Geology and genesis of the Chomalu polymetallic deposit, NW Iran

The vein-type Chomalu polymetallic epithermal deposit, located in the Tarom-Hashtjin Metallogenic Province (THMP), western Alborz, formed two separate mineralized zones controlled by fault within andesite and olivine basalt host rocks. deposit occurs adjacent to Varmarziar quartz monzonite, monzodiorite, monzosyenite intrusions. Ore mineralization consists of three stages; (i) an early stage dominated gold-bearing breccia veins mainly consisting quartz, pyrite, arsenopyrite, chalcopyrite, minor magnetite bornite assemblages, (ii) a main stage, which is divided sub-stages I, II III. Sub-stage I Pb-Zn-Cu-Ag-rich mineral assemblages including galena, Fe-poor sphalerite, tetrahedrite, pyrite. only represented galena sphalerite. III defined Fe-Mn-Zn-Ca-Mg carbonate minerals. late supergene (iii) characterized malachite, covellite, chalcocite, cerussite, Fe-oxide hydroxides. Microthermometry primary fluid inclusion indicate homogenization temperatures (Th) 253° 305 °C salinities 3.5–4.82 wt% NaCl equivalent stage. indicates 200° 280 180° 235 with 2.18–4.96 0.53–2.90 for II, respectively. precipitation was possibly caused simultaneous dilution cooling hydrothermal fluids. may be classified as E-type intermediate sulfidation extensional back-arc regime.