Arc versus slab-failure magmatism in the Urumieh-Dokhtar Magmatic Arc and NW Iran: Implications for porphyry Cu-(Mo, Au) exploration

The Urumieh-Dokhtar Magmatic Arc and NW magmatism in Iran formed during Late Cretaceous to Quaternary opening and closure of the Neotethys ocean. Its prolonged magmatic history provides an opportunity to discriminate magmas linked to arc formation from those resulting from slab-failure and to investigate their relation to porphyry Cu-(Mo, Au) mineralization. Our data compilation shows that Late Cretaceous to Early Oligocene magmas are pre-collisional arc magmas, whereas those of Middle Oligocene to Quaternary age are the product of post-collisional slab-failure and thickening of arc crust. Magmas produced by slab-failure show adakite-like chemical characteristics with Nb/Y > 0.4, Sr/Y > 20, La/Yb > 10, Ta/Yb > 0.3, Gd/Yb > 2, and Sm/Yb > 2.5. Fertile and economic porphyry systems in the Urumieh-Dokhtar Magmatic Arc and NW Iran are typically related with these slab-failure magmas. Exploration for porphyry systems in this and other Cenozoic arcs in Iran therefore needs to focus on post-collisional intrusive suites showing such geochemical characteristics.