s. h. mojtahedzadeh

Radar interferometry technique is an efficient tool to study changes in the Earth's crust. The method is based on the phase difference between two image pairs at different time intervals. In this research, subsidence of Abarkuh plain, Yazd province investigated. The subsidence is actually the lowering of the Earth's surface due to the natural and human activities. Excessive extraction of underground resources, especially water, is a main cause of subsidence in many plains in Iran. Hydrological studies in this area show a groundwater level drop of 0.6 meters per year. According to the geological studies, karst developments and dispersive clay soils are two causes of subsidence. By the radar interferometry technique over a period of 2003 to 2005 using 12 Envisat satellite images, the average subsidence rate in the region was estimated. In Abarkouh, maximum subsidence rate is 2 to 3 cm/year and in Mehrdasht area 5 cm/year. Accurate alignment studies have been used for the accuracy of the calculations between 1985 and 2001, which are in agreement with the results obtained by radar interferometry. The reasons for this discrepancy are the inconsistency between two available data and the radar interferometry error.

Bafgh Mishdovan ore body is located in the Central Iranian zone and is recognized as potential of the sillimanite group minerals. In this region, the outcrops of the different formations can be observed which mainly consist of the Precambrian metamorphic rocks. Silimanite group minerals are existed in the schistic rocks. The area is located in a tectonized zone and subjected to regional metamorphism then intruded by igneous plutonic rocks. The study area has 95 km2 coverage and according to quality and grade of sillimanite group minerals can be divided to four different mineral zones. Primary exploration activities have been carried out by digging of the trenches and test pits. Samples were taken systematically from outcrops, trenches and test pits. In order to recognize of the ore body (via mineralogy studies), some samples were sent to the laboratory for thin section studies and also XRD and XRF analysis. Based on these investigations, it is verified that the refractory minerals are consisted of sillimanite and kyanite and rarely andalusite. Based on the hosted rocks type and their metamorphic stages, thin section studies and XRD analysis, the phase transition of the primary andalusite into sillimanite and kyanite due to the high temperature-contact metamorphism can be justified. Also regarding the XRD analysis, only one sample contains some kyanites, so it seems that ore bodies is low grade and beneficiation of this industrial minerals face many difficulties or may not be feasible.