Note: This page contains sample records for the topic olivines limnpo4 lifepo4 from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Comparison of small polaron migration and phase separation in olivine LiMnPO4 and LiFePO4 using hybrid density functional theory  

NASA Astrophysics Data System (ADS)

Using hybrid density functional theory based on the Heyd-Scuseria-Ernzerhof (HSE06) functional, we compared polaron migration and phase separation in olivine LiMnPO4 to LiFePO4. The barriers for free hole and electron polaron migration in the Mn olivine system are calculated to be 303 and 196 meV, respectively, significantly higher than the corresponding barriers of 170 and 133 meV, respectively, for the Fe olivine system, in agreement with previous experimental findings. These results suggest that the electronic conductivities of LiMnPO4 and MnPO4 are about 177 and 11 times lower than their respective Fe analogs at room temperature. In the presence of lithium vacancies or ions, the barriers for both hole and electron polaron migration were found to be about 100-120 meV higher in the Mn olivine. The HSE06 functional, with its more universal treatment of self-interaction error, was found to be essential to the proper localization of a polaron in the Mn olivine but predicted qualitatively incorrect phase separation behavior in the LixFePO4 system.

Ong, Shyue Ping; Chevrier, Vincent L.; Ceder, Gerbrand

2011-02-01

2

Facile synthesis of LiMnPO4 olivines with a plate-like morphology from a dittmarite-type KMnPO4·H2O precursor.  

PubMed

Dittmarite-type compound KMnPO(4)·H(2)O was used as a new precursor for the synthesis of nanostructured LiMnPO(4) phospho-olivines with a plate-like morphology at low temperature (about 200 °C) and a short reaction time (90-180 min). The dehydration of KMnPO(4)·H(2)O was studied by DTA and TG analysis. Structural and morphological characterization of both KMnPO(4)·H(2)O and LiMnPO(4) was performed by powder XRD, SEM and TEM analyses. The formation of nanostructured LiMnPO(4) was examined by electron paramagnetic resonance spectroscopy and TEM. It was found that the reaction between KMnPO(4)·H(2)O with the LiCl-LiNO(3) mixture includes a fast ionic exchange of K(+) with Li(+) in the framework of the dittmarite structure, followed by H(2)O release and the formation of the olivine-type structure. The morphology and texture of the dittmarite-type precursor results in a plate-like morphology of LiMnPO(4) with a preferred orientation along the [100] direction. The plate-like morphology of LiMnPO(4) is stable after annealing at 500 °C. The plates are composed of nanocrystallites, with various sizes in the range 10-20 nm. The EPR signal of LiMnPO(4) is due to the exchange-coupled Mn(2+) ions. It was demonstrated that the EPR line-width correlates with the Scherrer crystallite size. PMID:21681329

Koleva, Violeta; Zhecheva, Ekaterina; Stoyanova, Radostina

2011-06-17

3

Synthesis of Highly Crystalline Olivine-Type LiFePO4 Nanoparticles by Solution-Based Reactions  

Microsoft Academic Search

LiFePO4 nanocrystals were synthesized in various polyol media without any further post-heat treatment. The LiFePO4 samples synthesized using three different polyol media namely, diethylene glycol (DEG), triethylene glycol (TEG), and tetraethylene glycol (TTEG), exhibited plate and rod-shaped structures with average sizes of 50-500 nm. The X-ray diffraction (XRD) patterns were indexed on the basis of an olivine structure (space group:

Donghan Kim; Jinsub Lim; Eunseok Choi; Jihyeon Gim; Vinod Mathew; Younkee Paik; Hongryun Jung; Wanjin Lee; Docheon Ahn; Seungmin Paek; Jaekook Kim

2010-01-01

4

Raman spectroscopy of carbon-coated LiCoPO 4 and LiFePO 4 olivines  

Microsoft Academic Search

The effect of laser power on the Raman spectra of two carbon-coated nano-powders of LiCoPO4 and LiFePO4 olivine cathode materials were investigated. In the ambient atmosphere at a moderate laser power, the phenomenon of the removal of the carbon coating layer from both samples was detected. The olivine structure of LiCoPO4-C powder therefore remains unchanged during the prolonged exposure to

E. Markevich; R. Sharabi; O. Haik; V. Borgel; G. Salitra; D. Aurbach; G. Semrau; M. A. Schmidt; N. Schall; C. Stinner

2011-01-01

5

Crystal structure and lithium electrochemical extraction properties of olivine type LiFePO 4  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) cathode material has been synthesized by a solid-state reaction. The XRD patterns and SEM images of the samples show that the LiFePO4 compounds prepared at 650°C by using carbon gel in reaction have a single-phase, small grain-size and regular shapes. By using Rietveld refinement method, we calculated the Li–O interatomic distance in LiO6 octahedra and the

Y. Z. Dong; Y. M. Zhao; H. Duan

2011-01-01

6

Enhancing the electrochemical kinetics of high voltage olivine LiMnPO4 by isovalent co-doping.  

PubMed

We report here doping of Fe(2+) and/or Mg(2+) in LiMnPO4 cathode material to enhance its lithium storage performance and appraise the effect of doping. For this purpose, LiMn0.9Fe(0.1-x)MgxPO4/C (x = 0 and 0.05) and LiMn0.95Mg0.05PO4/C have been prepared by a ball mill assisted soft template method. These materials were prepared with similar morphology, particle size and carbon content. Amongst them, the isovalent co-doped LiMn0.9Fe0.05Mg0.05PO4/C sample shows better electrochemical performance compared to LiMn0.9Fe0.1PO4/C and LiMn0.95Mg0.05PO4/C samples. For instance, a lithium storage capacity of 159 mA h g(-1) is obtained at 0.1 C for LiMn0.9Fe0.05Mg0.05PO4/C material with a relatively low polarization of ?139 mV. This is in sharp contrast to LiMn0.9Fe0.1PO4/C and LiMn0.95Mg0.05PO4/C which show only 136.8 and 128.4 mA h g(-1) at 0.1 C with the polarization of ?222 and 334 mV respectively. Further, the LiMn0.9Fe0.05Mg0.05PO4/C electrode delivers discharge capacities of 155.8, 141.4, 118.8, 104.6, 81.4 and 51.8 mA h g(-1) at 0.2, 0.5, 1, 2, 5 and 10 C respectively. This electrode material also retains a capacity of 116 mA h g(-1) at 1 C after 200 cycles, which is 96% of its initial capacity. Such improved cycling stability of LiMn0.9Fe0.05Mg0.05PO4/C is attributed to the suppressed Mn dissolution in the electrolyte compared to the other samples. Further, during the Li extraction process, delithiated phases created from the Fe(2+)/Fe(3+) redox reaction (?3.45 V) favor enhanced electrochemical activity of the succeeding Mn(2+)/Mn(3+) redox couples. The fully charged state (4.6 V) contains a partially lithiated phase owing to the presence of electrochemically inactive Mg(2+). The presence of such lithiated phase provides a favourable environment for the subsequent lithium insertion process. We also observe improved electronic conductivity and Li-ion diffusion for the co-doped sample compared to LiMnPO4 doped with either Fe(2+) or Mg(2+) by impedance measurements. The improved storage performance of co-doped LiMnPO4 is thus explained in terms of (i) favorable extraction and insertion reactions and (ii) enhanced transport properties. PMID:24018895

Ramar, Vishwanathan; Balaya, Palani

2013-09-25

7

Comparison of electrochemical performances of olivine NaFePO4 in sodium-ion batteries and olivine LiFePO4 in lithium-ion batteries.  

PubMed

Carbon-coated olivine NaFePO(4) (C-NaFePO(4)) spherical particles with a uniform diameter of ?80 nm are obtained by chemical delithiation and subsequent electrochemical sodiation of carbon-coated olivine LiFePO(4) (C-LiFePO(4)), which is synthesized by a solvothermal method. The C-NaFePO(4) electrodes are identical (particle size, particle size distribution, surface coating, and active material loading, etc.) to C-LiFePO(4) except that Li ions in C-LiFePO(4) are replaced by Na ions, making them ideal for comparison of thermodynamics and kinetics between C-NaFePO(4) cathode in sodium-ion (Na-ion) batteries and C-LiFePO(4) in lithium-ion (Li-ion) batteries. In this paper, the equilibrium potentials, reaction resistances, and diffusion coefficient of Na in C-NaFePO(4) are systematically investigated by using the galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and compared to those of the well-known LiFePO(4) cathodes in Li-ion batteries. Due to the lower diffusion coefficient of Na-ion and higher contact and charge transfer resistances in NaFePO(4) cathodes, the rate performance of C-NaFePO(4) in Na-ion batteries is much worse than that of C-LiFePO(4) in Li-ion batteries. However, the cycling stability of C-NaFePO(4) is almost comparable to C-LiFePO(4) by retaining 90% of its capacity even after 100 charge-discharge cycles at a charge-discharge rate of 0.1 C. PMID:23235803

Zhu, Yujie; Xu, Yunhua; Liu, Yihang; Luo, Chao; Wang, Chunsheng

2012-12-12

8

Coupling of Li motion and structural distortions in olivine LiMnPO4 from 7Li and 31P NMR  

NASA Astrophysics Data System (ADS)

We present a detailed 7Li- and 31P-NMR study on single crystalline LiMnPO4 in the paramagnetic and antiferromagnetic phase (AFM, TN˜34 K). This allows us to determine the spin directions in the field-induced spin-flop phase. In addition, the anisotropic dipolar hyperfine coupling tensor of the 7Li and 31P nuclei is also fully determined by orientation and temperature-dependent NMR experiments and compared to the calculated values from crystal structure data. Deviations of the experimental values from the theoretical ones are discussed in terms of Mn disorder which is induced by Li disorder. In fact, the disorder in the Mn sublattice is directly revealed by diffuse x-ray scattering data. The present results provide experimental evidence for the Li diffusion strongly coupling to structural distortions within the MnPO4 host, which is expected to significantly affect the Li mobility as well as the performance of batteries based on this material.

Rudisch, Christian; Grafe, Hans-Joachim; Geck, Jochen; Partzsch, Sven; Zimmermann, M. v.; Wizent, Nadja; Klingeler, Rüdiger; Büchner, Bernd

2013-08-01

9

Thin film rechargeable electrodes based on conductive blends of nanostructured olivine LiFePO4 and sucrose derived nanocarbons for lithium ion batteries.  

PubMed

The present study provides the first reports of a novel approach of electrophoretic co-deposition technique by which titanium foils are coated with LiFePO4-carbon nanocomposites synthesized by sol gel route and processed into high-surface area cathodes for lithium ion batteries. The study elucidates how sucrose additions as carbon source can affect the surface morphology and the redox reaction behaviors underlying these cathodes and thereby enhance the battery performance. The phase and morphological analysis were done using XRD and XPS where the LiFePO4 formed was confirmed to be a high purity orthorhombic system. From the analysis of the relevant electrochemical parameters using cyclic voltammetry and electrochemical impedance spectroscopy, a 20% increment and 90% decrement in capacity and impedance values were observed respectively. The composite electrodes also exhibited a specific capacity of 130 mA h/g. It has been shown that cathodes based on such composite systems can allow significant room for improvement in the cycling performance at the electrode/electrolyte interface. PMID:23882803

Praveen, P; Jyothsna, U; Nair, Priya; Ravi, Soumya; Balakrishnan, A; Subramanian, K R V; Nair, A Sreekumaran; Nair, V Shantikumar; Sivakumar, N

2013-08-01

10

A study on the electrochemical characteristics of LiFePO 4 cathode for lithium polymer batteries by hydrothermal method  

Microsoft Academic Search

Phospho-olivine LiFePO4 cathode materials were prepared by hydrothermal reaction at 150°C. Carbon black was added to enhance the electrical conductivity of LiFePO4. LiFePO4-C powders (0, 3, 5 and 10wt.%) were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). LiFePO4-C\\/solid polymer electrolyte (SPE)\\/Li cells were characterized electrochemically by charge\\/discharge experiments at a constant current density of 0.1mAcm?2 in a

En Mei Jin; Bo Jin; Dae-Kyoo Jun; Kyung-Hee Park; Hal-Bon Gu; Ki-Won Kim

2008-01-01

11

An optimized Ni doped LiFePO 4\\/C nanocomposite with excellent rate performance  

Microsoft Academic Search

Both Ni doping and carbon coating are adopted to synthesize a nano-sized LiFePO4 cathode material through a simple solid-state reaction. It is found that the Ni2+ has been successfully doped into LiFePO4 without affecting the phospho-olivine structure from the XRD result. The images of SEM and TEM show that the size of particles is distributed in the range of 20–60nm,

Yucui Ge; Xuedong Yan; Jing Liu; Xianfa Zhang; Jiawei Wang; Xingguang He; Rongshun Wang; Haiming Xie

2010-01-01

12

Doping effects of zinc on LiFePO 4 cathode material for lithium ion batteries  

Microsoft Academic Search

Alien atom doping has been adopted to modify the electrochemical performance of olivine type LiFePO4 for cathode material of the lithium ion batteries. Here, we first report that zinc-doping can improve the performance of LiFePO4. The effects of zinc-doping have been studied by the measurements of X-ray diffraction pattern, scanning electronic microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The results

H. Liu; Q. Cao; L. J. Fu; C. Li; Y. P. Wu; H. Q. Wu

2006-01-01

13

Low-temperature synthesis of LiFePO4 nanocrystals by solvothermal route  

PubMed Central

LiFePO4 nanocrystals were synthesized at a very low temperature of 170°C using carbon nanoparticles by a solvothermal process in a polyol medium, namely diethylene glycol without any heat treatment as a post procedure. The powder X-ray diffraction pattern of the LiFePO4 was indexed well to a pure orthorhombic system of olivine structure (space group: Pnma) with no undesirable impurities. The LiFePO4 nanocrystals synthesized at low temperature exhibited mono-dispersed and carbon-mixed plate-type LiFePO4 nanoparticles with average length, width, and thickness of approximately 100 to 300 nm, 100 to 200 nm, and 50 nm, respectively. It also appeared to reveal considerably enhanced electrochemical properties when compared to those of pristine LiFePO4. These observed results clearly indicate the effect of carbon in improving the reactivity and synthesis of LiFePO4 nanoparticles at a significantly lower temperature.

2012-01-01

14

Physical and electrochemical characterizations of LiFePO 4 -incorporated Ag nanoparticles  

Microsoft Academic Search

Olivine-type LiFePO4 composite materials for cathode material of the lithium-ion batteries were synthesized by using a sol-gel method and were\\u000a coated by a chemical deposition of silver particles. As-obtained LiFePO4\\/C-Ag (2.1 wt.%) composites were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD),\\u000a conductivity measurements, cyclic voltammetry, as well as galvanostatic measurements. The results revealed that the discharge\\u000a capacity of

Zhaolin Liu; Siok Wei Tay; Liang Hong; Jim Yang Lee

2011-01-01

15

Olivine-type nanosheets for lithium ion battery cathodes.  

PubMed

Olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) has become of great interest as cathodes for next-generation high-power lithium-ion batteries. Nevertheless, this family of compounds suffers from poor electronic conductivities and sluggish lithium diffusion in the [010] direction. Here, we develop a liquid-phase exfoliation approach combined with a solvothermal lithiation process in high-pressure high-temperature (HPHT) supercritical fluids for the fabrication of ultrathin LiMPO4 nanosheets (thickness: 3.7-4.6 nm) with exposed (010) surface facets. Importantly, the HPHT solvothermal lithiation could produce monodisperse nanosheets while the traditional high-temperature calcination, which is necessary for cathode materials based on high-quality crystals, leads the formation of large grains and aggregation of the nanosheets. The as-synthesized nanosheets have features of high contact area with the electrolyte and fast lithium transport (time diffusion constant in at the microsecond level). The estimated diffusion time for Li(+) to diffuse over a [010]-thickness of <5 nm (L) was calculated to be less than 25, 2.5, and 250 ?s for LiFePO4, LiMnPO4, and LiCoPO4 nanosheets, respectively, via the equation of t = L(2)/D. These values are about 5 orders of magnitude lower than the corresponding bulk materials. This results in high energy densities and excellent rate capabilities (e.g., 18 kW kg(-1) and 90 Wh kg(-1) at a 80 C rate for LiFePO4 nanosheets). PMID:23713414

Rui, Xianhong; Zhao, Xiaoxu; Lu, Ziyang; Tan, Huiteng; Sim, Daohao; Hng, Huey Hoon; Yazami, Rachid; Lim, Tuti Mariana; Yan, Qingyu

2013-05-30

16

Nanocrystalline LiMnPO 4 prepared by a new phosphate–formate precursor method  

Microsoft Academic Search

The preparation of homogeneous phosphate–formate precursors by freeze-drying of solutions containing lithium, Mn(II), phosphate and formate ions ensures production of stoichiometric, well crystallized, defectless and nano-sized LiMnPO4 powders at temperatures above 400°C. A systematic study of the influence of the synthesis conditions on the structure and morphology of LiMnPO4 is performed. It is established that the concentration of the solutions

V. Koleva; R. Stoyanova; E. Zhecheva

2010-01-01

17

LiFePO4 Cathode Materials for Lithium-ion Batteries  

Microsoft Academic Search

Research progress in recent years on the preparation, modification, how to control crystal size, relationship between structure and performance, and prospect of olivine-type lithium iron phosphate LiFePO4 cathode materials for the lithium-ion batteries was reviewed. Particle size and its distribution, ionic and electronic conductivity, and the content of Fe( ) have much effect on the performance of the samples. The

Lü Zhengzhong; Zhou Zhentao

18

Temperature Dependence of Aliovalent-vanadium Doping in LiFePO4 Cathodes  

SciTech Connect

Vanadium-doped olivine LiFePO4 cathode materials have been synthesized by a novel low-temperature microwave-assisted solvothermal (MW-ST) method at 300 oC. Based on chemical and powder neutron/X-ray diffraction analysis, the compositions of the synthesized materials were found to be LiFe1-3x/2Vx x/2PO4 (0 x 0.2) with the presence of a small number of lithium vacancies charge-compensated by V4+, not Fe3+, leading to an average oxidation state of ~ 3.2+ for vanadium. Heating the pristine 15 % V-doped sample in inert or reducing atmospheres led to a loss of vanadium from the olivine lattice with the concomitant formation of a Li3V2(PO4)3 impurity phase; after phase segregation, a partially V-doped olivine phase remained. For comparison, V-doped samples were also synthesized by conventional ball milling and heating, but only ~ 10 % V could be accommodated in the olivine lattice in agreement with previous studies. The higher degree of doping realized with the MW-ST samples demonstrates the temperature dependence of the aliovalent-vanadium doping in LiFePO4.

Harrison, Katharine L [University of Texas at Austin; Bridges, Craig A [ORNL; Paranthaman, Mariappan Parans [ORNL; Idrobo Tapia, Juan C [ORNL; Manthiram, Arumugam [University of Texas at Austin; Goodenough, J. B. [University of Texas at Austin; Segre, C [Illinois Institute of Technology; Katsoudas, John [Illinois Institute of Technology; Maroni, V. A. [Argonne National Laboratory (ANL)

2013-01-01

19

Atomic-scale visualization of antisite defects in LiFePO4.  

PubMed

We visualize the antisite exchange defects in LiFePO4 crystals with an ordered olivine structure by using annular dark-field scanning transmission electron microscopy (STEM). A recognizable bright contrast is observed in some of the Li columns of STEM images in a sample annealed at a lower temperature, which directly demonstrates the disordered occupations by Fe atoms. Furthermore, such exchange defects appear to be locally aggregated rather than homogeneously dispersed in the lattice, although their overall concentration is fairly low. The present study emphasizes the significance of atomic-level observations for the defect distribution that cannot be predicted by macroscopic analytical methods. PMID:18517881

Chung, Sung-Yoon; Choi, Si-Young; Yamamoto, Takahisa; Ikuhara, Yuichi

2008-03-26

20

Atomic-Scale Visualization of Antisite Defects in LiFePO4  

NASA Astrophysics Data System (ADS)

We visualize the antisite exchange defects in LiFePO4 crystals with an ordered olivine structure by using annular dark-field scanning transmission electron microscopy (STEM). A recognizable bright contrast is observed in some of the Li columns of STEM images in a sample annealed at a lower temperature, which directly demonstrates the disordered occupations by Fe atoms. Furthermore, such exchange defects appear to be locally aggregated rather than homogeneously dispersed in the lattice, although their overall concentration is fairly low. The present study emphasizes the significance of atomic-level observations for the defect distribution that cannot be predicted by macroscopic analytical methods.

Chung, Sung-Yoon; Choi, Si-Young; Yamamoto, Takahisa; Ikuhara, Yuichi

2008-03-01

21

Physical and electrochemical properties of La-doped LiFePO 4 \\/C composites as cathode materials for lithium-ion batteries  

Microsoft Academic Search

Olivine-type LiFePO4 is one of the most promising cathode materials for lithium-ion batteries, but its poor conductivity and low lithium-ion diffusion\\u000a limit its practical application. The electronic conductivity of LiFePO4 can be improved by carbon coating and metal doping. A small amount of La-ion was added via ball milling by a solid-state\\u000a reaction method. The samples were characterized by X-ray

Yung-Da Cho; George Ting-Kuo Fey; Hsien-Ming Kao

2008-01-01

22

Kinetics of lithium deintercalation from LiFePO 4  

Microsoft Academic Search

We have studied the kinetics of lithium deintercalation from lithium iron phosphate in a cathode material for batteries. The\\u000a main contribution to the resistance of the cell is made by interfaces and the resistance of LiFePO4 grains. The FePO4 solubility in LiFePO4 is 4.0%. The lithium deintercalation process can be described in terms of a heterogeneous grain model and its

D. V. Safronov; I. Yu. Pinus; I. A. Profatilova; V. A. Tarnopol’skii; A. M. Skundin; A. B. Yaroslavtsev

2011-01-01

23

Electrochemical properties of carbon coated LiFePO 4 cathode materials  

Microsoft Academic Search

Carbon coated lithium iron phosphates were prepared by a carbon aerogel synthesis process, through which LiFePO4 particles were embedded in amorphous carbon. The carbon coating effect can significantly enhance the electronic conductivity of LiFePO4. The electrochemical properties of the as-prepared LiFePO4 cathode materials were systematically characterised. The carbon coated LiFePO4 cathode demonstrated a high capacity and stable cyclability.

G. X. Wang; L. Yang; S. L. Bewlay; Y. Chen; H. K. Liu; J. H. Ahn

2005-01-01

24

Preparation and characterization of Ti 4+-doped LiFePO 4 cathode materials for lithium-ion batteries  

Microsoft Academic Search

Olivine structured LiFePO4 (lithium iron phosphate) and Ti4+-doped LiFe1?xTixPO4 (0.01?x?0.09) powders were synthesized via a solution route followed by heat-treatment at 700°C for 8h under N2 flowing atmosphere. The compositions, crystalline structure, morphology, carbon content, and specific surface area of the prepared powders were investigated with ICP-OES, XRD, TEM, SEM, EA, and BET. Capacity retention study was used to investigate

She-huang Wu; Mao-Sung Chen; Chao-Jung Chien; Yen-Pei Fu

2009-01-01

25

Synthesis and characterization of LiFePO 4 \\/3-dimensional carbon nanostructure composites as possible cathode materials for Li-ion batteries  

Microsoft Academic Search

Composites of three-dimensional (3D) carbon nanostructures coated with olivine-structured lithium iron phosphates (LiFePO4) as cathode materials for lithium ion batteries have been prepared through a Pechini-assisted reversed polyol process for\\u000a the first time. The coating has been successfully performed on nonfunctionalized commercially available 3D carbon used as\\u000a catalysts. Thermal analysis revealed no phase transitions till crystallization occurred at 579 °C. Morphological

Lucangelo Dimesso; Christina Spanheimer; Susanne Jacke; Wolfram Jaegermann

2011-01-01

26

Hydrothermal synthesis of LiFePO 4 with small particle size and its electrochemical properties  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) powders were prepared by hydrothermal reactions under a nitrogen atmosphere or an air atmosphere, and the microstructure\\u000a and electrochemical properties of the LiFePO4 powders were investigated. The LiFePO4 powder prepared under the nitrogen atmosphere (LiFePO4–N2) had a small particle size in the range of 300–500 nm, whereas the powder prepared under the air atmosphere (LiFePO4?air) had a

Akira Kuwahara; Shinya Suzuki; Masaru Miyayama

2010-01-01

27

Effect of synthesizing method on the properties of LiFePO4/C composite for rechargeable lithium-ion batteries  

NASA Astrophysics Data System (ADS)

Olivine-type LiFePO4/C cathode materials are fabricated with FePO4 powders that are pre-synthesized by two different processes from iron chloride solution. Process I is a modified precipitation method which is implemented by the pH control of a solution using NH4OH to form FePO4 precipitates at room temperature. Process II is a conventional precipitation method, of which H3PO4 (85%) solution is gradually added to a FeCl3 solution during the process to maintain a designated mole ratio. The solution is subsequently aged at 90°C in a water bath until FePO4 precipitates appear. In order to synthesize LiFePO4/C composites, each batch of FePO4 powders is then mixed with pre-milled lithium carbonate and glucose (8 wt. %) as a carbon source in a ball-mill. The structural characteristics of both LiFePO4/C composites fabricated using iron phospates from two different routes have been examined employing XRD and SEM. The modified precipitation process is considered to be a relatively simple and effective process for the preparation of LiFePO4/C composites owing to their excellent electrochemical properties and rate capabilities.

Yoon, Man-Soon; Islam, Mobinul; Park, Young Min; Ur, Soon-Chul

2013-03-01

28

LiMnPO4 Nanoplate Grown via Solid-State Reaction in Molten Hydrocarbon for Li-ion Battery Cathode  

SciTech Connect

Electrochemically active LiMnPO4 nanoplates have been synthesized via novel single step solid state reaction in molten hydrocarbon. The LiMnPO4 prepared show unique porous nanoplate shape ~50nm in thickness with highly preferred crystallographic orientation. The reversible cycling of carbon coated LiMnPO4 show flat potential at 4.1 V vs. Li with specific capacity reaching up to 168mAh/g and excellent cycling performance using only galvanostatic charging / discharging mode.

Choi, Daiwon; Wang, Donghai; Bae, In-Tae; Xiao, Jie; Nie, Zimin; Wang, Wei; Viswanathan, Vilayanur V.; Lee, Yun Jung; Zhang, Jiguang; Graff, Gordon L.; Yang, Zhenguo; Liu, Jun

2010-08-11

29

The effects of calcination temperature on the electrochemical performance of LiMnPO 4 prepared by ultrasonic spray pyrolysis  

Microsoft Academic Search

Carbon-coated LiMnPO4 powders were prepared by ultrasonic spray pyrolysis. The effects of calcination temperature on the microstructure and electrochemical performance of C-LiMnPO4 were investigated. X-ray diffraction (XRD) studies showed that the crystallite size varied with calcination temperature. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that the calcination temperature had a strong influence on the morphology of

Seung-Min Oh; Sung Woo Oh; Seung-Taek Myung; Sung-Man Lee; Yang-Kook Sun

2010-01-01

30

Synthesis, crystal structure, and electrode characteristics of LiMnPO4(OH) cathode for lithium batteries  

NASA Astrophysics Data System (ADS)

The electrochemical properties of lithium manganese hydroxyphosphate, LiMnPO4(OH), with the tavorite structure have been investigated to assess its suitability as a cathode material for lithium batteries. Stoichiometric LiMnPO4(OH) was synthesized by an ion-exchange reaction with MnPO4·H2O and LiNO3. Lithium (de)intercalation reaction was observed for the first time in the trivalent LiMnPO4(OH), and it exhibited a reversible capacity of 110 mA h g-1 with an average cell voltage of 3.4 V (vs. Li) after an irreversible phase change during the first charge process. The crystal structure has been refined at room temperature by neutron and synchrotron X-ray diffraction data using Rietveld method with a space group of P-1. The hydroxy group at a bottleneck may reduce the attraction force between lithium and the bottleneck oxygen ions that thus increase the ion mobility along the lithium diffusion tunnel.

Yang, Yang; Hirayama, Masaaki; Yonemura, Masao; Kanno, Ryoji

2012-03-01

31

Carbon nanotube and graphene nanosheet co-modified LiFePO4 nanoplate composite cathode material by a facile polyol process  

NASA Astrophysics Data System (ADS)

LiFePO4 nanoplate based composite cathode materials with 5 wt% multi-walled carbon nanotubes and 1 wt% graphene nanosheets have been prepared via a single-step polyol process under low temperature, without using any inert gas input and post heat treatments. The carbon nanotubes have been embedded into the inside of LiFePO4 nanoplates, whilst graphene nanosheets have been coated on the surface, and both carbon additives have interlaced to form a crosslinked three-dimensional mixed conducting network, to assist the charge transfer throughout the inside and outside of cathode materials. The structural and morphological properties of the nanocomposites have been investigated by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The electrochemical properties have been studied by charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. Both pristine LiFePO4 nanoplate and the nanocomposites display an orthorhombic olivine-type structure. The nanocomposites present excellent electrochemical performance with a reversible specific capacity of 166 mAh g-1 at the current rate of 10 mA g-1, and a capacity retention ratio close to 100% after 100 cycles.

Wu, Guan; Zhou, Yingke; Shao, Zongping

2013-10-01

32

Electrochemical Performances of LiMnPO4 Synthesized from Non-Stoichiometric Li/Mn Ratio  

SciTech Connect

In this paper we report the influences of the initial lithium content on the structural, electrochemical and magnetic properties of nonstoichiometric LixMnPO4 (0.5?x?1.2) nano-particles. It has been revealed Mn2P2O7 is the main impurity when Li<1.0 while Li3PO4 begins to form once x>1.0. The different functions of Mn2P2O7 and Li3PO¬4 impurities in the non-stoichiometric compounds have been investigated systematically. At a slow rate of C/50 the reversible capacity of both Li0.5MnPO4 and Li0.8MnPO4 increases with cycling indicating a gradual activation of more sites to accommodate a reversible diffusion of Li+ ions which may be related to the interaction between Mn2P2O7 and LiMnPO4 nanoparticles. Among all the different compositions, Li1.1MnPO4 exhibits the most stable cycling ability probably due to the existence of a trace amount of Li3PO4 impurity which functions as a solid state electrolyte on the surface. The magnetic properties and X-ray absorption spectroscopy (XAS) of MnPO4?H2O precursor, pure and carbon coated LiMnPO4 and all the other non-stoichiometric LixMnPO4 are also investigated to identify the key steps to prepare a high performance LiMnPO4.

Xiao, Jie; Chernova, Natalya; Upreti, Shailesh; Chen, Xilin; Li, Zheng; Deng, Zhiqun; Choi, Daiwon; Xu, Wu; Nie, Zimin; Graff, Gordon L.; Liu, Jun; Whittingham, M. S.; Zhang, Jiguang

2011-09-12

33

Oleic acid-assisted preparation of LiMnPO 4 and its improved electrochemical performance by Co doping  

Microsoft Academic Search

LiMnPO4, with a particle size of 50–150 nm, was prepared by oleic acid-assisted solid-state reaction. The materials were characterized\\u000a by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical\\u000a properties of the materials were investigated by galvanostatic cycling. It was found that the introduction of oleic acid in\\u000a the precursor led to smaller particle size and more

Zhao Yang; Gao-Shao Cao; Jian Xie; Xin-Bing Zhao

34

Shape controlled hydrothermal synthesis and characterization of LiFePO4 for lithium ion batteries.  

PubMed

Various LiFePO4 microstructures were synthesized via hydrothermal or solvothermal routes using different additives. In an aqueous solution, LiFePO4 spindles whose length was about 2 microm were obtained with the assistance of polyvinyl pyrrolidone (PVP). As PVP and P2O7(4-) added in water, ellipsoidal LiFePO4 particles which composed of nanoparticles around 100 nm in diameter were obtained. If the additive was cetyltrimethyl ammonium bromide (CTAB), sheet-like LiFePO4 crystals with the width of 100 nm were prepared. In the mixed solvents of water together with ethanol or acetylacetone, when adding CTAB or polyethylene glycol (20000), LiFePO4 plates or nanoparticles were obtained. The ellipsoidal LiFePO4 had the best electrochemical properties among all these products. It is found that the annealed samples were significantly better than the corresponding unannealed ones. Take the ellipsoidal LiFePO4 for example, the initial discharge capacity of annealed (161 mAh/g) was much higher than the unannealed ones (85 mAh/g) at 0.1 C and the former cell still could deliver a capacity of 143 mAh/g after 30 cycles. PMID:23646673

Yu, Yang; Li, Qianwen; Ma, Yanmei; Zhang, Xing; Zhu, Yongchun; Qian, Yitai

2013-02-01

35

Effect of conductive additives in LiFePO4 cathode for lithium-ion batteries  

SciTech Connect

The electrochemical properties of LiFePO4 cathodes with different carbon contents were studied to find out the role of carbon as conductive additive. LiFePO4 cathodes containing from 0 percent to 12 percent of conductive additive (carbon black or mixture of carbon black and graphite) were cycled at different C rates. The capacity of LiFePO4 cathode increased, as conductive additive content increased. Carbon increased the utilization of active material and the electrical conductivity of electrode, but decreased volumetric capacity of electrode.

Shim, J.; Guerfi, A.; Zaghib, K.; Striebel, K.A.

2003-11-25

36

Nanocomposite of LiFePO4 and mesoporous carbon for high power cathode of lithium rechargeable batteries.  

PubMed

A composite of LiFePO4 and MgO-templated disordered mesoporous carbon was prepared through infiltrating a LiFePO4 precursor solution into the mesoporous carbon and growing LiFePO4 nanocrystals in the pore of the carbon. Transmission electron microscope (TEM) and scanning electron microscope (SEM) analysis showed that LiFePO4 nanoparticles are embedded homogeneously in the mesoporous carbon without formation of big LiFePO4 particles out of the pores. The pores of the carbon are believed to suppress crystal growth of LiFePO4. The 3-dimensional conducting carbon network between the LiFePO4 nanoparticles led to excellent cycling stability and rate capability. The composite showed no fade of discharge capacity up to 100 cycles and 85% of the reversible capacity at 0.1 C was retained at 30 C. PMID:23421233

Kim, Jun-Il; Roh, Kwang Chul; Lee, Jae-Won

2012-11-01

37

Study of LiFePO 4 cathode materials coated with high surface area carbon  

Microsoft Academic Search

LiFePO4 is a potential cathode material for 4V lithium-ion batteries. Carbon-coated lithium iron phosphates were prepared using a high surface area carbon to react precursors through a solid-state process, during which LiFePO4 particles were embedded in amorphous carbon. The carbonaceous materials were synthesized by the pyrolysis of peanut shells under argon, where they were carbonized in a two-step process that

Cheng-Zhang Lu; George Ting-Kuo Fey; Hsien-Ming Kao

2009-01-01

38

Biomimetic synthesis and characterization of the positive electrode material LiFePO 4  

Microsoft Academic Search

The biosurfactant is used as the template to synthesize lithium iron phosphate (LiFePO4) precursor with the co-precipitation method and the microwave sintering method is used to prepare positive electrode material LiFePO4 for the lithium ion battery. By using the Brunauer–Emmett–Teller (BET) surface areas, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and conductometer, the authors explored the influence of the

Peng Li; Wen He; Hongshi Zhao; Shaopeng Wang

2009-01-01

39

Reaction behavior of LiFePO 4 as a cathode material for rechargeable lithium batteries  

Microsoft Academic Search

We investigated the effect of cell temperature on the electrochemical reaction behavior of LiFePO4. We evaluated its electrochemical characteristics by using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Both the electron transfer activity and the lithium ion diffusion rate in the LiFePO4 electrode increased as we increased the operating temperature. The apparent activation energy for the lithium diffusion was more

Masaya Takahashi; Shin-ichi Tobishima; Koji Takei; Yoji Sakurai

2002-01-01

40

Optimized carbon-coated LiFePO 4 cathode material for lithium-ion batteries  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) cathode material has been synthesized by a solid-state reaction. The XRD patterns of the samples show that the single-phase LiFePO4 compounds can be obtained in our experimental conditions. According to Popa theory, using the result from Rietveld refinement, the shape and the size of crystallite can be obtained. The result shows that the use of carbon

Y. Z. Dong; Y. M. Zhao; Y. H. Chen; Z. F. He; Q. Kuang

2009-01-01

41

Synthesis of LiFePO 4\\/polyacenes using iron oxyhydroxide as an iron source  

Microsoft Academic Search

LiFePO4\\/polyacenes (PAS) composite is synthesized by iron oxyhydroxide as a new raw material and phenol–formaldehyde resin as both reducing agent and carbon source. The mechanism of the reaction is outlined by the analysis of XRD, FTIR as well as TG\\/DSC. The results show that the formation of LiFePO4 is started at 300°C, and above 550°C, the product can be mainly

Guiling Yang; Xianfa Zhang; Jing Liu; Xingguang He; Jiawei Wang; Haiming Xie; Rongshun Wang

2010-01-01

42

Effect of carbon sources on the morphology of LiFePO 4 cathode materials for lithium ion batteries  

Microsoft Academic Search

The LiFePO4 materials were prepared by incorporating conductive carbon from pyrolysising three different carbon sources (acetylene black,\\u000a glucose and phonetic resin). The morphology LiFePO4\\/C was investigated by the SEM. Results revealed that the carbon precursor has much effect on the morphology of the samples.\\u000a The carbon coated LiFePO4 showed much better performance in terms of the discharge capacity and rate

Y.-M. Bai; H. Chen; Sh.-Ch. Han

2011-01-01

43

Electrochemical properties of LiFePO 4-multiwalled carbon nanotubes composite cathode materials for lithium polymer battery  

Microsoft Academic Search

LiFePO4-multiwalled carbon nanotubes (MWCNTs) composites were prepared by a hydrothermal method followed by ball-milling and heat treating. Cyclic voltammetry, ac impedance and galvanostatic charge\\/discharge testing results indicate that LiFePO4-MWCNTs composite exhibits higher discharge capacity and rate capability than pure LiFePO4 at high-rate at room temperature. It is demonstrated that the added MWCNTs not only increase the electronic conductivity and lithium-ion

Bo Jin; En Mei Jin; Kyung-Hee Park; Hal-Bon Gu

2008-01-01

44

Electrochemical performance of SiO 2-coated LiFePO 4 cathode materials for lithium ion battery  

Microsoft Academic Search

The surface of LiFePO4\\/C particles was coated with SiO2 via a sol–gel method, and the electrochemical performance of SiO2-coated LiFePO4 cathode materials at room temperature and 55°C was investigated. Compared with pristine LiFePO4, the structure of LiFePO4 with SiO2 coating had no change, the existence of SiO2 coating effectively enhanced the cycling capacity, reduced capacity fading at high temperature and

Ying-Da Li; Shi-Xi Zhao; Ce-Wen Nan; Bao-Hua Li

2011-01-01

45

Impacts of different polymer binders on electrochemical properties of LiFePO4 cathode  

NASA Astrophysics Data System (ADS)

Impacts of different polymer binders (PVdF, PAA and PMMA) on electrochemical performance of the LiFePO4 cathode in Li-ion batteries are investigated. From CV result, the voltage between redox peaks of the LiFePO4 with PVdF, PAA and PMMA binders are 0.26, 0.20 and 0.23 V, respectively. The current of the LiFePO4 with PMMA binder shows the highest value of 1.4 mA. The apparent diffusion coefficient of the LiFePO4 with PVdF, PAA and PMMA binders is 8.30 × 10-12, 2.57 × 10-11 and 9.13 × 10-11 cm2 s-1, respectively. The discharge capacities of the LiFePO4 with PVdF, PAA and PMMA binders are 106, 143 and 154 mAh g-1 at an initial cycle, respectively. FE-SEM studies clearly demonstrate that plate-like PAA and PMMA coating on the electrodes form a protective film, which may decrease the amount of the deposits, thus decreasing crack and crystallization on the electrode surface. Achieved results indicate that PVdF, PAA and PMMA binders show better properties than the traditional one, especially PMMA one.

Nguyen, Van Hiep; Wang, Wan Lin; Jin, En Mei; Gu, Hal-Bon

2013-10-01

46

Cycling performance of LiFePO 4 cathode material for lithium secondary batteries  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) cathode material has been synthesized by a solid-state reaction which uses Li3PO4 and Fe3(PO4)2·8H2O as starting materials. These materials were mixed with alumina balls and treated thermally at various temperatures in an argon and hydrogen atmosphere. The crystalline intensity of LiFePO4 powder prepared at 700°C is higher than that of powders prepared at 600 and 800°C.

Hyung-Sun Kim; Byung-Won Cho; Won-Il Cho

2004-01-01

47

Carbon Surface Layers on a High-Rate LiFePO4  

SciTech Connect

Transmission electron microscopy (TEM) was used to image particles of a high-rate LiFePO4 sample containing a small amount of in situ carbon. The particle morphology is highly irregular, with a wide size distribution. Nevertheless, coatings, varying from about 5-10 nm in thickness, could readily be detected on surfaces of particles as well as on edges of agglomerates. Elemental mapping using Energy Filtered TEM (EFTEM) indicates that these very thin surface layers are composed of carbon. These observations have important implications for the design of high-rate LiFePO4 materials in which, ideally, a minimal amount of carbon coating is used.

Gabrisch, Heike; Wilcox, James D.; Doeff, Marca M.

2005-09-06

48

TEM Studies of Carbon Coated LiFePO4 after Charge DischargeCycling  

SciTech Connect

Carbon coating has proven to be a successful approach toimprove the rate capability of LiFePO4 used in rechargeable Li-ionbatteries. Investigations of the microstructure of carbon coated LiFePO4after charge discharge cycling shows that the carbon surface layerremains intact over 100 cycles. We find micro cracks in the cycledmaterial that extend parallel to low indexed lattice planes. Ourobservations differ from observations made by other authors. However thedifferences between the orientations of crack surfaces in both studiescan be reconciled considering the location of weak bonds in the unit celland specimen geometry as well as elastic stress fields ofdislocation.

Gabrisch, H.; Wilcox, J.; Doeff, M.

2006-11-30

49

Conductive surface modification of LiFePO4 with nitrogen doped carbon layers for lithium-ion batteries  

SciTech Connect

The LiFePO4 rod surface modified with nitrogen doped carbon layer has been prepared using hydrothermal processing followed by post-annealing in the presence of an ionic liquid. The coated LiFePO4 rod exhibits good capacity retention and high rate capability as the nitrogen doped carbon improves conductivity and prevents aggregation of the rod during cycling.

Yoon, Sukeun [ORNL; Liao, Chen [ORNL; Sun, Xiao-Guang [ORNL; Bridges, Craig A [ORNL; Unocic, Raymond R [ORNL; Nanda, Jagjit [ORNL; Dai, Sheng [ORNL; Paranthaman, Mariappan Parans [ORNL

2012-01-01

50

Hierarchical LiFePO4 with a controllable growth of the (010) facet for lithium-ion batteries  

PubMed Central

Hierarchically structured LiFePO4 was successfully synthesized by ionic liquid solvothermal method. These hierarchically structured LiFePO4 samples were constructed from nanostructured platelets with their (010) facets mainly exposed. To the best of our knowledge, facet control of a hierarchical LiFePO4 crystal has not been reported yet. Based on a series of experimental results, a tentative mechanism for the formation of these hierarchical structures was proposed. After these hierarchically structured LiFePO4 samples were coated with a thin carbon layer and used as cathode materials for lithium-ion batteries, they exhibited excellent high-rate discharge capability and cycling stability. For instance, a capacity of 95% can be maintained for the LiFePO4 sample at a rate as high as 20 C, even after 1000 cycles.

Guo, Binbin; Ruan, Hongcheng; Zheng, Cheng; Fei, Hailong; Wei, Mingdeng

2013-01-01

51

Hierarchical LiFePO4 with a controllable growth of the (010) facet for lithium-ion batteries.  

