Origin of the Kaviro lead deposit in the Neyganan area, Lut Block, Eastern Iran: Constraints from geology, fluid inclusions, and isotope geochemistry

Abstract

The Kaviro lead deposit is located in the Lut Block, which is an important metallogenic province in Eastern Iran (lat 34°22'N, long 57°18'E). The deposit includes ore-bearing veins and veinlets emplaced in folds and hosted by middle Jurassic slate units. The ore-forming procedure can be segregated into three stages: pre-mineralization stage quartz-pyrite, main stage quartz-dolomitepyrite-galena, and late stage calcite and pyrite. Hydrothermal alteration minerals are composed of dolomite, quartz, and calcite. Microscopic surveys show that the vein includes galena with minor amounts of pyrite as hypogene minerals. Two types of fluid inclusions are distinguished in quartz and dolomite veins. Microthermometric investigations reveal homogenization temperatures of 180-250 °C and salinities from 5 to 12.5 wt.% NaCl equivalents. The oreforming fluids of the Kaviro deposit are medium-to-low in terms of temperature and salinity. The δ 34S values for the ore fluid are estimated to be between +0.94‰ and +3.27‰. The isotopic compositions of sulfur suggest that the ore-forming aqueous solutions are derived from a nonmagmatic source, probably from leaching of metamorphic rocks. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of the samples span narrow ranges from 18.514-18.569, 15.668-15.715, and 38.803-38.950, respectively. The 207Pb/204Pb and 208Pb/204Pb ratios plot above the evolution curves and clearly indicate a crustal source. The 207Pb/204Pb vs. 206Pb/204Pb data suggest a homogen source for Pb. Most of the galena samples in the CIM Pb-Zn deposits show high 207Pb/204Pb ratios, indicating that Pb is mainly derived from continental crust or pelagic sediment. The age of the mineralization is after the middle Jurassic. The Kaviro deposit is a metamorphic-related vein deposit, and fluid mixing is the important mechanism for its deposition.