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  • 1
    Electronic Resource
    Electronic Resource
    Compression of witherite to 8 GPa and the crystal structure of BaCO3II (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 467-473 
    Details
    ISSN: 1432-2021
    Keywords: Key words Witherite ; High pressure ; Aragonite ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Natural witherite (Ba0.99Sr0.01CO3) has been studied by single-crystal X-ray diffraction in the diamond anvil cell at eight pressures up to 8 GPa. At ambient pressure, cell dimensions are a = 5.3164(12) Å, b = 8.8921(19) Å, c = 6.4279(16) Å, and the structure was refined in space group Pmcn to R(F) = 0.020 from 2972 intensity data. The unit cell and atom position parameters for the orthorhombic cell were refined at pressures of 1.2, 2.0, 2.9, 3.9, 4.6, 5.5, 6.2, and 7.0 GPa. The volume-pressure data are used to calculate equation of state parameters K T0 = 50.4(12) GPa and K′ = 1.9(4). At approximately 7.2 GPa, a first-order transformation to space group P3¯1c was observed. Cell dimensions of the high-pressure phase at 7.2 GPa are a = 5.258(6) Å, c = 5.64(1) Å. The high pressure structure was determined and refined to R(F) = 0.06 using 83 intensity data, of which 15 were unique. This high-pressure phase appears to be more compressible than the orthorhombic phase with an estimated initial bulk modulus (K 7.2GPa) of 10 GPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690000087
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  • 2
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    Shear waves in the diamond-anvil cell reveal pressure-induced instability in (Mg,Fe)O (2004)
    National Academy of Sciences
    Details
    Publication Date: 2004-04-12
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    Degassing of reduced carbon from planetary basalts (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-04-08
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 4
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    Quantification of water in majoritic garnet (2015)
    Mineralogical Society of America
    Details
    Publication Date: 2015-05-13
    Description: Majoritic garnet, characterized by an excess of silicon (〉3 Si per formula unit), is considered one of the major phases of the Earth’s transition zone from 410–660 km depth. Quantifying the H 2 O content of nominally anhydrous mantle minerals is necessary to evaluate their water storage capacity from experiments and modeling the Earth’s deep water cycle. We present mineral-specific infrared absorption coefficients for the purpose of quantifying the amount of water incorporated into majorite as hydroxyl point defects. A suite of majoritic garnet samples with varying proportions of Si, Fe, Al, Cr, and H 2 O was synthesized at conditions of 18–19 GPa and 1500–1800 °C. Single-crystals were characterized using X-ray diffraction, electron microprobe analysis, secondary ion mass spectrometry (SIMS), IR, Raman, and Mössbauer spectroscopy. We utilize SIMS and Raman spectroscopy in combination with IR spectroscopy to provide IR absorption coefficients for water in majoritic garnets with the general mineral formula (Mg,Fe) 3 (Si,Mg,Fe,Al,Cr) 2 [SiO 4 ] 3 . The IR absorption coefficient for majoritic garnet in the OH stretching region is frequency dependent and ranges from 10 470 ± 3100 Lmol –1 cm –2 to 23 400 ± 2300 Lmol –1 cm –2 .
