<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>&#948;<sup>34</sup>S values in primary chalcocites (-7.7<em>&#8240;</em>-9.3<em>&#8240;</em>) and the &#948;<sup>34</sup>S <sub>H2S </sub>(-3.5<em>&#8240;-5.2&#8240;</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 &#177; 0.22 my for this unit. Also, based on the study of zircons, the average age of the pyroxene hornblende monzodiorite is 2.44 &#177; 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>&#160;</p>
<p>Diz alteration area is situated in the southern part of Ardabil province in the northwest of Iran. This alteration area is a limited part of Tarom-Hashtjin volcanic zone. The hydrothermal alteration process has been mostly taken place in pyroclastic and volcanic units such as tuff, ignimbrite, and trachyandesites. The alterations of this area are related to Eocene volcanism which has considerably developed in the northwest of Iran. The argillic alterations in Diz area are mainly seen in ignimbrite unit and the precursor rock has been intensely altered such that many parts of the parent rock has been fully leached and all of the mobile elements have been removed from the parent rock while the resistant elements such as Al, Si, and some other immobile elements have remained in the context. Considering to the special behavior of REEs in the weathering and alteration profiles, depending on the REE bearing mineral&#8217;s resistivity against weathering and alteration processes, REEs can be removed or fixed in the environment. In the studied samples different concentrations of REEs are observable.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; &#160;</p><p>The drawn REE diagrams show unique patterns for the studied samples where Ce group elements (LREEs) show a slight enrichment comparing to Y group (HREEs). The comparison of LREEs with HREEs represents that LREEs have been enriched 4 times more than HREEs.</p><p>The positive correlation coefficient between &#931;REE and TiO<sub>2 </sub>(R<sup>2</sup>=0.70) represents the role of Ti bearing minerals such as ilmenite, pyroxene, rutile, and anatase in the fixation of REEs. On the other side the presence of considerable amounts of P<sub>2</sub>O<sub>5 </sub>in the studied samples and also the positive correlation coefficients between P<sub>2</sub>O<sub>5 </sub>and LREEs (R<sup>2</sup>=0.90), and P<sub>2</sub>O<sub>5</sub> and &#931;REE (R<sup>2</sup>=0.74) suggest that some minor minerals such as monazite (Ce,La,Nd,Th)(PO<sub>4</sub>,SiO<sub>4</sub>) must be considered. The positive correlation coefficient between Al<sub>2</sub>O<sub>3 </sub>and &#931;REE shows the influence of clay minerals in the adsorption of REEs.&#160;&#160;&#160;&#160;&#160;&#160;&#160; &#160;</p><p>The evaluation of REE patterns normalized to chondrite show a remarkable peak for Gd. Geochemically, Gd shows similarities with Ca<sup>2+</sup>. The Gd complexes may decompose in the presence of some elements such as Cu, Y, and REEs and Gd<sup>3+ &#173;&#173;</sup>can be released. Hence, CaO is a main component in the parent rock of the studied altered samples, the positive Gd anomaly is most likely related to the primary composition of the parent rock. Furthermore, the decomposition of Gd complexes in the presence of competitor elements and also the high Gd content of altering fluids can be thought as the main reasons of Gd positive anomaly in the studied samples.</p>
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