The mining newspaper for Alaska and Canada's North
The mining newspaper for Alaska and Canada's North
First 2019 hole taps new metals zone at exploration target North of 60 Mining News – September 13, 2019
A drill tests Sunshine, one of many metal-rich volcanogenic massive sulfide targets that have been identified across Trilogy Metals' Upper Kobuk Mineral Project in the Ambler District.
Rick Van Nieuwenhuyse, John Proffett and Andy West investigate the highly folded Gnurgle Gneiss outcrop north of the Arctic deposit at UKMP.
The initial results from 2019 drilling at the Upper Kobuk Mineral Projects in Northwest Alaska has the Trilogy Metals team excited, especially the first hole from the Sunshine exploration target about eight miles (13 kilometers) west of the Arctic Mine project.
The US$18.2 million carried out this year at UKMP included six holes (1,357 meters) of exploration drilling at the Sunshine prospect, 10 holes (7,610 meters) of resource upgrade and expansion drilling at the Bornite copper deposit and 11 holes (2,405 meters) of drilling to provide additional geotechnical and hydrological data needed for a coming feasibility study for the Arctic Mine project.
The initial batch of assay results is from four holes drilled at Bornite and one hole drilled at the Sunshine exploration target, where the drill tapped rich zones of volcanogenic massive sulfide mineralization reminiscent of Arctic.
"The four mineralized holes from Bornite show that the copper-mineralization is continuous throughout the Upper and Lower Reefs," said James Gowans, interim president and CEO, Trilogy Metals. "However, we are excited with the results from our recently completed regional exploration program where we have intersected VMS polymetallic mineralization at Sunshine with grades and thicknesses comparable to Arctic. Of particular excitement is the discovery of a new horizon that lies above known sulfide horizons."
Upgrading, expanding Bornite
All four of the 2019 infill and step-out holes that Trilogy has received assay results for continue to cut the rich copper mineralization Bornite is known for.
At a cut-off grade of 0.5 percent, the open-pit portion of Bornite hosts 40.5 million metric tons of indicated resource averaging 1.02 percent (913 million pounds) copper; and 84.1 million metric tons of inferred resource averaging 0.95 percent (1.77 billion lb) copper.
With none of the cobalt yet upgraded to the indicated category, the Bornite open-pit hosts 124.6 million metric tons of inferred resource averaging 0.017 percent (45 million lb) cobalt.
At a cut-off grade of 1.5 percent, the below-pit portion of Bornite hosts 57.8 million metric tons of inferred resource averaging 2.89 percent (3.68 billion lb) copper and 0.25 percent (32 million lb) cobalt.
This year's US$9.2 million drill program at Bornite, which is being funded by South32 Ltd., focused primarily on upgrading and expanding the underground mineralization.
At a cut-off grade of 0.5 percent copper, results from the first four holes include:
• RC19-257, drilled within the eastern portion of underground inferred resource, cut three mineralized intervals, including: 3.7 meters of 1.32 percent copper from 546.2 meters; and 4.4 meters of 2.6 percent copper from 587.4 meters.
• RC19-258, drilled about 150 meters north of the existing resource, cut three mineralized intervals, including 23.2 meters of 0.76 percent copper from 636.3 meters.
• RC19-259, drilled about 425 meters north of RC19-257 cut seven mineralized intervals including: 56.1 meters of 1.81 percent copper from 512.1 meters.
• RC19-261, drilled right on the northern boundary of the underground resource, cut six significant mineralized intervals: 2.9 meters of 2.63 percent copper from 304.6 meters; 35 meters of 1.98 percent copper from 387.4 meters; 16 meters of 2.02 percent copper from 426.6 meters; 54.1 meters of 1.11 percent copper from 526.6 meters; 3.1 meters of 1.84 percent copper from 651.9 meters; and 29 meters of 1.47 percent copper from 661.6 meters.
With the completion of the 2019 drilling at Bornite, South32 has invested US$30 million in drilling at Bornite over three seasons. The Australia-based major now has until January to decide to acquire a 50 percent joint venture interest in the Upper Kobuk Mineral Projects by paying Trilogy Metals US$150 million.
Exploring Sunshine
In addition to investing the money to keep its option in good standing, South32 agreed to match a US$1 million investment made by Trilogy for district-scale exploration across the Ambler Mining District with a focus on identifying and testing new drill targets within the Ambler Volcanogenic Massive Sulfide Belt that is covered by the UKMP property.
This work began with district-wide VTEM (versatile time domain electromagnetic) and ZTEM (z-axis tipper electromagnetic) geophysical surveys flown this spring along the entire belt of rocks that already hosts dozens of known VMS deposits and prospects.
The results from the geophysics was incorporated in Trilogy's already extensive dataset encompassing geology, geochemistry, geophysics and over 150,000 meters of historical drilling accumulated over four decades of exploration.
After compiling the data, Trilogy and South32 decided to complete six holes at Sunshine, where historical drilling tapped substantial widths of massive sulfide mineralization in the same stratigraphic horizon as the world-class Arctic deposit to the southeast.
In 1997, Kennecott Mines estimated that Sunshine hosts 20 million metric tons of resource averaging 1.4 percent copper, 2.5 percent zinc, 0.5 percent lead and 28.1 g/t silver. While not compliant to modern reporting standards, this historical resource demonstrates the tenor and potential of the deposit.
The first hole drilled at Sunshine this year, SC19-019, encountered five zones of Arctic-like VMS mineralization, including a newly discovered high-grade zone. Highlights include:
• 9.1 meters of 3.02 percent copper, 1.42 percent zinc, 0.27 percent lead, 0.14 g/t gold and 24.65 g/t silver in New Zone;
• 3.3 meters of 1.68 percent copper, 1.77 percent zinc, 0.47 percent lead, 0.12 g/t gold and 27.57 g/t silver in Zone 1;
• 3.7 meters of 4.74 percent copper, 0.97 percent zinc, 0.13 percent lead, 0.15 g/t gold and 28.96 g/t silver in Zone 2;
• three meters of 0.75 percent copper, 1.4 percent zinc, 0.35 percent lead, 0.08 g/t gold and 21.02 g/t silver in Zone 3; and
• 7.88 meters of 2.23 percent copper, 5.62 percent zinc, 1.1 percent lead, 0.18 g/t gold and 46.95 g/t silver in Zone 4.
These grades are similar to Arctic, which hosts 43.04 million metric tons of probable reserves averaging 2.32 percent copper, 3.24 percent zinc, 0.57 percent lead, 0.49 g/t gold and 36 g/t silver.
A 2018 prefeasibility study detailed plans for an open-pit mine at Arctic and a 10,000-metric-ton-per-day mill that is expected to produce more than 159 million pounds of copper, 199 million lb of zinc, 33 million lb of lead, 30,600 oz of gold and 3.3 million oz of silver annually over a 12-year mine-life.
A feasibility study for Arctic is underway and permitting for this first mine in the mineral-rich Ambler Mining District is expected to begin by early 2020.
Over his more than 16 years of covering mining and mineral exploration, Shane has become renowned for his ability to report on the sector in a way that is technically sound enough to inform industry insiders while being easy to understand by a wider audience.
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