PubMed

Hierarchically structured LiFePO4 was successfully synthesized by ionic liquid solvothermal method. These hierarchically structured LiFePO4 samples were constructed from nanostructured platelets with their (010) facets mainly exposed. To the best of our knowledge, facet control of a hierarchical LiFePO4 crystal has not been reported yet. Based on a series of experimental results, a tentative mechanism for the formation of these hierarchical structures was proposed. After these hierarchically structured LiFePO4 samples were coated with a thin carbon layer and used as cathode materials for lithium-ion batteries, they exhibited excellent high-rate discharge capability and cycling stability. For instance, a capacity of 95% can be maintained for the LiFePO4 sample at a rate as high as 20 C, even after 1000 cycles. PMID:24071818

Guo, Binbin; Ruan, Hongcheng; Zheng, Cheng; Fei, Hailong; Wei, Mingdeng

2013-09-27

52

Comparison of LiMnPO4 made by Combustion and Hydrothermal Syntheses  

SciTech Connect

Among the olivine-structured metal phosphate family, LiMnPO{sub 4} exhibits a high discharge potential (4V), which is still compatible with common electrolytes, making it interesting for use in the next generation of Li ion batteries. The extremely low electronic conductivity of this material severely limits its electrochemical performance, however. One strategy to overcome this limitation is to make LiMnPO{sub 4} nanoparticulate to decrease the diffusion distance. Another is to add a carbon or other conductive coating in intimate contact with the nanoparticles of the main phase, as is commonly done with LiFePO{sub 4}. The electrochemical performance of LiFePO{sub 4} is highly dependent on the quality of the carbon coatings on the particles, among other variables. Combustion synthesis allows the co-synthesis of nanoparticles coated with carbon in one step. Hydrothermal synthesis is used industrially to make LiFePO{sub 4} cathode materials and affords a good deal of control over purity, crystallinity, and particle size. A wide range of olivine-structured materials has been successfully prepared by this technique, including LiMnPO{sub 4} in this study. In this paper, we report on the new synthesis of nano-LiMnPO{sub 4} by a combustion method. The purity is dependent upon the conditions used for synthesis, including the type of fuel and precursors that are chosen. The fuel to nitrate ratio influences the combustion temperature, which determines the type and amount of carbon found in the LiMnPO{sub 4} composites. This can further be modified by use of carbon structural modifiers added during a subsequent (optional) calcination step. Figure 1 shows a transmission electron microscopy (TEM) image of the spherical nano-sized LiMnPO{sub 4} particles typically formed by combustion synthesis. The average particle size is around 30 nm, in agreement with values obtained by the Rietveld refinement of XRD patterns. The small size of the particles cause the peak broadening evident in the pattern of combustion formed LiMnPO{sub 4}, shown in Figure 2. Figure 2 also shows a pattern of hydrothermally prepared LiMnPO{sub 4}, which is sub-micron in size. In this presentation, we will show how the crystallographic parameters, particle size, particle morphology, and carbon content and structure impact the electrochemical properties of the LiMnPO{sub 4}/C composites produced by these methods.

Chen, Jiajun; Doeff, Marca M.; Wang, Ruigang

2008-10-12

53

Comparison of LiMnPO4 made by Combustion and Hydrothermal Syntheses  

SciTech Connect

Among the olivine-structured metal phosphate family, LiMnPO{sub 4} exhibits a high discharge potential (4V), which is still compatible with common electrolytes, making it interesting for use in the next generation of Li ion batteries. The extremely low electronic conductivity of this material severely limits its electrochemical performance, however. One strategy to overcome this limitation is to make LiMnPO{sub 4} nanoparticulate to decrease the diffusion distance. Another is to add a carbon or other conductive coating in intimate contact with the nanoparticles of the main phase, as is commonly done with LiFePO{sub 4}. The electrochemical performance of LiFePO{sub 4} is highly dependent on the quality of the carbon coatings on the particles [1-2], among other variables. Combustion synthesis allows the co-synthesis of nanoparticles coated with carbon in one step. Hydrothermal synthesis is used industrially to make LiFePO{sub 4} cathode materials [3] and affords a good deal of control over purity, crystallinity, and particle size. A wide range of olivine-structured materials has been successfully prepared by this technique [4], including LiMnPO{sub 4} in this study. In this paper, we report on the new synthesis of nano-LiMnPO{sub 4} by a combustion method. The purity is dependent upon the conditions used for synthesis, including the type of fuel and precursors that are chosen. The fuel to nitrate ratio influences the combustion temperature, which determines the type and amount of carbon found in the LiMnPO{sub 4} composites. This can further be modified by use of carbon structural modifiers added during a subsequent (optional) calcination step. Figure 1 shows a transmission electron microscopy (TEM) image of the spherical nano-sized LiMnPO{sub 4} particles typically formed by combustion synthesis. The average particle size is around 30 nm, in agreement with values obtained by the Rietveld refinement of XRD patterns. The small size of the particles cause the peak broadening evident in the pattern of combustion formed LiMnPO{sub 4}, shown in Figure 2. Figure 2 also shows a pattern of hydrothermally prepared LiMnPO{sub 4}, which is sub-micron in size. In this presentation, we will show how the crystallographic parameters, particle size, particle morphology, and carbon content and structure impact the electrochemical properties of the LiMnPO{sub 4}/C composites produced by these methods.

Chen, Jiajun; Doeff, Marca M.; Wang, Ruigang

2008-05-15

54

Enhanced electrochemical performance of graphene modified LiFePO4 as a cathode material for lithium ion batteries  

NASA Astrophysics Data System (ADS)

We have synthesized LiFePO4/graphene nano-composites using a sol-gel method by adding water dispersed graphene oxide to the LiFePO4 precursors during the synthesis. The graphene oxide was reduced by annealing the composite at 600^oC for 5h in flowing forming gas (90% Ar and 10% H2). The phase purity of the product was characterized by X-Ray diffraction and Raman spectroscopy. The reduction of graphene oxide was verified by Raman spectroscopy and X-ray Photoelectron spectroscopy. The electronic conductivity of LiFePO4/graphene composite was found to be six orders of magnitude higher than that of pure LiFePO4 synthesized following otherwise the same procedure except that no graphene oxide was added. SEM and TEM images show that LiFePO4 particles are wrapped in uniformly distributed graphene sheets throughout the material forming a three dimensional conducting network. At low currents, the capacity of the composite cathode reaches 160 mAh/g, which is very close to the theoretical limit. More significantly, the graphene wrapped LiFePO4 shows a dramatically improved rate capability and excellent charge-discharge cycle stability in comparison with the LiFePO4 without graphene.

Dhindsa, K. S.; Mandal, B. P.; Lin, M. W.; Nazri, M.; Nazri, G. A.; Naik, V. M.; Vaishnava, P.; Naik, R.; Zhou, Z. X.

2012-10-01

55

The development of low cost LiFePO4-based high power lithium-ion batteries  

SciTech Connect

The cycling performance of low-cost LiFePO4-based high-power lithium-ion cells was investigated and the components were analyzed after cycling to determine capacity fade mechanisms. Pouch type LiFePO4/natural graphite cells were assembled and evaluated by constant C/2 cycling, pulse-power and impedance measurements. From post-test electrochemical analysis after cycling, active materials, LiFePO4 and natural graphite, showed no degradation structurally or electrochemically. The main reasons for the capacity fade of cell were lithium inventory loss by side reaction and possible lithium deposition on the anode.

Shim, Joongpyo; Sierra, Azucena; Striebel, Kathryn A.

2003-11-25

56

Thermal Stability and Phase Transformation of Electrochemically Charged/Discharged LiMnPO4 Cathode for Li-Ion Battery  

SciTech Connect

Electrochemically active LiMnPO4 nanoplate at lithiated/delithiated state were subjected to thermal stability and phase transformation evaluate for safety as a cathode material for Li-ion battery. The phase transformation and oxygen evolution temperature on the delithiated MnPO4 were characterized using in-situ hot-stage X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), thermogravimetric - differential scanning calorimetry - mass spectroscopy (TGA-DSC-MS), transmission electron microscopy and scanning electron microscopy (SEM) - energy dispersive X-ray analysis (EDAX).

Choi, Daiwon; Xiao, Jie; Choi, Young Joon; Hardy, John S.; Vijayakumar, M.; Bhuvaneswari, M. S.; Liu, Jun; Xu, Wu; Wang, Wei; Yang, Zhenguo; Graff, Gordon L.; Zhang, Jiguang

2011-11-01

57

Analysis of the thermal behavior of a LiFePO4 battery cell  

NASA Astrophysics Data System (ADS)

This paper presents theory, experiments and numerical modeling results for the electrothermal analysis of Lithium Iron Phosphate (LiFePO4) battery cells. Thermal management of batteries is important for several reasons including thermal runaway and maintaining battery operating time. A battery pack is comprised of battery cells which are stacked together without cooling surfaces except for the pack outer surface. The central cells in the pack are therefore exposed to the risk of overheating. A model for a single specific commercial LiFePO4 battery cell is presented together with preliminary experiments and results for determination of heating sources during charging and discharging. Based on the experimental results we extract model parameters for use in the model. The experiments lead to relations for the cell surface temperature and the lump temperature of the cell. A reasonable agreement between experiments and the model is found and suggestions for further work is indicated.

Niculu??, Marian-Ciprian; Veje, Christian

2012-11-01

58

Characterization of LiFePO4/C Composite Thin Films Using Electrochemical Impedance Spectroscopy  

NASA Astrophysics Data System (ADS)

The composite LiFePO4/C thin films were prepared on steel substrate by radio frequency (RF) magnetron sputtering. Electrochemical properties of the obtained thin films were investigated by cyclic voltammetry charge-discharge measurements and electrochemical impedance spectroscopy (EIS). The films annealed at 550 °C exhibited a couple of redox peaks at 3.45 V vs. Li/Li+ characteristic for the electrochemical lithium insertion/extraction in LiFePO4. At low current rate such composite thin film showed a discharge capacity of over 110 mAh g-1. The dependence of charge transfer resistance, double layer capacitance and lithium diffusion coefficients on applied electrode potential were calculated from EIS data. Determined values of lithium diffusion coefficient were in the range from 8.3-10-13 cm2 s1 to 1.2-10-13 cm2 s-1 at 3.4 V and 3.7 V, respectively.

Bajars, G.; Kucinskis, G.; Smits, J.; Kleperis, J.; Lusis, A.

2012-08-01

59

Needle-like LiFePO 4 thin films prepared by an off-axis pulsed laser deposition technique  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) thin films were prepared by pulsed laser deposition with an off-axis geometry. Amorphous, needle-like and crystallized granular thin films were prepared on Si and titanium substrates. The preferred orientation of these crystallized LiFePO4 thin films is (120). Microstructures of the deposited films are dependant on the substrate temperature (room temperature, 500 °C and 700 °C) and Ar pressure

Jinpeng Sun; Kun Tang; Xiqian Yu; Hong Li; Xuejie Huang

2009-01-01

60

Electrical properties of poly(vinyl alcohol) (PVA) based on LiFePO 4 complex polymer electrolyte films  

Microsoft Academic Search

Li ion conducting polymer electrolyte films were prepared based on poly(vinyl alcohol) (PVA) with 5, 10, 15, 20, 25 and 30 wt%\\u000a lithium iron phosphate (LiFePO4) salt using a solution-casting technique. X-ray diffraction (XRD) was used to determine the complexation of the polymer with\\u000a LiFePO4 salt. Differential scanning (DSC) calorimetry was used to determine the melting temperatures of the pure PVA

V. M. Mohan; Weiliang Qiu; Jie Shen; Wen Chen

2010-01-01

61

Solvothermal synthesis of hierarchical LiFePO 4 microflowers as cathode materials for lithium ion batteries  

Microsoft Academic Search

Hierarchical LiFePO4 microflowers have been successfully synthesized via a solvothermal reaction in ethanol solvent with the self-prepared ammonium iron phosphate rectangular nanoplates as a precursor, which is obtained by a simple water evaporation method beforehand. The hierarchical LiFePO4 microflowers are self-assemblies of a number of stacked rectangular nanoplates with length of 6–8?m, width of 1–2?m and thickness of around 50nm.

Qiang Wang; Weixin Zhang; Zeheng Yang; Shaoying Weng; Zhuojie Jin

2011-01-01

62

Monodisperse porous LiFePO4 microspheres for a high power Li-ion battery cathode.  

PubMed

A novel solvothermal approach combined with high-temperature calcinations was developed to synthesize on a large scale LiFePO(4) microspheres consisting of nanoplates or nanoparticles with an open three-dimensional (3D) porous microstructure. These micro/nanostructured LiFePO(4) microspheres have a high tap density and, as electrodes, show excellent rate capability and cycle stability. PMID:21268579

Sun, Chunwen; Rajasekhara, Shreyas; Goodenough, John B; Zhou, Feng

2011-01-26

63

Particle size distribution and electrochemical properties of LiFePO 4 prepared by a freeze-drying method  

Microsoft Academic Search

The electrochemical performance of carbon-coated nanocrystalline LiFePO4 prepared by a freeze-drying method is examined. This method is based on the thermal decomposition of homogeneous phosphate-formate precursors. Structural and morphological characterization of LiFePO4 is carried out by powder XRD, BET measurements, SEM and XPS analyses. The electrochemical behaviour is tested in model lithium cells using galvanostatic mode. By changing the solution

E. Zhecheva; Ml. Mladenov; P. Zlatilova; V. Koleva; R. Stoyanova

2010-01-01

64

A novel process for producing synthetic rutile and LiFePO 4 cathode material from ilmenite  

Microsoft Academic Search

Synthetic rutile and LiFePO4 cathode materials are prepared from the titanium hydrolysate and iron-rich lixivium, respectively. The titanium hydrolysate and iron-rich lixivium are obtained from the ilmenite by mechanical activation and leaching. The purity of synthetic rutile and the electrochemical performance of LiFePO4 are mainly determined by the leaching process. The optimal leaching conditions are as follows: HCl concentration 20wt.%,

Ling Wu; Xinhai Li; Zhixing Wang; Huajun Guo; Xiaojuan Wang; Feixiang Wu; Jie Fang; Zhiguo Wang; Lingjun Li

2010-01-01

65

Electrochemical properties of LiFePO 4 thin films prepared by pulsed laser deposition  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) thin film electrodes were prepared by pulsed laser deposition (PLD). The thin films were annealed at various temperatures under argon gas flow and the influence of annealing temperature on their electrochemical performance was studied. The thin films annealed at 773 and 873K exhibited a couple of redox peaks at 3.4V (versus Li\\/Li+) that are characteristics of

Chihiro Yada; Yasutoshi Iriyama; Soon-Ki Jeong; Takeshi Abe; Minoru Inaba; Zempachi Ogumi

2005-01-01

66

LiFePO 4 doped with magnesium prepared by hydrothermal reaction in glucose solution  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) doped with magnesium was hydrothermally synthesized from commercial LiOH, FeSO4, H3PO4 and MgSO4 with glucose as carbon precursor in aqueous solution. The samples were characterized by X-ray powder diffraction, scanning electron microscopy and constant charge–discharge cycling. The results show that the synthesized powders have been in situ coated with carbon precursor produced from caramel reaction of

Xiu Qin Ou; Guang Chuan Liang; Jin Sheng Liang; Sheng Zhao Xu; Xia Zhao

2008-01-01

67

Lithium deintercalation in LiFePO4 nanoparticles via a domino-cascade model  

Microsoft Academic Search

Lithium iron phosphate is one of the most promising positive-electrode materials for the next generation of lithium-ion batteries that will be used in electric and plug-in hybrid vehicles. Lithium deintercalation (intercalation) proceeds through a two-phase reaction between compositions very close to LiFePO4 and FePO4. As both endmember phases are very poor ionic and electronic conductors, it is difficult to understand

M. Maccario; L. Croguennec; F. Weill; C. Delmas; F. Le Cras

2008-01-01

68

PPy doped PEG conducting polymer films synthesized on LiFePO 4 particles  

Microsoft Academic Search

In this work, polyethyleneglycole (PEG) is introduced into polypyrrole (PPy) film coated on LiFePO4 powder particles to promote the properties of cathode material for lithium-ion batteries. The enhancement of the electrochemical activity by the substitution of a carbon with electrochemically active polymer is investigated. Films of the PPy doped with the PEG were prepared by the chemical oxidative polymerization of

Andrea Fedorková; Renáta Ori?áková; Andrej Ori?ák; Ivan Talian; Andreas Heile; Hans-Dieter Wiemhöfer; Dušan Kaniansky; Heinrich F. Arlinghaus

2010-01-01

69

Improving the electrochemical performance of LiFePO4/C by doping magnesium trisilicate  

NASA Astrophysics Data System (ADS)

This work studies the effect of doping with magnesium trisilicate for LiFePO4/C cathode materials by a solid-state method. The samples were synthesized by two-step processing. Firstly, it was heated at 360 °C for 10 hours and then was calcined at 700°C for 10 hours. All the annealing processing was carried out in argon atmosphere. The phase structure, morphology and element distribution of prepared samples were characterized by XRD and scanning electron microscope and energy dispersive spectrometer. The results show that Mg2+ and Si4+ co-doped LiFe0.99Mg0.01P0.985Si0.015O4/C cathode materials exhibit higher capacity and rate capability than the unsubstituted LiFePO4/C cathode. For example, LiFe0.99Mg0.01P0.985Si0.015O4/C exhibit discharge capacity of 146 mAh·g-1 compared to 140mAh·g-1 for unsubstituted LiFePO4/C at 0.5C. Especially, at 5C rate, the discharge capacity of LiFe0.99Mg0.01P0.985Si0.015O4/C was remarkably exceeded that of unsubstituted LiFePO4/C cathode materials. The better performances of the cathode were attributed to the increase of electronic conductivity and the improved migration of lithium ion.

Chen, Weiqiang; Zhao, Shixi; Ding, Hao; Li, Baohua; Nan, Cewen

2011-11-01

70

Polyol process for the synthesis of LiFePO 4 rhombohedral particles  

Microsoft Academic Search

As a new approach, LiFePO4 nanoparticles were directly synthesized from precursors iron(III) nitrate and lithium dihydrogen phosphate by a polyol process without post heat treatment in one step. The obtained powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and combined thermogravimetry and differential scanning calorimetry and mass spectroscopy TG\\/DSC\\/MS. The X-ray diffraction showed the orthorhombic crystal structure

Madhav Singh; Monika Willert-Porada

2011-01-01

71

Lithium-iron battery: Fe 2O 3 anode versus LiFePO 4 cathode  

Microsoft Academic Search

In this work we disclose a novel lithium ion battery based on a bulk iron oxide, alfa-Fe2O3, anode and a lithium iron phosphate, LiFePO4, cathode which are low cost and environmental compatible materials. The preliminary results here reported suggest that this unique battery may be highly competitive with other power sources especially in terms of cost and reliability.

Jusef Hassoun; Fausto Croce; Inchul Hong; Bruno Scrosati

2011-01-01

72

Enhanced electrochemical performance of graphene modified LiFePO4 as a cathode material for lithium ion batteries  

NASA Astrophysics Data System (ADS)

We synthesized LiFePO4/graphene nano-composites using a sol-gel method by adding water dispersed graphene oxide to the LiFePO4 precursors during the synthesis. The graphene oxide was subsequently reduced to graphene by annealing the composite which was confirmed by Raman spectroscopy and X-ray Photoelectron spectroscopy. The electronic conductivity of the composite was found to be six orders of magnitude higher than that of pure LiFePO4 Scanning Electron microscopy and Transmission electron microscopy images show LiFePO4 particles are wrapped in uniformly distributed graphene sheets throughout the material forming a three dimensional conducting network. At low currents, (C/3), the capacity of the composite cathode reaches 160 mAh/g, which is very close to the theoretical limit. More significantly, the graphene wrapped LiFePO4 shows a dramatically improved rate capability up to 27C, and excellent charge-discharge cycle stability over 500 stable cycles as compared to the pure LiFePO4.

Singh Dhindsa, Kulwinder; Prasad Mandal, Balaji; Lin, Ming-Wei; Nazri, Maryam; Nazri, Gholam Abbas; Naik, Vaman M.; Vaishnava, Prem; Naik, Ratna; Zhou, Zhixian

2013-03-01

73

A chemically activated graphene-encapsulated LiFePO4 composite for high-performance lithium ion batteries.  

PubMed

A composite of modified graphene and LiFePO4 has been developed to improve the speed of charging-discharging and the cycling stability of lithium ion batteries using LiFePO4 as a cathode material. Chemically activated graphene (CA-graphene) has been successfully synthesized via activation by KOH. The as-prepared CA-graphene was mixed with LiFePO4 to prepare the composite. Microscopic observation and nitrogen sorption analysis have revealed the surface morphologies of CA-graphene and the CA-graphene/LiFePO4 composite. Electrochemical properties have also been investigated after assembling coin cells with the CA-graphene/LiFePO4 composite as a cathode active material. Interestingly, the CA-graphene/LiFePO4 composite has exhibited better electrochemical properties than the conventional graphene/LiFePO4 composite as well as bare LiFePO4, including exceptional speed of charging-discharging and excellent cycle stability. That is because the CA-graphene in the composite provides abundant porous channels for the diffusion of lithium ions. Moreover, it acts as a conducting network for easy charge transfer and as a divider, preventing the aggregation of LiFePO4 particles. Owing to these properties of CA-graphene, LiFePO4 could demonstrate enhanced and stably long-lasting electrochemical performance. PMID:23897269

Ha, Jeonghyun; Park, Seung-Keun; Yu, Seung-Ho; Jin, Aihua; Jang, Byungchul; Bong, Sungyool; Kim, In; Sung, Yung-Eun; Piao, Yuanzhe

2013-09-21

74

Anisotropy in Magnetic Properties and Electronic Structure of Single Crystal LiFePO4  

SciTech Connect

We report the experimental and theoretical results on the anisotropies in the magnetic properties and x-ray absorption spectra of single-crystal LiFePO4. A mean-field theory is developed to explain the observed strong anisotropies in Lande g-factor, paramagnetic Curie temperature, and effective moment for LiFePO4 single crystals. The values of the in-plane nearest- and next-nearest-neighbor spin exchange (J1 and J2), interplane spin exchange (J{perpendicular}), and single-ion anisotropy (D), obtained recently from neutron scattering measurements, are used for calculating the Curie temperatures with the formulas derived from the mean-field Hamiltonian. It is found that the calculated Curie temperatures match well with that obtained by fitting the magnetic susceptibility curves to the modified Curie-Weiss law. For the polarized Fe K-edge x-ray absorption spectra of single-crystal LiFePO4, a different feature assignment for the 1s4p transition features is proposed and the anisotropy in the intensities of the 1s3d transition features is explained adequately by a one-electron theory calculation of the electric quadrupole transition terms in the absorption coefficient.

Liang,G.; Park, K.; Li, J.; Benson, R.; Vaknin, D.; Markert, J.; Croft, M.

2008-01-01

75

Synthesis and electrochemical performance of nano-metastructured LiFePO4/C cathode material.  

PubMed

The nano-metastructured LiFePO4/C composites were synthesized by carbothermal reduction method using starch gel as carbon source and dispersing media to obtain high tap density LiFePO4 with excellent electrochemical performance. The raw materials were coated by starch gel as compact precursors, which was sintered at 750 degrees C for 8 h to obtain high-density LiFePO4/C composite aggregated with nano-sized particles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations showed that the primary particles had an average size of about 50-80 nm and the aggregates had a homogeneous particle size distribution of about 400 nm. The asprepared samples had a shortened lithium-ion diffusion length but with higher tap density, thus leading to the excellent electrochemical performance of the cathode materials. Electrochemical results showed that the samples delivered high discharge capacities of 155.6 and 120.7 mAh/g at 0.2C and 5C rates, respectively, with excellent cycling performance. PMID:21138008

Zhi, Xiaoke; Liang, Guangchuan; Wang, Li; Cui, Junyan; Yang, Limei

2010-11-01

76

Mesoscale phase distribution in single particles of LiFePO4 following lithium deintercalation.  

PubMed

The chemical phase distribution in hydrothermally grown micrometric single crystals LiFePO4 following partial chemical delithiation was investigated. Full field and scanning X-ray microscopy were combined with X-ray absorption spectroscopy at the Fe K- and O K-edges, respectively, to produce maps with high chemical and spatial resolution. The resulting information was compared to morphological insight into the mechanics of the transformation by scanning transmission electron microscopy. This study revealed the interplay at the mesocale between microstructure and phase distribution during the redox process, as morphological defects were found to kinetically determine the progress of the reaction. Lithium deintercalation was also found to induce severe mechanical damage in the crystals, presumably due to the lattice mismatch between LiFePO4 and FePO4. Our results lead to the conclusion that rational design of intercalation-based electrode materials, such as LiFePO4, with optimized utilization and life requires the tailoring of particles that minimize kinetic barriers and mechanical strain. Coupling TXM-XANES with TEM can provide unique insight into the behavior of electrode materials during operation, at scales spanning from nanoparticles to ensembles and complex architectures. PMID:23745016

Boesenberg, Ulrike; Meirer, Florian; Liu, Yijin; Shukla, Alpesh K; Dell'anna, Rossana; Tyliszczak, Tolek; Chen, Guoying; Andrews, Joy C; Richardson, Thomas J; Kostecki, Robert; Cabana, Jordi

2013-05-14

77

Effects of carbonaceous materials on the physical and electrochemical performance of a LiFePO 4 cathode for lithium-ion batteries  

Microsoft Academic Search

The effects of carbonaceous materials on the physical and electrochemical performance of LiFePO4\\/C hybrids are reviewed. The major role, advantages and disadvantages of carbon-based materials in LiFePO4\\/carbon hybrids are discussed. The introduction of an in situ grown carbon coating would be beneficial to limiting the LiFePO4 particle growth and increasing the electric conductivity. The structure and precursors of the in

Fei-yu KANG; Jun MA; Bao-hua LI

2011-01-01

78

Electrochemical properties of the carbon-coated LiFePO 4 as a cathode material for lithium-ion secondary batteries  

Microsoft Academic Search

In this study the effect of the carbon coating on the electrochemical properties of LiFePO4 as a cathode for Li-ion batteries were investigated. The carbon-coated LiFePO4 particles were synthesized by the mechanochemical process and one-step heat treatment. Microscopic observations using SEM and TEM revealed that the carbon coating reduced the particle size of the LiFePO4. The carbon-coated LiFePO4 showed much

Ho Chul Shin; Won Il Cho; Ho Jang

2006-01-01

79

Porous LiFePO 4 \\/NiP Composite nanospheres as the cathode materials in rechargeable lithium-ion batteries  

Microsoft Academic Search

We report the synthesis of porous LiFePO4\\/NiP composite nanospheres and their application in rechargeable lithium-ion batteries. A simple one-step spraying technique\\u000a was developed to prepare LiFePO4\\/NiP composite nanospheres with an electrical conductivity 103–104 times that of bulk particles of LiFePO4. Electrochemical measurements show that LiFePO4 nanospheres with a uniform loading of 0.86 wt%–1.50 wt% NiP exhibit high discharge capacity, good

Chunsheng Li; Shaoyan Zhang; Fangyi Cheng; Weiqiang Ji; Jun Chen

2008-01-01

80

Modified solid-state reaction synthesized cathode lithium iron phosphate (LiFePO4) from different phosphate sources.  

PubMed

A modified solid-state method was used to prepare LiFePO4. With the aid of deionized water, a mixture containing Fe2O3, NH4H2PO4 (or (NH4)2HPO4), LiOH, glucose and oxalic acid was prepared into fluffy powders, which were heated in a carbon-coated crucible at 700 degrees C for 3 hours to synthesize LiFePO4 without any inert gas flow. For the first time, the roles of NH4H2PO4 and (NH4)2HPO4 on the preparation of LiFePO4 were systematically investigated. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS), revealing that the crystallinity of the LiFePO4 sample prepared from NH4H2PO4 is superior to that prepared from (NH4)2HPO4 and the particle size of the sample prepared from NH4H2PO4 is smaller than that prepared from (NH4)2HPO4. The specific capacity, cycle property and rate capabilities were also compared between the as-prepared LiFePO4 samples. A better electrochemical performance was observed in the sample prepared from NH4H2PO4. PMID:22852311

Ding, Keqiang; Li, Wenjuan; Wang, Qingfei; Wei, Suying; Guo, Zhanhu

2012-05-01

81

Simultaneous enhancement of electronic and Li+ ion conductivity in LiFePO4  

NASA Astrophysics Data System (ADS)

Enhancing the electronic and ionic conductivity in Li compounds can significantly impact the design of batteries. Here, we explore the influence of biaxial strain on the electronic and Li+ ion conductivities of LiFePO4 by performing first-principles calculations. We find that 4% biaxial tensile strain (BTS) leads to 15 times increase in electronic conductivity and 50 times increase in Li+ ion conductivity at 300 K, respectively. Electronic conductivity is enhanced because BTS softens lattice distortions around a polaron, resulting in a reduction of the activation barrier. The extra volume introduced by tensile strain also reduces the barrier of Li+ ion migration.

Lee, Jaekwang; Pennycook, Stephen J.; Pantelides, Sokrates T.

2012-07-01

82

Preparation of synthetic rutile and metal-doped LiFePO 4 from ilmenite  

Microsoft Academic Search

The synthetic rutile and metal-doped LiFePO4 are prepared from the high-titanium residue and iron-rich lixivium, which are obtained from the ilmenite by a mechanical activation and leaching process. ICP results show that the rutile contains 92.01% TiO2, 1.59% Fe2O3, 0.034% MnO2 and 0.60% (MgO+CaO), which meet the requirement of the titanium dioxide chlorination process. The results also reveal that small

Ling Wu; Xinhai Li; Zhixing Wang; Xiaojuan Wang; Lingjun Li; Jie Fang; Feixiang Wu; Huajun Guo

2010-01-01

83

A chemically activated graphene-encapsulated LiFePO4 composite for high-performance lithium ion batteries  

NASA Astrophysics Data System (ADS)

A composite of modified graphene and LiFePO4 has been developed to improve the speed of charging-discharging and the cycling stability of lithium ion batteries using LiFePO4 as a cathode material. Chemically activated graphene (CA-graphene) has been successfully synthesized via activation by KOH. The as-prepared CA-graphene was mixed with LiFePO4 to prepare the composite. Microscopic observation and nitrogen sorption analysis have revealed the surface morphologies of CA-graphene and the CA-graphene/LiFePO4 composite. Electrochemical properties have also been investigated after assembling coin cells with the CA-graphene/LiFePO4 composite as a cathode active material. Interestingly, the CA-graphene/LiFePO4 composite has exhibited better electrochemical properties than the conventional graphene/LiFePO4 composite as well as bare LiFePO4, including exceptional speed of charging-discharging and excellent cycle stability. That is because the CA-graphene in the composite provides abundant porous channels for the diffusion of lithium ions. Moreover, it acts as a conducting network for easy charge transfer and as a divider, preventing the aggregation of LiFePO4 particles. Owing to these properties of CA-graphene, LiFePO4 could demonstrate enhanced and stably long-lasting electrochemical performance.A composite of modified graphene and LiFePO4 has been developed to improve the speed of charging-discharging and the cycling stability of lithium ion batteries using LiFePO4 as a cathode material. Chemically activated graphene (CA-graphene) has been successfully synthesized via activation by KOH. The as-prepared CA-graphene was mixed with LiFePO4 to prepare the composite. Microscopic observation and nitrogen sorption analysis have revealed the surface morphologies of CA-graphene and the CA-graphene/LiFePO4 composite. Electrochemical properties have also been investigated after assembling coin cells with the CA-graphene/LiFePO4 composite as a cathode active material. Interestingly, the CA-graphene/LiFePO4 composite has exhibited better electrochemical properties than the conventional graphene/LiFePO4 composite as well as bare LiFePO4, including exceptional speed of charging-discharging and excellent cycle stability. That is because the CA-graphene in the composite provides abundant porous channels for the diffusion of lithium ions. Moreover, it acts as a conducting network for easy charge transfer and as a divider, preventing the aggregation of LiFePO4 particles. Owing to these properties of CA-graphene, LiFePO4 could demonstrate enhanced and stably long-lasting electrochemical performance. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02738d

Ha, Jeonghyun; Park, Seung-Keun; Yu, Seung-Ho; Jin, Aihua; Jang, Byungchul; Bong, Sungyool; Kim, In; Sung, Yung-Eun; Piao, Yuanzhe

2013-08-01

84

Effect of Fe(III) impurity on the electrochemical performance of LiFePO 4 prepared by hydrothermal process  

Microsoft Academic Search

Lithium iron phosphate (LiFePO4) was synthesized from LiOH, FeSO4 and H3PO4 by a hydrothermal process at 180°C. The samples were characterized by X-ray diffraction, scanning electron microscopy and\\u000a chemical analysis. Electrochemical performance of the samples was tested in terms of charge-discharge capacity and cycling\\u000a behavior. The results indicated that Fe(III) impurity had obviously effect on the electrochemical properties of LiFePO4,

XiuQin Ou; ShengZhao Xu; GuangChuan Liang; Li Wang; Xia Zhao

2009-01-01

85

Physical and electrochemical properties of LiFePO 4\\/carbon composite synthesized at various pyrolysis periods  

Microsoft Academic Search

Aluminum-doped lithium iron phosphate was synthesized with a modified sol–gel process. The sol–gel derived cathodes show much higher conductivity than those prepared by a solid-state method. The conductivity is 8×10?2Scm?1 for the Al-doped LiFePO4\\/carbon composite powders synthesized at 850°C for 2h, as determined using AC impedance spectroscopy. The electrodes consisting of the Al-doped LiFePO4\\/carbon composite powders were fabricated for the

Kuei-Feng Hsu; Sun-Yuan Tsay; Bing-Joe Hwang

2005-01-01

86

A PEG assisted sol–gel synthesis of LiFePO 4 as cathodic material for lithium ion cells  

Microsoft Academic Search

In order to obtain fine-particle LiFePO4 with excellent electrochemical performance, LiFePO4\\/C powders were synthesized by a poly(ethylene glycol) (PEG) assisted sol–gel method. All samples were characterized by X-ray powder diffraction and scanning electron microscopy, and their electrochemical properties were investigated by cycle voltammograms and charge–discharge tests. The sample, synthesized with the nPEG\\/nLFP=1:1 under sintering temperature of 600°C, possesses the global

Zhihui Xu; Liang Xu; Qiongyu Lai; Xiaoyang Ji

2007-01-01

87

The hydrothermal synthesis and characterization of olivines and related compounds for electrochemical applications  

Microsoft Academic Search

A number of cathodes are being considered for the next generation of lithium ion batteries to replace the expensive LiCoO2 presently used. Besides the layered oxides, such as LiNiyMnyCo1?2yO2, a leading candidate is lithium iron phosphate with the olivine structure. Although this material is inherently low cost, a manufacturing process that produces electrochemically-active LiFePO4 at a low cost is also

Jiajun Chen; Michael J. Vacchio; Shijun Wang; Natalya Chernova; Peter Y. Zavalij; M. Stanley Whittingham

2008-01-01

88

Raman and NMR studies of aged LiFePO4 cathode  

NASA Astrophysics Data System (ADS)

The carbon coated LiFePO4 nanoparticles are used in advanced lithium-ion batteries due to low cost, high energy and power density. In this paper Raman spectroscopy is used to analyze the degradation of carbon coating around these nanoparticles in several commercial cells aged with different C-rate. Magic angle spinning 7Li Nuclear magnetic resonance (NMR) spectroscopy is used to characterize these nanoparticles for the presence of Li. In Raman spectroscopy data, structural change in the carbon leading to low electrical conductivity is observed for the cells aged at higher C-rate. In NMR spectroscopy data, isotropic 7Li peak is observed in an unaged cell, while the similar peak is absent in the aged cells.

Nagpure, Shrikant C.; Bhushan, Bharat; Babu, S. S.

2012-10-01

89

Li-Ion Batteries from LiFePO4 Cathode and Anatase\\/Graphene Composite Anode for Stationary Energy Storage  

Microsoft Academic Search

Li-ion batteries based on LiFePO4 cathode and anatase TiO2\\/graphene anode were investigated for possible stationary energy storage application. Fine-structured LiFePO4 was synthesized by novel molten surfactant approach. Anatase TiO2\\/graphene nanocomposite was prepared via self assembly method. The full cell that operated at flat 1.6V demonstrated negligible fade after more than 700 cycles. The LiFePO4\\/TiO2 combination Li-ion battery is inexpensive, environmentally

Daiwon Choi; Donghai Wang; Vilayanur V. Viswanathan; In-Tae Bae; Wei Wang; Zimin Nie; Jiguang Zhang; Gordon L. Graff; Jun Liu; Zhenguo Yang; Tien Q. Duong

2009-01-01

90

Carboxylic acid-assisted solid-state synthesis of LiFePO 4 \\/C composites and their electrochemical properties as cathode materials for lithium-ion batteries  

Microsoft Academic Search

To enhance the capability of LiFePO4 materials, we attempted to coat carbon by incorporating various organic carboxylic acids as carbon sources. The purity of\\u000a LiFePO4 was confirmed by XRD analysis. Galvanostatic cycling, cyclic voltammetry, electric impedance spectroscopy, and conductivity\\u000a measurements were used to evaluate the material’s electrochemical performance. The best cell performance was delivered by\\u000a the sample coated with 60 wt.%

George Ting-Kuo Fey; Tung-Lin Lu; Feng-Yu Wu; Wen-Hsien Li

2008-01-01

91

Electrochemical properties of carbon-coated LiFePO 4 synthesized by a modified mechanical activation process  

Microsoft Academic Search

Carbon-coated lithium iron phosphate (LiFePO4\\/C) composites were synthesized by conventional mechanical activation (MA) process and also by a modified MA process. Phase-pure particles were obtained of ?100nm size with a nano-meter thick web of carbon surrounding the particles. The composite prepared by the modified MA process shows good performance as cathode material in lithium cells at room temperature. A high

Jae-Kwang Kim; Gouri Cheruvally; Jou-Hyeon Ahn; Gil-Chan Hwang; Jin-Beom Choi

2008-01-01

92

Comparison between different LiFePO 4 synthesis routes and their influence on its physico-chemical properties  

Microsoft Academic Search

LiFePO4 powders were synthesized under several different conditions (solid state reactions at high temperatures, co-precipitation in aqueous medium, hydrothermal synthesis or mechanochemical activation). The samples were characterized by X-ray diffraction (XRD), chemical titration and their electrochemical performance were investigated in terms of cycling behavior. We also report, in this work, the benefit of introducing an electronic conductor precursor (typically a

Sylvain Franger; Frédéric Le Cras; Carole Bourbon; Hélène Rouault

2003-01-01

93

Lithium oxalyldifluoroborate\\/carbonate electrolytes for LiFePO 4\\/artificial graphite lithium-ion cells  

Microsoft Academic Search

The electrolytes based on lithium oxalyldifluoroborate (LiODFB) and carbonates have been systematically investigated for LiFePO4\\/artificial graphite (AG) cells, by ionic conductivity test and various electrochemical tests, such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge–discharge test. The conductivity of nine electrolytes as a function of solvent composition and LiODFB salt concentration has been studied. The coulombic efficiency of

Jie Li; Keyu Xie; Yanqing Lai; Zhi’an Zhang; Fanqun Li; Xin Hao; Xujie Chen; Yexiang Liu

2010-01-01

94

Nanoscopic scale studies of LiFePO 4 as cathode material in lithium-ion batteries for HEV application  

Microsoft Academic Search

We present a review of the structural properties of LiFePO4. Depending on the mode of preparation, different impurities can poison this material. These impurities are identified and\\u000a a quantitative estimate of their concentrations is deduced from the combination of X-ray diffraction analysis, Fourier transform\\u000a infrared spectroscopy, Raman spectroscopy, and magnetic measurements. An optimized preparation provides samples with carbon-coated\\u000a particles free

C. M. Julien; A. Mauger; A. Ait-Salah; M. Massot; F. Gendron; K. Zaghib

2007-01-01

95

The development of low cost LiFePO 4-based high power lithium-ion batteries  

Microsoft Academic Search

Pouch type LiFePO4-natural graphite lithium-ion cells were cycled at constant current with periodic pulse-power testing in several different configurations. Components were analyzed after cycling with electrochemical, Raman and TEM techniques to determine capacity fade mechanisms. The cells with carbon-coated current collectors in the cathode and LiBOB-salt electrolyte showed the best performance stability. In many cases, iron species were detected on

Kathryn Striebel; Joongpyo Shim; Azucena Sierra; Hui Yang; Xiangyun Song; Robert Kostecki; Kathryn McCarthy

2005-01-01

96

A comparison study of capacity degradation mechanism of LiFePO 4-based lithium ion cells  

Microsoft Academic Search

The physical properties and electrochemical performance of two kinds of commercialized LiFePO4 (hereafter abbreviated as LFP) were analyzed. And the cycle stability of the two kinds of material in the 18,650 type lithium ion cells was measured at different charge cut-off voltage (3.65,3.8,4.0 and 4.2V). The two kinds of material showed remarkable difference. One has good cycle stability but another

Hui-Fen Jin; Zhen Liu; Yan-Mei Teng; Jun-kui Gao; Yong Zhao

2009-01-01

97

A LiTi 2O 4–LiFePO 4 novel lithium-ion polymer battery  

Microsoft Academic Search

A new type of lithium-ion polymer cell based on a LiTi2O4 anode, a LiFePO4 cathode and a PVdF-based gel electrolyte is reported and discussed. The cell operates with a very flat voltage profile evolving around 2 V and cycles with negligible capacity fading and with a high rate. These features, combined with the low cost and the low toxicity of

L Persi; F Croce; B Scrosati

2002-01-01

98

Cycling performance of low-cost lithium ion batteries with natural graphite and LiFePO 4  

Microsoft Academic Search

Low-cost lithium ion batteries with LiFePO4 and natural graphite were cycled in 1M LiBF4+EC\\/DEC at 100% depth of discharge and 25°C in order to investigate cycle performance and diagnostics for capacity fading. The 12cm2 pouch cell showed 65% of capacity retention at 5C compared to that at C\\/25. The cell showed 80% of initial capacity after 80 cycles and its

Joongpyo Shim; Kathryn A. Striebel

2003-01-01

99

In situ Raman spectroscopy of LiFePO4: size and morphology dependence during charge and self-discharge  

NASA Astrophysics Data System (ADS)

Previous studies of the size dependent properties of LiFePO4 have focused on the diffusion rate or phase transformation pathways by bulk analysis techniques such as x-ray diffraction (XRD), neutron diffraction and electrochemistry. In this work, in situ Raman spectroscopy was used to study the surface phase change during charge and self-discharge on a more localized scale for three morphologies of LiFePO4: (1) 25 ± 6 nm width nanorods, (2) 225 ± 6 nm width nanorods and (3) ?2 ?m porous microspheres. Both the large nanorod and microsphere geometries showed incomplete delithiation at the end of charge, which was most likely caused by anti-site defects along the 1D diffusion channels in the bulk of the larger particles. Based on the in situ Raman measurements, all of the morphologies studied exhibited self-discharge with time. Among them, the smallest FePO4 particles self-discharged (lithiated) the fastest. While nanostructuring LiFePO4 can offer advantages in terms of lowering anti-site defects within particles, it also creates new problems due to high surface energies that allow self-discharge. The in situ Raman spectroscopy also showed that carbon coating did not provide significant improvement to the stability of the lithiated particles.

Wu, Jing; Krishna Phani Dathar, Gopi; Sun, Chunwen; Theivanayagam, Murali G.; Applestone, Danielle; Dylla, Anthony G.; Manthiram, Arumugam; Henkelman, Graeme; Goodenough, John B.; Stevenson, Keith J.

2013-10-01

100

Magnetic and diffusive nature of LiFePO4 investigated by muon spin rotation and relaxation  

NASA Astrophysics Data System (ADS)

In order to elucidate the magnetism and Li diffusion in LiFePO4, we have measured muon-spin rotation and relaxation (?+SR) spectra for the polycrystalline LiFePO4 sample in the temperature range between 1.8 and 500 K. Below TN˜52 K, two oscillatory signals together with one fast relaxation signal were clearly found in the zero-field (ZF) ?+SR spectrum. The three signals are reasonably explained using an antiferromagnetic (AF) spin structure proposed by neutron measurements, because electrostatic potential calculations suggests multiple different muon sites in the LiFePO4 lattice. However, the AF ordered moment estimated from ?+SR was about 3/4 of that reported by neutron, probably due to a different time window between the two techniques. In the paramagnetic state, ZF and longitudinal-field (LF) ?+SR spectra exhibited a dynamic nuclear field relaxation. From the temperature dependence of the field fluctuation rate, a diffusion coefficient of Li+ ions (DLi) at 300 K was estimated about 3.6×10-10 cm2/s, assuming that diffusing Li+ ions jump between the regular site and interstitial sites.

