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By Shane Lasley
Mining News 

Mining Explorers 2011: Explorers seek Alaska mammoths

Miners see Last Frontier as prime hunting ground for world-class deposits

 

Last updated 11/6/2011 at Noon



Whether it is multimillion-ounce gold discoveries, copper deposits that measure in the billions of pounds or massive ore-bodies of 20 percent zinc, Alaska is renowned for its mammoth deposits. The prospect of finding another Donlin, Pebble or Red Dog continues to draw explorers to this vast and underexplored corner of the United States.

In the Survey of Mining Companies: 2010/2011, conducted by the Fraser Institute, top executives from 494 mining and mineral exploration company's ranked Alaska as having the highest mineral potential out of 79 jurisdictions worldwide.

"We like Alaska for a lot of reasons, not the least of which is that in the last 20-25 years, there have been some very large gold deposits discovered in this jurisdiction," explains Kiska Metals Corp. President and CEO Jason Weber.

The same group of miners that voted Alaska "most prospective," ranked the Last Frontier a dismal 57th in comparative infrastructure.

The limited access, combined with the Far North state's rugged terrain, Arctic weather and high exploration costs, has kept much of Alaska's vast mineral wealth locked away.

"Alaska hasn't experienced near the amount of exploration that has taken place in British Columbia and the Yukon (Territory)," according to Millrock Resources Ltd. Vice President of Exploration Phil St. George.

With mineral deposits in more easily accessible parts of the world harder to come by, junior explorers and senior miners alike are hunting for the mammoth deposits lurking in America's Last Frontier.

"I, and others, think there is a lot of potential to find other Pebbles, other Donlins, other huge gold systems," St. George said.

Exploring TGB East

The Tintina Gold Belt, a particularly rich and vast aurum province that sweeps some 1,350 kilometers (850 miles) across the middle of the Alaska, hosts such large Alaska gold deposits as Fort Knox, Pogo, Donlin and Livengood. These world-class discoveries only begin to account for the source of more than 17 million ounces of placer gold recovered from the streams of the Golden Arch, making it a favored destination for explorers seeking the precious metal.

Alaska's portion of this rich gold province can be divided into two distinct groups - the eastern extent, which runs from the Alaska-Yukon border some 480 kilometers (300 miles) into the state, and the 190,000-square-kilometer (74,000-square-mile) Kuskokwim Gold Belt in southwestern Alaska.

In addition to hosting two of Alaska's four operating hardrock gold mines, the eastern half of Alaska's Golden Arch is home to the 20-million-ounce Money Knob gold deposit at International Tower Hill Mines Ltd.'s Livengood project.

"There are not a lot of 20-million-ounce (gold) deposits being found globally, this is one of them," touts Tower Hill CEO James Komadina.

As Tower Hill continues to expand and upgrade Money Knob for a mine capable of producing some 500,000 ounces of gold per year, the junior is seeking new deposits across its 145-square-kilometer Livengood land package.

The emerging story in the eastern end of the Tintina Gold Belt, though, could be the rich placer districts that have yet to give up the lode source of their alluvial gold.

Rolling Thunder, an intriguing program launched in 2010 by junior explorer Full Metal Minerals Ltd., is targeting the source of more than half a million ounces of placer gold recovered from streams draining the rolling hills of the Fortymile Mining District.

Recognizing that the belt of Cretaceous-age deposits, prospects, and placer gold mines of Yukon Territory's White Gold District trends northwest into Alaska, Full Metal geologists surmised that similar mineralization might be the undiscovered lode of the alluvial gold-producing streams in the neighboring Fortymile district on the stateside of the border.

Using placer gold-producing streams to vector their search, Full Metal geologists traversed the hilltops and ridges of some 145,500 acres of the explorer's Rolling Thunder claims in the Fortymile. The company said this reconnaissance sampling and mapping has identified multiple areas of strong alteration and quartz veining reminiscent of White Gold.

