Determination of SiO2 Raman spectrum indicating the transformation from coesite to quartz in Gföhl migmatitic gneisses in the Moldanubian Zone, Czech Republic

Kobayashi, Tomoyuki; Hirajima, Tsuyoshi; Hiroi, Yoshikuni; Svojtka, Martin

doi:10.2465/jmps.071020

Cited by 36 publications

(18 citation statements)

References 32 publications

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“…Conversely, the appearance of the new peak at 520 cm −1 in the quartz spectrum is not a thermal effect associated with the power of the laser. This peak is characteristic of coesite and corresponds to the symmetric stretching of oxygen in the four‐membered SiO 4 tetrahedra . However, the Raman spectrum of coesite is normally characterised by additional peaks at 204, 270, 355 and 426 cm −1 , which were not present in our sample .…”

Section: Discussionmentioning

confidence: 99%

Effect of grain size distribution on Raman analyses and the consequences for in situ planetary missions

Foucher

López‐Reyes

Bost

et al. 2013

J Raman Spectroscopy

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Raman spectroscopy can be used for analysing both mineral and organic phases, thus allowing characterisation of the microbial‐scale geological context as well as the search for possible traces of life. This method is therefore very useful for in situ planetary exploration missions. Compared with the myriad of sample preparation techniques available in terrestrial laboratories, the possibilities for sample preparation during in situ missions on other planetary bodies are extremely limited and are generally restricted to abrasion of rock surfaces or crushing of the target samples. Whereas certain techniques need samples to be prepared in powder form, such as X‐ray diffraction, this kind of preparation is not particularly suitable for optical microscopy and/or Raman spectroscopy. In this contribution, we examine the effects of powdering rock and mineral samples on optical observations and Raman analyses. We used a commercial Raman spectrometer, as well as a Raman laser spectrometer that simulates the instrument being developed for the future ExoMars 2018 mission. The commercial Raman spectrometer documents significant modifications to the spectra of the powdered samples, including broadening of the peaks and shifts in their position, as well as the appearance of new peaks. These effects are caused by localised heating of the sample under the laser beam and amplification of nominal surface effects due to the increase in surface area in finer grain sizes. However, most changes observed in the Raman spectra using the Raman laser spectrometer system are negligible because the relatively large (50 µm diameter) laser spot size produces lower irradiance. Furthermore, minor phases were more easily detectable in the powdered samples. Most importantly, however, this sample preparation method results in the loss of the textural features and context, making identification of potential fossilized microbial remains more problematic. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Effect of grain size distribution on Raman analyses and the consequences for in situ planetary missions

Foucher

López‐Reyes

Bost

et al. 2013

J Raman Spectroscopy

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“…Geothermo-barometric calculations suggest that several eclogite and garnet peridotite masses in the Gföhl unit experienced UHP conditions (e.g., Nakamura et al, 2004;Medaris et al, 2006;Naemura et al, 2009). On the other hand, evidence for UHP metamorphism of felsic granulite and gneiss in the Bohemian Massif is rare, but a few findings of microdiamond and coesite from such felsic rocks have been recently reported (e.g., Kobayashi et al, 2008;Kotková et al, 2011;Perraki and Faryad, 2014), indicating that some garnet peridotite masses and surrounding felsic rocks may have shared the same P-T history, although peak P-T conditions of granulite in the Gföhl unit have been estimated to be approximately 1.6-2.0 GPa, 900-1100°C (e.g., Carswell and O'Brien, 1993).…”

Section: Geological Outlinementioning

confidence: 99%

Evidence for partial melting of eclogite from the Moldanubian Zone of the Bohemian Massif, Czech Republic