Sugiyama, Jun; Nozaki, Hiroshi; Harada, Masashi; Kamazawa, Kazuya; Ofer, Oren; Månsson, Martin; Brewer, Jess H.; Ansaldo, Eduardo J.; Chow, Kim H.; Ikedo, Yutaka; Miyake, Yasuhiro; Ohishi, Kazuki; Watanabe, Isao; Kobayashi, Genki; Kanno, Ryoji

2011-08-01

101

Carbon-coated LiFePO4-porous carbon composites as cathode materials for lithium ion batteries  

NASA Astrophysics Data System (ADS)

This work introduces a facile strategy for the synthesis of carbon-coated LiFePO4-porous carbon (C-LiFePO4-PC) composites as a cathode material for lithium ion batteries. The LiFePO4 particles obtained are about 200 nm in size and homogeneously dispersed in porous carbon matrix. These particles are further coated with the carbon layers pyrolyzed from sucrose. The C-LiFePO4-PC composites display a high initial discharge capacity of 152.3 mA h g-1 at 0.1 C, good cycling stability, as well as excellent rate capability (112 mA h g-1 at 5 C). The likely contributing factors to the excellent electrochemical performance of the C-LiFePO4-PC composites could be related to the combined effects of enhancement of conductivity by the porous carbon matrix and the carbon coating layers. It is believed that further carbon coating is a facile and effective way to improve the electrochemical performance of LiFePO4-PC.

Ni, Haifang; Liu, Jinkun; Fan, Li-Zhen

2013-02-01

102

Carbon-coated LiFePO4-porous carbon composites as cathode materials for lithium ion batteries.  

PubMed

This work introduces a facile strategy for the synthesis of carbon-coated LiFePO(4)-porous carbon (C-LiFePO(4)-PC) composites as a cathode material for lithium ion batteries. The LiFePO(4) particles obtained are about 200 nm in size and homogeneously dispersed in porous carbon matrix. These particles are further coated with the carbon layers pyrolyzed from sucrose. The C-LiFePO(4)-PC composites display a high initial discharge capacity of 152.3 mA h g(-1) at 0.1 C, good cycling stability, as well as excellent rate capability (112 mA h g(-1) at 5 C). The likely contributing factors to the excellent electrochemical performance of the C-LiFePO(4)-PC composites could be related to the combined effects of enhancement of conductivity by the porous carbon matrix and the carbon coating layers. It is believed that further carbon coating is a facile and effective way to improve the electrochemical performance of LiFePO(4)-PC. PMID:23389625

Ni, Haifang; Liu, Jinkun; Fan, Li-Zhen

2013-02-06

103

In situ Raman spectroscopy of LiFePO4: size and morphology dependence during charge and self-discharge.  

PubMed

Previous studies of the size dependent properties of LiFePO4 have focused on the diffusion rate or phase transformation pathways by bulk analysis techniques such as x-ray diffraction (XRD), neutron diffraction and electrochemistry. In this work, in situ Raman spectroscopy was used to study the surface phase change during charge and self-discharge on a more localized scale for three morphologies of LiFePO4: (1) 25 ± 6 nm width nanorods, (2) 225 ± 6 nm width nanorods and (3) ?2 ?m porous microspheres. Both the large nanorod and microsphere geometries showed incomplete delithiation at the end of charge, which was most likely caused by anti-site defects along the 1D diffusion channels in the bulk of the larger particles. Based on the in situ Raman measurements, all of the morphologies studied exhibited self-discharge with time. Among them, the smallest FePO4 particles self-discharged (lithiated) the fastest. While nanostructuring LiFePO4 can offer advantages in terms of lowering anti-site defects within particles, it also creates new problems due to high surface energies that allow self-discharge. The in situ Raman spectroscopy also showed that carbon coating did not provide significant improvement to the stability of the lithiated particles. PMID:24067625

Wu, Jing; Dathar, Gopi Krishna Phani; Sun, Chunwen; Theivanayagam, Murali G; Applestone, Danielle; Dylla, Anthony G; Manthiram, Arumugam; Henkelman, Graeme; Goodenough, John B; Stevenson, Keith J

2013-09-25

104

Particle size dependent confinement and lattice strain effects in LiFePO4.  

PubMed

We report the intrinsic electronic properties of LiFePO4 (LFP) with different particle sizes measured by broad-band impedance spectroscopy and diffuse reflectance spectroscopy. The electronic properties show typical size-dependent effects with decreasing particle size (up to 150 nm). However, at the nanoscale level, we observed an enhancement in the polaronic conductivity about an order of magnitude. We found that the origin of the enhanced electronic conductivity in LFP is due to the significant lattice strain associated with the reduction of particle size. The observed lattice strain component corresponds to the compressive part which leads to a decrease in the hopping length of the polarons. We reproduce nonlinearities in the transport properties of LFP with particle size, to capture the interplay between confinement and lattice strain, and track the effects of strain on the electron-phonon interactions. These results could explain why nano-sized LFP has a better discharge capacity and higher rate capability than the bulk counterpart. We suggest that these new correlations will bring greater insight and better understanding for the optimization of LFP as a cathode material for advanced lithium ion batteries. PMID:24091905

Shahid, Raza; Murugavel, Sevi

2013-10-16

105

Synthesis and electrochemical characterizations of nano-crystalline LiFePO 4 and Mg-doped LiFePO 4 cathode materials for rechargeable lithium-ion batteries  

Microsoft Academic Search

Nano-crystalline LiFePO4 and LiMg0.05Fe0.95PO4 cathode materials were synthesized by sol–gel method in argon atmosphere using succinic acid as a chelating agent. Physico-chemical\\u000a characterizations were done by thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy,\\u000a transmittance electron microscopy, and Raman spectroscopy. Electrochemical behavior of the cathode materials were analyzed\\u000a using cyclic voltammetry, and galvanostatic charge\\/discharge cycling studies were employed

D. Arumugam; G. Paruthimal Kalaignan; P. Manisankar

2009-01-01

106

Effect of complexing agents on the electrochemical performance of LiFePO4/C prepared by sol-gel method  

PubMed Central

LiFePO4/C is synthesized via sol-gel method using Fe3+ as iron sources and different complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.%, and the X-ray diffraction experiment confirms that all samples are pure single phase indexed with the orthorhombic Pnma space group. The particle size of the LiFePO4/C synthesized by acetic acid as a complexing agent is very fine with a size of 200 nm. The electrochemical performance of this material, including reversible capacity, cycle number, and charge-discharge characteristics, is better than those of LiFePO4/C synthesized by other complexing agents. The cell of this sample can deliver a discharge capacity of 161.1 mAh g-1 at the first cycle. After 30 cycles, the capacity decreases to 157.5 mAh g-1, and the capacity fading rate is 2.2%. The mechanism is studied to explain the effect of a complexing agent on the synthesis of LiFePO4/C by sol-gel method. The results show that the complexing agent with a low stability constant may be proper for the synthetic process of LiFePO4/C via sol-gel method.

2012-01-01

107

Impedance Spectroscopy Studies of Nano-Crystalline LiFePO4 Cathode Synthesized by Hydrothermal Method  

NASA Astrophysics Data System (ADS)

LiFePO4 has become of great interest as storage cathodes for rechargeable lithium batteries because of their high energy density, low raw materials cost, environmental friendliness, high thermal stability. In the present investigation, lithium iron phosphate (LiFePO4) cathode material has been prepared by using hydrothermal synthesis. The structure of the sample has been studies by using X-ray diffraction. The XRD spectrum exhibited different characteristic peaks along with (311) predominant orientation corresponding to an orthorhombic crystal structure with Pnma space group. Electrical and dielectric properties were studied over a frequency range of 1 Hz - 1 MHz at different temperatures. The electrical conductivity was found to be increased with increasing temperature following Arrhenius relation with an estimated activation energy of 0.44 eV. The dielectric properties were analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. The evolution of the complex permittivity as a function of frequency and temperature was investigated. Several important parameters such as activation energy, ionic hopping frequency, carrier concentration, ionic mobility and diffusion coefficient etc, were determined.

Rosaiah, P.; Hussain, O. M.

108

A novel network composite cathode of LiFePO 4\\/multiwalled carbon nanotubes with high rate capability for lithium ion batteries  

Microsoft Academic Search

A novel network composite cathode was prepared by mixing LiFePO4 particles with multiwalled carbon nanotubes for high rate capability. LiFePO4 particles were connected by multiwalled carbon nanotubes to form a three-dimensional network wiring. The web structure can improve electron transport and electrochemical activity effectively. The initial discharge capacity was improved to be 155mAh\\/g at C\\/10 rate (0.05mA\\/cm2) and 146mAh\\/g at

Xinlu Li; Feiyu Kang; Xinde Bai; Wanci Shen

2007-01-01

109

Intergrown Li2FeSiO4·LiFePO4-C nanocomposites as high-capacity cathode materials for lithium-ion batteries.  

PubMed

Intergrown Li2FeSiO4·LiFePO4-C nanocomposites with different compositions were synthesized by a tartaric acid assisted sol-gel method. The 0.96Li2FeSiO4·0.04LiFePO4-C nanocomposites exhibited greatly enhanced electrochemical properties, attaining a high discharge capacity up to 284.7 mA h g(-1) (equal to ca. 1.72 Li(+) per molecule) at 45 °C. PMID:23467304

Gao, Haiyan; Hu, Zhe; Zhang, Kai; Cheng, Fangyi; Chen, Jun

2013-04-14

110

Effect of C and Au additives produced by simple coaters on the surface and the electrochemical properties of nanosized LiFePO 4  

Microsoft Academic Search

We examined the use of two conductive additives (C and Au) to boost the performance of lithium iron phosphate as a positive electrode material for lithium ion batteries. The phosphate was prepared by using a new, fast synthetic method that provides nanosized particles. Carbon and gold were sputtered on LiFePO4. Additional sample was an intimate mixture of carbon and phosphate

Julián Morales; Rafael Trócoli; Enrique Rodríguez-Castellón; Sylvain Franger; Jesús Santos-Peña

2009-01-01

111

The structure of tavorite LiFePO(4)(OH) from diffraction and GGA + U studies and its preliminary electrochemical characterization.  

PubMed

Pure tavorite LiFePO(4)(OH) was synthesized through a hydrothermal route. A fine structural analysis was done by X-ray and neutron diffraction techniques. The structure consists of a three-dimensional network with iron(iii) octahedra (FeO(6)) sharing corners, forming chains that run along the b direction. These chains are interconnected by PO(4) tetrahedra, such as the resulting framework encloses tunnels of two different sizes running along the a and c axis. The lithium and hydrogen atoms were precisely localized in these tunnels. Theoretical (GGA + U) calculations performed for LiFePO(4)X materials (X = OH, F) confirmed our results and revealed that a unique lithium position is expected in LiFePO(4)(OH), as experimentally observed. For the first time, lithium intercalation was shown to occur in LiFePO(4)(OH) through the reduction of Fe(3+) to Fe(2+) at an average voltage of approximately 2.3 V (vs. Li(+)/Li) with a good cyclability. PMID:20440440

Marx, Nicolas; Croguennec, Laurence; Carlier, Dany; Wattiaux, Alain; Cras, Frédéric Le; Suard, Emmanuelle; Delmas, Claude

2010-05-01

112

Hierarchical LiFePO4/C microspheres with high tap density assembled by nanosheets as cathode materials for high-performance Li-ion batteries.  

PubMed

In this paper, LiFePO(4)/C microspheres consisting of closely packed nanosheets have been synthesized via a simple solvothermal method and a subsequent carbon coating procedure. In order to clarify the microstructure of the product, the as-prepared composite has been characterized by various techniques, such as powder x-ray diffraction, scanning electron microscopy, energy dispersive spectrum, Raman spectroscopy and high-resolution transmission microscopy. Results show that the LiFePO(4)/C microspheres are uniform with a particle size of 8-10 ?m. The microspheres are composed of densely compacted nanosheets with a thickness of 20-30 nm. The gaps between the nanosheets are estimated to be 10-50 nm; a carbon layer with a thickness of ~4 nm is coated on the surface of the LiFePO(4) spheres. The tap density of the LiFePO(4)/C composite reaches up to 1.5 g cm(-3). As cathode material for Li-ion batteries, the composite exhibits a high capacity: 155 mAh g(-1), 144 mAh g(-1), 129 mAh g(-1), and 104 mAh g(-1) at 0.1 C, 1 C, 5 C and 10 C, respectively. Furthermore, the material also shows good cycling stability at both low and high current rates. The unique nanostructure of the material promises its excellent electrochemical properties as a cathode material for lithium batteries. PMID:23117189

Wei, Wei; Chen, Dezhi; Wang, Ruining; Guo, Lin

2012-11-01

113

Hierarchical LiFePO4/C microspheres with high tap density assembled by nanosheets as cathode materials for high-performance Li-ion batteries  

NASA Astrophysics Data System (ADS)

In this paper, LiFePO4/C microspheres consisting of closely packed nanosheets have been synthesized via a simple solvothermal method and a subsequent carbon coating procedure. In order to clarify the microstructure of the product, the as-prepared composite has been characterized by various techniques, such as powder x-ray diffraction, scanning electron microscopy, energy dispersive spectrum, Raman spectroscopy and high-resolution transmission microscopy. Results show that the LiFePO4/C microspheres are uniform with a particle size of 8-10 ?m. The microspheres are composed of densely compacted nanosheets with a thickness of 20-30 nm. The gaps between the nanosheets are estimated to be 10-50 nm a carbon layer with a thickness of ˜4 nm is coated on the surface of the LiFePO4 spheres. The tap density of the LiFePO4/C composite reaches up to 1.5 g cm-3. As cathode material for Li-ion batteries, the composite exhibits a high capacity: 155 mAh g-1, 144 mAh g-1, 129 mAh g-1, and 104 mAh g-1 at 0.1 C, 1 C, 5 C and 10 C, respectively. Furthermore, the material also shows good cycling stability at both low and high current rates. The unique nanostructure of the material promises its excellent electrochemical properties as a cathode material for lithium batteries.

Wei, Wei; Chen, Dezhi; Wang, Ruining; Guo, Lin

2012-11-01

114

Nonequilibrium Phase Transformation and Particle Shape Effect in LiFePO4 Materials for Li-Ion Batteries  

SciTech Connect

The nonequilibrium phase transformation and particle shape effects in LiFePO4 materials of Li-ion batteries are explored in this work. A continuum model employing the mushy-zone (MZ) approach, accounting for sluggish Li diffusion across the two-phase boundary, has been developed to study the kinetically-induced nonequilibrium phenomenon in Li-ion batteries. A theoretical analysis is presented to show that the nonequilibrium miscibility gap expands and shifts to higher Li composition at high discharge rates, due to insufficient compositional readjustments at the two-phase boundary. Furthermore, critical effects of particle shape on nonequilibrium phase transformation and discharge capacity have been discovered by the model.

Mukherjee, Partha P [ORNL

2011-01-01

115

Vacancy-Driven Anisotropic Defect Distribution in the Battery-Cathode Material LiFePO4  

NASA Astrophysics Data System (ADS)

Li-ion mobility in LiFePO4, a key property for energy applications, is impeded by Fe antisite defects (FeLi) that form in select b-axis channels. Here we combine first-principles calculations, statistical mechanics, and scanning transmission electron microscopy to identify the origin of the effect: Li vacancies (VLi) are confined in one-dimensional b-axis channels, shuttling between neighboring FeLi. Segregation in select channels results in shorter FeLi-FeLi spans, whereby the energy is lowered by the VLi’s spending more time bound to end-point FeLi’s. VLi-FeLi-VLi complexes also form, accounting for observed electron energy loss spectroscopy features.

Lee, Jaekwang; Zhou, Wu; Idrobo, Juan C.; Pennycook, Stephen J.; Pantelides, Sokrates T.

2011-08-01

116

The effect of Cr doping on Li ion diffusion in LiFePO4 from first principles investigations and Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

Using the adiabatic trajectory method, the migration energy barriers for the migration of Li ions and Cr ions along the one-dimensional diffusion pathway in pure and Cr doped LiFePO4 are obtained from first principles calculations. The results show that while Li ions can diffuse along the diffusion pathway easily, Cr ions do not easily diffuse away from their initial positions. This means that the heavy Cr ions will block the one-dimensional diffusion pathway of the material. Monte Carlo simulations are performed to evaluate the influences of the blocking behaviours on the electrochemical performance of LiFePO4 cathode material for Li ion secondary batteries. The results show that the evaluated capacity is highly sensitive to the amount of the dopant, the size of the super-cell being used for simulation (particle size of the powder cathode material) and the Monte Carlo steps for statistics (charge-discharge current density).

Ouyang, C. Y.; Shi, S. Q.; Wang, Z. X.; Li, H.; Huang, X. J.; Chen, L. Q.

2004-04-01

117

Flexible, solid electrolyte-based lithium battery composed of LiFePO4 cathode and Li4Ti5O10 anode for applications in smart textiles  

Microsoft Academic Search

Here we report fabrication of flexible and stretchable battery composed of strain free LiFePO4 cathode, Li4Ti5O10 anode and a solid poly ethylene oxide (PEO) electrolyte as a separator layer. The battery is developed in a view of smart textile applications. Featuring solid thermoplastic electrolyte as a key enabling element this battery is potentially extrudable or drawable into fibers or thin

Yang Liu; Maksim Skorobogatiy

2011-01-01

118

High-temperature carbon-coated aluminum current collector for enhanced power performance of LiFePO 4 electrode of Li-ion batteries  

Microsoft Academic Search

The charge\\/discharge capacity and cycle stability at high C-rate of LiFePo4 (LFPO) electrodes using three types of Al current collectors, including smooth un-etched Al foil, anodization-etched Al foil, and the etched Al foil covered with a conformal C coating grown at 600°C in CH4, were investigated. The results unequivocally demonstrate the strong effects exerted by the surface structure and composition

Hsien-Chang Wu; Hung-Chun Wu; Eric Lee; Nae-Lih Wu

2010-01-01

119

Fine-particle lithium iron phosphate LiFePO 4 synthesized by a new low-cost aqueous precipitation technique  

Microsoft Academic Search

Phase pure, homogeneous, and well-crystallized lithium iron phosphate LiFePO4 was synthesized by aqueous co-precipitation of an Fe(II) precursor material and succeeding heat treatment in nitrogen. The particle morphology of the precursor is preserved during the heat treatments. Excellent electrochemical properties in terms of capacity, reversibility, cycling stability and rate capability have been achieved. The thermal stability of charged electrodes is

G Arnold; J Garche; R Hemmer; S Ströbele; C Vogler; M Wohlfahrt-Mehrens

2003-01-01

120

Preparation and characterization of carbon-coated LiFePO 4 cathode materials for lithium-ion batteries with resorcinol–formaldehyde polymer as carbon precursor  

Microsoft Academic Search

LiFePO4\\/C composites were synthesized by two methods using home-made amorphous nano-FePO4 as the iron precursor and soluble starch, sucrose, citric acid, and resorcinol–formaldehyde (RF) polymer as four carbon precursors, respectively. The crystalline structures, morphologies, compositions, electrochemical performances of the prepared powders were investigated with XRD, TEM, Raman, and cyclic voltammogram method. The results showed that employing soluble starch and sucrose

Yachao Lan; Xiaodong Wang; Jingwei Zhang; Jiwei Zhang; Zhishen Wu; Zhijun Zhang

2011-01-01

121

A poly(3-decyl thiophene)-modified separator with self-actuating overcharge protection mechanism for LiFePO 4-based lithium ion battery  

Microsoft Academic Search

A voltage-sensitive separator is prepared simply by impregnating electroactive poly(3-decylthiophene) (P3DT) polymer into a commercial porous separator and tested for a self-actuating control of overcharge voltage of LiFePO4\\/C lithium-ion batteries. The experimental results demonstrate that this type of separator can be reversibly p-doped and dedoped to maintain the cell's voltage at a safe value of ?4V even at high rate

S. L. Li; L. Xia; H. Y. Zhang; X. P. Ai; H. X. Yang; Y. L. Cao

2011-01-01

122

A lithium ion battery using nanostructured Sn–C anode, LiFePO 4 cathode and polyethylene oxide-based electrolyte  

Microsoft Academic Search

In this work we report a lithium ion battery based on a nanostructured Sn–C anode, an improved lithium iron phosphate, LiFePO4, cathode and a polyethylene oxide-based electrolyte. The battery has a solid-like configuration, high safety and can operate at room temperature with a stable capacity of the order of 120mAh g?1 at a voltage of 2.8V. These properties candidate the

Jusef Hassoun; Dong-Ju Lee; Yang-Kook Sun; Bruno Scrosati

2011-01-01

123

Direct evidence of concurrent solid-solution and two-phase reactions and the nonequilibrium structural evolution of LiFePO4.  

PubMed

Lithium-ion batteries power many portable devices and in the future are likely to play a significant role in sustainable-energy systems for transportation and the electrical grid. LiFePO(4) is a candidate cathode material for second-generation lithium-ion batteries, bringing a high rate capability to this technology. LiFePO(4) functions as a cathode where delithiation occurs via either a solid-solution or a two-phase mechanism, the pathway taken being influenced by sample preparation and electrochemical conditions. The details of the delithiation pathway and the relationship between the two-phase and solid-solution reactions remain controversial. Here we report, using real-time in situ neutron powder diffraction, the simultaneous occurrence of solid-solution and two-phase reactions after deep discharge in nonequilibrium conditions. This work is an example of the experimental investigation of nonequilibrium states in a commercially available LiFePO(4) cathode and reveals the concurrent occurrence of and transition between the solid-solution and two-phase reactions. PMID:22482702

Sharma, Neeraj; Guo, Xianwei; Du, Guodong; Guo, Zaiping; Wang, Jiazhou; Wang, Zhaoxiang; Peterson, Vanessa K

2012-04-30

124

A new phosphate-formate precursor method for the preparation of carbon coated nano-crystalline LiFePO 4  

Microsoft Academic Search

Mixed phosphate-formate precursors, LiFePO4Hx(HCOO)x·yH2O (x?1, 1

V. Koleva; E. Zhecheva; R. Stoyanova

2009-01-01

125

Sucrose-assisted loading of LiFePO4 nanoparticles on graphene for high-performance lithium-ion battery cathodes.  

PubMed

A simple approach for loading LiFePO4 (LFP) nanoparticles on graphene (G) that could assemble amorphous LiFePO4 nanoparticles into a stable, crystalline, graphene-modified layered materials (G-S-LFP, S=sucrose) by using graphene as building block and sucrose as a linker has yet to be developed. On the basis of differential scanning calorimetric and transmission electron microscopy analysis of the samples from controlled experiment, a possible mechanism was proposed to explain the "linker" process of LFP and graphene with sucrose as the linker. The electrochemical properties of the samples as cathode material for lithium-ion batteries were studied by cyclic voltammogrametry and galvanostatic methods. Results showed that G-S-LFP displayed superior lithium-storage capability with current density changes randomly form 0.5 to 10 C. The significant improvement for rate and cycle performance could be attributed to the high conductivity of the graphene host, the high crystallinity, and the layered structure. PMID:23468054

Wu, Yongmin; Wen, Zhenhai; Feng, Hongbin; Li, Jinghong

2013-03-06

126

Aristarchus Olivine in Context with Circum-Imbrium Olivine Deposits  

NASA Astrophysics Data System (ADS)

We investigate the origin of olivine-bearing deposits in Aristarchus Crater ejecta. Given that spectrally similar olivine is found circum Imbrium, olivine in Aristarchus may represent reexposed Imbrium ejecta or other impact transported deposits.

Wiseman, S. M.; Donaldson Hanna, K. L.; Mustard, J. F.; Isaacson, P. J.; Pieters, C. M.; Jolliff, B. L.

2012-07-01

127

An experimental investigation of olivine morphology  

Microsoft Academic Search

Olivine crystals can adopt ten types of shape. Experimental crystallization of eight rock melts shows that there is a systematic change from polyhedral or granular olivines --> hopper olivines --> branching olivines --> randomly oriented chain olivines --> parallel-growth chain olivines --> chain+lattice olivines --> plate or feather olivines, with increase in cooling rate and with increase in degree of

Colin H. Donaldson

1976-01-01

128

An experimental investigation of olivine morphology  

Microsoft Academic Search

Olivine crystals can adopt ten types of shape. Experimental crystallization of eight rock melts shows that there is a systematic change from polyhedral or granular olivines ? hopper olivines ? branching olivines ? randomly oriented chain olivines ? parallel-growth chain olivines ? chain+lattice olivines ? plate or feather olivines, with increase in cooling rate and with increase in degree of

Colin H. Donaldson

1976-01-01

129

Synthesis of TiO2 hollow nanofibers by co-axial electrospinning and its superior lithium storage capability in full-cell assembly with olivine phosphate  

NASA Astrophysics Data System (ADS)

We report the formation and extraordinary Li-storage properties of TiO2 hollow nanofibers by co-axial electrospinning in both the half-cell and full-cell configurations. Li-insertion properties are first evaluated as anodes in the half-cell configuration (Li/TiO2 hollow nanofibers) and we found that reversible insertion of ~0.45 moles is feasible at a current density of 100 mA g-1. The half-cell displayed a good cyclability and retained 84% of its initial reversible capacity after 300 galvanostatic cycles. The full-cell is fabricated with a commercially available olivine phase LiFePO4 cathode under optimized mass loading. The LiFePO4/TiO2 hollow nanofiber cell delivered a reversible capacity of 103 mA h g-1 at a current density of 100 mA g-1 with an operating potential of ~1.4 V. Excellent cyclability is noted for the full-cell configuration, irrespective of the applied current densities, and it retained 88% of reversible capacity after 300 cycles in ambient conditions at a current density of 100 mA g-1.We report the formation and extraordinary Li-storage properties of TiO2 hollow nanofibers by co-axial electrospinning in both the half-cell and full-cell configurations. Li-insertion properties are first evaluated as anodes in the half-cell configuration (Li/TiO2 hollow nanofibers) and we found that reversible insertion of ~0.45 moles is feasible at a current density of 100 mA g-1. The half-cell displayed a good cyclability and retained 84% of its initial reversible capacity after 300 galvanostatic cycles. The full-cell is fabricated with a commercially available olivine phase LiFePO4 cathode under optimized mass loading. The LiFePO4/TiO2 hollow nanofiber cell delivered a reversible capacity of 103 mA h g-1 at a current density of 100 mA g-1 with an operating potential of ~1.4 V. Excellent cyclability is noted for the full-cell configuration, irrespective of the applied current densities, and it retained 88% of reversible capacity after 300 cycles in ambient conditions at a current density of 100 mA g-1. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01128c

Zhang, X.; Aravindan, V.; Kumar, P. Suresh; Liu, H.; Sundaramurthy, J.; Ramakrishna, S.; Madhavi, S.

2013-06-01

130

Olivine-liquid equilibrium  

Microsoft Academic Search

A number of experiments have been conducted in order to study the equilibria between olivine and basaltic liquids and to try and understand the conditions under which olivine will crystallize. These experiments were conducted with several basaltic compositions over a range of temperature (1150–1300° C) and oxygen fugacity (10-0.68–10-12 atm.) at one atmosphere total pressure. The phases in these experimental

P. L. Roeder; R. F. Emslie

1970-01-01

131

REE Diffusion in Olivine  

NASA Astrophysics Data System (ADS)

Diffusion of rare earth elements has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of REE aluminate garnet powder and synthetic forsterite powder in 3:1 proportions. Experiments were prepared by enclosing source material and polished forsterite in platinum capsules, which were crimped shut. For experiments on natural olivine, samples were placed with the source in AgPd capsules, which were sealed under vacuum in silica glass ampoules with a solid buffer to buffer at NNO. Prepared capsules were then annealed in 1 atm furnaces for times ranging from an hour to several weeks, at temperatures from 850 to 1300°C. REE distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for Dy diffusion in forsterite: D = 2.3x10-10 exp(-273 kJ mol-1/RT) m2sec-1. Diffusivities of Yb and La in forsterite appear similar, and preliminary results for Dy diffusion in natural olivine also suggest similar diffusivities. REE diffusivities in forsterite are about an order of magnitude faster than those of REE+3 in enstatite (Cherniak and Liang, 2007). However, if the Arrhenius relation above is extrapolated up to 1450C, it yields diffusivities about three orders of magnitude smaller than those determined for REE diffusion in olivine by Spandler et al. (2007). Work is currently underway in further characterizing diffusion in Fe-bearing olivine. If an Arrhenius relation similar to that for forsterite is found to apply, timescales for preservation of REE signatures in olivine-hosted melt inclusions may be relatively long. Cherniak and Liang (2007) GCA 71, 1324-1340; Spandler et al. (2007) Nature 447, 303-306.

Cherniak, D. J.

2007-12-01

132

Determination of the Lamb-Mössbauer factors of LiFePO4 and FePO4 for electrochemical in situ and operando measurements in Li-ion batteries  

NASA Astrophysics Data System (ADS)

57Fe Mössbauer spectroscopy is a powerful tool to investigate redox reactions during in electrochemical lithium insertion/extraction processes. Electrochemical oxidation of LiFeIIPO4 (triphylite) in Li-ion batteries results in FeIIIPO4 (heterosite). LiFePO4 was synthesized by solid state reaction at 800 °C under Ar flow from Li2CO3, FeC2O4·2H2O and NH4H2PO4 precursors in stoichiometric composition. FePO4 was prepared from chemical oxidation of LiFePO4 using bromine as oxidative agent. For both materials a complete 57Fe Mössbauer study as a function of the temperature has been carried out. The Debye temperatures are found to be ?M=336 K for LiFePO4 and ?M=359 K for FePO4, leading to Lamb-Mössbauer factors f300 K=0.73 and 0.77, respectively. These data will be useful for a precise estimation of the relative amounts of each species in a mixture.

Aldon, L.; Perea, A.; Womes, M.; Ionica-Bousquet, C. M.; Jumas, J.-C.

2010-01-01

133

Solvothermal Synthesis of Monodisperse LiFePO4 Micro Hollow Spheres as High Performance Cathode Material for Lithium Ion Batteries.  

PubMed

A microspherical, hollow LiFePO4 (LFP) cathode material with polycrystal structure was simply synthesized by a solvothermal method using spherical Li3PO4 as the self-sacrificed template and FeCl2·4H2O as the Fe(2+) source. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the LFP micro hollow spheres have a quite uniform size of ?1 ?m consisting of aggregated nanoparticles. The influences of solvent and Fe(2+) source on the phase and morphology of the final product were chiefly investigated, and a direct ion exchange reaction between spherical Li3PO4 templates and Fe(2+) ions was firstly proposed on the basis of the X-ray powder diffraction (XRD) transformation of the products. The LFP nanoparticles in the micro hollow spheres could finely coat a uniform carbon layer ?3.5 nm by a glucose solution impregnating-drying-sintering process. The electrochemical measurements show that the carbon coated LFP materials could exhibit high charge-discharge capacities of 158, 144, 125, 101, and even 72 mAh g(-1) at 0.1, 1, 5, 20, and 50 C, respectively. It could also maintain 80% of the initial discharge capacity after cycling for 2000 times at 20 C. PMID:23981067

Yang, Shiliu; Hu, Mingjun; Xi, Liujiang; Ma, Ruguang; Dong, Yucheng; Chung, C Y

2013-09-12

134

Li Diffusion in Olivine  

NASA Astrophysics Data System (ADS)

We have carried out experiments to study the diffusion of Li along the [001] direction of oriented, polished single crystals of San Carlos olivine at 800 °C and atmospheric pressure under a controlled fO2 of 10- 17 bars (~ WM buffer). Cubes of the crystals were annealed surrounded by a powder mix of the same olivine and 6Li enriched lithium silicate. After the experiments, the crystals were sectioned parallel to the diffusion direction and concentration profiles were measured using a Cameca IMS4f ion microprobe in the step scanning mode. The concentration profiles show (i) complex shapes with plateaus in between that are not amenable to treatment using standard solutions to the diffusion equation, and (ii) isotopic fractionation. The shapes of the profiles clearly indicate that at least two different species of Li are involved in the diffusion process. However, a time series of anneals (10 min, 5 h, 10 h, 40 h and 100 h) demonstrate that the shapes are reproducible and evolve systematically with time. We find that the concentration evolution can be described by the following set of processes: (i) incorporation of Li in olivine primarily in octahedral metal sites, (ii) a fast, homogeneous reaction involving metal vacancies (V''Me) that partitions Li between the octahedral site (Li'Me) and interstitial positions (Li\\bulleti): Li'Me = V''Me + Li\\bulleti, and (iii) diffusion of total Li as Li'Me as well as Li\\bulleti, at very different rates. The concentration of Li'Me is at least 10 times higher than the concentration of Li\\bulleti but the diffusion rate of Li\\bulleti is about two orders of magnitude faster than of Li'Me. At the experimental conditions, we can fit the profiles using known values of metal vacancy diffusion coefficients in olivine D(V''Me) = 10-14 m2/s, D(Li'Me) = 10-15 m2/s and D(Li\\bulleti) = 2.5 · 10-13 m2/s. Once these parameters are obtained by fitting any one profile, calculated profiles for any other run duration are an excellent fit to the observed profile shapes, confirming the inferred mechanism. Experiments are in progress to study the temperature dependence of these processes.

Dohmen, R.; Kasemann, S.; Coogan, L.; Chakraborty, S.

2007-12-01

135

Kimberlite Ascent: Insights from Olivine  

NASA Astrophysics Data System (ADS)

Olivine is ubiquitous in both extrusive and intrusive kimberlite deposits worldwide. Within kimberlite, it is mainly present as xenocrysts derived from the disaggregation of mantle-derived peridotitic xenoliths. Many textural and chemical features within the mantle-derived olivine xenocrysts result from post entrainment processes. On that basis, these features record physical and chemical changes attending kimberlite ascent and can be used to elucidate the transport and eruption of kimberlite magma. Our textural study of kimberlitic olivine is based on intrusive and pyroclastic kimberlite from the Diavik kimberlite cluster and from the Igwisi Hills kimberlitic lava flows. Based on these observations and the physical and chemical properties of olivine we derive a relative sequence of textural events. Textural features include: sealed cracks, healed cracks, phases trapping in cracks, rounded grains, overgrowths and phase trapping in overgrowths. These features record processes that operate in kimberlite during ascent, and from these features we create a summary model for kimberlite ascent: -- Olivine is incorporated into kimberlitic melts in peridotitic mantle xenoliths continuously during ascent. Xenolith incorporation is focused at the crack tip where the stress regime is highest. -- Shortly after the incorporation of these xenocrysts the tensile strength of the xenoliths is reached at a maximum of 2 km from its source. Disaggregation of mantle xenoliths (producing xenocrysts) is facilitated by expansion of the minerals within the xenoliths causing intra-crystal slip (i.e. along grain boundaries). -- Continued decompression causes olivine to also break in tension approximately 20 km from source. The void space produced by the failure of the crystals (inter-crystal cracks) is filled with melt and crystals consisting of primary carbonate (high-Sr), chromite and spinel crystals. The carbonate later crystallizes to produce sealed fractures. -- Mechanical rounding of the xenocrysts occurs during pressure release (ascent) events characterized by phase separated (fluid at top: liquid at bottom) flow. Turbulent and fluidized flow heads the propagation whereas kimberlite melt state follows. -- Settling of olivine crystals into the melt state occurs when crack propagation halts. At these points, cracks that are not totally sealed begin to heal, and are ultimately present as healed fractures in olivine in the end deposit. -- Saturation of olivine produces rounded overgrowths on large xenocrysts, euhedral overgrowths on smaller xenocrysts, and a volumetrically minor population of olivine phenocrysts. Olivine growth traps fluid, solid and melt inclusions. Calculations based on these relationships suggest that the melt saturates with olivine at a maximum depth of 20 km and a minimum depth of 7 km.

Brett, C.; Russell, K.

2009-05-01

136

Formation conditions of pyroxene-olivine and magnesian olivine chondrules  

SciTech Connect

Dynamic crystallization experiments performed on a Type I and an intermediate Type II/III composition demonstrate chondrule texture is controlled by the abundance of heterogeneous nuclei. This factor is controlled by the maximum initial temperature relative to the olivine disappearance temperature for the given heating time. Glassy and excentroradial textures form from superheated melts with no nuclei, and barred textures form with initial temperatures near the olivine disappearance temperature. Porphyritic and granular textures form with initial temperatures below the liquidus with abundant nuclei. Comparison of zoning characteristics of experimental olivines with those in natural porphyritic olivine chondrules indicates cooling rates of 100 to 1000{degree}C/h, whereas olivine morphology indicates barred olivines cooled at rates of 250 to 1,000{degree}C/h. Texture/composition relationships suggest chondrules experienced initial temperatures below 1,750{degree}C. These observations are consistent with the idea that chondrules formed by transient heating in dust-rich regions (i.e., in the midplane) of the solar nebula.

Radomsky, P.M.; Hewins, R.H. (Rutgers Univ., New Brunswick, NJ (USA))

1990-12-01

137

Structural, magnetic, and energetic properties of Na2FePO4F, Li2FePO4F, NaFePO4F, and LiFePO4F from ab initio calculations  

NASA Astrophysics Data System (ADS)

In this paper, we report on Na2FePO4F and Li2FePO4F, which are materials that are used as cathodes in batteries, using density functional theory with the LDA, LDA+U, GGA, or GGA+U approximations. Specifically, we study their crystal structure, electronic structure, and magnetic properties and provide similar information about the intermediate compounds LiFePO4F and NaFePO4F. Finally, the intercalation voltages of the corresponding batteries are calculated using various exchange-correlation approximations and conclusions are drawn about which one is the most suitable to use for the study of this class of materials.

Ramzan, M.; Lebègue, S.; Larsson, P.; Ahuja, R.

2009-08-01

138

Defects in Microwave Solvothermally Grown Phospho-Olivine Nanoparticles  

SciTech Connect

Microwave solvothermally (MW-ST) synthesized crystalline nanopowders of LiFePO4 have been structurally characterized using a combination of high resolution powder neutron diffraction, synchrotron X-ray diffraction and HAADF STEM images. The presence of a significant level of defects has been verified for the samples prepared at 255 oC and 275 oC. These temperatures are significantly higher than what has previously been suggested to be the maximum temperature for defect formation in LiFePO4, and their presence likely relates to the rapid synthesis provided by the MW-ST approach. A defect model has been tentatively proposed, though it has been shown that powder diffraction data alone cannot conclusively determine the precise defect distribution in LiFePO4 samples. The model is consistent with other literature reports on nanopowders synthesized at low temperatures, in which the unit cell volume is significantly reduced relative to defect-free, micron-sized LiFePO4 powders.

Bridges, Craig A [ORNL; Harrison, Katharine L [University of Texas at Austin; Unocic, Raymond R [ORNL; Idrobo Tapia, Juan C [ORNL; Paranthaman, Mariappan Parans [ORNL; Manthiram, Arumugam [University of Texas at Austin

2013-01-01

139

Supernova olivine from cometary dust.  

PubMed

An interplanetary dust particle contains a submicrometer crystalline silicate aggregate of probable supernova origin. The grain has a pronounced enrichment in 18O/16O (13 times the solar value) and depletions in 17O/16O (one-third solar) and 29Si/28Si (<0.8 times solar), indicative of formation from a type II supernova. The aggregate contains olivine (forsterite 83) grains <100 nanometers in size, with microstructures that are consistent with minimal thermal alteration. This unusually iron-rich olivine grain could have formed by equilibrium condensation from cooling supernova ejecta if several different nucleosynthetic zones mixed in the proper proportions. The supernova grain is also partially encased in nitrogen-15-rich organic matter that likely formed in a presolar cold molecular cloud. PMID:15994379

Messenger, Scott; Keller, Lindsay P; Lauretta, Dante S

2005-06-30

140

Water-Induced Fabric Transitions in Olivine  

Microsoft Academic Search

The interpretation of seismic anisotropy in Earth's upper mantle has traditionally been based on the fabrics (lattice-preferred orientation) of relatively water-poor olivine. Here we show that when a large amount of water is added to olivine, the relation between flow geometry and seismic anisotropy undergoes marked changes. Some of the puzzling observations of seismic anisotropy in the upper mantle, including

Haemyeong Jung; Shun-ichiro Karato

2001-01-01

141

Dissolution of olivine during natural weathering  

NASA Astrophysics Data System (ADS)

Naturally weathered olivine occurring as phenocrysts in Hawai'ian volcanic rocks from several volcanic centers and regolith/outcrop settings, and as tectonized olivines from several metadunite bodies in the southern Appalachian Blue Ridge, are all similarly corroded by natural weathering. Conical (funnel-shaped) etch pits occur as individual pits, base-to-base pairs of cone-shaped pits, or en echelon arrays. Etch-pit shapes and orientations in the smallest etch-pit arrays visible in conventional scanning electron microscopy resemble even smaller features previously reported from transmission electron microscope investigations of olivine weathering. Etch pits occur in samples with chemical and/or mineralogical evidence of weathering, and/or are associated with, or proximal or directly connected to, fractures or exposed outcrop surface, and therefore are formed by weathering and not inherited from pre-weathering aqueous alteration (e.g., serpentinization, iddingsitization) of these parent rocks. Many etch pits are devoid of weathering products. Natural weathering of olivine is surface-reaction-limited. Similarity of corrosion forms from naturally weathered olivine from multiple igneous and metamorphic parent-rock bodies suggests that olivine weathers in the same manner regardless of its specific crystallization/recrystallization history, eruption/weathering/exposure ages of the olivine's host rock, and the local regolith history.

Velbel, Michael A.

2009-10-01

142

Primary trapped melt inclusions in olivine in the olivine-augite-orthopyroxene ureilite Hughes 009  

Microsoft Academic Search

We describe the first known occurrence of primary melt inclusions in a ureilite. The ureilite is Hughes 009, one of a small number of ureilites whose primary mineralogy is olivine-augite-orthopyroxene, rather than olivine-pigeonite. Hughes 009 has a coarse-grained, equilibrated texture typical of ureilites, and homogeneous primary mineral compositions: olivine — mg 87.3; augite — mg 89.2, Wo 37.0, Al2O3 =

Cyrena Anne Goodrich; Anna Maria Fioretti; Mario Tribaudino; Gianmario Molin

2001-01-01

143

Water in Olivine - not a Simple Question  

NASA Astrophysics Data System (ADS)

How much "water" is present in olivine is of great interest for the upper mantle. Thermodynamics mandates that small amounts of H2O become structurally incorporated, when olivine crystallizes in an H2O-laden environment. It is widely believed that the formation of hydroxyl (OH- or Si-OH) is the end point of the H2O dissolution mechanism. Therefore it is also believed that quantitative solute H2O contents can be obtained by measuring the O-H stretching bands in olivine crystals by infrared (IR) spectroscopy. However, we can take olivine crystals, which are devoid of OH- according to the IR criteria, and fracture them in front of a mass spectrometer. Instantly upon fracture, H2 molecules evolve from the freshly formed surfaces, followed by H2O and then again by H2. This observation indicates that an apparently "dry" olivine can contain dissolved H2O, though not in form of IR-recognizable OH- or Si-OH. When we measure the effective dielectric constant \\epsiloneff at the limit of 0 Hz, we observe that \\epsiloneff changes reversibly in two steps, around 200°C and 400°C. At about 400°C the olivine turns into a p-type semiconductor. Our observations point (i) at the conversion of hydroxyl, probably Si-OH pairs, into H2 plus peroxy links, Si-OO-Si, (ii) at a two-step dissociation of the peroxy links. We conclude that, to determine the amount of solute "water" in olivine, it is not enough to measure its hydroxyl content by IR spectroscopy. Other methods have to be used or developed to provide information about the number of H2 molecules and peroxy links in the olivine matrix.

Bansal, S. A.; Dickinson, J. T.; Freund, F.

2004-12-01

144

Incompatible Trace Element Abundances in Hawaiian Olivines  

NASA Astrophysics Data System (ADS)

Our understanding of trace elements partitioning between olivine and silicate melt is clouded by large variations in values of partition coefficients presented in the literature. In general, partition coefficients from phenocryst-matrix results are higher than those from experimental equilibration and in-situ measurements (such as LA-ICP-MS and Ion-probe) (Blard and Farley, 2008; Lee et al., 2007). This discrepancy is possibly caused by the presence of melt or micromineral inclusions in the analyzed phenocrysts, or contamination of grain boundaries by enriched glasses or accessory phases or uranium pick up from alteration of olivines. To further investigate why analysis of natural phenocrysts usually results in relative high apparent D’s for incompatible trace elements, six aliquots of olivine grains from a single sediment sample of Waimea river watershed, on the western side of the island of Kauai, Hawaii, were analyzed by solution ICP-MS at Harvard University for trace element concentrations. Two aliquots of olivines were leached in 1% oxalic acid for 45-60 min at 90 OC before dissolution. Leached and unleached olivines mostly show positive linear correlations in plots of incompatible trace elements versus La, which possibly indicates mixing lines between olivine and one end-member with higher incompatible element concentration (possibly melt inclusion). Assuming La concentration in olivine is zero, we estimate concentration of other incompatible elements in olivines using intercepts of these mixing lines. We obtain that U and Th concentration in the olivines to be about 1 ppb and 0.1 ppb respectively, corresponding to apparent DUol/melt and DThol/melt of 0.003 and 0.0001 if host lave has U of 0.3 ppm and Th of 1ppm (Gayer et al.,2008). Recently, helium isotopic measurements were made in these olivines (Gayer et al., 2008) and the results yield a basin-wide average erosion rate of 0.056 mma-1 for Waimea river watershed. Gayer et al. (2008) argued that radiogenic 4He in these ~4.5 Ma old olivines is negligible using DUol/melt=2×10-5 and DThol/melt=5×10-5 (Beattie 1993; Kennedy et al., 1993) and 0.3 ppm U and 1 ppm Th for host lavas. This assumption has been challenged by Blard and Farley (2008), who argued that radiogenic 4He in these olivines are significant and could affect the calculated erosion rate by a factor of 10-100. They used apparent DUol/melt and DThol/melt ranging between 0.03 and 0.1, which were obtained from analyses of whole natural phenocrysts and host lava (Blard and Farley, 2008). In contrast, using our measured U and Th contents in the Kauai olivines suggest revisions to erosion rates on order of only 15%. Therefore, Blard and Farley (2008)’s apparent D values may not be representative of Kauai olivines and their assertion that Gayer et al. (2008)’s erosion rates from Hawaii require revision by more than a factore of 10 is incorrect.

