Introduction
Eaglehead is an advanced exploration stage polymetallic porphyry copper project covering 15,713 ha (157.1 km2) located 50 kilometers (km) east of Dease Lake in the Liard Mining District, British Columbia, within Tahltan territory. The mineralized area covers an area measuring 8km by 3km and contains four open-ended porphyry copper deposits, two areas of widespread mineralization and 173 additional copper showings. The mineralized area is referred to as the “mineralized corridor”.
Property Description
In April 2021, Copper Fox, through its 100% owned subsidiary, Northern Fox Copper Inc., purchased a 100% working interest in the Eaglehead project for CA$1.2 million. A cash payment of $200,000 was paid upon signing the Agreement with the remaining $1 million to be paid in three installments on each anniversary date following the closing (one installment remaining). The Agreement granted a 0.5% net smelter return (NSR) royalty over the Property, half of which can be purchased for $1 million at any time up until the second anniversary of commercial production. Certain mineral tenures covering the Property are subject to various NSR royalties, of which from 50% to 75% can be purchased for amounts ranging from $1 to $2 million.
2023 Mineral Resource Estimate
In October 2023, Copper Fox filed on SEDAR an NI 43-101 Technical Report which included the results of an updated, pit constrained mineral resource estimate (“MRE”) for the Eaglehead project (click for report). The study utilized 120 of the 126 drill holes completed on the project. Metal prices used in the MRE are stated in USD: $3.50/lb Cu, $20/lb Mo, $1,750/oz Au and $10/oz Ag. Metal recoveries used in the MRE are 89.9% Cu, 71.1% Mo, 78.6% Au and 78.1% Ag to concentrate.
Exploration Model
A Plutonic sub-type of porphyry copper (Cu-Mo-Au-Ag) model is being used to guide future exploration to delineate the limits of the mineral resources in the Bornite and East zones and further evaluate the resource potential of the Camp and Pass zones. Highland Valley and Ike are examples of Plutonic sub-type deposits in British Columbia. Porphyry deposits of the Plutonic sub-type can exceed one billion tonnes in size.
The mineralized corridor is located along the southern margin of the Eaglehead intrusive in proximity to the regional scale Thibert fault system. The Thibert fault system is interpreted to have exerted significant control on the location of the mineralized corridor.
Project Geology
The Eaglehead pluton is calc-alkalic, Early Jurassic mulit-phase intrusive ranging from hornblende quartz diorite to granodiorite in composition. Whole rock geochemical studies, the presence of hornblende and ‘fertility’ indicator ratios such as Sr/Y, and V/Sc support the porphyry potential of the Eaglehead project and suggest that the intrusive phases making up the Eaglehead intrusive were derived from a hydrous, oxidized magma at depth.
Age dating (Pb-U zircon) completed in 2021, revised the age of emplacement of the Eaglehead intrusive from 186 +/- 7Ma (K-Ar age) to 195.1 +/- 0.13Ma for the older marginal hornblende quartz diorite and 194.8 +/- 0.1Ma for the younger quartz porphyry. Biotite granodiorite, the youngest intrusive phase is located between the hornblende quartz diorite and the quartz porphyry and only occurs within the mineralized corridor. The 2021 age dating indicates that the Eaglehead pluton was emplaced during a major epoch of porphyry emplacement in British Columbia.
Age dating (Re-Os) of molybdenite mineralization yielded a 194.2 +/- 0.9Ma age indicating emplacement of the copper-molybdenum mineralization approximately 500,000 to 700,000 years after emplacement of the Eaglehead intrusive. Approximately 85% of the porphyry mineralization is hosted in the biotite granodiorite with lesser concentration of the mineralization occurring in the hornblende quartz diorite and quartz porphyry.
Porphyry Footprint
The Eaglehead porphyry system occurs within the mineralized corridor located immediately north of regional scale Thibert Fault system exposed in a northwest trending valley floor that extends from the Camp zone to the East zone. The porphyry mineralization and alteration are interpreted to represent the upper levels of a paragenetically, homogeneous, large porphyry system.
Mineralization
The copper mineralization (chalcopyrite, bornite with assessor primary chalcocite) is associated with potassic, and texturally destructive sericite-chlorite alteration hosted in crosscutting, multi-phase quartz-sulphide veins, quartz vein stockworks and fractures that can contain significant concentrations of gold-molybdenum-silver. The copper mineralization also occurs as stringers, disseminations, with biotite veins and associated with mafic minerals. Several pulses of copper mineralization are evidenced by early-stage chalcopyrite filled veins cross-cut by later stage chalcopyrite-bornite-pyrite +/- molybdenite veins, quartz chalcopyrite veins and pyrite veins. Late-stage magmatic breccia and brecciated zones exhibiting intense potassic alteration occur in the East, Bornite and Pass zones and contain significantly higher concentrations of copper-molybdenum-gold-silver mineralization as seen in drillholes 69A, 79 and 87.
