The Chopper 7,9 copper occurrence is situated at the headwaters of the Gataga River, 13.5 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 7,9 occurrence is situated around the contact between the Aida Formation and the overlying Gataga Formation of the Muskwa Assemblage, although the mineralization is structurally, not stratigraphically, controlled. The Aida Formation comprises slaty, dolomitic mudstone and siltstone, argillaceous limestone, and dolostone (Assessment Reports 2640, 10960; Geological Survey of Canada Memoir 373, Paper 67-68). The Gataga Formation consists of slaty, carbonaceous shale, mudstone, siltstone and sandstone. 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 from a few metres to tens of metres in thickness. 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. 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 1 in the Chopper 9 claim at the top of the Aida Formation, but it encompasses Showing Number 2, 250 metres to the southwest in the Chopper 7 claim, which is at the base of the Gataga Formation (Assessment Report 2640). The veins in Showing Number 1 strike approximately 020 degrees, dip steeply west or vertically, and extend discontinuously for approximately 300 metres, mostly along the margin of a diabase dike. The veins range in thickness from 0.6 to 2.75 metres. Mineralization is erratic, forming streaky lenses less than 1 centimetre to 25 centimetres wide. Chip sample C-3 assayed 7.36 per cent copper over 60 centimetres, and chip sample C-5 assayed 0.52 per cent copper over 2.75 metres (Assessment Report 2640, Geological Map).
Showing Number 2 consists of a single quartz carbonate vein with a more typical north-northwest strike, and a dip of 40 degrees west. It is exposed for approximately 200 metres and ranges in width from 30 to 90 centimetres. Mineralization is very erratic. Chip sample C-7 assayed 1.47 per cent copper over 60 centimetres (Assessment Report 2640, Geological Map).
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 and Acroll Oil and Gas Ltd. completed a program of geological mapping on the area immediately north of the occurrence as the Andrew claims.
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.