Yu, G.; Huang, S.; Mukhopadhyay, S.; Jacobsen, S. B.

2009-12-01

145

Atom Probe Tomography of Olivine  

NASA Astrophysics Data System (ADS)

Here we present atom probe tomographic (APT) analyses of natural olivine. APT provides three-dimensional trace element and isotopic analysis with sub-nanometer spatial resolution. It has been used for many years in engineering and materials science, but has not been applied to geological materials because traditional APT can only be used on conducting (usually metal) samples. The recent development of laser assisted APT has changed this situation, and now semi-conductors and insulators can be analyzed (Marquis et al., 2009, Kelly et al 2007). Potentially, this opens APT to extensive use in geoscience as many Fe-bearing silicates are semi-conductors. In this study, we explore the capability of the new class of APT instrumentation to analyze geological materials. APT involves the controlled evaporation of small, cylindrical specimens (100's nm in diameter) within an electric field. Specimens are typically prepared using in-situ focused-ion-beam (FIB) liftout and shaping techniques. Evaporated atoms are accelerated to a detector plate that records the position of the atom with sub-nm precision. Evaporated atoms are measured using time-of-flight mass spectrometry, allowing both elemental and isotopic determination. Since the method progressively ablates into the needle, the final analytical result is a nm-scale 3-dimensional image in which the position and identity of each detected atom is known. Typical mass resolution is between 200 and 1200 (full-width at half maximum) and typical concentration detection limits are 10 ppm. The number of potential applications of APT to igneous, metamorphic and sedimentary materials is large, ranging from studies of mineral and melt inclusions, to fine scale layering in minerals, to reaction surfaces and diffusion profiles. Much recent progress in the geochemical and petrologic fields has been driven by the increasing spatial resolution of the ion probe and laser ablation ICPMS. The ability of APT to provide atom-scale mass spectrometry should continue this trend. The main limitations to atom probe analysis of geological materials are the ability to control heat flow during laser pulsing and the associated ability to control clustering during field evaporation. Both of these factors can be controlled through specimen preparation and varying the atom probe experimental factors. Olivine specimens were properly analyzed using laser pulsed APT through the use of shallow (nominally 1mm) FIB liftouts and wide shank angle specimen apices. APT settings were found to give the best mass resolution using low specimen temperatures, 0.2 nJ laser energy, and 50 kHz pulse repetition rate. Increasing any of these values increases the amount of thermal tails due to excessive heat buildup, reducing the mass spectrum resolution, and ultimately affecting the spatial resolution of the reconstruction. Marquis EA, Miller MK, Blavette D, Ringer SP, Sudbrack CK and Smith DW (2009). MRS Bulletin 34: 725-730. Thomas F. Kelly, David J. Larson, Keith Thompson, Roger L. Alvis, Joseph H. Bunton, Jesse D. Olson, Brian P. Gorman, Ann. Rev. Mat. Res. 37: 681-727.

Parman, S. W.; Gorman, B.; Jackson, C.; Cooper, R. F.; Jaeger, D.

2010-12-01

146

Defect chemistry of phospho-olivine nanoparticles synthesized by a microwave-assisted solvothermal process  

NASA Astrophysics Data System (ADS)

Nanocrystalline LiFePO4 powders synthesized by a microwave-assisted solvothermal (MW-ST) process have been structurally characterized with a combination of high resolution powder neutron diffraction, synchrotron X-ray diffraction, and aberration-corrected HAADF STEM imaging. A significant level of defects has been found in the samples prepared at 255 and 275 °C. These temperatures are significantly higher than what has previously been suggested to be the maximum temperature for defect formation in LiFePO4, so the presence of defects is likely related to the rapid MW-ST synthesis involving a short reaction time (˜5 min). A defect model has been tentatively proposed, though it has been shown that powder diffraction data alone cannot conclusively determine the precise defect distribution in LiFePO4 samples. The model is consistent with other literature reports on nanopowders synthesized at low temperatures, in which the unit cell volume is significantly reduced relative to defect-free, micron-sized LiFePO4 powders.

Bridges, Craig A.; Harrison, Katharine L.; Unocic, Raymond R.; Idrobo, Juan-Carlos; Parans Paranthaman, M.; Manthiram, Arumugam

2013-09-01

147

A search for olivine activation volume  

NASA Astrophysics Data System (ADS)

Knowledge of the rheological properties of mantle materials is critical in modeling the dynamics of the Earth. The flow law of olivine defined at mantle pressure and temperature is especially important since the pressure dependence of rheology may affect our estimation for the strength of olivine in the Earth's interior. Conventional deformation methods in defining the flow law of olivine have to face factors of large uncertainties of differential stress measurements and/or limited confining pressure for deformation. In this study, high-temperature (up to 1473 K) deformation experiments of polycrystalline olivine (average grain size < 5 micron) at pressure up to 6.5(0.2) GPa were conducted in-situ using large-volume high-pressure apparatus (Deformation DIA) and synchrotron x-ray radiation. More than 30% strain was generated during the uniaxial compression. The sample lengths during the deformation process were monitored by x-ray radiography. The strain rate was derived with precision up to 10-6. Macroscopic differential stress was measured at constant strain rate (˜ 10-5 s-1) using a multi-element solid-state detector combined with a conical slit. The new data, measured at 1473 and 1273K at 6.5 and 3GPa, fits well an empirical power-law creep flow law under the condition that the activation energy is 520(20) kJ/mol and the activation volume is less than 3 cm^3/mol. Consistent with TEM observations on recovered samples, tests for grain size dependence of flow, and the empirical power law exponent, we conclude that power-law creep is the dominant flow mechanism for dry olivine at upper mantle conditions. The success of defining the flow law for olivine in this study also symbolizes a huge opening for defining the rheological flow law for other materials in the Earth's interior.

Li, L.; Weidner, D.; Mei, S.; Raterron, P.; Chen, J.; Durham, W.

2003-04-01

148

OH point defects in olivine from Pakistan  

NASA Astrophysics Data System (ADS)

The infrared (IR) spectra of gem-quality olivine crystals from Pakistan, formed in serpentinised dunitic rocks, are characterised by strongly pleochroic absorption bands at 3,613, 3,597, 3,580 and 3,566 cm-1. These bands are assigned to O-H stretching vibrations of OH point defects corresponding to H2O concentrations of about 35 wt ppm. Unlike other olivine spectra, the dominating bands are strongly polarised parallel to the b-axis. The unusual spectra type, excludes the presence of planar defects. This finding is supported by transmission electron microscopy. The 3,613 cm-1 band is related to vacant Si sites, the slightly lower energetic bands preferentially to vacant M2 sites. The exclusive presence of these bands is not only a characteristic feature of olivines treated under high P,T conditions equivalent to mantle environment, the presence of these bands in untreated natural olivine also indicates formation conditions equivalent to crustal rocks.

Gose, Jürgen; Schmädicke, Esther; Markowitz, Margit; Beran, Anton

2010-05-01

149

Cations in olivine, Part 1: Calcium partitioning and calcium-magnesium distribution between olivines and coexisting melts, with petrologic applications  

Microsoft Academic Search

As part of a study of kinetic and equilibrium aspects of magmatic olivines (Jurewicz 1986; Jurewicz and Watson 1988), calcium distribution and partitioning sys- tematics have been experimentally determined for olivine\\/ melt pairs under a wide variety of temperatures, pressures and oxygen fugacities. The calcium content of an equilibrated olivine depends upon (1) the concentration of calcium in the melt

Amy J. G. Jurewicz; E. Bruce Watson

1988-01-01

150

Water loss from olivine hosted melt inclusions  

NASA Astrophysics Data System (ADS)

Water content in melt inclusions has long been used as an important index for the water content of the hosting magma. However, many studies have shown that post-entrapment diffusive re-equilibration can affect the water content of melt inclusions. This process must be considered when using melt inclusions to infer water content of the hosting magma. Theoretical model on the diffusive re-equilibration between melt inclusions and external melts showed that the re-equilibration rate depends on the diffusivity of the re-equilibrating species in the host mineral, the partition coefficient of this species between the host mineral and melt, and the geometry of the melt inclusion and host mineral. The water diffusivity in olivine and water partition coefficient between melt and olivine have been measured by recent studies, therefore the diffusive re-equilibration model can be tested by experiments. In this study, we carried out in-situ Fourier transform infrared spectroscopy (FTIR) measurements on the water content of olivine hosted melt inclusions at high temperatures. Initial water content of the melt inclusions is about 4 wt%. A heating stage system is combined with a microscope FTIR and the absorption spectrum through the olivine and melt inclusion is repeatedly measured. Although the absorption band at around 3540 cm-1 has not be calibrated at high temperatures, it is assumed that the absorbance is linearly related to the total water concentration in the melt inclusion, and the relative water content can be inferred. Cautions have been exercised to maintain a consistent measurement spot such that the thickness of the melt inclusion within the beam path did not change significantly during each experiment. Oxygen fugacity in the heating stage is controlled by Zr purified Ar gas to be about 7 logarithm units below the QFM buffer and about 1 logarithm unit above the QIF buffer at 1473 K. Preliminary results showed that at 1430 and 1581 K, the total water content of the melt inclusion decreased by 80% within about 7 and 1 hours, respectively. This rapid decrease of water content agrees with previous observations. Applying the model and water partition coefficient between olivine and melt by a previous study yields water diffusivities in olivine as 5E-12 and 3E-11 m2/s at 1430 and 1581 K, respectively. These numbers are consistent with the diffusivities measured by a previous study. Due to some experimental difficulties, it is unclear whether bubble existed during the experiments and affected the apparent water content change. Oxygen fugacity may also play a role in water re-equilibration. Further efforts will be made to investigate these aspects and better understand the water re-equilibration process.

Chen, Y.; Provost, A.; Schiano, P.; Cluzel, N.

2009-12-01

151

Electronically conductive phospho-olivines as lithium storage electrodes  

NASA Astrophysics Data System (ADS)

Lithium transition metal phosphates have become of great interest as storage cathodes for rechargeable lithium batteries because of their high energy density, low raw materials cost, environmental friendliness and safety. Their key limitation has been extremely low electronic conductivity, until now believed to be intrinsic to this family of compounds. Here we show that controlled cation non-stoichiometry combined with solid-solution doping by metals supervalent to Li+ increases the electronic conductivity of LiFePO4 by a factor of ~108. The resulting materials show near-theoretical energy density at low charge/discharge rates, and retain significant capacity with little polarization at rates as high as 6,000 mA g-1. In a conventional cell design, they may allow development of lithium batteries with the highest power density yet.

Chung, Sung-Yoon; Bloking, Jason T.; Chiang, Yet-Ming

2002-10-01

152

Electronic Properties of LiFePO4 and Li doped LiFePO4  

SciTech Connect

LiFePO{sub 4} has several potential advantages in comparison to the transition metal oxide cathode materials used in commercial lithium-ion batteries. However, its low intrinsic electronic conductivity ({approx} 10{sup -9} S/cm) is problematic. We report here a study by soft x-ray absorption/emission spectroscopy of the electronic properties of undoped LiFePO{sub 4} and Li-doped LiFePO{sub 4} in which Li{sup +} ions are substituted for Fe{sup 2+} ions in an attempt to increase the intrinsic electronic conductivity. The conductivities of the Li{sub 1+x}Fe{sub 1-x}PO{sub 4} samples were, however, essentially unchanged from that of the undoped LiFePO{sub 4}. Nonetheless, evidence for changing the electronic properties of LiFePO{sub 4} by doping with excess Li+ was observed by the XAS/XES spectroscopy. New pre-edge features the O-1s XAS spectrum of Li{sub 1.05}Fe{sub 0.95}PO4 is a direct indication that the charge compensation for substitution of Fe{sup 2+} by Li{sup +} resides in the unoccupied O-2p orbitals. A charge transfer (CT) excitation was also observed in the doped material implying that the unoccupied O-2p orbitals created by doping are strongly hybridized with unoccupied Fe-3d orbitals of neighboring sites. However, the strong covalent bonding within the (PO{sub 4}){sup 3-} anions and the large separation of the Fe cations means that the charge created by doping is not delocalized in the manner of electrons or holes in a semiconductor.

Allen, J.L.; Zhuang, G.V.; Ross, P.N.; Guo, J.-H.; Jow, T.R.

2006-05-31

153

Shock-produced olivine glass: First observation  

USGS Publications Warehouse

Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, (Mg0.88Fe 0.12SiO4 recovered from peak pressures of about 56 ?? 109 pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation ofolivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that olivine glass may be formed as a result of shock at pressures above about 50 to 55 ?? 109 pascals and that further TEM observations of naturally shocked olivines may demonstrate the presence of glass.

Jeanloz, R.; Ahrens, T. J.; Lally, J. S.; Nord, Jr. , G. L.; Christie, J. M.; Heuer, A. H.

1977-01-01

154

Olivine-rich patches observed by OMEGA  

NASA Astrophysics Data System (ADS)

Several small regions with very intense and broad 1 ?m absorption have been observed by OMEGA. They are mostly located in the dark, older highland plateaus of the southern hemisphere, in particular Terra Tyrrhena and Noachis Terra. The band starts at 0.9 ?m, presents a steep absorption front located up to 1.6 ?m, 20% in strengh, and is accompanied in some cases by a subdued feature at ~0.5 ?m. Such broad signatures, when they appear alone, are matched only by olivines with high Fe content (fayalite endmember). The observed patches are typically on the kilometer scale, and are located in otherwise pyroxene-rich areas. In at least one occurrence, an enhanced olivine feature is located in the rim and ejecta blanket of a crater, suggesting excavated material. Some of them could correspond to areas tentatively detected by TES (Hoefen & Clark 2001).

Erard, S.; Langevin, Y.; Forni, O.; Poulet, F.; Bibring, J.-P.

155

Dislocation creep of fine-grained olivine  

Microsoft Academic Search

Deformation experiments conducted in a gas medium apparatus at temperatures from 1200 to 1350°C with a fine-grained, solution-gelation derived Fe-bearing olivine show a stress dependence of the strain rate at stresses above ?150 MPa, which is much stronger than previously reported for polycrystalline samples. The data can be fit by a power law with $\\\\dot {\\\\epsilon }$$\\\\propto$?n with n ?

U. H. Faul; J. D. Fitz Gerald; R. J. M. Farla; R. Ahlefeldt; I. Jackson

2011-01-01

156

Dynamic crystallization study of barred olivine chondrules  

SciTech Connect

Chondrules, which comprise the bulk of most chondrites, formed very early in the solar system, and understanding their formation will elucidate early nebular processes. Barred olivine (BO) chondrules make up approximately 10% of chondrules and because of their unique dendritic textures represent a restricted set of crystal growth conditions and, thus, formation conditions. BO textures have been replicated using dynamic crystallization techniques on olivine-rich chondrule starting compositions in an attempt to determine these formation conditions. One composition was modeled after the average BO chondrule composition in L-chondrites determined by Weisberg (1987) in a survey of BO chondrules. Chondrule droplets are presumed to form by the melting of crystalline material. BO textures developed best if the crystalline precursor was melted slightly above to tens of degrees above the liquidus temperature eliminating all ready nuclei. Crystalline material (embryos) of subcritical nuclei size in the melts provide the nuclei when they reach critical nucleus size at degrees of supercooling which stabilize the plate dendritic crystal form of olivine. The plate dendrite is the basic crystal unit of the BO texture. Multiple-plate dendrites are the common texture in experimentally produced chondrules; the classic, single-plate-dendrite BO chondrule has not been reproduced in the experiments.

Lofgren, G. (NASA Johnson Space Center, Houston, TX (USA)); Lanier, A.B. (Lockheed Engineering and Science Company, Houston, TX (USA))

1990-12-01

157

Electrical conductivity of synthetic iron-bearing olivine  

Microsoft Academic Search

The electrical conduction in synthetic, dry polycrystalline, iron-bearing olivine (Fo90) was investigated as a first-order approach to the electrical conductivity in the upper mantle. This fundamental study is\\u000a of great importance to better understand the charge-transport mechanisms seen in olivine. Conduction processes in synthetic\\u000a samples are not influenced by a complex geological history in contrast to conductivity in natural olivine.

Robert J. M. Farla; C. J. Peach; S. M. ten Grotenhuis

2010-01-01

158

Search for olivine spectral signatures on the surface of Vesta  

NASA Astrophysics Data System (ADS)

The occurrence of olivines on Vesta were first postulated from traditional petrogenetic models which suggest the formation of olivine as lower crustal cumulates. An indirect confirmation is given by their presence as a minor component in some samples of diogenite meteorites, the harzburgitic diogenites and the dunitic diogenites, and as olivine mineral clasts in howardites. Another indication for this mineral was given by interpretations of ground-based and Hubble Space Telescope observations that suggested the presence of local olivine-bearing units on the surface of Vesta. The VIR instrument onboard the DAWN mission has been mapping Vesta since July 2011. VIR acquired hyperspectral images of Vesta's surface in the wavelength range from 0.25 to 5.1 µm during Approach, Survey and High Altitude Mapping (HAMO) orbits that allowed a 2/3 of the entire asteroid surface to be mapped. The VIR operative spectral interval, resolution and coverage is suitable for the detection and mapping of any olivine rich regions that may occur on the Vesta surface. The abundance of olivine in diogenites is typically lower than 10% but some samples richer in olivine are known. However, we do not expect to have extensive exposures of olivine-rich material on Vesta. Moreover, the partial overlap of olivine and pyroxene spectral signatures will make olivine difficult to detect. Different spectral parameters have been used to map olivine on extraterrestrial bodies, and here we discuss the different approaches used, and develop new ones specifically for Vesta. Our new methods are based on combinations of the spectral parameters relative to the 1 and 2 micron bands (the most prominent spectral features of Vesta surface in the visible and the infrared), such as band center locations, band depths, band areas, band area ratios. Before the direct application to the VIR data, the efficiency of each approach is evaluated by means of analysis of laboratory spectra of HED meteorites, pyroxenes, olivines and their mixtures.

Palomba, E.; De Sanctis, M. C.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Farina, M.; Frigeri, A.; Longobardo, A.; Tosi, F.; Zambon, F.; McSween, H. Y.; Mittlefehldt, D. W.; Russell, C. T.; Raymond, C. A.; Sunshine, J.; McCord, T. B.

2012-04-01

159

Olivine-based heat storage refractories  

NASA Astrophysics Data System (ADS)

The processing properties and performance of special refractory shapes produced from olivine for prototype evaluations in heat storage furnaces are investigated. Heat storage furnaces and related consumer owned thermal storage units are energy conversion/storage devices of the sensible heat type. Their primary purpose is to permit electrical load leveling of large generating/distributing systems. Load-leveling enables power generating plants to operate more efficiency thus contributing to better overall energy utilization. The principal application for these ceramic thermal energy reservoirs is in home or business heating (furnaces, space heaters).

Gay, B. M.; Palmour, H., III; Cochrane, R. L.

1981-03-01

160

Effect of Water on Olivine Metastability in Subducting Lithosphere  

NASA Astrophysics Data System (ADS)

The roles of metastably persisting olivine in subducting lithosphere has been investigated in light of mineralogical and thermal structures, plate velocities, and deep seismogenesis. Many different variables have been used in these examinations: latent heat feedback, kinetic models, and thermal conductivity models, to name a few. In all these models, however, the olivine has been anhydrous, though the presence of H2O in the (Mg,Fe)2SiO4 system is well-known to enhance the rates of phase transformation. Diedrich et al. [2005] recently determined growth rates for olivine with low (300 wt ppm) water content and found that, compared with dry samples, hydrous olivine has growth rates 1.7 orders faster at 1100°C. Using these kinetic data, we modeled 25 subducting slabs with thermal parameters (?) ranging from 3400-17000 km to see the effect of water on olivine metastability. Except within the coldest, fastest slabs, (? > 10000 km) all olivine had transformed to wadsleyite or ringwoodite within 1-2 km of the equilibrium phase boundary, resulting in regions of metastability only 5-10% in size as compared with slabs with dry olivine. Wedges of metastable olivine did form in slabs moving at velocities ?14 cm/yr, yet these were only 4-5% in size with respect to their anhydrous counterparts. Metastable olivine only reached maximum depths of ~360 km, compared with 500-550 km for dry slabs, 5-15 km down-dip of the equilibrium phase boundary. These results suggest that, given small amounts of water, subducting slabs will exhibit near-equilibrium mineralogical structures. Therefore, in consequence, explanations of deep seismogenesis that rely on the persistence of metastable olivine would seem unlikely for hydrous lithosphere. In addition, any decrease in subduction velocity due to the existence of a low-density wedge of metastable olivine (the parachute effect) in dry slabs would not be evident in hydrous ones.

Marton, F. C.; Diedrich, T.; Sharp, T. G.

2006-12-01

161

Olivine Annealing in Molten Iron-Sulfide. A Tool to Interpret the Origin of Pallasites  

NASA Astrophysics Data System (ADS)

Annealing of olivine in molten Fe-S was performed in order to decipher the origin of rounded olivine group pallasite meteorites. Growth mechanism and growth rate of olivine was obtained and a variety of formation models are critically discussed.

Solferino, G. F. D.; Muir, S. L.

2013-09-01

162

Possible Xenolith and Xenocrysts of Olivine in the Asuka-881371 Angrite Collected from Antarctica  

NASA Astrophysics Data System (ADS)

Angrite is the oldest aged rock in all meteorites. Asuka-881371 angrite include some xenolith-xenocrysts like olivine aggragate and/ or large olivine grains. They are differ from any olivine in host for their occurrences, texture and compositions.

Yanai, K.

2003-03-01

163

RELICT Olivines in Micrometeorites from Greenland and Antarctica  

NASA Astrophysics Data System (ADS)

Previously, [1] studied the bulk chemistry and texture of 223 micrometeorites from Greenland (size: 100-200 micrometers): 82% spherical, 6% porous, and 12% monomineralic particles or particles with unique textures and from Antarctica (size: 50-100 micrometers): 24% spheres, 62% porous, and 14% particles with unique textures. In order to obtain information about the origin of micrometeorites we have studied minerals within these particles that escaped melting during atmospheric heating. Relict olivine grains occur in 27 spheres, 3 porous particles, and 11 particles with unique textures. Relict olivines (mostly > 5 micrometers in apparent size) can be distinguished from secondary crystallized (subsequent to atmospheric melting) olivines by their grain size, morphology, composition, and/or the presence of Fe/Ni-metal inclusions in olivine. Previously, [2] studied 26 Mg-rich olivines from Antarctic micrometeorites and [3] investigated about 70 olivines in micrometeorites from Antarctica and Greenland. Within the 41 micrometeorites containing such grains, 98 relict olivines were analyzed by electron microprobe, representing a much wider range of compositions than reported by [2]. In most micrometeorites, only one or two relict olivines occur and were large enough to be analyzed. In some particles, however the Fa-contents of several relict olivines were obtained (Fig. 1). Relict olivines with Fa-contents below 5.2 mol% Fe are abundant (Fig. 1). One forsterite within a porous particle is manganese- enriched and similar in composition to LIME olivines known from IDPs and primitive meteorites [4]. Comparing olivines from chondrites with those in micrometeorites, Fa-poor olivines occur in Type I chondrules from carbonaceous chondrites [5] and as isolated olivines in the matrix of C2, C3, and unequilibrated ordinary chondrites [2]. Between Fa(sub)5.2 and Fa(sub)~12 a gap exists in the distribution of the Fa-contents (Fig. 1). Relict olivines, however, with about 12 and 30 mol% Fa occur. These Fa- contents are similar to those of equilibrated H, L, and LL chondrites and may indicate that many particles are related to ordinary chondrites. In addition, several other micrometeorites contain olivines with Fa-contents exceeding those of olivines in ordinary chondrites. Considering chondrites as potential material of their origin, they may be related to matrix olivines in Type III carbonaceous chondrites and to olivines in Type II chondrules [5]. In six micrometeorites relict olivines with highly variable compositions were analyzed, indicating that the precursor was unequilibrated prior to thermal processing during atmospheric entry. Comparing all data, it appears that the larger-sized particles from Greenland may contain a slightly higher abundance of forsteritic relict olivines than the small particles from Antarctica. However, we cannot rule out that this observation is a result of insufficient data. References: [1] Beckerling W. et al. (1992) Meteoritics, 27, 200- 201. [2] Steele I. M. (1992) GCA, 56, 2923-2929. [3] Christophe Michel-Levy M. and Bourot-Denise M.(1992) Meteoritics, 27, 73-80. [4] Klock W. et al. (1989) Nature, 339, 126-128. [5] McSween H. Y. (1977) GCA, 41, 477-491.

Beckerling, W.; Klock, W.; Bischoff, A.

1993-07-01

164

Fe/Mn in Olivine of Carbonaceous Meteorites.  

National Technical Information Service (NTIS)

Olivines in primitive meteorites show a range of Fe/Mn both within one grain and among grains suggesting that they have recorded changing conditions during or after growth. Because olivine should be an early forming phase, Fe/Mn is used here to infer thes...

I. M. Steele

1993-01-01

165

Effect of Water on Olivine Metastability in Subducting Lithosphere  

Microsoft Academic Search

The roles of metastably persisting olivine in subducting lithosphere has been investigated in light of mineralogical and thermal structures, plate velocities, and deep seismogenesis. Many different variables have been used in these examinations: latent heat feedback, kinetic models, and thermal conductivity models, to name a few. In all these models, however, the olivine has been anhydrous, though the presence of

F. C. Marton; T. Diedrich; T. G. Sharp

2006-01-01

166

Ringwoodite lamellae in olivine: Clues to olivine-ringwoodite phase transition mechanisms in shocked meteorites and subducting slabs  

PubMed Central

The first natural occurrence of ringwoodite lamellae was found in the olivine grains inside and in areas adjacent to the shock veins of a chondritic meteorite, and these lamellae show distinct growth mechanism. Inside the veins where pressure and temperature were higher than elsewhere, ringwoodite lamellae formed parallel to the {101} planes of olivine, whereas outside they lie parallel to the (100) plane of olivine. The lamellae replaced the host olivine from a few percent to complete. Formation of these lamellae relates to a diffusion-controlled growth of ringwoodite along shear-induced planar defects in olivine. The planar defects and ringwoodite lamellae parallel to the {101} planes of olivine should have been produced in higher shear stress and temperature region than that parallel to the (100) plane of olivine. This study suggests that the time duration of high pressure and temperature for the growth of ringwoodite lamellae might have lasted at least for several seconds, and that an intracrystalline transformation mechanism of ringwoodite in olivine could favorably operate in the subducting lithospheric slabs in the deep Earth.

Chen, Ming; Goresy, Ahmed El; Gillet, Philippe

2004-01-01

167

Ringwoodite lamellae in olivine: Clues to olivine-ringwoodite phase transition mechanisms in shocked meteorites and subducting slabs.  

PubMed

The first natural occurrence of ringwoodite lamellae was found in the olivine grains inside and in areas adjacent to the shock veins of a chondritic meteorite, and these lamellae show distinct growth mechanism. Inside the veins where pressure and temperature were higher than elsewhere, ringwoodite lamellae formed parallel to the [101] planes of olivine, whereas outside they lie parallel to the (100) plane of olivine. The lamellae replaced the host olivine from a few percent to complete. Formation of these lamellae relates to a diffusion-controlled growth of ringwoodite along shear-induced planar defects in olivine. The planar defects and ringwoodite lamellae parallel to the [101] planes of olivine should have been produced in higher shear stress and temperature region than that parallel to the (100) plane of olivine. This study suggests that the time duration of high pressure and temperature for the growth of ringwoodite lamellae might have lasted at least for several seconds, and that an intracrystalline transformation mechanism of ringwoodite in olivine could favorably operate in the subducting lithospheric slabs in the deep Earth. PMID:15479764

Chen, Ming; El Goresy, Ahmed; Gillet, Philippe

2004-10-12

168

Cotectic proportions of olivine and spinel in olivine-tholeiitic basalt and evaluation of pre-eruptive processes  

USGS Publications Warehouse

The volume %, distribution, texture and composition of coexisting olivine, Cr-spinel and glass has been determined in quenched lava samples from Hawaii, Iceland and mid-oceanic ridges. The volume ratio of olivine to spinel varies from 60 to 2800 and samples with >0.02% spinel have a volume ratio of olivine to spinel of approximately 100. A plot of wt % MgO vs ppm Cr for natural and experimental basaltic glasses suggests that the general trend of the glasses can be explained by the crystallization of a cotectic ratio of olivine to spinel of about 100. One group of samples has an olivine to spinel ratio of approximately 100, with skeletal olivine phenocrysts and small (100 ??m) spinel crystals that show evidence of two stages of growth, and a volume ratio of olivine to spinel of 100 to well over 1000. The olivine and spinel in this group have crystallized more slowly with little physical interaction, and show evidence that they have accumulated in a magma chamber. ?? 2006 Oxford University Press.

Roeder, P.; Gofton, E.; Thornber, C.

2006-01-01

169

The case for a cognate, polybaric origin for kimberlitic olivines  

NASA Astrophysics Data System (ADS)

Kimberlitic olivines typically show a continuous range in size and texture rather than two discrete populations. The cores of small euhedral olivines commonly provide the template for the final crystal shape, which in turn closely matches morphologies produced by crystallization from a moderately under-cooled magma. Cores and edges of the majority of all olivines define a continuous compositional field, which can be interpreted in terms of Raleigh crystallization. Marked chemical gradients at the olivine margins are linked to rapid physico-chemical changes to the magma associated with loss of volatiles during the late stages of emplacement. Thus, rapid crystallization of groundmass olivines would deplete the magma in Ni, but increase Ca activity. The latter would be enhanced by decreasing pressure coupled with loss of CO2 from the carbonate-bearing kimberlite magma.For mantle olivines and the most refractory olivines in kimberlites (~ Fo94) to be in equilibrium with bulk rock compositions matching those of Mg-rich macrocrystic and aphanitic kimberlites (Mg# ~ 88) requires a mineral-melt Mg-Fe distribution coefficient of 0.47. This is well within the experimentally determined range for this distribution coefficient in carbonate-bearing systems. In southern African post-Gondwana alkaline pipe clusters, the average bulk rock Mg# and composition of the associated most Mg-rich olivine both decrease sympathetically from the interior to the continental margin, which is also consistent with a cognate origin for the olivines.A kimberlite magma following a plausible P-T trajectory relative to the CO2/H2O peridotite solidus would initially experience superheating, resulting in partial resorption of early-formed olivines that crystallized on the cool conduit walls. It would become supersaturated as it crossed the carbonated peridotite "ledge", resulting in tabular and hopper growth forms typical of euhedral olivine cores. With further ascent, the magma would once again become superheated, resulting in partial resorption of these cores. Thus, apparently complex textures and internal zonation patterns of kimberlitic olivines are predicted by a plausible magma P-T trajectory.

Moore, Andy E.

2012-01-01

170

Olivines from Kimberlites and Diamonds: Problem of Origin  

NASA Astrophysics Data System (ADS)

Mg-rich olivine Fo [100Mg/(Mg + Fe)] 85-94 is the principal mineral of kimberlites, peridotite xenoliths and diamond inclusions. It is completely altered in common kimberlites, however, it is absolutely fresh in a huge block from Udachnaya-East kimberlite in Yakutia (Russia). Pioneering studies of this unaltered kimberlite resulted in a discovery of high role of a mantle chlorine along with very low water content (Kamenetsky et al., 2004, Geology, 32: 845-848). Two olivine populations are distinguished, which are represented by oval-rounded unzoned or partly zoned xenocrysts of olivine I (more than 1 mm) and well defined zoned phenocrysts ( 0.05-1.0 mm) of olivine II (e.g. Kamenetsky et al., 2008, J.Petrol., 49: 823-839). The cores of olivine II are compositionally similar to olivine I with Mg# 86-94, but rims of olivine II and partly preserved rims of olivine I have constant Fo values about 89-90. We report here the results of major and minor elements analyses by EPMA of more than 300 grains of olivine I and olivine II, both of cores and rims by high precision approach (Sobolev et al., 2007, Science, 316: 412-417) to minor elements including Ti, Al, Cr, Ca, Mn, Ni, Co using the high sample current and high counting time, which was found optimal to obtain limit of detection about 10 ppm. Several grains of analyzed olivines contain clinopyroxene (cpx) and pyrope (prp) inclusions confirming their high pressure origin. One large olivine I grain contains clusters of cpx ( 33 grains) and prp ( 6 grains) inclusions., having a range in Cr2O3 (1.52- 2.36 wt%) , Al2O3 (0.99-5.53 wt%) and Na2O (1.45-5.96 wt%) for cpx and Cr2O3 (3.51-4.42 wt%) and CaO (5.64-6.61 wt%) for prp, showing disequilibrium in olivine I core, containing 200 ppm Ti. This is completely different from any peridotite xenoliths, confirming the uniqueness of this assemblage. The systematic high Ti ( more than 150 ppm) of all studied cores of olivine grains containing low T (Ca# 43.3-48) cpx and prp inclusions confirm the listed differences from all olivines from peridotites and diamonds (e.g. Sobolev et al., 2009, Lithos, 112S: 701-713.). Earlier, similar Ti abundance was reported only for olivines from dunite nodules in Greenland kimberlites (e.g. Arndt et al., 2010, J. Petrol., 51: 573-602).We suggest that Ti-bearing olivine, represented more that 70% of studied samples, is a part of high pressure pyrope lherzolite assemblage, which was formed and grew during the formation and early evolution of kimberlites

Sobolev, N. V.; Sobolev, A. V.; Tomilenko, A. A.; Kovyazin, S. V.; Kuzmin, D. V.

2011-12-01

171

Multiple Olivine Phase Transitions in the Shocked Martian Meteorite Tissint  

NASA Astrophysics Data System (ADS)

In some melt regions of Tissint olivine dissociated into silicate perovskite + magnesiowüstite while in others it transformed into ringwoodite. These different reactions and reaction mechanisms can be explained by local temperature variations.

Sharp, T. G.; Hu, J.; Walton, E. L.

2013-09-01

172

Olivine diogenites: The mantle of the eucrite parent body  

SciTech Connect

Two olivine-rich Antarctic diogenites (ALH A77256 and ALH 84001) of the howardite-eucritediogenite (HED) meteorite association have olivine/pyroxene ratios similar to normative ratios in devolatilized ordinary chondrites. Based on chemical data and petrological analysis, these meteorites represent the residuum of partial melting of the mantle in the eucrite parent body (EPB). Mineral assemblages in these olivine-rich diogenites record a continuum in thermal histories from initial partial melting (1150-1200{degree}C) to subsolidus re-equilibration (795 {plus minus} 55{degree}C). The small number of olivine-rich diogenites known hints that only the outer portion of the EPB has been sampled.

Sack, R.O.; Azeredo, W.J.; Lipschutz, M.E. (Purdue Univ., IN (USA))

1991-04-01

173

A Natural Example of Olivine LPO Variation With Shear Strain  

NASA Astrophysics Data System (ADS)

Understanding mantle rheology, seismic anisotropy, and strain localization requires knowledge of the evolution of olivine lattice preferred orientations (LPOs) as a function of strain and melt content. The Josephine Peridotite in southwest Oregon is ideal for analysis of the interaction of deformation and melt, due to the presence of shear zones with associated melt migration structures. We present results on the variation of olivine LPO with shear strain in these shear zones. The LPO evolution with proximity to the shear zone center provides a link between experimental data and LPO evolution models, which can be applied to the interpretation of mantle seismic anisotropy and to models of melt extraction at mid-ocean ridges. Results for harzburgites from the largest Josephine shear zone, which is 100m wide and contains syn-deformational dunite, indicate that the olivine LPO rotates in the shear zone so that the [100] maxima lies parallel to the shear direction. Outside of the shear zone, the harzburgites have a pre-existing LPO. Shear strain for the Josephine samples is calculated from the deflection angle of the regional pyroxene foliation. By ~100% shear strain, the olivine LPO evolves so that the [100] axis is aligned with the flow direction. These results on olivine LPO evolution during shear agree with the experimental data of Zhang and Karato (1995). They extend observations of olivine LPO to much higher strains and lower stresses. At face value, the Josephine shear zone data also agree with predictions from polycrystal plasticity models that incorporate the effects of dynamic recrystallization (Ribe and Yu, 1991; Wenk and Tomé, 1999). The variation of olivine LPO during simple shear is important for correctly interpreting seismic anisotropy. Our results indicate how much strain is necessary for olivine LPO to align in the flow direction. In conjunction with modelling studies, this information can be used to interpret the kinematics of deformation in regions where mantle anisotropy varies spatially.

Warren, J. M.; Hirth, G.

2005-12-01

174

Origin of plagioclase-olivine inclusions in carbonaceous chondrites  

Microsoft Academic Search

Plagioclase-Olivine Inclusions (POIs) are an abundant group of chondrule-like objects with igneous textures found in carbonaceous chondrites. POIs consist of plagioclase, olivine, pyroxene, and spinel, and cover a wide range of compositions between Type C Ca-Al-rich Inclusions (CAIs) and ferromagnesian chondrules. POIs are distinguished from CAIs by the absence of melilite, lack of refractory siderophile-rich opaque assemblages, more sodic plagioclase,

Y. J. Sheng; I. D. Hutcheon; G. J. Wasserburg

1991-01-01

175

Petrogenesis of olivine-phyric shergottite Yamato 980459, revisited  

Microsoft Academic Search

Primitive magmas provide critical information on mantle sources, but most Martian meteorites crystallized from fractionated melts. An olivine-phyric shergottite, Yamato 980459 (Y-980459), has been interpreted to represent a primary melt, because its olivine megacrysts have magnesian cores (Fo84–86) that appear to be in equilibrium with the Y-980459 whole-rock composition based on Fe–Mg partitioning. However, crystal size distribution (CSD) plots for

Tomohiro Usui; Harry Y. McSween Jr.; Christine Floss

2008-01-01

176

A precise olivine-augite Mg-Fe-exchange geothermometer  

Microsoft Academic Search

Olivine and augite that were experimentally equilibrated in the temperature interval 1175–1080°C at 1 bar in natural basaltic\\u000a and andesitic bulk compositions are used to calibrate an Mg-Fe2+ cation-exchange geothermometer. Within its temperature interval of experimental calibration, and over a broad range in olivine\\u000a Mg\\/Fe ratio, the geothermometer has a standard error of ±6°C. In compositionally simpler synthetic systems, the

Robert R. Loucks

1996-01-01

177

Waveform effects of a metastable olivine tongue in subducting slabs  

Microsoft Academic Search

We constructed velocity models of subducting slabs with a kinetically-depressed olivine ? ?- and ?-spinel transition, and examined the effect that such structures would have on teleseismic P waveforms using a full-wave finite-difference method. These two-dimensional calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO) to

John E. Vidale; Quentin Williams; Heidi Houston

1991-01-01

178

Waveform effects of a metastable olivine tongue in subducting slabs  

Microsoft Academic Search

Velocity models of subducting slabs with a kinetically-depressed olivine to beta- and gamma-spinel transition are constructed, and the effect that such structures would have on teleseismic P waveforms are examined using a full-wave finite-difference method. These 2D calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO)

John E. Vidale; Quentin Williams; Heidi Houston

1991-01-01

179

Spatial and Compositional Variations of Olivine in Terra Tyrrhena, Mars  

Microsoft Academic Search

Global modeling of thermal and VIS\\/NIR spectra of the Martian highlands reveal that many materials contain 10 - 20% olivine that spans a relatively large range of Mg\\/Fe contents (forsterite numbers 100 - 35). We examine the olivine-bearing locales in Terra Tyrrhena using TES-derived mineralogies, spectral variation maps made from THEMIS IR images, THEMIS and MOC visible images, MOLA topographic

W. C. Koeppen; V. E. Hamilton

2007-01-01

180

Dislocation recovery in fine-grained polycrystalline olivine  

Microsoft Academic Search

The rate of static dislocation recovery in Fo90 olivine has been studied under conditions of high temperature and controlled atmosphere in compressively deformed polycrystals\\u000a hot-pressed from synthetic (sol–gel) and natural (San Carlos) precursor powders. The sol–gel olivine, containing a small fraction\\u000a of orthopyroxene, was deformed to a final strain of 19% with a maximum differential stress of 266 MPa whereas the

R. J. M. Farla; H. Kokkonen; J. D. Fitz Gerald; A. Barnhoorn; U. H. Faul; I. Jackson

2011-01-01

181

Lithium iron phosphate\\/carbon nanocomposite film cathodes for high energy lithium ion batteries  

Microsoft Academic Search

This paper reports sol–gel derived nanostructured LiFePO4\\/carbon nanocomposite film cathodes exhibiting enhanced electrochemical properties and cyclic stabilities. LiFePO4\\/carbon films were obtained by spreading sol on Pt coated Si wafer followed by ambient drying overnight and annealing\\/pyrolysis at elevated temperature in nitrogen. Uniform and crack-free LiFePO4\\/carbon nanocomposite films were readily obtained and showed olivine phase as determined by means of X-Ray

Yanyi Liu; Dawei Liu; Qifeng Zhang; Danmei Yu; Jun Liu; Guozhong Cao

2011-01-01

182

Olivine Instability: An Experimental View of Mechanism of Deep Earthquakes  

NASA Astrophysics Data System (ADS)

Olivine (¦Á-(Mg,Fe)2SiO4) is the major constituent of the upper mantle and the ocean lithosphere. In subduction zone, where the earthquakes happen, the rheology of slab is mainly controlled by that of olivine. Several different mechanisms for deep focus earthquakes have been suggested, which include olivine instability (Bridgman, 1936; Orowan, 1960; Post, 1977; Ogawa, 1987; Hobbs and Ord, 1988; Kao and Chen, 1995), shear-induced melting (Griggs, 1954, 1972; Griggs and Handin, 1960; Griggs and Baker, 1969), phase transformation (Bridgman, 1945; Benioff, 1963; Meade and Jeanloz, 1989), dehydration of hydrous specimens (Meade and Jeanloz, 1991), and olivine metastability-induced anticrack (Green and Houston, 1995). Since the low temperature of the ¡°cold¡± slab, which can be as low as 600¡ãC in transition zone, olivine may still exist there and thus its shear instability may still be the possible mechanism for the deep-focus earthquakes. In our experimental study on deformation of San Carlos olivine at subduction zone conditions carried out on a D-DIA apparatus, Sam85 at X17B2, NSLS, we observed that the transitional temperature between regimes of insensitive to temperature and sensitive to temperature can be as high as 900¡ãC or even higher for the annealed polycrystal olivine sample, while that for unannealed sample can be as low as 450¡ãC. Our results for the unannealed sample are consistent to the result of Raterron et al (2004), which is concluded from the relaxation experiments. The annealed and unannealed olivine can be present the natural olivine in non-fault systems and that in pre-existing fault systems in subduction zone, respectively. We therefore propose a new olivine instability model with a ¡°sandwich¡± formation for the deep focus earthquakes: In this model the pre-existing fault system is surrounded by the no-fault systems. When the slab dives down, the olivine in both systems undergoes a stress- build-up process and can hold very high stress in both cases. However, as it keeps diving to the transition zone, the slab is heated and its temperature arrives at the boundary temperature from the insensitive temperature regime to the sensitive to temperature regime for the olivine in pre-existing fault system. As a result, while the olivine in non-fault system is still in regime of insensitive to temperature and can still hold the built high stress, the olivine in pre-existing fault system can not hold the built stress any more and gives a stress release. The pre- existing fault is re-active and heat from the re-active fault accelerates the ongoing process. Earthquake happens.

Long, H.; Weidner, D.; Li, L.; Chen, J.; Wang, L.

