Carbonate-hosted Zn-Pb-Cu-Ba (-Ag) mineralization in the Mehdiabad deposit, Iran: new insights, new discoveries

Abstract

The Mehdiabad deposit in the Yazd-Anarak metallogenic belt (YAMB), central Iran, is the largest carbonate-hosted Zn-Pb-Ba-Cu (-Ag) deposit in the world, with a reserve of 630 Mt sulphide and non-sulphide ore. It was formed during the Early Cretaceous by the replacement of barite and hydrothermally dolomitized breccia bodies of the Taft and Abkuh formations. This deposit consists of different ore zones, including the feeder zone, massive ore (including sulphide-oxide parts), massive barite ore, and copper-rich sulphide-barite ore, formed in an extensional environment related to the Naein-Baft back-arc basin. The deposit is stratabound and comprises a wedge-shaped sulphide-barite orebody with complex replacement textures of sulphides and barite. The primary sulphide ore, including a copper-rich core (with a reserve of more than 50 Mt of copper ore), developed in a barite sheath and characterized by the replacement of barite and pyrite by an assemblage of chalcopyrite, bornite, sphalerite and galena. Several stages of barite and sulphide deposition in the Mehdiabad deposit are similar to those reported in other Irish-type and barite-replacement sediment-hosted Zn-Pb deposits worldwide (e.g., Red Dog deposit, Alaska, USA).