Geochemical, microthermometric, and sulfur isotopic constraints on the origin of the Sarviyan iron deposit, Markazi Province, Iran

Abstract

The Sarviyan iron deposit is located 30 km northeast of Delijan city in Markazi Province, Iran. The iron ores occur dominantly as irregular masses and veins in a Middle-Late Eocene volcano-sedimentary sequence, adjacent to Eocene-Oligocene plutonic rocks. Magnetite is the main ore mineral accompanied by hematite, goethite, pyrite, and chalcopyrite. The gangue minerals include garnet, pyroxene, epidote, amphibole, phlogopite, chlorite, calcite, and quartz. Macroscopic and microscopic examinations show that the ore emplaced through replacing the host rocks. The concentrations of, and relationships among, trace elements deduced from LA-ICP-MS analysis in magnetite samples suggest a hydrothermal-skarn origin for the Sarviyan deposit. The sulfur isotopic composition of the pyrite samples (3.7–6.6‰) is slightly more positive than δ34SCDT values of magma-derived sulfur, indicating that the magmatic sulfur is negligibly contaminated with sulfur from sedimentary origin, or that sulfur sourced from magma with a crustal constituent. Fluid inclusion analyses in calcite samples reveal that ore-bearing solutions originated from a composite source including a relatively high temperature (135–380 °C) and salinity (29.10–42.97 wt% NaCl equivalent) magmatic fluid, and a second low to medium temperature (90–218 °C) and salinity (10.24–18.96 wt% NaCl equivalent) water, possibly of basinal/metamorphic source. It is proposed here that the iron mineralization at Sarviyan deposit is a skarn-type one.