Hydrothermal alteration in Eshtehard volcanoes, Iran: Constraints from trace elements redistribution and stable isotope geochemistry

We use the mineralogy, trace element compositions and elemental mass balance of volcanic materials collected from propylitic, potassic phyllic alteration facies in Eshtehard area Iran to document nature effects hydrothermal alteration. Incompatible abundances hydrothermally–altered samples show transformations that include: (i) depletion alkalis alkaline earth elements (i.e., Ba, Sr), (ii) variable behavior first series transition (depletion Cr, Co Ni; enrichment Zn Cu), (iii) HREE, Hf Th relative U LREE. In detail, (associated with a major addition Cu) zones are characterized by SiO2 MgO whereas propylitization depleted MnO, enriched Fe2O3, increased LOI. Whole rock geochemistry along revealed consistent negative Ce Eu anomalies, indicating reducing conditions persisted during processes. Substantial changes isovalent ratios K/Ba, K/Rb, Y/Ho, Sr/Eu, Zr/Hf Eu/Eu*) illustrate non–charge radius control construed as lanthanide tetrad–effect phenomena. The co–occurrence zigzag patterns M W–shapes) is evidence for partial or incomplete tetrad effect reaction between REE3+ F-and Cl-rich fluids systems. Low T4 values overall suggest rock–fluid interaction involving rather low temperature solutions. Mass (?M) volume (?V) were slightly propylitic (?3.80% ?5.66%) (?3.48% ?5.66%), (?2.52% ?2.91%) isocon slopes 1.06, 1.06 1.03, respectively. envisage secondary phenomenon open system which accompanied fluid–rock plausible cause slight REE observed hydrothermally altered samples. Fluid inclusions studies yield homogenization temperatures 275–596 °C salinity ranging 34 39 wt% NaCl equivalent suggesting boiling mineralization area. calculated ?18O ?D range 5.3 7.1 ?75 ?62 per mil, On this basis, we ore-forming had magmatic source underwent and/or exchange hydrous minerals.