ALBERT

Description:    The D′′ region that lies just above the core mantle boundary exhibits complex anisotropy that this is likely due to preferred orientation (texturing) of the constituent minerals. (Mg,Fe)SiO 3 post-perovskite is widely thought to be the major mineral phase of the D′′. Texture development has been studied in various post-perovskite phases (MgSiO 3 , MgGeO 3 , and CaIrO 3 ), and different results were obtained. To clarify this controversy, we report on transformation and deformation textures in MgGeO 3 post-perovskite synthesized and deformed at room temperature in the diamond anvil cell. Transformed from the enstatite phase, MgGeO 3 post-perovskite exhibits a transformation texture characterized by (100) planes at high angles to the direction of compression. Upon subsequent deformation, this texture changes and (001) lattice planes become oriented nearly perpendicular to compression, consistent with dominant (001)[100] slip. When MgGeO 3 post-perovskite is synthesized from the perovskite phase, a different transformation texture is observed. This texture has (001) planes at high angle to compression and becomes slightly stronger upon compression. We also find that the yield strength of MgGeO 3 post-perovskite is dependent on grain size and texture. Finer-grained samples exhibit higher yield strength and are harder to induce plastic deformation. Strong textures also affect the yield strength and can result in higher differential stresses. The inferred dominant (001) slip for pPv is significant for geophysics, because, when applied to geodynamic convection models, it predicts the observed anisotropies of S-waves as well as an anti-correlation between P- and S-waves. Content Type Journal Article Pages 1-14 DOI 10.1007/s00269-011-0439-y Authors Lowell Miyagi, Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA Waruntorn Kanitpanyacharoen, Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA Stephen Stackhouse, School of Earth and the Environment, University of Leeds, Leeds, LS2 9JT UK Burkhard Militzer, Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA Hans-Rudolf Wenk, Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    We conducted powder neutron diffraction for δ-AlOOH samples with and without Mg and Si ions under ambient conditions in order to investigate the long-standing problem of the symmetry of this phase. The observed reflection conditions clearly show that the space group of pure δ-AlOOH is P 2 1 nm with ordered hydrogen bonds, whereas that of δ-(Al 0.86 Mg 0.07 Si 0.07 )OOH is Pnnm or Pnn2 with disordered hydrogen bonds. It is more likely that the space group of δ-(Al 0.86 Mg 0.07 Si 0.07 )OOH is Pnnm , because cation or hydrogen ordering that breaks the mirror plane perpendicular to c axis in the Pnnm structure would not occur. The previously reported inconsistency for the space group of this phase was caused by the substitution of Mg and Si ions to Al site, i.e., the disordered cations with different valences may fluctuate hydrogen positions, and the disordered hydrogen causes the symmetry change. Content Type Journal Article Pages 1-7 DOI 10.1007/s00269-011-0445-0 Authors K. Komatsu, Geochemical Research Center, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033 Japan A. Sano-Furukawa, High Pressure Science Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan H. Kagi, Geochemical Research Center, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033 Japan Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    We have measured the pressure-induced change in the lattice dynamics of diaspore, α-AlO(OH), by in situ Raman spectroscopy up to 25 GPa. The spectra are evaluated by density functional perturbation theory-based atomistic model calculations. The assignment of calculated to experimentally observed Raman bands is based on the calculation of Raman intensities. We discuss the accuracy of the approach employed for these calculations and explain the relative magnitudes of mode Grüneisen parameters. Content Type Journal Article Pages 1-8 DOI 10.1007/s00269-011-0442-3 Authors Roberto E. San Juan-Farfán, Centro de Investigación Científica y de Educación Superior de Ensenada, Carretera Ensenada-Tijuana No. 3918, C.P. 22860 Ensenada, BC, Mexico Lkhamsuren Bayarjargal, Institut fur Geowissenschaften, Goethe-Universität, Altenhöferallee 1, 60438 Frankfurt a.M., Germany Björn Winkler, Institut fur Geowissenschaften, Goethe-Universität, Altenhöferallee 1, 60438 Frankfurt a.M., Germany Eiken Haussühl, Institut fur Geowissenschaften, Goethe-Universität, Altenhöferallee 1, 60438 Frankfurt a.M., Germany