PRELIMINARY PORPHYRY CU ASSESSMENT FOR THE CENTRAL TETHYS REGION

The Central Tethys region—consisting of the countries Afghanistan, Armenia, Azerbaijan, Georgia, Iran, Pakistan, and Turkey—was assessed for undiscovered porphyry Cu deposits in 2008 as part of a global mineral-resource assessment. The region hosts 19 known porphyry Cu deposits having an estimated 8,800 million tonnes (Mt) of material containing about 46 Mt of Cu; 1.7 Mt of Mo; 2,100 t Au; and 9,100 t Ag. They formed as a result of the collision and subduction of the Afro-Arabian plate beneath the Eurasian plate during the Late Cretaceous to Miocene. There are also numerous porphyry Cu prospects in the region. Currently, the region produces less than 2 percent of the world’s Cu with Iran being the largest producer. Sar Cheshmeh, Iran, and Reko Diq, Pakistan, are two very large (14 Mt and 12 Mt of Cu, respectively) porphyry Cu deposits in the region. The region has recently drawn the interest of explorationists because of the discovery of porphyry Au deposits such as Copler and Kisladag in Turkey, which contain hundreds of tonnes of Au. These deposits have yet to be assessed for Cu.

The assessment was conducted by a team of international experts on the mineral deposits and resources in the region. The team delineated 11 geographic areas as tracts permissible for porphyry Cu deposits. The tracts ranged in size from 10,280 to 223,380 km². They consist of probable post-collision magmatic arcs and Andean-style volcanic arcs that formed as the aftermath of subduction and crustal shortening. For example, the Chagai tract, where Reko Diq and numerous other deposits and prospects are located delineates superimposed Paleogene and Neogene magmatic arcs. For 8 of the 11 tracts, probabilistic estimates of undiscovered deposits were made. Monte Carlo simulations using porphyry Cu deposit models produced probabilistic estimates of undiscovered resources for four metals found in porphyry Cu deposits: Cu, Mo, Au, and Ag and the amount of rock in the deposits. The simulations determined there is a 50 percent probability of at least 14.3 Mt of undiscovered Cu in the 8 tracts where estimates were made.