Thunder Bay North deposit (Current Lake zone), Greenwich Lake Area, Thunder Bay District, Ontario, Canadai

Regional Level Types
Thunder Bay North deposit (Current Lake zone)	Deposit
Greenwich Lake Area	Area
Thunder Bay District	District
Ontario	Province
Canada	Country

The TBN project (700 km²) is in the northern part of the 1.1 billion years old Proterozoic Midcontinent Rift region, an important emerging Ni-Cu-PGM province. The geology of this region is analogous to that of the giant Norilsk - Talnakh Ni-Cu-PGM camp in Russia. Mineralization has been known in the Midcontinent Rift for many years; however, up until recently it appeared to be mostly of relatively low grade. The Eagle (3.6Mt at 3.5% Ni, 3.0% Cu & 1.6g/t Pt+Pd+Au) and Tamarack discoveries in the USA, as well as Magma's TBN discovery, all made this decade, have demonstrated that higher grade mineralization is also present and that the province has significant potential to become a major North American Ni-Cu-PGM camp. Ultramafic boulders containing abundant disseminated sulphides were located within the southern part of the TBN claim block in July 2001. The glacially transported boulders are large (metre-scale) and angular indicating a proximal source. The boulders are mainly composed of peridotite containing 2-5% disseminated sulphides. Assays range from 1.6g/t Pt+Pd+Au, 0.2% Ni & 0.2% Cu to 9.5g/t Pt+Pd+Au, 0.3% Ni & 1.0% Cu and average 3.8g/t Pt+Pd+Au, 0.2% Ni & 0.4% Cu. The Pt:Pd ratio of the mineralization is characteristically 1:1. Another extensive occurrence of boulders was found on the east shore of Current Lake in 2006. These boulders appear to be in-situ, with some minor movement, possibly due to frost heave. Assay values for 22 samples of these boulders ranged up to 9.4g/t Pt+Pd+Au, 1.2% Cu & 0.4% Ni with an average of 2.3g/t Pt+Pd+Au, 0.2% Cu & 0.2% Ni. An aeromagnetic survey of the TBN claim block was undertaken in July 2006 and identified a prominent linear anomaly beneath Current Lake. This was interpreted to reflect the source intrusion for the mineralized peridotite boulders. The survey also located an intense reversely magnetised "bulls-eye" magnetic anomaly southeast of Current Lake on the adjacent Beaver Lake claim. Drilling of the magnetic anomaly at Current Lake in December 2006 confirmed that it reflects a peridotite intrusion and is the source of the mineralised glacial boulders. The discovery drill-hole, TBND001, completed in December 2006 returned an intersection of 10.5m @ 2.8g/t Pt+Pd+Au, 0.5% Cu & 0.3% Ni.
Current Lake zone is 30m x 30m to 50m wide and 70m tall (and is in general, flat lying). The zone consists of olivine metagabbro with disseminated pyrrhotite, pentlandite, chalcopyrite, pyrite, rare cubanite and violarite. Beaver Lake Zone exhibits a shallow east-southeasterly plunge and increases from 100m width and 15m thickness to 550m width and 200m thickness towards the east. Mineralization in olivine melagabbro and lherzolite. Mineralization is disseminated similar to the Current Lake Zone.

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References