Melt inclusions in olivines from phoscorites and olivinites of the Kovdor massif.
- 1Sobolev Institute of Geology and Mineralogy Siberian Branch Russia Academy of Sciences (SB RAS), pr. Ak. Koptyuga 3, 630090, Novosibirsk, Russia (redina@igm.nsc.ru)
- 2German Research Centre for Geosciences, GFZ, Telegrafenberg, 14473 Potsdam, Germany (cwohl@gfz-potsdam.de)
- 3Kola Science Centre, Russian Academy of Sciences, Fersman St. 14, 184209, Apatity, Russia (ylya_korchak@mail.ru)
The Kovdor massif is a part of the Paleozoic Kola alkaline province and located in the eastern part of the Baltic Shield. Kovdor carbonatites host a unique complex baddeleyite-apatite-magnetite deposit from which iron ores and zirconium have been mined. New data on melt inclusions in olivine crystals from phoscorites and olivinites of the ore complex are presented in this contribution. Daughter minerals in crystallized melt inclusions were identified by Raman spectroscopy and scanning electron microscopy. The trace element composition of inclusions was determined using LA-ICP-MS.
Melt inclusions in olivine from Kovdor phoscorites are negative crystal or round in shape, with sizes ranging from 5 to 50 microns. They form groups or line up. According to the mineral composition, two types of melt inclusions can be distinguished: carbonate and silicate-carbonate. In the first type, Ca-Na-Mg- (Sr?) - REE carbonates are dominant among daughter phases. In the second one, silicate phases (phlogopite, monticellite, diopside), Ca-Na-Mg carbonates and magnetite are found together. Melt inclusions in olivine from olivinites are isometric or elongated, 5–25 μm in size. They form groups or occur as isolated inclusions. Benstoneite, geylussit, ankerite, calcite and hydroxyl-bastnesite along with phyllosilicates (phlogopite, paragonite?) were identified among daughter minerals.
The rare earth elements composition of melt inclusions from both types of rocks is characterized by the predominance of light REE. The content of REE, especially light ones, in inclusions from phoscorites is higher. Strontium and barium contents in most melt inclusions have negative correlations with niobium and zirconium concentrations.
Melt inclusions from phoscorites and olivinites contain carbonate and silicate mineral phases in various proportions, which may imply heterogeneous trapping of crystalline phases and two immiscible melts, silicate and carbonatite. Inclusions from phoscorite represent a more evolved magma with higher concentrations of rare metals.
This work was supported by the Russian Science Foundation, grant No 19-17-00013.
How to cite: Redina, A., Wohlgemuth-Ueberwasser, C., Mikhailova, J., and Ivanyuk, G.: Melt inclusions in olivines from phoscorites and olivinites of the Kovdor massif., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12611, https://doi.org/10.5194/egusphere-egu2020-12611, 2020
