Major and trace elements and sulfur isotopes in two stages of sphalerite from the world-class Angouran Zn–Pb deposit, Iran: Implications for mineralization conditions and type

Abstract The Angouran deposit is the second-largest Zn–Pb deposit in Iran with 4.7 Mt sulfide ore (27.7% Zn, 2.4% Pb, and 110 g/t Ag) and 14.6 Mt nonsulfide ore (28.1% Zn, 4.4% Pb). Various models have been proposed to explain the genesis of sulfide ore in this deposit. Moreover, the mineralization type of its primary sulfide ores remains controversial. The major and trace element concentrations and sulfur isotopic composition of the two stages of sphalerite have been analyzed to constrain mineralization conditions and the genesis. The Angouran deposit, which contains discordant orebodies, is hosted in a Neoproterozoic/Cambrian schist-marble sequence. Two stages of sphalerite have been distinguished: early-stage (S1) red-brown sphalerite and late-stage (S2) honey-yellow sphalerite. Our result shows that, relative to the S2 sphalerite, the S1 sphalerite has higher contents of Fe, Mn, Co, Cu, Ag, Sn, Ga, Sb and In, but lower contents of As and Tl. Time-resolved depth profiles in these sphalerites determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses indicate that Fe, Cd, Co, Hg, Mn, Ge, and In are mainly present in solid solution and that Ag, Cu, Pb, As, Ni, Ga, Tl, Sb, and Sn are present in both solid solution and mineral inclusions. Correlation analyses reveal the occurrence of direct substitution mechanisms, such as Zn 2+  ↔ (Fe 2+ , Cd 2+ ) and 2Zn 2+  ↔ Ge 4+ +□ (vacancy) as well as coupled substitutions, such as 2Zn 2+  ↔ Cu +  + Ga 3+ , 2Zn 2+  ↔ (Cu + , Ag + ) + Sb 3+ , 3Zn 2+  ↔ Pb 2+  + Tl +  + As 3+ , 4Zn 2+  ↔ Pb 2+  + 2As 3+ +□(vacancy) or (Zn 2+ , Pb 2+ ) ↔ Tl +  + As 3+ , and 4Zn 2+  ↔ Cu +  + (Ga 3+ , In 3+ ) + Sn 4+ +□(vacancy). Geothermometer studies suggest that sphalerite in the Angouran deposit precipitated from a low-temperature ( 34 S V-CDT values of the S1 and S2 sphalerites, which range from 5.1‰ to 10.9‰, are atypical of magma-derived sulfur isotopic compositions. Therefore, the Angouran deposit was formed in a low-temperature (