Active tectonics and late Cenozoic strain distribution in central and eastern Iran

Right-lateral shear between central Iran and Afghanistan is accommodated on N-S right-lateral strike-slip faults surrounding the aseismic Dasht-e-Lut. North of ∼3°N, the right-lateral shear is accommodated on left-lateral faults that rotate clockwise about vertical axes. Little is known of the late Tertiary and younger offsets and slip rates on the active fault systems, results that are important for understanding the regional tectonics. We use observations from satellite imagery to identify displaced geological and geomorphological markers which we use in conjunction with the overall morphology and orientation of the active fault systems to estimate the total cumulative right-lateral shear. Estimates of cumulative fault movements from offset features and inferred vertical axis rotation of fault-bounded blocks suggest that the late Cenozoic strain is concentrated toward the eastern margin of Iran, along the Sistan shear zone, where bedrock offsets of at least 70 km are observed across the active faults. The geomorphology of the Deh Shir, Anar, and Great Kavir strike-slip faults in central Iran suggest that although little shortening is accommodated across this region, they might still be active, and hence capable of producing earthquakes. Present-day activity on these faults in central Iran would not be expected from distributions of instrumental and historical earthquakes. Although speculative, the late Tertiary strain distribution described in this paper is consistent with what we know of the present-day rates of shear in eastern Iran and provides a framework to which later, more detailed, work can be added. Copyright 2004 by the American Geophysical Union

Assessment of chemical and mineralogical characteristics of airborne dust in the Sistan region, Iran

Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. Sistan is a region located in southeast Iran with extensive wind erosion, severe desertification and intense dust storms, which cause adverse effects in regional air quality and human health. To mitigate the impact of these phenomena, it is vital to ascertain the physical and chemical characteristics of airborne and soil dust. This paper examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol samples at two stations established close to a dry-bed lake dust source region, from August 2009 to August 2010. Furthermore, soil samples were collected from topsoil (0–5 cm depth) at several locations in the dry-bed Hamoun lakes and downwind areas. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. X-ray Diffraction (XRD) analysis of airborne and soil dust samples shows that the dust mineralogy is dominated mainly by quartz (30–40%), calcite (18–23%), muscovite (10–17%), plagioclase (9–12%), chlorite ( 6%) and enstatite ( 3%), with minor components of dolomite, microcline, halite and gypsum. X-ray Fluorescence (XRF) analyses of all the samples indicate that the most important oxide compositions of the airborne and soil dust are SiO2, CaO, Al2O3, Na2O, MgO and Fe2O3, exhibiting similar percentages for both stations and soil samples. Estimates of Enrichment Factors (EFs) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes lying to the north of Sistan.http://www.elsevier.com/locate/chemospherehb201