S.J Moghaddasi
Abstract
Jeirud phosphate deposit is located about 45 km north of Tehran, in the central part of the Alborz geological-structural zone. This deposit is occurred in Jeirud Formation, which is one of the major hosts of phosphate deposits in Iran. Jeirud phosphate deposit is composed of several phosphatic sandstone ...
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Jeirud phosphate deposit is located about 45 km north of Tehran, in the central part of the Alborz geological-structural zone. This deposit is occurred in Jeirud Formation, which is one of the major hosts of phosphate deposits in Iran. Jeirud phosphate deposit is composed of several phosphatic sandstone (phosphorite) layers occurring in the laminated black shale unit of Jeirud Formation. Based on the petrographic studies, phosphatic layers of Jeirud formation have simple mineralogy. Phosphate mineralization mainly consists of apatite and quartz with subordinate calcite, dolomite, pyrite, iron oxides and clay minerals. Jeirud phosphate samples show similar REE patterns, total REE contents and element ratios, suggesting contribution of common processes in their formation. Average total REE contents of the Jeirud phosphate samples are much more than those in the average oceanic water. Normalized REE patterns of Jeirud phosphate samples show differentiation and enrichment in LREEs in comparison to HREEs. Ce anomaly was not distinguished in the deposit. Investigating chondrite normalized REE patterns of the Jeirud phosphates indicate their deposition under reducing conditions. Post Archean Average Shale (PAAS) normalized patterns of the Jeirud phosphates show a nearly convex pattern with moderate positive Eu anomaly, revealing an anoxic or (sulfate reducing) diagenetic environment for phosphate formation.
Seyed Javad Moghaddasi; Y. Negahban
Abstract
Robat Karim manganese deposit is located in 7 km northwest of Robat Karim (southwest of Teharan), within northeastern margin of Orumiyeh-dokhtar volcanic belt. Based on regional geology, the studied area is situated in the northern Saveh Eocene volcanic assemblage, composed of rhyolite, trachyte, andesite ...
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Robat Karim manganese deposit is located in 7 km northwest of Robat Karim (southwest of Teharan), within northeastern margin of Orumiyeh-dokhtar volcanic belt. Based on regional geology, the studied area is situated in the northern Saveh Eocene volcanic assemblage, composed of rhyolite, trachyte, andesite and basalt. Manganese mineralization is occurred as veins, in faults, joints and fractures that crosscut the volcanic rocks. According to mineralogical studies, the manganese ore of the studied area is composed of pyrolusite, psilomelane, ramsdelite and hollandite, as well as calcite and quartz. Intergrowths of manganese oxides and quartz (or calcite) associated with various open space filling textures support the epithermal origin of the ore forming fluids in this area. Geochemistry of major and trace elements in Robat Karim manganese ores, similarity of their chondrite normalized REE pattern with volcanic host rocks and other hydrothermal manganese deposits of the world, as well as negative Ce anomaly indicate a probable epithermal origin of the deposit. Ore forming fluids could be originated from meteoric and/or magmatic waters circulating through Eocene volcanic rocks, dissolve manganese and other metals and deposit them in fault planes and major fractures. High pressure of the ore forming fluid has caused the formation of brecciated trachyte.
