Minor element- and carbonaceous material thermometry of high-grade metapelites from the Sauwald Zone, Southern Bohemian Massif (Upper Austria)

Wyhlidal, Stefan; Tropper, Peter; Thöny, Werner F.; Kaindl, Reinhard

doi:10.1007/s00710-009-0081-2

Cited by 8 publications

(3 citation statements)

References 31 publications

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“…However, it was found that the bulk Na 2 O influences the Na contents of cordierite, and therefore the bulk composition of the sample has to be taken into account. Thus, the authors (Wyhlidal et al., 2007a, 2007b; Wyhlidal et al., 2008; Wyhlidal, Tropper, Thöny, & Kaindl, 2009) proposed two calibrations, one for low bulk Na 2 O (<1% Na 2 O) and the other for high bulk Na 2 O (>1% Na 2 O) contents.…”

Section: P–t Pseudosections and Conventional Thermobarometrymentioning

confidence: 99%

“…The bulk composition determined from the thin section yielded a bulk Na 2 O content of 1.72% indicating that only the calibration for high bulk Na 2 O is suitable for temperature calculation. The temperature dependence of Na incorporation in cordierite for high bulk Na 2 O is described by the following equation (Wyhlidal et al., 2007a, 2007b; Wyhlidal et al., 2008, 2009):

T = Na - 0.36811 / - 0.000386

where T is temperature in °C, and Na is the Na content of cordierite in a.f.u.…”

Section: P–t Pseudosections and Conventional Thermobarometrymentioning

confidence: 99%

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Deformation‐induced cordierite breakdown–An example from western Maine, USA

Sanislav

Sharib

Gromard

2020

Journal Metamorphic Geology

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Preservation of partially completed metamorphic reactions in the form of partial pseudomorphs is very important as it provides direct insight onto the reaction mechanism and the phases involved in the reaction. The staurolite and andalusite grade rocks in western Maine, USA, contain cordierite porphyroblasts partly pseudomorphed by coarse-grained muscovite and biotite. The pseudomorphs consist of a cordierite core surrounded by a reaction rim. Modal mineralogy, calculated using the ImageJ processing software based on backscatter images and X-ray compositional maps, reveals that the core consists of cordierite (53.5%), muscovite (22.8%), biotite (9.1%), quartz (1 0.4%), plagioclase (3.1%) and ilmenite/pyrrhotite and apatite (1.1%) whereas the reaction rim consists of cordierite (1.8%), muscovite (51.6%), biotite (30.4%), quartz (4.3%), plagioclase (10%), garnet (1.2%), ilmenite/pyrrhotite and apatite (0.8%). The net effect of the cordierite breakdown reaction is an increase of 226% in muscovite, 334% in biotite and 323% in plagioclase content and a decrease of 97% in cordierite. The reaction involved exchange of components with the matrix requiring addition of H 2 O, K + , Na + and Ti 4+ and removal of SiO 2 , Mg 2+ and PO 4 3from the reaction site. PT estimates using the garnet-biotite, Ti-in-biotite, Na-in-cordierite thermometers and the garnet-biotite-muscovite-plagioclase barometer indicate that cordierite breakdown occurred at ~550°C and 3.5 kbar. thermocalc modelling using the bulk rock composition suggests that cordierite is not stable at these conditions, whereas modelling using a thin section-derived bulk composition indicates that cordierite stability extends to higher pressures, and most likely that the cordierite breakdown was not PT dependent. The incorporation of Na (up to 0.18 a.f.u.) into the cordierite structure has the effect of stabilizing the cordierite under a variety of H 2 O activity and limiting the role of fluids into destabilizing it. The cordierite cores contain evidence of plastic and brittle deformation in the form of subgrains and microcracks, which facilitated the infiltration of fluids that destabilized cordierite at constant PT conditions by leaching Na and introducing K. New mica growth along these structural heterogeneities suggests that deformation played an important role promoting breakdown of cordierite to muscovite and biotite.

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Section: P–t Pseudosections and Conventional Thermobarometrymentioning

confidence: 99%

T = Na - 0.36811 / - 0.000386

where T is temperature in °C, and Na is the Na content of cordierite in a.f.u.…”

Section: P–t Pseudosections and Conventional Thermobarometrymentioning

confidence: 99%

Deformation‐induced cordierite breakdown–An example from western Maine, USA

Sanislav

Sharib

Gromard

2020

Journal Metamorphic Geology

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“…Geothermometry based on the Raman spectra of carbonaceous material (RSCM) was invented for different types of rocks [26][27][28][29]. This technique has been successfully used to estimate the peak temperatures of both regional and contact metamorphism [30][31][32][33][34][35]. According to Reference [36], it works even in the case of polymetamorphic complexes.…”

Section: Introductionmentioning

confidence: 99%

Carbon Sources and the Graphitization of Carbonaceous Matter in Precambrian Rocks of the Keivy Terrane (Kola Peninsula, Russia)

et al. 2019

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The Precambrian rocks of the Keivy Terrane reveal five types of carbonaceous matter (CM): Fine-grained, flaky, nest, vein, and spherulitic. These types differ in their distribution character, carbon isotope composition, and graphitization temperatures calculated by the Raman spectra of carbonaceous material (RSCM) geothermometry. Supracrustal rocks of the Keivy Terrane contain extremely isotopically light (δ13CPDB = –43 ± 3‰) carbon. Presumably, its source was a methane–aqueous fluid. According to temperature calculations, this carbon matter and the host strata underwent at least two stages of metamorphism in the west of the Keivy Terrane and one stage in the east. The CM isotope signatures of several samples of kyanite schists (δ13CPDB = –33 ± 5‰) are close to those of oils and oil source rocks, and they indicate an additional carbon reservoir. Thus, in the Keivy territory, an oil-and-gas bearing basin has existed. Heavy carbon (δ13CPDB = −8 ± 3‰) precipitated from an aqueous CO2-rich fluid is derived from either the lower crust or the mantle. This fluid probably migrated from the Keivy alkaline granites into the surrounding rocks previously enriched with “methanogenic” carbon.

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