Miguel Avalos-Borja, Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, Km. 107 Carretera Tijuana-Ensenada Apdo. Postal, 356, C.P. 22800 Ensenada, BC, Mexico Keith Refson, Rutherford-Appleton Laboratory, Building R3, Chilton, Didcot, Oxfordshire, OX11 0QX UK Victor Milman, Accelrys, 334 Cambridge Science Park, Cambridge, CB4 0WN UK Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    We used an in situ measurement method to investigate the phase transition of CaGeO 3 polymorphs under high pressures and temperatures. A multi-anvil high-pressure apparatus combined with intense synchrotron X-ray radiation was used. The transition boundary between a garnet and a perovskite phase at T  = 900–1,650 K and P  = 3–8 GPa was determined as occurring at P (GPa) = 9.0−0.0023 ×  T (K). The transition pressure determined in our study is in general agreement with that observed in previous high-pressure experiments. The slope, d P/ d T , of the transition determined in our study is consistent with that calculated from calorimetry data. Content Type Journal Article Pages 1-6 DOI 10.1007/s00269-011-0446-z Authors Shigeaki Ono, Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka-shi, Kanagawa, 237-0061 Japan Takumi Kikegawa, High Energy Acceleration Research Organization, 1-1 Oho, Tsukuba, 305-0801 Japan Yuji Higo, Japan Synchrotron Radiation Research Institute, Sayo-cho, Sayo-gun, Hyogo, 679-5198 Japan Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    The high-pressure structural evolution of hemimorphite, Zn 4 Si 2 O 7 (OH) 2 ·H 2 O, a  = 8.3881(13), b  = 10.7179(11), c  = 5.1311(9) Å, V  = 461.30(12) Å 3 , space group Imm 2, Z  = 2, was studied by single-crystal X-ray diffraction with a diamond anvil cell under hydrostatic conditions up to 4.2 GPa. In the pressure range of 0.0001–2.44 GPa, the unit-cell parameters change almost linearly. The phase transition (probably of the second order) with symmetry reduction from Imm 2 (hemimorphite-I) to Pnn 2 (hemimorphite-II) was found near 2.5 GPa. The structure compressibility increases somewhat above the phase transition. Namely, the initial unit-cell volume decreases by 3.6% at 2.44 GPa and by 7.2% at 4.20 GPa. The hemimorphite framework can be described as built up of secondary building units (SBU) Zn 4 Si 2 O 7 (OH) 2 . These blocks are combined to form the rods arranged along the c -axis; these rods are multiplied by basic and I -translations of orthorhombic unit cell. The symmetry reduction is caused by the rotation of the rods along their axis. In hemimorphite-I, the compression affects mainly the SBU dimensions, whereas a rectangular section of the channels having mm 2 symmetry remains practically unchanged. An appreciable decrease in this section in hemimorphite-II is determined by its oblique distortion with the loss of m planes. It results from opposite rotation of adjacent SBU, which also leads into the loss of I -translation. In hemimorphite-I, the coordination of H 2 O molecules is fourfold planar; the hydrogen-bonded hydroxyls and H 2 O molecules form infinite ribbons along the c -axis. In hemimorphite-II, an additional short H 2 O–O contact appears as a result of asymmetric deformation of the channels. The appearance of this new contact provides the possibility for re-orientation of hydrogen bonds. The planar coordination of H 2 O molecules changes to tetrahedral and the ribbons are transformed to islands (OH) 2 –H 2 O. Content Type Journal Article Pages 1-6 DOI 10.1007/s00269-011-0440-5 Authors Yurii V. Seryotkin, Sobolev Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia Vladimir V. Bakakin, Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    Amorphous ferric iron species (ferrihydrite or akaganeite of 〈5 nm in size) is the only known solid ferric iron oxide that can be reductively transformed by dissimilatory iron-reducing bacteria to magnetite completely. The lepidocrocite crystallite can be transformed into magnetite in the presence of abiotic Fe(II) at elevated pH or biogenic Fe(II) with particular growth conditions. The reduction of lepidocrocite by dissimilatory iron-reducing bacteria has been widely investigated showing varying results. Vali et al. (Proc Natl Acad Sci USA 101:16121–16126, 2004 ) captured a unique biologically mediated mineralization pathway where the amorphous hydrous ferric oxide transformed to lepidocrocite was followed by the complete reduction of lepidocrocite to single-domain magnetite. Here, we report the 57 Fe Mössbauer hyperfine parameters of the time-course samples reported in Vali et al. (Proc Natl Acad Sci USA 101:16121–16126, 2004 ). Both