Eudialyte Group Minerals from the Lovozero Alkaline Massif, Russia: Occurrence, Chemical Composition, and Petrogenetic Significance

The Lovozero Alkaline Massif intruded through the Archean granite-gneiss and Devonian volcaniclastic rocks ca. 360 Ma ago and formed a large laccolith-type body. The lower part of the massif (the Layered complex) is composed of regularly repeating rhythms: melanocratic nepheline syenite (lujavrite,...

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Bibliographic Details
Published in:Minerals (Basel) 2020-12, Vol.10 (12), p.1070
Main Authors: Mikhailova, Julia A., Pakhomovsky, Yakov A., Panikorovskii, Taras L., Bazai, Ayya V., Yakovenchuk, Victor N.
Format: Article
Language:English
Subjects:
Amphiboles
Chemical composition
Crystal structure
Crystallization
Devonian
eudialyte-group minerals
Fractional crystallization
Gneiss
Iron
Lovozero Alkaline Massif
Manganese
Massifs
Minerals
Nepheline
Petrogenesis
Petrography
Petrology
Rhythm
Rocks
Syenite
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Summary:The Lovozero Alkaline Massif intruded through the Archean granite-gneiss and Devonian volcaniclastic rocks ca. 360 Ma ago and formed a large laccolith-type body. The lower part of the massif (the Layered complex) is composed of regularly repeating rhythms: melanocratic nepheline syenite (lujavrite, at the top), leucocratic nepheline syenite (foyaite), foidolite (urtite). The upper part of the massif (the Eudialyte complex) is indistinctly layered, and lujavrite enriched with eudialyte-group minerals (EGM) prevails there. In this article, we present the results of a study of the chemical composition and petrography of more than 400 samples of the EGM from the main types of rock of the Lovozero massif. In all types of rock, the EGM form at the late magmatic stage later than alkaline clinopyroxenes and amphiboles or simultaneously with it. When the crystallization of pyroxenes and EGM is simultaneous, the content of ferrous iron in the EGM composition increases. The Mn/Fe ratio in the EGM increases during fractional crystallization from lujavrite to foyaite and urtite. The same process leads to an increase in the modal content of EGM in the foyaite of the Layered complex and to the appearance of primary minerals of the lovozerite group in the foyaite of the Eudialyte complex.
ISSN:2075-163X
2075-163X
DOI:10.3390/min10121070