پروین نجف زاده طهرانی

Neyzar iron deposit is located about 50 km southwest Mashhad, northeast Iran. It was developed as layered and discontinuous lenses in a fault zone within quartz-arenite and sub-litharenite sandstones of Lalun Formation (Lower Cambrian).  Mineralographical studies show that hematite is the principal iron ore mineral accompanied by goethite and lesser amounts of pyrite. Microscopic examinations confirm the presence of skeletal, relic replacement, marginal replacement, and pseudomorphic textures within the ores. Based on petrographical data, two series of alteration minerals, hypogene (sericite, pyrite, pyrophyllite, barite, chalcedony, and calcite) and supergene (goethite, jarosite, gypsum, limonite, and hematite) were developed in this deposit. Based on the results obtained from field works, mineralographical and geochemical studies, it appears that the evolution of the studied ores is genetically related to the host rocks.  Both hydrothermal processes and fault systems (existing in the host rocks) played important roles in leaching of elements and depositing of the ores. Results of chemical analyses show that the REE values vary in the iron ores from 6.97 to 18.26 ppm. Eu and Ce anomalies in the ores are within the ranges of 0.01-1.36 and 0.28-1.89, respectively. Geochemical considerations reveal that distribution of rare earth elements within Neyzar iron ores was controlled by pH, abundance of complex-forming ions (CO32-, F־, Cl־, PO43-, and SO42-), scavenging processes, and fixation in neomorph mineral phases.