The Sunro mine is located on the eastern side of the Jordan River, approximately 3.3 kilometres northeast of the community of Jordan River.
The Metchosin Volcanics form a belt 8 to 16 kilometres wide that extends west-northwest across the southern end of Vancouver Island. The volcanics consist principally of basalt and some diabase. Near the Sunro mine they include porphyritic and non- porphyritic, amygdaloidal varieties; beyond the mine area, well developed pillow lavas, flow breccias and fragmental types are found. They strike 120 to 130 degrees and dip 15 to 30 degrees northward, although in places they may be vertical or dip steeply southward. Fossils found in interbedded basaltic sandstone are Eocene (Geological Survey of Canada Memoir 96, page 290).
The mineralization of the Sunro mine appears to be genetically related to the emplacement and crystallization of the Eocene Sooke Gabbro within the Metchosin Volcanics, the orebodies occurring near contacts. The gabbro, possibly comagmatic and coeval with the volcanics, occurs as several stock-like masses of augite gabbro that trend north west across the southern tip of the island; however, these bodies in the Sunro vicinity are elongate, striking with the enclosing volcanics, and may be sills. Three north west -trending bands of gabbro occur on the Sunro property, ranging in width from 150 to 900 metres, separated by approximately 1 kilometre of basalt, and are known to extend along strike for approximately 6.5 kilometres. The centre band, from 600 to 900 metres wide, is the widest of the bands and the most important, hosting copper mineralization in shears in basalt along both contacts. The rock is a dark- greenish grey, coarse-grained hornblende gabbro with conspicuous plagioclase crystals. Some relicts of primary augite remain as cores surrounded by the secondary hornblende. Some white patches occur in the gabbro where plagioclase has been hydrothermally altered to scapolite. The basalt in the contact zone has a definite hornfels texture.
The oldest rocks in the area form the Jurassic to Cretaceous Leech River Complex and consist of a series of argillites and sandstone that have been metamorphosed into slaty and quartzose schists. The complex is in contact with the northern boundary of the Metchosin Volcanics along the west- striking Leech River fault. Marine sandstones and conglomerates of the Oligocene Sooke Formation overlie the volcanics and gabbro along the southern boundary of their exposure near the ocean. Many diabase dikes are exposed, cutting the gabbro in the Jordon River canyon. They range in width from just a few millimetres to approximately 3 metres, but widths of approximately 1 metre are typical.
The basalt surrounding the ore-bearing shear zones has been extensively replaced by hornblende, and in the shear zones this hornblendized basalt has been mineralized with chalcopyrite, pyrrhotite, pyrite and small amounts of molybdenite. Microscopic lathes of cubanite have been noted in some specimens of chalcopyrite, and minute blebs and wisps of pentlandite have been seen in pyrrhotite. Polished sections have also identified arsenopyrite and ilmenite. Much of the pyrite has a striking colloform texture. A small amount of native copper, as disseminated grains and as a leaf-like coating on short slips, has been seen in core from holes drilled beyond the mineralized zones. Scattered grains of magnetite are common, not only in the ore zones but also beyond them. The ore sulphides form a pattern of gash-like veinlets and irregular lenticular masses in the hornblende rock of the shear zones. Some chalcopyrite veinlets also contain quartz. In addition to its occurrence as veinlets and lenses, a small amount of chalcopyrite occurs as disseminated grains.
At least 18 mineralized zones have been identified over a distance of approximately 1.6 kilometres of the Jordan River canyon. The zones typically occur in basalt but at least three minor zones are located in areas mapped as gabbro. Three zones along the north east contact of the gabbro body, the River (A, B and C), Cave and Centre (New), have proved to be the most promising. Other zones include the Turnbull, Archibald, Bend, Winkler, Tiger, Yellow Cliff, Robertson, Caulfield, Hornet, Vulcan, Stewart, Hanna and Gordon.
The River (A, B and C) zones are located on the Sunloch 6 (L.797) crown grant and extend underground and below the Jordan River north to the Sunloch 5 (L.796) crown grant. The zones range in width from 30 centimetres to approximately 30 metres and are traceable along strike for approximately 335 metres, and to a depth of 340 metres. The zone is roughly parallel to the trend of contact, striking 150 degrees and appearing to dip from 70 to 80 degrees south west. In 1973, drilling on the River “C” zone yielded 2.07 per cent copper over 2.7 metres in hole U-703 and 1.06 per cent copper over 6.9 metres in hole U-704, while a hole (U-703) near the River “A” zone yielded 1.98 per cent copper over 15.6 metres (Property File - Jordan River Mines Ltd. [1974-01-01]: Annual Geological Report 1973 - Sunro). In 2000, a 0.25- metre grab sample (170502) from the River adit assayed 2.42 per cent copper, 8.4 grams per tonne silver and 0.57 gram per tonne gold (Property File - EMPR [2000-04-28]: Assays - Sunro). In 2004, a rock sample (S-04-AR-3) assayed greater than 1 per cent copper with 21.6 grams per tonne silver and 0.72 gram per tonne gold (Assessment Report 27472).
