عنوان مقاله [English]
IntroductionThe northern Kabudan ore mineralization has occurred in part of the Taknar structural zone in NE Iran and part of the Central Iranian structural zone (Stocklin, 1968; Berberian and King, 1981). The Taknar zone has been known for mainly acidic submarine volcanoes (Malekzadeh Shafaroudi, 2003; Karimpour et al., 2003) and the north Kabudan mineralization has been introduced as volcanogenic massive sulfide ore deposit (Heidarpour, 2012). In this research, mineralogy, mineral chemistry and geochemistry of ore deposits have been studied. Kabudan Fe ore mineralization district with average grade of about 45 wt. % is located in part of the Taknar volcano-sedimentary Formation (micashist units, dacitic-rhyolitic volcanic units and a complex of granite-granodiorite-metadiabase to metagabbro-dioritic intrusive bodies). Magnetite mineral chemistry in Fe ore deposits can be used on genesis of ore mineralization.Analytical methodsA total of ninety microscopic sections were prepared from ore, geological units and alteration zones and studied at the Iranian Mineral Processing Research Center, using Axiplan 2 Zeiss microscope. For mineral chemistry, selected polished sections were studied by SEM (SEM 1450 VP) and EPMA (CAMECA X 100) electron microscopes at the Iranian Mineral Processing Research Center. In order to identify the mineralogical phases at the alteration zones, eighteen samples were studied by X-ray diffraction (XRD) method at Mashhad Geological Survey and Iranian Mineral Processing Research Center. For geochemical studies of ore, about 31 rock samples were taken from the ore mineralization zones and analyzed at the Geological Survey of Iran.Results and discussionOre mineralization had occurred as hypogene and supergene polymetallic (iron-lead-zinc-copper). Mineralization was seen at the specific horizons of Taknar Formation (sericite schist and chlorite schist) and metavolcanics associated with the Teknar Formation, as layered, massive and stockwork textures. Paragenetic sequences in layered and massive zones are: magnetite±hematite, pyrite, chalcopyrite, shpalerite and galena. Magnetite is the main and abound mineral in the massive zone. Pyrite, chalcopyrite and minor magnetite are main minerals in stockwork zone. Malachite and Fe-oxy-hydroxide associated with cerussite are formed as fracture filling and supergene zones. Electron microprobe results of magnetite show that the MgO contents are ranging from 0 to 0.77 wt. %, Al2O3 contents are ranging from 0.01 to 2.55 wt. %, TiO2 contents are ranging from 0.06 to 0.06 wt. %, V2O5 contents are ranging from 0.06 to 0.06 wt. %, FeO contents are ranging from 20.01 to 30.60 wt. % and finally Fe2O3 contents are ranging from 69.21 to 80.31 wt. %. Based on the results of the magnetite chemistry on geochemical diagrams by Dupuis and Beaudoin (2011), Kabudan-Bardaskan ore mineralization is classified as iron-rich volcanogenic massive sulfide. Geochemistry of ore indicate that Pb-Zn, Sb with As, Au and Fe and Zn-Mn pair elements have highest correlation coefficients and Cu-Mn and Bi with Sb- Fe and Ag have low correlation coefficients, which have been confirmed by microscopic studies.ConclusionStructurally, north Kabudan polymetallic ore mineralization (iron and base metals), is part of polymetallic Taknar zone in which iron, copper, lead and zinc mineralization occur as three forms: layered, massive and stockwork in the several different outcrops. The stockwork ore mineralization mainly consists of pyrite and chalcopyrite. Layered ore mineralization consists of magnetite, hematite associated with chlorite, carbonate and quartz as gangue minerals. The massive ore mineralization consists of magnetite, hematite, quartz, chlorite and quartz. Mineralization in Kabudan district is introduced as volcanogenic massive sulfide ore deposit due to presence of stockwork texture at lower depth and the layered and massive in the upper part, the existence of chlorite-sericite-carbonate alteration, simple mineralogy including chalcopyrite, pyrite, magnetite, galena and sphalerite and the presence of felsic volcanic rocks and basic metamorphosed subvolcanic and magnetite chemistry data. Considering differences with Kuroko, Besshi and Cyprus volcanic-hosted massive sulfide types, these facts indicate that ore mineralization in north of Kabudan can be classified as magnetite-rich massive sulfide ore deposits alike Balcooma, Gossan Hill and Noranda ore districts (Abitibi, Canada) (Morton, 1987; Huston et. al., 1992; Large, 1992; Huston, 2002; Sharpe and Gemmell, 2002).