Ammonium-Bearing Fluorapophyllite-(K) in the Magnesian Skarns from Aleului Valley, Pietroasa, Romania

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dc.citation.articleNumber1362
dc.citation.issueNumber11
dc.citation.journalTitleMinerals
dc.citation.volumeNumber13
dc.contributor.authorMarincea, Ştefan
dc.contributor.authorDumitraş, Delia-Georgeta
dc.contributor.authorSava Ghineţ, Cristina
dc.contributor.authorFiliuţă, Andra Elena
dc.contributor.authorDal Bo, Fabrice
dc.contributor.authorHatert, Frédéric
dc.contributor.authorCostin, Gelu
dc.date.accessioned2024-05-03T15:51:12Z
dc.date.available2024-05-03T15:51:12Z
dc.date.issued2023
dc.description.abstractAn ammonium-bearing fluorapophyllite-(K) occurs as a late hydrothermal product in the outer endoskarn zone from Aleului Valley (N 46°37′04″, E 22°35′22″), located at the contact of the granodiorite laccolith from Pietroasa, of Upper Cretaceous age, with Anisian dolostones. Associated minerals are wollastonite, K feldspar, diopside, fluorapatite, talc, and pectolite. The chemical structural formula is [K0.985Na0.012(NH4)0.076]Σ=1.073(Ca4.009Mn0.001Fe2+0.003Mg0.002Ba0.001)Σ=4.016(Si7.953Al0.047) O20.029[F0.899(OH)0.101]·8.059H2O. The structure was successfully refined as tetragonal, space group P4/mnc, with cell parameters of a = 8.9685(1) Å and c = 15.7885(5) Å. The indices of refraction are ω = 1.534(1) and ε = 1.536(1). The calculated density is Dx = 2.381 g/cm3, in good agreement with the measured density, Dm = 2.379(4) g/cm3. The thermal analysis shows that the mineral completely dehydrates at up to 450 °C (endothermic effects at 330, 371, and 448 °C) and loses ammonium at 634 °C. In the infrared spectra, the multiplicity of the bands assumed to be silicate modes (1ν1 + 3ν3 + 2ν2 + 3ν4) agrees with the reduction in the symmetry of the SiO44− ion from Td to Cδ. Fluorapophyllite-(K) from Aleului Valley is of late hydrothermal origin and crystallized from F-rich fluids originating from the granodiorite intrusion, which mobilized K, Ca, and Si from the pre-existing feldspar.
dc.identifier.citationMarincea, Ş., Dumitraş, D.-G., Sava Ghineţ, C., Filiuţă, A. E., Dal Bo, F., Hatert, F., & Costin, G. (2023). Ammonium-Bearing Fluorapophyllite-(K) in the Magnesian Skarns from Aleului Valley, Pietroasa, Romania. Minerals, 13(11), Article 11. https://doi.org/10.3390/min13111362
dc.identifier.digitalminerals-13-01362-v2
dc.identifier.doihttps://doi.org/10.3390/min13111362
dc.identifier.urihttps://hdl.handle.net/1911/115567
dc.language.isoeng
dc.publisherMDPI
dc.rightsExcept where otherwise noted, this work is licensed under a Creative Commons Attribution (CC BY) license. Permission to reuse, publish, or reproduce the work beyond the terms of the license or beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.titleAmmonium-Bearing Fluorapophyllite-(K) in the Magnesian Skarns from Aleului Valley, Pietroasa, Romania
dc.typeJournal article
dc.type.dcmiText
dc.type.publicationpublisher version
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