Contrasting parageneses in mica schists of the Hohe Tauern, caused by manganese and zinc
Journal article
Authors / Editors
Research Areas
- Earth and related Environmental sciences (NATURAL SCIENCES)
(Geosciences, multidisciplinary; Mineralogy; Palaeontology; Geochemistry and geophysics; Physical geography; Geology; Volcanology; Environmental sciences (social aspects to be 5.7);
- Meteorology and atmospheric sciences; climatic research;
- Oceanography; Hydrology; Water resources;) - ENGINEERING AND TECHNOLOGY (Frascati classification)
Publication Details
Subtitle: Contrasting parageneses in mica schists of the Hohe Tauern, caused by manganese and zinc
Author list: Proyer, Alexander
Publisher: Springer Verlag (Germany)
Publication year: 2000
Journal: Mineralogy and Petrology (0930-0708)
Volume number: 69,
Issue number: 3-4
Start page: 197
End page: 212
Number of pages: 16
ISSN: 0930-0708
eISSN: 1438-1168
Abstract
Two compositionally similar types of metapelites from the same outcrop in the eastern Hohe Tauern/Austria (Lieserkarscharte, Silbereck Series) have evolved two distinctly different AFM parageneses. While both contain quartz, muscovite, kyanite and hematite, one type contains additional chloritoid (chloritoid schist), the other one additional garnet, chlorite, staurolite and allanite (garnet schist). This behaviour is shown to be caused by higher contents of manganese and zinc in the garnet schists (MnO ≥ 0.25%, Zn ≥ 140 ppm), which triggered two FMASH isograd reactions that were never reached by the chemically purer chloritoid schists (MnO ≤ 0.03%, Zn ≤ 70 ppm). Garnet and staurolite appeared as new phases, buffering manganese and zinc, respectively. Both types of mica schist have evolved from a single, compositionally almost homogeneous pelite or chlorite pyrophyllite schist. In fact, reactions representing specific isograds occurred only in mica schists containing impurities. They caused the growth of some extra phases which enabled us to calculate the PT-conditions of the final equilibration (around 540 ± 25°C and 12 ± 2 kbar). These rocks are a good example of the importance of minor elements in moderately high-pressure schists as compared to the already well known effects of these elements in medium-grade metamorphic mica schists.
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