Millrock has completed similar prospecting at its some 23,000 hectares (57,000 acres) of claims in the Fortymile district and the project-generating explorer said it is looking for a partner to continue this exploration.

Further west, Full Metal is carrying out a program comparable to Rolling Thunder across a large package of state of Alaska mining claims it staked early in 2011 in the Circle Mining District, situated about 130 kilometers (80 miles) northeast of Fairbanks. The streams of this historical district have produced more than 1 million ounces of placer gold but a significant hardrock source has yet to be found here.

Rob McEwen-led US Gold Corp. is also seeking the source of historical placers in the eastern portion of the Tintina Gold Belt. In July, the Toronto-based major cut an exploration-purchase deal on Tri-Valley Corp.'s Richardson property about 115 kilometers (70 miles) southeast of Fairbanks.

Some 118,640 ounces of placer gold and 2,357 ounces of lode gold have been mined from this district-scale property since 1905.

Although the eastern half of the Tintina belt is best known for its intrusive-related gold deposits, explorers are also finding copper, zinc and silver in volcanogenic massive sulfide and porphyry deposits here.

Full Metal Zinc Ltd. is exploring a carbonate replacement style deposit rich in zinc, lead and silver at its Fortymile project, found in the placer gold district that bears the same name.

Heatherdale Resources Ltd. is exploring precious metals-enriched VMS mineralization at its Delta project, located in the southern margins of the Tintina Gold Belt about 58 kilometers (36 miles) southwest of the town of Tok.

An inferred resource of 15.4 million metric tons grading 0.6 percent copper, 1.7 percent lead, 3.8 percent zinc, 62 g/t silver, and 1.7 g/t gold has been calculated for Delta. Explorers also found large massive sulfide boulders on the 39,840-acre, or 16,123-hectare, property that average 113 g/t silver 7.3 percent lead, 5.6 percent zinc, 113 g/t silver and 0.7 g/t gold.

"Delta is an early-stage project, but it also represents an emerging massive sulfide district with the potential to be in the top tier of global districts of its type," Heatherdale President and CEO Patrick Smith said of the find.

Kuskokwim Gold Belt

At the western end of the Golden Arc lies the Kuskokwim Mineral Belt, a 645-kilometer- (400-mile-) long gold-rich expanse that runs northeast from the Goodnews Bay region of Southwest Alaska.

The 40-million-ounce Donlin gold deposit - being developed by Barrick Gold Corp. and Novagold Resources - highlights the potential of the western portion of the Tintina Gold Belt and the expense of building a mine in Alaska.

Preliminary estimates released by NovaGold in September anticipate capital requirements of US$7 billion to build the mine facilities and supporting infrastructure at the enormous deposit.

Though these costs seem staggering, the Donlin Gold partners seem confident the feasibility study currently underway will outline a project with positive economics.

"The updated study is expected later this year and we anticipate permitting will commence shortly after that," Barrick Regional President, North America Greg Lang said a day after the estimated costs were announced.

Over the past several years, majors and junior explorers alike have scoured the region in search of other large intrusive-related gold deposits, uncovering several promising prospects.

Invenio Resources Corp., a newcomer to Alaska, is looking for Donlin-style mineralization at its Ganes Creek property about 40 kilometers (25 miles) west of McGrath.

Ganes Creek - which is famed for its enormous gold nuggets, including the 5th- and 13th-largest ones ever found in Alaska, at 122 and 62.5 troy ounces, respectively - has given up some 250,000 ounces of placer gold and an estimated 734,000 ounces of the alluvial aurum still remains. The coarse nature of the gold suggests a nearby lode.

In the search for the hardrock source, Invenio is targeting two styles - structurally controlled vein systems with the potential to host high-grade gold and lower grade disseminated mineralization.

Vinasale, found on the northern end of the Kuskokwim Gold Belt about 26 kilometers (16 miles) south of McGrath, is another intrusive-related gold project that saw drilling in 2011.

