Explorers chase signs of Carlin gold

It is still early days in the exploration play for gold in eastern Yukon Territory, but a score of companies got a jump on competitors in 2011 by targeting promising occurrences of gold and pathfinder elements in a frenzy of unprecedented claim staking and reconnaissance.

The early explorers rushed to the region following a report by ATAC Resources Ltd. in September 2010 that it discovered unusual mineralization in the rocky eastern ridges of its 1,600-square-kilometer (618 square miles) Rackla Project.

Atac posted high-grade assays from several zones on Rackla where rocks mimic those found far to the south in Nevada's Carlin Trend, where miners have produced more than 90 million ounces of gold in recent decades.

The junior named the discovery Osiris after the Egyptian god of the underworld in a nod to Underworld Resources Inc., another Yukon junior that made the White Gold discovery farther west in 2009 and touched off the modern-day Yukon gold rush that still continues.

Energized by Atac's report, a slew of explorers rushed to the region, scrambling to identify drill-ready and near-drill-ready targets that could contain Carlin-style mineralization.

Darwin Green of Constantine Metal Resources Ltd. and Adam Travis, president and CEO of Colorado Resources Ltd., were among geologists and others who joined Atac President Robert Carne in reporting the progress of some of these exploration programs at the Yukon Geoscience Forum Nov. 19-23.

A strategic joint venture

"Our history starts with Atac's discovery last September," said Green in describing the genesis of a joint venture that Constantine formed with Carlin Gold Corp. "We thought it was important to get up here and investigate."

Through the JV, the companies hoped to profit from both Constantine's familiarity with mining north of the 60th parallel and Carlin Gold's experience tracking Carlin Trend systems in Nevada. The companies' managers also boast 125 years of combined mineral exploration experience.

Green, who is vice president of exploration at Constantine, said the JV team devoured all of the data it could find, including historic research and government data, and started staking claims just weeks after Atac's announcement.

"Probably our biggest tool was (regional geochemical sediment) data," he told a rapt audience of about 500. "We were looking for the key pathfinders, arsenic, antimony, gold and thallium, if they were there. Add to that some regional-scale antiforms and other structures to make nice traps for some of the unique minerals associated with Carlin systems.

Green and others also described poring over research papers written by companies exploring the Selwyn Basin for uranium and base metals in the 1970s and 1980s.

"We looked at what was better than 10 parts-per-billion gold in the RGS data, and we looked at the graininess around Osiris and the rocks in Nevada in the Carlin Trend.

From this research, the Constantine-Carlin Gold JV created a "witches brew of what you want to see in the database and things started popping out at us," Green explained.

"We also looked at where the Dawson Thrust goes and it created all these ideas, and we went out there and staked them. Now, it's truth time to see what we've got."

The Constantine-Carlin Gold JV now controls 4,967 claims in 12 gold property areas totaling about 1,000 square kilometers (386 square miles). Its exploration team has collected 12,000 soil, silt and rock samples to date as part of a C$1.2 million exploration program.

In September, the companies confirmed the presence of a gold and arsenic soil anomaly (soils with greater than 100 parts-per-million arsenic and greater than 20 ppb gold) spanning 6.5 kilometers (4 miles) in length and 300-1,200 meters in width on its Tut property.

Individual soil samples within this area assayed as high as 2,809 ppb (2.81 grams per metric ton gold) and 58,652 ppm (5.87 percent) arsenic. The JV said other separate areas on the Tut property receiving follow-up evaluation include a zone of gold-in-soil values encountered on a reconnaissance soil traverse 6 kilometers (3.75 miles) west of the first anomaly. This zone is defined by anomalous gold-in-soil values ranging from 56 ppb to 163 ppb gold over a distance of about 1 kilometer (0.62 mile) and is the focus of additional grid sampling, prospecting and mapping.

