Allen Bay Stratigraphy
The BPF is the dominant host of good copper mineralization throughout the property. It is within this unit that the best replacement textures are seen. The fossiliferous and bioturbated nature of the BBF provides a receptive host for mineralization fluids. Adjacent to strongly mineralized BPF, the ADMW unit usually contains moderate crackle breccia hosted and stringer/vein style mineralization throughout, often extending up to the contact with the Cape Storm Formation. Only in the 3500 Zone is mineralization seen to penetrate down into the VSM, likely due to the structurally complex nature of this area. The best mineralization in the 3500N zone is BPF as breccia cement and towards the top of the VSM as stringers.
Through most of the mineralization was hosted in the Allen Bay, hole ST99-35 intersected 0.85% Cu / 1.8 metres in the Douro Formation fossiliferous limestone. This indicates potential may exist in the Douro Formation, a unit not considered as a good target prior to the drilling.
ADMW unit (Alternating Dolmicrite and Dolwackestone)
The ADMW unit consists of a 35-50 metre succession of fine-grained dolomitic mudstone (dolmicrite) alternating with light to medium grey silty dolomite intervals containing disseminated fossil fragments and debris (dolwackestone). The base of the ADMW is marked by the first appearance of the BPF unit.
BPF unit (Brown Dolpackstone and Dolfloatstone)
The BPF unit is distinguished by its medium to dark brown and different lithology. Dolpackstone is a term defining a fossiliferous unit where the concentration of fossil fragments is very high such that individual fossil fragments are packed together cemented by carbonate. The unit averages approximately 35 metres in thickness. Chert nodules are common in this unit and seem to be restricted to two horizons, one found about a third of the way from the top, and the other located close to the base. The bottom of this unit is marked by the appearance of light grey to buff stromatoporoid facies.
VSM Unit (Varied Stromatoporoid)
The VSM unit is composed of various dolfloatstone and dolrudstone beds (term that defines coarse fossil fragments that produce a cobble texture), interbedded stromatoporiod boundstone, framestone, and some thinly bedded dolmicrite beds. The unit is greater than 150 metres thick.
Close to the top of the VSM unit is a distinctive reef horizon, the SBFM unit (Stromatoporoid Boundstone/Framestone Marker). The distinctive marker is characterized by digitate stromatporoids in growth position. Dolarenite and dolmicrite sediments fill the interdigitate voids. The SBFM marker averages six metres thick, though in places is found brecciated, and significantly thinner.
Five metres below the SBFM is the RCM unit (Rudstone Chip Marker). The RCM is less than one metre thick, consisting of a shelly hash of elongate fossil fragments. In the western portion of the property, a third marker unit, the OP (Oolite Marker), occurs about 40 metres from the top of the VSM. This distinctive marker is composed of one or two reverse-graded oolite to oncolitic packstone beds. In the 3500 Zone the SBFM and RCM are located roughly 35 metres below the Oolite Marker, demonstrating substantial thickening of the VSM to the west.
The SBFM and RCM markers occur within the footwall to most of the mineralization and represent a useful level past which drilling was terminated. The SBFM and RCM were found across the drilled area, but not in every hole. This was due to holes collared in the footwall, 2) the late recognition of the markers in the program 3) a lack of significant mineralization above that level in many holes and, 4) holes lost at a shallow depth.
This stratigraphy was identified best in the 4100 Zone where are a number of closely spaced holes intersected the marker horizons. The OP is dominant in the 3500 Zone. However both the SBFM and RCM markers were located on the eastern edge of the 3500 Zone (Hole ST99-38) allowing the 3500 zone to be placed in the regional context. The stratigraphic subdivision and the two markers (SBFM and RCM) provide important information for regional evaluation of the Allen Bay Formation.
Stratigraphic Column - Storm Copper
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