Mineralogy, and genesis of Khalyfehlou copper deposit based on host rock geochemical data and o-s isotope characteristics

Khalyfehlou Cu deposit (southeast of the Zanjan), is the volcanic-hosted vein-type deposit located in the Tarom metallogenic zon,Western Alborz (northwest of Iran) . Tarom zone consist mainly of volcanic and volcaniclastic rocks of the Karaj Formation (Early to Middle Eocone). Regarding the stratigraphic position, the Karaj Formation is divided into two members: Kordkand and Amand. The Kordkand member is overlain by the Amand member .The Amand member is divided into six units, Ea1 through Ea6. The Khalyfehlou Cu deposit is located in Ea5 and Ea6 units of Amand member .The Karaj Formation is interrupted by large and linear intrusions with calc alkaline affinities. Host rocks are green tuffs and, rarely, andesites. The patterns of rare earth elements in the studied samples indicate the negative anomaly of Eu element due to plagioclase subtraction. In all the samples, the enrichment of light rare earth elements (LREE) and large lithophil ion (LILE) elements and the depletion of strong field strength elements (HFSE) are observed. This probably indicates the common origin of these rocks. Main minerals include chalcopyrite, bornite, chalcocite, and covellite and gangue minerals including quartz, sericite, and calcite. In this paper the origin of ore-forming fluids and genesis of Khalyfehlou Cu deposit is studied using sulfur and oxygen isotope data. The sulfur isotope values for the chalcopyrite range from −2.0 to −5.3‰. Negative sulfur isotopes values and the occurrence of framboidal pyrite in the tuffaceous sandstone host rocks suggests a sedimentary origin for the sulfur. The oxygen isotope composition of quartz from the veins ranges from 12.3 to 14.3‰. The δ18Ofluid values calculated from the oxygen isotope data range from 0.6‰ to 3.6‰. The O isotopic characteristics indicate that the ore-forming fluids for the Khalyfehlou deposit was meteoric-formational water.This study suggests that mineralization at the Khalyfehlou deposit is similar to cordilleran vein-type deposits.