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The Angouran mine in northwestern Iran is a very high grade zinc ore deposit with some 18.2 Mt of nonsulphide ore (28.1% Zn, 4.2% Pb, 110 g/t Ag) and an additional 4 Mt of sulphide ore (40.4% Zn, 1.9% Pb).

The deposit is hosted by metamorphic basement rocks of the Sanandaj-Sirjan microplate of the Zagros Orogenic Belt (Neo-Tethys) that have been affected by the Tertiary to Quaternary volcanic and geothermal activity of the Urumieh-Dokhtar volcanic arc.

The ore body that occurs at the boundary between footwall schists and hangingwall marbles consists of a layer of sulphide ore at depth directly overlain by the mixed sulphide-nonsuphide ore, and capped by smithsonite-rich nonsulphide ore. The extremely rich sphalerite ore contains only subordinate amounts of galena with minor pyrite and arsenopyrite. The nonsulphide zinc ore (smithsonite) has been formed (1) in paragenetic association with the sulphide ore, and (2) by supergene in-situ oxidation of the sphalerite ore.

The fixation of the mobilised zinc as smithsonite was promoted by the buffering action of (CO3)(2-) that was delivered from dissolution of the calcite in the hanging wall. Minor amounts of other oxides including Fe-(Pb)-oxyhydroxide complexes, mimetite, and hemimorphite are associated with type (2) smithsonite. Large amounts of clay minerals were formed also in the footwall schists due to the disintegration of aluminosilicates. A high-purity zinc carbonate ore, containing hydrozincite, formed at shallower levels of the hangingwall marble due to lower fCO(2).

The supergene oxide ore system has undergone only weak metal fractionation, and the major constraint on the formation of high-grade Zn-carbonate ore wer primarily the presence of an extremely zinc-rich sulphide protore and carbonate rocks in the hangingwall. The geotectonic setting within the overriding plate of the active convergent plate of Iran provided long term uplift, erosion, rapid exhumation of the sulphide protore, and exposition to oxygenated surface waters. Arid paleoclimatic conditions prevented the nonsulphide solutions from being flushed out of the system. Oxidation processes may have been additionally promoted by a regional high heat flow due to the young geothermal activities. An earlier smithsonite generation was probably formed by mixing of the CO2-rich meteoric waters with the hydrothermal fluids. The genesis of this type is still ambiguous, and clarifications are expected from the results of current stable isotope studies.