Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000002867

Record: MDI000000002867

General

Commodities

Primary Commodities: Gold

Location

Township or Area: Castlewood Lake Area

Latitude: 49° 51' 6.65"    Longitude: -87° 43' 15.93"

UTM Zone: 16    Easting: 448163   Northing: 5522408    UTM Datum: NAD83

Resident Geologist District: Thunder Bay North

NTS Grid: 42E13SE

Point Location Description: DDH 09GE007A from Assessment report 20000004636

Location Method: Based on Assessment

Exploration History

2008-09: Sage Gold carried out prospecting, stripping, sampling, mapping, ground magnetic and HLEM surveys, and drilled 17 DDH totalling 996 m. 2010: Sage Gold conducted ground magnetic and VLF-EM surveys.

Assessment Work on File

Geology

Province: Superior

Subprovince: Wabigoon

Terrane: Eastern Wabigoon

Belt: Onaman-Tashota

Geological Age: Archean  

Lithology

Lithology Comments

Dec 01, 2021 (Therese Pettigrew) - The Jacobus East Property is underlain by intermediate volcanic rocks (andesites and dacites) of the Elmhirst-Rickaby and Marshall Assemblages (ca. 2740 Ma) that were intruded by the Elmhirst intrusive suite ca. 2736 Ma. Although not observed in outcrop, compilation of previous mapping as well as the presence of rafts within the Elmhirst intrusion suggests that andesites of the Elmhirst-Rickaby Assemblage exist under the northeast section of the mapped area. Rafts suggest the Elmhirst-Rickaby Assemblage is composed of massive to pillowed flows of andesites, which have undergone regional greenschist facies metamorphism identified by chlorite and localized skarn-like metamorphism related to emplacement of the Elmhirst intrusion resulting in magnetite recrystallization of pillow selvages. Dacites of the Marshall Assemblage overlie the andesites of the Elmhirst-Rickaby Assemblage and are present in the western half of the mapped area. Outcrop exposures of the Marshall Assemblage display two primary lithologies. In the southwest portion of the map area, the Marshall Assemblage is composed of dacitic, heterolithic pyroclastic tuff-breccias. Heterolithic breccia fragments range in size from 5-30 cm and include massive dacite, feldspar porphyry and hornblende-feldspar porphyritic clasts, typically clast supported in a dacitic tuff matrix. Bedding and younging directions were unobtainable as breccia fragments display compression and transposition into regional deformation fabrics. In the northwest portion of the mapped area the Marshall Assemblage is composed of massive to bedding dacitic crystal-lithic lapilli-tuff. Dominantly the lapilli-tuff is composed of feldspathic ash with minor feldspar lapilli. The unit is generally massive, presumably related to the obliteration of primary bedding textures due to transposition and metamorphism. The polyphase Elmhirst intrusion is the dominant lithology underlying the mapped area, intruding into both the Elmhirst-Rickaby and Marshall Assemblages. The earliest phase of the intrusion includes fine grained feldspar porphyritic diorite followed by the most volumetrically significant, medium grained, equigranular ferrodiorite/quartz diorite phase of the intrusion. Gabbro pods, related to magmatic segregation are locally associated with this phase of intrusive emplacement. Later phases of the Elmhirst intrusion include fine grained, equigranular granodiorite along the northern margin of the intrusions and coarse feldspar +/- hornblende porphyritic granodiorite within north-south corridors along the southern margin of the mapped area, a large northwest trending structural corridor cross-cutting the main phase of the intrusion and a large pod, including west trending apophyses, in the southwest part of the mapped area (Assessment report 20000004636).

Mineralization

Mineralization Comments

Dec 01, 2021 (Therese Pettigrew) - Gold mineralization identified to date on the property occurs primarily at the Golden Extension Showing. The mineralization consists of quartz & pyrite +/- chalcopyrite, carbonate, sericite & chlorite veins and their altered, sulphidized and sometimes stockworked and sheared selvedges. Much if not most of the gold occurs in a coarse free state associated with variable (trace to 10%) amounts of pyrite and small amounts (trace to 2%) of chalcopyrite and magnetite. Individual veins range in width from sub cm to nearly 2m trending west-northwest-eastsoutheast or east-west, however, the vein system appears to have an overall northwest trend. The 2008-2009 stripping program has outlined a system with a discontinuous strike length of approximately 850 m which is roughly 400 m broad. Individual veins often pinch and swell along strike likely related to post-mineralization shearing and boudinage. Vein selvedges and some of the shear zones can be several metres wide and are typically strongly deformed and variably altered to sericite-chlorite-hematite-carbonate-pyrite which habitually yield lower gold values than the veins. Stockwork style mineralization is present at a number of locations proximal to larger veins overprinting the bordering diorite or intermediate volcanic rocks. Grab samples collected in 2009 returned assays of 2.17 to 59.6 g/t Au. DDH 09GE007a retuned up to 14.9 g/t Au from a vein at 8.64-9.1 m containing visible gold and chalcopyrite. DDH 09GE007b intersected the target vein between 13.51-15.08 m and yielded a gold value of 1.49 g/t Au including 5.38 g/t Au over 0.30 m. DDH 09GE011 intersected the vein between 6.68-7.07 m. The vein contained visible gold and returned 4.01 g/t Au (Assessment report 20000004636).

Alteration Comments

Dec 01, 2021 (Therese Pettigrew) - Alteration of the Elmhirst-Rickaby Assemblage is pervasive chlorite, presumably related to greenschist regional metamorphism. Alteration of the Marshall Assemblage is silica-white mica also related to regional metamorphism. Alteration of the Elmhirst intrusion is dominantly chlorite associated with mylonitization within shear zones and later hydrothermal activity during quartz vein emplacement. A good example of this is at the Boundary stripping where demagnetization and chlorite alteration increase over tens of meters leading into the intersection of D2 and D3 shear zones (Assessment report 20000004636).

Assay Samples

Mineral Record Details

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Ministry Contact Information

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