Microlite-group minerals: tracers of complex post-magmatic evolution in beryl–columbite granitic pegmatites, Maršíkov District, Bohemian Massif, Czech Republic.
In: Mineralogical Magazine, Jg. 85 (2021-10-01), Heft 5, S. 725-743
Online
academicJournal
Zugriff:
Microlite-group minerals occur as common replacement products after primary and secondary columbite-group minerals (CGM) in albitised blocky K-feldspar and in coarse-grained, muscovite-rich units of the Schinderhübel I, Scheibengraben and Bienergraben beryl–columbite pegmatites in the Maršíkov District (Silesian Unit, Bohemian Massif, Czech Republic). Textural and compositional variations of microlite-group minerals were examined using electron probe micro-analyses and microRaman spectroscopy (μRS). A complex post-magmatic evolution of the pegmatites and the following microlite populations (Mic) and related processes were found: (1) precipitation of U, Na-rich and F-poor Mic I on cracks in CGM; (2) alteration of Mic I to U-rich together with Na- and F-poor Mic II; and (3) partial replacement of Mic I and II by Mic III with a distinct Na, U and Ti loss and Ca and F gain. Stage (2) includes an extensive leaching of Na, without U loss. The final stage (3) produced euhedral-to-subhedral oscillatory zoned Ca and F enriched Mic III with distinctly different composition to the previous F-poor and A-site vacant Mic II. Aggregates of fersmite are associated commonly with Mic III. Distal Mic IIId occurs locally on cracks in K-feldspar or quartz, with compositions analogous to Mic III. Compositional variations and textural features of microlite-group minerals during dissolution–reprecipitation processes serve as sensitive tracers of post-magmatic evolution in granitic pegmatites recording complex interactions between magmatic pegmatite units and externally derived, hydrothermal metamorphic fluids. [ABSTRACT FROM AUTHOR]
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Microlite-group minerals: tracers of complex post-magmatic evolution in beryl–columbite granitic pegmatites, Maršíkov District, Bohemian Massif, Czech Republic.
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Autor/in / Beteiligte Person: | Chládek, Štěpán ; Uher, Pavel ; Novák, Milan ; Bačík, Peter ; Opletal, Tomáš |
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Zeitschrift: | Mineralogical Magazine, Jg. 85 (2021-10-01), Heft 5, S. 725-743 |
Veröffentlichung: | 2021 |
Medientyp: | academicJournal |
ISSN: | 0026-461X (print) |
DOI: | 10.1180/mgm.2021.58 |
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