A 4,000-meter drill program carried out by Freegold Ventures Ltd. in 2011 was designed to upgrade and expand a recently calculated 1.33-million-ounce gold resource at Vinasale.

Besides Donlin Creek-style mineralization, the Kuskokwim belt also hosts Nixon Fork, a carbonate skarn deposit rich in copper, silver and high-grade gold; several mercury-antimony deposits; and a large past-producing placer platinum deposit.

World-class porphyries

Paralleling the Tintina Belt to the south lies a band of mineral-rich terranes, or series of related rock formations, drawing the attention of senior and junior miners. This arc consists of the Wrangellia Composite and Kahiltna terranes, two interrelated but distinct assemblages.

The Kahiltna Terrane - home of the enormous Pebble deposit being advanced by Anglo American plc and Northern Dynasty Ltd. - is highly regarded for its potential to host other world-class porphyry copper-gold and intrusive gold deposits.

With its 80.6 billion pounds of copper, 107.4 million ounces of gold and 5.6 billion pounds of molybdenum, the Pebble deposit ranks amongst the world's largest for any of these metals - combined it is extraordinary.

Formed when the Wrangellia Composite Terrane thrust up the ocean floor as it collided with Alaska and pumped with copper and gold-bearing fluids at least twice, the more that 650-kilometer (400-mile) long Kahiltna Terrane provides the ideal setting for explorers to search.

"The discovery potential is very high for porphyry deposits generally in this arc environment, but I would also say that Pebble-look-alikes are probably not likely. However, this does not preclude the potential to find other large porphyry deposits with their own unique sets of characteristics. So, we should not over-focus on the Pebble model, but we should focus more on the favorable environment that Pebble represents," Pebble Partnership Chief Geologist Jim Lang explains.

About 280 kilometers (175 miles) northwest of Pebble, Kiska Metals is seeking additional large porphyry deposits at its Whistler gold-copper.

The 527-square-kilometer (203-square-mile) Whistler property hosts one deposit with an estimated 3.1 million ounces of gold, 769 million pounds of copper and 13.2 million ounces of silver. Other prospects here are showing the potential to be significantly larger than this initial find.

Immediately west of Whistler, Millrock Resource Inc. and Teck Resources Ltd. are seeking large intrusive-style or porphyry-related gold deposits on the expansive Estelle project.

The 2,500-meter program carried out in 2011 is the first drilling at Estelle since Millrock picked up the 246-square-kilometer (95-square-mile) property in 2008.

Though the Kahiltna assemblage is best known for its porphyry and other intrusive related copper and gold projects, the region also is highly prospective for other styles of mineralization.

"All over the Kahiltna Terrane keep your mind open to any style of mineralization - it could be VMS (volcanogenic massive sulfide), a skarn or a great big vein," Millrock President and CEO Greg Beischer told Mining News.

A great big vein is what Corvus Gold Corp.'s project partner, WestMountain Index Advisors Inc., is hoping to mine at the Terra project some 30 kilometers (19 miles) west of Estelle.

The company is currently setting up a small-scale mill and gravity circuit designed to process ore from the Ben Vein, a one-meter thick high-grade vein-system that averages about 19.8 g/t gold. While setting up the mill, WestMountain is drilling to extend the vein along strike and at depth with the aim of adding to the 168,000 ounce of gold currently outlined.

The Wrangellia Terrane, a subset of the larger composite terrane that bears the same name, stretches east from Southcentral Alaska through southern Yukon Territory and along the coast of British Columbia. This island arc is known for its nickel and platinum group elements as well as copper-gold porphyries.

Surface showings of up to 15 percent nickel, 7 percent copper and 170 g/t of combined PGE-gold-silver are found at Pure Nickel Inc.'s Man project - located on the southern slopes of the Alaska Range about 265 kilometer (165 miles) southeast of Fairbanks.

Though exploration in recent years has focused on discovering an ultramafic intrusion believed to be the source of surface nickel mineralization, two other metals - platinum and palladium - have grabbed the spotlight at the property.