the quadrupole splittings and linewidths of Fe(III) ions decrease consistently with the change of aqueous Fe(II) and transformations of mineral phases, showing the Fe(II)-mediated gradual regulation of the distorted coordination polyhedrons of Fe 3+ during the biomineralization process. The aqueous Fe(II) catalyzes the transformations of Fe(III) minerals but does not enter the mineral structures until the mineralization of magnetite. The simulated abiotic reaction between Fe(II) and lepidocrocite in pH-buffered, anaerobic media shows the simultaneous formation of green rust and its gradual transformation to magnetite plus a small fraction of goethite. We suggested that the dynamics of Fe(II) supply is a critical factor for the mineral transformation in the dissimilatory iron-reducing cultures. Content Type Journal Article Pages 1-8 DOI 10.1007/s00269-011-0443-2 Authors Yi-Liang Li, Department of Earth Sciences, The University of Hong Kong, Pok Fu Lam, Hong Kong San-Yuan Zhu, Department of Earth Sciences, The University of Hong Kong, Pok Fu Lam, Hong Kong Kun Deng, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, China Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    The Raman spectra of bixbyite, Mn 2 O 3 , were measured up to 40 GPa at room temperature. Mn 2 O 3 undergoes a phase transition from the C-type rare earth structure to the CaIrO 3 -type (post-perovskite) structure at 16–25 GPa. The transition pressure measured in Raman spectroscopy is significantly lower than the pressure reported previously by an X-ray diffraction study. This could be due to the greater polarizability in the CaIrO 3 -type structure, consistent with high-pressure observation on the CaIrO 3 type in MgGeO 3 , although it is still possible that experimental differences may cause the discrepancy. Unlike the change at the perovskite to CaIrO 3 -type transition, the spectroscopic Grüneisen parameter does not decrease at the C-type to CaIrO 3 -type transition. The spectroscopic Grüneisen parameter of the low-pressure phase (C type) is significantly lower than thermodynamic Grüneisen parameter, suggesting significant magnetic contributions to the thermodynamic property of this material. Our Raman measurements on CaIrO 3 -type Mn 2 O 3 contribute to building systematic knowledge about this structure, which has emerged as one of the common structures found in geophysically important materials. Content Type Journal Article Pages 1-7 DOI 10.1007/s00269-011-0441-4 Authors S.-H. Shim, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA D. LaBounty, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA T. S. Duffy, Princeton University, Guyot Hall, Princeton, NJ 08544, USA Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    Heat treatment was performed on selected Fe-dominant tourmalines to establish the nature of any change in optical properties. Two tourmaline samples from Dolní Bory, Czech Republic (TDB) and Vlachovo, Slovakia (TVL) were heated at 450, 700 and 900°C at 0.1 mPa and ambient oxidation conditions for 8 h. EMPA study shows that tourmaline from Vlachovo has schorlitic composition and tourmaline from Dolní Bory is alkali-depleted schorl to foitite. Although the black colour remained unchanged after heating at 450°C, it changed to brown at 700°C and reddish brown at 900°C. No significant changes of chemical composition were observed during heating. X-ray diffraction, infrared and Mössbauer study showed negligible oxidation of tourmaline heated at 450°C, but a significant change in iron valency state and deprotonization at 700°C. The oxidation of Fe is the main cause of tourmaline colour change, and the substitution vector for oxidation of Fe is Fe 3+ OFe −1 2+ (OH) −1 . The predicted deprotonization of OH was confirmed by infrared spectroscopy, which documented a decrease in OH groups in both samples, mainly at the V site. The oxidation of Fe is mostly significant in the Y site as documented on the compression of the Y -site octahedra and subsequent decrease in the a lattice parameter. This feature is consistent with lattice dimensions in the transition from schorl and foitite dimensions to those consistent with fluor-buergerite. The Z -site octahedra did not compressed and were not affected by heating-induced Fe oxidation, which indicates only negligible content of Z Fe 2+ in original samples. After heating at 900°C, the tourmaline structure collapsed likely due to the thermally induced weakening of bonds in Y and Z octahedra, which results in amorphization of tourmaline. Subsequently, breakdown products including Fe-oxides and mullite replaced