Fluorine Controls Mineral Assemblages of Alkaline Metasomatites
In the Khibiny and Lovozero alkaline massifs, there are numerous xenoliths of the so-called ‘aluminous hornfelses’ composed of uncommon mineral associations, which, firstly, are ultra-aluminous, and secondly, are highly reduced. (K,Na)-feldspar, albite, hercynite, fayalite, minerals of the phlogopit...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2022-08-01
|
| Series: | Minerals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-163X/12/9/1076 |
| _version_ | 1797484500688568320 |
|---|---|
| author | Julia A. Mikhailova Yakov A. Pakhomovsky Natalia G. Konopleva Andrey O. Kalashnikov Victor N. Yakovenchuk |
| author_facet | Julia A. Mikhailova Yakov A. Pakhomovsky Natalia G. Konopleva Andrey O. Kalashnikov Victor N. Yakovenchuk |
| author_sort | Julia A. Mikhailova |
| collection | DOAJ |
| description | In the Khibiny and Lovozero alkaline massifs, there are numerous xenoliths of the so-called ‘aluminous hornfelses’ composed of uncommon mineral associations, which, firstly, are ultra-aluminous, and secondly, are highly reduced. (K,Na)-feldspar, albite, hercynite, fayalite, minerals of the phlogopite-annite and cordierite-sekaninaite series, corundum, quartz, muscovite, sillimanite, and andalusite are rock-forming minerals. Fluorite, fluorapatite, ilmenite, pyrrhotite, ulvöspinel, troilite, and native iron are characteristic accessory minerals. The protolith of these rocks is unknown. We studied in detail the petrography, mineralogy, and chemical composition of these rocks and believe that hornfelses were formed as a result of the metasomatic influence of foidolites. The main reason for the formation of an unusual aluminous association is the high mobility of aluminum promoted by the formation of fluid expelled from foidolites of the Na-Al-OH-F complexes. Thus, it is fluorine that controls the mobility of aluminum in the fluid and, consequently, the mineral associations of alkaline metasomatites. The gain of alkalis and aluminum to rocks of protolith was the reason for the intense crystallization of (K,Na)-feldspar. As a result, a SiO<sub>2</sub> deficiency was formed, and Si-poor, Al-rich silicates and/or oxides crystallized. |
| first_indexed | 2024-03-09T23:05:17Z |
| format | Article |
| id | doaj.art-cb9ac12ff14b4144a79d5bca0e5174da |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-09T23:05:17Z |
| publishDate | 2022-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-cb9ac12ff14b4144a79d5bca0e5174da2023-11-23T17:55:03ZengMDPI AGMinerals2075-163X2022-08-01129107610.3390/min12091076Fluorine Controls Mineral Assemblages of Alkaline MetasomatitesJulia A. Mikhailova0Yakov A. Pakhomovsky1Natalia G. Konopleva2Andrey O. Kalashnikov3Victor N. Yakovenchuk4Geological Institute of the Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, 184209 Apatity, RussiaGeological Institute of the Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, 184209 Apatity, RussiaGeological Institute of the Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, 184209 Apatity, RussiaGeological Institute of the Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, 184209 Apatity, RussiaGeological Institute of the Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, 184209 Apatity, RussiaIn the Khibiny and Lovozero alkaline massifs, there are numerous xenoliths of the so-called ‘aluminous hornfelses’ composed of uncommon mineral associations, which, firstly, are ultra-aluminous, and secondly, are highly reduced. (K,Na)-feldspar, albite, hercynite, fayalite, minerals of the phlogopite-annite and cordierite-sekaninaite series, corundum, quartz, muscovite, sillimanite, and andalusite are rock-forming minerals. Fluorite, fluorapatite, ilmenite, pyrrhotite, ulvöspinel, troilite, and native iron are characteristic accessory minerals. The protolith of these rocks is unknown. We studied in detail the petrography, mineralogy, and chemical composition of these rocks and believe that hornfelses were formed as a result of the metasomatic influence of foidolites. The main reason for the formation of an unusual aluminous association is the high mobility of aluminum promoted by the formation of fluid expelled from foidolites of the Na-Al-OH-F complexes. Thus, it is fluorine that controls the mobility of aluminum in the fluid and, consequently, the mineral associations of alkaline metasomatites. The gain of alkalis and aluminum to rocks of protolith was the reason for the intense crystallization of (K,Na)-feldspar. As a result, a SiO<sub>2</sub> deficiency was formed, and Si-poor, Al-rich silicates and/or oxides crystallized.https://www.mdpi.com/2075-163X/12/9/1076Lovozero massifKhibiny massifaluminous hornfelsesalkaline metasomatismfoidolites |
| spellingShingle | Julia A. Mikhailova Yakov A. Pakhomovsky Natalia G. Konopleva Andrey O. Kalashnikov Victor N. Yakovenchuk Fluorine Controls Mineral Assemblages of Alkaline Metasomatites Minerals Lovozero massif Khibiny massif aluminous hornfelses alkaline metasomatism foidolites |
| title | Fluorine Controls Mineral Assemblages of Alkaline Metasomatites |
| title_full | Fluorine Controls Mineral Assemblages of Alkaline Metasomatites |
| title_fullStr | Fluorine Controls Mineral Assemblages of Alkaline Metasomatites |
| title_full_unstemmed | Fluorine Controls Mineral Assemblages of Alkaline Metasomatites |
| title_short | Fluorine Controls Mineral Assemblages of Alkaline Metasomatites |
| title_sort | fluorine controls mineral assemblages of alkaline metasomatites |
| topic | Lovozero massif Khibiny massif aluminous hornfelses alkaline metasomatism foidolites |
| url | https://www.mdpi.com/2075-163X/12/9/1076 |
| work_keys_str_mv | AT juliaamikhailova fluorinecontrolsmineralassemblagesofalkalinemetasomatites AT yakovapakhomovsky fluorinecontrolsmineralassemblagesofalkalinemetasomatites AT nataliagkonopleva fluorinecontrolsmineralassemblagesofalkalinemetasomatites AT andreyokalashnikov fluorinecontrolsmineralassemblagesofalkalinemetasomatites AT victornyakovenchuk fluorinecontrolsmineralassemblagesofalkalinemetasomatites |