نویسندگان
گروه زمینشناسی، دانشکده علوم، دانشگاه زنجان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
The Qamishlou Cu occurrence is located 150 km southwest of Zanjan, and is part of the Central Iran zone. Mineralization occurs as a stratabound zone hosted in the top part of the lower Cretaceous basalt-andesitic basalt lava. The ore zone has an NW-SE trend with 70-80˚ to the southwest and is 200 m long, and 1.5 m thick. Hydrothermal alteration related to mineralization includes chlorite-carbonate alteration. Propylitic and zeolitic alteration, and silica-calcite alteration, respectively, are related to pre- and post-mineralization processes. Primary chalcocite and bornite accompanied by minor pyrite, and chalcopyrite, are ore minerals; calcite and chlorite along with rare quartz, and zeolite are gangue minerals. Secondary chalcocite, covellite, malachite, cuprite, and neotocite are supergene minerals. The ore minerals show disseminated, vein-veinlet, vug infill, replacement, and framboidal textures. Mineralization at Qamishlou can be divided into four stages include pre-ore stage, syn-ore stage, post-ore stage, and supergene. Pre-ore stage is related to the diagenesis and burial metamorphism processes in which disseminated framboidal pyrites, and zeolite (as filling the amygdales) are formed within host basalt-andesitic basalt lavas. Syn-ore stage is divided in two substages. Early-ore stage is characterized by primary chalcocite, and bornite with disseminated, vug infill, and framboidal (pseudomorph of the framboidal pyrite) textures, and primary chalcocite veinlets. Late-ore stage includes minor pyrite- and chalcopyrite-bearing calcite vein-veinlets. Post-ore stage is marked by barren late calcite, and quartz vein-veinlets. Supergene stage is characterized by weathering and formation of secondary minerals. Geochemical investigations of ore samples show strong positive correlation between Cu and sulfur (0.93), and weak negative correlation between Ag and sulfur (˗0.27). Features of the Qamishlou Cu occurrence are comparable with the Manto-type (Buena Esperanza subtype) deposits.
کلیدواژهها [English]
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