Abstract Iran is a resource-rich country, with large deposits of iron, copper, zinc, and gold, as well as industrial minerals and oil and gas. Most of these resources were formed in response to complex and protracted contractional deformation events related to the subduction and eventual closure of the Neotethys ocean in the late Mesozoic and Cenozoic. Here we focus on porphyry Cu ± Mo ± Au and related epithermal Au deposits, which were once thought to be synonymous with subduction, but are now recognized to also form during collisional and other postsubduction tectonic processes. Recent advances in tectonic and paleogeographic reconstructions, and new geochronological and geochemical data reveal that in fact most of Iran’s major porphyry and epithermal deposits fall into this postsubduction category (e.g., Sungun, Sari Gunay, Meiduk, Sar Cheshmeh). The same applies to several major deposits in neighboring Turkey (e.g., Kişladağ, Çöpler), whereas continued subduction beneath the Makran in western Pakistan accounts for some of the only “normal” subduction-related porphyry deposits in the region (e.g., Saindak, Reko Diq). Few igneous rocks or mineral deposits associated with the Paleotethys ocean occur in Iran, although several Paleozoic ophiolite belts are preserved, and Early Cambrian Kiruna-type iron oxide-apatite deposits are found in the Bafq district of eastern Central Iran. Arc magmatism associated with Mesozoic subduction of the Neotethys ocean is widespread in the Sanandaj-Sirjan zone, but no porphyry or epithermal deposits of this age have been discovered to date, likely due to erosion down to batholithic levels. Arc magmatism shifted to the Urumieh-Dokhtar magmatic arc and the Lut block in the late Paleogene-early Neogene, and the first significant porphyry deposits formed in the Eocene and Oligocene. However, the main period of porphyry formation occurred later in the early to mid-Miocene, synchronous with terminal collision between the Afro-Arabian and Eurasian plates. Several large porphyry Cu (Sungun, Meiduk, and Sar Cheshmeh), as well as the porphyry-related Sari Gunay epithermal Au deposit, were formed at this time (~20–11 Ma) along the length of the orogen. Active subduction continues only beneath the Makran of southeastern Iran and western Pakistan, where the large Saindak (~22 Ma) and Reko Diq (13–10 Ma) porphyry deposits occur. Mineral exploration in Iran to date has been largely restricted to areas of outcrop, but the potential for extensions of known deposits, or “blind” discoveries below widespread Quaternary cover is considered to be high.

Abstract Tectonic, geologic, geochemical, geochronologic, and ore deposit data from the U.S. Geological Survey-led assessment of 26 porphyry belts identified in the central Tethys region of Turkey, the Caucasus, Iran, western Pakistan, and southern Afghanistan relate porphyry mineralization to the tectonomagmatic evolution of the region and associated subduction and postsubduction processes. However, uplift, erosion, subsidence, and burial of porphyry systems, as well as post-mineral deformation, also played an essential role in shaping the observed metallogenic patterns. We present a methodology that systematically evaluates the relationship between the level of erosion, the extent of cover, and the number of known porphyry occurrences in porphyry belts. Porphyry belts that exhibit coeval volcanic-to-plutonic rock aerial ratios between 33 and 66 and limited cover contain numerous identified porphyry occurrences. These belts are relatively well explored because porphyry systems are not eroded or buried. Porphyry belts with volcanic-to-plutonic ratios that are greater than 66, but are modestly covered, contain fewer identified porphyry occurrences. Current exploration in these belts is increasingly identifying porphyry systems under associated epithermal deposits. Porphyry belts that show volcanic-to-plutonic ratios that are greater than 66, but are extensively covered, contain few identified porphyry occurrences. These belts have not been extensively explored but have potential for discoveries under cover. Deformed porphyry belts exhibit variable volcanic-to-plutonic ratios that are typically below 33, but can be as high as 60. Commonly, these deformed belts are extensively covered. Exploration efforts for porphyry deposits in these variably exhumed belts have been limited. Exploration has resulted in the identification of 62.7 million tonnes (Mt) of copper, 2.0 Mt of molybdenum, and 4.200 t of gold in the 45 porphyry deposits contained in the 26 porphyry belts of the region: (1) 54.7 Mt of copper (87% of total), 1.74 Mt of molybdenum (87%), and 3,370 t of gold (80%) occur in the 25 deposits of the four porphyry belts that exhibit coeval volcanic-to-plutonic ratios between 33 and 66 and limited cover; (2) 5.44 Mt of copper (9%), 0.148 Mt of molybdenum (7%), and 581 t of gold (14%) are contained in the 11 deposits of the 11 porphyry belts that display volcanic-to-plutonic ratios greater than 66 and modest cover; (3) 2.08 Mt of copper (3%), 0.110 Mt of molybdenum (6%), and 244 t of gold (6%) occur in the seven deposits of the three porphyry belts that have volcanic-to-plutonic ratios that are greater than 66 and extensive cover; and (4) 0.388 Mt of copper (1%), 0.006 Mt of molybdenum (<<1%), and 6 t of gold (<<1%) are contained in the two deposits of the eight deformed and covered porphyry belts with variable but typically low volcanic-to-plutonic ratios. The central Tethys region is receiving considerable exploration attention. It hosts the Kadjaran (4.6 Mt Cu), Sungun (5.1 Mt Cu), Sar Cheshmeh (8.9 Mt Cu), and Reko Diq (23.0 Mt Cu) world-class porphyry deposits. Continued exploration for porphyry deposits in the region will likely lead to new discoveries in known porphyry belts, particularly under cover and below high- and intermediate-sulfidation epithermal systems.

Abstract A method is presented for integrating structural and alteration interpretations based on regional remote sensing magnetic and infrared spectral data. Integrated interpretations can provide insight about the controls that basement structural architecture exerts over porphyry mineralization. The method is illustrated by a study of the porphyry-endowed Kerman belt of Iran, for which structural interpretations of EMAG2 first vertical derivative magnetic data were refined using alteration lineaments interpreted from Landsat-8 infrared spectral data. This method makes use of regional linear alteration trends indicative of lithologic discontinuities to refine and to enhance the understanding of deep-seated structures interpreted from regional magnetic data. The integrated structural and alteration analysis of the Kerman belt of Iran highlights a first-order fault that is interpreted continuously at depth over approximately 500 km strike length and shows good spatial correlation with the location of most porphyry deposits and prospects. The analysis also allows for the visualization of a premineralization regional dilational zone that hosts the most prolific portion of the Kerman porphyry belt.