Summary:
The Galore Creek property is interpreted to be an example of an alkalic porphyry copper–gold–silver system.
The Project is situated within the Stikine Terrane, an exotic terrane accreted to the ancestral North American craton. A sequence of Permian, Mississippian and Devonian age calc-alkaline and bimodal flows and volcaniclastic rocks, interbedded carbonate and minor shale and chert, termed the Stikine assemblage, form the basement of the terrane. Unconformably overlying the Stikine assemblage is a succession of Lower to Middle Triassic sedimentary and upper Triassic volcanic rocks.
The Galore Creek Syenite Complex, of Tertiary age, is centered in the west fork of Galore Creek and is 5 km in length and 2 km in width. The deposits are hosted by potassium-enriched volcanic rocks and pipe-like breccias adjacent to syenite stocks and dykes. They are manto-shaped, and trend north to northeast, following either, or both, syenite contacts and structural breaks. To date, 14 deposits and prospects have been identified, five of which, the Central Zone, Southwest Zone, Junction Zone West Fork Zone and Middle Creek Zone are of economic interest.
Disseminated pyrite is the most abundant sulphide mineral. Chalcopyrite and bornite in the ratio 10:1 are the main copper minerals. Sphalerite and galena are associated with garnet-rich areas and trace amounts of molybdenite, native silver, native gold and tetrahedrite have been noted (Allen, 1966). Magnetite occurs in veinlets with or without chalcopyrite, and often cements breccias. Secondary minerals identified include chalcocite, cuprite, native copper and tenorite.
Bornite and generally higher-grade gold are developed in the intense potassic alteration zone, and are associated with magnetite and sparse pyrite. Within the propylitic zone, zones of moderate potassic alteration have developed, and have associated chalcopyrite and pyrite mineralization. External to these potassic zones, but still within the propylitic zone, replacement lodes of gold, silver and base metals have formed.
Where surface exposures have been mapped in the Central deposit, malachite, azurite, hematite, and limonite, occurring both as locally pervasive disseminations and as widespread fracture-controlled infills, have been noted. Rare chalcocite and native copper were also noted. Typically, chalcopyrite and bornite are also found with the copper oxides. Drill core logs from Central have identified an oxide zone with average depths of 20 m below the overburden surface; however, weak fracture-controlled oxidation has been logged to depths of = 200 m. The oxide zone mimics the topography, weakens down-hole, and rarely reaches the broken–stick rock surface.
Oxidation is variable outside of the Central Zone. The Junction and West Fork deposits show trace to minimal oxidation. The Southwest Zone shows minimal oxidation and the Middle Creek deposit shows significant oxidation.
Central Zone
The Central Zone consists of the North Gold Lens, the Central Replacement Zone, and the South Gold Lens, which are differentiated based on gross differences in mineralogy.
The long axis of the Central Zone deposit has an orientation of 015° and dips steeply to the west. It is 1,700 m long, 200 to 500 m wide and has been traced to a depth of 450 m and remains open at depth. Mineralization crops out in the southern part of the zone, but elsewhere is covered by up to 75 m of glacially-derived material (Workman, 2006a).
The deposit plunges gently to the north and at its maximum thickness is 335 m. It comprises several parallel, en-echelon copper zones centred on a steeply-dipping breccia pipe. Mineral zoning consists of an intense potassic core zone, which hosts the mineralization, and a spotty propylitic alteration zone which occurs mainly along the eastern edge of the deposit.
Southwest Zone
The Southwest Zone is located about 600 m southwest of the south end of the Central Zone and contains some of the highest grade near-surface gold mineralization. Drilling has outlined an elongate pod-shaped body that trends roughly east–west and dips approximately 60° to the south. The zone is up to 400 m long and may be as wide as 140 m. It is still open at depth, and from 2005 drilling, may also be open along strike.
Junction and Junction North Zones
The Junction and North Junction Zones lie about 2 km northwest of the Central Zone and are about 460 m higher in elevation than Central. Both deposits have similar geological characteristics to the Central Zone.
The Junction deposit is a tabular northeast-striking, northwest-dipping body. It can be traced from surface exposures and drill holes 700 m along strike and 200 m down dip. The North Junction deposit, 350 m to the east, is podiform with the long axis plunging to the northwest.
Copper mineralization is well exposed on the slopes of Junction Creek, where the stream cuts through the Junction deposit. Mineralization is partially controlled or bound by Junction Porphyry and syenite dykes that parallel the deposit. On the south end of the deposit, the Junction Porphyry marks the hanging wall of the mineralization.
West Fork Zone
The West Fork Zone (also known as the West Fork Glacier Zone) lies in the valley floor less than 1 km south of the Central Zone and less than 50 m higher in elevation than Central. West Fork contains two adjacent but distinctly different styles of mineralization: disseminated sulphide replacements similar to portions of the Central Zone, and massive veining (Opulent Vein). Higher grade disseminated zones appear to be controlled by structures, though distinct veining is absent.
There are four distinct zones of mineralization, the Opulent Vein, the Upper Opulent Zone, the Lower Opulent Zone, and the Lower West Fork Zone. The first three mineralized zones are hosted in a breccia unit. The Opulent Vein is north–south trending and steeply west-dipping. The high-grade mineralization is defined by a massive magnetite–bornite–chalcopyrite assemblage which is hosted in a near-surface magnetite breccia. The Upper and Lower Opulent Zones parallel the Opulent Vein and are characterized by less intense bornite and chalcopyrite mineralization. The known extent of the Opulent vein is limited within a breccia mass and strikes approximately 355° with a steep westerly dip. The extent of the zone is 150 m in length and 100 m in depth. In general, mineralization shows a progression from bornite laterally to chalcopyrite with increasing pyrite peripheral in the system. Isolated intervals of anomalous gold occasionally >1 g/t Au have been encountered.
Middle Creek
Mineralization is characterized by finely-disseminated bornite, chalcopyrite and magnetite associated with pervasive fine-grained biotite and garnet alteration, hosted in a breccia or volcaniclastic unit. Middle Creek is the most oxidized zone discovered to date on the Galore Creek property.