The Ann 188 occurrence is situated on the Ann 18 claim, 7 kilometres south of Yedhe Creek, 10 kilometres east of Toad River, in the Muskwa Ranges in the Northern Rocky Mountains approximately 166 kilometres west of Fort Nelson (Assessment Report 3420, Map 14).
The occurrence is in a region known as the Muskwa Anticlinorium, a major north-northwest trending structure characterized by moderate folding and thrust faulting. The structure consists of Middle Proterozoic (Helikian) rocks of the Muskwa Assemblage, as well as Paleozoic rocks (Geological Survey of Canada Map 1343A; Geological Society of America, Geology of North America, Volume G-2, pages 111, 639). All belong to Ancestral North America (Geological Survey of Canada Map 1713A). Northeast to northwest trending diabase dikes of Proterozoic age are common in the region.
The showing area is underlain mainly by the Aida Formation of the Muskwa Assemblage (Geology, Exploration and Mining in British Columbia 1971; Geological Survey of Canada Memoir 373). In this area, this unit comprises calcareous and dolomitic mudstone and slate, silty mudstone, dolostone, limestone and minor quartzite (Assessment Report 3420; Property File - Adamson, R.S., 1971). Bedding strikes northwest and dips moderately southwest. Locally the rocks are folded, sheared and faulted, and are intruded by several northeast-striking diabase dikes.
A prominent shear zone passes through the area, striking about 045 degrees. It is approximately 30 metres wide and has been traced for 1.1 kilometres horizontally, and 425 metres vertically. Coincident with the shear zone is a large diabase dike, forming a resistant spur. It dips steeply and is betweeen 2 and 12 metres thick. Its contacts are sheared and altered, as is the adjacent slaty mudstone wall rock. The dyke and the shear zone are important as they host a discontinuous series of mineralized quartz-carbonate veins, occurring at or close to the dike's contacts in the shear zone. The constituent veins have the same general orientation, but may vary in attitude on the local scale. The veins range in thickness from a few centimetres to 2.75 metres; most are under 1 metre thick. They may have originally been a single vein, known as the Neil vein, which has been disrupted by shearing into smaller lenses. The age relationship between the dike's intrusion and the veining is uncertain; at least some shearing post-dates both.
The veins are composed of quartz and ankerite, and may have inclusions of wallrock. Chalcopyrite is sporadic and occurs in aggregates and disseminations in variable amounts, along with very minor bornite and pyrite. Secondary malachite and azurite are common. Very locally, there are small blebs and stringers of galena.
This occurrence is centred on the vein in Trench 4, towards the western end of its exposure, immediately west of the Bob group of claims (Assessment Report 3420, Map 14). A related occurrence, the Bob 3-4 prospect (094K 040), is towards the eastern end of the vein. Here, the vein is on the southeast side of the dike. The best chip sample from Trench 4 assayed 2.79 per cent copper over 0.9 metre (Assessment Report 3420, Map 6).
Exploration in the area dates back to the early 1960s when copper-bearing quartz-carbonate vein showings were discovered in the Muskwa Anticlinorium. Two of them, Neil Vein (094K 040) and Ann 18 (094K 057, this description and also referred to as the Neil Vein) lie within the Neil property of A.R. Raven (ca. 2016). These two occurrences are at the northeast and southwest ends, respectively, of what is believed to the same mineralized vein structure. The veins are referred to by different names. The Neil Vein (094K 040) is also referred to as the Bob 3-4, Ram Creek and Okey Vein, and the Ann 18 Vein (094K 057) has also been referred to as the Neil Vein. Refer to 094K 040 for a detailed and related work history.
In 1972, seven holes were diamond drilled on the Ann 17 and 18 claims, totalling 681 metres (Geology, Exploration and Mining in British Columbia 1972).
There was renewed interest in the property in 1992 (George Cross News Letter, Number 87, May 5).