Abstract
Single-crystal X-ray structure refinements have been carried out on natural Fe-bearing orthoenstatite (OEN) at pressures up to 14.53 GPa. We report a new high-pressure phase transition from OEN to a monoclinic phase (HPCEN2) with space group P21/c, with a density change of ~1.9(3)%. The HPCEN2 phase is crystallographically different from low-pressure clinoenstatite (LPCEN), which also has P21/c symmetry. Upon release of pressure HPCEN2 reverts to OEN, and the transition pressure is bracketed between 9.96 and 14.26 GPa at room temperature. We find no evidence for a C2/c phase at high pressure. The lattice constants for the new phase at 14.26 GPa are a = 17.87(2), b = 8.526(9), c = 4.9485(10) Å, β = 92.88(4)° [ρ = 3.658(9) g/cm3]. Refinement of the new structure indicates rotation of tetrahedral chain as the key characteristic of this transition. This experiment points to the possibility of OEN and HPCEN2 as the stable phases in Earth’s upper mantle.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Mercury (Hg) mineral evolution: A mineralogical record of supercontinent assembly, changing ocean geochemistry, and the emerging terrestrial biosphere
- The 3.65 Å phase, MgSi(OH)6: Structural insights from DFT-calculations and T-dependent IR spectroscopy
- Vertical zonation of the Barcroft granodiorite, White Mountains, California: Implications for magmatic processes
- Minerals in cement chemistry: A single-crystal neutron diffraction and Raman spectroscopic study of thaumasite, Ca3Si(OH)6(CO3)(SO4)·12H2O
- A new high-pressure phase transition in natural Fe-bearing orthoenstatite
- Aluminum solubility in TiO2 rutile at high pressure and experimental evidence for a CaCl2-structured polymorph
- First record and timing of UHP metamorphism from zircon in the Xitieshan terrane: Implications for the evolution of the entire North Qaidam metamorphic belt
- Lead in zircon at the atomic scale
- Characterization of fluor-chlorapatites by electron probe microanalysis with a focus on time-dependent intensity variation of halogens
- An inversion-based self-calibration for SIMS measurements: Application to H, F, and Cl in apatite
- Second boiling effects on the Al-content of hornblende rims from an exhumed Cretaceous arc pluton, Stewart Island, New Zealand
- Heat transfer in plagioclase feldspars
- Transport properties and equation of state of 1-bar eutectic melt in the system CaAl2Si2O8-CaMgSi2O6 by molecular dynamics simulation
- High-pressure behavior of zoisite
- A first-principle investigation of antigorite up to 30 GPa: Structural behavior under compression
- Reynoldsite, Pb2Mn4+2 O5(CrO4), a new phyllomanganate-chromate from the Blue Bell claims, California and the Red Lead mine, Tasmania
- A new cubic perovskite in PbGeO3 at high pressures
- Manganoquadratite, AgMnAsS3, a new manganese-bearing sulfosalt from the Uchucchacua polymetallic deposit, Lima Department, Peru: Description and crystal structure
- Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron in minerals by PIGE
- Synthetic LiAlGe2O6: The first pyroxene with P21/n symmetry
- Panguite, (Ti4+,Sc,Al,Mg,Zr,Ca)1.8O3, a new ultra-refractory titania mineral from the Allende meteorite: Synchrotron micro-diffraction and EBSD
- Buseckite, (Fe,Zn,Mn)S, a new mineral from the Zakłodzie meteorite
- Experimental calibration of the effect of H2O on plagioclase crystallization in basaltic melt at 200 MPa
- High-pressure and high-temperature titanium solution mechanisms in silicate-saturated aqueous fluids and hydrous silicate melts
- Thermodynamic behavior and properties of katoite (hydrogrossular): A calorimetric study
- Graphite in the martian meteorite Allan Hills 84001