Anchorage, Alaska —
The property covers a sequence of intrusive and extrusive rocks that contain many known occurrences of nickel, copper and PGEs, as well as gold and lead.
Nevada Star plans to drill three nickel-copper-PGE showings in the Canwell area of the property. This area comprises three zones: Canwell West Ridge, Upper Canwell and Odie. These massive to semi-massive sulphide showings occur along a 1,371-metre ground electromagnetic anomaly. A small Hydrocore portable drill rig is drilling the Ridge zone, where earlier sampling returned 8.56% nickel and 0.86% copper, plus 1.86 grams platinum and 3.16 grams palladium per tonne. Sampling at the Upper Canwell zone returned 6.9% nickel, 2.3% copper, 3.5 grams platinum and 2.6 grams palladium. At the Odie target, sampling returned 0.86% nickel, 0.3% copper, 12.3 grams platinum and 1.2 grams palladium.
“The focus right now is on getting down to the target stage, and Canwell is our first shot,” said Nevada Star President Gerald Carlson, who spoke with The Northern Miner on-site.
The 303-sq.-km property consists of two exploration blocks, which cover terrane that ranges from moderate tundra-covered hills in the south to rugged mountains in the north. Elevations vary from 914 to 1,829 metres above sea level.
The northern property, known as Eureka Creek, lies just west of the Richardson Highway and the Trans-Alaska Pipeline. The other half of the property, dubbed Tangle Lakes, is 13 km south of the Eureka Creek ground. Tangle Lakes’ southern margin is adjacent to the Denali Highway.
The remote rugged parts of the project are accessible mainly by helicopter. There are several poorly maintained trails, and these allow all-terrain vehicles and snowmobiles to gain access to the less rugged areas.
The nearest community is the town of Paxton, at the junction of the Denali and Richardson Highways. The nearest deep-water port is Valdez, about 500 km to the south.
Most of the property is on Alaska state or state-selected land, the chief exception being the northeastern portion of the Eureka Creek area, where there are 76 federal claims. Nevada Star holds a 100% interest in all of the claims, and the state lands are subject to a 3% net proceeds interest upon production.
Over the past four years, the property has been the focus of a joint study involving the state of Alaska, the Geological Survey of Canada, and Nevada Star. The study is aimed at assessing the mineral potential of the region through regional-scale ground and airborne geophysical surveys, as well as geological mapping and sampling. All of this information has been entered into a single database.
The geology comprises Upper Paleozoic to Tertiary-aged formations in the Wrangellia terrain of central Alaska. “Wrangellia is a transported or accreted terrain that was welded on to the side of the old continent,” said Larry Hulbert of the Geological Survey of Canada. “The main feature that defines Wrangellia is a package of volcanics about 4.5 kilometres thick. These rocks have a strike length of more than 2,000 km from the border between Oregon and Washington, all the way up the coast of British Columbia and into the Yukon and Alaska.”
The eastern arm of this rock package hosts numerous nickel, copper and PGE occurrences and can be traced for 900 km from northern British Columbia into the Yukon and Alaska.
“What is so unique about this belt is that it contains about twice as much platinum as palladium, as well as high concentrations of the rarer platinum group elements, such as rhodium, osmium and iridium,” said Hulbert.
Nevada Star has focused its attention on the ultramafic-mafic intrusions of the Nikolai group within the Wrangellia package. Mineralization is primarily hosted in gabbro, clinopyroxenite and serpentinized dunnite, and the primary sulphide minerals are pyrrhotite pentlandite and chalcopyrite.
In the Eureka Creek project area, significant thrust faulting and folding have exposed lower sequences of the Nikolai intrusions. In 1997, Nevada Star started exploring the nickel-copper-PGE potential in the Eureka Creek area. To date, mineralization has been identified as associated with four parallel and northwest-trending belts of ultramafic-mafic intrusions: Canwell, Rainy, Eureka and Ice. In 1998, exploration work moved to the Tangle Lakes area and confirmed the existence of a large ultramafic body that was covered by a thin veil of glacial overburden. The rocks underlying the Tangle Lakes claim block are structurally intact, compared with rocks in the northern Eureka Creek claim block.
“The geology of the north is the same as what we find in the south,” said Hulbert. “However, in the south, the rocks have been undeformed. They look similar to when they were formed 232 million years ago. The north claim block provides the company with a window to what is hidden in the south claim block.”
To identify PGE depletion trends, stratigraphic profile samples were taken through the Nikolai group basaltic volcanics, situated up-sequence of the ultramafic body. Results indicate that the basal 488-610 metres of the basaltic volcanics were extremely depleted in platinum and palladium at the base of the lava flows. This indicates that the platinum and palladium were concentrated elsewhere.
Concentration
“PGEs will only go into one phase, and that is nickel-copper sulphides,” Hulbert continued. “Somewhere within the Tangle complex is a significant concentration of nickel-copper and PGEs. The depletion we see here is much greater than at Noril’sk [in Russia].”
The Noril’sk deposit is estimated to host more than 1.2 billion tonnes of ore with an average grade of 1.84% nickel, 3.85% copper, 7.7 grams palladium and 2 grams platinum per tonne.
In addition, geochemical profiles within the Tangle Lake high-level ultramafic sills showed up to 50% nickel depletion. Another important factor that is considered critical for the deposition of nickel-copper-PGM deposits is a source of sulphur contamination for the magma. The Tangle Lakes and Eureka Creek areas host abundant sulphides in the surrounding sediments and volcanic rocks.
“We are in the heart of a plumbing system for one of the largest magmatic events in earth history,” Hulbert explained. “This is where we think the ‘Big Kahuna’ is.”
Magmatic sulphide ores are thought to form when droplets of a sulphide liquid are assimilated into a silicate magma from a nearby source. If there is significant metal present in the magma and if there is enough mixing of the magma, the sulphide droplets will scavenge metals such as nickel, copper, cobalt and PGEs and concentrate them by way of gravitational settling. The sulphides accumulate near the base of the intrusion, while the overlying volcanic rocks exhibit depleted concentrations of metals.
Two intrusive centres
In 1999, a helicopter-supported magnetic-electromagnetic geophysical survey was flown over both the northern and southern claim blocks. Interpretation of the magnetic data in the Tangle Lakes area indicates that there are two intrusive centres that have laterally extensive sills parallel to the layering of the local country rocks. The intrusive complexes were determined to be 10 miles long and 2 miles wide. The geophysical survey also identified several coincident positive magnetic anomalies and electromagnetic conductors. Additional geophysical surveys were performed, including magnetic, gravity and magnetotelluric traverses across the Tangle Lakes property. Modeling of these data indicates a funnel-shaped wedge of conductive rocks.
In addition to the geophysical surveys, Nevada Star performed soil geochemical surveys, as well as Mobile Metal Ion analysis over the Tangle Lakes area to identify prospective areas covered by glacial overburden. Last year, exploration resumed at the Eureka Creek claims, in the form of mapping, prospecting and sampling. Although there have been five summer
field programs, the actual man-days of exploration completed equates to no more than one field season.
Exploration this year will focus on drilling the known mineral occurrences on the Canwell target, on the northern claim block, and performing an induced-polarization (IP) survey over the Tangle Lakes claims.
“The most prospective area in the Tangle complex has very little rock exposure,” said Carlson. “So we’re going to perform an IP survey and then drill the resulting targets. The timing of that is a little farther down the road, partly because of budget, partly because we are waiting for a few areas to be converted from federal to state land, and partly because we are just preoccupied with the northern property and want to make sure we do everything methodically.”
Nevada Star has 63.5 million shares on a fully diluted basis and about $200,000 in its coffers.
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