Stable isotope, fluid inclusion, and petrological-mineralogical features of epithermal deposits in the structural zones of Iran: A review

Abstract

The structural zones of Iran and their various subtypes of epithermal deposits are: Urumieh-Dokhtar (LS-IS-HS), Arasbaran (LS-IS-HS), Alborz [Tarom (LS-IS-HS), Torud-Chah Shirin (LS-IS-HS), Binalood (LS) subzones], Sabzevar-Taknar (LS), Sanandaj-Sirjan (IS-HS), Makran (LS), Lut (LS-IS-HS), and Central Iran (LS-IS). One hundred and sixteen epithermal deposits in Iran are reviewed in this article. There are two or three subtypes in all zones except Sabzevar-Taknar and Makran. The majority of the host rocks consist of Eocene-Oligocene volcanic, pyroclastic, and intrusive rocks with calc-alkaline, high-K calc-alkaline, and shoshonitic affinities in the continental magmatic arc in a subduction zone. The Central Iran host rocks are the most different. Based on isotope studies, the O and H sources are mostly magmatic and then meteoric water, but in some LS deposits, formation waters played a role. In the LS deposits, C sources are magmatic, meteoric, marine carbonate, and sedimentary. Sulfur sources are mostly magmatic, but sedimentary, volcanic-sedimentary series, igneous, marine evaporate sulfate, evaporate, and sedimentary-metamorphic basement. In the IS deposits, S sources are sedimentary, igneous, magmatic, and volcanic H₂S. In the HS deposits, S sources are sedimentary, volcanic-sedimentary series, igneous, magmatic, magmatic vapors, and volcanic H₂S. There are L + V, L₁ + L₂ + V, V + L, L, V, L + V + S, and L + V + CO₂ fluid inclusion types, and precipitation mechanisms in order of importance are boiling, mixing, cooling, and dilution. Makran and then Sabzevar-Taknar deposits exhibit the lowest temperature and salinity. According to all the pieces of evidence, the structural setting of the zones determines the characteristics of the deposits, like host rocks, ore-bearing fluid conditions, ore mineral assemblage, alteration, S, O, H, and C sources, and finally, deposit subtypes. In some deposits, shreds of evidence like higher fluid inclusion maximum homogenization temperature, and salinity relative to epithermal range, potassic alteration (biotite-rich), and adakite magma affinity indicate that other types of mineralization (probably porphyry) are associated.