Concentration–Number (C–N) fractal method has been used for determining and separating mineralization phases based on surface lithogeochemical Au, Ag, Cu, Pb, Zn, As and Sb data in the Zehabad epithermal deposit, NW Iran. Five mineralization phases are demonstrated by multifractal modeling for the mentioned elements correlating with geological studies. The extreme phase of Au mineralization is higher than 7.9 ppm, which is correlated with hematite deposition in silicic veins and veinlets, whereas Ag (˃79.43 ppm), Cu (˃15.85%), Pb (˃63.1%), Zn (˃11.2%) extreme phases are associated with the main stage sulfidation phases. The results show that Au, Cu, Pb, Zn and Ag have two different mineralization trends based on the multifractal nature in this area. These trends are presented based on oxidic and sulfidic mineralization. According to mineralogical studies, the main stages of mineralization include: 1) formation of chalcopyrite ± sphalerite in silicic veins in sulfidic trend; 2) deposition of native gold and specular hematite in silicic veins in response to boilling, in oxidic trend; 3) next phase of fluid penetration and replacing chalcopyrite by galena, sphalerite and tetrahedrite-tennantite in the sulfide veins, in sulfic trend. Neighbouring copper and silver are due to the formation of tetrahedrite-tennantite solid solution. The obtained results show a positive correlation between mineralization phases and the faults present at the deposit. Moreover, mineralization phases of these elements demonstrate a good correlation with silicification and silicic veins and veinlets. پرونده مقاله

The Tarom metallogenic belt of the Alborz magmatic belt in NW Iran is characterized by two alignments of intrusion in its northern and southern parts. The northern intrusion is younger than the southern one. Mineral chemistry investigations on the northern and southern intrusions characterize calc-alkaline magmatism. The northern intrusion consists mostly of quartz monzonite, and the southern intrusion comprises 1) gabbro - pyroxene quartz monzodiorite – quartz monzodiorite series and quartz syenite; 2) gabbro-diorite. Electron microprobe chemistries indicate that the northern plagioclases are An22 to An49 (oligoclase to labradorite). Plagioclases from the southern intrusion are An35 to An54 (andesine to labradorite) and gabbro-diorite plagioclases are An65 to An61 (labradorite). All pyroxenes correspond to the Quad (diopside, augite, and clinoenstatite) and crystallized at <2 to 5 kbar and H2O=10%. Formation temperatures of pyroxenes from the northern intrusion are in the range of 1100-1175°C. The northern feldspars show temperatures ~550°C. Formation temperatures for the clinopyroxene and feldspar from the southern intrusion are estimated at 1140-1185°C and 550-600°C, respectively. The Fe-rich biotite minerals from the northern intrusion suggest high oxygen fugacity magma. The northern and southern intrusions formed in an arc-related tectonic setting. The northern magma is sourced from the melting of a mixed mantle-crust in a subduction-related environment. The mineral composition of the northern intrusion implies magma fertility and porphyry mineralization which can be due to its high oxygen fugacity magma and lower crystallization pressure relative to those of the southern intrusion. پرونده مقاله