alkali-depleted amorphized tourmaline. Content Type Journal Article Pages 1-13 DOI 10.1007/s00269-011-0432-5 Authors P. Bačík, Faculty of Natural Sciences, Department of Mineralogy and Petrology, Comenius University in Bratislava, Mlynská dolina, 842 15 Bratislava, Slovak Republic D. Ozdín, Faculty of Natural Sciences, Department of Mineralogy and Petrology, Comenius University in Bratislava, Mlynská dolina, 842 15 Bratislava, Slovak Republic M. Miglierini, Department of Nuclear Physics and Technology, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovičova 3, 812 19 Bratislava, Slovak Republic P. Kardošová, Faculty of Natural Sciences, Department of Mineralogy and Petrology, Comenius University in Bratislava, Mlynská dolina, 842 15 Bratislava, Slovak Republic M. Pentrák, Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 36 Bratislava, Slovak Republic J. Haloda, Czech Geological Survey, Geologická 6, 152 00 Praha, Czech Republic Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    Present work provides in-situ structural data at a fine temperature scale from RT to the melting point of nitratine, NaNO 3 . From the analysis of log e 33 versus log t plots, it is possible to prove that an univocal indication on the R 3   c (low temperature, LT) →  R 3   m (high temperature, HT) transition mechanism cannot be obtained because of the relevant role played by the arbitrary assumptions required for defining the c 0 dependence from temperature of the HT phase. This is due to the occurrence of excess thermal expansion for the HT phase. A significantly better fit for an Ising-spin structural model over a non-Ising rigid-body one has been obtained for the LT phase. Moreover, the Ising model led to a smooth variation of the oxygen site x fractional coordinate throughout the transition. The structure of the HT polymorph has been successfully refined considering an oxygen site at x , 0, ½, with 50% occupancy. Such model was the only acceptable one from the crystal chemical point of view as the alternative model (oxygen site at x , y , z with 25% occupancy) led to unrealistically aplanar \text NO 3 - groups. Content Type Journal Article Pages 1-11 DOI 10.1007/s00269-011-0425-4 Authors Paolo Ballirano, Dipartimento di Scienze della Terra, Sapienza Università degli Studi di Roma, P.le Aldo Moro 5, 00185 Rome, Italy Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791

Description:    Purified natural clinoptilolite from the Tasajeras deposit, Cuba, and some of its metal exchanged forms are studied, at the dehydrated state, by means of dielectric relaxation spectroscopy (DRS) using two different modus operandi: complex impedance spectroscopy and dielectric dynamic thermal analysis. Data analysis yields the determination of the extra-framework cation (EFC) population into the various possible crystallographic sites of the zeolitic framework as well as of the activation energy characterizing the localized hopping mechanism of EFC. First, it is shown that the DRS responses obtained here match well with the previous reported data, which were previously localized EFCs in positions close to M1 and M2 sites when the clinoptilolite is modified to almost homoionic form. From this outcome, it can be concluded that all EFCs are in the same crystallographic situation regarding solvation or, in other terms, that no steric effect can be taken into account to explain cationic selectivity. Second, based on the assumption that the activation energy for EFC hopping is directly connected to the EFC/framework interaction and on simple thermodynamics consideration, we show this interaction does not govern the EFC exchange reaction. So, it is emphasized that EFC/H 2 O interaction is the key factor for cation exchange selectivity. Content Type Journal Article Pages 1-9 DOI 10.1007/s00269-011-0433-4 Authors Gerardo Rodríguez-Fuentes, Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, Zapata y G s/n, Vedado, 10400 La Habana, Cuba Sabine Devautour-Vinot, Equipe Physicochimie des Matériaux Désordonnés et Poreux, Institut Charles Gerhardt, UMR 5253 CNRS, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France Sekou Diaby, Laboratoire de Chimie-Physique, UFR-SSMT (Unité de Formation et de Recherche en Sciences des Structures de la Matière et Technologie), Université de Cocody-Abidjan, 22 BP 582 Abidjan 22, Côte d’Ivoire François Henn, Equipe Physicochimie des Matériaux Désordonnés et Poreux, Institut Charles Gerhardt, UMR 5253 CNRS, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France Journal Physics and Chemistry of Minerals Online ISSN 1432-2021 Print ISSN 0342-1791