Textural variations and origin of apatite and other phosphates in the Gruvberget deposit (Northern Sweden)

The Gruvberget deposit, located in northern Sweden, comprises part of the Kiruna iron mining district, one of the most valuable regions of the world for extraction of iron. The open-pit Gruvberget ore is classified as Kiruna-type iron oxide-apatite (IOA) deposit with apatite as the main accessory gangue mineral. As apatite can host high quantities of rare earth elements, LKAB, the mining company responsible for the Kiruna mining district, is now starting to consider the possibility to use tailings for possible future exploitation of rare earth elements. Ore samples were collected from selected drill cores and investigated using optical microscopy, laser Raman spectroscopy, EPMA and SEM-cathodoluminescence. Investigations focused on apatite textural variations throughout the magnetite-dominated, hematite-dominated and magnetite-hematite-dominated domains. Also other REE-bearing minerals, such as monazite and allanite, were also taken into consideration in the research. Observations revealed both petrographical and geochemical variations of apatite, which includes its crystal size and distribution, its association with iron oxide and other gangue minerals, possible inclusion characterization and Cl- and F-content variations. Moreover, possible implications on the origin of apatite in the Gruvberget IOA deposit is discussed.