Minto/Carmacks Cu-Au, Yukon Geological Overview
2016/01/25 BCGold Corp. Announces Acquisition of New Yukon Gold Discovery (Wels Poperty), Corporate Restructuring and Private Placement Read Release
2013/10/03 Kaiyue International Inc. Commences Work Program at BCGold Corp.’s Toe Property in Yukon Read Release
2013/09/23 BCGold Corp. Commences Work Program at Minto–Carmacks Copper–Gold Property in Yukon Read Release
2012/08/10 BCGold Corp. Enters into Option Agreement With Kaiyue International Inc.
2012/06/21 BCGold Corp. Commences Exploration Programs on Six Properties in B.C. and Yukon Read Release
BCGold Corp. is the largest landholder in the Carmacks Copper Gold Belt. Its 16 Minto/Carmacks Copper-Gold Properties are strategically located proximal and adjacent to Capstone Mining Corp.’s ("Capstone") Minto Mine, a conventional flotation open pit copper mine that commenced commercial production on October 1, 2007, and Copper North Mining Corp.'s ("Copper North") Carmacks Copper Project, located 52 kilometres to the south. Copper North's Carmacks Copper Project is currently in the permitting stage and the company is planning for an open pit, heap leach operation. BCGold Corp.’s Carmacks Copper-Gold properties were staked over areas with similar geological, geochemical and geophysical characteristics known to reflect near-surface, high-grade structurally controlled copper-gold mineralization.
BCGold Corp.’s Minto/Carmacks Copper-Gold properties are situated in the Carmacks Copper-Gold Belt, centered some 220 kilometres northwest of Whitehorse, Yukon. This northwest-trending belt lies along the eastern margin of the Yukon-Tanana Composite Terrain, which is composed of several metamorphic assemblages and batholiths. Intermediate to felsic intrusive and meta-intrusive rocks of the early Mesozoic Granite Mountain Batholith underlie much of the area and are interpreted to be intrusive into the Yukon-Tanana Terrane (Gordey and Makepeace, 1999). The batholithic rocks are in fault and/or intrusive relation with an unnamed package of altered mafic volcanic rocks to the northeast, and are unconformably overlain by sedimentary rocks and volcanic flows of the Late Cretaceous Tantalus Formation and Late Cretaceous Carmacks Group, respectively. Regional structure is poorly understood because outcrop is very sparse (<1%) and the area is unglaciated and deeply weathered.
The Minto Deposit*
The high grade Minto copper-gold-silver mine is Canada’s newest mine, reaching commercial production on October 1, 2007. The deposit was discovered in 1973 and actively explored and evaluated in the early 1970s and 1990s but not developed until 2005-2008.The Minto deposit is hosted by Mesozoic Age plutonic rocks of the Granite Batholith (~197Ma), which is interpreted as intrusive into the Yukon-Tanana Terrain. The Granite Batholith is composed of primarily massive granodiorite with very discrete, localized zones of foliation. The Minto deposit itself lies in the near flat-lying hinge of a broad north trending synform defined by the warping of this foliation about an axis which passes through the deposit.
There are no apparent deposits analogous to the Minto deposit on a world-wide basis, except perhaps the nearby Carmacks copper deposit. Capstone Mining Corp. is currently working on the basis of Minto being a variant of the IOCG class of deposits. Whatever its origin, the Minto deposit is hosted in granodiorites and mineralization is characterized by a bornite-chalcopyrite-magnetite rich core grading outward to a chalcopyrite-rich but bornite-magnetite poor eastern periphery. Magnetite content ranges to 30+%, but averages 5-10%. Pyrite is either absent or present in very low concentrations and is confined mostly to the magnetite-poor eastern periphery. Mineralization is confined to the zones of foliation where copper sulphide mineralization is disseminated and bleb to stringer like, preferentially orientated along foliation planes. Copper can locally grade up to 20+% while gold grades are frequently in the 1-2 g/t range. Gold is found throughout the deposit but is most strongly associated with bornite, although rare coarse free gold has been reported with grades exceeding 500g/t Au.
Visible alteration is sharply confined to foliated rocks with secondary potassium feldspar and abundant secondary biotite, and local silicification. Structural control of mineralization is evident on a micro and macro scale, with mineralization confined to multiple, flat-lying deformation zones in sharp contact with barren, but geologically identical granodiorite. Internal foliation is often at an angle to the overall foliated zones, and small scale parasitic folds internal to the foliated zones are evident. There is large scale open folding of the foliated zones and later sub-vertical structures may be upgrading the mineralization.