A US$4.8 million exploration program funded by JV partner Itochu Corp. carried out in 2011 followed up on the previous year's drilling, which encountered two platinum group element-enriched horizons stretching along the property's Alpha complex.

Corvus Gold's Chisna project - about 12 kilometers (20 miles) east of Man - is a 914-square-kilometer (353-square-mile) land package that encompasses multiple copper and gold prospects. A US$2.3 million exploration program funded by Ocean Park Ventures Corp. focused on a newly discovered gold zone known as Golden Range.

A 280-kilometer (175-mile) long area of rare earth element soil anomalies has also been outlined in this region along the southern slopes of the Alaska Range.

Alaska Peninsula porphyries

A belt of much younger porphyries can be found further southwest on the Alaska Peninsula and Aleutian Islands.

This active island arc on the Ring of Fire has received limited modern exploration but is known to host both epithermal gold and porphyry copper-gold mineralizing systems.

Several prospects have been identified along the nearly 1,600-kilometer (1,000-mile) long peninsula and island chain.

Full Metal has an agreement to explore around 1.4 million acres of prospective Native-owned land on the Alaska Peninsula. The Pyramid copper-molybdenum porphyry and Unga-Popov epithermal gold projects highlight the potential of the region.

Pyramid - which hosts 125 million metric tons of near-surface mineralization grading 0.403 percent copper and 0.025 percent molybdenum - is being drilled by Full Metal and Chile-based project partner Antofagasta Minerals S.A.

Unga-Popov - an epithermal gold project on an island about 40 kilometers (25 miles) south of Pyramid - was also the target of partner-funded exploration in 2011. This property - which hosts two historical resources; Apollo with 280,000 metric tons averaging 27.7 g/t gold and 92.6 g/t silver and Centennial, which has about 6 million metric tons at 1.5 g/t.

Redstar Gold Corp. - which signed an agreement with Full Metal in June giving it the right to earn up to a 75 percent interest in the Unga-Popov - began drilling the gold project in September. The 2011 drill program focused on confirming and expanding the historical high-grade gold mineralization.

Zinc-copper-rich Northwest

The western reaches of the Brooks Range - a chain of mountains that spans the more than 970-kilometer (600-mile) width of Alaska north of the Arctic Circle - is home to both sedimentary exhalative deposits with extraordinarily high zinc grades and outstanding copper-rich VMS deposits.

Averaging 20 percent zinc over its first two decades of production, the Red Dog Mine, co-owned by Teck Resources Ltd. and NANA Regional Native Corp., is an example of the potential of this region.

"Red Dog is one of the greater lead-zinc deposits in the world, and there is more potential for those in Northwest Alaska as well as other places (where) there are Paleozoic rocks that are similar to Red Dog," observed Millrock Vice President of Exploration Phil St. George.

As Teck continues to mine Red Dog, it is seeking similar deposits in the region. Anarraaq - a prospect with a preliminary resource of 18 million metric tons grading 18 percent zinc, 5.4 percent lead, and 85 g/t silver about 11 kilometers (8 miles) northwest of the mine - is one of several targets of this search.

Zazu Metals Corp. is currently studying the feasibility of mining Lik, a zinc-lead-silver deposit about six miles (10 kilometers) west of Anarraaq.

The ore-body at Lik is divided into two deposits separated by a fault - the near-surface Lik South has an indicated resource of 18.74 million metric tons grading 8.08 percent zinc, 2.62 percent lead and 52.8 grams per metric ton silver; and the deeper Lik North has an inferred resource of 5.18 million metric tons grading 9.65 percent zinc, 3.25 percent lead and 51 g/t silver.

The VMS potential of Northwest Alaska is exemplified by NovaGold's Arctic deposit. A preliminary economic assessment prepared for this copper-rich deposit envisions a 4,000-metric-ton-per-day-mine producing some 1.7 billion pounds of copper, 2 billion pounds of zinc, 291 million pounds of lead, 266,000 ounces of gold and 22 million ounces of silver over a 25-year mine-life.

