Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000000192

Record: MDI000000000192

General

Commodities

Primary Commodities: Gold

Location

Township or Area: Tarp Lake Area

Latitude: 51° 33' 14.37"    Longitude: -90° 4' 35.32"

UTM Zone: 15    Easting: 702670   Northing: 5715485    UTM Datum: NAD83

Resident Geologist District: Thunder Bay North

NTS Grid: 52O09SE

Point Location Description: Location from assessment file map in AFRO# 2.32421.

Location Method: Data Compilation

Assessment Work on File

Geology

Province: Superior

Subprovince: Uchi

Terrane: North Caribou

Domain: Uchi

Belt: Pickle Lake

Geological Age: Mesoarchean  

Geology Comments

Dec 18, 2006 (Mark Puumala) - The Tarp Lake area gold prospects and occurrences are located in the northern portion of the Pickle Lake Greenstone Belt. These occurrences are found within a mafic metavolcanic rock dominated supracrustal sequence identified by Young (2003) as being part of the > 2860 Ma Pickle Crow Assemblage. According to Young (2003), the Pickle Crow assemblage is dominated by massive and pillowed mafic metavolcanic flows with subordinate (likely synvolcanic) gabbroic sills. MacTavish (2006) describes the mafic metavolcanic flows as being commonly well-foliated to schistose, amphibolitized, and often finely-amygdaloidal. In addition, MacTavish (2006) indicates that the mafic metavolcanics include units of pillow and hyaloclastite breccia. The gabbroic sills are described by MacTavish (2006) as fine- to coarse-grained gabbro, melagabro and ferrogabbro sills up to 200 m thick. The mafic metavolcanics are intercalated with thin, laterally continuous banded iron formation and small, discontinuous lenses of intermediate to felsic metavolcanics. A significant 90 to 125 m thick northeast-trending unit of felsic to intermediate tuff breccia to pyroclastic breccia has been reported in this area by MacTavish. Relatively thin units (up to 70 m thick) of clastic metasedimentary rocks have also been reported by MacTavish (2006). All lithologies are intruded by semi-concordant feldspar porphyry dikes. These dikes are reported by MacTavish (2006) to vary widely in thickness and lateral continuity. MacTavish (2006) also indicates that all lithologies are crosscut by late biotite lamprophyre dikes that are up to 5 m in thickness. One of these dikes is reported to contain ultramafic and country rock xenoliths, red garnets and greenish diopside. Stratigraphy in the Tarp Lake area generally faces toward the northwest, except where asymmetric folding (mainly further to the southeast in the Pickle Crow mine area) has caused reversals in the younging direction (Young 2003). The dominant geological structure in the Tarp Lake area is the Tarp Lake Shear Zone. This structure strikes northeast and forms a wide, diffuse and anastamosing deformation zone that is poorly exposed and characterized (MacTavish 2006). The mafic metavolcanic rocks affected by this shear zone are characterized by moderate to intense carbonatization, sericitization and local silicification (MacTavish 2006). This alteration zone hosts the numerous gold occurrences throughout the area. Many of the more significant gold prospects appear to be located where the Tarp Lake Shear Zone is intersected by splays and/or later fault/shear zones, or relatively competent lithological units such as porphyry intrusions, gabbro and iron formation. The cross-cutting deformation zones are most commonly reported to strike approximately northwest, east-west and north-northeast. Similar complex faulting/shearing patterns have been noted nearby by MacQueen (1987) in the vicinity of the Pickle Crow gold mine, and by McAuley and Winter (1990) in the vicinity of a number of gold occurrences in the July Falls area.

Lithology

Mineralization

Mineralization Comments

Dec 18, 2006 (Mark Puumala) - The West Vein is described by Potts (1992) as a 0.3 to 2.0 m wide milky-white quartz vein with minor carbonate fracture filling. The host rock is described as a pervasively carbonatized and chloritized mafic metavolcanic flow. The vein strikes approximately 110, with a near-vertical dip. Ladder veins with an orientation of 020/82 have been noted by Potts (1992) to branch off the main vein. The vein has been traced over a strike length of 70 m. The vein is reported by Potts (1992) to pinch out toward the east (near the contact with a quartz-feldspar porphyry dike), while it remains open to the east where it drops into a swamp. Although the overall sulphide content of the West Vein is reported to be low, Potts (1992) notes that chalcopyrite and pyrite occur in localized fine-grained masses containing 5 to 8 % sulphides. These sulphide-rich zones appear at surface as hematitic patches. The most favourable reported assay from this occurrence is 4.9 g/t Au from a Homestake Canada grab sample of hematitic material with 1 to 2 % pyrite (Potts 1992). Homestake also reports an assay of 0.65 g/t from a 1.0 m channel sample that was collected across the vein.

Mineral Record Details

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