As consultants begin to piece together a limited but growing database of information about Noront Resources’ (NOT-V, NOSOF-O) Double Eagle project in northeastern Ontario, the discovery is looking less like a standalone occurrence and more like part of a magma conduit that could contain other massive sulphide deposits.
“We feel we are in the conduit of a magma chamber and could find another blow of massive sulphide down along that conduit,” says Neil Novak, vice-president of exploration for Toronto-based Noront. “The current drilling program is designed to test that.”
Aside from the potential atdepth, Noront is seeing evidence of mineralized sills at the northern flank of the occurrence. Though more drilling is needed to test the theory, these sills could turn out to be similar to the original discovery, adding to the tonnage potential near surface, says consultant Jim Mungall, an associate professor at the University of Toronto and one of Canada’s top researchers of magmatic sulphide deposits.
“(The sills) look like nothing, with just the odd little bleb of sulphides,” Mungall says. “But the fact that they are there, and that they look like the edge of Eagle One, is encouraging. There is certainly the potential for more of these occurrences in the same area.”
Eagle One is a magmatic massive sulphide, a type of deposit that contains nickel, copper and platinum group elements (PGEs) as sulphide concentrations associated with mafic and ultramafic rocks.
The peridotite body appears to be a typical flat-lying layered intrusion turned over on its side. The bottom of the magma chamber containing the massive sulphides lies to the west, overlain by net-textured sulphides, then disseminated sulphides and above that and to the east, barren peridotite.
The mineralized body has a strike length of about 250 metres from the north to the south end, where it starts to plunge steeply. According to Mungall, it looks like a sword blade sticking into the ground — long, flat, wide and thin, with the long axis pointing almost straight down.
Massive sulphide intersections from 36 holes to date have been notable for their high grades of nickel, copper, platinum, palladium and, more recently gold and rhodium, though true widths have not yet been calculated.
Examples include 117 metres (drilled downdip) grading 4.1% nickel, 2.2% copper, 2.1 grams platinum per tonne, and 7.1 grams palladium from just below surface, and 46.2 metres grading 6.25% nickel, 2.75% copper, 1.85 grams platinum, 10.2 grams palladium and 3 grams gold at 113 metres down-hole. Rhodium, which trades at about US$6,800 per oz., grades up to 1 gram in 20 samples tested.
“Some of the sulphide-poor peridotite is pregnant with PGEs regardless of the nickel and copper grades,” Novak says.
In terms of the style of mineralization, Eagle One most resembles the Raglan and Expo Ungava deposits in northwestern Quebec and the Jinchuan deposit in China, all of which contain similar grades of these base and precious metals.
At Raglan, mineralization consists of individual lenses of sulphides associated with ultramafic flows and subvolcanic intrusions.
Nine peridotitic bodies containing pervasive sulphide mineralization, mainly 1-3% finely disseminated pyrrhotite and pentlandite, occur over a distance of 55 km. Thicknesses vary from a few metres to tens of metres, and strike length can vary from tens of metres to 200 metres. The main deposit, Katinniq, consists of over 20 discrete lenses that vary in size from 10,000 tonnes to 1.4 million tonnes with grades ranging from 2.5-5% nickel.
The flows hosting the Raglan deposits are thought to have been fed by the ultramafic intrusions that also host the Nunavik Nickel project belonging to Canadian Royalties (CZZ-T, CRYAF-O). These intrusions occur along a belt several tens of kilometres long in a structural position similar to that of Eagle One along the Sachigo greenstone belt.
In terms of regional structure, the McFauld’s Lake area looks more like the Shaw Dome south of Timmins, Ont., which contains several small nickel-copper deposits, including Redstone and Langmuir. Based on airborne geophysical surveys and sporadic regional drilling near Mc- Fauld’s Lake, Mungall suspects an arc sequence punctured by younger plume-type magma — the source of the nickel-copper-PGE sulphides — a common feature in Archean terrains such as the Shaw Dome.
He says these comparisons can be misleading, however, because although magmatic sulphide deposits share the same basic genesis, each deposit is different.
“Structurally it looks like the Shaw Dome, where there are lots of
little deposits, but compositionally it looks like Jinchuan, which is one of the largest in the world.”
What is known from the global database of ore deposits is that magmatic sulphide deposits rarely occur in isolation and the grades of individual bodies tend to be consistent throughout the system –an encouraging feature for Mc- Fauld’s Lake, where the grades are relatively high.
Back at Eagle One, Noront has followed the 50-metre-wide conduit to a depth of about 250 metres. Deeper drilling was hampered by the capability of the on-site drills used last fall, but Novak says the depth potential will be tested once the company completes deeper ground geophysical work, including gravity, magnetic, time-domain electromagnetics and down-hole induced polarization, that will tell the geologists where to collar their holes.
“Wedon’twant tobe drilling blind because the cost of drilling up there is horrendous,” he says.
He is reluctant to speculate about tonnages for Eagle One until results from all 36 holes are available and specialists in ore reserve calculation have a chance to interpret the data and run a grade-tonnage sensitivity analysis to determine if the deposit has more potential as an open pit or underground operation.
While three drills complete in-fill drilling and test other geophysical targets on the property, Noront is orchestrating a significant regional exploration program to test the potential of the
surrounding area, where there is limited geological information.
Most of the work will focus on the so-called “Ring of Fire,” an arc-like structure outlined by airborne geophysics and drilling and interpreted to represent the Sachigo greenstone belt, where numerous small volcanogenic massive sulphide deposits have been found in recent years.
The regional program, starting with airborne geophysics followed up by ground work, will attempt to outline more anomalies that carry Eagle One’s geophysical signature: an electromagnetic conductor (suggesting sulphide mineralization) with an associated magnetic high (indicating peridotite). Those with the strongest signatures will be drill tested.
Noront recently completed a $26- million financing that will be allocated for on-site and regional exploration and is spending about $2 million per month on the effort. –The author is a freelance writer specializing in mining issues, and principal of Toronto-based GeoPen Communications ( www.geopen.com).
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