The distribution of molybdenite is more restricted in extent and primarily occurs in quartz-molybdenite and quartz-molybdenite-anhydrite veins and veinlets and along slippage planes and in minor shear zones.
Pyrite has a wider distribution than the copper mineralization and occurs mainly as fracture and vein filling and in quartz vein and quartz veinlet associated with copper sulphides. Pyrite also occurs as disseminations and associated with mafic minerals. The estimated pyrite content in the mineralized zone is estimated to be less than 1%.
Alteration
The mineralization is characterized by alteration phases the grade from a potassic (K-feldspar-hydrothermal biotite-magnetite) core transitioning outward to propylitic alteration (albite, epidote, actinolite, calcite). The potassic and propylitic phases are over printed by both sericite-chlorite-clay and sericite-chlorite-silica +/- pyrite styles of phyllic alteration. The alteration and metal association transitions from dominantly potassic with copper-molybdenum-gold-silver mineralization in the East zone to mainly phyllic with primarily copper with sporadic silver and trace molybdenum-gold mineralization in the Camp zone. These features suggest either a higher level to the porphyry system to the northwest or several over lapping porphyry centers.
The primary characteristics of the mineralized corridor are:
- The mineralization is primarily hosted in biotite granodiorite, with lesser amounts in hornblende quartz diorite and quartz porphyry, common host rocks to porphyry copper deposits.
- The porphyry copper-molybdenum-gold-silver mineralization is characterized by multiple stages of overlapping and cross-cutting copper-molybdenum-iron sulphides exhibiting variable alteration phases and gangue mineral associations. The cross-cutting relations suggest multiple introductions of copper and molybdenite mineralization.
- The mineralized zones exhibit a stong spatial association with magnetic vector inversion anomalies interpreted to represent the potassic core of either a single or multiple porphyry centers due to the presence of hydrothermal magnetite.
- The mineralization and alteration show a strong spatial relationship to a 6km long positive chargeability anomaly. The drilling has tested only a portion of the lateral and horizontal extent of the chargeability anomaly. The mineralization could extend between the currently defined zones and is open to the south and at depth to the north.
- The change in metal associations and alterations to the northwest along the mineralized corridor suggests a progression to success higher levels in the porphyry system as suggested by the depth of the magnetic vector inversion anomalies and the change from copper-molybdenum-gold-silver in teh East zone to almost exclusively copper in the Camp zone. The distribution and intensity of the alteration changes from widespread potassic in the East zone transitioning to dominantly phyllic and propylitic in the Camp zone.
- 173 copper showings located on the south facing slope in the area north of the Camp and Pass zones. These showings cover an area measuring approximately 3km by 2km. Metal concentrations are as follows: 0.06% to 6.90% Cu, 1 to 488 parts per million (“ppm”) Mo, 3 to 5,285 parts per billion Au and 0.02 to 49.2 ppm Ag.
Diamond Drilling
Selected mineralized intervals (at 0.10% Cu cut-off) from the East, Bornite, Pass and Camp zones are listed below.
Zone | DDH | TD (m) | Dip | From (m) | To (m) | Interval (m) | Cu (%) | Mo (%) | Au (g/t) | Ag (g/t) |
---|---|---|---|---|---|---|---|---|---|---|
East | 86 | 453.20 | -65 | 114.91 | 453.24 | 338.33 | 0.329 | 0.03 | 0.076 | 1.23 |
398.37 | 453.24 | 54.87 | 0.709 | 0.032 | 0.086 | 2.06 | ||||
Bornite | 116 | 318.40 | -55 | 111.00 | 75.00 | 64.00 | 0.278 | tr | 0.083 | 1.08 |
140.00 | 251.00 | 111.00 | 0.483 | 0.02 | 0.276 | 1.4 | ||||
Pass | 125 | 609.00 | -70 | 470.00 | 609.00 | 139.00 | 0.18 | 0.013 | 0.09 | 0.76 |
Camp | 29 | 262.10 | -80 | 152.40 | 185.90 | 33.50 | 0.43 | n/a | n/a | n/a |
210.30 | 243.80 | 33.50 | 0.49 | n/a | n/a | n/a |
Notes: tr=element present but in amounts less than 30 parts per million; n/a=not analyzed, capping of higher-grade results was not employed, weighted average interval includes up to 12 m core length of material below the Cu cut-off, intervals do not represent true thickness.
Preliminary Metallurgical Testwork
Two phases of lock-cycle and variability testwork on mineralized samples from the East, Bornite and Pass zones yielded a clean, bulk cleaner copper-molybdenum concentrate that assayed 29.6% Cu, 2.72% Mo, 28.2 g/t Au and 175.9 g/t Ag with predicted metal recoveries of 89.9% Cu, 71.1% Mo, 78.6% Au and 78.1% Ag to concentrate. The Bond Work Indices that ranged from 16.9 to 20.6 kWh/t (average 18.6 kWh/t) and Bond Abrasion Index ranged from 0.211g to 0.554g (average 0.381g).