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 5
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    Degassing of reduced carbon from planetary basalts [Earth, Atmospheric, and Planetary Sciences] (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-05-15
    Description: Degassing of planetary interiors through surface volcanism plays an important role in the evolution of planetary bodies and atmospheres. On Earth, carbon dioxide and water are the primary volatile species in magmas. However, little is known about the speciation and degassing of carbon in magmas formed on other planets (i.e.,...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 6
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    Single-crystal neutron diffraction and Raman spectroscopic study of hydroxylherderite, CaBePO4(OH,F) (2014)
    Mineralogical Society of Great Britain and Ireland
    Details
    Publication Date: 2014-07-25
    Description: The crystal structure, H bonding and chemical composition of hydroxylherderite from the Bennett pegmatite, Buckfield, Oxford County, Maine, USA were investigated by single-crystal X-ray diffraction and neutron Laue diffraction, electron microprobe analysis in wavelength-dispersive mode, inductively coupled plasma-atomic emission spectrometry and polarized Raman spectroscopy [ Ca (Na 0.01 Ca 1.01 ) 1.02 Be (Be 0.98 Li 0.01 ) 0.99 (Si 0.03 P 0.98 ) 1.01 O 4 (OH 0.67 F 0.33 ) 1 , Z = 4, a = 9.7856(5), b = 7.6607(5), c = 4.8025(3) Å, β = 90.02(3)°, V= 360.02(4) Å 3 , space group P 2 1 / a ]. The neutron-structure refinement converged with fully anisotropic displacement parameters to give a final agreement index R 1 = 0.0363 for 85 refined parameters and 1614 unique reflections with F o 〉4( F o ). The structure refinement was used to determine the H position and geometry of H bonding in the structure. One H site was found on the O 5 anion with an O–H interatomic distance, corrected for "riding motion", of 0.996(2) Å. The H bond of hydroxylherderite is bifurcated with O 2 and O 4 acceptors forming H bonds with O 5··· O 2 = 3.163(1) Å, H ··· O 2 = 2.544(2) Å and O 5– H ··· O 2 = 121.8(1)°; O 5··· O 4 = 3.081(1) Å, H ··· O 4 = 2.428(2) Å and O 5– H ··· O 4 = 124.4(1)°. The highly non-linear O–H···O hydrogen bonds in hydroxylherderite and in the isotypic datolite [ideally CaBSiO 4 (OH)] are constrained by the tetrahedral network topology. Two main O–H stretching modes were observed in the Raman spectra at 3565 and 3620 cm –1 , which are attributed to the bifurcated H bond. Two additional weak bands at 3575 and 3610 cm –1 are attributed to Si–P disorder in the tetrahedral sites. Results of this study will contribute to the correlation of H-bonding geometry and O–H stretching frequencies of highly non-linear H bonds.
    Print ISSN: 0026-461X
    Electronic ISSN: 1471-8022
    Topics: Geosciences
    Published by Mineralogical Society of Great Britain and Ireland
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  • 7
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    Elasticity of franklinite and trends for transition-metal oxide spinels (2013)
    Mineralogical Society of America
    Details
    Publication Date: 2013-03-30
    Description: The pressure dependence of single-crystal elastic moduli of a natural Mn-rich franklinite, (Mn 0.40 Fe 2+ 0.16 Zn 0.37 Mg 0.03 )(Fe 3+ 1.94 Al 0.08 )O 4 , has been determined by GHz-ultrasonic interferometry in a diamond-anvil cell to 9.8 GPa. The room-pressure elastic constants of franklinite are C 11 = 244(3) GPa, C 12 = 142(4) GPa, and C 44 = 77(2) GPa. Linear pressure derivatives of C 11 and C 12 are 4.3(3) and 3.8(3), respectively, whereas the C 44 modulus exhibits softening, fitted in the P ≤ 10 GPa pressure range to C 44 = 77(2) + 0.29(2) P – 0.018(2) P 2 GPa. The average of Hashin-Shtrikman bounds on the adiabatic bulk modulus ( K S0 ) of franklinite is 175(3) GPa, with pressure derivative K S ' = 4.3(3), and the shear modulus G 0 = 66(2) GPa with G ' = 0.09(3). The isothermal compressibility of franklinite was determined from a separate high-pressure, single-crystal X-ray diffraction experiment to 7.8 GPa, yielding K T0 = 173.5(7) GPa fitted with a fixed pressure derivative of K T ' = 4. When K ' is fixed to the ultrasonic value of 4.3, we obtain K T0 = 172.2(7) GPa. In contrast to iron-free gahnite (ZnAl 2 O 4 ), franklinite exhibits pressure-induced mode softening of C 44 similar to magnetite (Fe 3 O 4 ). Between end-member compositions ZnFe 2 O 4 (franklinite) and MnFe 2 O 4 (jacobsite), the bulk modulus decreases linearly with increasing %Mn, however we observe non-linear behavior in other elastic moduli, especially C 44 , which displays a pronounced negative anomaly for the mid-range Mn composition. Applying Birch’s law to AB 2 O 4 -type spinels reveals that oxide spinels containing transition metals on both A and B sites follow a distinct trend from other spinels.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 8
