High temperature structural and thermoelastic behaviour of mantle orthopyroxene: an in situ neutron powder diffraction study

Gatta, G. Diego; Rinaldi, Rossella; Knight, Kevin S.; Molin, G.; Artioli, Gilberto

doi:10.1007/s00269-006-0138-2

Cited by 17 publications

(9 citation statements)

References 44 publications

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“…Additionally, no new OH band is observed during the process of increasing temperature, excluding the possibility of proton migration. Moreover, direct effect of thermal expansion of the sample over this temperature range can be neglected based on the reported thermal expansion coefficient for orthopyroxene (Smyth 1973;Gatta et al 2007). On the other hand, from the results of in situ polarized FTIR at varying temperatures, the variations of intensities and total integral absorbance of the OH bands with temperature are not due to changes of OH dipole direction.…”

Section: Temperature Dependence Of Integral Absorption Coefficientmentioning

confidence: 99%

OH in natural orthopyroxene: an in situ FTIR investigation at varying temperatures

et al. 2012

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In situ unpolarized and polarized Fourier transform infrared spectra of a natural orthopyroxene at varying temperatures were obtained using a heating stage attached on an Infrared microscope. The three main bands (3,595, 3,520 and 3,410 cm -1 ) at room temperature are ascribed to OH fundamental stretching bands. With increasing temperature from room temperature to 500°C, the 3,595 cm -1 band shifts 20 cm -1 to lower frequency. The total integral absorbance decreases with increasing temperature. These changes are reversible. Excluding the influences of dehydration, proton migration, thermal expansion, and changes in OH dipole direction, the change of integral absorbance with temperature reflects the temperature dependence of absorption coefficient due to the anharmonicity of OH vibration. Based on the integral absorption coefficient at room temperature (14.84 ppm -1 cm -2 ) from Bell et al. (Am Mineral 80:463-474, 1995), the integral absorption coefficients at other temperatures are calculated. The variation of integral absorption coefficient between room temperature and 500°C obtained in this study is about 18.5 % and may be greater at higher temperature according to the proposed linear relationship.

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Section: Temperature Dependence Of Integral Absorption Coefficientmentioning

confidence: 99%

OH in natural orthopyroxene: an in situ FTIR investigation at varying temperatures

et al. 2012

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“…Jadeite, the second form of jade, has a composition close to NaAlSi 2 O 6 . Due to the similarity of the XRPD patterns of the serpentinites and amphibole polymorphs [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], Raman spectroscopy is advantageous for mineral identification [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. The identification of specific minerals remains difficult, especially when their structures are degraded by firing in the kiln.…”

Section: Resultsmentioning

confidence: 99%

“…) are presented in the form of straight intensity lines at the pattern bottom[21][22][23][24][25][26][27][28][29]. See Appendix A for XRPD patterns of samples a and b.…”

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confidence: 99%

Asbestos-Based Pottery from Corsica: The First Fiber-Reinforced Ceramic Matrix Composite

Colomban

Kremenović

2020

Materials

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Asbestos-containing pottery shards collected in the northeast of Corsica (Cap Corse) and dating from the 19th century, or earlier, have been analyzed by SEM-EDS, XRPD, FTIR and Raman microspectroscopy. Blue (crocidolite) and white (chrysotile) asbestos fiber bundles are observed in cross-sections. Most of the asbestos is partly or totally dehydroxylated, and some transformation to forsterite is observed to occur, indicative of a firing above 800 °C. Examination of freshly fractured pieces shows a nonbrittle fracture with fiber pull-out, consistent with a composite material behavior, which makes these ceramics the oldest fiber-reinforced ceramic matrix composite. Residues indicate the use of this pottery as a crucible for gold extraction using cyanide.

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“…Thus the displacive Pbca ⇆ Cmca transition postulated for pure OEn may well occur over a compositional range that covers that of mantle orthopyroxene, except for the effect of aluminium that has not been investigated thus far. Non‐linear variations of volume, cell parameters and bond angles have been observed in orthopyroxenes on the En–Fs join, for compositions Fs 25 (transition above 1027 °C; (Yang & Ghose 1995), Fs 100 (transition at 1153 K, (Sueno et al 1976; Sueno et al 1984), Fs 6 orthopyroxene up to 1473 K, (Gatta et al 2007), and in a 3 per cent Ca‐bearing orthoenstatite, (Ohi et al 2008). The exact nature of the phase transition may vary from OEn to PEn in MgSiO 3 (Smyth 1971), while ferrosilite transforms to a high‐temperature C 2/ c form distinct from the high‐pressure isostructural form (Sueno et al .…”

Section: High‐temperature Transition In Mantle Orthopyroxenesmentioning

confidence: 97%

High-temperature elastic softening of orthopyroxene and seismic properties of the lithospheric upper mantle

Reynard¹,

Bass²,

Brenizer³

2010

Geophysical Journal International

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International audienceMineralogical models suggest that low velocity zones of the upper mantle may be accounted for by elasticity of dry rocks along geotherms away from the mid-oceanic ridges (MOR) while, closer to MOR, anelasticity plays a significant role in reducing shear wave velocities V(S) and generating attenuation. We investigate the potential influence of elastic softening, precursor of high-temperature phase transition in orthopyroxenes, on the seismic properties of the upper mantle. In situ Brillouin and Raman spectroscopy were used to evidence pre-transitional behaviour at high temperature in natural San Carlos orthopyroxene. Pre-transitional behaviour induces a large softening of the acoustic and low frequency modes, resulting in a large anharmonic decrease of sound velocities, similar to that observed in the MgSiO(3) end-member orthoenstatite. The high-temperature high-pressure phase diagram of enstatite is revised to account for the new phase transition, and a simple model is developed to evaluate elastic softening effects on the upper-mantle seismic properties, whose results depend much on the as yet poorly constrained pressure and compositional dependence of the phase transition boundary. Within the tested range of parameters, OPx softening is likely to affect the seismic properties of mantle rocks at depths shallower than 80 km in hot regions. Thus elastic softening of pyroxene is unlikely to affect the LVZ or continental lithospheric mantle unless the transition temperature is drastically reduced by incorporation of aluminium in orthopyroxene. It will contribute to a decrease of V(S) near MOR, hot spots and evolved continental rifts, where it can explain part of the non-linear high-temperature decrease of V(S) in the lithospheric oceanic mantle. It will affect the magnitude of anelastic effects and the nature of the likely mechanisms of attenuation required to match seismological observations

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High temperature structural and thermoelastic behaviour of mantle orthopyroxene: an in situ neutron powder diffraction study

Cited by 17 publications

References 44 publications

OH in natural orthopyroxene: an in situ FTIR investigation at varying temperatures

OH in natural orthopyroxene: an in situ FTIR investigation at varying temperatures

Asbestos-Based Pottery from Corsica: The First Fiber-Reinforced Ceramic Matrix Composite

High-temperature elastic softening of orthopyroxene and seismic properties of the lithospheric upper mantle

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