Miyazaki

Nakamura

Tamura

et al. 2016

Journal of Mineralogical and Petrological Sciences

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Eclogites from the Moldanubian Zone of the Bohemian Massif (Czech Republic) have experienced ultrahighpressure (UHP) and ultrahigh-temperature (UHT) metamorphic conditions (P > 4.0 GPa, T > 1000°C). One eclogite sample collected from Nové Dvory, eastern part of Czech Republic, contains leucocratic pockets. The mineral assemblage of the melanocratic part of the eclogite is garnet + omphacite + rutile + later-stage minerals (biotite + amphibole + plagioclase). The leucocratic pockets mainly consist of plagioclase and include moderate amounts of garnet and clinopyroxene + small amounts of biotite and amphibole. Garnet and clinopyroxene grains in the leucocratic pockets display faceted shapes whereas those in the melanocratic part show irregular shapes. These are consistent with the idea that garnet and clinopyroxene grains in the leucocratic pockets had been surrounded by melt, as melt can provide free space for the formation of such faceted shapes. The major and trace element composition of garnet grains in the melanocratic part are the same as those in the leucocratic pockets. Clinopyroxene also shows the same major and trace element composition for irregular shape grains in the melanocratic part as faceted grains in the leucocratic pockets. If the melt had originated from the gneiss surrounding the peridotite body with eclogite lenses or layers, the composition of clinopyroxene in the leucocratic pockets would have been completely different from that in the melanocratic part. In addition, the trace element composition of melt estimated from clinopyroxene composition resembles that of TonaliteTrondjhemite -Granodiorite (TTG), which can be produced by partial melting of eclogite. Thus, these observational and analytical data suggest that the leucocratic pockets were originally melt that was internally produced by partial melting of the eclogite.

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“…Mineralogical (increase in Ca of garnet from core to rim; Nakamura et al, 2004) and geochemical (e.g., positive Sr and Eu anomalies; Obata et al, 2006) characteristics of kyanite -bearing eclogites from this body suggest that at least some of them should have experienced subduction before the attainment of the UHP conditions of about 5 GPa, 1100 °C. Kobayashi et al (2008) found some peaks reflecting coesite relics in Raman spectra for SiO 2 inclusions in zircon that were extracted from the migmatitic gneiss near the Nové Dvory peridotite body, although the P -T path of the migmatitic gneiss of the Gföhl unit is still under debate (e.g., Cooke and O'Brien, 2001).…”

Section: Geological Settingmentioning

confidence: 99%

Sr-sulphate and associated minerals found from kyanite-bearing eclogite in the Moldanubian Zone of the Bohemian Massif, Czech Republic

Nakamura

Kobayashi

Shimobayashi

et al. 2010

Journal of Mineralogical and Petrological Sciences

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Sr -sulphate, celestine, was newly found in a kyanite -bearing eclogite associated with the Nové Dvory peridotite mass in the Moldanubian Zone of the Bohemian Massif, Czech Republic. Celestine is closely associated with anhydrite, pyrite, pyrrhotite and chalcopyrite, and those minerals occur in the matrix, where fine -grained omphacite aggregate and kelyphites after garnet develop. A common Sr reservoir in eclogite is known to be epidote, but the maximum pressure -temperature (P -T) conditions of the studied eclogite was estimated as about 1050 -1150 °C, 4.5 -4.9 GPa. In such extremely high P -T conditions, epidote should be unstable. In fact, epidote is absent from most of eclogites in the Moldanubian Zone of Czech Republic. These facts suggest that a Sr -reservoir after the epidote -breakdown in subducting eclogite might be celestine, or its high -P polymorph, although the formation stage of celestine in the study sample and maximum stability limits of celestine are not known. Another idea is that celestine in the study sample was formed at relatively shallow levels after the ascent of the eclogite. In this case, omphacite and apatite would have contained significant amount of Sr under the eclogitefacies conditions. Otherwise, metasomatic infiltration of Sr -rich fluids into the eclogite is necessary for the formation of celestine in order to provide sufficient amount of Sr. A Ba -rich alumino -silicate, probably celsian, was also found as a retrograde product around pyrrhotite in kelyphite and in symplectites mainly composed of augite and plagioclase after omphacite. Several grains of biotite are also present along the margin of garnet and in the symplectites after omphacite. In addition, small amounts of muscovite and amphibole are present in the symplectites after omphacite. These findings suggest that metasomatism with Sr -and Ba -rich fluids may have occurred during decompression of the eclogite and may not be indicative of the UHP history of these rocks.

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Determination of SiO2 Raman spectrum indicating the transformation from coesite to quartz in Gföhl migmatitic gneisses in the Moldanubian Zone, Czech Republic

Cited by 36 publications

References 32 publications

Effect of grain size distribution on Raman analyses and the consequences for in situ planetary missions

Effect of grain size distribution on Raman analyses and the consequences for in situ planetary missions

Evidence for partial melting of eclogite from the Moldanubian Zone of the Bohemian Massif, Czech Republic

Sr-sulphate and associated minerals found from kyanite-bearing eclogite in the Moldanubian Zone of the Bohemian Massif, Czech Republic

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