Given some 65 to 70 per cent of all the copper produced in the US – and 10 per cent for the entire globe ‒ is sourced from Arizona, it is no surprise the state continues to lure a slew of explorers looking to find what is now considered a green metal.
As a result, two interesting, albeit different, players currently have evolving stories to tell the market as they go about strengthening their respective inventories.
The first is an ASX-listed junior, which is confident it has one of the world’s highest grade copper deposits, with an asset base in Arizona’s north-west.
Meanwhile the other, with its holdings in the state’s south, is being led by a rich and controversial minerals entrepreneur who claims his New York-based outfit has the second largest red metal play in the Lower 48.
Interestingly, both are looking at grounds which have established histories.
West Australian-based New World Resources Ltd (NRW) has already put together a JORC-compliant resource at its wholly-owned Antler play, located some 260 kilometres north-west of Phoenix, of 7.7 million tonnes of ore at 2.2 per cent copper, 5.3 per cent zinc, 0.9 per cent lead, 28.8 grams per tonne silver and 0.18g/t gold for a total copper equivalent of 7.7 Mt at 3.9 per cent.
The junior has completed a scoping study on the project and plans to wrap-up its pre-feasibility documentation during the second quarter of 2023.
A high grade volcanic massive sulphide deposit, Antler outcrops over 750 metres of strike and dips west north-west at 60 degrees.
During the recent RIU Resurgence Conference in Perth, NRW managing director Michael Haynes said previous production at the project between 1916-1970 had yielded 70,000t at 2.9 per cent copper, 6.2 per cent zinc, 1.1 per cent lead, 31g/t silver and 0.3g/t gold, equating to a 5 per cent copper equivalent.
The plan now, Haynes explained, was to continue expanding the resource base while concurrently obtaining all the approvals to bring Antler back into production as soon as practicable.
In this regard, the junior has had three rigs on site and completed more than 40 holes in the past 12 months.
The scoping study, Haynes told RIU delegates, had determined Antler would be an underground operation incorporating longhole stoping with a single decline and a nominal production rate of 1 Mt per annum over an initial 10 years
Between years two and nine, this should see an output of 30,600t a year of copper equivalent metal, generating US$135 million of free cash per annum at a total operating cost of US$85.93/t.
The pre-production capital requirement was expected to be US$201 million (including a US$36.5 million contingency), with another US$29.9 million needed for sustaining costs.
If all goes to plan, construction may begin in the fourth quarter of 2004.
Importantly, Haynes said, NRW had delineated strong soil anomalies over 6 km of Antler strike extensions.
These including more than 300m of untested copper/zinc anomalism at the southern end of the deposit, a 500m long copper anomaly and a 1000m zinc one at Antler Offset as well as another 700m copper one, grading up to 305 parts per million, at Copper Knob – suggesting the overall ore body could have some significant upside.
Meanwhile, to the south, the dual-listed Ivanhoe Electric (IE) – led by well-known enigmatic global explorer Robert Friedland – is developing its Santa Cruz project, which covers 78 square km, including 28 km2 of private land, 31 km2 of Arizona State Mineral Exploration permits as well as 238 unpatented claims over 19 km2.
The company, which listed on the New York and Toronto stock exchanges in the middle of this year, acquired Santa Cruz in mid-2021 after several years of negotiations.
Copper mineralisation on the property was originally discovered over 50
years ago, with the Santa Cruz, Texaco and Park Salyer deposits being identified beneath gravel cover.
Located 11 km west of Casa and just south west of Phoenix, the project sits within a mineralised corridor running between the Ajo and Globe Miami copper mines.
According to IE, this is a fundamental geological feature and is estimated to control around 35 per cent of all known copper metal resources in Arizona.
While the largest of the three bodies is Santa Cruz, this trio of ore bodies may originally have been part of one or more Laramide-age porphyry copper systems that were subsequently dismembered by basin and range extensional faulting.
As it stands, the project has indicated resources of 2.5 Mt of contained copper at an average grade of 0.9 per cent, in addition to inferred resources of 2.3 Mt of contained red metal at 0.9 per cent (using a cut-off grade of 0.35 per cent).
However, when a 1 per cent cut-off grade is applied, Santa Cruz maintains nearly 60 per cent of its contained metal, with 1.4 Mt of copper in the indicated category (at an average grade of 1.7 per cent) and 1.4 Mt in the inferred one (1.9 per cent).
In an investor presentation Friedland had been making before IE’s float, it was stated that during November 2021, Santa Cruz yielded the fourth and 12th largest global copper drill intercepts for the year, with the rig returning 585m at 1.13 per cent and 389m at 1.01 per cent respectively. When converted to length by grade numbers, these became 658m and 384m.
Based on these figures, this ranked the project in the top five copper exploration plays world-wide.
As it stands the deposit, which is made up of both oxide with underlying sulphide material, goes to a depth of around 500m.
It is understood the mining plan is to begin with a heap leaching operation while factoring in the introduction of a potential concentrator sometime in the future.
During early November this year, IE announced the discovery of the
East Ridge oxide zone at Santa Cruz, saying this demonstrated the effectiveness of the company’s proprietary Typhoon surveying system for identifying hidden mineralisation.
Additionally, the explorer told the market it was beginning to receive high grade assay results from its extensive drilling campaign in the Santa Cruz area, and these numbers would be incorporated into the updated mineral resource estimate for the project expected during January 2023.
In terms of copper deposit sizes in the state, only Resolution – the joint venture between the publicly (and dual)-listed mining giants Rio Tinto and BHP ‒ is larger, but it faces significant opposition from First Nations groups.
Oddly, in a strange twist of fate it was Resolution, which was once owned by the now-gone US outfit Magma Copper, that indirectly helped lead Friedland into southern Mongolia to size up the massive Oyu Tolgoi copper-gold deposit – an underground porphyry mine that is now wholly-owned by Rio Tinto.
Around 2001 Ivanhoe Mines Ltd (which was also run by the Chicago-born entrepreneur) purchased Oyu Tolgoi from BHP after the latter paid $3.2 billion for Magma in 1996, only to have the deal go sour and force the mining giant to sell its unwanted Mongolian holdings to the Canadian explorer in order to help avoid bankruptcy.