Relationship between dolomitization alteration and mineralization in Ahangaran epigenetic deposit (southeast of Malayer): mineralogy, geochemistry and mineral chemistry evidences

The Malayer–Esfahan metallogenic province in the Sanandaj-Sirjan zone hosted several various deposit and occurrences, which occurred in the Lower Cretaceous carbonated rocks at the point of metallogenic view. The Ahangaran Pb-Fe±Ag deposit (southeast Malayer) as the main deposit of this province, occurs mainly within Lower Cretaceous limestone, dolomitic limestone, dolomite and sandstone hosts. The main oldest rocks in the area composed of schist, slate, quartzite, and shale belong to Jurassic which overlaid on Triassic rocks due to disconformity. Mineralization with dolomitic alteration occurred as two types of ores including sulfide (Pb±Ag vein-type) and oxide (Fe-leached cap) ores. Petrographical and mineral chemical studies show at least three types of dolomites in fine crystalline carbonate host rocks of sulfide and oxide ore bodies, including fine-grained (RD1), medium-grained (RD2), and coarse-grained dolomites with zoning (RD3). RD1– and RD2–dolomites mainly occur in sulfide ore and RD3 dolomites occur in oxide ore. The composition of RD2 dolomites indicated high value of Fe (13.5 wt% in average), Pb (80 ppm in average), and Mn (1600 ppm in average), relative to RD1 dolomites. Formation of RD2 dolomites from ore-forming fluid is supported by evidences such as, high content of Pb (100 ppm) in RD2 dolomites, high correlation index between Pb and other Ca (R=0.57), Fe (R=0.60), and Sr (R=0.78) elements and adjacency of these dolomites to ore-bearing Pb veins, has been progress eventuality formation of RD2 dolomites from ore-forming fluid composition.