Abstract
The equilibrium intracrystalline distribution of Mn and Mg between the M1 and M2 sites of a Mn-rich/Fe-free orthopyroxene (donpeacorite) was investigated by means of annealing experiments at temperatures between 980 and 800 °C and single-crystal X-ray diffraction. The data show that Mn, as does Fe2+ in Fe-Mg orthopyroxene, preferentially orders at the M2 site. However, comparison of the distribution coefficient kD(Mn-Mg) determined in this study with kD+ measured for Fe-Mg orthopyroxene shows that Mn has a much stronger preference for the M2 site relative to Fe2+. This result implies that the practice to partition Fe2+ + Mn = Fe* as one species, typically implemented to determine the quenched-site occupancies in Fe-rich/Mn-poor orthopyroxene, should be abandoned and that Mn should be considered totally ordered at M2. The partitioning method, i.e., Fe vs. Fe*, has implications for the determination of cooling rates from the observed ordering state of orthopyroxene, particularly for Fe-poor compositions (Fs < 0.16).
© 2015 by Walter de Gruyter Berlin/Boston
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Artikel in diesem Heft
- Contact metamorphism of the White Mountain Peak metavolcanic complex, eastern California
- Structure and luminescence characteristics of quartz from pegmatites
- Evidence for monazite-, barite-, and AgMnO4 (distorted barite)-type structures of CaSO4 at high pressure and temperature
- The “template” effect of the extra-framework content on zeolite compression: The case of yugawaralite
- The influence of OH in coesite on the kinetics of the coesite-quartz phase transition
- First-principles study of hydrogen bond symmetrization of phase D under high pressure
- First-principles study of OH-stretching modes in kaolinite, dickite, and nacrite
- A systematic study of OH in hydrous wadsleyite from polarized FTIR spectroscopy and single-crystal X-ray diffraction: Oxygen sites for hydrogen storage in Earthʼs interior
- Determination of the content and distribution of fixed ammonium in illite-smectite using a modified X-ray diffraction technique: Application to oil source rocks of western Greenland
- Determination of defect structures in kaolin minerals by high-resolution transmission electron microscopy (HRTEM)
- Mössbauer spectroscopy of omphacite and garnet pairs from eclogites: Application to geothermobarometry
- Allanite and epidote weathering at the Coweeta Hydrologic Laboratory, western North Carolina, U.S.A.
- Ca2SiO3OHFA high-pressure phase with dense calcium polyhedral packing and tetrahedral silicon
- Relationships between SEM-cathodoluminescence response and trace-element composition of hydrothermal vein quartz
- Quantitative evaluation of attenuation contrast of X-ray computed tomography images using monochromatized beams
- Biotic and abiotic products of Mn(II) oxidation by spores of the marine Bacillus sp. strain SG-1
- The Mn, Mg-intracrystalline exchange reaction in donpeacorite (Mn0.54Ca0.03Mg1.43Si2O6) and its relation to the fractionation behavior of Mn in Fe, Mg-orthopyroxene
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- Dehydroxylation and CO2 incorporation in annealed mica (sericite): An infrared spectroscopic study
- Relict coesite exsolution in omphacite from Western Tianshan eclogites, China
- Hyperfine electric field gradients and local distortion environments of octahedrally coordinated Fe2+
- A synchrotron Mössbauer spectroscopy study of (Mg,Fe)SiO3 perovskite up to 120 GPa
- Temporal stability and pressure calibration of barium carbonate and talc/pyrex pressure media in a piston-cylinder apparatus
- Cation ordering in magnesioferrite, MgFe2O4, to 982 °C using in situ synchrotron X-ray powder diffraction
- Halite-sylvite thermoconsolution
- The role of water in the structures of synthetic hallimondite, Pb2[(UO2)(AsO4)2](H2O)n and synthetic parsonsite, Pb2[(UO2)(PO4)2](H2O)n, 0 ≤ n ≤ 0.5
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