Modern technologies combined with robust metal prices helped generate many of the domestic and international exploration successes featured at Mineral Exploration Roundup hosted by the Association for Mineral Exploration British Columbia (AME BC) in late January.
But with a few exceptions — primarily in the developing world — most of the featured projects were first found decades ago, reflecting the increasing rarity of surface and near-surface discoveries.
“From 1980 to 2008, Canada’s reserves of metals have been in continuous decline, resulting in levels today that are less than half of those reported at the end of 1980,” warned Mike Villeneuve of the Geological Survey of Canada (GSC).
Villeneuve’s remarks were part of a public geoscience session, “Preparing for the Next 100 Years,” focused on the search for increasingly elusive hidden deposits. He cited Canada’s Targeted Geoscience Initiative as an example of efforts to develop “the next generation” of geoscience knowledge and analytical techniques to effectively target buried deposits and increase discovery rates.
In the meantime, exploration dollars appear to be largely flowing to projects with long histories, as is the case with many advanced projects in B.C., the Yukon and Alaska (TNM, Feb. 6–12/12). Yet another example is the Golden Meadows project of Midas Gold (MAX-T), aptly described as a “rediscovery” by president Stephen Quin.
Golden Meadows is located in the Stibnite-Yellow Pine district at the southern end of the 80-km-long Central Idaho gold belt, a regional shear structure that has produced at least 8 million oz. gold from more than a dozen historic mines.
The Stibnite-Yellow Pine district was the site of a placer gold rush in 1880, which led to lode discoveries in the 1920s that produced an estimated 450,000 oz. gold as a by-product of antimony sulphide and tungsten mining operations. Another 520,000 oz. gold were produced from heap-leach mines from 1974 to the late 1990s.
Quin said the district’s fragmented ownership impeded past exploration efforts.
“We’ve consolidated the land package for the first time in the district’s ninety-year history and have purchased all outstanding royalties,” Quin added. “Integrating the properties allowed us to put together a district-wide picture.”
The project area has been drilled with more than 2,200 holes totalling 175,000 metres at the end of 2011. Current National Instrument 43-101-compliant resources include 2 million oz. gold in the indicated category (40.8 million tonnes grading 1.58 grams gold per tonne) and 3.7 million oz. gold in the inferred category (54.1 million tonnes at 2.15 grams gold), contained within three nearby deposit areas.
Quin described the project as having exploration potential beyond existing resources, and adds that geophysics — notably, airborne electromagnetic surveying — have defined known mineralization while also picking out known targets and finding new anomalies.
Intrusive-related and sediment-hosted gold deposits are the main targets sought, but Quin said there is also “significant value” in antimony and by-product silver and tungsten at Golden Meadows. As a result, Midas is managing its exploration and development programs in parallel, as its management team had previously done to fast track the Minto copper-gold project in the Yukon.
The past exploration efforts of Newmont Mining (NMC-T, NEM-N) have borne fruit for Southern Arc Minerals (SA-V) at its West Lombok porphyry-epithermal project in Indonesia’s Sunda-Banda arc. Newmont had discovered epithermal gold and porphyry copper-gold mineralization on a district-scale in the region starting in the mid-1980s, but stopped these efforts to focus on developing the Batu Hijau copper-gold mine on the neighbouring island of Sumbawa.
Southern Arc began exploring its ground in 2006, targeting epithermal gold, and has since drilled more than 30,000 holes. An initial National Instrument 43-101-compliant resource is expected in mid-2012. The company has also defined 14 porphyry copper-gold targets and tested seven of them, including the gold-rich Selodong porphyry copper prospect.
Chief geologist Andy Rowe suggested other porphyry centres exist on the 101-sq.-km land package, which he said is a “question we need to answer.”
Another “elephant country” project benefiting from historic exploration efforts is the high-profile Wafi-Golpu project in Papua New Guinea, a fifty-fifty joint venture between partners Harmony Gold Mining (HMY-N) and Newcrest Mining.
“It’s a standout project in the league of Oyu Tolgoi,” said Michael Humphries, an exploration manager of Harmony Gold, referring to the world-class copper-gold deposit in Mongolia.
CRA of Australia made the first discoveries in the area through rock-chip sampling in the seventies. Harmony picked up the ground in 2004, but exploration was stymied by periods of political instability until recently. Humphries said the Wafi prospect was found to have “complicated metallurgical issues,” so the company focused on the Golpu intrusive, which appeared to be amenable to block caving.
“We knew we needed a high-grade driver, but the drill results blew our socks off,” Humphries said, citing 892 metres grading 2.3 grams gold and 2.15% copper as an example. “These are spectacular copper and gold grades for a porphyry deposit.”
A recent Bloomberg report stated that Harmony has refused offers in the range of $6 billion to $8 billion for the large-scale project and related land package.
Humphries said the company plans further exploration to test other systems along a favourable, 17-km trend. “This is elephant country, and elephants occur in herds,” he said.
Porphyry copper deposits also tend to occur in clusters, including in Arizona, where Curis Resources (CUV-T) is advancing its Florence copper project. The deposit was discovered in the early 1960s, with previous operators completing studies on both the oxide and sulphide portions of the deposit in the 1970s and again in the 1990s.