2007-12-01

183

A Method for the Flux Growth of Intermediate Composition Olivine  

NASA Astrophysics Data System (ADS)

Though solid solution of iron and magnesium between forsterite (Mg2SiO4) and fayalite (Fe2SiO4) is possible in the olivine crystal structure, the high oxygen fugacity condition of the terrestrial mantle inhibits the widespread crystallization of intermediate (Fo40-Fo60) composition olivine. This limitation is not the same for some other inner solar system bodies (e.g. the Moon and Mars), where conditions are reducing and olivine compositions are wide ranging. Unfortunately, the amount of samples from the Moon and Mars is extremely limited; with only Apollo and Luna mission samples, lunar meteorites, and Martian meteorites available for direct mineralogic and petrologic characterization. These characterizations have provided a useful basis for many spectroscopic and modeling interpretations, but many fundamental questions remain and may only be answerable through either direct observation of rocks or by analog experimentation. The motivation for our work on growth of intermediate olivine crystals, therefore, is to create realistic starting material for use in Mars and Moon analog experiments. A variety of crystal growth methods have been previously used to synthesize olivine, including: the Czochralski-pulling (CZ) method, the floating-zone image furnace (FZ) method, and sol-gel processing techniques. Both the CZ and FZ methods have the advantage of producing large crystals, but the growth apparatus and regulation of reduced atmospheric conditions during growth can make these techniques both time and cost intensive. Sol-gel processing to produces olivine fibers is a useful chemical technique, but obtaining larger grain sizes can be difficult. An alternative method for crystal growth is through the use a flux, which can grow crystals relatively quickly and inexpensively. We have grown synthetic crystals of intermediate composition (Fo30-Fo70) olivine using a lithium borate (B5Li3O9) flux. The starting material was a mixture of magnesite (MgCO3), siderite (FeCO3), and quartz (SiO2) powder in a 1:1:1 ratio. The advantage of using siderite is that the iron is already present in the ferrous form. Upon heating and decarbonation, this mixture represents a bulk composition of Fo50 (FeMgSiO4) olivine. Flux was then added to the starting material mixture so that the final mixture was 50% starting material and 50% flux by weight. This final mix was then placed in a platinum crucible that was heated to 1100 °C in a vacuum furnace for three days. The use of a vacuum furnace ensured that conditions remained reducing during crystal growth. The result was growth of olivine crystals that are generally small (< 1 mm in length) and have euhedral crystal form. These crystals have been analyzed by electron microprobe, and are systematically zoned from core to rim with Mg-rich cores (˜Fo70) transitioning to Fe-rich rims (˜Fo30). This zoning represents an expected heterogeneity due to olivine growth from a finite reservoir of starting material. The flux growth of this intermediate composition olivine was primarily a 'proof of concept' experiment, and showed that olivine crystals can be grown using a flux under sub-solidus conditions. Additional crystal growth experiments would be useful to gauge the response of olivine to changes in temperature, duration, and composition of the flux + starting material mixture.

Deangelis, M. T.; Anovitz, L. M.; Labotka, T. C.; Frederick, D. A.

2009-05-01

184

Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance  

SciTech Connect

Composite cathode materials in lithium ion batteries have become the subject of a great amount of research recently as cost and safety issues related to LiCoO2 and other layered structures have been discovered. Alternatives to these layered materials include materials with the spinel and olivine structures, but these present different problems, e.g. spinels have low capacities and cycle poorly at elevated temperatures, and olivines exhibit extremely low intrinsic conductivity. Previous work has shown that composite structures containing spinel and layered materials have shown improved electrochemical properties. These types of composite structures have been studied in order to evaluate their performance and safety characteristics necessary for use in lithium ion batteries in portable electronic devices, particularly hybrid-electric vehicles. In this study, we extended that work to layered-olivine and spinel-olivine composites. These materials were synthesized from precursor salts using three methods: direct reaction, ball-milling, and a coreshell synthesis method. X-ray diffraction spectra and electrochemical cycling data show that the core-shell method was the most successful in forming the desired products. The electrochemical performance of the cells containing the composite cathodes varied dramatically, but the low overpotential and reasonable capacities of the spinel-olivine composites make them a promising class for the next generation of lithium ion battery cathodes.

Ward, R.M.; Vaughey, J.T.

2006-01-01

185

B-type Olivine Fabric induced by Grain Boundary Sliding  

NASA Astrophysics Data System (ADS)

Olivine fabric, or Lattice Preferred Orientation (LPO), in naturally deformed peridotite largely contributes to the seismic anisotropy of the upper mantle. LPO usually results from motion of intra-crystalline dislocations during dislocation creep. In this case, experimental and numerical data indicate that the degree of mineral alignment (fabric strength) increases with increasing finite strain. Here, we show an opposite trend suggesting that olivine fabric can also result from a different deformation mechanism. Based on documentation of olivine LPOs in peridotites of a kilometer-scale mantle shear zone in the Ronda massif (Spain), we highlight a transition from a flow-parallel [a]- axis LPO (A-type fabric) to a flow-normal [a]-axis LPO (B-type fabric). While dislocation sub-structures indicate that A-type fabric results from dislocation motion, we conclude that the B-type fabric does not originate from dislocation creep, but instead from grain boundary sliding (GBS) because: (1) dislocation sub-structures remain consistent with the A-type slip system in all samples; (2) the fabric transition from A-type to B-type correlates with decreasing fabric strength despite increasing finite strain; and (3) our observations are supported by experiments that document B-type fabric in olivine aggregates where deformation involves a component of GBS. The B-type olivine fabric has a specific signature in term of seismic anisotropy, and hence, our results may have important implications for interpreting upper mantle structures and deformation processes via seismic observations.

Précigout, Jacques; Hirth, Greg

2013-04-01

186

An olivine-free mantle source of Hawaiian shield basalts.  

PubMed

More than 50 per cent of the Earth's upper mantle consists of olivine and it is generally thought that mantle-derived melts are generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. This can be resolved if the olivine of the mantle peridotite is consumed by reaction with melts derived from recycled oceanic crust, to form a secondary pyroxenitic source. Our modelling shows that more than half of Hawaiian magmas formed during the past 1 Myr came from this source. In addition, we estimate that the proportion of recycled (oceanic) crust varies from 30 per cent near the plume centre to insignificant levels at the plume edge. These results are also consistent with volcano volumes, magma volume flux and seismological observations. PMID:15800614

Sobolev, Alexander V; Hofmann, Albrecht W; Sobolev, Stephan V; Nikogosian, Igor K

2005-03-31

187

Dislocation recovery in fine-grained polycrystalline olivine  

NASA Astrophysics Data System (ADS)

The rate of static dislocation recovery in Fo90 olivine has been studied under conditions of high temperature and controlled atmosphere in compressively deformed polycrystals hot-pressed from synthetic (sol-gel) and natural (San Carlos) precursor powders. The sol-gel olivine, containing a small fraction of orthopyroxene, was deformed to a final strain of 19% with a maximum differential stress of 266 MPa whereas the San Carlos specimen was deformed to 15% strain and 260 MPa differential stress. Small samples cut from these deformed materials were annealed under high-temperature, controlled atmosphere conditions, for different durations to allow partial recovery of the dislocation sub-structures. Oxidative-decoration of the microstructural features, followed by backscattered electron imaging at 5 kV and image analysis, was used to determine dislocation density. The variation of dislocation density ? with time t at absolute temperature T was fitted to a second-order rate equation, in integral form, 1/?( t) - 1/?(0) = kt with k = k 0 exp(- E a/RT). The activation energy E a of the recovery process is 240 ± 43 and 355 ± 81 kJ mol-1 for sol-gel and San Carlos olivine polycrystals, respectively. The measured rates are one to two orders of magnitude lower than those reported in previous studies on natural single crystal olivine. The difference may be explained by several factors such as high dislocation densities measurable from large areas at high magnification for the SEM and the technique used to estimate dislocation densities. Comparison between fine-grained sol-gel olivine and the coarser-grained San Carlos olivine aggregate did not indicate that grain boundaries play an important role in dislocation recovery, but the absence of grain boundaries might also have contributed to the high dislocation recovery rates previously measured for single crystals.

Farla, R. J. M.; Kokkonen, H.; Fitz Gerald, J. D.; Barnhoorn, A.; Faul, U. H.; Jackson, I.

2011-05-01

188

Dislocation recovery in fine-grained polycrystalline olivine  

NASA Astrophysics Data System (ADS)

The rate of static dislocation recovery in Fo90 olivine has been studied under conditions of high temperature and controlled atmosphere in compressively deformed polycrystals hot-pressed from synthetic (sol-gel) and natural (San Carlos) precursor powders. The sol-gel olivine, containing a small fraction of orthopyroxene, was deformed to a final strain of 19% with a maximum differential stress of 266 MPa whereas the San Carlos specimen was deformed to 15% strain and 260 MPa differential stress. Small samples cut from these deformed materials were annealed under high-temperature, controlled atmosphere conditions, for different durations to allow partial recovery of the dislocation sub-structures. Oxidative-decoration of the microstructural features, followed by backscattered electron imaging at 5 kV and image analysis, was used to determine dislocation density. The variation of dislocation density ? with time t at absolute temperature T was fitted to a second-order rate equation, in integral form, 1/?(t) - 1/?(0) = kt with k = k 0 exp(-E a/RT). The activation energy E a of the recovery process is 240 ± 43 and 355 ± 81 kJ mol-1 for sol-gel and San Carlos olivine polycrystals, respectively. The measured rates are one to two orders of magnitude lower than those reported in previous studies on natural single crystal olivine. The difference may be explained by several factors such as high dislocation densities measurable from large areas at high magnification for the SEM and the technique used to estimate dislocation densities. Comparison between fine-grained sol-gel olivine and the coarser-grained San Carlos olivine aggregate did not indicate that grain boundaries play an important role in dislocation recovery, but the absence of grain boundaries might also have contributed to the high dislocation recovery rates previously measured for single crystals.

Farla, R. J. M.; Kokkonen, H.; Fitz Gerald, J. D.; Barnhoorn, A.; Faul, U. H.; Jackson, I.

2010-12-01

189

Rheology of olivine at high temperature and high pressure  

NASA Astrophysics Data System (ADS)

Two major contributions were accomplished in this dissertation. From the scientific aspect, the rheological properties of olivine at mantle condition were investigated by defining the flow mechanism and quantifying the high-pressure and high temperature flow law for olivine. From the technical development aspect, a breakthrough to measure macroscopic differential stress and strain rate in situ under mantle pressure and temperature condition was recorded in this dissertation. Conventional deformation methods in defining the flow law of olivine have to face factors of large uncertainties of differential stress measurements and/or limited confining pressure for deformation. These two difficulties were overcome by conducting high-temperature (up to 1473 K) deformation experiments of polycrystalline olivine (average grain size <5 micron) at pressure up to 8 GPa using large-volume high-pressure apparatus and synchrotron x-ray radiation. Strain rates of the deformation from x-ray radiograph of the sample itself were measured. Image analysis software for strain rate measurement was developed. Macroscopic differential stress of olivine was measured by monitoring the elastic strain of lattice spacing. The algorithms and programs were developed to convert the elastic strain of samples deformed under uniaxial compression into the macroscopic differential stress. In summary, the flow law for olivine at high temperature and high pressure has been defined as dislocation creep, assisted by dynamic recrystallization. The activation volume is characterized as 0˜5 cm3/mol. The technology developed in the course of this dissertation research opens new possibilities for rheological studies in the future. The accuracy of the results is comparable to the best rheological studies that are carried out in any system at the present.

Li, Li

190

Grinding methods to enhance the reactivity of olivine  

SciTech Connect

The Albany Research Center (ARC) conducted studies of mechanical activation by conventional and ultra-fine grinding techniques to enhance olivine reactivity in mineral carbonation reactions. Activated olivine is one of several solid feed materials used at ARC in reactions with carbon dioxide to form carbonate minerals. This paper compares grinding techniques via energy demand data and product characteristics, including particle size distributions, surface areas, full width at half maximum (FWHM) XRD analyses, and particle morphology by SEM analyses. Reactivity was gauged by percent conversion to carbonate in subsequent carbonation tests.

Summers, Cathy A.; Dahlin, David C.; Rush, Gilbert E.; O'Connor, William K.; Gerdemann, Stephen J.

2004-01-01

191

Laboratory spectra of amorphous and crystalline olivine: An application to comet Halley IR spectrum.  

National Technical Information Service (NTIS)

Among the various silicates proposed as components of cosmic dust grains, olivine is considered one of the most likely materials. In this work we present the infrared spectra of three different types of olivine grains: crystalline, amorphous, and syntheti...

A. Blanco V. Orofino E. Bussoletti S. Fonti L. Colangeli

1990-01-01

192

Ringwoodite Rims Around Olivine Fragments in Melt Vein of Antarctic Chondrite GRV 022321: Transformation Kinetics  

NASA Astrophysics Data System (ADS)

Ringwoodite rims around olivine in shocked veins of chondrites GRV 022321 were investigated by electron microscopes to elucidate mechanisms of transformation and Mg-Fe diffusion of olivine to ringwoodite, and estimate shock duration using kinetics.

Xie, Z.; Li, X.; Sharp, T. G.; DeCarli, P. S.

2013-09-01

193

Mineralogy of Stardust Track 112 Particle: Relation to Amoeboid Olivine Aggregates  

NASA Astrophysics Data System (ADS)

We have examined the relationships between T112 particle and amoeboid olivine aggregates. Slight enrichment of Fe in olivine rim and associated chromites suggest that T112 may have experienced a minor degree of metamorphism.

Komatsu, M.; Fagan, T.; Mikouchi, T.; Miyamoto, M.; Zolensky, M.; Ohsumi, K.

2012-03-01

194

Optimization of Carbon Coatings on LiFePO4  

SciTech Connect

The electrochemical performance of LiFePO{sub 4} in lithium cells is strongly dependent on the structure (disordered/graphene or D/G ratio) of the in situ carbon produced during synthesis from carbon-containing precursors. Addition of pyromellitic acid (PA) prior to final calcination results in lower D/G ratios, yielding a higher-rate material. Further, improvements in electrochemical performance are realized when graphitization catalysts such as ferrocene are also added during LiFePO{sub 4} preparation, although overall carbon content is still less than 2 wt.%.

Doeff, Marca M.; Wilcox, James D.; Kostecki, Robert; Lau, Grace

2005-07-14

195

Origins of compositional heterogeneity in olivine-hosted melt inclusions from the Baffin Island picrites  

Microsoft Academic Search

The Baffin Island picrites are highly magnesian (<=22 wt% MgO) olivine tholeiites, erupted through felsic continental crust. Plots of most major and minor element oxides against MgO for the lavas define very tight trends consistent with modification of melts parental to the erupted suite by olivine fractionation or accumulation. However, melt inclusions trapped in primitive olivine phenocrysts in these lavas

Gregory M. Yaxley; Vadim S. Kamenetsky; Maya Kamenetsky; Marc D. Norman; Don Francis

2004-01-01

196

Search for olivine in the Vesta surface from the Dawn-VIR hyperspectral data  

NASA Astrophysics Data System (ADS)

We study the possibility to discern the infrared spectral signature of olivine in pyroxene based multimineralic mixtures. Different spectral indexes are selected and tested onto laboratory controlled spectral set of mixtures. The best index able to detect even low amount of olivines, will be applied to the VIR-Dawn dataset to search for olivine on the surface of Vesta.

Palomba, E.; Longobardo, A.; De Sanctis, M. C.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Farina, M.; Frigeri, A.; Tosi, F.; Zambon, F.; McSween, H. Y.; Mittlefehldt, D. H.; Russell, C. T.; Beck, A.; Toplis, M. J.; McFadden, L.; Cloutis, E.

2012-09-01

197

Hydroxide in olivine: A quantitative determination of the absolute amount and calibration of the IR spectrum  

Microsoft Academic Search

Olivine is an important host of hydrogen in the Earth's upper mantle, and the OH abundance in this mineral determines many important physical properties of the planet's interior. To date, natural and experimentally hydrated olivines have been analyzed by uncalibrated spectroscopic methods with large (±100%) uncertainties in accuracy. We determined the hydrogen contents of three natural olivines by 15N nuclear

David R. Bell; George R. Rossman; Joachim Maldener; Denis Endisch; Friedel Rauch

2003-01-01

198

The geoengineering potential of artificially enhanced silicate weathering of olivine  

Microsoft Academic Search

Geoengineering is a proposed action to manipulate Earth's climate in order to counteract global warming from anthropogenic greenhouse gas emissions. We investigate in more detail the potential of a specific geoengineering technique, the carbon sequestration by artificially enhanced silicate weathering via the dissolution of olivine. This approach would not only operate against rising temperatures but would also oppose ocean acidification,

Peter Köhler; Jens Hartmann; Dieter A. Wolf-Gladrow

2010-01-01

199

Hydroxyl in mantle olivine xenocrysts from the Udachnaya kimberlite pipe  

Microsoft Academic Search

The incorporation of hydrogen in mantle olivine xenocrysts from the Udachnaya kimberlite pipe was investigated by Fourier-transform infrared spectroscopy and secondary ion mass spectrometry (SIMS). IR spectra were collected in the OH stretching region on oriented single crystals using a conventional IR source at ambient conditions and in situ at temperatures down to ?180°C as well as with IR synchrotron

Monika Koch-Müller; Stanislav S. Matsyuk; Dieter Rhede; Richard Wirth; Natasha Khisina

2006-01-01

200

Surface modification of olivine by H + and He + bombardment  

Microsoft Academic Search

Laboratory simulations of solar wind irradiation of olivine, a constituent of ordinary chondritic meteorites and S-type asteroids, show a dramatic chemical reduction of surface iron and, to a lesser extent, silicon. Earth's atmosphere oxidizes any reduced iron instantaneously, whereas irradiated material on the surface of an asteroid would remain reduced. Changes in optical reflectance, due to metallization of the surface,

C. A. Dukes; R. A. Baragiola; L. A. McFadden

1999-01-01

201

Investigating Asteroids on the Olivine-to-Pyroxene Continuum  

NASA Astrophysics Data System (ADS)

The spectral characteristics of asteroids having a strong 1 um absorption feature are attributed to the presence of pyroxene, olivine, or both. Distinguishing between pyroxene and olivine requires measuring the strength of an additional absorption band centered near 2 um. Accurate measurements of both bands are now possible using SpeX, a new generation low- to medium-resolution infrared spectrograph in operation as a facility instrument at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Visible-wavelength surveys such as SMASSII (Bus 1999; Ph. D. thesis) show a continuum of properties in terms of spectral slope and the depth of the 1 um band, as measured over the wavelength interval 0.4-1.0 um. With SpeX, we are now examining whether this apparent continuum is also evident within spectra extending out to 2.5 um. Taking advantage of our ability to infer mineralogy based on near-infrared spectral information, we are also seeking to understand the extent to which this spectral continuum is rooted in a smooth gradient in olivine-pyroxene mineralogy. We are estimating olivine-pyroxene ratios using the Modified Gaussian Model (MGM) of Sunshine et al. (1990, JGR 95, 6955).

Bus, S. J.; Sunshine, J. M.; Binzel, R. P.; Burbine, T. H.

2001-11-01

202

Challenges in detecting olivine on the surface of 4 Vesta  

NASA Astrophysics Data System (ADS)

Identifying and mapping olivine on asteroid 4 Vesta are important components to understanding differentiation on that body, which is one of the objectives of the Dawn mission. Harzburgitic diogenites are the main olivine-bearing lithology in the howardite-eucrite-diogenite (HED) meteorites, a group of samples thought to originate from Vesta. Here, we examine all the Antarctic harzburgites and estimate that, on scales resolvable by Dawn, olivine abundances in putative harzburgite exposures on the surface of Vesta are likely at best in the 10-30% range, but probably lower due to impact mixing. We examine the visible/near-infrared spectra of two harzburgitic diogenites representative of the 10-30% olivine range and demonstrate that they are spectrally indistinguishable from orthopyroxenitic diogenites, the dominant diogenitic lithology in the HED group. This suggests that the visible/near-infrared spectrometer onboard Dawn (VIR) will be unable to resolve harzburgites from orthopyroxenites on the surface of Vesta, which may explain the current lack of identification of harzburgitic diogenite on Vesta.

Beck, Andrew W.; McCoy, Timothy J.; Sunshine, Jessica M.; Viviano, Christina E.; Corrigan, Catherine M.; Hiroi, Takahiro; Mayne, Rhiannon G.

2013-07-01

203

Micromechanical modeling of the viscoplastic behavior of olivine  

NASA Astrophysics Data System (ADS)

Efforts to couple mantle flow models with rheological theories of mineral deformation typically ignore the effect of texture development on flow evolution. The fact that there are only three easy slip systems for dislocation glide in olivine crystals leads to strong mechanical interactions between the grains as the deformation proceeds, and subsequent development of large viscoplastic anisotropy in polycrystals exhibiting pronounced Lattice Preferred Orientations. Using full-field simulations for creep in dry polycrystalline olivine at high temperature and low pressure, it is shown that very large stress and strain rate intragranular heterogeneities can build up with deformation, which increase dramatically with the strength of the hard slip system (included for the purpose of enabling general deformations). Compared with earlier nonlinear extensions of the Self-Consistent mean-field theory to simulate polycrystal deformation, the "Second-Order" method is the only one capable of accurately describing the effect of intraphase stress heterogeneities on the macroscopic flow stress, as well as on the local stress- and strain rate fluctuations in the material. In particular, this approach correctly predicts that olivine polycrystals can deform with only four independent slip systems. The resistance of the fourth system (or accommodation mechanism), which is likely provided by dislocation climb or grain boundary processes as has been observed experimentally, may essentially determine the flow stress of olivine polycrystals. We further show that the "tangent" model, which had been used extensively in prior geophysical studies of the mantle, departs significantly from the full-field reference solutions.

Castelnau, O.; Blackman, D. K.; Lebensohn, R. A.; Ponte CastañEda, P.

2008-09-01

204

Deformation of olivine in torsion under hydrous conditions  

NASA Astrophysics Data System (ADS)

We performed torsional deformation experiments on pre-hydrated fine-grained olivine aggregates using an innovative experimental assembly to investigate water weakening in mantle rocks at high shear strains. San Carlos olivine powder was cold-pressed and then hot-pressed under hydrous conditions, producing aggregates with average grain sizes of 7 or 15 ?m. Deformation experiments were performed in a high-resolution gas-medium apparatus equipped with a torsional actuator, under a confining pressure of 300 MPa, a temperature of 1200 °C, and constant shear strain rates ranging from 8 × 10-5 to 1.4 × 10-4 s-1. Maximum shear stresses range from 150 to 195 MPa. These values are 30% lower relative to those determined in previous torsion experiments on dry, fined-grained dunites under similar conditions. Textures and microstructures of the starting and deformed specimens were characterized by scanning and transmission electron microscopy. All deformed aggregates exhibit a shape-preferred orientation marking a foliation and lineation, as well as a reduction in mean grain size from 15 ?m down to 3-4 ?m due to dynamic recrystallization. Olivine crystallographic fabrics developed rapidly (? < 0.1), but their strength, characterized by the J-index, is low compared to naturally deformed peridotites or to polycrystalline olivine deformed at similar finite shear strains under dry conditions. The crystallographic fabrics are consistent with deformation by a dislocation accommodated creep mechanism with activation of multiple {0 k l}[1 0 0] systems, among which the (0 1 0)[1 0 0] slip system is dominant, and minor participation of the (0 1 0)[0 0 1] slip system. Transmission electron microscopy confirmed the occurrence of dislocations with [1 0 0] and [0 0 1] Burgers vectors in most grains. Analysis of unpolarized infrared spectra indicates that hydrogen concentration in the olivine lattice is below the saturation level of 18 ppm wt H2O, which is similar to those typically observed in spinel-bearing peridotite xenoliths, and also provide evidence for water-rich inter-granular material trapped in pores and grain boundaries. Seismic properties computed from the CPO observations correspond to those most commonly observed in naturally deformed mantle peridotites with fast P-wave propagation and S-wave polarization subparallel to the shear direction. These torsion experiments on fine-grained olivine polycrystals under hydrous conditions indicate that water weakening under lithospheric conditions is linked to various defects with hydrogen in the olivine structure, as well as with water-derived species in grain boundaries or pores.

Demouchy, Sylvie; Tommasi, Andréa; Barou, Fabrice; Mainprice, David; Cordier, Patrick

2012-08-01

205

Activities of olivine slip systems in the upper mantle  

NASA Astrophysics Data System (ADS)

We investigated the effect of pressure (P) on olivine [1 0 0](0 0 1) and [0 0 1](1 0 0) dislocation slip systems by carrying out deformation experiments in the Deformation-DIA apparatus (D-DIA) on single crystals of Mg2SiO4 forsterite (Fo100) and San Carlos (SC) olivine (Fo89), at P ranging from 5.7 to 9.7 GPa, temperature T = 1473 and 1673 K, differential stress ? in the range 140-1500 MPa, and in water-poor conditions. Specimens were deformed in axisymmetry compression along the so-called [1 0 1]c crystallographic direction, which promotes the dual slip of [1 0 0] dislocations in (0 0 1) plane and [0 0 1] dislocations in (1 0 0) plane. Constant ? and specimen strain rates (??) were monitored in situ by synchrotron X-ray diffraction and radiography, respectively. Comparison of the obtained high-P rheological data with room-P data, previously reported by Darot and Gueguen (1981) for Fo100 and Bai et al. (1991) for SC olivine, allowed quantifying the activation volume V* in classical creep power laws. We obtain V* = 9.1 ± 1.6 cm3/mol for Fo100. For SC olivine, we obtain V* = 10.7 ± 5.0 cm3/mol taking into account the oxygen-fugacity uncertainty during the high-P runs. These results, combined with previous reports, provide complete sets of parameters for quantifying the activities of olivine dislocation slip systems. Extrapolation of the rheological laws obtained for SC olivine crystals to conditions representative of natural deformations show that [1 0 0](0 1 0) slip largely dominates deformation in the shallow upper mantle. At depths greater than ˜65 km along a 20-Ma oceanic geotherm or ˜155 km along a continental geotherm, the dual activity of [1 0 0](0 0 1) and [0 0 1](1 0 0) slips becomes comparable to that of [1 0 0](0 1 0) slip. At depths greater than ˜240 km, [0 0 1](0 1 0) slip becomes dominant over all other investigated slip systems. Such changes in olivine dislocation-slips relative activity provide a straightforward explanation for the seismic anisotropy contrast and attenuation with depth observed in the Earth's upper mantle.

Raterron, Paul; Girard, Jennifer; Chen, Jiuhua

2012-06-01

206

Olivine as a key to unlocking Kilauea's magmatic history  

NASA Astrophysics Data System (ADS)

Olivine is a ubiquitous mineral in Hawaiian basalts. It is on the liquidus at pressures <0.5 GPa and has the potential to record numerous petrologic processes including the histories of parental magma composition changes, crystal fractionation, magma mixing and crustal contamination. These processes are recorded in olivine composition (major and trace elements, and isotopes) and by melt inclusions trapped within olivine. Here we focus on Kilauea's historical lavas (1820-present) to evaluate the magmatic history one of world's most active volcanoes. Kilauea has shown dramatic variations in it eruptive rate and style (from vigorous, quiescent effusion in 1820 to infrequent explosive activity in 1924 and then to its highest effusion during the last decade). Eruption rates correlate with whole-rock compositional and isotopic variations (P-G 1999). Most Kilauea lavas have normally zoned olivine in equilibrium with whole-rock compositions which belies complex magma chamber processes. Parental magma composition changed rapidly based on the heterogeneity of melt inclusion compositions in higher Mg olivine (>86 forsterite). Melt inclusions from single eruptions show wider variation in ratios of Ca/Al and Nb/Y than observed in lavas for the historical period. Thus, the mantle source is heterogeneous on a small scale and small batches of compositionally distinct melt are frequently delivered to the volcano. These magma batches undergo mixing, fractionation and after caldera collapses (e.g.1924), crustal contamination in the summit reservoir. This work demonstrates that an Ernstonian approach, using minerals to understand petrologic processes, is key to unlocking Kilauea's magmatic processes. Pietruszka, A.P. and Garcia, M.O., 1999, J. Petrol. 40, 1321-1342.

Garcia, M. O.; Norman, M. D.

2011-12-01

207

Rheological studies of olivine under high pressure and temperature  

NASA Astrophysics Data System (ADS)

The rheological properties of San Carlos olivine and forsterite were studied under simultaneous high pressure and temperature conditions on the cubic anvil high-pressure apparatus. Using the synchrotron x-ray diffraction method, elastic strain, stress and strain rate information were extracted, and the flow laws on olivine were derived by fitting the experimental data. The microstructures of samples quenched under high pressure at different temperatures were observed using transmission electron microscopy (TEM). The rheology of lab-dry San Carlos olivine was studied up to 9 GPa and 800°C. Our results show that lab-dry San Carlos olivine reaches yield point around 5.4 GPa differential stress at room temperature. The yield stress increases with the loading pressure and decreases with the increasing temperature. A dramatic decrease in strength occurs around 430--500°C that reflects a change of the flow mechanism. Two different flow laws at 9 GPa at different temperature regimes have been derived based on the experimental data. A 3? -sigma-T deformation map was constructed using the derived flow laws. TEM observations reveal that c dislocation glide and recrystallization are the active deformation processes responsible for the stress instability above 400°C. It is believed that this stress instability can provide experimental constraints for the possible existence of a run-away plastic instability process that may be the cause of the deep earthquakes. The variation of the differential stress with temperature and pressure was studied on both lab-dry and dehydrated forsterite samples up to 9 GPa confining pressure and 1000°C. Lab-dry forsterite exhibits identical rheological behaviors at similar pressure and temperature conditions as that of San Carlos olivine. The dehydrated forsterite sample behaves quite similarly to the lab-dry sample at room temperature, and appears to be stronger at high temperature. The water content in the sample can affect the critical temperature where the stress instability would be operative.

Wu, Yujun

2000-10-01

208

Kamacite and olivine in ordinary chondrites: Intergroup and intragroup relationships  

SciTech Connect

The three principal groups of ordinary chondrites (OCs), H (high total Fe), L (low total Fe), and LL (low total Fe, low metallic Fe), constitute {approximately}80% of all meteorites observed to fall. In going from H to L to LL chondrites, the abundances of siderophile elements decrease and the degree of oxidation increases. The proportion of oxidized Fe (i.e., FeO in silicates) increases at the expense of metallic Fe. Because Fe is more readily oxidized than Ni or Co, bulk metal becomes increasingly rich in Ni and Co (e.g., Prior, 1916). Equilibrated LL chondrites are thus characterized by high FeO/(FeO + MgO) ratios in olivine and low-Ca pyroxene, high taenite/kamacite ratios, and the occurrence of Co-rich kamacite. The present study reports high-precision electron microprobe analyses of olivine and kamacite in a large suite of OCs. The purpose of the study was sixfold: (1) rigorously define the compositional ranges of these phases for each OC group, (2) identify anomalous OCs whose olivine and/or kamacite compositions lie outside the established ranges, and hence may not belong to the three main OC groups, (3) characterize the phases in the chondritic clasts of the Netschaevo iron meteorite and determine how closely related Netschaevo is to OCs, (4) determine if there are intragroup variations of olivine and kamacite compositions with petrologic type, (5) identify those OCs as fragmental breccias that contain some olivine and/or kamacite grains with aberrant compositions, and (6) search for new metallic Fe-Ni phases with extreme compositions. An expected by-product of this investigation was that a few meteorites that previously had not been well-characterized would be reclassified.

Rubin, A.E. (Univ. of California, Los Angeles (USA))

1990-05-01

209

Reaction-induced weakening of plagioclase olivine composites  

NASA Astrophysics Data System (ADS)

The localisation of strain into natural ductile shear zones is often associated with the occurrence of metamorphic reactions. In order to study the effects of solid solid mineral reactions on plastic deformation of rocks, we have investigated the shear deformation of plagioclase olivine composites during the reaction plagioclase + olivine ? orthopyroxene + clinopyroxene + spinel (± garnet). Microstructures of plagioclase olivine composites were studied after shear deformation experiments in a Griggs apparatus. Experiments were performed on anorthite forsterite (An Fo) and labradorite forsterite (Lab Fo) composites at 900 °C, confining pressures between 1000 1600 MPa and with constant shear strain rates of ˜5 × 10-5 s-1. In absence of reaction, Lab Fo composites are stronger than pure olivine and labradorite end-members that deform with a high temperature plasticity mechanism. Lab Fo composites strain harden due to the inhibition of extensive recrystallisation by interphase boundaries. In An Fo composites, the reaction induces strain weakening by a switch from dislocation creep to grain size sensitive deformation mechanisms through the development of fine-grained (size < 0.5 ?m) polyphase reaction products. Interconnecting layers of reaction products accommodate most of the applied strain by grain size sensitive creep. Recovery processes are pronounced during syndeformational reaction: original anorthite and olivine dynamically recrystallise by subgrain rotation and bulging recrystallisation. Presumably, the dynamic recrystallisation is caused by reduced stress conditions and partitioning of strain and strain rates between the new reaction products and the relict An Fo grains. The results of our experiments are in good agreement with natural observations of shear localisation in the lower crust and upper mantle, and imply that anhydrous mineral reactions can be important causes for localisation of deformation.

de Ronde, A. A.; Stünitz, H.; Tullis, J.; Heilbronner, R.

2005-11-01

210

Geoengineering potential of artificially enhanced silicate weathering of olivine  

PubMed Central

Geoengineering is a proposed action to manipulate Earth’s climate in order to counteract global warming from anthropogenic greenhouse gas emissions. We investigate the potential of a specific geoengineering technique, carbon sequestration by artificially enhanced silicate weathering via the dissolution of olivine. This approach would not only operate against rising temperatures but would also oppose ocean acidification, because it influences the global climate via the carbon cycle. If important details of the marine chemistry are taken into consideration, a new mass ratio of CO2 sequestration per olivine dissolution of about 1 is achieved, 20% smaller than previously assumed. We calculate that this approach has the potential to sequestrate up to 1 Pg of C per year directly, if olivine is distributed as fine powder over land areas of the humid tropics, but this rate is limited by the saturation concentration of silicic acid. In our calculations for the Amazon and Congo river catchments, a maximum annual dissolution of 1.8 and 0.4 Pg of olivine seems possible, corresponding to the sequestration of 0.5 and 0.1 Pg of C per year, but these upper limit sequestration rates come at the environmental cost of pH values in the rivers rising to 8.2. Open water dissolution of fine-grained olivine and an enhancement of the biological pump by the rising riverine input of silicic acid might increase our estimate of the carbon sequestration, but additional research is needed here. We finally calculate with a carbon cycle model the consequences of sequestration rates of 1–5 Pg of C per year for the 21st century by this technique.

Kohler, Peter; Hartmann, Jens; Wolf-Gladrow, Dieter A.

2010-01-01

211

Local structure in the Li-ion battery cathode material Li x (Mn y Fe 1? y )PO 4 for 0 < x ? 1 and y = 0.0, 0.5 and 1.0  

Microsoft Academic Search

Infrared and Raman spectroscopy have been used to investigate the Li-ion battery cathode materials Lix(MnyFe1?y)PO4 for 0

Christopher M. Burba; Roger Frech

2007-01-01

212

Controls on helium solubility in olivine at low pressures  

NASA Astrophysics Data System (ADS)

Experiments on the solubility of helium in olivine have been conducted over a range of conditions to evaluate the thermodynamic controls on helium partitioning during melting. The experiments were performed at 1 to 150 atm. total pressure at temperatures between 1350 and 1550° C. Helium partial pressures ranged from 0.5 to 150 atm. The effect of oxygen fugacity was examined by running experiments at both the QFM and Ni-NiO buffer, and by using both Fe-bearing and Fe-free olivines. Temperature: Experiments at 1350, 1450 and 1550° C (Ni-NiO buffer) show a clear decreasing solubility of helium with temperature, as expected for a gas dissolving in a solid. In contrast, previous experiments on basaltic melts show little change of helium solubility with temperature. Therefore the olivine-melt D value decreases steadily with temperature. Linear regression yields the equation DHe=-8.8e-6T+ 0.014 (with R2 > 0.999), where T is in degrees C. Using the van't Hoff equation, this implies an enthalpy of solution of -2.0 kJ/mole and an entropy of solution of -1.97 J/mole K. Pressure: Experiments on powdered samples at helium partial pressures of 0.5 and 150 atmospheres suggest a Henry's law constant between 1e-6 and 3e-6 STP cc/g/atm. This value is around 2 orders of magnitude lower than the Henry's law constant for basaltic melts, consistent with the higher density of olivine. Note that these values should be taken as preliminary as only two helium partial pressures have been studied so far and there are large uncertainties in analyzing powdered samples. Oxygen Fugacity: Experiments on Fe-bearing and Fe-free olivine as well as at varying oxygen fugacity indicate that at least some He is located in vacancies associated with Fe3+ in the olivine crystal lattice. A single experiment at the QFM buffer suggests a DHe at 1 atm. of ~0.001, a factor of 2-3 lower than at Ni-NiO. Assuming that the measured Henry's law constant is valid at high pressure, that mantle melting takes place between temperatures of 1200 and 1450° C and that fO2 conditions are near the QFM buffer, our experiments suggest D values during mantle melting of 0.001 to 0.002.

Parman, S. W.; Kurz, M. D.; Hart, S. R.; Grove, T. L.

2005-12-01

213

Magmatic versus metamorphic origin of olivine-plagioclase coronas  

NASA Astrophysics Data System (ADS)

An SEM, REE, and mineral Sm-Nd isotope study on olivine-plagioclase coronas in the Vestre Dale gabbro, Norway, was carried out in order to solve the temporal relationships within these coronas. It is demonstrated that in contrast to common models, corona formation is a multistage, late-magmatic process, starting with the formation of orthopyroxene by (partial) dissolution of olivine, followed by the nucleation and rapid outward growth of orthopyroxene+spinel symplectites at its outer margin, and concluded by replacement of this precursory outer shell by calcic amphibole. Isotopic equilibrium between inner shell orthopyroxene and the magmatic assemblage, and the REE contents of orthopyroxene and outer shell amphibole also provide strong arguments for a magmatic origin, with the local availability of fractionated magma acting as a limiting factor. The absence of replacement of intercumulus clinopyroxene by amphibole also favours a late stage magmatic rather than a metamorphic origin for corona amphibole.

de Haas, Geert-Jan; Nijland, Timo; Valbracht, Peter; Maijer, Cees; Verschure, Rob; Andersen, Tom

2002-05-01

214

Grinding methods to enhance the reactivity of olivine  

SciTech Connect

The Albany Research Center (ARC) conducted studies of mechanical activation by conventional and ultrafine grinding techniques to enhance olivine reactivity in mineral carbonation reactions. Activated olivine is one of several solid feed materials used at ARC in reactions with carbon dioxide to form carbonate minerals. This paper compares grinding techniques via energy demand data and product characteristics, including particle size distributions, surface areas, full-width-at-half-maximum (FWHM) XRD analyses, and particle morphology by SEM analyses. Reactivity was calculated by percent conversion to carbonate in subsequent carbonation tests. Particle size reduction has the greatest impact on reactivity, and wet grinding is more energy efficient than dry grinding. Large additional inputs of energy to increase surface area or reduce crystallinity do not result in proportional improvements in reactivity.

Summers, Cathy A.; Dahlin, David C.; Rush, Gilbert E.; O'Connor, William K.; Gerdemann, Stephen J.

2005-08-01

215

Visualizing frozen point defect tracks in Fe-containing olivines  

NASA Astrophysics Data System (ADS)

Using a combination of first-principles calculations and Monte Carlo simulations, we show that Fe-containing silicates such as olivines naturally offer a way for visualizing tracks left by diffusing vacancies. Fe in its 2+ and 3+ valency states prefers two distinct cation sites in the olivine structure. Vacancies formed at the cationic M sites, cause neighboring Fe ions in their normally occurring Fe2+ state to change valency to Fe3+, compensating for the charge imbalance and reducing energy costs, consequently altering the local site preference of Fe. Once the vacancy diffuses away, Fe atoms remain stuck in their metastable location producing a microscopic record of the vacancy's trajectory. Our results may be verified using high-resolution transmission electron microscopy, combined with electron energy-loss spectroscopy.

Chatterjee, S.; Saha-Dasgupta, T.; Sengupta, S.

2012-04-01

216

Olivine and pyroxene-rich deposits in Holden Crater, Mars  

NASA Astrophysics Data System (ADS)

Holden crater is a ~150 km diameter crater centered at 326 E, 26S breached in the south by Uzboi Vallis. Holden has been proposed as a possible landing site for the Mars Science Laboratory (MSL) rover and has been the subject of intense scrutiny due to its potential as a paleolake basin. Near the region where Uzboi Vallis breaches the southern Holden Crater wall are layered rocks that have been suggested to be aqeously deposited. Additionally, fan-shaped deposits originate in the southern and western crater walls that have been interpreted as alluvial fans and fan deltas. New analyses of THEMIS and TES data indicate that both the basement and layered rocks - those interpreted to have been deposited in an aqueous environment - near the breach point of Holden crater are olivine and pyoxene- rich. Based on THEMIS IR imagery, these units have a higher thermal inertia than the surrounding terrain. The higher-TI units correspond with lighter-toned layered units seen in THEMIS Vis and MOC imagery that also have a distinct mafic signature in THEMIS daytime IR false-color decorrelation stretch images. The fan deposit in western Holden Crater, which has been proposed as a specific landing site for MSL may also have an elevated olivine abundance based on TES data. High olivine and pyroxene abundances in the sedimentary units of Holden crater do not preclude the presence of water in the history of the crater. However, based on analysis of TES and THEMIS data over the region, there is no evidence for extended chemical weathering present at the surface. Olivine-rich bedrock is likely to be a regional property as it is also present in chaos terrain to the northeast of Holden which is the source of the Landon Vallis outflow channel. These regions should be considered high priority targets for future investigations by OMEGA and CRISM.

Glotch, T. D.

2006-12-01

217

An olivine-microchondrule-bearing clast in the Krymka meteorite  

SciTech Connect

A small (150 x 200-micron-size) clast consisting of 20 vol pct olivine microchondrules (with barred and granular textures) and 80 vol pct recrystallized silicate matrix material occurs in Krymka (LL3.1). This is the fourth microchondrule-bearing clast to be described. The chondrules are zoned in FeO with concentrations increasing toward the surface. The clast most closely resembles a previously described radial-pyroxene-microchondrule-bearing clast in Piancaldoli (LL3.4). 8 refs.

Rubin, A.E. (California Univ., Los Angeles (USA))

1989-09-01

218

Nickeliferous sulfides in xenoliths, olivine megacrysts and basaltic glass  

Microsoft Academic Search

The composition of olivine and nickeliferous sulfide inclusions from a selection of mafic and ultramafre rocks, xenoliths and megacrysts, including picritic basalts from Kilauea Volcano, Hawaii, kimberlite from Fayette County, Pennsylvania, and megacrysts from Mount Shasta, California are compared with the mean experimental value of the distribution coefficient for Ni\\/Fe exchange (KD3=32). Only nine of the forty five olivipe\\/bulk-sulfide pairs

Michael E. Fleet; William E. Stone

1990-01-01

219

Space Weathering Evolution on Airless Bodies - Laboratory Simulations with Olivine  

NASA Astrophysics Data System (ADS)

Lunar-type space weathering of airless bodies is associated with nanophase iron (npFe0) production in Fe bearing silicate minerals that is often responsible for observable changes of its reflectance spectra. A new method of controlled npFe0 production on olivine grains was developed in order to quantitatively evaluate spectral changes related to space weathering and presence of npFe0. Through a two-step thermal treatment a series of olivine samples with increasing concentration of iron nanoparticles on the grain surfaces was prepared. The grain size of the npFe0 particles was kept in the same range 5-20 nm). Magnetic methods were used to estimate npFe0 concentration. Compared to fresh olivine, treated samples exhibit the spectral characteristics of lunar type space weathering (darkening, shallowing of 1 µm olivine absorption band, and reddening) related to increasing presence of npFe0. From quantitative point of view, a logarithmic trend was found between spectral changes and npFe0 concentration. One sample with additional population of larger ~50 nm npFe0 particles follows the darkening and the 1 µm band shallowing trend, but does not fully follow the reddening trend. This is due to fact that the larger 40 50 nm sized) npFe0 particles do not contribute to the spectral slope change. The observed logarithmic trend between the spectral changes and the npFe0 concentration give constrains on time evolution of space weathering. In the case of constant micro impact, solar wind and cosmic radiation on a regolith, the npFe0 concentration increases linearly with time while spectral changes related to space weathering evolve logarithmically with time.

