The North Rim zone of the Galore Creek deposit is located at the headwaters of Galore Creek, a northerly flowing tributary of the Scud River, some 85 kilometres south-southwest of Telegraph Creek.
At least twelve alkalic porphyry copper-gold deposits are known to occur within the Galore Creek syenite complex. This complex comprises a series of Late Triassic to Early Jurassic orthoclase-porphyry syenitic bodies which have intruded coeval Upper Triassic Stuhini Group volcanic rocks and related sediments. Faults which offset and segment the intrusive rocks and a sub-horizontal fracture cleavage are the two main structural elements in the syenite complex. The complex is roughly 5 by 2.5 kilometres in area.
The deposits are hosted primarily by highly altered potassium-enriched volcanic rocks and pipe-like breccias adjacent to syenite dikes and stocks. Typically, the deposits are manto-shaped and have a north to northeast trend related to the syenite contacts and zones of structural weakness.
The syenite complex is made up of four intrusive phases that are most closely associated with the copper deposits. Six other phases are recognized but are peripheral to the Central zone deposit. The copper-bearing rocks near the syenite intrusion are extensively metasomatized, recrystallized and locally brecciated. These may include pyroclastic and intrusive breccia, trachyte, phonolite, lithic tuff, crystal tuff, pyroxene basalt, pyroxene andesite and minor sediments. These rocks have been converted to skarns and fenitic porphyroids so that original rock types are unclear. The term "hornfels" was frequently applied to these meta-volcanic rocks in the early stages of exploration.
Alteration and mineralization are contemporaneous and spatially overlap. The hydrothermal system was extensive and the resultant alteration led to the formation of large gossans. Potassic alteration consisting of potassium feldspar, titanium biotite and magnetite have converted the syenites and volcanic rocks to pink, white and orange rocks composed mostly of orthoclase. Alteration of pyroxene, hornblende and biotite to assemblages of chlorite and calcite plus/minus albite and epidote characterizes the propylitic zone, best developed in the syenitic rocks. Calc-silicate alteration consisting of abundant garnet, diopside, epidote, albite and anhydrite is an unusual feature of the complex. Garnet replaces up to 50 per cent of the metavolcanic rocks and infills breccias near the northern end of the Central zone breccia pipe but is generally absent from the other deposits. However unusual this metasomatic overprint is, the distribution of sulphides, precious metal and magnetite is considered consistent with the expected zoning pattern for alkalic porphyry deposits.
In 2011, the Junction zone was described in a technical report (43-101) by AMEC Americas Limited on behalf of NovaGold (Galore Creek Project by AMEC, July 17, 2011) as follows:
"The North Rim Zone lies in the northeast corner of the North Junction grid. It is an early-stage exploration target, defined by the presence of widespread scattered malachite in poorly-exposed outcrops, a large, coincident copper and gold soil anomaly, and a large, strong, chargeability anomaly that is broadly coincident with the soil anomaly. One large and two smaller breccia bodies were mapped in the area. Two clast types are present: late megaporphyry and equigranular syenite. Chalcopyrite accompanied by biotite and sometimes bornite are locally present either as veins or more frequently as an accessory in the breccia matrix.
Mineralization at an old cross-shaped trench, within the North Rim Zone, consists of disseminations and veins of chalcopyrite and bornite. The mineralized veins and fractures are locally 1 to 2 centimetres thick and occur with veins consisting of dark green diopside, biotite, and magnetite.
Chalcopyrite accompanied by biotite and sometimes bornite are locally present either as veins or more frequently as an accessory in the breccia matrix, in two of the mapped breccia bodies in the prospect area.
Work History
Trenching in 1989 crossed the strike of mineralization on the North Rim zone. Sampling outlined a 10.4-metre section which averaged 5.59 grams per tonne gold (Assessment Report 19397, page 26). This included 7 metres at 9.26 grams per tonne gold and 2.37 per cent copper. Six diamond drill holes totalling 545.7 metres were drilled on the zone in 1990. A 27-metre drill section averaged 0.27 gram per tonne gold and 0.3 per cent copper (Assessment Report 20558, page 29).
AMEC reports five zones as being modelled toward its 2011 Mineral Resource Estimate for the Galore Creek deposit: the Central zone (including the Bountiful deposit), Southwest Zone, Junction/North Junction Zone, Southwest Zone, and West Fork Zone. Refer to the Central Zone deposit (104G 090) for further details of the Galore Creek deposits. Further details of a common work history and 2011 reserves and resources are given.