"This preliminary economic assessment demonstrates the robust economics of developing one of the highest-grade VMS deposits in the world," Van Nieuwenhuyse said.

Arctic is one of several deposits in a belt of precious metals-enriched volcanogenic massive sulfide mineralization that stretches along the southern slope of the Brooks Range in Northwest Alaska.

Andover Ventures Inc.'s Sun deposit, for example has a historical resource of 20.3 million metric tons averaging 74 g/t silver, 1.9 percent copper, 4.5 percent zinc and 1.2 percent lead.

Andover is having this resource updated to NI 43-101 compliance based on 50 holes drilled here, including drilling completed in 2011.

Sun11-28, which tested a 250-meter wide gap in the previous drilling, cut 10.65 meters averaging 2.56 percent copper, 4.47 percent zinc, 0.81 percent lead, 63.8 g/t silver and 0.22 g/t gold.

Bornite a large under-explored copper deposit located about 27 kilometers (17 miles) to the southwest

VMS, REE in Southeast

In the opposite corner of Alaska, the southeast panhandle has no shortage of precious, base and rare earth metals targets.

A 450-mile-, or 725-kilometer-, long belt of VMS deposits stretches along the length panhandle encompasses such metals-rich deposits as Niblack, Greens Creek, Palmer and, as the belt continues into British Columbia, Windy Craggy.

Heatherdale Resources Corp.'s Niblack project was the target of the largest exploration program in Southeast Alaska.

According to a resource estimate released in early March, Niblack contains indicated resource of 4.1 million metric tons averaging 1.13 percent copper, 2.32 grams per metric ton gold, 2.27 percent zinc and 38.7 g/t silver; and an additional inferred resource of 1.74 million metric tons grading 1.21 percent copper, 1.77 g/t gold, 2.29 percent zinc and 25.90 g/t silver.

With a 2011 exploration program expected to top US$20 million by the close of the year, Heatherdale and its joint venture partner, Niblack Mineral Development Inc., are rapidly advancing this precious metal-rich VMS deposit toward a production decision.

At some 8 million tons of reserves averaging 426 grams per metric ton silver, 3.4 g/t gold, 10.5 percent zinc and 3.8 percent lead; Hecla Mining Co.'s Greens Creek host's the most silver-enriched of the known deposits along this trend.

Constantine Metal Resources Ltd.'s Palmer Project at the north end of Alaska's portion of the VMS belt contains about 31 g/t silver - along with 2 percent copper, 4.8 percent zinc, and 0.30 g/t gold.

Anchored by Ucore Rare Metals Inc.'s Bokan Mountain project to the south, the length of the Southeast Alaska Panhandle is also prospective for REE deposits.

An inaugural NI 43-101-compliant resource calculated for Bokan earlier this year estimates the deposit hosts an inferred mineral resource of 3.7 million metric tons grading 0.75 percent total rare earth oxides.

Though not particularly large or high-grade, the Bokan deposit is believed to be 39 percent heavy rare earth oxides, which are the more valuable REEs.

Technology Metals Research co-founder Jack Lifton - considered to be the leading authority on the sourcing and end-use trends of rare and strategic metals - said Bokan Mountain is key to securing a domestic supply of the critical heavy REEs in THE United States.

"Because of its proportion of heavy rare earths, (Bokan) is the most desirable deposit to be developed in the United States," Lifton said. "For the future of this country, this development in Alaska is very important."

A trend of REE prospects has been identified along the entire 220-kilometer (135-mile) length of Prince of Wales Island; which is a subset of a 560-kilometer (350-mile) belt prospective for these strategic metals. All told, more than two dozen prospects have been identified along the panhandle.

Author Bio

Shane Lasley, Publisher

Over his more than 11 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.

Email: [email protected]
Phone: (907) 726-1095
https://www.facebook.com/miningnewsnorth

 

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