Metals drilled 45 DDH totalling 7,668 m.

Assessment Work on File

Geology

Province: Superior

Subprovince: Uchi

Belt: Lake St. Joseph

Geological Age: Archean  

Geology Comments

Jul 17, 2023 (Therese Pettigrew) - The Root Lake Lithium Project is located the boundary between the Uchi Domain and the English River subprovince is defined by the Sydney Lake - Lake St. Joseph Fault, a steeply dipping brittle ductile fault zone over 450km along strike and 1-3 km wide. It is estimated that the fault had accommodated 30 km dextral, transcurrent displacement and 2.5 km of south side up normal movement. The English River Terrane is an east-west trending subprovince composed of highly metamorphosed sedimentary rock, including turbiditic sediments and oxide iron formations, abundant granitoid batholiths, mafic to ultramafic plutons and rare felsic to intermediate metavolcanic rock. The pegmatites are hosted within an Archean package of metabasalts of the Lake St. Joseph greenstone belt. The metabasalts are themselves sandwiched in a 300 m wide corridor flanked in the south by met-sediments and in the north by more metaediments hosting banded iron formation units. The contacts between the metabasalts and the metasedimentary units are thought to be steeply dipping to sub-vertical. The Root Bay pegmatite is exposed approximately 60 m along strike, is 10m wide (Smyk et al., 2008; Magyarosi, 2016) and follows the presumed trace of the Lake St. Joseph Fault (Smyk et al., 2008). The pegmatites are hosted in foliated, locally pillowed mafic metavolcanic rock that contain metasomatic near the contact of the pegmatite (Magyarosi, 2016) (Green Technology Metals ASX Announcement June 7, 2023).

Lithology

Lithology Comments

Jun 08, 2021 (Therese Pettigrew) - The length of the exposed dike is approximately 60 m with a width of 10 m. The minerals in the pegmatite dike include white albite, grey quartz and pale green spodumene crystals up to 10 cm in length. The deposit model is that the spodumene occurs in Li-Cs-Ta (“LCT”) rare-element pegmatite dikes. LCT pegmatites are associated with S-type, peraluminous (Al-rich), quartz-rich granites. S-type granites crystallize from a magma produced by partial melting of pre-existing sedimentary source rock. They are characterized by the presence of biotite and muscovite, and the absence of hornblende. Rare-element pegmatites derived from a fertile granite intrusion are typically distributed over a 10 to 20 km2 area within 10 km of the fertile granite. A fertile granite is the parental granite to rare-element pegmatite dikes. The parental magma of the Root Lake pegmatites may be the chemically evolved southeast arm of the Allison Lake batholith, located approximately 10 km west of the pegmatite dikes, or the Root Bay pluton, located approximately 10 km east of the pegmatite dikes (Assessment report 20000013876).

Mineralization

Mineralization Comments

Mar 12, 2013 (Robert Cundari) - A newly discovered pegmatite body is exposed (600367 E / 5642412 N) on the eastern side of a logging road along the prominent ridge that follows the presumed trace of the Lake St. Joseph Fault. It is hosted by foliated (090º), locally pillowed, mafic metavolcanic rocks. Outcrop distribution suggests that the dyke is perhaps 10 m wide at this location and strikes 170º. No exogenic features were noted in the host rocks along the limited, exposed contact. The dyke is characterized by coarse white albite, grey quartz and pale grey-green spodumene crystals up to 10 cm long. The dyke also displays spectacular colloform banding developed in fine-grained quartz and feldspar. Samples were sent to Fred Breaks (Precambrian Geoscience Section, OGS) and Andy Tindle (The Open University, Milton Keynes, U.K.) for analysis. Among the minerals that were identified were ferrotapiolite (Fe(Ta,Nb)2O6), columbitetantalite (Fe,Mn,Mg)(Nb,Ta)2O6), garnet, muscovite and tourmaline (Andy Tindle, The Open University, Milton Keynes, U.K, personal communication, 2007). Tantalum contents reach 70 wt% Ta2O5 in the ferrotantalite and 79 wt% in the ferrotapiolite. Most grains are very small, but a couple display oscillatory and/or patchy elemental zoning. Garnet is intermediate in composition between the spessartine and almandine end-members. The muscovite contains very low cesium values and has a slightly elevated rubidium content. Tourmaline is schorl and shows no indication of lithium enrichment (ibid) This pegmatite dyke is likely related to those found approximately 9 km to the west at Root Lake (Breaks, Selway and Tindle 2001). The Root Lake Pegmatite Group comprises 4 albite-spodumene-type pegmatites (including the McCombe 1 and 2 dykes), which are perhaps genetically related to the peraluminous, S-type, Root Bay granite pluton. Initial geochemical data suggest that the newly discovered pegmatite may be more chemically primitive than the McCombe dykes and perhaps closer geochemically to the parental, pegmatitic granite (Fred Breaks, OGS, personal communication, 2007).

Jun 08, 2021 (Therese Pettigrew) - The exposed Root Bay pegmatite dike is zoned with spodumene pegmatite (approximately 35% spodumene 5-6 cm long) in the center, followed by two K-feldspar rich zones of different crystal sizes and a wall zone composed of an unidentified mineral with comb structure. The host rock is metasomatized and contains holmquisite. 14 m of spodumene pegmatite and aplite with 1.67 wt% Li2O including 3 m with 2.13 wt% Li2O in channel RootBay-CH-16- 01 (Assessment report 20000013876). DDH RG-23-001 returned 67.1 m @ 1.13% Li2O from 60.9 m. RB-23-003 returned 12.1 m @ 1.30% Li2O from 67.4 m. RB-23-005 returned 6.6 m @ 1.47% Li2O from 129.2 m, 4.5 m @ 1.34% Li2O from 140.5 m and 2.1 m @ 1.09% Li2O from 149.0 m (Green Technology Metals ASX release March 31, 2023). Drilling has revealed multiple, shallow-dipping LCT pegmatites up to 18 m thick, with lithium grades up to 1.73% Li2O. 13 stacked pegmatites have been identified and defined to over 200 m depth and 1,300 m along the Root Bay trend, with a northerly strike length of up to 300 m. The pegmatites all dip to the east at approximately 35 degrees (Green Technology Metals ASX Announcement June 7, 2023).

Mineral Record Details

Site Visit Information

Date: Jul 02, 2007

Geologist: M Smyk

Notes: Site visit by Mark Smyk

References

Mono - Report of Activities 2007, Resident Geologist Program, Thunder Bay North Regional Resident Geologist Report: Thunder Bay North District

Publication Number: OFR6217 Page: 18-20  Date: 2008

Author: Smyk M.C., White G.D., Puumala M.A., Hinz P., Komar C.L.

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