Recycling of orogenic arc crust triggers porphyry Cu mineralization in Kerman Cenozoic arc rocks,southeastern Iran

Pre-collisional Eocene–Oligocene arc diorites, quartzdiorites, granodiorites, and volcanic equivalents in the Kerman arc segment in central Iran lack porphyry Cu mineralization and ore deposits, whereas collisional middle-late Miocene adakite-like porphyritic granodiorites without volcanic equivalents host some of the world’s largest Cu ore deposits. Petrological and structural constraints suggest a direct link between orogenic arc crust evolution and the presence of a fertile metallogenic environment. Ore-hosting Kuh Panj porphyry intrusions exhibit high Sr (>400 ppm), low Y (<12 ppm) contents, significant REE fractionation (La/Yb > 20), no negative Eu anomalies (Eu/Eu^* ≥ 1), and relatively non-radiogenic Sr isotope signatures (⁸⁷Sr/⁸⁶Sr = 0.7042–0.7047), relative to Eocene–Oligocene granitoids (mainly Sr < 400 ppm; Y > 12; La/Yb < 15; Eu/Eu^* < 1; ⁸⁷Sr/⁸⁶Sr = 0.7053–0.7068). Trace element modeling indicates peridotite melting for the barren Eocene–Oligocene intrusions and a hydrous garnet-bearing amphibolite source for middle-late Miocene ore-hosting intrusions. The presence of garnet implies collisional arc crustal thickening by shortening and basaltic underplating from about 30–35 to 40–45 km or 12 kbar. The changes in residual mineralogy in the source of Eocene to Miocene rocks in the Kerman arc segment reflect probing of a thickening arc crust by recycling melting of the arc crustal keel. Underplating of Cu and sulfur-rich melts from fertile peridotite generated a fertile metallogenic reservoir at or near the crust–mantle boundary, and dehydration melting under oxidizing conditions produced syn- and post-collisional ore-hosting intrusions, while the lack of post-collisional volcanism prevented the venting of volatiles to the atmosphere from sulfur-rich and oxidized adakitic magmas. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.