Toronto-based gold producer Orvana Minerals (ORV-T) has increased the historical estimate at its copper deposit in Michigan by 12%.
A National Instrument 43-101 resource for Orvana’s Copperwood deposit demonstrates measured and indicated resources of 19.5 million tonnes grading 1.86% copper for contained copper of 798 million lbs., and an additional 3.3 million tonnes in the inferred category grading 1.49% copper for 107 million lbs. copper.
The new numbers will be included into a preliminary economic assessment due out in June. They will also be used to assess earlier trade-off studies and refine the company’s conceptual mine plan. Over the last year Orvana has undertaken various trade-off studies to evaluate mine and tailings impoundment designs, assess water sources, waste management and transportation alternatives.
The resource estimate is based on 119 drill holes totaling 18,885 metres of which Orvana drilled 85 holes (or 13,425 metres). The remaining drill holes are historical.
Copperwood is about 30 km southwest of the inactive White Pine mine, where between 1953 and 1996 more than 1.7 million tonnes of copper and 4.5 million oz. silver were produced.
Copperwood’s stratiform copper mineralization is hosted in shales and siltstones of the basal Nonesuch Formation and is stratigraphically equivalent to the copper-bearing zone at the White Pine mine. The mineralization occurs as very fine-grained chalcocite.
The mineralized area is open to the southwest but truncated to the south by subcrop, to the north and east by a stratigraphic pinch out, and to the west by the lakeshore.
In addition to copper, the Copperwood deposit contains silver ranging from 5 to 7 grams per tonne in the Domino and Upper Layer.
Copperwood is situated along the southern flank of the west-northwest- plunging Western Syncline and has option agreements on three other mineralized areas within it.
Along with Copperwood, Orvana owns and operates the Don Mario copper-gold mine in Bolivia and is developing the advanced-stage El Valle-Boinas/Carles gold-copper project in northern Spain.
The company’s share price was $1.05 at presstime, trading within a 52-week range of 60¢-$1.22.
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