Mineralogical and geochemistry of alteration zones in Qizilligh area-North Sarab (NW Iran)

The studied area is located in the northwest of Iran, East Azarbaijan province, and at a distance of about 30 km from the north of Sarab city. This area is part of the structural zone of Alborz. Based on petrographic and field studies, the lithology of the area includes an intrusive mass of quartz monzonite porphyry, the mass of granodiorite porphyry, dykes branching from the mass of granodiorite porphyry, and basalts. The main mineralogy includes plagioclase, quartz, potassium feldspar, clinopyroxene, biotite, and amphibole, alteration minerals in the studied rocks include sericite, chlorite, kaolinite, and iron oxides and often have porphyric, glomeroporphyric and Poikilitic texture. The most important variations include phyllic, argillic, and propylitic zones. Sulfide minerals observed in the area are mostly pyrite, chalcopyrite, sphalerite, and molybdenite, which have been converted into iron oxides and hydroxides (hematite) at some points. The mineralized texture is mainly scattered grains and veins. Examining the changes of rare earth elements and rare elements of porphyry masses shows positive anomalies of elements Li, Pb, Th, and U and negative anomalies of elements P, Zr, Ti, and Nb. A specific enrichment of LREE/HREE elements can be seen. The ratio of Eu/Eu* in altered samples is lower than that of healthy samples, and the ratio of Ce/Ce* is almost the same for healthy samples and most of the altered samples. In addition, the subtraction factors of (La/Yb)N, (La/Sm)N, and (Gd/Yb)N in altered samples are higher than in healthy samples. Light rare earth elements show an increasing trend and heavy rare earth elements have increased and decreased during the region's transformation process. The enrichment of U and Th elements is probably due to the prevailing acidic conditions and surface absorption by clay minerals and also due to the presence of zircon in the mineral network. Elements with high field strength show enrichment in most of the altered samples compared to the source rock, and only the Hf element shows depletion.