In the heart of the copper corridor near Kearny, Arizona a nano-cap junior Prismo Metals is walking between giants and planning what could be the most significant copper discovery in the state since Resolution in 1995 at its Hot Breccia project.

Hot Breccia is within sight of Grupo Mexico’s Hayden smelter and near its Ray mine. Within a 50km radius are major mines including operations owned by BHP [San Manuel, the first block cave mine in North America], Freeport McMoran [Christmas mine] and Capstone Copper [Pinto Valley], and Resolution, the Rio Tinto-BHP joint venture currently in permitting.

“We are definitely in elephant country in one of most productive copper belts in the world, with 75Blb of copper endowment. Resolution, 20 miles to the north, is a great inspiration for us,” said technical advisor Steve Robertson. “With 1.6Bt grading 0.6% copper, Resolution changed the art of the possible about what could be down there at Hot Breccia,” he said.

Geology

Prismo is targeting the same carbonate rocks which host mineralisation at Resolution. At Hot Breccia, company geologists estimates these start at about 400m depth and will continue to about 1000m depth. By comparison, the top of the Resolution deposit occurs at a depth of 1.2km.

“Hot Breccia is so named because it has hydrothermal breccia pipes, vertical features that are the result of high pressure when magma intruded the area. This was an explosive event, which would have broken the material deep underground and brought it upwards”.

“We can see these breccia pipes that come from significant depth and which are responsible for the high-grade copper deposits in Arizona, such as Hermosa and Christmas,” said Dr Lynas Keating, a partner in the company that owns the underlying concessions.

Keating, who studied geology at the University of Arizona and so has a good handle on Arizonan copper porphyries, looked at Hot Breccia in the 1990s when he worked at Kennecott. 

The target horizon is a skarn that was originally limestone, a highly reactive rock. When the hot, acidic mineralised hydrothermal fluids hit the limestone, the chemical reaction caused the metals to rapidly precipitate out, which is why they can hold such high grades. 

The Christmas stock brought in the hydrothermal fluids and the metals and the Christmas mine produced from similar carbonate rocks. The Christmas mine produced about ~25Mt containing 363Mlb of copper as well as silver and gold.

The area has a number of indicators of being the right address for a copper discovery. There are a series of dioritic dykes with the 50 degrees north and 75 degrees northeast orientations which are typical of the Larimide period dating to 55-75 million years ago, related to a much deeper source of stress that allowed big intrusives to come to surface. 

“This would have been 7-8km below surface, which is where many of the most productive porphyries in Arizona formed,” said Keating.

Hot Breccia has been explored and drilled before by Kennecott and Phelps Dodge in the 1970s, when the project was called O’Connell Canyon, obtaining long intervals of skarn with intercepts of copper of up to 5.7%. 

However, the subsequent discovery of the Christmas deposit brought an end to exploration at Hot Breccia. “The Kenncott holes were off the mark and a bit too shallow,” said Robertson.

Hot Breccia is covered with Cretaceous volcanics which were deposited prior to the Laramide intrusive event, and essentially hid it, until the discovery of Resolution, 20km to the north, after this drilling in the 1970s provided a model that there could be something at depth,

Resolution’s geological model provided a blueprint to reexamine Hot Breccia and unlock the copper it may potentially host. “We have evidence that there is a hydrothermal system at depth. We have incredible breccias at surface at top of volcanics.

 When the fluids boil, they are explosive and the rocks come flying up to surface. The angular fragments in the breccia are from carbonate and intrusive rocks. It was a really energetic system,” said Robertson.

Drill programme

Prismo is planning a 5000m drilling programme which could quickly show whether the analogy holds. 

It will test with an initial five 1km-long holes, at a cost of about C$1 million per hole, one of which will likely twin one of the 1970s holes and go deeper, while other targets will test the ZTEM geophysical anomaly, which has a similar size footprint as Resolution does.

This indicates there could be a large sulphide body at depth, with targeting being refined through the use of Artificial Intelligence. Before that though, the company is waiting to be awarded drilling permits from the Bureau of Land Management.

“Prismo has a modern exploration tool box that they didn’t have in 1970s. A ZTEM survey is very good at picking up deep conductors, and there is one sitting under the area of maximum complexity on the property, which is where the limestones are. 

“Limestones are not supposed to be conductive, so they could be full of copper mineralisation. We have a very good chance of hitting a hydrothermal system,” said Robertson.

Origin 

Prismo was formed with the original aim of exploration in Mexico with a portfolio of properties in the Panuco district of Sinaloa, proximal to where 9.9% shareholder Vizsla Silver is exploring. 

In addition to Robertson and Keating, the geological suite at Prismo includes Dr Craig Gibson as chief executive and Dr Peter Megaw as advisor, with Alain Lambert as executive chair, responsible for capital markets. Management and insiders own 28.1% at an approximate average cost of 10c per share. Vizsla Silver 9.9% strategic investor. The company also owns 500,000 shares of Vizsla that it could sell.

Assuming the drilling occurs and hits the target, the timing could not be better for Prismo, which has an option to earn a 75% interest in Hot Breccia. Copper has made it onto the US list of critical minerals, and with an industry discovery rate of virtually zero, potentially tapping into something which could be similar to Resolution would generate a lot of interest.

“Every major copper miner in the world apart from Codelco is working in Arizona. We don’t want a strategic investor at the current share price, but if we get a good hit and our market capitalisation jumps it would be good to get a strategic in, as when they put a check in, it comes with a lot of technical support. 

Hot Breccia shows discovery potential, in an area with existing infrastructure in the state that produces around 68% of all US copper production. 

Sacred land

However, one cloud in the clear blue sky of the Sonoran Desert could be the proximity of the projects’ area to the San Carlos Apache Reservation to the East.

 The San Carlos Apache native Americans are opposing the development of the Resolution mine and the transfer of land it considers sacred by the US government to the project. 

There is no indication that Hot Breccia is located on any sacred land, with Prismo waiting to obtain its drilling permits before formerly initiating outreach to the San Carlos Apache.