The Chopper 5 copper occurrence is situated at the headwaters of the Gataga River, 14 kilometres south of Churchill Peak in the mountainous Muskwa Ranges of the Northern Rocky Mountains (Assessment Report 2640).
The occurrence is in a region known as the Muskwa Anticlinorium, a major north-northwest–trending structure characterized by large, folded thrust sheets that expose rocks as old as Middle Proterozoic (Helikian), as well as Paleozoic rocks (Geological Survey of Canada Map 1343A; Geological Society of America, Geology of North America, Volume G-2, page 639). All belong to Ancestral North America (Geological Survey of Canada Map 1713A). The Middle Proterozoic rocks are pre-Windermere Supergroup, and are known as the Muskwa Assemblage, a thick package of carbonate and clastic rocks that has been divided into a number of formations (Geological Society of America, Geology of North America, Volume G-2, page 111). All rocks are gently folded, and some have slaty cleavage. Northwest- to northeast-striking, steeply dipping diabase and gabbro dikes are common in the region. The dikes are Proterozoic because they are truncated by a Lower Cambrian unconformity (Geological Survey of Canada Memoir 373).
The Chopper 5 occurrence is situated in the Gataga Formation, not far from the top of the underlying Aida Formation, both of the Muskwa Assemblage. The Gataga Formation consists of slaty, carbonaceous shale, mudstone, siltstone and sandstone (Assessment Report 2640; Geological Survey of Canada Memoir 373, Paper 67-68). The Aida Formation comprises slaty, dolomitic mudstone and siltstone, argillaceous limestone, and dolostone. These rocks generally strike 330 degrees and dip moderately southwest. Numerous diabase dikes intrude this area, striking approximately 340 degrees and dipping steeply southwest. They range in thickness from a few metres to tens of metres. Centimetre-scale contact metamorphism next to the dikes is shown by epidote, actinolite, diopside and marble. Immediately southwest of the Chopper claim group are unconformably overlying siliceous sandstone and quartzite of the Lower Cambrian Atan Group.
Fault and shear fracture zones occur locally in the sedimentary rocks and less commonly along dike margins. They strike north-northwest and dip moderately to steeply west. Many of these zones contain quartz-carbonate veins, ranging in thickness from 2.5 centimetres to 2.75 metres. A few of these veins are mineralized with chalcopyrite and minor galena, pyrite and malachite. This occurrence is centred on Showing Number 3, a mineralized vein in the Chopper 5 claim (Assessment Report 2640). This vein ranges in width from 15 to 30 centimetres and is exposed intermittently for approximately 70 metres along a small fault. It strikes approximately 350 degrees and dips vertically. Mineralization is erratic and discontinuous here. Chip sample C-8 assayed 11.27 per cent copper over 30 centimetres (Assessment Report 2640, Geological Map). A few other small, mineralized veins occur approximately 100 metres to the north.
Work History
In 1970, Windermere Exploration Ltd. completed a program of geological mapping and rock sampling on the area as the Chopper claim group. Also at this time, Fortune Channel Mines Ltd. and Beaumont Resources Ltd. completed a program of prospecting, geological mapping, trenching and rock sampling on the area immediately east of the occurrence as the P property.
In 1981 and 1982, Coppex Syndicate completed a program of geological mapping and geochemical (rock and soil) sampling on the area as the BE and MO claim groups.
In 2005, Twenty-Seven Capital Corp. completed a regionally extensive program of geochemical (rock, silt and soil) sampling and a 9002.0 line-kilometre airborne magnetic survey on the area as the Muskwa property.
