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Article

Towards Identification of Zircon Populations in Permo-Carboniferous Rhyolites of Central Europe: Insight from Automated SEM-Mineral Liberation Analyses

1
Instytut Nauk Geologicznych, Uniwersytet Wrocławski, pl. Maksa Borna 9, 50-204 Wrocław, Poland
2
Institut für Mineralogie, Lagerstättenlehre und Petrologie, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg/Sachsen, Germany
3
Institut für Geologie, TU Bergakademie Freiberg, Bernhard von Cotta Str. 2, 09599 Freiberg/Sachsen, Germany
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(4), 308; https://doi.org/10.3390/min10040308
Received: 24 February 2020 / Revised: 24 March 2020 / Accepted: 28 March 2020 / Published: 30 March 2020
(This article belongs to the Special Issue Accessory Minerals in Silicic Igneous Rocks)
Zircon is a main mineral used for dating rhyolitic magmas as well as reconstructing their differentiation. It is common that different populations of zircon grains occur in a single rhyolitic sample. The presence of both autocrystic and antecrystic zircon grains is reflected in their strongly varied chemical compositions and slight spread of ages. However, postmagmatic processes may induce lead loss, which is also recorded as a spread of zircon ages. Therefore, new approaches to identify different zircon populations in rhyolitic rocks are needed. In this study, we suggest that detailed examination of zircon positions in the thin sections of rhyolitic rocks provides valuable information on zircon sources that can be used to identify autocrystic and antecrystic zircon populations. Automated Scanning Electron Microscope (SEM) analyses are of great applicability in determining this, as they return both qualitative and quantitative information and allow for quick comparisons between different rhyolite localities. Five localities of Permo-Carboniferous rhyolites related to post-Variscan extension in Central Europe (Organy, Bieberstein, Halle, Chemnitz, Krucze) were analyzed by automated SEM (MLA-SEM). The samples covered a range of Zr whole rock contents and displayed both crystalline and glassy groundmass. Surprisingly, each locality seemed to have its own special zircon fingerprint. Based on comparisons of whole rocks, modal composition and SEM images Chemnitz ignimbrite was interpreted as containing mostly (or fully) antecrystic zircon, whereas the Bieberstein dyke was shown to possibly contain both types, with the antecrystic zircon being associated with disturbed cumulates. On the other hand, Organy was probably dominated by autocrystic zircon, and Krucze contained dismembered, subhedral zircon in its matrix, whereas Halle zircon was located partly in late veins, filling cracks in laccolith. Both localities may, therefore, contain zircon populations that represent later stages than the crystallization of the main rhyolitic body. View Full-Text
Keywords: volcanic rock structure; subvolcanic; pyroclastic; zircon associations; zircon saturation; mineral liberation analysis (MLA) volcanic rock structure; subvolcanic; pyroclastic; zircon associations; zircon saturation; mineral liberation analysis (MLA)
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MDPI and ACS Style

Przybyło, A.; Pietranik, A.; Schulz, B.; Breitkreuz, C. Towards Identification of Zircon Populations in Permo-Carboniferous Rhyolites of Central Europe: Insight from Automated SEM-Mineral Liberation Analyses. Minerals 2020, 10, 308. https://doi.org/10.3390/min10040308

AMA Style

Przybyło A, Pietranik A, Schulz B, Breitkreuz C. Towards Identification of Zircon Populations in Permo-Carboniferous Rhyolites of Central Europe: Insight from Automated SEM-Mineral Liberation Analyses. Minerals. 2020; 10(4):308. https://doi.org/10.3390/min10040308

Chicago/Turabian Style

Przybyło, Arkadiusz, Anna Pietranik, Bernhard Schulz, and Christoph Breitkreuz. 2020. "Towards Identification of Zircon Populations in Permo-Carboniferous Rhyolites of Central Europe: Insight from Automated SEM-Mineral Liberation Analyses" Minerals 10, no. 4: 308. https://doi.org/10.3390/min10040308

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