S Afzali; N Nezafati; M Ghaderi
Abstract
The Gazestan magnetite–apatite deposit is located 78 km east of Bafq, in the Bafq-Poshtebadam subzone of the Central Iran structural zone. The rock units in the area belong to the Rizou series and consist of carbonate rocks, shale, tuff, sandstone and volcanic rocks. Intrusive rocks in the form ...
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The Gazestan magnetite–apatite deposit is located 78 km east of Bafq, in the Bafq-Poshtebadam subzone of the Central Iran structural zone. The rock units in the area belong to the Rizou series and consist of carbonate rocks, shale, tuff, sandstone and volcanic rocks. Intrusive rocks in the form of stock and dyke crop out as granodiorite and granite in various places. Trachytic and dacitic rocks in the area are green due to chloritic alteration and host iron and phosphate mineralization. The main alteration types are chloritic and argillic, while sericitic, potassic, and silicic alterations as well as tourmalinization and epidotization are also found in the rock units. Five forms of mineralization are distinguished in the Gazestan deposit, including massive iron ore with minor apatite, apatite-magnetite ore, irregular vein-veinlets (stockwork) in the brecciated green rock and disseminated and monomineralic massive apatite veins. Fluid inclusion studies were conducted on the apatites of two stages. According to these studies, temperature and salinity values in the stage-I apatite are higher than those in stage-II apatite. Lower salinity values in the stage-II apatite could be due to contamination of magmatic fluids with meteoric waters during later stages of mineralization. Oxygen, hydrogen and carbon stable isotope composition of magnetite, quartz, apatite and calcite; and calculation of oxygen isotope composition in the fluid equilibrated with the oxide minerals suggest mixing the magmatic fluids with basin brines in mineralization of the Gazestan deposit.
S Afzali; N Nezafati; M Ghaderi; J Ghalamghash; M.R Ghassemi; A Karimi Bavandpur
Abstract
The Gazestan magnetite–apatite deposit is situated 78 km east of Bafq. The Gazestan deposit is located in Bafq-Poshtebadam subzone of Central Iran structural zone. The rock units in the area belong to the Rizu series and consist of carbonate rocks, shale, tuff, sandstone and volcanics. In addition ...
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The Gazestan magnetite–apatite deposit is situated 78 km east of Bafq. The Gazestan deposit is located in Bafq-Poshtebadam subzone of Central Iran structural zone. The rock units in the area belong to the Rizu series and consist of carbonate rocks, shale, tuff, sandstone and volcanics. In addition to sedimentary and volcanic rocks, intrusive rocks in the form of stock and dyke outcrop as diorite gabbro, gabbro, diabase, quartz-monzonite and granite in various places. The green rocks with acidic to intermediate composition (trachyte and dacite demonstrate green color due to alteration) host iron and phosphate mineralization which in some localities, show subvolcanic facies. The alteration is more obvious in the volcanic rocks and includes chloritization, argillic, silicification, and also formation of mafic minerals such as epidote, tremolite and actinolite. The host rocks are strongly altered. Mineralization at the Gazestan deposit comprises a combination of iron oxides and apatite with various ratios accompanied by quartz and calcite, observed in different forms mainly within the trachytic-dacitic rocks and a small proportion in the rhyolites. Five forms of mineralization are distinguished in the area including massive iron ore with minor apatite, apatite-magnetite ore, irregular vein-veinlets (stockwork) in the brecciated green rocks, disseminated, and pure massive apatite veins. The host rocks in the Gazestan area plot on calc-alkaline field. Comparison of the most important characteristics of the Gazestan deposit (including tectonic setting, host rock, mineralogy, alteration, structure and texture) with those of various types of mineralization in the world suggest that the deposit is quite similar to the iron oxide - apatite deposits.
