The Junction 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 12 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.
The Junction deposit lies about 2 kilometres to the west-northwest of the main Galore Creek-Central Zone deposit.
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 Junction deposit is a tabular northeast-striking, northwest-dipping body. It can be traced from surface exposures and drill holes 700 metres along strike and 200 metres down dip. The North Junction deposit, 350 metres 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 dikes that parallel the deposit. On the south end of the deposit, the Junction Porphyry marks the hanging wall of the mineralization. The footwall is limited by either the Junction Porphyry, syenite porphyry dikes, or assay limits.
The mineralization, consisting of disseminated chalcopyrite and bornite, is hosted in both the Junction porphyry and the Late Junction porphyry and orthoclase syenite mega-porphyry. K-silicate alteration consisting of pervasive hydrothermal biotite and K-feldspar flooding is associated with the mineralization. A large mass of late-mineral mega-porphyry truncates the zone on the west. A brittle–ductile fault marks the southern limit of North Junction mineralization."
Both the North Junction and the Junction have similar geological characteristics to the Central Zone.
In 1966, Barr (CIM Bulletin July 1966) described the Junction deposit as follows: "The deposit trends slighty east of north and dips steeply to the north- west, parallel in strike attitude to the contact of a nearby mass of epidotized syenite porphyry which lies to the southeast. The deposit is controlled by a zone of fracturing in which both potash feldspar and hydrothermal biotite are the principal alteration products. The mineralization includes pyrite, chalcopyrite and minor bornite which occur as disseminations, fracture fillings and as stringer-like replacements. Specularite, which occurs as minute veinlets, is prominent on the southeast side of the southern part of the deposit. The upper part of the southern extension of the deposit contains many minerals typical of the oxide zone, including native copper, cuprite, covellite, chalcocite and malachite."
By September 2004, NovaGold had completed five drill holes in the Junction zone located 1.2 kilometres west of the main Central deposit. Historically, 35 drill holes were completed in the area, defining a mineralized zone measuring 500 metres by one kilometre. Initial results from NovaGold's first drill hole, GC04-465, intersected three composite intervals totalling 133.7 metres of 2.2 per cent copper equivalent or 3.6 grams per tonne gold equivalent and grading 1.6 per cent copper, 0.9 gram per tonne gold and 12.9 grams per tonne silver. Included in this composite interval are 56.4 metres grading 2.2 per cent copper, 1.7 grams per tonne gold and 20 grams per tonne silver (Press Release, NovaGold Resources Inc., Sept. 27, 2004).
An NI-43-101 compliant resource estimate for the Junction at a 0.35 per cent copper equivalent cut-off is given at 30,000,000 tonnes of Measured and Indicated ore grading 0.59 per cent copper, 0.41 gram per tonne gold and 4.78 grams per tonne silver and; 71,600,000 tonnes of ore in the Inferred category grading 0.53 per cent copper, 0.29 gram per tonne gold and 3.33 grams per tonne silver (Updated Preliminary Economic Assessment, NovaGold Resource Inc., October, 2005).
In 2008, Galore Creek Mining Corporation (GCMC) completed nine diamond drill holes totalling 2,049.58 metres. The main objectives of the drill program were to obtain ABA (Acid Base Accounting) data in the Central, Southwest, North Junction and Junction pits, to confirm legacy grades in the Junction pit, and to collect metallurgical data in the Central pit.
AMEC reports five zones as being modelled toward its 2011 Mineral Resource Estimate: the Central Zone (including the Bountiful deposit), Southwest Zone, Junction/North Junction Zone, Southwest Zone, and West Fork Zone. The Junction and North Junction zone have historically been separate and are treated as such for MINFILE.
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. Details of work history on specific zones (including the Junction zone) are not readily available or easily broken out from the overall Galore property body of work.