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    High-pressure high-temperature Raman spectroscopy of kerogen: Relevance to subducted organic carbon (2017)
    Mineralogical Society of America
    Details
    Publication Date: 2017-02-02
    Description: The amount of insoluble macromolecular organic matter in the Earth’s crust, commonly referred to as kerogen, far exceeds the mass of living organic matter. The fraction of kerogen in sediments subducted into the mantle remains poorly constrained and will vary depending on the physical-chemical properties of kerogen along different slab geotherms. We studied the pressure-temperature evolution of carbon vibrational frequencies in isolated kerogen, previously not subjected to metamorphism, using Raman spectroscopy in a sapphire optical cell up to 3.2 GPa and 450 °C, corresponding to colder subduction geotherms. For blue-green laser excitation, we find optical irradiance exceeding ~3 kW/cm 2 induces changes in spectral features of the primary graphitic (G-band) and two main disordered modes (D1 and D2) that might otherwise be mistaken for thermal maturation. Whereas previous in situ studies have investigated the changes in these molecular vibrations of kerogen at high temperature or high pressure, we collected Raman spectra of isolated kerogen at simultaneous high P-T conditions. Although instantaneous and irreversible changes in band ratios of isolated kerogen were observed above ~350 °C at room-pressure, long-duration (2–8 h) heating experiments at 450 °C and 2.7–3.0 GPa reveal no permanent change in band structure. The reduction in vibrational frequencies of the disordered carbon modes with temperature (d/d T ) at pressures 〉1 GPa is slightly less than found at room pressure, further indicating that pressure effectively increases the thermal stability of kerogen. Our results suggest that kerogen reaching depths of 60 km where the temperature is below ~450 °C may subduct into the mantle, providing a potential source for the organic-rich component of carbon recently detected in certain lower-mantle diamonds.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 9
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    Transition metals in the transition zone: Crystal chemistry of minor element substitution in wadsleyite (2016)
    Mineralogical Society of America
    Details
    Publication Date: 2016-10-08
    Description: As the most abundant solid phase at depths of 410–525 km, wadsleyite constitutes a large geochemical reservoir in the Earth. To better understand the implications of minor element substitution and cation ordering in wadsleyite, we have synthesized wadsleyites coexisting with pyroxenes with 2–3 wt% of either TiO 2 , Cr 2 O 3 , V 2 O 3 , CoO, NiO, or ZnO under hydrous conditions in separate experiments at 1300 °C and 15 GPa. We have refined the crystal structures of these wadsleyites by single-crystal X-ray diffraction, analyzed the compositions by electron microprobe, and estimated M3 vacancy concentration from b / a cell-parameter ratios. According to the crystal structure refinements, Cr and V show strong preferences for M3 over M1 and M2 sites and significant substitution up to 2.9 at% at the tetrahedral site (T site). Ni, Co, and Zn show site preferences similar to those of Fe with M1 M3 〉 M2 〉 T. The avoidance of Ni, Co, and Fe for the M2 site in both wadsleyite and olivine appears to be partially controlled by crystal field stabilization energy (CFSE). The estimated CFSE values of Ni 2+ , Co 2+ , and Zn 2+ at three distinct octahedral sites show a positive correlation with octahedral occupancy ratios [M2/(M1+M3)]. Ti substitutes primarily into the M3 octahedron, rather than M1, M2, or T sites. Ti, Cr, and V each have greater solubility in wadsleyite than in olivine. Therefore these transition metal cations may be enriched in a melt or an accessory phase if hydrous melting occurs on upward convection across the wadsleyite-olivine boundary and may be useful as indicators of high-pressure origin.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 10
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    High-pressure synthesis of the BiVO3 perovskite (2019)
    American Physical Society
    Details
    Publication Date: 2019-06-20
    Electronic ISSN: 2475-9953
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by American Physical Society
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