Since acquiring control of the Minto deposit in 2005, Capstone Mining Corp. has been undertaking an aggressive exploration program that has resulted in the discovery of at least one new commercial deposit, as well as several other significant zones of mineralization that offer commercial potential.
* Abridged from Geological Association of Canada, Québec 2008, Abstract, vol. 33, p. 140.
Western Copper Corp. (the company from which Copper North was spun out in October 2011) defined 14 copper zones within the Carmacks Copper Project, which BCGold Corp.’s Carmacks Block of mineral claims surrounds. The Carmacks Copper Project is situated 52 km south of the Minto deposit. The deposit area is underlain by intrusive and meta-intrusive rocks of the Granite Mountain Intrusion. Compositions range from granodiorite to diorite. These rocks are equigranular to porphyritic, and massive to moderately foliated.
Technical reports describing the geology of these deposits and the region in detail can be viewed by going to the 'Reports' tab of the box on the right hand side of this page.
For additional details on the Minto and Carmacks deposits, please see the websites for Capstone Mining Corp. ( http://www.capstonemining.com/ ) and Copper North Mining Corp. ( http:/www.coppernorthmining.com/ ).
To date, BCGold Corp. has discovered seven significant “Carmacks–style” copper–gold mineralized zones on the ICE and WS properties, which lie just south of the Carmacks deposit.
At the ICE claims in 2007, situated seven kilometres southward of the Carmacks deposits, rock samples were collected from a series of granitic outcrops over a partially exposed strike length of 80 metres. The granitic rock displays discrete zones of weak to moderate foliation dipping 25-30° to the northeast, locally containing significant amounts of “Carmacks-style” copper oxide and gold mineralization with samples assaying up to 1.83% Cu, 0.25 g/t Au and 1.28% Cu, 0.41 g/t Au. The oxide copper mineralization occurs in the form of malachite with secondary biotite (potassic) alteration.Follow-up drilling at the ICE zone in 2007 intersected 2 discrete zones of copper-oxide mineralization. The first copper horizon was approximately 5 metres thick and grades up to 0.46% Cu. The horizon is described as foliated megacrystic biotite rich granodiorite with 5-10% malachite on fractures and along the foliation. A second copper-oxide horizon less than 2 metres thick and grading up to 0.26% Cu was intersected further down-hole and is characterized by 5% malachite on fractures and along foliation planes (for full details of the drilling see November 22, 2007 news release). Ice Zone copper-gold mineralization occurs along the eastern flank of a bulls-eye aeromagnetic high signature, measuring roughly 1,000 metres by 700 metres in size. Highly anomalous copper-in-soil samples, with values ranging from 281 to 935 parts per million (ppm) copper have been recorded 300 metres westward of the Ice Zone rock samples, along the northwest margin of this same magnetic anomaly.
In 2008, BCGold Corp. drilled five holes in 1,235 metres on the WS property along the Copper North property boundary, targeting five discrete induced polarization (IP) geophysical and/or copper Mobile Metal Ion (MMITM) geochemical trends defined by BCGold Corp. in 2008 . Drill hole WS08-09B intersected two near-surface copper sulphide horizons over 63.1 metres that averaged 0.17% Cu (containing 23.6 m averaging 0.34% Cu). This intercept is reflected by a weak copper MMITM anomaly coincident with a pronounced, 2 kilometre long linear IP geophysical anomaly. This IP anomaly is along strike and one kilometre from Copper North's Zone 14. Western Copper Corp. intersected 79.7 metres averaging 0.23% copper in Zone 14 during its 2007 drill program (Western Copper Corp. News Release – November 22, 2007). BCGold Corp.’s drill holes WS08-10, 11 and 12 did not intersect any significant copper mineralization.Copper mineralization in drill hole WS08-09B occurs in two discrete and relatively homogenous intervals of foliated horneblende schist within a white mega-crystic alkali feldspar granodiorite. Mineralization in the upper interval, which averages 0.13% copper over 20.0 metres between 46.0 – 66.0 metres, consists primarily of pyrite and chalcopyrite intermixed in foliated schist. Massive chalcopyrite occurs along the edges of carbonate stringers and malachite occurs along fractures.
Chalcopyrite mineralization occurs in a similar fashion in the lower mineralized interval between 85.5 and 109.1 metres, and averages 0.34% Cu over 23.6 metres. Chalcopyrite and fracture controlled malachite occur intermixed with pyrite in foliated hornblende schist. Massive chalcopyrite rims carbonate stringers and larger chalcopyrite grains display red oxidized rims. Propylitic (chlorite, epidote, carbonate, and sericite) alteration with secondary hematite and weak alkali feldspar alteration predominates.