Initial sampling at the JV's X Block property also encountered several areas with anomalous gold and arsenic, with associated thallium and mercury that are the focus of detailed follow-up work. Separate soil samples have returned values of up to 4,248 ppb (4.25 g/t) gold, 9,756 ppm arsenic, 13.6 ppm thallium and 9.3 ppm mercury. The geological setting of these anomalous sample areas is within the lower Paleozoic strata and structures targeted in the initial staking.

The TUT and X Block properties are located about 140 kilometers (87 miles) northeast of the community of Ross River.

Aggressive staking push

Colorado Resources is another junior that owes its acceleration out of the starting gate, if not its actual birth, to industry excitement about the gold discoveries in the Yukon.

Travis said he attended the 2010 Yukon Geoscience Forum where many in the industry were buzzing about Atac's Osiris discovery, including representatives of Barrick Gold Corp. and Newmont Mining Corp.

The junior rushed out and quickly staked 50 claims before issuing a C$2 million initial public offering.

Colorado returned to the Selwyn Basin and found itself caught up with Newmont and the Constantine-Carlin JV in "a good, old-fashioned staking rush, albeit in February," Travis said. "We were hoping to stake the claims in the spring rather than in February. Newmont cost me an extra C$400,000. At one time, we had three choppers and 23 guys flying from Faro there every day."

Travis said the company focused on staking claims along the shelf margin of the Selwyn Basin. The junior controls 1,400 claims, or about 60 square kilometers (23 square miles) in the region.

"It's certainly not an Atac-size claim block, but it's not bad," said Travis.

"We were told that we had the next best target after Atac. It has the right kind of rocks in the right kind of setting and with the right kind of structure," he explained. "And it is punctuated with the right kind of orpiment-realgar showing right in the middle with decent gold in the trenches and drill holes."

Travis said the results of 14,000 soil samples, 1,200 rock samples, 2,000 line kilometers in a DGEMA survey and 15 trenches identified favorable geology. This along with detailed reports written by earlier explorers in 1979 and 1983 and the impressions of visiting experts from Nevada convinced the junior that it is seeing Carlin-style mineralization in a 4-kilometer- (2.5 miles) long soil anomaly and other targets on its claims.

Newmont spokesman Omar Jabara said the major staked 1,475 claims in the Yukon in 2011, but no other information on the work was available, which is not surprising given that the gold producer has a number of such programs around the globe in its development pipeline.

More gold at Rackla

After completing 32,500 meters in 118 drill holes in 2011 on its Rackla gold project, Carne said Atac is now very comfortable with the term "Carlin-type mineralization."

Among Atac's latest exploration results, drill hole OS-11-058 cut 41.15 meters grading 7.33 g/t gold with 13.72 meters grading 16.23 g/t gold, 2.20 meters grading 10.15 g/t gold and 2.76 meters grading 10.94 g/t gold; and hole OS-11-062 cut 59.44 meters grading 4.32 g/t gold with 19.54 meters grading 8.75 g/t gold and 4.33 meters grading 4.80 g/t gold in the Conrad Zone, one of five Carlin-type gold exploration targets within a 4-kilometer-by-3-kilometer (2.5 miles by 2 miles) area within the Nadaleen Trend.

The Conrad zone lies 1 kilometer (0.62 miles) east of the Osiris zone and 1.5 kilometers (1 mile) east of Isis East, Atac's new high-grade discovery where it intersected 6.77 g/t gold over 15.24 meters in hole OS-11-40.

Additional prospecting in 2011 identified two arsenic, thallium, mercury and antimony soil geochemical anomalies, named Dale and Pyramid, which are located 14 kilometers (9 miles) and 26 kilometers (15 miles), respectively, to the west of Conrad, where orpiment and realgar mineralization was discovered at surface.

Aggressive exploration is planned for 2012 in the area with a focus on the Dale and Pyramid targets along with follow-up work at Conrad and Isis East.

Carne said Atac has explored the region since early in the past decade and credits a Geological Survey of Canada RGS database, which has been in the public domain for a long time, with providing critical clues for its exploration programs.

Carne also said he would like to see more geochemical sampling done in the area.

