Cliff-Miles porphyry system lies on the southern end of the 7.5 km long Hawilson Monzonite (‘HM’) complex. Porphyry copper-gold mineralization is associated with north-south trending corridor of Jurassic age (191 Ma) monzonite porphyry intrusions and breccias hosted by upper Triassic Stuhini Group rocks. The porphyry system is proximate to the Triassic-Jurassic unconformity; referred to as the “Red Line” (Kyba 2014) recognized as an important geological horizon for copper-gold deposits in the Golden Triangle. The geology and metallogeny of the Cliff porphyry system is similar to the Kerr Deposit of Seabridge Gold’s KSM project, which has an inferred resource of 1.92 billion tonnes grading 0.41% copper and 0.31 g/t gold, containing 19.0 million ounces of gold and 17.3 billion pounds of copper (Seabridge New Release Feb 16, 2017).
The Cliff-Miles corridor is represented by a series of porphyry intrusions including an early Medium-grained porphyry (‘MP’) and inter-mineral coarse porphyry (‘CP’) cut by hydrothermal breccias (‘HBX’). The porphyry intrusions and breccias exhibit pervasive sericitic, and, remnant potassic alteration along with a network of quartz-carbonate veins and disseminated to veinlet pyrite ± pyrrhotite ± chalcopyrite mineralization. The mineralized porphyry intrusions and breccias are subsequently cut by typically narrow 1-4 m thick barren diorite and mafic dikes.
Structural Setting and Control of Mineralization
The exploration and drilling campaigns confirmed a very strong structural control of mineralization in the Cliff-Miles, porphyry corridor. Mineralization tends to occur in both hanging and footwall of the northerly trending Adam fault system, leading to two sub-parallel zones of potassic alteration and Cu-Au mineralization mainly along M-Porphyry and hydrothermal breccias. Elevated gold-grades ranging from 1 to 14 g/t Au are commonly associated with silicification and quartz-carbonate-sulphide veins constrained along contact zones and NW-trending, conjugate faults.
The geological framework, drilling assays and IP anomalies highlighted a central well-mineralized gold-rich zone outlined as 250m-wide, 2,000m-long and 600m-deep. This zone is characterized by extensive sericitic and remnant potassic alteration and gold-rich mineralization. The high-grade gold is commonly associated with silicification in the porphyry and country rocks coincident with resistivity anomalies. Mineralization is constrained within “M” Porphyry and calcareous siltstone/sandstone units and remain open in all directions. The 2020 drilling program highlights are given below.
Highlights
- KH20-37 discovered a substantial gold zone with 83m of 0.68 g/t AuEq. incl. 32m of 24 g/t AuEq. to the north.
- KH20-34 drilled 141m of 0.64 g/t AuEq. incl. 54m of 1.13 g/t AuEq. extending the gold zone to the south.
- KH20-36 drilled 480.8m of 0.33 g/t AuEq. incl. 253m of 0.34 g/t AuEq. and a 56 m sub zone of 0.50 g/t AuEq. providing a true test of the Cliff at higher elevation.
- Steeply west dipping “M” Porphyry and sediments remains untested to the west of the Cliff porphyry system.
- Increasing copper-gold grades and potassic zones indicated a transition to the deep core of Cliff Porphyry system.
The 3D modelling and structural reconstruction has revealed that the Cliff-Miles is a substantial porphyry system with continuous porphyry style mineralization for a strike-length of 4 kilometers. A cluster of northeast trending sub-parallel mineralized zones linked to a much larger magmatic-hydrothermal system underneath. Mineralization tends to occur in both hanging and footwall of the northerly trending Adam fault system. The potassic core zones at Cliff-Miles appear deeper than tested by most of the previous drill holes. The fault bounded porphyry dikes, breccias, alteration patterns and copper-gold grades all suggest the outer shell (“Carapace”) of a calc-alkaline porphyry system.
Highlights
- Near surface gold zone measured as 250m-wide, 2,000m-long and 600m-deep
- Most drill holes are 100-200m apart, with significant vertical and lateral upside potential
- Gold-rich mineralization constrain along syn-mineral faults and breccias.
- 3D modeling indicates M-Porphyry (60%), C-Porphyry (25%) and Hydrothermal Breccia (10%)
- Remnant Potassic alteration, veins and “CPY” content increase with depth > 500m
- Tabular mineralization suggests an ideal open-pit extraction scenario in the initial development stage.
SECTION A-A’
- Cliff/Miles Gold Zone (250m-wide, 2,000m-long and 600m-deep)
- Coincident IP Resistivity Anomaly open to the N and S
- Discovery Hole KH20-37 drilled 83m of 0.68 g/t AuEq. incl. 32m of 1.24 g/t AuEq. in calcareous siltstone units
- Footwall Block open in all directions
- Potential of copper-gold core below 600m
SECTION B-B’
- Cliff/Miles Gold Zone (250m-wide, 2,000m-long and 600m-deep)
- Strong IP Resistivity Anomaly correlate with silicification in “MP”
- KH20-35m tested the upper NW part of the gold zone intersecting 254m of 0.33 g/t AuEq. incl. 33m of 0.66 g/t AuEq.
- Improving Chalcopyrite-pyrite ratio and Cu-Au grades with depth
- Potential of copper-gold core below 600m
SECTION C-C’
- Cliff/Miles Gold Zone (250m-wide, 2,000m-long and 600m-deep)
- Strong IP Resistivity Anomaly correlate with silicification in “MP”
- KH20-34 drilled 141m of 0.64 g/t AuEq. incl. 54m of 1.13 g/t AuEq. confirmed improving grades beyond 500m depth
- Remnant potassic alteration, chalcopyrite and higher Cu-Au grades
- Potential of copper-gold core below 600m
SECTION D-D’
- Cliff/Miles Gold Zone (250m-wide, 2,000m-long and 600m-deep)
- Strong IP Resistivity Anomaly correlate with silicification in “MP” and hydrothermal breccia (“HBX”)
- KH20-36 drilled 490.8m @ 0.32 g/t AuEq. incl. 56.2m of 0.50 g/t AuEq. showing typical Porphyry style mineralization
- Steeply west dipping morphology highlight significant upside potential at depth and to the West
- Potential of copper-gold core below 600m
Drilling from east to west at 60o inclination was exceptionally effective in cutting across the entire stratigraphic column and porphyry copper-gold zones. It also tested the resistivity anomaly and confirmed the presence of deeper high-grade gold mineralization within the calcareous siliciclastic rocks. The intensity of alteration, veins and chalcopyrite-pyrite ratios and Cu grades increases with depth; a key vector towards a high-temperature potassic core in the porphyry systems, which may have a vertical extent of approximately 1.5 km. Some of the drilling highlights includes
Highlight Assays
- 141m @ 0.64 g/t AuEq. in KH20-34 incl. 54m @ 1.13 g/t AuEq. – M Porphyry
- 83m @ 0.68 g/t AuEq. in KH20-37 incl. 32m @ 1.24 g/t AuEq. – Calcareous siltstone
- 490m @ 0.32 g/t AuEq. in KH20-36 incl. 56m @ 0.50 g/t AuEq. – M Porphyry & breccias
- 172m @ 0.64 g/t AuEq. in KH18-08 – Potassic alteration in M Porphyry
- 141m @ 0.70 g/t AuEq. in KH18-16 – Potassic alteration in M Porphyry
- 126m @ 0.50 g/t AuEq. in KH19-30 – Potassic alteration in M Porphyry
