One of the most important ores for REE mineralization are iron oxide–apatite (IOA) deposits. The Posht-e-Badam Block (PBB) is a part of the Central Iranian geostructural zone which is the host of most important Fe deposits of Iran. Exploration studies of the IOA deposits within the PBB (e.g. Esphordi, Gazestan, Zarigan, Lak-e-Siah, Sechahoun, Chahgaz, Mishdovan, Cheshmeh Firouzi and Shekarab) demonstrate that these deposits contain high contents of REE. Concentrations of ΣREE in the most important IOA deposits of the PBB include the following: the Esphordi deposit varies between 1.2 and 1.88%, the Gazestan deposit between 0.17 and 1.57%, the Zarigan deposit between 0.5 and 1.2% and the Lak-e-Siah deposit varies between 0.45 and 1.36%. Concentrations of ΣREE within the apatite crystals present within the IOA ores in the Esphordi, Lak-e-Siah and Homeijan deposits have ranges between 1.9–2.54%, 1.9–2.16% and of 2.55%, respectively. These elements are mainly concentrated in apatite crystals, but other minerals such as monazite, xenotime, bastnasite, urtite, alanite, thorite, parisite–synchysite and britholite have been recognized as hosts of REEs, as small inclusions within the apatite crystals, and in subsequent carbonate, hematite–carbonate and quartz veins and veinlets. Given the extent of this block and the presence of several IOA deposits within this block, and also the high grades of REEs within these deposits, one can reasonably state that it is obvious that there are significant resources of REEs in this part of Iran.
Authors:Mir Ali Asghar Mokhtari, H. Moinvaziri, M. R. Ghorbani, and M. Mehrpartou
The Kamtal Intrusion is located in Eastern Azarbaijan province, northwestern Iran, near the Armenian border. This body consists of an acidic part of monzogranitic composition, and an intermediate-basic part which is composed of quartz-monzonite and gabbro. The gabbro forms lenses within the intermediate rocks. Monzogranite has been intruded into the quartz-monzonite. Both monzogranites and quartz-monzonites are high-K calk-alkaline and metaluminous in composition and can be classified as I-type granitoids, while the gabbro has tholeiitic affinity.
Monzogranite and quartz-monzonite are characterized by LREE-rich patterns and high LREE/HREE ratios. The similarities of their REE patterns suggest a genetic relationship among these rocks. The geochemical characters of the gabbro types indicate two different patterns: a flat pattern with low LREE/HREE ratio, and a steep pattern with high LREE/HREE ratio. The former was probably produced by high melting ratio of a depleted mantle source, and the steep pattern probably was the result of a low melting ratio of this mantle source. Negative anomalies of Nb and Ti can be seen in all rock types of the Kamtal Intrusion, which is indicative of subduction zones. The comparison of trace element variations with granitoid rocks of different tectonic settings allows observing a similarity between the Kamtal Intrusion and Andean volcanic arc granitoids.
The Kamtal body is related to the VAG tectonic setting and was probably produced as a result of Khoy back-arc basin subduction beneath the Azerbaijan continental crust.