Chalcopyrite in calcite skarn Copper ore

The Oro Denoro Mine is 10.2 kilometres northeast of Greenwood, at elevation 1066 metres on the divide between Eholt and Fisherman creeks. The property adjoins the Emma Mine (082ESE062) to the north. Access to these properties is about 0.6 kilometre southwest from Highway 3 by level gravel road along an old railway bed.

Production from Oro Denoro, in the period 1903 to 1917, totals 123,782 tonnes containing 116.5 kilograms of gold, 953.4 kilograms of silver, and 1690.6 tonnes of copper; this does not include several thousand tonnes of ore shipped to the Phoenix mill (082ESE020) in 1978.

The Oro Denoro mine is centrally located within a 2.4 kilometre long, north-south alignment of skarn deposits which includes the Emma and Jumbo (082ESE062) on the north and the Cyclops and Lancashire Lass (082ESE122) on the south. Mine development began at Oro Denoro in 1896 and by 1900 the underground workings consisted of a shaft 70 metres deep, and 240 metres of crosscuts and drifts. By 1908 an additional 40 metres of sinking and 20 metres of crosscutting was completed. The present mine workings cover an area of about four hectares in the central part of the claim.

In the early period of mining at the Oro Denoro mine, 1903 to 1910, ore was drawn from a number of large stopes on two underground levels and five open pits. The two southermost pits or quarries, Nos. 1 and 2, were the principal source of copper ore. These are interconnected and have a general east-west elongation. The trend of the excavations appears to follow the course of a number of large steeply dipping calcite lenses in the skarn by the granodiorite contact which is near the north wall. Quarry No. 3, centred about 60 metres north of Nos. 1 and 2, is the second largest pit. Here the mineralization was concentrated in a tongue of skarn projecting deep into the granodiorite mass. Quarries Nos. 4 and 5, centred about 45 metres northwest of No. 3, are relatively small. The magnetite rich ore was situated between a small remnant of limestone in the skarn and the granodiorite. Control of the mineralization appears to be east-west cross fractures trending approximately perpendicular to bedding in the limestone host rocks.

The most recent excavation, which is located immediately west and south of the old quarries, is an open pit, 150 metres long and 45 metres wide, developed mainly in garnetite skarn at the summit of Oro Denoro's 'Mine hill'. The target of these workings was a mineralized zone near the south end of the pit. The mine area is traversed by a number of ore controlling faults. The most significant is a pronounced shear that strikes 120 degrees from the north end of the main pit and through No. 1 quarry. Important movement on this zone has resulted in the emplacement of exotic formations in the skarn such as a wedge of carbonaceous schist in the main pit and epidotized volcanic breccia along the south wall of No. 1 quarry. Of less importance are two minor faults dipping 80 degrees east and 75 degrees southeast causing local displacements in the skarn-granodiorite contact.

Ore reserves at Oro Denoro comprise, in part, the sills and pillars in the old underground workings below the Granby pit. This mineralization is exposed in the lower adit level. More than several hundred thousand tonnes of ore grading in excess of 0.5 per cent copper may still remain in the mine according to old reports. Indicated resources were estimated at 1,058,700 tonnes of 0.95 per cent copper, 0.7 gram per tonne gold and 10.3 grams per tonne silver (Campbell, 1968 and Western Miner, October 1968). In 1967, W.J. Weymark estimated the following: reasonably assured, indicated and possible ore reserves at 42,460,000 tonnes grading 0.92 per cent copper, 0.82 grams per tonne gold, and 10.97 grams per tonne silver. This breaks down to 3,524,400 tonnes of reasonably assured ore grading 1.32 per cent copper, 0.82 grams per tonne gold, and 10.97 grams per tonne silver; 18,388,600 tonnes of indicated ore grading 0.80 per cent copper, 0.82 gram per tonne gold, and 10.97 grams per tonne silver; 6,331,200 tonnes of possible ore grading 0.75 per cent copper, 0.79 gram per tonne gold, and 10.97 grams per tonne silver; and 14,216,500 tonnes of possible ore, below the diorite sill, grading 1.07 per cent copper, and minor gold and silver. (Western Miner, February 1967, page 49.)

Exploration activity on the property and adjacent areas from 1950 to 1989 is summarized in Assessment Report 21329. See also History of Exploration and Development on National Mineral Inventory card 082E2 Cu4.

The area is underlain by limestone, sharpstone conglomerate, tuffs and breccias of the Triassic Brooklyn Group. These rocks are cut by granodiorite of the Jurassic-Cretaceous Wallace Creek Pluton and alkaline syenite of the Eocene Coryell Intrusions.

A skarn sample assayed 2.2 per cent copper, 6.0 grams per tonne, silver, and 0.15 grams per tonne gold (EMPR Paper 1989-3, Appendix 7). Another sample assayed 0.03 per cent cobalt (EMPR Bulletin 101, Appendix 4B).

Echo Bay Mines Ltd. drilled 5 holes totalling 250 metres in 1997.