Kohout, Tomas; Cuda, J.; Bradley, T.; Britt, D.; Filip, J.; Tucek, J.; Malina, O.; Kaslik, J.; Siskova, K.; Kletetschka, G.; Zboril, R.

2013-10-01

220

Experimental deformation of olivine single crystals at lithospheric temperatures  

NASA Astrophysics Data System (ADS)

Rheological properties of mantle minerals and rocks at temperatures (T) appropriate to much of Earth's lithosphere have remained poorly constrained, even though past experimental studies on olivine single crystals and polycrystalline aggregates have quantified the high-temperature creep mechanisms (T > 1200°C). Consequently, we have performed deformation experiments on crystals of San Carlos olivine at lower temperatures, from 900° to 1200°C, in triaxial compression along the [101]c direction. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at differential stresses of 100 to 500 MPa. Several samples were deformed at constant displacement rate and others at constant load, in order to provide insight into possible effects of work-hardening. Under the deformation conditions investigated, little evidence of work-hardening was observed. The data follow a power-law dependence on stress, as in previous high-temperature deformation studies. The samples were, however, considerably weaker than predicted by the experimentally determined high-temperature constitutive equation for olivine crystals of this orientation from the study of Bai et al. (1991). The mechanical behavior correlates instead with the weaker of the two mechanisms (flow laws) that contribute to the high-temperature constitutive equation. Thus, our experiments demonstrate that published high-temperature constitutive equations overestimate the strength of lithospheric mantle and that the transition to low-temperature creep occurs at lower temperatures than previously inferred.

Demouchy, Sylvie; Schneider, Stephen E.; Mackwell, Stephen J.; Zimmerman, Mark E.; Kohlstedt, David L.

2009-02-01

221

The effect of water on the electrical conductivity of olivine.  

PubMed

It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%. PMID:17066032

Wang, Duojun; Mookherjee, Mainak; Xu, Yousheng; Karato, Shun-ichiro

2006-10-26

222

Olivine crystals align during diffusion creep of Earth's upper mantle.  

PubMed

The crystallographic preferred orientation (CPO) of olivine produced during dislocation creep is considered to be the primary cause of elastic anisotropy in Earth's upper mantle and is often used to determine the direction of mantle flow. A fundamental question remains, however, as to whether the alignment of olivine crystals is uniquely produced by dislocation creep. Here we report the development of CPO in iron-free olivine (that is, forsterite) during diffusion creep; the intensity and pattern of CPO depend on temperature and the presence of melt, which control the appearance of crystallographic planes on grain boundaries. Grain boundary sliding on these crystallography-controlled boundaries accommodated by diffusion contributes to grain rotation, resulting in a CPO. We show that strong radial anisotropy is anticipated at temperatures corresponding to depths where melting initiates to depths where strongly anisotropic and low seismic velocities are detected. Conversely, weak anisotropy is anticipated at temperatures corresponding to depths where almost isotropic mantle is found. We propose diffusion creep to be the primary means of mantle flow. PMID:24132289

Miyazaki, Tomonori; Sueyoshi, Kenta; Hiraga, Takehiko

2013-10-17

223

Origin of plagioclase-olivine inclusions in carbonaceous chondrites  

SciTech Connect

Plagioclase-Olivine Inclusions (POIs) are an abundant group of chondrule-like objects with igneous textures found in carbonaceous chondrites. POIs consist of plagioclase, olivine, pyroxene, and spinel, and cover a wide range of compositions between Type C Ca-Al-rich Inclusions (CAIs) and ferromagnesian chondrules. POIs are distinguished from CAIs by the absence of melilite, lack of refractory siderophile-rich opaque assemblages, more sodic plagioclase, and abundance of olivine and aluminousenstatite. Rare accessory minerals including armalcolite, zirconolite, rutile, and sapphirine are found in several POIs. The petrographic and chemical properties of POIs indicate that they are not condensates or evaporative residues but formed by melting or partial melting of pre-existing solids. Seven of fourteen POIs contain isotopically fractionated Mg, and despite their textures these POIs are not isotopically homogeneous. A comparison of the essential characteristics of POIs and CAIs suggests that the major processes leading to formation of POIs - including condensation, dust/gas fractionation, aggregation of chemically and isotopically disparate materials, and partial melting - are common to most CAIs and chondrules. We present a scenario for the formulation of these objects and conclude that the homogeneity of the final assemblage - CAI, POI, or chondrule - is primarily a reflection of the thermal history rather than the nature of precursor materials.

Sheng, Y.J.; Hutcheon, I.D.; Wasserburg, G.J. (California Inst. of Tech., Pasadena (USA))

1991-02-01

224

Rheology of olivine and the strength of the lithosphere  

SciTech Connect

In order to throw some light on the rheological behavior of the upper mantle of the Earth, a detailed series of high-temperature deformation experiments has been performed on olivine single crystals at 1 atm pressure under highly controlled thermodynamic conditions. The effects of stress, temperature, oxygen fugacity and orthopyroxene activity on the deformation rate of olivine have been carefully measured for the major high-temperature slip systems. These experimental results have been extrapolated to the pressures and strain rates of the upper mantle to provide new insight into the mechanical behavior of the mantle and a better constrained approach to extrapolation of laboratory deformation data to the conditions present in the upper mantle. The authors suggest that extrapolations in stress provide the most reliable means for extending laboratory creep data to upper mantle strain rates. They also predict that, in the dislocation creep field, the bulk of the strain in olivine in the upper mantle is accommodated by the (010)(100) slip system. In addition, true mantle strengths are probably most accurately modeled using the experimental data for samples oriented favoring the (010)(001) slip system. However, the reliable prediction of mantle strengths requires highly accurate temperature versus depth relationships and good indications of the local oxygen fugacity in the mantle.

Mackwell, S.J. (Pennsylvania State Univ. (USA)); Bai, Q.; Kohlstedt, D.L. (Cornell Univ. (USA))

1990-01-01

225

LA-ICP-MS mapping of olivine from the Brahin and Brenham meteorites: Complex elemental distributions in the pallasite olivine precursor  

NASA Astrophysics Data System (ADS)

To investigate the early history of olivine from the Main-Group pallasites Brahin and Brenham, we have spatially mapped their trace-element distributions using laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS). Brahin olivine interiors contain ˜100-200 ?m patches enriched in Cr, Al, Ti, V, Sc and Ga, separated by linear enrichments of P; these structures bear no relation to current crystal morphologies. Rather, cross-cutting relationships suggest they predate olivine-metal mixing. Brenham olivine also has internal variations for these elements. By contrast, Ni and Co concentrations in olivine from both meteorites decrease near crystal margins, as expected for freezing-in of profiles formed during diffusive re-equilibration with metal during cooling. Brenham olivine also has decreasing Al, Cr and Ti near the margin. Correlations between concentrations of Cr and Al exist for individual Brahin olivine grains, but do not hold over multiple grains, indicating a heterogeneous precursor. Al and Ti are correlated over multiple grains in Brahin, interpreted as Ti cations decorating pre-existing Al-defects. In Brenham olivine, similar geochemical trends exist, but the Cr-Al relationship probably represents both grain margin effects and pre-existing internal heterogeneity. The preservation of structure for elements which are normally fast diffusers in olivine hinges on coupled substitutions involving Al, which along with P diffuses much more slowly than most other elements under some conditions. Al concentrations in olivine are low and variable (3-33 ppm) which is inconsistent with crystallisation from a normal silicate melt; Al-in-olivine thermometers indicate that pallasite olivine was formed in a low-temperature environment. Following its delivery to the magma ocean/core-mantle boundary, Al-P systematics were not substantially modified. Assuming diffusivities for Al and P that are similar to Si (since they reside in the same crystallographic site) and temperatures of 1600-1650 K (from the melting point of the metal and the absence of orthopyroxene in pallasites) an upper limit on the residence time of pallasite olivine of ˜1 Ma can be inferred by the persistence of trace element detail over scales of 100 ?m. Following the olivine-metal mixing event, homogeneous Ni and Co distributions were modified by diffusion; Cr and V were partially modified; Al and P were essentially unchanged.

McKibbin, Seann J.; O'Neill, Hugh St. C.; Mallmann, Guilherme; Halfpenny, Angela

2013-10-01

226

Petrogenesis and Nd-, Pb-, Sr-isotope geochemistry of the Cenozoic olivine melilitites and olivine nephelinites ("ankaratrites") in Madagascar  

NASA Astrophysics Data System (ADS)

The Cenozoic ankaratrites of the Alaotra, Takarindoha-Vatomandry and Votovorona (NE Ankaratra) volcanic fields, Madagascar, range from olivine (± monticellite) melilitites, through olivine-melilite nephelinites to olivine (± leucite) nephelinites. The rocks show significant compositional ranges in their coexisting magmatic minerals (olivine-group minerals, melilite, clinopyroxene, nepheline, leucite, Ba-phlogopite, perovskite, ilmenite, spinels, apatite), and evidence of distinct parental magmas, often in different facies of the same vent. Primitive compositions (high Mg#, Cr and Ni concentrations) are found in each volcanic district, and a few lavas contain mantle xenoliths or xenocrysts. The rocks show enrichment in the most strongly incompatible elements (e.g., Ba and Nb up to 200 times primitive mantle, La/Ybn = 24 to 40), with troughs at K and smooth, decreasing patterns towards the least incompatible elements in mantle-normalized diagrams. The Nd-Pb-Sr isotope geochemistry indicates a marked heterogeneity of the mantle sources of the various districts (e.g., 206Pb/204Pb = 18.68-18.77, 87Sr/86Sr = 0.704011-0.704207 for the Alaotra-Votovorona districts; 206Pb/204Pb = 19.04-19.14, 87Sr/86Sr = 0.703544-0.704017 for the Takarindoha-Vatomandry districts), with significant differences to other Cenozoic mafic volcanic rocks of northern Madagascar. The genesis of the Madagascan ankaratrites is related to rifting events which triggered low-degree partial melting of a garnet peridotite enriched in dolomite and incompatible-element-rich phases, in the lowermost lithosphere. Despite marked geochemical similarities, the source of the Madagascan melilitites bears no isotopic similarity to the HIMU-related sources of melilitites of eastern and southern Africa.

Melluso, Leone; Le Roex, Anton P.; Morra, Vincenzo

2011-12-01

227

Partition of Ni between olivine and sulfide and its application to Ni-Cu sulfide deposits  

Microsoft Academic Search

Equilibration of natural olivine with (Fe, Ni)S in sealed silica glass tubes yields a value for the distribution constant for Ni\\/Fe exchange (KD3) of 27.7±3.5, for 1,200° C, product olivine and sulfide compositions in the ranges 96 to 97 mol% Fo and 15 to 70 mol% NiS, respectively, and run durations of 28 days. Electron microprobe analysis of product olivine

M. E. Fleet; N. D. MacRae

1983-01-01

228

Origins of compositional heterogeneity in olivine-hosted melt inclusions from the Baffin Island picrites  

Microsoft Academic Search

The Baffin Island picrites are highly magnesian (?22 wt% MgO) olivine tholeiites, erupted through felsic continental crust. Plots of most major and minor element oxides against MgO for the lavas define very tight trends consistent with modification of melts parental to the erupted suite by olivine fractionation or accumulation. However, melt inclusions trapped in primitive olivine phenocrysts in these lavas have

Gregory M. Yaxley; Vadim S. Kamenetsky; Maya Kamenetsky; Marc D. Norman; Don Francis

2004-01-01

229

Rheology of San Carlos Olivine at High Pressure and Low Temperature  

Microsoft Academic Search

Olivine, alpha -(Mg,Fe)2SiO4, represents a large fraction of the cold lithospheric material sinking into the mantle in subduction zones. The low-temperature (typically T<800\\\\deg C) olivine rheology, thus, must control the rheology of subducting slabs. Despite its importance, olivine low-temperature rheology is still poorly documented, mainly because of the experimental complications resulting from the high differential yield stress (sigma m) of

P. Raterron; Y. Wu; D. J. Weidner

2001-01-01

230

Phosphorus zoning in olivine of Kilauea Iki lava lake, Hawaii  

NASA Astrophysics Data System (ADS)

Kilauea Iki lava lake was formed when the lavas of the 1959 summit eruption of Kilauea volcano ponded in Kilauea Iki pit crater, as described by [1]. The main chamber of this lake has been drilled repeatedly from 1960 to 1981 as the lake has cooled and crystallized and partial descriptions of core can be found in [2-7]. The bulk of the core consists of a gray, olivine-phyric basalt matrix [3]. Rapid diffusion of divalent cations through olivine at magmatic temperatures can delete information on early-formed zoning and thus information on early magmatic history, recorded in olivine during its growth, is often largely lost [8-11]. In the last years many studies [8-11] have shown that natural olivine, terrestrial and extraterrestrial, from several localities and rock types can preserve a complex zoning in P (sometimes associated with Cr and Al). Simple crystallization experiments conducted by [10] and [11] were able to replicate these features (i.e., sector and oscillatory zoning). Here, we describe P, Cr and Al zoning in olivine from the 1981 drilling of Kilauea Iki lava lake hole #1 (KI81-1) [6]. K? X-ray intensity maps and major and minor element quantitative analyses were obtained using the Caltech JEOL JXA-8200 electron microprobe. We acquired P, Cr, Al, Fe and Ti X-ray maps simultaneously at 15 kV and 400 nA, a beam diameter of 1 ?m, pixel spacing of 1-2 ?m, and count times of 420-1500 msec/step were used depending on the dimension of the crystal. 15 kV and 40 nA with a beam diameter of 1 ?m were used to collect quantitative analyses. P2O5 contents of the Iki olivines range from below detection limit to 0.30 wt%. Zoning in phosphorus, based on X-ray intensity maps, was observed in all olivines we examined. The P zoning patterns of the olivines display several styles. P shows oscillatory zoning comparable to that seen in terrestrial and extraterrestrial igneous olivines and in experimentally grown olivine [8-11]; high P regions, inside the crystals, outline low P chambers and P enriched zones were also observed; near the margins of the crystals is possible to find the presence of discontinuous sets of P-enriched bands that generally outline euhedral crystal forms; some crystals are characterized by P-enriched ghosts of relict crystals in their interior that are associated with probable undercooling and/or with an initial pulse of rapid crystal growth [8, 10]. Phenocrysts and microphenocrysts are frequently unzoned in major and minor divalent cations (Fe, Mg, Mn, Ca, Ni), but all are zoned in P. Variations in Cr and Al correlate spatially with P but are much fainter or absents, in some crystal the P-enriched bands are superimposed with small crystals of chromite (?1 ?m) aligned along the P zoning. Probably these chromites were formed by precipitation from the original Cr and Al bands. In no case was observed Ti zoning. [1] Richter D.H. et al. (1970) US Geol Surv Prof Pap 537-E, 73 p. [2] Richter D.H., Moore J.G. (1966) US Geol Surv Prof Pap 537-B, 26 p. [3] Helz R.T. (1980) Bull Volcanol 43-4, 675-701. [4] Helz R.T. et al. (1984) US Geol Surv Open File Rep 84-484, 72 p. [5] Hardee H.C. et al. (1981) Geophys Res Lett 8, 1211-1214. [6] Helz R.T., Wright T.L. (1983) US Geol Surv Open File Rep 83-326, 66 p. [7] Helz R.T. (1987) Geochem Soc Spec Pub 1, 241-258. [8] Beckett J.R. et al. (2008) LPSC abs. 1726. [9] Mccanta M.C. et al. (2008) LPSC abs. 1807. [10] Milmann-Barris M.S. et al. (2008) CMP 155, 739-765. [11] Mccanta M.C. et al. (2008) GCA 72-12, S1, A610.

Fabbrizio, Alessandro; Beckett, John R.; Baker, Michael B.; Stolper, Edward M.

2010-05-01

231

Olivine/Fe-metal equilibrium under high pressure: an ATEM investigation  

NASA Astrophysics Data System (ADS)

San Carlos olivine samples enclosed in soft iron capsules were annealed in an uniaxial split-sphere apparatus, at pressures ranging from 4.6 to 9.0 GPa and temperature ranging from 1310º to 1595 ºC. We estimated the annealing fO2, theoretically controlled by the olivine/Fe-metal equilibrium, to be 1 to 2 log units above the fO2 of the iron/wustite buffer. Samples were investigated by analytical transmission electron microscopy (ATEM) in order to verify that olivine and Fe capsule did equilibrate during the annealings. TEM imaging of the olivine bulk shows a and c dislocations confined in the (010) plane, and small (0.5 µm) spatially coupled precipitates of (1) Al-rich spinel and (2) enstatite (volumic proportion of precipitates =60 ppm). These coupled precipitates are surrounded by split c dislocation loops. Olivine composition profiles, determined by ATEM near the Fe-capsule/olivine contact, reveal a weak loss of Ni from the olivine matrix toward the capsule, as expected in such reducing conditions. These profiles also reveal a marked incorporation of Fe from the capsule into the olivine matrix. These observations, and their interpretation in terms of olivine point defect chemistry, lead to the following conclusions: (1) the starting olivine contained a high concentration of vacancies on octahedral sites (>=1000 ppm per site); such a high vacancy concentration is expected in San Carlos olivine which equilibrated in nature at relatively high fO2; (2) the olivine/Fe-metal equilibrium did control fO2 during the annealings, that resulted in a rapid re-equilibration of olivine at the beginning of the runs to the lower fO2 imposed by the Fe capsule; this led to a strong decrease of the octahedral vacancy concentration in olivine. (3) Such a fO2 decrease promoted in olivine the coupled precipitation of both types of Al-rich spinel and enstatite precipitates. These observations show that the use of Fe-capsule in high pressure experiments is an efficient method for controlling fO2 when studying olivine, and more generally Fe-bearing silicates.

Raterron, P.; Béjina, F.; Doukhan, J. C.; Jaoul, O.; Liebermann, R. C.

232

Thermochemical stability of low-iron, manganese-enriched olivine in astrophysical environments  

NASA Astrophysics Data System (ADS)

Low-iron, manganese-enriched (LIME) olivine grains are found in cometary samples returned by the Stardust mission from comet 81P/Wild 2. Similar grains are found in primitive meteoritic clasts and unequilibrated meteorite matrix. LIME olivine is thermodynamically stable in a vapor of solar composition at high temperature at total pressures of a millibar to a microbar, but enrichment of solar composition vapor in a dust of chondritic composition causes the FeO/MnO ratio of olivine to increase. The compositions of LIME olivines in primitive materials indicate oxygen fugacities close to those of a very reducing vapor of solar composition. The compositional zoning of LIME olivines in amoeboid olivine aggregates is consistent with equilibration with nebular vapor in the stability field of olivine, without re-equilibration at lower temperatures. A similar history is likely for LIME olivines found in comet samples and in interplanetary dust particles. LIME olivine is not likely to persist in nebular conditions in which silicate liquids are stable.

Ebel, Denton S.; Weisberg, Michael K.; Beckett, John R.

2012-04-01

233

Dependence of Water Solubility in Mantle Olivine on the Silica Activity  

NASA Astrophysics Data System (ADS)

Trace amount of hydrogen stored in nominally anhydrous minerals in the Earth's mantle plays an important role in the dynamics of solid state processes. It may change mineral physical properties such as strength, diffusion and creep rates, electrical conductivity, and transformation kinetics. There have been tremendous efforts to study the incorporation of hydrogen in mantle minerals. However, answers to problems such as incorporation mechanism and solubility of hydrogen in olivine, the most abundant mineral in the upper mantle, remain controversial and somewhat illusive. We present here the results from experimental studies of dependence of hydrogen solubility in olivine on the silica activities, which in turn help our understanding of the incorporation mechanism of hydrogen. Off-line high-pressure experiments were performed on SAM85 press equipped with a DIA module at beamline X17B2 of NSLS at 5-10 GPa and 800 - 1200C. Durations range from one to four hours. Standard cell assembly for DIA was used, each consisting pressure medium of amorphous boron mixed with epoxy, graphite heater, and BN sample capsule. San Carlos olivine was used as starting material. Three layers of sample separated by Pt foil were packed into the capsule, with a fine powder of olivine, a mixture of olivine and orthopyroxene, and a mixture of olivine and periclase in each layer. Several larger grains of olivine (few hundred microns) were embedded in each powder sample. Volatiles were provided by the decomposition of epoxy at high temperature. After experiments samples were cut and double-polished for FTIR analyses, which were conducted at beamline U2A of NSLS. Both powder and single crystal FTIR data revealed the following trend for water solubility in olivine in three samples: olivine + MgO >> olivine > olivine + opx. Water content in olivine in low silica environment (i.e., in sample olivine + MgO) is al least an order of magnitude higher than that equilibrated with high silica activity (i.e., in sample olivine + opx). However, no significant difference among IR patterns in terms of hydroxyl stretching bands for different samples was found, in contrary to findings in some earlier studies. Our results suggest the silica activity may be the dominant factor for water solubility in mantle olivine, and that hydrogen could prefer to enter Si vacancies in olivine.

Allen, K.; Wang, L.; Chen, J.; Weidner, D. J.; Liu, Z.

2004-12-01

234

Origin of graphitic carbon and pentlandite in matrix olivines in the Allende meteorite.  

PubMed

Matrix olivines in the Allende carbonaceous chondrite are believed to have formed by condensation processes in the primitive solar nebula. However, transmission electron microscope observations of numerous matrix olivines show that they contain abundant, previously unrecognized, nanometer-sized inclusions of pentlandite and poorly graphitized carbon. Neither of these phases would have been stable at the high-temperature conditions required to condense iron-rich olivine in the solar nebula. The presence of these inclusions is consistent with formation of the olivines by parent body processes that involved overgrowth of fine-grained organic materials and sulfides in the precursor matrix materials. PMID:10464092

Brearley, A J

1999-08-27

235

Deformation of Olivine at Mantle Pressure using D-DIA  

SciTech Connect

Knowledge of the rheological properties of mantle materials is critical in modeling the dynamics of the Earth. The high-temperature flow law of olivine defined at mantle conditions is especially important since the pressure dependence of rheology may affect our estimation of the strength of olivine in the Earth's interior. In this study, steady-state high-temperature (up to 1473 K) deformation experiments of polycrystalline olivine (average grain size ? 10 ?m) at pressure up to 9.6 GPa, were conducted using a Deformation-DIA (D-DIA) high-pressure apparatus and synchrotron X-ray radiation. The oxygen fugacity (fo2) during the runs was in-between the iron-wustite and the Ni/NiO buffers' fo2. The water content of the polycrystalline samples was generally about 150 to 200 wt. ppm but was as low as 35 wt ppm. Typically, 30 % strain was generated during the uniaxial compression. Sample lengths during the deformation process as well as the differential stresses were monitored in situ by X-ray radiography and diffraction, respectively. The strain rate was derived with an accuracy of 10?6 s?1. Differential stress was measured at constant strain rate (?10?5 s?1) using a multi-element solid-state detector combined with a conical slit. Recovered specimens were investigated by optical and transmission electron microscopy (TEM). TEM shows that dislocation glide was the dominant deformation mechanism throughout the experiment. Evidence of dislocation climb and cross-slip as active mechanisms are also reported. Deformation data show little or no dependence of the dislocation creep flow with pressure, yielding to an activation volume V* of 0 {+-} 5 cm3/mol. These new data are consistent with the high-temperature rheological laws at lower pressures, as reported previously.

Li,L.

2006-01-01

236

Serpentinization of sintered olivine during seawater percolation experiments  

NASA Astrophysics Data System (ADS)

The mantle exposed at slow to ultra-slow spreading ridges is pervasively and variably serpentinized down to depth of 4-8km according to available geophysical data. The onset and durability of this hydration process require efficient penetration and renewal of fluids at the mineral-fluid interface. Moreover, serpentinization is exovolumic if a mass-conservative system is assumed, or chemical elements have to be leached out to conserve rock volume. Thus, the extent of serpentinization depends of the system capacity to create space and/or to drive mass transfers. In order to investigate these coupled hydrodynamic and chemical mechanisms, we did a laboratory experiment during which seawater was injected in a sintered San Carlos olivine sample at conditions representative of low temperature, ultramafic-hosted, hydrothermal systems. The percolation-reaction experiment was carried out at 19 MPa and 190°C; the initial water flow was set at 0.2 mL/h then decreased down to 0.06 mL/h after 8 days. During experiment, permeability decreases continuously although the high Si concentrations in outlet fluids indicate steady olivine dissolution. Fluids are also depleted in Fe and Mg, suggesting precipitation of Fe- and Mg-rich mineral phases. SEM and AEM/TEM analyses of the reacted samples allowed to characterize hematite and poorly crystallized serpentine, both formed at the expanse of olivine. Mass balance calculations indicate that, ca. 8 wt. % olivine was dissolved while the same mass of serpentine (+/- brucite) was formed finally resulting in a porosity decrease from ~ 12% to 5 %. We infer that the structure of the newly formed serpentine resulted in the clogging of fluid paths and explain the decrease of permeability during experiments. Hematite (<1 wt.%) is also observed, indicating redox reactions. We observed that the outlet fluid composition is not modified by changes in the fluid flow. These experimental results are used better understand the scale and efficiency of serpentinization at the onset of the alteration reactions (effective reaction rates in porous/fractured media).

Luquot, L.; Andreani, M.; Godard, M.; Gouze, P.; Gibert, B.

2012-04-01

237

Experimental constraints of the olivine crystals compaction in cumulus layer  

NASA Astrophysics Data System (ADS)

The layered intrusions are the result of magma crystallization and differentiation in a form of lateral structures, which are often observed in magmatic chambers. They are markers of processes occurring during a prolonged cooling stage (several tens of thousands years for bodies 1 km in size). There is no unique explication for the mechanism of layering during the intrusion formation. The most plausible mechanism proposed to explain the observed layering includes the coupled crystal settling and residual liquid advection. In the layers containing a large crystal fraction (> 66 vol%) and a small percentage of the residual liquid, the compaction mechanism and the decrease of cumulate layer porosity due to the diffusion adjustment of grain boundaries could effectively occur. In this study, the compaction mechanisms of crystals settling in magma chambers have been modelled with the use of a high temperature centrifuge. The suspensions of olivine crystals and a basaltic melt (33 vol% and 67 vol%, respectively) were centrifuged at the melting temperature of basalt (temperature range of 1270-1280°C). The experiments were conducted at 200-1500 g under a pressure between 0.8-1.1 GPa. During centrifugation run olivine grains are compacted because of the x-time enhanced centrifugation force which is equivalent to x-time larger volume of crystals compacting from above. After crystals have reached a maximum compaction concentration due to this accelerated piling from above, their locations and porosity in cumulates change under the influence of the solution - recrystallisation process. The concentration of crystals in a cumulate layer increases much slower than during their sedimentation. The solution-precipitation and recrystallisation process is a diffusion type mechanism of compaction and has not been addressed experimentally before. Evidences of the precipitation - recrystallisation process of olivine grains in centrifuged samples with TEM analyses are revealed. In fact, knowing that Ca is characteristic only for MORB-melt, the first feature is the presence of Ca at the interface of two adjacent Ol-grains even when the melt phase is escaped. Another evidence of the diffusion compaction is the presence of some small melt inclusions at the growing Ol-boundaries of compacting Ol-grains. Finally, the precipitation - recrystallisation process of olivine grains during the cumulus compaction stems from the observation that the new boundary between two Ol-grains is distinct and not fully crystallized as the interior of grains. This indicates some MORB melt elements (for example, enrichment in Ca) prevent to recrystallize Ol in a fully crystalline structure.

Forien, M.; Bagdassarov, N.; Schmidt, M. W.

2009-12-01

238

Rheology of San Carlos Olivine at High Pressure and Low Temperature  

NASA Astrophysics Data System (ADS)

Olivine, ? -(Mg,Fe)2SiO4, represents a large fraction of the cold lithospheric material sinking into the mantle in subduction zones. The low-temperature (typically T<800\\deg C) olivine rheology, thus, must control the rheology of subducting slabs. Despite its importance, olivine low-temperature rheology is still poorly documented, mainly because of the experimental complications resulting from the high differential yield stress (? m) of olivine in this range of temperature (e.g., ? m > 5 GPa at T>100 \\deg C, e.g., Evans and Goetze, 1979). At low temperature and low pressure (typically P<300 MPa) only indentation measurements can be performed without breaking apart the specimen. Although several attempts have been made to study the olivine rheology at high pressure, they were until recently either limited to room temperature measurements or inaccurate in the determination of specimen yield stresses and/or strain rates. We report here new results using a new experimental method (see Weidner, 1998) for investigating the low-temperature olivine rheology. San-Carlos olivine rheological properties were studied at high pressure, during relaxation experiments carried out in a large-volume cubic-anvil (SAM85, DIA-type) press, by using in-situ synchrotron X-ray diffraction at the NSLS (Brookhaven, NY) and APS (Argonne, IL) facilities. The olivine elastic strain and strain rate were measured from the broadening of the olivine diffraction peaks. The stress in olivine was deduced from the elastic strain using the olivine elastic constants. Assuming a constant total strain (sum of both the elastic and the plastic strains), a classic assumption for relaxation experiments for which the loading pressure is maintained constant, the olivine plastic strain rate was deduced from the elastic strain rate, ultimately leading to the olivine rheological law at low temperature. The run products were investigated by transmission electron microscopy (TEM) in order to interpret the rheological data in terms of olivine microstructures. We will present these results with particular attention to highlighting the future prospects regarding these new techniques which today allow accurate rheological measurements at high pressure. Evans, B., and Goetze, C. (1979) The temperature variation of hardness of olivine and its implication for polycrystalline Yield stress, J. Geophys. Res., 84: 5,505-5,524. Weidner (1998) Rheological studies at high pressure, in "Ultrahigh-pressure mineralogy: Physics and chemistry of the Earth's deep interior", R. J. Hemley Ed., Reviews in Mineralogy, vol.37, Mineralogical Society of America, Washington D.C., pp.493-524.

Raterron, P.; Wu, Y.; Weidner, D. J.

2001-12-01

239

Mineral replacement rate of olivine by chrysotile and brucite under high alkaline conditions  

NASA Astrophysics Data System (ADS)

Olivine mineral replacement by serpentine is one major alteration reaction of oceanic hydrothermalism. In the present experimental study, olivine grains were replaced by chrysotile and brucite under high alkaline conditions. In our study, olivine replacement implied a spatial and temporal coupling of dissolution and precipitation reactions at the interface between olivine and chrysotile-brucite minerals. Coupled dissolution-precipitation led to the alteration of starting olivine grains (so-called primary or parent mineral) to a porous mineral assemblage of chrysotile and brucite with preservation of the initial olivine morphology. This mineral replacement reaction of olivine (serpentinization) has been characterized using XRD, FESEM and FTIR measurements. Moreover, a simple and novel method is here proposed to quantify the mineral replacement rate (or serpentinization rate) of olivine using thermogravimetric (TG) and differential TG (DTG) analyses. Serpentinization extent depends on the grain size: it is complete after 30 days of reaction for the smallest olivine grains (<30 ?m), after 90 days of reaction for the intermediate olivine grains (30 ?m-56 ?m). For the largest fraction (56-150 ?m), 55% of serpentinization extent was reached after 90 days. Based on the fitting of the serpentinization extent (?t) versus time (t) using a kinetic pseudo-second-order model, the serpentinization rates vary from 3.6×10-6 s-1 to 1.4×10-7 s-1 depending on the olivine grain size. An additional correlation between FTIR spectra analysis and TG measurements is proposed. The mineral replacement reactions frequently observed in natural alteration processes could be a powerful synthesis route to design new porous and/or nanostructured materials.

Lafay, Romain; Montes-Hernandez, German; Janots, Emilie; Chiriac, Rodica; Findling, Nathaniel; Toche, Francois

2012-05-01

240

Development of A-type olivine fabric in water-rich deep upper mantle  

NASA Astrophysics Data System (ADS)

Water controls the activity of slip systems in olivine resulting in various types of olivine crystallographic preferred orientation (i.e., fabric) in mantle rocks. The A-type olivine fabric is the most commonly observed olivine fabric in natural peridotites. Development of A-type olivine fabric (developed by the (010)[100] slip system) is known to be limited to the water-poor conditions of the shallow upper mantle (<200 km depth). We have performed simple-shear deformation experiments of olivine at 7.2-11.1 GPa and 1400-1770 K. Here we show that A-type olivine fabric was developed under water-rich conditions (>2130 ppm H/Si in olivine), while B-type fabric (by the (010)[001] slip system) was observed under moderately wet conditions (750-2130 ppm H/Si). Developments of C-type (by the (100)[001] slip system) fabric was limited to water-poor conditions (<220 ppm H/Si). We found that monotonic decrease in the seismic anisotropy VSH/VSV (the ratio of horizontally and vertically polarized shear waves) with depth in the global one-dimensional models is well explained by the olivine fabrics developed in the horizontal flow of a water-poor mantle. Only A-type olivine fabric can explain the vertical mantle flow which associates the seismic anisotropy of VSH/VSV<1 in the deep upper mantle (>200 km depth). A strong anomaly of VSH/VSV<1 observed in the deep upper mantle beneath the East Pacific Rise is well explained by the distribution of water-rich regions (in which A-type olivine fabric is dominantly developed) in the deep upper mantle and upwelling mantle flows.

Ohuchi, Tomohiro; Irifune, Tetsuo

2013-01-01

241

An experimental investigation into the metastable formation of phosphoran olivine and pyroxene  

NASA Astrophysics Data System (ADS)

The formation of phosphoran olivine by crystallization from a melt was investigated experimentally using a one atmosphere furnace, using San Carlos olivine [(Mg,Fe) 2SiO 4] mixed with either iron phosphide (FeP) or magnesium pyrophosphate (Mg 2P 2O 7). Both dynamic crystallization and isothermal experiments produced phosphoran olivine as zoned single crystals and as overgrowths surrounding normal, phosphorus-free olivine grains. The crystallization pathways that form phosphoran olivine were traced and confirm that it is a metastable phase that can crystallize from a phosphorus-rich melt over timescales of hours to days. Removal of the P and equilibration of the olivine however requires weeks to months in the presence of silicate melt. Phosphoran olivine with up to 27 wt% P 2O 5 was generated and up to 69% of the Si tetrahedral sites were replaced by P. The substitution of Si by P into olivine was confirmed as 4 VIM +2 + 2 IVSi +4 ? 3 VIM +2 + 2 IVP +5 + VI[]. Phosphoran olivine compositions that vary from (Mg,Fe) 2SiO 4 to (Mg,Fe) 1.65[] 0.35Si 0.3P 0.7O 4 have been produced in these experiments. Phosphoran pyroxene was also generated in a few experiments and forms when phosphoran olivine reacts with either tridymite or melt. It has compositions compatible with protopyroxene, orthopyroxene, pigeonite and sub-calcic augite, and can contain up to 31.5 wt% P 2O 5. Like phosphoran olivine, it is also a metastable phase. Phosphorus replaces Si in pyroxene by the following substitution methods: 8 IVSi +4 ? 3 IVSi +4 + 4 IVP +5 + IV[] with Al entering the structure by the exchange 2 IVSi +4 ? IVAl +3 + IVP +5. Phosphoran pyroxene compositions vary from (Mg,Fe) 8Si 8O 24 to (Mg,Fe) 8Si 3P 4[]O 24.

Boesenberg, Joseph S.; Hewins, Roger H.

2010-03-01

242

Partition of noble gases between olivine and basalt melt  

NASA Astrophysics Data System (ADS)

The distribution coefficients ( K i ) of noble gases were determined for synthesized olivine-basalt melt pairs. Seven samples (BH-series) were synthesized at 1370 ~ 1300°C under a one atmospheric pressure (~ 10 5 Pa) noble gas mixture, and four samples (HPP- and HPG-series) at 1360-1050°C at high pressures (0.2-1.5 GPa). The two different experiments gave consistent results with each other. Some BH-series olivine samples were apparently contaminated with gas-rich inclusions or the glass phase, and the effects of such interferences on the calculated distribution coefficients were evaluated. The possible ranges of the distribution coefficients of noble gases thus obtained are: K He 0.07, K Ne = 0.006-0.08, K Ar = 0.05-0.15, K Kr 0.15, and K Xe 0.3. These show remarkable features compared to solid element distribution coefficients: the distribution coefficients of noble gases are rather insensitive to, or even positively correlated with the atomic size of noble gases. The striking contrast between the partition of noble gases and that of solid elements may be attributed to the electrical neutrality of noble gases and the increasing electronic polarizability from He to Xe.

Hiyagon, H.; Ozima, M.

1986-09-01

243

The waveguide effect of metastable olivine in slabs  

NASA Astrophysics Data System (ADS)

We use a finite difference algorithm to compute P-SV synthetic seismograms for deep earthquakes recorded at regional seismic stations located above a subducting slab. We calculate synthetics for 2-D slab models in which the 410 km-discontinuity is uplifted, owing to the exothermic nature of the ? ? ? transition (the equilibrium model), and models in which the 410 km-discontinuity is depressed, owing to inhibited kinetics of the ? ? ? olivine transition (the metastable model). In the latter case the existence of the low-velocity wedge of metastable olivine has a profound influence on the waveforms of deep-focus earthquakes. The wedge acts as a geometrical waveguide, with the energy-focusing effect apparent even after the wavefront has traveled the several hundred kilometers from the wedge boundary to the Earth's surface. The guided energy is most pronounced for receivers located near the surface projection of the deep slab but is observable over a range of 300 km and so may provide a valuable diagnostic for discriminating between equilibrium and metastable models of subduction. A recent search for such guided energy, using regionally recorded P and S waves from deep events in Tonga, yielded negative results.

Koper, Keith D.; Wiens, Douglas A.

244

Olivine-spinel transition and the 400-km discontinuity  

NASA Astrophysics Data System (ADS)

The sequence of high-pressure phase transitions ?-olivine ? ?-modified spinel ? ?-spinel is commonly used as a model for upper mantle seismic velocity increases in the 200-650-km depth interval. The widths of seismic transition zones and the corresponding divariant (e.g., ?+? and ?+?) mineral stability fields are important criteria for correlating velocity variations with phase changes. Divariant mineral stability fields are poorly known for mantle molar Mg/(Mg+Fe) ratios (about 0.9), but C.R. Bina and B.J. Wood of the Department of Geological Sciences, Northwestern University (Evanston, Ill.), have demonstrated that these fields can be constrained by requiring the Mg2SiO4 -Fe2SiO4 phase diagram to be consistent with known thermochemical data. They have derived an internally consistent phase diagram (Figure 1) based on available calorimetric, thermoelastic, and synthetic data. They find that the divariant transition a ? ? + ? ? ? , which is generally regarded as occurring over a broad depth interval, is in fact extremely sharp. For mantle olivine compositions the transition takes place over a pressure interval of only about 2 kbar. The sharpness of this transition, claim the authors, is quite insensitive to uncertainties in the constraining thermodynamic data.

245

Olivine-Hosted Melt Inclusions: Record of High-Pressure or Late-Stage Processes?  

Microsoft Academic Search

Melt inclusions in olivine have been thought to be high fidelity recorders of equilibrium melt compositions for incompatible trace elements because partition coefficients are very low, and incompatible elements are very large atoms that do not substitute in the olivine structure. This view has recently been shaken by the Spandler et al. (Nature, 2007) results on very fast REE diffusion

M. Laubier; C. H. Langmuir

2007-01-01

246

Evolution of olivine lattice preferred orientation during simple shear in the mantle  

Microsoft Academic Search

Understanding the variation of olivine lattice preferred orientation (LPO) as a function of shear strain is important for models that relate seismic anisotropy to the kinematics of deformation. We present results on the evolution of olivine orientation as a function of shear strain in samples from a shear zone in the Josephine Peridotite (southwest Oregon). We find that the LPO

Jessica M. Warren; Greg Hirth; Peter B. Kelemen

2008-01-01

247

Hydrous olivine unable to account for conductivity anomaly at the top of the asthenosphere.  

PubMed

The oceanic asthenosphere is observed to have high electrical conductivity, which is highly anisotropic in some locations. In the directions parallel and normal to the plate motion, the conductivity is of the order of 10(-1) and 10(-2) S m(-1), respectively, which cannot be explained by the conductivity of anhydrous olivine. But because hydrogen can be incorporated in olivine at mantle pressures, this observation has been attributed to olivine hydration, which might cause anisotropically high conductivity by proton migration. To examine this hypothesis, here we report the effect of water on electrical conductivity and its anisotropy for hydrogen-doped and undoped olivine at 500-1,500 K and 3 GPa. The hydrous olivine has much higher conductivity and lower activation energy than anhydrous olivine in the investigated temperature range. Nevertheless, extrapolation of the experimental results suggests that conductivity of hydrous olivine at the top of the asthenosphere should be nearly isotropic and only of the order of 10(-2) S m(-1). Our data indicate that the hydration of olivine cannot account for the geophysical observations, which instead may be explained by the presence of partial melt elongated in the direction of plate motion. PMID:17066031

Yoshino, Takashi; Matsuzaki, Takuya; Yamashita, Shigeru; Katsura, Tomoo

2006-10-26

248

Catalytic decomposition of biomass tars: use of dolomite and untreated olivine  

Microsoft Academic Search

Although biomass is getting increased attention as a renewable energy source, one of the remaining problems still to be solved is the reduction of the high level of tar present in the product gas from gasification of biomass. The purpose of the present work is to study the activity of olivine and dolomite for tar destruction. Some researchers investigated olivine

Lopamudra Devi; Krzysztof J. Ptasinski; Frans J. J. G. Janssen; Sander V. B. van Paasen; Patrick C. A. Bergman; Jacob H. A. Kiel

2005-01-01

249

Effects of water and iron content on the rheological contrast between garnet and olivine  

NASA Astrophysics Data System (ADS)

The effects of water and iron content on the relative creep strengths of garnet and olivine were investigated by shear deformation experiments. Garnet and olivine samples were sandwiched together between alumina pistons in a simple shear geometry and were deformed at P = 1-2 GPa, T = 1473 K and strain rates ranging from 10 -5 to 10 -3 s -1 using a Griggs-type solid-medium apparatus. The stress- and strain-rate relation, as well as the deformation microstructures including lattice-preferred orientation and dynamic recrystallization, indicates that the deformation by dislocation creep. The creep tests show that the Fe-rich garnet (Alm 67Prp 29Grs 3) was slightly weaker than olivine (Fo90), whereas the Mg-rich garnet (Alm 19Prp 68Grs 12) was significantly stronger than olivine under dry conditions. The wet experiments show that the creep rate of the Mg-rich garnet is more sensitive to water than olivine; the water fugacity exponent on strain rate was estimated to be ˜2.4 for garnet and ˜1.2 for olivine, and the Mg-rich garnet becomes weaker than olivine in a water-rich environment. The experimental results show that the rheological contrast between garnet and olivine depends strongly on water content and to a lesser degree on Fe content. Consequently, the geodynamic behavior of geochemical reservoirs can be sensitive to their chemical environments in the upper mantle.

Katayama, Ikuo; Karato, Shun-Ichiro

2008-01-01

250

Remote Compositional Analyses of Lunar Olivine-rich Lithologies Using Moon Mineralogy Mapper (M3) Data  

Microsoft Academic Search

We have applied techniques developed for laboratory spectra of lunar olivines to spectra collected by M3. Our work suggests that the olivines analyzed to date are more Fe-rich than those in primitive Mg-suite rocks from the Apollo collection.

P. J. Isaacson; C. M. Pieters; R. N. Clark; J. W. Head; R. L. Klima; N. E. Petro; M. I. Staid; J. M. Sunshine; L. A. Taylor; K. G. Thaisen; S. Tompkins

2010-01-01

251

FTIR spectroscopy of OH in olivine: A new tool in kimberlite exploration  

NASA Astrophysics Data System (ADS)

Our study of olivines from Canadian kimberlites shows that the application of FTIR spectroscopy significantly improves the reliability of olivine as a kimberlite indicator mineral (KIM). We have developed an algorithm that yields the water concentration and the normalized intensity of the OH IR absorption band at 3572 cm -1 from unpolished olivine grains of unknown thickness. For 80% of kimberlitic olivines these two parameters are significantly higher than those for olivines from non-kimberlitic magmas and consequently, olivines with water concentrations >60 ppm and a strong absorption band at 3572 cm -1 can be reliably classified as being kimberlitic. We have identified two major spectral features in the OH absorption bands of kimberlitic olivines that allow for a more detailed classification: (a) the presence of three types of high-requency OH absorption bands (Group 1A, 1B and 1C) and (b) the proportion of low-frequency OH absorption bands (Group 2) relative to high-frequency bands (Group 1). Comparison of our results with experimental studies suggests that differences within Group 1 OH absorption bands are due to different pressures of crystallization or hydrogenation. The three identified types of Group 1 OH absorption bands approximately correspond to high ( P > 2 GPa, Group 1A), moderate (2-1 GPa, Group 1B), and low (<1 GPa, Group 1C) pressures of hydrogenation. Group 2 OH IR absorption bands in olivines with NiO > 3500 ppm are interpreted to reflect olivine-orthopyroxene equilibria and hence are indicative of xenocrystic olivine derived from lherzolitic or harzburgitic mantle sources. Interaction of xenocrystic olivine with hydrous kimberlitic melts with low silica activity likely will cause a gradual increase in Group 1 absorption bands. Therefore, FTIR spectra of olivine can be used to obtain qualitative estimates of the duration of interaction between mantle material and a kimberlitic melt. In addition to applications in kimberlite and diamond exploration, FTIR spectra of olivine phenocrysts, combined with mineral chemical data, may also provide insights into kimberlite evolution. Our data suggest that in some instances the ascent of kimberlitic magmas could have been interrupted at or near the Moho, followed by olivine crystallization and exsolution of aqueous fluids.

