Around the same time that Underworld made its White Gold discovery, Atac Resources (ATC-V) struck gold in the Selwyn basin, about 55 km northeast of Keno city and on the northern edge of the Tintina gold belt.

Since then, the company, which had its origins in geological consultancy Archer Cathro, has had phenomenal success at its Rackla project. Not only is it planning to release a resource estimate for its Tiger zone in the third quarter, it's also moving ahead with a $25-million exploration program at the 1,660-sq.-km project - doubling last year's budget.

At least eight drills will be deployed to conduct 40,000 metres of drilling at the 185-km-long by 15-metre-wide Rackla project. The bulk of the drilling (30,000 metres) will be conducted at Osiris and other Carlin-type deposits discovered last year along the Nadaleen trend, on the eastern end of the project. Tiger and five oxide gold targets within 5 km of the deposit will see 10,000 metres of drilling.

Atac staked the grassroots Rackla project based on regional prospecting. It discovered the Tiger zone, located in the Rau trend (just west of the centre of the property) in 2008, pulling intervals such as 78.54 metres of 1.71 grams gold (from 71.5 metres) and spent much of 2009 delineating the sulphide, then oxide zones of the deposit. High-grade results from the oxide zone, such as 19.4 metres of 5.29 grams gold (from 84 metres) and 38.8 metres of 17.11 grams gold sent its shares to a then new high above $2.10 last August.

Mineralization at Tiger is hosted in interbedded (dolomitized) limestones and basalt flows. The near-surface, carbonate replacement deposit has an oxide zone about 600 metres long, 200 metres wide and 40 metres thick, and a 350-metre-long, 120-metre-wide, 50-metre-thick sulphide zone.

At the beginning of September, the company followed up its Tiger zone results with the discovery of the Osiris zone, 100 km east of Tiger. With the first hole into Osiris cutting 65.2 metres grading 4.6 grams gold (from 56 metres depth), the possibility of a district-scale discovery sent its shares to more than $7 from $3 in one week.

It wasn't just the potential scale of its project that had investors so pumped up. It was also the type of mineralization at Osiris, which Atac described as "Carlin-type."

The Selwyn basin was formed at the same time and has the same regional-scale thrust faults as those in the Carlin trend as Nevada's Great basin, one of the world's most prolific gold producing areas.

"You show (rocks from Osiris) to any Nevada geologist and their jaw drops because of the similarities," says Mike Burke, a geologist and 20-year veteran of the Yukon Geological Survey. (Burke left earlier this year to join the team at Golden Predator.)

Like Nevada's Carlin deposits, the gold at Osiris is sediment-hosted (in Paleozoic carbonate rocks) finely disseminated, and originated from hydrothermal processes.

Osiris consists of stacked, gold-bearing intervals within favourable limestone debris units that are linked by feeder structures. The limestone debris-flow horizon is 150 to 200 metres thick and has been traced on surface for 2.5 km.

Osiris mineralization is distinct from Tiger in that, true to the Carlin analogue, low-temperature arsenic minerals realgar and orpiment are the main minerals associated with gold, rather than pyrite and arsenopyrite.

The 5-km-long Nadaleen fault also hosts three other Carlin-type discoveries within 8 sq. km: Isis, Conrad, and Eaton.

Just 100 metres west of Osiris is an identical horizon, called Isis - a 150-200 metre thick limestone debris-flow unit. Drilling there returned 17 metres of 0.92 gram gold from 32 metres depth.

End of season drilling at Conrad, 2 km east of Isis, returned 21.1 metres of 8.03 grams gold (from 41 metres depth), while Eaton, which is 400 metres southeast of Conrad, returned 39.8 metres of 1.61 grams gold, 9.64 metres of 3.36 grams gold (both from just over 100 metres depth).

Atac ended 2010 with nearly $27 million in the bank and raised another $25 million in a private placement in February.

http://www.miningmarkets.ca/news/the-yukon-the-new-address-for-gold/1000484680/

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