Occurrence of metasomatic monazite-xenotime inclusions in chlorapatites of Esfordi phosphate deposit

Apatite is the most common phosphate mineral in the Esfordi ore body. Euhedral crystal (2-20 cm) of the apatite occurs as an intergrowth in magnetite and hematite, vein and dike. There are two types of apatite in the Esfordi deposit, based on Petrographic studies: primary and secendary. Fresh and altered parts of primary apatite display dark and light color respectively using BSE images. EMP analyses demonstrate that primary apatites (light area) were chlorapatite in composition and have been partially changed into hydroxyle-flourapatite (dark area) by the metasomatic process. Lighter areas represent more Cl, SiO2, Na2O and LREE+Y enriched apatites. Monazite and xenotime inclusions in apatite can be classified into two types: primary (30-100µm) and hydrothermal (5-20µm). The hydrothermal inclusions are found in the dark area, apatite crack and along grain boundaries. The monazite and xenotime inclusions in the dark areas are enriched in LREE and HREE+Y respectively. Monazite-xenotime thermometer yielded a temperature of about 150-350°C for apatite metasomatism and hydrothermal monazite-xenotime formation, coincides with greenschist facies conditions.