Matveev, S.; Stachel, T.

2007-11-01

252

Systematics of Ni and Co partitioning between olivine and peridotitic liquids  

NASA Astrophysics Data System (ADS)

We have measured olivine/liquid partition coefficients (D) for Ni and Co in runs from 1550 to 2015° C and 1.5 to 6 GPa. D values (weight units) range from 7.2 to 1.4 for Ni and 2.0 to 0.9 for Co. The Ds correlate weakly with 1/T and P/T, but well with D/*(MgO) in accordance with the Jones'95 model (D/*MO = aD/*MgO +b, where D/* is the partition coefficient expressed in cation mole fraction, M is a divalent cation, and a and b are constants). Our experiments have D/*MgO in the range of 2.4 to 1.4. The model predicts that Ni and Co will become incompatible (D>1) for values of D/*MgO < 1.39 and 1.76, respectively, which correspond to peridotitic and komatiitic compositions. Calculations of the fractional crystallization of a lunar magma ocean with bulk composition similar to a degassed terrestrial upper mantle and an initial bottom pressure of 3.0 GPa show that both Ni and Co are initially incompatible, but that Ni becomes compatible after 10/% crystallization and Co after about 40/%. Ni in olivine has a prominent peak at intermediate fractions of crystallization; whereas Co in olivine in creases monotonically until the very latest stages. The patterns of Ni and Co concentration calculated in magma ocean olivine mimic patterns in observed in lunar rocks: olivines for the Mg-suite have the highest Mg/#s, but relatively low Ni; mare basalts have less magnesian olivine but much higher Ni in olivine, and ferroan anorthosites have olivines with lower Mg/# still, but also low Ni. Co is also low in the most magnesian olivines, but olivines from ferroan anorthosites have Co concentrations similar to olivine in mare basalts, so the overall pattern is a monotonic increase of Co as Mg/# decreases. Within the mare basalt series the expected pattern of Ni and Co concentrations in olivine decreasing as Mg/# decreases is observed. So the apparently anomalous behavior of Ni and Co can only be explained by crystallization of a magma ocean in which accumulation of the earliest olivines contributed to the formation of the Mg-suite source region, accumulation of intermediate olivine cumulates led to the formation of the mare basalts, and in the later stages ferroan anorthosites formed either directly in the magma ocean or their source regions did.

Longhi, J.; Walker, D.; Durand, S.

2006-12-01

253

The Mn-Fe negative correlation in olivines in ALHA 77257 ureilite  

NASA Astrophysics Data System (ADS)

An electron probe microanalyzer is used to measure the Mn, Fe, and oxygen zoning profiles of olivines in the ALHA 77257 ureilite. This is done to study the effects of reduction on the Mn-Fe value, as ureilite olivines exhibit thin reduced rims. Since the Mn content gradually increases toward the rim of ureilite olivines, while the Fa (= 100 x Fe/(Mg + Fe), mol percent) component decreases, the Mn-Fe content of olivine is likely related to redox conditions. The results of melting experiments suggest that the Mn-Fe positive correlation is related to temperature and that the negative correlation of Mn-Fe in olivine and low-Ca pyroxene is related to reduction.

Miyamoto, M.; Furuta, T.; Fujii, N.; McKay, D. S.; Lofgren, G. E.; Duke, M. B.

1993-03-01

254

Remote compositional analysis of lunar olivine-rich lithologies with Moon Mineralogy Mapper (M3) spectra  

NASA Astrophysics Data System (ADS)

A systematic approach for deconvolving remotely sensed lunar olivine-rich visible to near-infrared (VNIR) reflectance spectra with the Modified Gaussian Model (MGM) is evaluated with Chandrayaan-1 Moon Mineralogy Mapper (M3) spectra. Whereas earlier studies of laboratory reflectance spectra focused only on complications due to chromite inclusions in lunar olivines, we develop a systematic approach for addressing (through continuum removal) the prominent continuum slopes common to remotely sensed reflectance spectra of planetary surfaces. We have validated our continuum removal on a suite of laboratory reflectance spectra. Suites of olivine-dominated reflectance spectra from a small crater near Mare Moscoviense, the Copernicus central peak, Aristarchus, and the crater Marius in the Marius Hills were analyzed. Spectral diversity was detected in visual evaluation of the spectra and was quantified using the MGM. The MGM-derived band positions are used to estimate the olivine's composition in a relative sense. Spectra of olivines from Moscoviense exhibit diversity in their absorption features, and this diversity suggests some variation in olivine Fe/Mg content. Olivines from Copernicus are observed to be spectrally homogeneous and thus are predicted to be more compositionally homogeneous than those at Moscoviense but are of broadly similar composition to the Moscoviense olivines. Olivines from Aristarchus and Marius exhibit clear spectral differences from those at Moscoviense and Copernicus but also exhibit features that suggest contributions from other phases. If the various precautions discussed here are weighed carefully, the methods presented here can be used to make general predictions of absolute olivine composition (Fe/Mg content).

Isaacson, Peter J.; Pieters, Carle M.; Besse, Sebastien; Clark, Roger N.; Head, James W.; Klima, Rachel L.; Mustard, John F.; Petro, Noah E.; Staid, Matthew I.; Sunshine, Jessica M.; Taylor, Lawrence A.; Thaisen, Kevin G.; Tompkins, Stefanie

2011-04-01

255

Extended planar defects and the rapid incorporation of Ti4+ into olivine  

NASA Astrophysics Data System (ADS)

The formation of extended planar defects in minerals such as olivine is related to high point defect concentration and can be driven by large gradients in chemical potential, where the energy of the system is lowered by the ordering of defects along specific planes in the crystal. The presence of extended defects has the potential to create the (apparently) anomalous ionic diffusion in olivine as reported recently (Spandler and O'Neill in Contrib Mineral Petrol 159(6):791-818, 2010). High-resolution transmission electron microscopy and energy-filtered imaging were done using experimental samples designed to examine the impact of a TiO2 and f O2 on the potential to form such defects in ferromagnesian olivine. Doped basalt (5 wt% TiO2)-olivine reaction couple experiments were run at 1 atm and 1,310 and 1,410 °C for 50 h at various f O2, ranging from 102 below to 102 above the quartz-fayalite-magnetite buffer. Our results show that extended planar defects in olivine, parallel to {101}ol and occurring in ordered "clusters" with a prolate spheroid geometry 5-25 nm across and extending up to 150 nm into the olivine, are present near the olivine-glass interfaces in all of our experimental high-TiO2 basalt-olivine samples. Increased Ti content in the olivine is associated with the defects; ordering of Ti4+ and octahedral site vacancies leads to a two- or three-layer superstructure in the olivine. Defect nucleation and growth is driven by the large TiO2 chemical potential gradient across the phase boundary at the start of the experiments, which provides access to microstructures not otherwise present.

Burgess, Katherine D.; Cooper, Reid F.

2013-10-01

256

Martian Dunite NWA 2737: Petrographic Constraints on Geological History, Shock Events, and Olivine Color  

SciTech Connect

Meteorite Northwest Africa (NWA) 2737 is the second known chassignite, an olivine-rich igneous rock with mineral compositions and isotopic ratios that suggest it formed on Mars. NWA 2737 consists of ?85% vol. olivine (Mg, molar Mg/(Mg + Fe), of 78.3 {+-} 0.4%), which is notable because it is black in hand sample and brown in thin section. Other minerals include chromite, pyroxenes (augite, pigeonite, orthopyroxene), and diaplectic glass of alkali-feldspar composition. Aqueous alteration is minimal and appears only as slight dissolution of glass. NWA 2737 formed by accumulation of olivine and chromite from a basaltic magma; the other minerals represent magma trapped among the cumulus grains. Minerals are compositionally homogeneous, consistent with chemical equilibration in late and postigneous cooling. Two-pyroxene thermometry gives equilibration temperatures 1150 C, implying a significant time spent at the basalt solidus. Olivine-spinel-pyroxene equilibria give ?825 C (possibly the T of mesostasis crystallization) at an oxidation state of QMF-1. This oxidation state is consistent with low Fe3+ in olivine (determined by EMP, Moessbauer spectra, and synchrotron micro-XANES spectroscopy) and with {approx}10% of the iron in pyroxene being Fe3+. NWA 2737 experienced two shock events. The first shock, to stage S5-S6, affected the olivine by producing in it planar deformation features, intense mosaicism and lattice strain, and abundant droplets of iron-nickel metal, 5-15 nm in diameter. At this stage the olivine became deeply colored, i.e., strongly absorbing at visible and near-infrared (NIR) wavelengths. This shock event and its thermal pulse probably occurred at {approx}170 Ma, the Ar-Ar age of NWA 2737. The colored olivine is cut by ribbons of coarser, uncolored olivine with long axes along [100] and shorter axes on {l_brace}021{r_brace} planes: These are consistent with the easy slip law for olivine [100]{l_brace}021{r_brace}, which is activated at moderate strain rate at high temperature. Within these ribbons the olivine was coarsened and the iron metal globules coalesced to micron-sized grains. The ribbons also are mosaicized and cut by planar fractures, which bespeak a second shock event, possibly that of ejection from Mars. The deeply colored olivine in NWA 2737 is unusual and represents a new 'ground truth' type for remote sensing of Mars. Understanding the occurrence of the brown color in olivine in NWA 2737 places important constraints on interpretation of optical measurements.

Treiman,A.; Dyar, M.; McCanta, M.; Noble, S.; Pieters, C.

2007-01-01

257

Hydrogen in the upper mantle: Diffusion and effects on olivine transformation kinetics  

NASA Astrophysics Data System (ADS)

Olivine is the most abundant mineral in Earth's upper mantle and can host significant amounts of hydrogen within its crystal structure. The presence of hydrogen affects many of olivine's physical properties such as electrical conductivity, viscosity, sound speed, transformation kinetics, phase equilibrium, and generally speaking the physics governing the interior of the earth. Understanding how hydrogen affects olivine is integral to understanding the Earth's interior. In this work olivine was experimentally hydrated and reacted at high pressure and temperature, to simulate upper mantle conditions. The physical properties measured in this work are used to understand seismic and magnetotelluric observations of the Earth. In the first project the effects of hydrogen on olivine transformation kinetics were examined. Growth rates for olivine's high pressure polymorphs, wadsleyite and ringwoodite, to determine if olivine can persist metastably inside cold subducting slabs in the mantle transition zone. Hydrogen significantly enhances the growth rates of olivine into ringwoodite. For olivine containing ˜75 (or higher) ppmw H2O At 18 GPa and 900°C the growth rate for ringwoodite rims is 1.0x10-9 m/s with activation enthalpy of 235 +/- 30 kJ/mol, which is too high for persistence of metastable olivine into the transition zone. Confirmation of the existence of metastable olivine by seismologists would constrain H2O contents at such locations to be < 75 ppmw H2O. In the second project deuterium-hydrogen interdiffusion coefficients were measured to help understand electrical conductivity, point defect populations, chemical transport, and defect dominated properties in olivine. For the fastest H-diffusing [100] orientation DD-H, [100] = 10(-5.04 +/- 1.43)*e(-137 +/- 31 kJ/mol)/(RT) m²/s at 2 GPa and 750--900°C. Comparison of DD-H to chemical diffusion coefficients allows us to calculate diffusivity of intrinsic defects. Olivine electrical conductivity is calculated from DD-H using the Nernst-Einstein relation. These results combined with geophysical electrical conductivity depth profiles permit first order calculations of H2O contents in the upper mantle and suggest that the hydrogen contribution to electrical conductivity is too small to account for high electrical conductivity anomalies in the asthenosphere.

Du Frane, Wyatt Louis

258

Shear Attenuation and Dispersion in Olivine + Orthopyroxene Aggregates (Synthetic Harzburgite)  

NASA Astrophysics Data System (ADS)

Low-frequency (10-2.25olivine (ol) and orthopyroxene (opx). The attenuation spectra reveal “high-temperature background” behavior where attenuation diminishes smoothly and mildly with increasing frequency (QG-1~f -0.3). At higher frequencies (f >10-0.5 Hz), the attenuation spectra reveal the onset of an apparent peak, likely due to elastically-accommodated grain boundary sliding. Most importantly, these experiments reveal a strong dependence of attenuation on the modal abundance of opx for constant frequency, temperature, grain size, and melt fraction: attenuation increases by roughly a factor of two as the modal abundance of opx rises from 6 to 54 vol%. Further addition of opx leads to diminished attenuation. These reciprocating torsion measurements were complemented by a series of unidirectional microcreep tests, which demonstrate that the variation in attenuation is complemented by both a lower shear viscosity and a drop in the activation energy as opx mode increases. The behavior suggests that: (1) phase boundaries are potent absorbers of mechanical energy, and (2) the background attenuation in dry, melt-free upper mantle may be larger than that predicted from experimental studies conducted on single-phase olivine aggregates. The implications of these results for understanding seismic signatures of mid-ocean ridges and subduction zones are discussed.

Sundberg, M. I.; Cooper, R. F.

2009-12-01

259

Olivine friction at the base of oceanic seismogenic zones  

USGS Publications Warehouse

We investigate the strength and frictional behavior of olivine aggregates at temperatures and effective confining pressures similar to those at the base of the seismogenic zone on a typical ridge transform fault. Triaxial compression tests were conducted on dry olivine powder (grain size ???60 ??m) at effective confining pressures between 50 and 300 MPa (using Argon as a pore fluid), temperatures between 600??C and 1000??C, and axial displacement rates from 0.06 to 60 ??m/s (axial strain rates from 3 ?? 10-6 to 3 ?? 10-3 s-1). Yielding shows a negative pressure dependence, consistent with predictions for shear enhanced compaction and with the observation that samples exhibit compaction during the initial stages of the experiments. A combination of mechanical data and microstructural observations demonstrate that deformation was accommodated by frictional processes. Sample strengths were pressure-dependent and nearly independent of temperature. Localized shear zones formed in initially homogeneous aggregates early in the experiments. The frictional response to changes in loading rate is well described by rate and state constitutive laws, with a transition from velocity-weakening to velocity-strengthening at 1000??C. Microstructural observations and physical models indicate that plastic yielding of asperities at high temperatures and low axial strain rates stabilizes frictional sliding. Extrapolation of our experimental data to geologic strain rates indicates that a transition from velocity weakening to velocity strengthening occurs at approximately 600??C, consistent with the focal depths of earthquakes in the oceanic lithosphere. Copyright 2007 by the American Geophysical Union.

Boettcher, M. S.; Hirth, G.; Evans, B.

2007-01-01

260

Electrical conductivity of olivine, a dunite, and the mantle  

SciTech Connect

Laboratory studies of the electrical conductivity of rocks and minerals are vital to the interpretation of electromagnetic soundings of the Earth's mantle. To date, the most reliable data have been collected from single crystals. The authors have extended these studies with electrical conductivity measurements on a dunite from North Carolina, in the temperature range of 600-1,200 C and under controlled oxygen fugacity. Observations of conductivity as a function of oxygen fugacity and temperature demonstrate that conduction in the dunite is indistinguishable from conduction in single olivine crystals. Thus the common practice of exaggerating the single-crystal conductivities to account for conduction by grain boundary phases in the mantle is unnecessary. Because the dunite conductivity is consistent with that published for single crystals under similar conditions, the authors have made a combined analysis of these data. Conductivity as a function of temperature between 600 and 1,450 C displays three conduction mechanisms whose activation energies may be recovered by nonlinear least squares fitting, yielding activation energies of 0.21 {plus minus} 2.56 {times} 10{sup {minus}19} J below 720 C, 2.56 {plus minus} 0.02 {times} 10{sup {minus}19} J between 720 C and 1,500 C and 11.46 {plus minus} 0.90 {times} 10{sup {minus}19} J above 1,500 C. The behavior of conductivity as a function of oxygen fugacity is well explained by a model in which an f{sub O{sub 2}}-independent population of charge carriers is supplemented at high oxygen fugacities with a population that is proportional to f{sub O{sub 2}}{sup 0.3}. This parametrization produces a clear correlation of the f{sub O{sub 2}} dependent term with iron content, which is otherwise obscured by variations in conductivity among olivines.

Constable, S. (Scripps Inst. of Oceanography, La Jolla, CA (United States)); Duba, A. (Lawrence Livermore National Lab., CA (United States))

1990-05-10

261

Deformation of dry Olivine up to 11 GPa and 2100 K Using a Rotational Drickamer Apparatus  

NASA Astrophysics Data System (ADS)

Characterizing the pressure effects on plastic deformation of olivine is important for understanding mantle dynamics and evolution of the Earth. Although many experimental studies have been performed on olivine deformation, the magnitude of the pressure effects (activation volume, V*) remain controversial. We use the rotational Drickamer apparatus (RDA) to determine the pressure dependence of creep strength of olivine in the dislocation creep regime. Deformation experiments on dry hot-pressed polycrystalline San Carlos olivine have been conducted at 6-11 GPa, 1500-2100 K and strain rates of 0.9-7.4 × 10-5 s-1 using the RDA at X17B2, Brookhaven National Laboratory. Shear deformation experiments up to the strain of 0.45 were performed. Near steady-state deformation was observed after the shear strain of 0.04-0.24. The stress was measured from the dependence of lattice spacing on the orientation for (130), (131), (112), (122), (140), (211) and (241) planes, as well as dislocation densities. We found that (i) the strength of olivine at steady-state deformation at these pressures is much larger than those at lower pressures, (ii) the variation of stress values inferred from different lattice planes decreases with temperature. We conclude that the creep strength of olivine for dislocation creep increases significantly with pressure and that the plastic anisotropy in olivine decreases with temperature.

Kawazoe, T.; Otsuka, K.; Tinker, D.; Karato, S.; Nishihara, Y.; Jing, Z.; Mookherjee, M.

2007-12-01

262

Variable Olivine Detection in Soils at Meridiani Planum From Mars Express OMEGA and MER Opportunity Observations  

NASA Astrophysics Data System (ADS)

The Meridiani plains have been characterized spectrally using data collected on the ground by the Opportunity rover and from orbit by the Mars Express OMEGA instrument. Observations completed by the Opportunity rover show that the Meridiani plains are covered by aeolian deposits composed of basaltic sands, gray hematite spherules, and variable amounts of bright dust. Measurements made by the Mössbauer spectrometer (14.4keV) of the deposits imply subequal concentrations of iron contained in both olivine and pyroxene [Klingelhöfer et al., 2004] whereas Mini-TES (5-29?m) detects a higher abundance of pyroxene relative to olivine [Christensen et al., 2004]. Distinct spectral features attributable to olivine or pyroxene in the ~0.4-1?m range are not detectable in Pancam data [Bell et al., 2004]. Spectral reflectance data from OMEGA (in the ~0.92-2.69?m range) covering the Opportunity rover traverse regions show evidence for the presence of pyroxene but not olivine, although olivine has been detected several kilometers to the south [Arvidson et al., 2006]. The apparent discrepancy in the concentration of olivine detected by the various instruments at Meridiani suggests that olivine is masked by the presence of other phases in the VNIR.

Wiseman, S. M.; Arvidson, R. E.; Poulet, F.; Morris, R. V.; Ming, D. W.

2006-05-01

263

The influence of water on the Peierls stress of olivine at high pressures  

NASA Astrophysics Data System (ADS)

To investigate the influence of water on the low-temperature plasticity of olivine under lithospheric conditions, we carried out a series of creep experiments on polycrystalline olivine at high pressures (~6 GPa), relatively low temperatures (873 ? T ? 1173 K), and hydrous conditions using a deformation-DIA. Samples were fabricated from fine powdered San Carlos olivine under hydrous conditions. In the experiments, a sample column composed of a sample and alumina pistons was assembled with a talc sleeve and graphite resistance heater into a 6.2-mm edge length cubic pressure medium. Experiments were carried out at the National Synchrotron Light Source at Brookhaven National Laboratory. In a run, differential stress and sample displacement were monitored in-situ using synchrotron x-ray diffraction and radiography, respectively. The low-temperature plasticity of olivine under hydrous conditions is constrained by our data with a Peierls stress of 4.2 ± 0.3 GPa. This value is much lower than those reported the Peierls stress for olivine under anhydrous conditions (~ 6 - 15 GPa, Evans and Goetze, 1979; Raterron et al., 2004; Mei at al., 2010), indicating a significant influence of water on the low-temperature plasticity of olivine. The low-temperature flow behavior of olivine under hydrous conditions quantified in this study provides a necessary constraint for modeling the dynamic activities occurring within lithospheric mantle especially for those regions with the presence of water such as beneath a mid-ocean ridge and along a subducting slab.

Mei, S.; Suzuki, A. M.; Xu, L.; Kohlstedt, D. L.; Dixon, N. A.; Durham, W. B.

2012-04-01

264

Granoblastic olivine aggregates as precursors of Type I chondrules: An experimental test  

NASA Astrophysics Data System (ADS)

Chondrule formation models involving precursors of granoblastic olivine aggregates (GOA) of either planetesimal or nebular origin have recently been proposed. We have therefore conducted chondrule simulation experiments using mixtures of 100 h-thermally annealed GOA and An + En to test the viability of GOA as predecessors of porphyritic olivine (PO) chondrules. Isothermal runs of less than 5 min at 1350-1550 °C result in GOA disaggregation and Fe-Mg exchange; runs of 0.5-4 h show textures superficially similar to granular and PO chondrules, but with reversely zoned olivine. Charges isothermally heated at 1550 °C for 1 and 4 h before being cooled at 10 and 100 °C/h undergo olivine crystallization and yield classical PO textures. Although most evidence of origin from GOA is erased, the cores of normally zoned euhedral crystals are relict. As 'phenocrysts' in Type I chondrules can be relict such chondrules could have experienced similar peak temperatures to those of Type II chondrules. Chondrules containing GOA with olivine triple junctions resemble experimental charges heated for minutes at temperatures between 1350 and 1450 °C and Type I chondrules with subhedral to anhedral olivine plus GOA relicts resemble charges heated at the same temperatures but for longer duration. Type I chondrules with a mass of granular olivine or irregular, anhedral olivine grains in the center, and much glass nearer the margin, on the other hand, require limited heating at high temperature (1550 °C) while Type I chondrules with euhedral olivines, resemble charges heated at 1550 °C for 4 h. The majority of Type I chondrules in CV chondrites display evidence of derivation from GOA. Many finer-grained chondrules in CR and UOC on the other hand, could not have been derived from such coarse-grained precursors, but could have formed from fine-grained dustballs as stipulated in the standard paradigm. Thus, both GOA and dustballs represent viable chondrule precursors of coarser and finer-grained Type I PO chondrules, respectively.

Whattam, Scott A.; Hewins, Roger H.

2009-09-01

265

Minor and trace elements in olivines as probes into early igneous and mantle melting processes  

NASA Astrophysics Data System (ADS)

The trace element composition of olivine is a rapidly growing research area that has several applications of great potential. Mantle olivines can be distinguished from volcanic olivines by lower concentrations of Ca (<700 ppm), Ti (<70 ppm), and often Cr. The melting of pyroxenites derived from recycled ocean crust can be recognized in volcanic olivines by correlations of Mn, Al, Sc and Co in addition to Ni. High Ni is characteristic of olivine derived from olivine-free source rocks, but alone it does not distinguish between recycling of ocean crust, continental crust, mantle wedge hybridization, and intra-mantle melt migration. Trace elements help to identify different types of non-peridotitic ultramafic rocks, including those not formed by ocean crust recycling. High Li may be caused by recycling of continental crust, as in Mediterranean post-collisional volcanics or by interaction with carbonatitic melts, and correlation with further elements such as Zn, Na, Ti and Ca will help to identify minerals in the source assemblages, such as phlogopite, spinel, garnet, amphiboles and carbonates, and thus the source of the olivine-free assemblages. Olivines often store the earliest chemical signals of melt loss in peridotites, but later absorb trace elements from passing melts, and are thus excellent monitors of the chemistry of metasomatic agents. Trace elements distinguish between Ti-enrichment by silicate melt metasomatism (high Ti, low Ca) and high-Ca signatures associated with plumes and rift regions that may be due to carbonate-silicate melts. Li may be enriched in olivine in the orogenic mantle, indicating the involvement of melted continental crustal material. Experimental data on element partitioning and diffusion currently partly conflicts with information from natural rocks.

Foley, Stephen F.; Prelevic, Dejan; Rehfeldt, Tatjana; Jacob, Dorrit E.

2013-02-01

266

Oriented chromite-diopside symplectic inclusions in olivine from lunar regolith delivered by "Luna-24" mission  

NASA Astrophysics Data System (ADS)

Calcium-chromium rich lamellae in olivine grain No. 1611 from the Luna-24 regolith were studied with FEG-EMPA and TEM. The lamellae consist of a worm-like intergrowth of FeCr2O4 chromite (Chr) and CaMgSi2O6 diopside (Di), with a Chr:Di modal proportion of 1:3. The linear extension of the lamellae and crystallographic orientation relationships among the symplectite phases and the olivine suggest that the lamellae nucleated at deformation defects in the olivine host. Calcium depletion haloes surrounding the lamellae amount to about 75 ?m and indicate that the chromite + diopside lamellae were formed by segregation of calcium and chromium from the host olivine into the lamellae without addition of calcium and/or chromium from outside the olivine. The segregation of calcium and chromium and, consequently, the growth of the symplectic lamellae were diffusion-controlled. The segregation of a calcium-chromium component from the host olivine was associated with oxidation of divalent to trivalent chromium. Oxidation was facilitated by dehydrogenation, which was driven by decompression and/or a change in redox potential. Hydrogen point defects in the original olivine with H+ substituting for divalent cations on the M-sites provided the necessary electron acceptors for the oxidation of chromium and after electron transfer left olivine as molecular H2. The internal microstructure of the lamellae suggests that exsolution of the calcium-chromium rich lamellae from the host olivine and formation of the chromite-diopside symplectic intergrowth occurred simultaneously. The time scale derived from diffusion modeling of the calcium depletion haloes around the lamellae indicates a thermal event on the order of several months to several hundred years at most. Symplectic inclusions found in olivine from lunar, martian and terrestrial rocks are similar with respect to their shape, crystallographic orientation relationships, and internal microstructure of the spinel-clinopyroxene intergrowth. These features are inconsistent with "dry" olivine oxidation that is by the uptake of oxygen. Dehydrogenation of OH-bearing precursor olivine is suggested as a general mechanism of oxidation accompanied by chemical segregation and phase separation resulting in symplectite formation.

Khisina, N. R.; Wirth, R.; Abart, R.; Rhede, D.; Heinrich, W.

2013-03-01

267

Serpentinization of oceanic peridotites: 2. Kinetics and processes of San Carlos olivine hydrothermal alteration  

NASA Astrophysics Data System (ADS)

The kinetics of the reaction (Mg,Fe)-olivine + H2O ? serpentine + magnetite + brucite + H2 were investigated at 500 bars in the 250-350°C range using natural olivine (San Carlos; Fo91) with grain sizes between 1 and 150 ?m and for run durations up to 514 d. The amount of magnetite produced, which directly relates to reaction progress, was accurately monitored using up to 24 time-resolved magnetic measurements per experiment. Eighty percent of serpentinization was achieved after 60 d for olivine grain sizes of 5-15?m and after 500 d for grain sizes of 50-63 ?m. Serpentinization kinetics were found to be inversely proportional to the geometrical surface area of the starting olivine grains. They were one or two orders of magnitude slower than serpentinization kinetics commonly used for modeling serpentinization-related processes. The nature of the serpentine mineral product depended on the initial olivine grain size (IGS); for IGS in the 5-150?m range lizardite formed, and olivine dissolution was the rate-limiting process. At IGS below 5?m, chrysotile crystallized instead of lizardite, and the relationship between olivine surface area and reaction kinetics no longer held. We infer that for such small olivine grain sizes dissolution is no longer the rate-limiting process. Serpentinization in our experiments was associated with the creation of new reactive surface area according to two cooperative processes: etch pits formation associated with dissolution and grain fracturing for IGS above 20?m. Interestingly, fractures and etch pits with similar geometry and sizes were also observed for residual olivine (with a typical grain size of 50 ?m) in serpentinized peridotite samples from the Southwest Indian Ridge. This suggests that the processes governing olivine serpentinization kinetics in our experiments are similar to those prevailing in natural systems. We therefore suggest that the new kinetic data set that we present here, which encompasses a range of olivine grain sizes and reaction temperatures, is relevant to the serpentinization of olivine in the oceanic crust insofar as water is available.

Malvoisin, Benjamin; Brunet, Fabrice; Carlut, Julie; RouméJon, StéPhane; Cannat, Mathilde

2012-04-01

268

Olivines in the Kaba carbonaceous chondrite and constraints on their formation  

NASA Astrophysics Data System (ADS)

Kaba is unique in containing almost pure fayalitic olivine (Fo(sub 0.1)). Its coexistence with pure forsterite up to Fo(sub 99.6) and normal (Fo(sub 92) to Fo(sub 59)) and reversely (Fo(sub 0.4) to Fo(sub 4.7)) zoned olivines suggest that the Kaba olivines are in thermodynamic disequilibrium and experienced a complicated history. The fayalite is sufficiently pure that it is unlikely that it could have been produced by fractional crystallization. A gas-solid reaction under oxidizing conditions (H2O/H2 ratio approximately 10) is probably responsible for its formation.

Hua, X.; Buseck, P. R.

1993-03-01

269

Relict olivine, chondrule recycling, and the evolution of nebular oxygen reservoirs  

NASA Astrophysics Data System (ADS)

Chondrules often contain relict olivine grains that did not crystallize in situ, providing opportunities to decipher how chondrule components evolved. We studied olivine in the Sahara-97210 (LL3.2), Wells (LL3.3) and Chainpur (LL3.4) chondrites using SEM, EMPA, and SIMS techniques. Oxygen isotopes were analyzed in 16 objects from all three meteorites, and trace elements were analyzed in Sahara-97210 and Chainpur. Two groups of olivine are identified based on oxygen isotope compositions. One group is enriched in 16O (? 17O ˜ - 8 to - 4‰) and falls close to the CCAM mixing line; it includes forsterite and Mg-rich olivine present as relict grains in Type II (ferrous) chondrules and the forsteritic cores of some isolated grains. These low-? 17O grains are poor in MnO (< 0.2 wt.%) and are usually enriched in CaO (˜ 0.3-0.65 wt.%). The other group is less enriched in 16O (? 17O ˜ - 3 to + 4 ‰); it includes normal (non-relict) ferrous olivine in type II chondrules, normal (non-relict) Mg-rich olivine in Type I (magnesian) chondrules, dusty olivine relict grains in Type I chondrules, and Mg-rich olivine relicts in a Type II and a Type I chondrule. These high-? 17O grains have variable CaO (0-0.95 wt.%) and MnO (˜ 0-0.45 wt.%) contents, with the more calcic and Mn-poor compositions associated with forsteritic olivine. Trace-element data show that forsteritic olivine grains in both oxygen groups are similarly enriched in refractory elements (Al, Sc, Y, Ca, Ti, V) and depleted in volatile elements (Cr, Mn, P, Rb, sometimes K and Na) compared to normal ferrous olivine, suggesting that variations in chemical composition reflect the extent of thermal processing (greater for magnesian olivine). The data are consistent with a model in which nebular reservoirs became less enriched in 16O with time. An earlier episode of chondrule formation produced Type I chondrules and isolated forsterites in carbonaceous chondrites, and forsteritic grains that were incorporated into ordinary chondrites as relict grains in chondrules and as isolated grains. Later episodes of chondrule formation produced both Type I and Type II chondrules in ordinary chondrites under a variety of thermal and redox conditions.

Ruzicka, A.; Hiyagon, H.; Hutson, M.; Floss, C.

2007-05-01

270

Measurement of Activation Volume of Dry Olivine at High Pressure  

NASA Astrophysics Data System (ADS)

Despite considerable effort to measure the activation volume V* of creep of olivine using a new generation of high-pressure deformation machines, namely the Rotational Drickamer Apparatus (RDA) and the Deformation- DIA (D-DIA) in conjunction with synchrotron x-ray sources, progress has been marred by a combination of an apparently weak signal (i.e., low V*) and measurement noise. The latter has a broad spectrum of causes, from inherent limitations of measurement systems (of stress, primarily) to limited time available for creep experiments at synchrotron sources to investigator-induced variations of sample state during measurement. We report here measurements following a significant advance in regulation of sample state: deforming polycrystalline olivine in a dry state under more uniform mechanical conditions gives us our first clear signal of a positive activation volume. The advance has been made possible by a choice of assembly materials that assures anhydrous conditions around the sample, and a technique for testing in the absence of a thermocouple within the sample assembly. The key to the anhydrous assembly is a self-gasketing D-DIA cube of hybrid composition: a sphere of mullite embedded in a cube of unfired pyrophyllite, where the diameter of the sphere matches the edge length of the cube (6-mm in our case). Unfired pyrophyllite is an excellent gasketing material, being soft and (in notable contrast with mullite) non-friable. Additionally, as a cube-filling "web" around the mullite sphere, the pyrophyllite is ideally configured for D-DIA self gasketing: maximum volume at the cube corners, minimum (zero) volume at cube faces. Thus the configuration under pressure is a bone-dry mullite pressure medium gasketed by pyrophyllite. Removal of the thermocouple from the deformation piston results in a demonstrably more symmetric deformation column within the assembly for the entire duration of the experiment, and the absence of the thermocouple is reliably compensated by off-line calibration of furnace power vs temperature. Results of creep experiments in the new cell indicate a value of V*/n (where n is the stress exponent) of 3 ± 1 × 10-6 m3/mol between 3 and 6 GPa. The value of n will be better resolved in future experiments, but if the deformation is in the dislocation creep regime (n ~ 3.5), then V* ~ 10 × 10-6 m3/mol.

Durham, W. B.; Kohlstedt, D. L.; Mei, S.; Dixon, D. A.; Wang, L.

2007-12-01

271

Titanium solubility in olivine in the system TiO2 MgO SiO2: no evidence for an ultra-deep origin of Ti-bearing olivine  

NASA Astrophysics Data System (ADS)

The finding of ilmenite rods in olivine from orogenic peridotites has sparked a discussion about the processes of incorporation and exsolution of titanium in olivine. We have experimentally investigated the solubility of Ti in olivine as a function of composition, temperature and pressure in the synthetic TiO2 MgO SiO2 system. Experiments at atmospheric pressure in the temperature range 1,200 1,500°C showed that the highest concentration of TiO2 is obtained when olivine coexists with spinel (Mg2TiO4). The amount of TiO2 in olivine in the assemblages olivine + spinel + periclase and olivine + spinel + ilmenite at 1,500°C was 1.25 wt.%. Changes in the coexisting phases and decreasing temperature result in a significant reduction of the Ti solubility. Olivine coexisting with pseudobrookite (MgTi2O5) and a Ti Si-rich melt at 1,500°C displays a fourfold lower TiO2 content than when buffered with spinel. A similar decrease in solubility is obtained by a decrease in temperature to 1,200°C. There is a negative correlation between Ti and Si and no correlation between Ti and Mg in Ti-bearing olivine. Together with the established phase relations this suggests that there is a direct substitution of Ti for Si at these temperatures, such that the substituting component has the stoichiometry Mg2TiO4. The unit cell volume of olivine increases systematically with increasing TiO2 content demonstrating that the measured TiO2 contents in olivine are not caused by micro-inclusions but by incorporation of Ti in the olivine structure. Least squares fitting of 20 olivine unit cell volumes against the Ti content yield the relation: V (Å3)=290.12(1) + 23.67(85) NTi. The partial molar volume of end-member Mg2TiO4 olivine (NTi=1) is thus 47.24±0.13 cm3. The change of the Ti solubilty in olivine coexistent with rutile and orthopyroxene with pressure was investigated by piston cylinder experiments at 1,400°C from 15 to 55 kbar. There is no increase in TiO2 contents with pressure and in all the experiments olivine contains ~0.2 wt.% TiO2. Moreover, a thermodynamic analysis indicates that Ti contents of olivine coexisting with rutile and orthopyroxene should decrease rather than increase with increasing pressure. These data indicate that the ilmenite exsolution observed in some natural olivine does not signify an ultra-deep origin of peridotite massifs.

Hermann, J.; O'Neill, H. S. C.; Berry, A. J.

2005-02-01

272

Optical constants of olivine particles between wavelengths of 7 and 200 microns  

SciTech Connect

Emission features are computed for spherical olivine particles of 0.03, 0.3, 3.0, and 30 micron radii, on the basis of laboratory determinations of the olivine particles' optical constants over the 7 to 200 micron range. It is noted that, while particles of radii smaller than 0.3 microns exhibit emission peaks at 16.3, 18.6, 23, 28, and 33.6 microns, together with a 10-micron region twin-peak structure, these readings weaken for particle radii of 3 microns or more. The appearance of the twin-peak feature in Comet P/Halley is accordingly judged to imply the presence of olivine particles smaller than 1 micron in radius; alternatively, such smaller olivines' enhancement may occur in the comet, which also exhibits a 10-micron silicate band twin-peak feature. 26 refs.

Mukai, Tadashi; Koike, Chiyoe (Kanazawa Institute of Technology (Japan) Kyoto Pharmaceutical Univ. (Japan))

1990-09-01

273

An Interactive Computer Program for Simulating the Effects of Olivine Fractionation from Basaltic and Ultrabasic Liquids.  

ERIC Educational Resources Information Center

|Describes interactive computer program (listing available from author) which simulates olivine fractionation from basaltic/ultrabasic liquid. The menu-driven nature of the program (for Apple II microcomputer) allows students to select ideal Rayleigh fractionation or equilibrium crystallization. (JN)|

Pearce, Thomas H.

1983-01-01

274

New Spinel-Olivine Oxybarometer: Near-Liquidus Partitioning of V between Olivine-Melt, Spinel-Melt, and Spinel-Olivine in Martian Basalt Composition Y980459 as a Function of Oxygen Fugacity.  

National Technical Information Service (NTIS)

Our research on valence state partitioning began in 2005 with a review of Cr, Fe, Ti, and V partitioning among crystallographic sites in olivine, pyroxene, and spinel. That paper was followed by several on QUE94201 melt composition and specifically on Cr,...

A. S. Bell C. K. Shearer J. Jones J. J. Papike L. Le P. V. Burger

2013-01-01

275

The Fayalite Content of Chondritic Olivine: Obstacle to Understanding the Condensation of Rocky Material  

Microsoft Academic Search

Solar gas is too reducing for the equilibrium XFa in condensate olivine to reach the minimum XFa of the precursors of chondrules in unequilibrated ordinary chondrites (UOCs), 0.145, at temperatures above those where Fe-Mg interdiffusion in olivine stops. Vaporization of a region enriched in dust relative to gas compared to solar composition yields higher fO2, and condensate grains with higher

A. V. Fedkin; L. Grossman

2006-01-01

276

Investigation on deformation of olivine at high pressure and low temperature  

Microsoft Academic Search

Olivine is the dominant mineral in the upper mantle. Several deformation experiments of polycrystalline powdered San Carlos olivine at subduction zone conditions (pressures of 3-5 GPa and temperatures of 25-1100°C) have been performed on a deformation DIA (D-DIA) apparatus, SAM85, at X17B2, National Synchrotron Light Source (NSLS). Enstatite (MgSiO3) (3-5% total quality of sample) is used as buffer to control

Hongbo Long

2008-01-01

277

Fault Reactivation During the Olivine to Wadsleyite Transition: A Mechanism for Deep Focus Earthquakes  

Microsoft Academic Search

Slip plane orientations of some deep-focus earthquakes suggest that earthquakes can be triggered by reactivation of pre-existing faults in the transition zone. In order to test this theory, we have studied the effect of the olivine-wadsleyite transition on the remobilization of pre-existing olivine faults by performing axisymmetric deformation experiments in a multi-anvil apparatus. Experiments were performed on 3 mm long,

D. Dobson; A. de Ronde; F. Heidelbach; P. Meredith; S. Boon

2006-01-01

278

Hydrous olivine unable to account for conductivity anomaly at the top of the asthenosphere  

Microsoft Academic Search

The oceanic asthenosphere is observed to have high electrical conductivity, which is highly anisotropic in some locations. In the directions parallel and normal to the plate motion, the conductivity is of the order of 10-1 and 10-2Sm-1, respectively, which cannot be explained by the conductivity of anhydrous olivine. But because hydrogen can be incorporated in olivine at mantle pressures, this

Takashi Yoshino; Takuya Matsuzaki; Shigeru Yamashita; Tomoo Katsura

2006-01-01

279

Combining [ 3He] cosmogenic dating with U–Th\\/He eruption ages using olivine in basalt  

Microsoft Academic Search

This paper presents new U–Th\\/He crystallization and 3He exposure ages on olivine for a suite of basalt samples from the Snake River Plain, Idaho. The results provide the first demonstration that U–Th\\/He geochronology can be successfully applied to Late Quaternary basalts using measurements of olivine phenocrysts as opposed to U-rich minerals. The approach employs abrasion to remove the outer rinds

Sarah M. Aciego; Donald J. DePaolo; B. M. Kennedy; Michael P. Lamb; Kenneth W. W. Sims; William E. Dietrich

2007-01-01

280

Experimental Study of the Effects of Dissolved Sulfur on Olivine-Liquid Ni Partitioning Behavior  

Microsoft Academic Search

The partitioning of Ni between olivine and a silicate melt is best described in terms of the Nernst partition coefficient, DNi which is equal to (wt % Ni)oliv \\/ (wt % Ni)melt. Ni in a silicate melt may partition into olivine according to the following reaction NiOmelt+ Fe2Si0.5O2oliv = Ni2Si0.5O2oliv + FeOmelt. In the presence of dissolved S, the oxide

J. G. Brophy; C. Li

2003-01-01

281

Cr-spinel\\/olivine and Cr-spinel\\/liquid nickel partition coefficients from natural samples  

Microsoft Academic Search

The Nernst partition coefficient of nickel (DNi) between Cr-spinel and silicate melt in natural systems has been investigated using mid-ocean ridge basalts (MORB) and other volcanic rocks. The Cr-spinel\\/olivine DNi values in volcanic rocks are between 1.2 and 0.3, indicating that the Cr-spinel\\/liquid DNi values vary from slightly higher to significantly lower than the olivine\\/liquid DNi values in natural systems.

Chusi Li; Edward M. Ripley; Yan Tao; Edmond A. Mathez

2008-01-01

282

The effect of S on the partitioning of Ni between olivine and silicate melt in MORB  

Microsoft Academic Search

The partitioning behavior of Ni between olivine and silicate melt in S-bearing systems has been investigated using mid-ocean ridge basalts (MORBs). The Nernst Ni partition coefficient between olivine and silicate melt (DNi) derived from the MORB samples varies between 4 and 9, values that are up to 50% lower than those derived from S-free experimental systems of similar composition. The

Chusi Li; E. M Ripley; E. A Mathez

2003-01-01

283

Lamellar pyroxene-spinel symplectites in lunar olivine from the Luna 24 regolith  

Microsoft Academic Search

Cr-Ca lamellae in a magnesian olivine grain (section 1611) from the Luna 24 regolith were investigated in detail by electron\\u000a microprobe analysis (EMPA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that\\u000a the lamellae are parallel to the (100) plane of oxygen closest packing in olivine and consist of regular vermicular intergrowths\\u000a of two phases, diopside

N. R. Khisina; R. Wirth; M. A. Nazarov

2011-01-01

284

Experimental and Natural Evidence for Rapid Water Exchange Between Melt Inclusions in Olivine and Host Magma  

NASA Astrophysics Data System (ADS)

We have carried an experimental study aimed at evaluating the ability of olivine to isolate chemically melt inclusions from the host magma after their entrapment. We demonstrate that nearly 'dry' (<0.5 wt% of water) melt inclusions from Galapagos Plateau basalt gain up to 2.5 wt% of water if they are placed for 2 days in a water-bearing melt at 200 MPa and 1140 °C. Amount of structurally bound water in olivine crystals also increased, maintaining equilibrium with hydrous matrix melt (D olivine-melt ~ 0.002). Despite the complete re-equilibration of the system with respect to water, no or only partial re-equilibration was achieved with respect to major, volatile (S, Cl) and incompatible trace elements between matrix melt, olivines and melt inclusions. The apparent diffusion coefficient of water in olivine is found to be more or equal to 5E-12 m2/s at our experimental conditions that is as fast as proton-vacancy diffusion and at least 3-4 orders of magnitude faster than for other major (e.g., Fe and Mg) and trace elements at dry or hydrous conditions. These results indicate that inclusions in olivine can rapidly and selectively exchange water with matrix melt, probably, through combination of proton diffusion and molecular water transport along dislocations in olivine. The rapid re-equilibration of melt inclusions with matrix melt or atmosphere can explain the decoupling of water and incompatible trace elements (e.g, water vs. potassium) reported for suites of primitive inclusions from oceanic settings (43 °N MAR, FAMOUS, Galapagos) and island arcs (Kamchatka, Central America, Cyprus). Rare cases of well preservation of initial water content in suites of co- genetic inclusions imply very short residence time (a few hours) of the olivine phenocrysts in magma with contrasting water content during fractionation and transport to the surface and rapid quenching upon eruption.

