The current study provides new data on δ 13 C of carbonates from the REE-rich Paleozoic Kovdor massif. It is an ultramafic, alkaline and carbonatite intrusion in the northeastern part of the Baltic Shield (Kola region, Russia). The carbonates have been sampled from the main outcrop of the phoscoritecarbonatite Kovdor massif. According to Rb-Sr and U-Pb data, its age is 420-360 Ma [3, 10]. The massif was formed in the active zone of a continental type as a result of hot spot plutonism on the Kola Peninsula. The selected ore minerals have been analyzed with optical and electron microscopy (Hitachi SU6600 with EDS attachment), whereas δ 13 C has been determined in the Mass Spectrometry Laboratory, Maria Curie-Skłodowska University. The works aim at studying the stable isotope in representative Ca-Mg-Sr carbonatites sampled by V.V. Balagansky in 2003. They have been analyzed using ICP-OAS and XRF in the Department of Soil Science in order to estimate metal concentrations.
The paper considers the relationship between textural and structural features and gross mineral and chemical composition of minerals and the physical properties of apatite-nepheline ores and their processing. It is noted that the change in the physical properties of ores involves primarily the change in their mineral composition due to apatite depletion. An increase in the content of nepheline and pyroxene to 35-55 % sharply increases the ore strength up to 47-104 MPa, which entails the growth of energy consumption for grinding. An important factor is that the ore contains high-strength poikilitic intergrowths of apatite with nepheline, pyroxene, and titanite, in which about 20 % of fine-grained apatite is concentrated, and the extraction of which is a complex technological problem. The authors attribute a change in the chemical composition of apatite to the main factors deteriorating the product quality. According to the studies, the chemical composition of apatite is unstable and varies in the content of P2O5 (37.20-42.6 %), SrO (2.29-5.36 %), and Tr2O3 (0.51-1.05 %). It is noted that a change in the composition may affect the flotation properties and quality of the concentrate.
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