Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000001775

Record: MDI000000001775

General

Commodities

Primary Commodities: Copper

Location

Township or Area: Garden Lake Area

Latitude: 49° 32' 45.68"    Longitude: -89° 51' 52.03"

UTM Zone: 16    Easting: 292800   Northing: 5492100    UTM Datum: NAD83

Resident Geologist District: Thunder Bay South

NTS Grid: 52H12SW

Point Location Description: Trench location from Map P3422

Location Method: Data Compilation

Access Description: Access to the Bumbu occurrence is obtained by travelling southwest approximately 10.5 km along Grew Road from Highway 811 to the intersection with a secondary logging road. Travel approximately 800 m southeast to the occurrence trench, which is located on the north side of the road.

Exploration History

1983-87: Prospecting, trenching and sampling by C. Bumbu. 1987: Airborne magnetic and electromagnetic surveys by Garden Lake Resources. 1991: Prospecting, trenching, sampling, airborne and ground geophysical surveys and geological compilation by Weaver Lake ResourcesCorporation. 1993-97: Prospecting, trenching and sampling by C. Bumbu and J. Martin.

Assessment Work on File

Mineralization Comments

Oct 21, 2014 (Mark Puumala) - The following discussion of mineralization found at the Bumbu showing during a 1991 exploration program carried out by Weaver Lake Resources is excerpted from Hart (2000 OFR6037). For more details see AFRI52H12SE0012. In 1991, Weaver Lake Resources completed a program of gridding, horizontal loop EM and magnetic surveys, further prospecting and trenching (Pitman, 1991). Detailed mapping and sampling was initiated, complimented by a thin section study. The units in the trenches are described as a chloritized and brecciated stringer sulphide zone located at the contact between pillowed mafic metavolcanic and felsic metavolcanic rocks. Along strike with the stringer zone 75 are massive sulphide lenses varying from 0.6 to 0.8 metres in width, and hosted by altered mafic metavolcanic rocks and metasediments / felsic tuffaceous rocks. Sulphide bearing siliceous metasediments and banded cherty-magnetite iron formation are located further along strike to the east, in the Conick Lake area. The metavolcanic rocks are highly altered and recrystallized obscuring the original rock types. The mafic metavolcanic rocks are described as being hornblende, chlorite, plagioclase, quartz, epidote, with minor opaques, typical of upper greenschist facies regional metamorphism. A sample from the easternmost northern trench contained an amphibole rich unit composed of Ti-hornblende/actinolite with minor plagioclase, quartz, biotite, and chlorite. This unit was interpreted to be a metamorphosed calcareous sediment or tuff. The whole sequence is capped by pillowed mafic metavolcanic rocks to the south. A grab sample assaying 6.11% Cu and 983 ppm Zn was collected from the southern trench (Pitman, 1991). Generally, samples from the northern trenches ranged from 71 to 260 ppm Cu and <50 to 163 ppm Zn. The following description of the geology of the Bumbu occurrence is excerpted from Hart (2000 OFR6037). The rocks currently exposed in the trenches are highly oxidized and rust stained obscuring many of the fine features. A series of massive, gabbroic textured flows and pillowed flows with rare flow top breccias and 5 to 10 cm wide iron formations are exposed in the trenches. The massive flows are usually metamorphosed to an upper greenschist to lower amphibolite facies containing medium to coarse grained hornblende. The chert-magnetite iron formation commonly caps the flow top breccia, but south of the road the iron formation also occurs as interpillow lenses. The sulphide mineralization is associated with iron formation and flow top breccias, and consists of massive to semi-massive 0.2 to 0.3 m wide lenses of pyrite and pyrrhotite with minor chalcopyrite. The lenses occur in highly fractured massive to pillowed mafic metavolcanics, often in close proximity to thin beds of iron formation. The silicified horizons were not observed in the trenches but occur stratigraphically above and below the sulphide mineralized units. The sulphide . iron formation association, and strata-bound silicification is interpreted to indicate a hydrothermal origin for the sulphides, with later remobilization into fractures during metamorphism and deformation. The hydrothermal activity probably continued to a lesser degree after deposition of these units as sulphide was observed in originally porous units overlying the trenches. This includes 2 to 3 cm fragments of sulphide in flow top breccia and 1 to 2 % fine grained pyrite in interpillow hyaloclastite south of the trenches, and interpillow pyrite along strike west of Conick Lake. Five samples of the heavily mineralized to semi-massive sulphide mineralization were collected from the trenches (samples 18a, b, tr2, tr3, tr4; Table 4). The best assay was 958 ppm Cu, 180 ppm Zn, 148 ppm Ni in a semi-massive sulphide sample.

Mineral Record Details

References

MonoMap - Precambrian Geology, Garden Lake Area

Publication Number: OFR6037 Scale:     Date: 2000

Author: Hart T.R.

Publisher Name: Ontario Geological Survey

Location:

Mono - Garden-Obonga Lake Area High Density Lake Sediment and Water Geochemical Survey, Northwestern Ontario

Publication Number: OFR6009 Scale:     Date: 2000

Author: Jackson J.E., Dyer R.D.

Publisher Name: Ontario Geological Survey

Location:

MonoMap - Geology of the Garden Lake area, District of Thunder Bay

Publication Number: R025 Scale:     Date: 1997

Author: Milne V.G.

Publisher Name: Ontario Dept. of Mines

Location:

Data - Ontario Airborne Geophysical Surveys, Magnetic and Electromagnetic Data, Garden-Obonga Area

Publication Number: GDS1105 Scale:     Date: 2000

Author: Ontario Geological Survey

Publisher Name: Ontario Geological Survey

Location:

Map - Precambrian Geology, Garden Lake Greenstone Belt (West Half)

Publication Number: P3422 Scale: 1:20,000    Date: 2000

Author: Hart T.R.

Publisher Name: Ontario Geological Survey

Location:

Map - Garden Lake area, Thunder Bay District

Publication Number: M2058 Scale: 1:63,360    Date: 1997

Author: Milne V.G.

Publisher Name: Ontario Dept. of Mines

Location:

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