The Chah-Mesi epithermal Cu-Pb-Zn-(Ag-Au) deposit and its link to the Meiduk porphyry copper deposit, SE Iran: Evidence from sulfosalt chemistry and fluid inclusions

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Abstract

The polymetallic Chah-Mesi epithermal vein deposit is located about 2.5 km south of the Meiduk porphyry Cu-(Mo-Au) deposit in the Kerman Cenozoic Magmatic Arc (Kerman Belt), representing the southeastern sector of the Urumieh-Dokhtar Magmatic Belt in Iran. The veins are N-S to NNE-SSW oriented and hosted in volcanic rocks of basaltic, andesitic to dacitic composition and pyroclastics, which were affected by intense local silicification and sericitization in proximity to mineralized veins. Propylitic, argillic, as well as potassic alteration show a more regional distribution; the latter only observed closer to the Meiduk deposit. Mineralization occurs in various types of veins (massive, banded, crustiform) and to minor extent in replacement and breccia bodies. It encompasses several stages: An early higher-sulfidation stage, characterized by pyrite, chalcopyrite, enargite/luzonite and bornite, is followed by the main intermediate-sulfidation state assemblage with pyrite, chalcopyrite, tetrahedrite group minerals and sphalerite. The late Pb-Zn rich stage with sphalerite, galena, chalcopyrite and pyrite overprints the earlier associations. Gold and silver of up to 7 g/t and 150 g/t, respectively, are associated with the main and late stages of mineralization. The main carriers of these precious metals are Ag-rich gold (electrum) and tetrahedrite; other Ag-bearing sulfosalts like pearceite are rare. The chemical composition of tetrahedrite group minerals ranges from tennantite-(Fe) to tetrahedrite-(Fe) and tetrahedrite-(Zn) exhibiting a positive correlation between Sb and Ag contents. The tetrahedrite group minerals show complex zoning and display an increase of Sb away from the Meiduk deposit. Primary fluid inclusions in sphalerite and quartz from the banded and crustiform veins are low saline aqueous H2O-salt inclusions with only traces of CO2. Homogenization temperatures of two-phase LV inclusions (Th LV→L) have an average of 210 °C in sphalerite and 260 °C in quartz. Salinity values range from 1.2 to 9.9 and 2.1 to 9.2 mass% NaCl equivalent in sphalerite and quartz, respectively with an average of c. 6 mass% NaCl equiv. Low CO2 concentrations in the vapor phase detected by Raman spectroscopy together with previously published stable isotope data indicate fluids of magmatic origin as the main fluid source that were mixed with meteoric water. Mineralization is linked to ascending hydrothermal fluids which evolved from high- to intermediate-sulfidation state due to cooling, dilution with meteoric water and progressing fluid-wallrock interaction. Similar low salinity, but higher CO2-bearing fluids were previously reported from the nearby Meiduk porphyry deposit. Conclusively, Chah-Mesi is classified as an intermediate-sulfidation epithermal deposit that developed in the peripheral parts of the Meiduk porphyry system.
Original languageEnglish
Article number104732
Number of pages23
JournalOre geology reviews
Volume142.2022
Issue numberMarch
Early online date29 Jan 2022
DOIs
Publication statusPublished - Mar 2022

Bibliographical note

Funding Information:
We are grateful to Mohsen Rezai and Majid Tashi (Shahid Chamran University of Ahvaz) for their help during fieldwork, sampling and sample preparation and for providing data and sharing information on Iranian deposits. Werner Paar (Salzburg) is thanked for his help with ore microscopy. Sincere thanks to Maik Zimmermann and Federica Zaccarini (Montanuniversität Leoben) for their assistance with sample preparation and EPMA analysis. The Shahid Chamran University of Ahvaz is acknowledged for logistical and financial support of this project, which is part of an official cooperation with Montanuniversität Leoben. We sincerely thank Editor-in-Chief Huayong Chen (Guangzhou Institute of Geochemistry) for the editorial handling of the manuscript and David R. Lentz (University of New Brunswick), as well as two anonymous reviewers for their constructive reviews.

Publisher Copyright:
© 2022 The Author(s)

Keywords

  • Epithermal ore deposits
  • Fluid inclusions
  • Iran
  • Tetrahedrite group

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