Promontorio Copper Gold Silver Project
COMMODITY: Copper, Gold and Silver
LOCATION: Chihuahua, Mexico
SIZE: 10,698.7 hectares
DEAL: Earn in to 100% allowing Azure to keep a royalty
Azure’s Promontorio Project is located 25km northeast of the Agnico Eagle “Pinos Altos” gold‑silver mine in the Western Sierra Madre of Chihuahua, Mexico. Promontorio hosts high‑sulfidation gold, copper, and silver mineralization in vuggy silica feeder veins, pipes, and mantos that overlie copper porphyry‑style mineralization at depth. The high-sulfidation system at Promontorio occurs in Tertiary dacitic volcanic and sub-volcanic rocks with mineralization exposed for some 2km through a window of post-mineral volcanics that is up to 500m wide.
Promontorio has seen sporadic mining and exploration over the last 115 years, and to date over 40,000m of drilling has been on the project. Most drilling explored for narrow high-grade copper mineralization that occurs with gold and silver. Copper values of over 40% along with gold values above 25 g/t and silver values of over 500 g/t were obtained from some of the drilling done on feeder veins and a breccia pipe located above the porphyry system on the project. Bulk-tonnage gold and silver also occur at Promontorio in vuggy-silica mantos and volcaniclastics with four holes on the project returning over 100 gram-meters of gold at a cutoff of 0.15 grams. Roughly half of the strike length of the mineralized system at Promontorio been drill tested.
Artisanal mining of narrow high-grade copper-gold-silver vuggy silica veins at Promontorio took place sporadically from the early 1900’s to the middle 1980’s. Modern exploration and drilling at Promontorio began in the early 1990’s when Placer Dome’s Mexican subsidiary CanMex optioned the property from the owners and drilled some 40 reverse-circulation holes on the project from 1993 to 1994. A Canadian junior named Sierra Nevada Gold subsequently optioned the project and drilled it from 1995 to 1997 after rehabilitating many of the underground workings and mapping the surface geology. In 1997 Sierra Nevada Gold hired Mine Development Associates from Reno, Nevada to do a section resource calculation study. Sierra Nevada Gold abandoned the property in 2000. DiaBras, now known as Sierra Metals, next optioned the Promontorio project in 2004 and did a limited I.P./ Resistivity survey plus a ground magnetic survey over the central part of the project. DiaBras completed two drilling programs on the property before abandoning it in 2008. Azure Minerals subsequently optioned the property from the owners and carried out its first drilling program in 2008. Over the following six years, Azure carried out mapping, sampling and various drilling campaigns as well as an I.P./ Resistivity survey and ground magnetics to guide the drilling. The geophysics indicated that there was porphyry-style mineralization deep beneath the high-sulfidation system exposed at the surface, and a couple of 600m deep hole confirmed that. Azure executed the option agreement in 2014 to own the project 100% with no royalty. Based on the two Azure holes that intersected porphyry-style mineralization, Rio Tinto entered into an earn-in agreement in 2015 with Azure, and after extensive geophysics studies, they drilled 9 holes totaling 8783.25m to test the deep porphyry potential of the property. The results failed to meet Rio Tinto’s expectations, and they abandoned the property to Azure in 2017. Only limited exploration work has been done at Promontorio since then.
The Promontorio project is mainly a Tertiary dacite-hosted high-sulfidation gold-silver-copper system located in the Sierra Madre Mountains of western Chihuahua. At Promontorio, high-grade copper, gold, and silver mineralization occurs in vuggy silica feeder veins, and breccia pipes situated above copper porphyry-style mineralization at depth. Bulk-tonnage-style precious metals mineralization occurs vuggy silica mantos and volcaniclastics above and lateral to the feeders. The mineralized volcaniclastics may in fact be diatremes, and further drilling could confirm that. The project is comprised of a core claim block of 187 hectares that Azure Minerals purchased plus 10,512 hectares of surrounding concessions that it staked after first optioning the core block of claims. The entire package of concessions occurs along the northeast extension of an important belt of operating gold mines in Chihuahua that includes the Moris mine, the Ocampo mine, the Pinos Altos mine and the Concheño mine. Outside of the main core group of concessions, geophysics work that Rio Tinto completed indicates that there are obvious targets worthy of further exploration.
Resource calculations done at Promontorio include ones that Mine Development Associates and Roscoe Paul Associates did for Sierra Nevada Gold and DiaBras respectively. Azure Minerals Ltd. also contracted three separate resource studies, and AGP from Toronto, Canada did the most recent of those studies. The results are shown in the following table.