Copper Creek is an old mining district located on the east bank of the San Pedro River and on the western slope of the Galiuro Mountains about 75 miles northeast of Tucson, see location map below. According to a story in the Arizona Daily Star, the property has been acquired by Redhawk Resources, a Canadian junior mining company that plans to develop an underground mine for copper, molybdenum, and silver.
The mining district was originally organized in 1883 and there has been some mining and much on-going exploration ever since (see history here). I was involved in some of that exploration.
The property has the potential for a large copper mine, however, most of the known primary mineralization is at a depth of between 1,500 to 3,000 feet below the surface, too deep for an open pit.
What attracted prospectors to the area are hundreds of mineralized breccia pipes which reach the surface.
As the mineralizing pluton was emplaced at depth, the magma pressure and pressure from hydrothermal fluids (hot water and gas), followed fractures to the surface, further fracturing the rock and depositing minerals in the open spaces around the rock fragments, forming irregular, pipe-like structures. Redhawk has a good, concise explanation of the geology here.
Redhawk Resources estimates a resource of 7.75 billion pounds of copper, 150 million pounds of molybdenum, and 32 million ounces of silver at a 0.2% copper equivalent cut-off grade. (The cut-off grade is the level of mineralization below which it is not economic to mine. Any grade above cut-off is economic to mine.) According to Redhawk, the ore grade of measured reserves is 0.72% copper, 0.013% molybdenum, and 2.63 ppm silver. To put that in perspective, the open pit Sierrita mine near Green Valley is operating profitably with an ore grade of 0.24% copper, 0.026% molybdenum, and 1.42 ppm silver. Of course, underground mining is more expensive than open pit mining.
Mining companies usually calculate the value of the mineral deposit at several cut-off grades to allow for variations in mining costs, market prices, cost of mining regulations, taxes and royalties. At the very high cut-off grade of 0.5% copper equivalent, RedHawk estimates the deposit contains mineable resources of 3.4 billion pounds of copper, 69 million pounds of molybdenum, and almost 16 million ounces of silver. This is still a substantial deposit. Remember, “ore” is that part of the mineralization that can be mined at a profit.
The Star reports that environmental organizations such as the Center for Biological Diversity and the Sierra Club are “concerned.” That means, of course, that environmentalists will, as usual, be opposed to resource production and will probably come up with many imagined excuses why the mine should not be developed. Let the games begin.