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Ms Zahra Yaftian, Dr Ata Shakeri, Dr Mehrdad Hadipourdeshal, Dr Meisam Rastegari Mehr,
Volume 9, Issue 2 (12-2023)
Abstract

Mining is a necessary activity for the development of countries, but it imposes direct and indirect negative impacts on the exploited areas and their surroundings. Sangan iron mine is one of the largest iron ore deposits in the Middle East, where the ore is extracted by open pit mining. The present study aims to investigate the soil’s concentration of heavy metals and to assess the level of soil’s contamination in the Sangan mining area. For these purposes, 44 samples of the soils (including both topsoils and subsoils) of the Sangan mining area were collected, and were analyzed by an ICP-MS device. The obtained data were analyzed by calculating the geochemical indices and statistical methods. On the basis of descriptive statistics of the analytical data, Pb with an average content of 138.39 mg/kg and Cd with an average concentration of 0.19 mg/kg had the highest and lowest concentrations in top soils, respectively. Moreover, Cr with an average value of 102.19 mg/kg, showed the highest, and Cd with an average of 0.2 mg/kg showed the lowest concentrations in subsoils. The average concentrations of As, Cr and Fe in the study area were higher than their respective values in the World-Soil Average composition. Among the elements, Pb had very high and severe enrichment in two stations with enrichment factor values of 149 and 23.85. The results indicated no severe soil pollution and ecological risk in the study area, except in some sampling sites. The most polluted soils were collected near the placer extraction units and tailing ponds of Ehya-Sepahan Company, as well as the waste rock pile of Sanabad Comprehensive Development Industrial and Mining Company.

Mr Hamed Ebrahimi Fard, Dr Majid Ghasemi Siani, Dr Behrouz Karimi Shahraki, Ms Fanoos Sharafi Nia,
Volume 10, Issue 2 (12-2024)
Abstract

The Sangan mining district, the largest Fe-skarn district in Iran, is located in the northeastern part of the Alborz magmatic arc. It comprises 14 deposits (1 Gt tons and a grade of 35-60% Fe), which have an east-west trend and are divided into three parts: eastern, central and western where the Tappeh Ghermez iron deposit (A') is located in the western part. The skarnification formed near the Sarnowsar syenogranitic intrusive body, and is composed of: 1) prograde endoskarn and exoskarn zones (clinopyroxene-garnet skarn subzone) and 2) retrograde exoskarn zone (amphibole skarn subzone). Thermometry of skarnification was carried out based on the chemistry of skarn silicate minerals and their agreement with the results of microthermometry studies of fluid inclusion carried out on garnet and calcite in order to determine the physicochemical conditions and temperature of skarnification in the Tappeh Ghermez deposit. Geothermometry of the garnet-clinopyroxene pair minerals, indicated temperatures of 302 to 442°C for the prograde skarn zone. Based on the geothermometry of the calcic amphiboles in the retrograde zone, formation temperatures of 206 to 333°C have been obtained. The results of the geothermometry of the prograde and retrograde skarn zones are consistent with the results of the microthermometry of the fluid inclusions. Andradite is stable at temperatures above 430°C, even under high sulfidation conditions. At temperatures below 430°C and a relatively high fugacity of sulfur (greater than 10-6), andradite altered into calcite, quartz and pyrite. As fS2 decreases (about 10-6), such fluids form the magnetite complex.  Itcan therefore be concluded that retrograde metasomatizing fluids in the Tappeh Ghermez iron skarn deposit have a sulfur fugacity of 10-6.5 and temperatures below 430°C.


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