Mineralogical and isotopic studies in the Gol-Cheshmeh copper deposit, NE Iran

Abstract

<p>The studied area is situated as a narrow strip NE Iran and belongs to Central Iran structural zone and also the Kavir-Sabzevar magmatic zone which is related to <em>continental arc subduction zone of NE Iran. The mineralization is hosted in Eocene andesite-basalt, trachyandesite, andesite, and monzodiorite with high potassic shoshonite affinities that have undergone propylitic alteration. The </em><em>disseminated copper oxide and sulfide mineralization occurs in the form of stratabound, vein-veinlet and open space filling</em><em>,</em><em> </em><em>resulted from replacement of volcanic units simultaneously with sericitization and silicification of the host rocks. Two stages of mineralization have been recognized, namely a hydrothermal stage and supergene enrichment stage. Chalcocite, covellite, chalcopyrite, bornite, digenite, and tetrahedrite are the main hypogene minerals, that were altered during the supergene enrichment into bornite, secondary chalcocite, and Cu-carbonates. The range of </em>δ<sup>34</sup>S values in primary chalcocites (-7.7<em>‰</em>-9.3<em>‰</em>) and the δ<sup>34</sup>S <sub>H2S </sub>(-3.5<em>‰-5.2‰</em>) indicate that the source of sulfur in ore forming fluids was most likely sedimentary. The hypogene ore minerals are enriched in Ag, As, Ba, Sr, Fe, Mn, Zn, and Ce compared to their supergene counterparts. The enrichment of Cu took place during the supergene stage. The study of hornblende pyroxene olivine andesite basaltic zircons, show the average age of 5.47 ± 0.22 my for this unit. Also, based on the study of zircons, the average age of the pyroxene hornblende monzodiorite is 2.44 ± 0.79 my.</p> <p><strong>Key words: </strong><em>Gol-Cheshmeh; </em><em>Manto-type; Cu mineralization; sulfur isotopes; Nd-Sr isotopes; NE Iran.</em></p> <p> </p>