Solving Shorty Creek
Freegold Ventures drilling will add pieces to Interior Alaska porphyry puzzle
Last updated 1/28/2018 at 1:17pm
Freegold Ventures Ltd. is testing the idea that a large and previously unrecognized porphyry deposit could lie beneath its Shorty Creek property in the Livengood Mining District of Interior Alaska.
Earlier this month, the exploration company raised C$1.35 million to fund a 3,000- meter drill program that could provide definitive evidence that various zones of copper, gold and molybdenum found across the 26,000-acre Shorty Creek land package are actually pieces of one porphyry copper-gold-molybdenum deposit spanning up to eight miles across.
Shorty Creek puzzle
For at least three decades, geologists have known that Shorty Creek is prospective for gold, copper and molybdenum. With the available data, the explorers concluded that the mineralization seen at surface comes from two separate sources – an intrusive-related gold system in the southern part of the property and a copper-molybdenum system to the north.
Like pieces of a puzzle, Fairbanks-based Avalon Development compiled all of the data from various historical exploration programs to reveal a bigger picture at Shorty Creek. Avalon President Curt Freeman saw what appears to be a zoned porphyry system that covers an area eight miles in diameter.
“While the interpretations of this report represent a departure from previous thinking about the Shorty Creek project area, this is the first time a single study has been able to incorporate all of the available data. Previous investigators focused on individual parts of the larger system, but did not recognize these parts as being integral pieces of a larger porphyry copper-gold-molybdenum system,” Freeman wrote in a 2010 technical report.
While the picture of copper-gold-molybdenum porphyry was becoming evident, some key pieces of the puzzle were still missing. This is something Freegold has been working to rectify since acquiring the Shorty Creek property last year.
To add to mounting evidence of a hidden porphyry system, Freegold completed ground geophysics and soil sampling that blanketed both the gold and copper-molybdenum targets and the area in between.
“We were excited about the geophysics and geochemistry we did up there last year,” Freegold President and CEO Kristina Walcott told Mining News.
“Last year was the first year anyone had ever done ground geophysics, and we did identify two significant, what look like very distinct, porphyry systems,” she added.
On one side of the puzzle is a gold prospect known as Hill 1835.
In 1989 and 1990, 20 relatively shallow holes were drilled at this prospect. Highlights from this historical drilling include 67 meters averaging 1.21 grams per metric ton gold and 58 meters of 0.51 g/t gold from surface.
Freegold’s 2014 exploration program identified gold and bismuth geophysical anomalies that correspond with a strong chargeability (induced polarization) anomaly at Hill 1835 and expanded the breadth of this target area.
While the deepest holes of the historical drilling only reached a depth of 500 feet (152 meters), many of these holes were cutting significant copper mineralization, hinting at a potential porphyry system that could be lurking below.
“It looks very much like the copper is increasing at depth,” Walcott explained
Mapping has indeed found quartz porphyry in a nearby creek bank about 30 meters below the depth of the historical drilling.
By drilling to a depth of up to 300 meters, Freegold will test the idea that the historical drilling fell short of reaching a porphyry deposit underneath.
About 2,500 meters to the northwest of Hill 1835, Freegold’s 2014 program identified a strong chargeability (IP) anomaly stretching across the copper-molybdenum prospect at Hill 1710. Freegold’s soil sampling outlined a 2,000- by 1,000-meter area of strong copper values (up to 669 parts per million copper) with a 1,000- by 800-meter strong molybdenum (up to 235 ppm molybdenum) core.
A portion of this year’s drilling will test what lies underneath this copper-molybdenum prospect.
Freegold hopes a picture of a significant porphyry system emerges from this drilling.
“There are, of course, no guarantees, but it certainly is very compelling to see ground geophysics, airborne geophysics, geochemistry and geology all in agreement,” Walcott said.
Golden Summit PEA
While piecing together the Shorty Creek puzzle, Freegold continues to move ahead with a preliminary economic assessment for its Golden Summit project located less than five miles north of Kinross Gold Corp.’s Fort Knox Mine near Fairbanks.
The Dolphin-Cleary Zone at Golden Summit has an indicated resource of 79.8 million tons averaging 0.66 grams per metric ton (1.68 million ounces) gold; and an inferred resource of 248.1 million metric tons averaging 0.61 g/t (4.84 million oz) gold.
The upper 60 meters of this resource is oxidized, providing a nice layer of gold-enriched mineralization that could be placed on a heap leach pad during the early years of a mine at Golden Summit.
At a 0.2 percent cut-off, the oxide cap of the Dolphin-Cleary zone has an indicated resource of 25 million metric tons averaging 0.55 g/t (439,000 oz) gold; and an inferred resource of 16.6 million metric tons averaging 0.47 g/t (253,000 oz) gold.
Based on the extensive work it has carried out at Golden Summit, Freegold is confident that it can significantly expand this oxide resource with additional shallow drilling.
The PEA is expected to examine the potential for a standalone heap leach operation. The assessment also will include a comprehensive review of the current sulfide resource, with the idea that the mine could be scaled up to a larger milling operation in future years.