The Mag occurrence is located on the west side of the Coldwater River, approximately four kilometres north of the Coquihalla Lakes. Early exploration in the area focused on base and precious metal mineralization at the Keystone mine (092HNW024), located approximately two kilometres north of the Mag occurrence.
The geology of the upper Coldwater River area is characterized by Late Triassic Nicola Group metavolcanic and metasedimentary rocks resulting from the emplacement of granitic rocks, assigned to the Late Jurassic and Early Cretaceous Eagle Plutonic Complex, to the west. Along the Coldwater River, the Nicola Group comprises amphibolite, foliated diorite, mylonite and chlorite schist with minor marble in contact with gneissic granodiorite. A quartz diorite stock of Early Tertiary age has intruded the plutonic rocks west of this contact.
The Mag occurrence is situated near the south end of the quartz diorite (Keystone) stock. The southern half of the stock is brecciated, as is the Eagle Plutonic Complex granodiorite adjacent to it. The brecciation has been attributed to the emplacement of relatively small stocks and dykes of porphyritic rhyolite. This event was apparently accompanied by pervasive alteration (sericitic to silicification) and the introduction of metallic mineralization. Sericite, quartz and pyrite are the most common alteration minerals within the brecciated zones.
In the area of the occurrence, granodiorite, diorite and a pebble breccia comprising fragments of both units are in contact. The breccia has been sericitized and hosts disseminated pyrite, chalcopyrite and sphalerite, making up a combined total of from one to three per cent of the rock. A significant percentage of the fragments also host quartz-pyrite veining. Sericite is widely distributed throughout the breccia and galena, hematite and molybdenite mineralization occurs locally. The showing is weathered and black manganese oxides have been noted in some fractures.
On the west, or footwall side of the showing, there is a shear approximately 1.52 metres wide which strikes 130 degrees and dips 85 degrees to the northeast. This shear is cut nearly perpendicularly by a narrow vein of comb-quartz hosting manganese oxides. A similar vein, 7.6 centimetres wide, also cuts the breccia in another location. Both veins are apparently barren of sulphide mineralization.
In 1968, a sample from the trenched area is reported to have yielded 2223 grams per tonne silver (Property File - 650178).
In 1969, drillhole NC-5-69 yielded 9.5 grams per tonne silver over 54 metres of kaolinized breccia with disseminated hematite and ankerite veins (Assessment Report 7135).
In 1978, a rock sample (K11-6) from a felsic dike with pyrite and sericite assayed 44.0 grams per tonne silver (Assessment Report 7135).
Work History
The area has been explored in conjunction with the nearby Keystone (MINFILE 092HNW024) occurrence and a complete exploration history of the area can be found there.
In 1965 and 1966, Dorian Mines is reported to have completed approximately 1500 metres of trenching and 32 diamond drill holes, totalling 2018 metres, on the area south of Dry (Mine) Creek (MINFILE 092HNW023 and 092HNW022).
