Opal Lake Ni-Cu occurrence, Nahlin River area, Atlin Mining Division, British Columbia, Canadai

Regional Level Types
Opal Lake Ni-Cu occurrence	Occurrence
Nahlin River area	- not defined -
Atlin Mining Division	Division
British Columbia	Province
Canada	Country

The Opal Lake Ni-Cu occurrence is located at "Opal Lake", about 9 kilometres east of the Nahlin River and 4.5 kilometres west of the “Old Telegraph Trail”, approximately 100 kilometres north of the community of Telegraph Creek, British Columbia.
The following quote is from B.C. Government site “Minfile”- Minfile No. 104J 001, current to 2013:
“The Opal Lake property covers a portion of a northwest trending regional structure known as the Nahlin fault, which cuts through Carboniferous-Jurassic Cache Creek Complex strata. Rock types on the property comprise upper Mississippian-Permian Horsefeed Formation limestone and dolomitic limestone; Mississippian-Triassic Kedahda Formation chert and cherty argillite; Mississippian-Pennsylvanian Nakina Formation andesitic, fine-grained metabasalt; and upper Mississippian-Permian serpentinized peridotite and serpentinite.
Along the Nahlin fault, nickel mineralization (millerite) and low gold concentrations (up to 0.5 gram per tonne) are associated with a significant zone of listwanitic-ankeritic alteration. The listwanite is a brilliant bright green and white rock of alternating layers of quartz-carbonate and fuchsite-carbonate. Seams and disseminations of magnetite also occur. The ankerite is buff to rust-brown, medium to fine grained with occasional faint foliation fabric.
Three zones have been identified on the property: Nickel City, Camp and Pond. At the Nickel City zone, 500 metres west of "Opal Lake", millerite, pyrite and minor fine black sulphides (marcasite? or arsenopyrite?) reheal multi-episodic opaline quartz-chalcedony- ankerite breccias in a structurally disrupted zone of the Nahlin fault. The breccias are characterized by matrix supported, fine grained, highly altered clasts, which themselves are brecciated. Millerite and pyrite are confined to the vuggy, black chalcedonic quartz matrix of the breccias. The breccias and veins generally strike 040 to 050 degrees and dip steeply to the west. The highest gold values (up to 0.5 gram per tonne) were obtained from a zone of small opaline and black chalcedonic quartz veins cutting ankerite alteration in serpentinite.
The Camp zone is located on the east end of "Opal Lake", where there are several exposures of bright green and buff fuchsite-bearing listwanite. The listwanites are generally moderately foliated and host anastomosing magnetite seams which roughly parallel foliation. Quartz and dolomite veinlets and stockwork crosscut the listwanite foliation. Elevated gold and arsenic values tend to be associated with these veins.
The Pond zone is southwest of Tedideech Lake where an outcrop on the north shore of a small pond exposes weakly foliated fuchsite-bearing listwanite. No mineralization was observed in the listwanite or in late-stage quartz veinlets crosscutting foliation.”
Comments by Giles Peatfield regarding some of the minerals reported:
Ankerite: This is based on reporting in Minfile, with no specific reference.
Bravoite: Archer (1957) reported that bravoite was confirmed by an X-ray photograph interpreted by Dr. R. M. Thompson.
Chalcocite: Lawrence (1959) reported chalcocite, associated with millerite or native copper, and confirmed microscopically using etch tests.
“Fuchsite”: This is reported in Minfile, with no more detail. It is commonly thought that green mica in “listwanite” is fuchsite, but this is not always true, so this mineral should be regarded as tentative here.
Violarite: Archer (1957) reported that violarite was confirmed by X-ray.

Other Databases

Link to British Columbia Minfile:	104J 001

Other Regions, Features and Areas containing this locality

References