The study of geochemical behavior of rare earth elements in apatites from the Hormoz Island, Persian Gulf

The study area is located about 3 km southwest of the Hormoz Island in the Hormozgan province، in the Persian Gulf. The main rock units in the region consist of a highly altered acidic pluton cratophyre، which is responsible for apatite formation، diabasic dike، marl and altered basalt. Apatite is the only phosphate mineral in the Hormoz Island، which has accumulated REE in its crystal structure. The amount of Na2O and SiO2 oxides in apatite are high and the average content of the main elements Fe، Mg، Al، Ca are 7. 5 ppm، 365 ppm، 2880 ppm and 27. 8%، respectively. The Y، Mn، Rb contents increase and Sr decreases with increasing magmatic differentiation. It shows that a moderate magmatic differentiation occurred during the crystallization of apatite. The total REE content in the Hormoz apatite is high (1. 22-2. 25%). LREE/HREE ratio is also high. This means that Hormoz apatites are enriched in light rare earth elements. The REE normalized pattern shows a negative slope with a negative Eu anomaly. According to various diagrams based on apatite composition، it is deduced that the Hormoz apatites belong to mafic I-type granitoids with high oxidation state (Fe2O3/FeO>1).