The Centre (New) zone, located approximately 90 metres south east from the River zone, strikes 110 degrees and dips vertically. It has been traced for a length of 200 metres and to a known depth of 97 metres. Where exposed underground, the zone is composed of a 36 metre width of widely spaced stringers of chalcopyrite. In 1973, a sample from the Centre tunnel portal yielded 3.4 per cent copper over 2.4 metres, while diamond drilling yielded up to 2.37 per cent copper over 2.4 metres (Property File - unknown [unknown]: Notes, Letters and Reports on Sunro Mine).
The Cave zone, located approximately 200 metres south west from the River zone, trends at 140 degrees and contains widely spaced stringers and lenses of chalcopyrite over a width of approximately 40 metres. The zone has a proven length of 180 metres (possibly as much as 460 metres) and a vertical extent of 150 metres. The Cave zone is also exposed on the west side of the Jordan River, approximately 30 metres downstream, and intersects the Turnbull zone. In 2004, a rock sample (S-04-AR-6) assayed greater than 1 per cent copper with 35.6 grams per tonne silver and 0.96 gram per tonne gold (Assessment Report 27472).
The Gordon zone, located approximately 100 metres southwest of the River adit, is hosted by massive basalt and strikes 105 degrees with a vertical dip. Mineralization consists of pyrite, chalcopyrite and bornite with hornblende and quartz stringers. In 2000, a 0.25- metre grab sample (170503) assayed 2.12 per cent copper, 3.1 grams per tonne silver and 1.29 grams per tonne gold (Property File - EMPR [2000-04-28]: Assays - Sunro).
The Hanna zone, located approximately 150 metres southwest of the Cave zone, occurs at the contact between the gabbro and basalt units. The zone strikes north 120 to 125 degrees east with a dip of 40 to 45 degrees north east. In 1973, a probable resource of 85,420 tonnes averaging 1.12 per cent copper was reported for the zone (Jordan River Mines Ltd. [1973-01-01]: Annual Geological Report 1972 - Sunro).
Weakly mineralized shear zones are also reported on the Ayah fraction, located approximately 1.2 southeast of the Forebay reservoir, and on the Olive fraction near Winkler Creek to the north west.
Production commenced in 1962 and proceeded intermittently until 1976, with most or all of the production apparently coming from the River (B and C) and Cave zones. During this time a total of 1 ,329 ,034 tonnes were mined and milled yielding 13,754,271 kilograms of copper, 2,262.65 kilograms of silver and 203.101 kilograms of gold.
Measured (proven) reserves are 1,030,465 tonnes grading 1.47 per cent copper; and indicated (probable) reserves are 423,782 tonnes grading 1.33 per cent copper (Northern Miner - December 27, 1973).
The area has been explored since its discovery in 1915 by G. Winkler. In 1917, Sunloch Mining Co. completed an unknown amount of trenching, diamond drilling and underground development. In 1919 and 1920, Consolidated Mining & Smelting Company continued programs of trenching, diamond drilling, totalling 1041 metres, in an unknown number of holes and 1132.8 metres of underground development on the River, Centre and Cave adits. Also, during this time, the Winkler and Hornet adits were driven. In 1949, Hedley Mascot Gold Mines Ltd. optioned the property and completed 2806.2 metres of diamond drilling. The following year, another 1224.6 metres of diamond drilling were completed. In 1955, a program of prospecting, geological mapping, trenching, electromagnetic and magnetic surveys, soil sampling and 600 metres of diamond drilling were completed. In 1956, the property was consolidated under Sunro Mines Limited. In 1957 and 1958, an adit was driven from an elevation of approximately 30 metres and for a total of 2341.5 metres along with a 120- metre drift.
During 1960 through 1962, Cowichan Copper Co. Ltd. re-opened the underground workings and completed 529.5 metres of drifts, raises and cross cuts along with milling, crushing and worker chambers. In 1963, the No.1 shaft was sunk for 145.8 metres along with 116 drill holes, totalling 4,186.2 metres, and 1829.1 metres of drifting and raising. In late 1963, a mine collapse in the “B” stope halted production. In 1964, a program to re-habilitate the underground workings was initiated. During 1965 through 1967, 3619.8 metres of underground development and 3535.8 metres of underground diamond drilling were completed. In 1968, Cerna Copper Mines Limited completed 1018.5 metres of underground development and 113.1 metres of diamond drilling before production ceased late in the year. In 1970 and 1971, mine rehabilitation programs including 1284.9 metres of underground development and 2298.9 metres of diamond drilling were completed. In 1972 and 1973, Jordan River Mines Limited continued production and underground development along with 7695.6 metres of diamond drilling. In 1977, after two further cave-ins occurred, the eight surface entries were barricaded.
A property visit in May 2000 and sampling by J. Houle showed elevated values in nickel and cobalt. In 2004, A. Kikauka completed a program of soil and rock chip sampling.