Curis, a Hunter Dickinson Group company, acquired the shallowly buried deposit in early 2010 and is advancing it as an in-situ copper recovery (ISCR) project. Dan Johnson, manager of environmental and technical services, noted that ISCR is being employed at several Arizona mines and the process is well suited for the Florence deposit, now in an advanced permitting and engineering stage.
“We have everything we need to develop the project quickly,” Johnson said, noting its excellent infrastructure with respect to water, power and road and rail access.
Mexico has dozens of historic mineral belts that have proven to be favourable hunting grounds for new deposits. Newstrike Capital (NES-V) is finding exploration success in the Guerrero gold belt, which hosts several projects with resources estimated to total 15 million oz. gold and 105 million oz. silver in all categories.
Newstrike has several projects in the re-emerging belt, including Ana Paula, acquired from Goldcorp (G-T, GG-N) in mid-2010. Previous work by Goldcorp focused on a gold anomaly that was drill-tested in 2005, revealing potential for low-grade bulk-tonnage and higher-grade replacement mineralization in sulphide lenses.
Craig Gibson focused his presentation on Newstrike’s recently discovered high-grade breccia zone at Ana Paula, where the discovery hole returned 3 grams gold over a 214-metre downhole length. A subsequent hole returned 7.51 grams gold over 240 metres, including 58 metres at 18.61 grams. Ongoing drilling is aimed at generating a preliminary resource estimate and testing other targets.
NGEx Resources (NGQ-T) showcased its Los Helados copper-gold porphyry deposit, one of several large porphyry systems held by the globe-trotting company in Chile’s Region III, roughly midway between the prolific Maricunga and El Indio belts.
NGEx discovered the talus-covered deposit in 2009 by following up Aster anomalies, with the discovery hole hitting 762 metres of 0.43% copper and 0.22 gram gold, or 0.58% copper equivalent. Subsequent holes returned comparable and higher grades.
Bob Carmichael, vice-president of exploration, said the project is being advanced with a $45-million work program and an initial resource expected later this year.
Another recent discovery showcased at Roundup is the Canahuire gold-copper-silver epithermal deposit, part of the Chucapaca joint venture between Gold Fields (GFI-N) and Minas Buenaventura (BVN-N). The grassroots discovery was made in Southern Peru’s altiplano region at altitudes ranging between 4,800 metres and 5,000 metres. It has since advanced to the feasibility stage, with a current resource of 132.7 million tonnes at 1.4 grams gold, 10.8 grams silver and 0.09% copper, or 7.6 million oz. gold equivalent.
Africa continues to draw exploration companies, with Burkino Faso reaping six new gold mines after introducing a new mining act in 2003. These mines are dominantly low-grade, bulk-tonnage operations, but high-grade targets have been found too, notably by Roxgold (ROG-V) at its Yaramoko property in the Hounde greenstone belt. Drilling of the Bagassi Central gold zones has returned some spectacular high-grade intersections, including one that hit 28.6 grams over 20 metres.
Roxgold president Robert Sibthorpe says soil geochemistry and geophysics have been effective tools in the saprolite- and laterite-covered gold zone discoveries.
Roundup 2012 also featured a session on “Canadian Exploration Highlights” that reflected the broad geographical and commodity diversity of these efforts. Many of the sessions focused on new success stories in historic mining camps, with a classic example being the consolidation of five contiguous former mines and numerous gold prospects in Ontario’s Kirkland Lake camp by Kirkland Lake Gold (KGI-T).
Ontario projects were featured prominently, including Trelawney Mining and Exploration’s (TRR-V) Côté Lake gold project in the Swayze greenstone belt and the Goliath gold project being explored by Treasury Metals (TML-T) near Dryden.
Paul Archer of Virginia Mines (VGQ-T) provided an update on the Coulon project in the James Bay area, which he described as a “very exciting new volcanogenic massive sulphide camp” and the “largest undeveloped copper-zinc resource in Quebec.”
Another undeveloped VMS deposit, the well-known McIlvenna Bay deposit in Manitoba’s Flin Flon camp, was also featured at the Roundup session. Roger March, vice-president of exploration for Foran Mining (FOM-V), told delegates that a new management team had recommenced exploration and engineering studies, building on work by previous operators over the past quarter century. A National Instrument 43-101-compliant resource and a preliminary economic assessment are planned for this year.
The Kami property in western Labrador was also featured in the Canadian Highlights session, with Tayfun Eldem, president of Alderon Iron Ore (ADV-T), providing an update on the company’s plans to develop the project into a producing mine in 2015. The advanced project is surrounded by four producing mines and is less than 6 km from a multi-user railway connecting to the St. Lawrence Seaway.
“We believe we will be the next iron ore mine in Canada,” Eldem said.
Canada’s North was represented by the aptly named North Country Gold (NCG-V) and its Three Bluffs gold project and Walker Lake trend in Nunavut’s Committee Bay greenstone belt. The project is located 280 km northeast of Meadowbank, Nunavut’s newest gold mine, and was first mapped by the Geological Survey of Canada in the 1960s. Iron formation and shear-hosted gold deposits are the main exploration targets. The company’s discoveries to date have potential for both open-pit and underground resources. The project covers only a small portion of the company’s land holdings.
As these and other featured projects show, fresh eyes and concepts are generating new discoveries and resources in known mining camps as well as in under-explored, overlooked and often underestimated regions of Canada and the world.
— Based in Vancouver, the author is a freelance journalist specializing in mining, and is a former editor of The Northern Miner.