Deposit-Type Characterization and Genetic Implications of the Albolaq Esfaryen Pb–Zn Mineralization, NE Iran

Abstract

The Albolaq Esfaryen deposite in Northeastern Iran represents a promising sediment-hosted Pb–Zn mineral system within Mesozoic carbonate sequences. Despite extensive exploration activities, the genetic classification of Pb–Zn mineralization in this area has remained debated. This study integrates field observations, ore petrography, mineragraphy, and alteration analysis to characterize the deposit type and clarify its genetic framework.

Pb–Zn mineralization is hosted by carbonate rocks and occurs as structurally controlled veins, veinlets, With mineralization locally developed within the host rocks along faults, fractures, and brecciated zones. The primary sulfide assemblage is dominated by sphalerite and galena with minor pyrite, supergene alteration has produced extensive secondary zinc and lead carbonates and iron oxides. Alteration patterns are characterized mainly by dolomitization, accompanied by silicification and late-stage calcitization, indicating multi-stage hydrothermal fluid evolution.

The strong structural control on ore distribution, dominance of carbonate host rocks, low abundance of iron sulfides, and widespread dolomitization collectively point to a Mississippi Valley–type (MVT) genetic affinity.

the Albolaq Esfarayen lead and zinc deposit is probably of the MVT type, and the source rocks are also shale units. The host rocks of Tirgan limestone and brines also play a complex role. According to previous work [1].comparing the Albolaq Esfarayen lead and zinc deposit with the MVT deposits of Central Alborz and Tabas Posht Badam, the Albolaq Esfarayen lead and zinc deposit can be considered compatible with the MVT deposits of Central Alborz (the deposits of northeast Shahmirzad and the Pichmatou deposit of northwest Shahroud). Also, SEM-EDS analysis of selected galena samples confirms the presence of silver, whereas ICP-OES data from 56 samples generally low Ag concentrations, with only two samples (~3.6%) reaching 13 ppm, suggesting localized and sporadic enrichment.

The relationships observed in Thin sections  indicate that the primary Pb–Zn sulfide system has undergone supergene processes involving oxidation, pseudomorphic replacement, phase transformations, and secondary metal enrichment.