He said the key was a focus on looking for structures in the region and examining the rocks adjacent to the structures.

The work paid off for Carne and for fellow explorer, Bill Wengzynowski of Archer Cathro & Associates (1981) Ltd., not only with the 2010 Osiris discovery and subsequent related discoveries but also with industry recognition as "Yukon Prospectors of the Year" for 2011.

Other early programs

Lara Lewis, economic geologist for the Yukon Geological Survey, offered forum participants a glimpse of the extensive exploration activity underway all over Yukon Territory in 2011, including in the Selwyn Basin with claims maps prepared by Intierra Mapping.

Lewis said the Selwyn Basin map showed just some of the many companies chasing Carlin-style gold based on regional stream sediment samples and regional mapping of potential host units - Paleozoic carbonates.

"Carlin-type deposits in Nevada occur in clusters and along 'trends', so there is good reason for the staking rush in the area," she said.

Lewis noted that the region also has intrusion-related gold targets, including Golden Predator Corp.'s Cynthia and Harlan properties, as well as silver and base metal-rich properties such as the polymetallic vein silver-lead-zinc Plata property being explored by Rockhaven Resources Ltd.

Other companies either already having identified and/or currently exploring for Carlin-style gold in the area include:

• Goldstrike Resources Ltd. in the Gold Rush Zone on its Plateau property located 85 kilometers (53 miles) north of Atac's Osiris discovery.

• Arcturus Ventures Inc. on its 56-claim, 1,130-hectare (2,792 acres) Keele Project located about 100 kilometers (62 miles) away from Osiris at Keele Peak, Yukon.

• Aben Resources Ltd. explored its Selwyn Recce and Hit properties, permits and newly staked claims cover prospective targets with both Carlin-style stratigraphy and promising geochemical signatures. In addition to being prospective for the presence of Carlin-type gold deposits, Aben said its permits and claims have the potential to host carbonate and sedimentary-exhalative style silver-lead-zinc deposits as well as sediment-hosted copper deposits.

New staking rush

In late August, the YGS released a slew of regional geochemical sample data collected years earlier by the GSC. Yukon government geologists re-analyzed and standardized the database for gold, arsenic, antimony, mercury and thallium values typical of Carlin-style mineralization.

The new information generated additional excitement in an already intense exploration environment and sparked a new round of claim-staking in a region of eastern Yukon Territory bounded on the north by the Dawson Thrust and on the south by the Tintina Fault, a large strike-slip fault extending in a boomerang-shaped belt of rocks from northwestern British Columbia through the Yukon and across Interior and southwestern Alaska. Numerous right deposits of gold have been found and mined along the Tintina Fault in all three jurisdictions.

"People jumped on it pretty darn quick," said Patrick Sack, YGS economic geologist, referring to the new flurry of staking.

Though the industry has been aware that the Selwyn Basin was loaded with lead and zinc since exploration in the 1960s and earlier, its potential for other types of mineralization is far less understood, Sack told Mining News.

"The majors had been up there looking for 10 years or more, but they would not analyze their samples for gold," he said.

With advances in technology, the dataset has improved over the years and "whoever was on the ball, grabbed the data when we released it" and soon began staking claims, Sack explained.

"The thallium anomalies were gone within a week. Helicopters started flying and it was crazy for a while," he said.

Though the YGS has no plans to collect additional RGS data at this time, Sack said the Survey has planned to undertake a new project aimed at mapping the Dawson Thrust and adjacent areas (up to about 25 kilometers, 16 miles wide) to the east. He said the Dawson Thrust is thought to have played an important role in the Osiris discovery. In fact, both the Tiger and Osiris gold discoveries made by Atac resulted from following up on RGS anomalies.

Constantine's Green said the Carlin-style gold play in eastern Yukon "is pretty compelling."

"One of the really exciting things about the Yukon, in general, is how underexplored it is," he said. "That's the kind of place the Yukon is right now. It's very early days. You can go out there with an idea and find something. We encourage everybody to get out there and go prospecting."