نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه زمینشناسی، واحد اهواز، دانشگاه آزاد اسلامی، اهواز، ایران
2 گروه زمینشناسی، دانشکده علوم زمین، دانشگاه شهید چمران اهواز، اهواز، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Baba-Ali and Galali deposits are located in 30 and 60 km northwest of Hamedan in northwest part of the Sanandaj-Sirjan zone. The host rocks of these deposits are metavolcano-sedimentary successions of Songhor series in Permo-Triassic age. Stratigraphic position of ore horizons, geometry of orebodies, ore structures and textures in different scales and paragenetic sequence of minerals all show close genetic relation between iron ore and the metavolcanosedimentary and subvolcanic rocks. The host rocks in the area are felsic to intermediate metavolcanic rocks, more than lava and rhyolitic tuffs with interculations of carbonate and metatuff-sandstones. Field observations and petrography show that emplacement of plutons and subvolcanic rock units with composition of gabbrodiorite, quartzmonzodiorite, granodiorite, syenite, syenogranite and granite in these successions caused deformation and metamorphism of ore and country rocks.
Materials and methods: In this research, 56 polished sections were prepared from iron ore of Baba Ali and Galali deposits, and the mineralogical characteristics and texture of the mineral in relation to gangue minerals were carefully studied using a reflected light mineralogical microscope. In order to determine the origin of ore-rich fluid, studies of fluid inclusions have been carried out on 6 double polished sections in the research laboratory of Tarbiat Modares University. Also, 29 samples of separated phases of sulphide, oxide-silicate and carbonate minerals from ore and gangue minerals of Baba Ali and Galali iron deposits have been analyzed for stable isotope analysis in Queen's University Isotope Research Laboratory in Canada.
Results and discussion: From field evidences, fluid inclusions data, as well as stable isotope analysis in this study, emplacement of plutons and subvolcanic rock units with composition of gabbrodiorite, quartzmonzodiorite, granodiorite, syenite, syenogranite and granite in these successions caused deformation and metamorphism of ore and country rocks. Fluid inclusion studies within the quartz crystals indicate that main salinity varies between 12±5 and 9±5 wt.% NaCl equivalent in Baba-Ali and Galali deposits respectively. Homogenization temperature for Baba-Ali and Galali deposits are 226±5 and 220±5 oC respectively. Occurrence of dynamothermal regional metamorphism in these deposits typically involves a lengthy period of time, during which there was a tendency toward isotopic homogenization specifically in O (3 to 10.5 ‰) and H (-10 to -35 ‰) stable isotopes and show the role of metamorphic waters in mineralization process. Measurement of δ34S (CDT) in first generation of pyrite is higher than another one, so these data confirm the volcano-sedimentary origin of primary iron mineralization.
Conclusion: Field observations, structure and texture, host rock, intercualation, geochemistry, alterations, studies of fluid inclusion and stable isotopes in Baba Ali and Galali deposits show that these deposits are volcanic-sedimentary iron deposits. Since most of these mineralizations are located in metamorphosed volcanic-sedimentary units, these rock groups are of great importance in terms of iron exploration. Investigating these stone units in the region and generalizing the evidence obtained from them to similar areas in Sanandaj-Sirjan zone can lead to the identification of this type of iron deposits.
کلیدواژهها [English]
)