Portnyagin, M.; Almeev, R.; Matveev, S.; Mironov, N.; Holtz, F.

2008-12-01

285

Characterization and petrologic interpretation of olivine-rich basalts at Gusev Crater, Mars  

NASA Astrophysics Data System (ADS)

Rocks on the floor of Gusev crater are basalts of uniform composition and mineralogy. Olivine, the only mineral to have been identified or inferred from data by all instruments on the Spirit rover, is especially abundant in these rocks. These picritic basalts are similar in many respects to certain Martian meteorites (olivine-phyric shergottites). The olivine megacrysts in both have intermediate compositions, with modal abundances ranging up to 20-30%. Associated minerals in both include low-calcium and high-calcium pyroxenes, plagioclase of intermediate composition, iron-titanium-chromium oxides, and phosphate. These rocks also share minor element trends, reflected in their nickel-magnesium and chromium-magnesium ratios. Gusev basalts and shergottites appear to have formed from primitive magmas produced by melting an undepleted mantle at depth and erupted without significant fractionation. However, apparent differences between Gusev rocks and shergottites in their ages, plagioclase abundances, and volatile contents preclude direct correlation. Orbital determinations of global olivine distribution and compositions by thermal emission spectroscopy suggest that olivine-rich rocks may be widespread. Because weathering under acidic conditions preferentially attacks olivine and disguises such rocks beneath alteration rinds, picritic basalts formed from primitive magmas may even be a common component of the Martian crust formed during ancient and recent times.

McSween, H. Y.; Wyatt, M. B.; Gellert, R.; Bell, J. F.; Morris, R. V.; Herkenhoff, K. E.; Crumpler, L. S.; Milam, K. A.; Stockstill, K. R.; Tornabene, L. L.; Arvidson, R. E.; Bartlett, P.; Blaney, D.; Cabrol, N. A.; Christensen, P. R.; Clark, B. C.; Crisp, J. A.; Des Marais, D. J.; Economou, T.; Farmer, J. D.; Farrand, W.; Ghosh, A.; Golombek, M.; Gorevan, S.; Greeley, R.; Hamilton, V. E.; Johnson, J. R.; Joliff, B. L.; Klingelhöfer, G.; Knudson, A. T.; McLennan, S.; Ming, D.; Moersch, J. E.; Rieder, R.; Ruff, S. W.; Schröder, C.; de Souza, P. A.; Squyres, S. W.; Wänke, H.; Wang, A.; Yen, A.; Zipfel, J.

2006-01-01

286

Possible mantle origin of olivine around lunar impact basins detected by SELENE  

NASA Astrophysics Data System (ADS)

The composition, structure and evolution of the Moon's mantle is poorly constrained. The mineral olivine, one of the main constituents of Earth's mantle, has been identified by Earth-based telescopic observations at two craters on the near side of the Moon, Aristarchus and Copernicus. Global reflectance spectra in five discrete spectral bands produced by the spacecraft Clementine suggested several possible olivine-bearing sites, but one of the candidate occurrences of olivine was later re-classified, on the basis of continuous reflectance spectra over the entire 1?m band, as a mixture of plagioclase and pyroxene. Here we present a global survey of the lunar surface using the Spectral Profiler onboard the lunar explorer SELENE/Kaguya. We found many exposures of olivine on the Moon, located in concentric regions around the South Pole-Aitken, Imbrium and Moscoviense impact basins where the crust is relatively thin. We propose that these exposures of olivine can be attributed either to an excavation of the lunar mantle at the time of the impacts that formed the basins, or to magnesium-rich pluton in the Moon's lower crust. On the basis of radiative transfer modelling, we suggest that at least some of the olivine detected near impact basins originates from upper mantle of the Moon.

Yamamoto, Satoru; Nakamura, Ryosuke; Matsunaga, Tsuneo; Ogawa, Yoshiko; Ishihara, Yoshiaki; Morota, Tomokatsu; Hirata, Naru; Ohtake, Makiko; Hiroi, Takahiro; Yokota, Yasuhiro; Haruyama, Junichi

2010-08-01

287

Shallow crystallization of Kilauean olivines: Magma density and picritic eruptions  

SciTech Connect

Of 35 analyzed glass inclusions in olivine phenocrysts from the 1959 Kilauea Iki eruption, 23 formed at pressures less than 1 Kbar, 10 between 1 and 2 Kbar and 2 at pressures greater than 2 Kbar. The surprisingly topheavy distribution of formation pressures suggests that the 1959 magma rose rapidly to the upper parts of Kilauea's summit magma storage reservoir where cooling and crystallization dominantly occurred. The implication that the parental magma was buoyant relative to preexisting resident magma is consistent with an expected preeruptive bulk CO[sub 2] content of 0.3wt.% and petrographic evidence for turbulent mixing between parental and preexisting magma. That the 1959 magma was rich not only in crystals but also in gas, as evidenced by its high lava fountains, suggests that the storage time in the summit reservoir was too short for either crystals or gas to be lost. Therefore, the 1959 Kilauean magma probably is a near-parental magma that rose and formed a gas- and crystal-rich cap at the top of Kilauea's summit magma storage reservoir. Whether parental magma rises to the top or ponds at the base of the summit reservoir depends mainly on reservoir pressure and magma gas content. Consequently, it seems likely that the eruptive and degassing behavior of Kilauea is regulated in part by an interplay between the CO[sub 2] content of parental magma and the pressure at the base of the summit storage reservoir.

Anderson, A.T. Jr.; Brown, G.G. (Univ. of Chicago, IL (United States). Dept. of the Geophysical Sciences)

1992-01-01

288

High-temperature viscoelasticity of fine-grained polycrystalline olivine  

NASA Astrophysics Data System (ADS)

Torsional forced-oscillation and microcreep methods have been employed in a study of the viscoelastic behaviour of fine-grained polycrystalline olivine at high temperatures (to 1300°C), seismic frequencies and low strain amplitudes. The Fo90 specimens are of low porosity and low dislocation density. They vary in mean grain size from 8 to 150?m and contain only trace amounts (<<0.1vol%) of quenched melt glass. For T<=900°C, their behaviour is essentially elastic and the shear modulus G closely approaches that expected for a dense polycrystal from single-crystal elasticity data - confirming the suppression of thermal microcracking in this study. At higher temperatures, pronounced absorption-band dissipation and associated dispersion of the shear modulus provide evidence of linear viscoelastic behaviour. Both recoverable (anelastic) and permanent (viscous) strains are involved and the proportion of the latter increases with increasing temperature and decreasing frequency. Comparison of the results for the three specimens provides a clear indication that the viscoelastic behaviour, attributed to diffusional processes, is grain-size-sensitive with the dissipation and associated dispersion increasing with decreasing grain size. Both elastically accommodated and diffusionally accommodated grain-boundary sliding appear to be implicated.

Tan, B. H.; Jackson, I.; Fitz Gerald, J. D.

289

Structural and Electrochemical Characterization of Lithium Transition Metal Phosphates  

NASA Astrophysics Data System (ADS)

The lithium ion battery has emerged as one of the most promising hybrid vehicle energy storage systems of the future. Of the potential cathode chemistries explored, lithium transition metal phosphates have generated a significant amount of interest due to their low-cost precursors, potential ease of synthesis, stability, and their environmentally friendly nature. This is in contrast to layered oxide systems such as LiCoO2, which have long been considered state of the art, but are now being reevaluated due to their structural instability at elevated temperatures, and higher cost. In particular, LiFePO4 has an operating potential comparable to those batteries available on the market (˜3.5V vs. Li/Li+), and higher theoretical specific capacity (170mAh/g vs. that of LiCoO2 which is 140mAh/g). The manganese analog to LiFePO4, LiMnPO4, exhibits a higher operating potential (˜4.1V v Li/Li+), and the same theoretical capacity, however Li-ion diffusion through this structure is much more rate limited and its theoretical capacity cannot be realized at rates suitable for commercial applications. The purpose of this work was threefold: 1) To explore the impact of Fe substitution on Mn sites in LiMnPO 4. 2) To examine the effects of alterations to the particle/electrolyte interface on rate capability. 3) To explore a novel fabrication route for LiMnPO4 using microwaves, and determine an optimal power and time combination for best performance. The coexistence of Fe and Mn on the transition metal site M, of LiMPO 4 resulted in an improved apparent Li-ion diffusivity in both Fe and Mn regimes as compared to that observed for LiFePO4 and LiMnPO 4 respectively. Calculations made from two different analysis methods, cyclic voltammetry (CV) and galvanostatic intermittent titration (GITT) drew this same conclusion. The signature characteristics observed from the CVs pertaining to single and dual phase reactions led to a delithiation model of LiFe0.5Mn0.5PO4 proposing the localization of half the Li atoms with Fe and half with Mn. Following this work, pure LiMnPO 4 was explored. LiMnPO4 was successfully fabricated using rapid, solid state microwave irradiation. Three classes of materials were prepared to study the effects of particle size, carbon coating, and electrolytic environment on rate capability. Reduction in particle size, carbon coating, and the aqueous electrolyte environment provided the most favorable conditions for performance enhancement. Based on the initial promising results of solid state microwave synthesis, further studies were conducted to optimize irradiation parameters. C-LiMnPO 4 fabricated at 200W for 5.0 minutes demonstrated the most superior rate capability. This material attained its full theoretical specific capacity, showing promise for the advancement of materials fabricated via this method.

Hashambhoy, Ayesha Maria

290

Reaction rim growth on olivine in silicic melts: Implications for magma mixing  

USGS Publications Warehouse

Finely crystalline amphibole or pyroxene rims that form during reaction between silicic host melt and cognate olivine xenocrysts, newly introduced during magma mixing events, can provide information about the timing between mixing and volcanic eruptions. We investigated rim growth experimentally by placing forsteritic olivine in rhyolitic and rhyodacitic melts for times between 25 and 622 h at 50 and 150 MPa, H2O-saturated, at the Ni-NiO buffer. Rims of orthopyroxene microlites formed from high-silica rhyolite and rhyodacite melts at 885??C and 50 MPa, and in the rhyolite at 150 MPa and 885??C. Rims of amphibole with lesser orthopyroxene formed in the rhyolite at 150 MPa and 800??C and in the rhyodacite at 150 MPa and 885??C. Irregular, convolute olivine edges and mass balance between olivine, melt, and rim phases show that olivine partly dissolved at all conditions. Iron-rich zones at the exteriors of olivines, which increased in width parabolically with time, show that Fe-Mg interdiffusion occurring in olivines was not outpaced by olivine dissolution. Linear increases of the square of rim widths with time suggest that diffusion within the melt is the rate-controlling process for olivine dissolution and rim growth. Rims grew one-half to one order-of-magnitude faster when melt water contents were doubled, unless conditions were far above the liquidus. Rim growth rate in rhyolite increases from 0.055 ?? 0.01 ??m2/h at 885 ??C and 50 MPa to 0.64 ?? 0.13 ??m2/h at 800 ??C and 150 MPa. Melt composition has a lesser effect on rim growth rates, with growth rate increasing as melt SiO2 content decreases. Pyroxene rims on olivines in andesite erupted from Arenal volcano (Costa Rica) grew at a rate of 3.0 ?? 0.2 ??m2/h over an eleven-year period. This rate is faster than those of the experiments due to lower melt viscosity and higher temperatures, and suggests that a magma mixing event preceded the start of the eruption by days.

Coombs, M. L.; Gardner, J. E.

2004-01-01

291

The rate of water loss from olivine-hosted melt inclusions  

NASA Astrophysics Data System (ADS)

Diffusive water loss from olivine-hosted melt inclusions has been reported previously. This process must be considered when interpreting melt inclusion data. This study measured the rate of water loss from olivine-hosted melt inclusions during heating-stage experiments to test a previous diffusive reequilibration model and the hydrogen diffusion mechanism that controls the rate. Olivine-hosted melt inclusions were heated to a constant temperature in reduced Ar gas in a heating stage for a few hours, and unpolarized Fourier transform infrared spectra were repeatedly measured through the inclusions. Water loss occurred rapidly in the experiments. Within a few hours, the water absorbance at 3,500 cm-1 wavenumber decreased by half. The observed water loss rate can be explained by the diffusive reequilibration model and hydrogen diffusion in olivine coupled with metal vacancy. The beginning of water loss was different in the low- and high-temperature experiments. At low temperatures (1,423 and 1,437 K), water loss did not occur in the initial 1 or 2 h. At high temperatures (1,471-1,561 K), water loss began immediately. The initial time period without water loss at low temperatures may be explained by a hydrogen fugacity barrier in the host olivine. At low temperatures, the internal pressure may be lower than the equilibrium pressure of melt inclusion and olivine, causing lower hydrogen fugacity in the melt inclusion than in the olivine, which will delay the water loss from the melt inclusion. The tested model and diffusivity were used to estimate the rate of water loss during homogenization experiments and magma eruption and cooling. For 1-h homogenization experiment, the model shows that large inclusions (50 ?m radius) in large olivines (500 ?m radius) are robust against water loss, while large or small inclusions (50-10 ?m radius) in small olivines (150 ?m radius) may suffer 30-100% water loss. For natural samples, the correlation between water concentration and melt inclusion and olivine sizes may be helpful to infer the initial water concentration, degree of diffusive reequilibration, and magma cooling rate.

Chen, Yang; Provost, Ariel; Schiano, Pierre; Cluzel, Nicolas

2011-09-01

292

Laboratory measurements of the viscous anisotropy of olivine aggregates.  

PubMed

A marked anisotropy in viscosity develops in Earth's mantle as deformation strongly aligns the crystallographic axes of the individual grains that comprise the rocks. On the basis of geodynamic simulations, processes significantly affected by viscous anisotropy include post-glacial rebound, foundering of lithosphere and melt production above subduction zones. However, an estimate of the magnitude of viscous anisotropy based on the results of deformation experiments on single crystals differs by three orders of magnitude from that obtained by grain-scale numerical models of deforming aggregates with strong crystallographic alignment. Complicating matters, recent experiments indicate that deformation of the uppermost mantle is dominated by dislocation-accommodated grain-boundary sliding, a mechanism not activated in experiments on single crystals and not included in numerical models. Here, using direct measurements of the viscous anisotropy of highly deformed polycrystalline olivine, we demonstrate a significant directional dependence of viscosity. Specifically, shear viscosities measured in high-strain torsion experiments are 15 times smaller than normal viscosities measured in subsequent tension tests performed parallel to the torsion axis. This anisotropy is approximately an order of magnitude larger than that predicted by grain-scale simulations. These results indicate that dislocation-accommodated grain-boundary sliding produces an appreciable anisotropy in rock viscosity. We propose that crystallographic alignment imparts viscous anisotropy because the rate of deformation is limited by the movement of dislocations through the interiors of the crystallographically aligned grains. The maximum degree of anisotropy is reached at geologically low shear strain (of about ten) such that deforming regions of the upper mantle will exhibit significant viscous anisotropy. PMID:23257885

Hansen, L N; Zimmerman, M E; Kohlstedt, D L

2012-12-20

293

Evolution of olivine lattice preferred orientation during simple shear in the mantle  

NASA Astrophysics Data System (ADS)

Understanding the variation of olivine lattice preferred orientation (LPO) as a function of shear strain is important for models that relate seismic anisotropy to the kinematics of deformation. We present results on the evolution of olivine orientation as a function of shear strain in samples from a shear zone in the Josephine Peridotite (southwest Oregon). We find that the LPO in harzburgites re-orients from a pre-existing LPO outside the shear zone to a new LPO with the olivine [100] maximum aligned sub-parallel to the shear direction between 168% and 258% shear strain. The strain at which [100] aligns with the shear plane is slightly higher than that observed in experimental samples, which do not have an initial LPO. While our observations broadly agree with the experimental observations, our results suggest that a pre-existing LPO influences the strain necessary for LPO alignment with the shear direction. In addition, olivine re-alignment appears to be dominated by slip on both (010)[100] and (001)[100], due to the orientation of the pre-existing LPO. Fabric strengths, quantified using both the J- and M-indices, do not increase with increasing shear strain. Unlike experimental observations, our natural samples do not have a secondary LPO peak. The lack of a secondary peak suggests that subgrain rotation recrystallization dominates over grain boundary migration during fabric re-alignment. Harzburgites exhibit girdle patterns among [010] and [001] axes, while a dunite has point maxima. Combined with the observation that harzburgites are finer grained than dunites, we speculate that additional phases (i.e., pyroxenes) limit olivine grain growth and promote grain boundary sliding. Grain boundary sliding may relax the requirement for slip on the hardest olivine system, enhancing activation of the two easiest olivine slip systems, resulting in the [010] and [001] girdle patterns. Overall, our results provide an improved framework for calibration of LPO evolution models.

Warren, Jessica M.; Hirth, Greg; Kelemen, Peter B.

2008-08-01

294

The Effect of Titanium on Water Incorporation and Rheology of Olivine  

NASA Astrophysics Data System (ADS)

While there is general agreement that water significantly affects the physical properties of rocks, the water incorporation mechanism, particularly in olivine, is still under debate. Experiments with synthetic, polycrystalline olivine allow the controlled addition of trace elements as well as water. To this end we have conducted hotpressing and deformation experiments with solution-gelation derived Fo90 olivine doped with Ca and Ti. While the addition of Ca does not change the behavior relative to trace element-free solgel, trace amounts of titanium have a significant effect both on water incorporation and the rheology. Infrared spectroscopy suggests that from the presence of titanium water is retained in olivine during prolonged firing in a controlled atmosphere furnace at 1400C, while it is lost in Ti- free olivine. The experimental infrared spectra have the same two prominent absorption bands at 3572 and 3525 cm-1 as spectra of olivine from xenoliths. These bands indicate that water (hydrogen) is incorporated in a titanium-clinohumite type point defect. This defect is stable and significantly affects the physical properties of mantle rocks at low water contents. Diffusion creep rates are increased by about one order of magnitude in Ti-doped olivine, even if water contents are below detection levels. Experiments with different capsule materials also highlight their importance for water retention in the absence of buffers. The potential significance of the relationship between Ti abundance, water content and rheology for natural systems is shown for example by the correlation between Ti content and hydrogen in titanium clinohumite defects in cratonic xenoliths.

Faul, U.; Farla, R. J.; Fitz Gerald, J. D.; Jackson, I.

2011-12-01

295

Experimental determination of Ni diffusion coefficients in olivine and their dependence on temperature, composition, oxygen fugacity, and crystallographic orientation  

Microsoft Academic Search

Diffusion couple experiments were carried out with San Carlos olivine (Fo90) and NiFe alloys (Ni100, Ni97Fe3, Ni90Fe10) or other olivine compositions (Fo100, Fo25) in order to determine the dependence on temperature, oxygen fugacity, composition and crystallographic orientation of Ni diffusion coefficient (DNi) in olivine. Experiments at 1 atmosphere total pressure cover a temperature range of 900–1445°C with run durations from

Christof Petry; Sumit Chakraborty; Herbert Palme

2004-01-01

296

Mineralogy and petrology of amoeboid olivine inclusions in CO3 chondrites: Relationship to parent-body aqueous alteration  

Microsoft Academic Search

Petrographic and mineralogic studies of amoeboid olivine inclusions (AOIs) in CO3 carbonaceous chondrites reveal that they are sensitive indicators of parent-body aqueous and thermal alteration. As the petrologic subtype increases from 3.0 to 3.8, forsteritic olivine (Fa0-1) is systematically converted into ferroan olivine (Fa60-75). We infer that the Fe, Si and O entered the assemblage along grain boundaries, forming ferroan

Lysa J. Chizmadia; Alan E. Rubin; John T. Wasson

2002-01-01

297

Nickel, Cobalt and Chromium in early lunar magma ocean olivine: Constraints on the petrogenesis of the Mg-suite  

Microsoft Academic Search

The parental magmas of the lunar highlands Mg-suite cumulates had enigmatic chemical signatures. They co-crystallized Mg-rich olivine and Ca-rich plagioclase and had extremely evolved trace element signatures (KREEP). Most models of Mg-suite petrogenesis call upon early, Mg-rich, olivine dominated LMO cumulates as a source to explain the high Mg* of the parental magmas. The olivine in the Mg-suite, however, contains

S. M. Elardo; C. Shearer Jr.; D. S. Draper

2010-01-01

298

Impact of geoengineering with olivine dissolution on the carbon cycle and marine biology  

NASA Astrophysics Data System (ADS)

We investigate the potential of a specific geoengineering technique: the carbon sequestration by artificially enhanced silicate weathering via the dissolution of olivine. This approach would not only operate against rising temperatures but would also oppose ocean acidification. If details of the marine chemistry are taken into consideration, a new mass ratio of CO2 sequestration per olivine dissolution of about 1 is achieved, 20% smaller than previously assumed. We calculate that this approach has the potential to sequestrate up to 1 Pg of C per year directly, if olivine is distributed as fine powder over land areas of the humid tropics, but this rate is limited by the saturation concentration of silicic acid. These upper limit sequestration rates come at the environmental cost of pH values in the rivers rising to 8.2 in examples for the rivers Amazon and Congo (Köhler et al., 2010). The secondary effects of the input of silicic acid connected with this approach leads in an ecosystem model (ReCOM2.0 in MITgcm) to species shifts aways from the calcifying species towards diatoms, thus altering the biological carbon pumps. Open ocean dissolution of olivine would sequestrate about 1 Pg CO2 per Pg olivine from which about 8% are caused by changes in the biological pumps (increase export of organic matter, decreased export of CaCO3). The chemical impact of open ocean dissolution of olivine (the increased alkalinity input) is therefore less efficient than dissolution on land, but leads due to different chemical impacts to a higher surface ocean pH enhancement to counteract ocean acidification. We finally investigate open ocean dissolution rates of up to 10 Pg olivine per year corresponding to geoengineering rates which might be of interest in the light of expected future emission (e.g. A2 scenario with emissions rising to 30 PgC/yr in 2100 AD). Those rates would still sequestrate only less than 20% of the emission until 2100, but would require that the nowadays available shipping capacity of tankers and bulk carriers is entirely used for olivine dissolution ten times a year. Reference Köhler, P.; Hartmann, J. and Wolf-Gladrow, D. A. (2010) Geoengineering potential of artificially enhanced silicate weathering of olivine, Proceedings of the National Academy of Science 107, 20228-20233, doi: 10.1073/pnas.1000545107.

Köhler, P.; Abrams, J.; Völker, C.; Wolf-Gladrow, D. A.; Hartmann, J.

2012-04-01

299

Effects of anneal, grain size and water content on deformation of olivine at subduction zone conditions  

NASA Astrophysics Data System (ADS)

Experimental study regarding to the effects of annealing process, grain size and water content on the deformation of polycrystalline San Carlos olivine has been performed at 3 GPa pressure with temperatures between 400 and 1000 C at a D-DIA facility at X17B2, NSLS. The total macroscopic strain is derived from the direct measurements of the images taken by X-ray radiograph technique. The differential stresses are deduced from elastic strains, which are calculated from olivine elastic properties. The experiments are preformed at constant strain rates of ~10-5-10-7s-1. Both annealed and unnannealed olivine samples exhibit a strain rate and temperature independent regime until a critical temperature where the olivine substantially softens. The annealed samples experience this softening process at temperatures as much as 370°C lower than the annealed samples. Grain size affects the rheological properties of olivine in the low temperature dislocation regime. Existence of water decreases the transition temperature of the boundary between the regimes of low temperature plasticity and power-law creep. The thermal softening of the unannealed samples could be the trigger of deep focus earthquakes in zones that were damaged by previous events.

Long, H.; Weidner, D. J.; Li, L.

2009-12-01

300

Valence State Partitioning of Vanadium Between Olivine-Melt in Olivine-Phyric Martian Basalts. Defining the fO2 of the Martian Mantle.  

NASA Astrophysics Data System (ADS)

Several recent studies have demonstrated that the fO2 in martian basalts varies by 2 to 3 log units and is correlated with geochemical parameters such as LREE/HREE, initial 87Sr/86Sr, and initial d. These correlations have been interpreted to indicate the presence of reduced, incompatible element-depleted and oxidized, incompatible element-enriched reservoirs that were produced during early stages of martian differentiation. Olivine-phyric basalts represent the closest approximation of primary martian basalts in the meteorite collection. Therefore, gaining a better understanding of the fO2 and incompatible element characteristics of the earliest phase (olivine) in these basalts may provide a clearer view into the martian mantle. Using the bulk composition of Yamato 980459 (an olivine-phyric basaltic melt composition), we conducted a series of near-liquidus experiments to determine the partitioning of V between olivine-melt at fO2 conditions between QFM and IW-1. XANES analyses of the glass indicate that the V4+/V3+ varies systematically with redox conditions of the experiments. SIMS analyses of V in glass and olivine indicated a systematic increase in DVol/melt from approximately 0.055 at QFM to approximately 0.5 at IW-1. This is consistent with the observed variation in V4+/V3+ measured in the glass by XANES and the crystal chemical preference of the olivine octahedral site for V3+ rather than V4+. Applying this oxybarometer calibration to well-defined lunar (IW-1) and terrestrial basaltic systems (QFM+0.2, Makaopuhi lava lake, Hawaii) indicate that it is vary robust over a wide range of planetary fO2 conditions. The determination of DVol/melt and incompatible element abundance using SIMS from martian olivine-phyric basalts indicate that they crystallized over a rather broad range in fO2 (IW+0.2 to IW+2) and from basaltic magmas with a range of incompatible element enrichments. These data indicate that correlations among these geochemical parameters are fundamental characteristics of the closest approximations of primary martian magmas. These signatures were not incorporated into the basaltic magmas during crystallization or involved late-stage processes. This suggests that if assimilation of martian crust by reduced, mantle derived magmas was an important mechanism for producing this array, assimilation occurred prior to the crystallization of any of the olivine now in these olivine-phyric shergottites. Thus the assimilation must have occurred at the base of the martian crust and all mineralogical evidence of assimilation was removed during transport to the martian surface. It appears more-likely that rather than assimilation, these arrays represent different mantle sources. This has substantial implications for the dynamics of a martian mantle that maintained two distinctly different reservoirs that were formed during initial martian differentiation at 4.5 Ga.

Shearer, C.; McKay, G.; Papike, J.; Karner, J.; Sutton, S.

2005-12-01

301

The olivine-wadsleyite phase transformation in mantle peridotite  

NASA Astrophysics Data System (ADS)

One of the most important goals in the study of the olivine (?) - wadsleyite (?) transformation is to understand the seismic discontinuity observed near the depth of 410 km in the Earth’s mantle. Although one school of thought attributes this discontinuity to radical chemical changes from lherzolite to picritic eclogite[1], the ?-? transformation in an isochemical peridotitic mantle has widely been accepted as the underlying cause. If the latter interpretation is valid, the composition and temperature can be inferred by the depth and magnitude of the discontinuity, providing useful information for understanding the present state of the Earth’s transition zone. In spite of extensive experimental investigations of this transformation, most studies were conducted in the simple system Mg2SiO4-Fe2SiO4 and/or using the quenching technique[2]. No efforts have been directed to study the kinetic barrier of the ?-? transformation under normal mantle conditions. In addition, recent studies have demonstrated increasing needs for the study of the ?-? transformation in multi-component systems relevant to the Earth’s mantle[3,4]. We choose the KLB-1 spinel lherzolite, a xenolith from Kilborne Hole Crater in New Mexico USA, as starting material because it represents one of the most undepleted mantle compositions. The high P-T x-ray diffraction experiments were conducted using a two-stage multi-anvil press on beamline 13-BM-D of Advanced Photon source, Argonne National Laboratory. Phase identifications were made by observing the first appearance of a phase that was absent in the starting sample and by closely monitoring complete disappearance of a low-pressure phase from the assembly. In the presence of both ? and ? phases, transformation direction was identified by observing a significant change in the relative intensity between the two phases. Our results demonstrate the experimental feasibility of studying ?-? transformation in complex systems and of resolving pressure differences of less than 0.4 GPa for the two-phase loop, even with the effect of kinetic barrier being taken into account. References: [1] Anderson and Bass, Nature 320, 321, 1986; [2] Katsura and Ito, J. Geophys. Res. 94, 15663, 1989; [3] Stixude, J. Geophys. Res. 102, 14835, 1997; [4] Irifune and Isshiki, Nature 392, 702, 1998.

Zhang, J.; Zhao, Y.; Wang, L.; Wang, Y.

2009-12-01

302

High pressure and temperature fabric transitions in olivine and variations in upper mantle seismic anisotropy  

NASA Astrophysics Data System (ADS)

Crystallographic preferred orientation (CPO) of olivine, which is developed by dislocation creep, controls the seismic anisotropy in the upper mantle. Strong seismic anisotropy observed in the oceanic lithosphere decreases monotonically with depth, and it rapidly decreases below 200 km depth (e.g., Montagner and Kennett, 1996; Montagner, 1998). The low seismic anisotropy in the deep upper mantle has been attributed to the transition from dislocation to diffusion creep (Karato, 1998) or the development of an olivine CPO with low seismic anisotropy (Courvy et al., 2004; Mainprice et al., 2005). It has recently been reported that the easiest slip system in olivine changes depending on pressure (Raterron et al., 2007; 2009), suggesting a pressure-induced transition of CPO type in olivine. However, the effect of pressure on the CPO patterns of olivine has been controversial: Simple-shear deformation experiments on olivine aggregates at 11 GPa and 1673 K using stress-relaxation techniques show that C-type fabric (developed by the (100)[001] slip system) can be developed in the deep upper mantle (Courvy et al., 2004). However, their experiments were conducted under wet conditions (289-2248 ppm H/Si of water in olivine), and some authors pointed out that the development of C-type fabric is due to the water effect (e.g., Jung et al., 2009). More recently, a series of simple-shear deformation experiments reported a pressure-induced fabric transition in olivine from A-type (developed by the (010)[100] slip system) to B-type (developed by the (010)[001] slip system) at 3 GPa under dry conditions (e.g., Jung et al., 2009), while deformation experiments on orientated single crystals of olivine showed a change of the dominant slip direction from b = [100] to [001] at higher pressures (5-7 GPa) under dry conditions (Raterron et al., 2007; 2009). Therefore, further extensive studies are needed to clarify the effects of pressure and temperature on the CPO of olivine under the upper mantle conditions. We have conducted simple-shear deformation experiments on olivine aggregates at pressures P = 2.1-7.6 GPa, temperatures T = 1493-1673 K, and shear strain rates of 1.5-7.5×10-5 s-1 under dry conditions using a deformation-DIA apparatus with the MA-6-6 system (Nishiyama et al., 2008). We found that the rapid decrease in seismic anisotropy is caused by the fabric transition from A-type to B-type-like fabric at 7.6 GPa. Temperature dependencies of the CPO patterns of B-type-like fabrics developed at 7.6 GPa were also observed. The fabric transition occurring at 7.6 GPa result in low seismic anisotropy at greater depths, consistent with seismological observations. Thus, the variations of CPO with pressure and temperature in olivine under dry conditions can explain the seismic anisotropy signatures observed in the upper mantle, without invoking other mechanisms.

Ohuchi, T.; Kawazoe, T.; Nishihara, Y.; Nishiyama, N.; Irifune, T.

2010-12-01

303

Effect of a Si-rich layer on olivine carbonation under in-situ conditions  

NASA Astrophysics Data System (ADS)

Mineral carbonation, a geochemical reaction between Mg-, Fe-, and Ca-silicate minerals and dissolved carbon dioxide (CO2), results in the long-term, stable storage of CO2 as carbonate minerals. Although the reaction is thermodynamically favored and occurs naturally, the kinetics are typically slow at temperatures < 100°C and thus limit industrial applications of the process. This study presents the results of a series of batch reactions designed to further understand the kinetics and mechanism of olivine carbonation in a three-phase system (water, solid, and supercritical CO2) at conditions relevant to in-situ¬ carbonation (60°C, 100 bar CO2 pressure, water:solid of 20:1 to 50:1, pH 3-6 ). Twin Sisters (OR) olivine ((Mg0.85 Fe0.15)2SiO4) was chosen as the reactive silicate mineral because olivines are abundant and undergo carbonation in nature. The carbonation of olivine in the presence of water and supercritical CO2 proceeds via dissolution of the starting mineral and CO2, followed by precipitation of secondary phases. Two secondary phases are relevant to this study. The first is Mg-carbonate (magnesite, MgCO3), the desired reaction product because it sequesters CO2 for geologic time scales. The second is amorphous silica (SiO2), a side-product that increases the total volume of solids in the system but does not interact with CO2. Because the solubility of silica is much less than that of Mg-carbonate at <100°C, silica reaches thermodynamic saturation first. The present study shows that the rate of olivine dissolution depends on the saturation state of amorphous silica and decreases by up to two orders of magnitude (from 10-11 to 10-13 mol cm-2 s-1) as saturation is approached. This observed effect is likely due to formation of a Si-rich layer on olivine grain surfaces after exposure to acidic solution, observed by x-ray photoelectron spectroscopy. The initial olivine dissolution is incongruent over the timeframe of several hours as shown by solution compositions determined by ICP-AES, but becomes congruent over longer periods. This behavior has been noted by others. We hypothesize that when in contact with an aqueous solution at saturation with respect to silica, the Si-rich layer will significantly lower Mg diffusion as well as the dissolution rate of olivine. The net effect is thus an apparent olivine dissolution rate of near zero for time periods ranging from 1 to 20 days. After this period the measured olivine dissolution rate increases, indicating that the Si-rich layer is no longer plays a role in passivating the surface. We hypothesize that as the surface area of secondary silica increases, there is an increasing movement of SiO2 from the olivine surface layer to physically separate secondary silica particles. We conclude that the rate of olivine carbonation under the conditions of our experiments depends strongly on SiO2 saturation and that this effect must be mitigated for a commercially viable Mg-silicate carbonation process.

Johnson, N. C.; Thomas, B.; Rosenbauer, R. J.; Maher, K.; Brown, G. E.

2011-12-01

304

Unusual olivine and pyroxene composition in interplanetary dust and unequilibrated ordinary chondrites  

NASA Astrophysics Data System (ADS)

The presence, in both a number of interplanetary dust particles (IDPs) and in meteorite matrices, of olivine and orthopyroxene grains, low in FeO but containing up to 5 wt pct MnO, is reported. The majority of olivines and pyroxenes in meteorites contain less than 0.5 wt pct MnO. The presence of these low-iron, manganese-enriched (LIME) olivines and pyroxenes in IDPs and meteorites may indicate a link between the origin and history of IDPs and the matrix material of primitive meteorites. The origin of the LIME silicates could be explained by condensation from a gas of solar composition. Forsterite is the first major silicate phase to condense from a solar nebula gas, and Mn, which is not stable as a metal under solar nebula conditions, would condense at about 1100 K as Mn2SiO4 in solid solution with forsterite.

Klock, W.; Thomas, K. L.; McKay, D. S.; Palme, H.

1989-05-01

305

The Effect of Trace H2O on the Mechanisms of the Olivine-Ringwoodite Transformation  

NASA Astrophysics Data System (ADS)

The existence of metastable olivine has been inferred as a possible trigger of deep focus earthquakes. Because hydrogen increases olivine-ringwoodite transformation rates, the existence of metastable olivine in the transition would require the subduction of very dry olivine. Our previous work has shown that for San Carlos olivine spheres, hydrated in a piston cylinder with 75 ppm H2O and 300 ppm D2O, ringwoodite-rim growth rates are greatly enhanced relative to anhydrous samples (Du Frane2010 and Diedrich et al, 2009). In anhydrous samples, rim-growth rates decrease with time as elastic strain builds up in the system, eventually stopping the reaction. As strain increases, wadsleyite forms, rather than or in addition to ringwoodite. In hydrous samples, hydrogen partitions to the ringwoodite growth rim, hydrolytically weakening it, and preventing the build up of elastic strain energy. Eventually, elastic strain energy may build up in slightly hydrous samples if the hydrogen content of the rim decreases sufficiently. Here we investigate the transformation mechanisms in the same San Carlos olivine samples, hydrated to 75 and 300 ppm H2O and D2O and transformed at 18 GPa. A 75-ppm-H2O sample run at 1100°C for 40 minutes shows a complex mixture of reaction textures. Optical microscopy and Raman spectroscopy show that the ringwoodite rims are nearly pure ringwoodite with minor amounts of wadsleyite. Scanning electron microscopy and transmission electron microscopy on a Focused Ion Beam slices of this sample show that the outermost rim is uniform, relatively course grained and defect free ringwoodite. This suggests limited nucleation at the sample-capsule interface and fairly rapid incoherent growth. The inner rim consists of a complex mixture of olivine and ringwoodite in which most of the ringwoodite has no crystallographic relationship to the host olivine and therefore represents incoherent nucleation and growth. Coherent ringwoodite lamellae are also present in the inner rim and the olivine core. These have the same crystallographic relation to olivine ([001]Ol || <110>Rg and (100)Ol || {111}Rw) as seen in previous studies (Kershhofer et al 1996). In the core of the olivine spheres, backscatter electron images show thin ringwoodite lamellae and numerous ringwoodite inclusions that are presumably incoherent. Unlike anhydrous samples, which generally contain wadsleyite inclusions, our Raman data indicate that hydrous samples have little intra-crystalline wadsleyite. Some of the ringwoodite inclusions are grouped into linear arrays that suggest heterogeneous nucleation on pre-existing defects such as tilt boundaries. The presence of 75 ppm H2O appears to enhance heterogeneous nucleation and the growth rates of coherent lamellae and incoherent inclusions. These results imply that small amounts of H2O in olivine enhance the transition to ringwoodite by increasing intra-crystalline nucleation and growth rates as well as by increasing rim-growth rates.

Sharp, T. G.; Rieck, K. D.; Hu, J.; Du Frane, W. L.

2011-12-01

306

Elasticity of the olivine and spinel polymorphs of Ni 2 SiO 4  

Microsoft Academic Search

The single-crystal elastic moduli, cij x, of the olivine (a) and spinel (?) polymorphs of nickel orthosilicate have been measured at atmospheric pressure and 20° C by Brillouin spectroscopy. The results are (Mbar), Ni2SiO4 olivine: c11=3.40(2), c22=2.38(2), c33=2.53(2), c44=0.71(1), c55=0.87(1), c66=0.78(1), c12=1.09(2), c13=1.10(4), c23=1.13(3), Ni2SiO4 spinel: c11=3.66(3), c44=1.06(1), c12=1.55(3). In comparing these results with extant elasticity data for olivine- and

Jay D. Bass; Donald J. Weidner; N. Hamaya; M. Ozima; S. Akimoto

1984-01-01

307

Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt.  

PubMed

Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg(2-2x)Fe(2x)SiO(4)) has been done for the protoplanetary disk HD?100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x???0.29). In the cold outskirts of the ??Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of ??Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01?±?0.001) and show that they make up 3.6?±?1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though ??Pictoris is more massive and more luminous and has a different planetary system architecture. PMID:23038467

de Vries, B L; Acke, B; Blommaert, J A D L; Waelkens, C; Waters, L B F M; Vandenbussche, B; Min, M; Olofsson, G; Dominik, C; Decin, L; Barlow, M J; Brandeker, A; Di Francesco, J; Glauser, A M; Greaves, J; Harvey, P M; Holland, W S; Ivison, R J; Liseau, R; Pantin, E E; Pilbratt, G L; Royer, P; Sibthorpe, B

2012-10-01

308

Deuterium-hydrogen exchange in olivine: Implications for point defects and electrical conductivity  

NASA Astrophysics Data System (ADS)

Knowledge about hydrogen self diffusion (DH) is critical for determining mantle hydrogen distribution and understanding point defects. Also, chemical diffusion of hydrogen in olivine, such as redox exchange with polarons (DRedox), depends on DH. In this study deuterium 2H was exchanged into hydrogen 1H saturated single crystals of San Carlos olivine between 750 and 900°C at 2 GPa. We measured and fit the resulting 2H profiles to obtain DH,[100] = 10(-4.9±1.4)*e(-140±30kJ/mol)/(RT) m2/s, which is ˜1 log unit lower than DRedox,[100], with similar activation enthalpy Ha. By comparing these two diffusion coefficients, we estimate the small polaron diffusion coefficient. Additionally, we estimate DH in the [010] and [001] orientations, demonstrating that DH is highly anisotropic in olivine. These DHvalues were used with the Nernst-Einstein relation to estimate the electrical conductivity by hydrogen in olivine (?H = 101.1*e(-130kJ/mol)/(RT) S/m for 10-2 wt % H2O) that is lower in magnitude than previous measurements. Our results suggest that hydrogen alone cannot account for high electrical conductivity anomalies observed at asthenospheric depths (˜10-2 to ˜10-1 S/m). The maximum anisotropic variation of DH and ?Hin olivine is ˜2 log units between 750 and 900°C and increases when extrapolated to higher temperature (˜3.3 at 1400°C). Anisotropy observed in the mantle may indicate substantial amounts of hydrogen in olivine with lattice-preferred orientation.

Du Frane, Wyatt L.; Tyburczy, James A.

2012-03-01

309

Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt  

NASA Astrophysics Data System (ADS)

Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg2-2xFe2xSiO4) has been done for the protoplanetary disk HD100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x~0.29). In the cold outskirts of the ?Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of ?Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01+/-0.001) and show that they make up 3.6+/-1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though ?Pictoris is more massive and more luminous and has a different planetary system architecture.

de Vries, B. L.; Acke, B.; Blommaert, J. A. D. L.; Waelkens, C.; Waters, L. B. F. M.; Vandenbussche, B.; Min, M.; Olofsson, G.; Dominik, C.; Decin, L.; Barlow, M. J.; Brandeker, A.; di Francesco, J.; Glauser, A. M.; Greaves, J.; Harvey, P. M.; Holland, W. S.; Ivison, R. J.; Liseau, R.; Pantin, E. E.; Pilbratt, G. L.; Royer, P.; Sibthorpe, B.

2012-10-01

310

Olivine Composition of the Mars Trojan 5261 Eureka: Spitzer IRS Data  

NASA Astrophysics Data System (ADS)

The largest Mars trojan, 5261 Eureka, is one of two prototype "Sa" asteroids in the Bus-Demeo taxonomy [1]. Analysis of its visible/near-IR spectrum [2] led to the conclusion that it might represent either an angritic analog or an olivine-rich composition such as an R chondrite. Spitzer IRS data (5-30 ?m) have enabled us to resolve this ambiguity. The thermal-IR spectrum exhibits strong olivine reststrahlen features consistent with a composition of ? Fo60-70. Laboratory spectra of R chondrites, brachinites, and chassignites are dominated by similar features.

Lim, L. F.; Emery, J. P.; Mueller, M.; Rivkin, A. S.; Trilling, D.; Burt, B. J.

2011-10-01

311

Electrically driven green, olivine, and amber color nanopyramid light emitting diodes.  

PubMed

We report the fabrication and studies of electrically driven green, olivine, and amber color nanopyramid GaN light emitting diodes (LEDs). InGaN/GaN multiple quantum wells (MQWs) were grown on the nanopyramid semipolar facets. Compared with the commonly used (0001) c-plane MQWs, the semipolar facet has lower piezoelectric field, resulting in much faster radiative recombination efficiency. This is important for high In content MQWs. The measured internal quantum efficiencies for green, olivine, and amber color LED are 30%, 25%, and 21%, respectively. The radiative and non-radiative lifetime of the semipolar MQWs are also investigated. PMID:24104218

Chang, Shih-Pang; Chang, Jet-Rung; Sou, Kuok-Pan; Liu, Mei-Chun; Cheng, Yuh-Jen; Kuo, Hao-Chung; Chang, Chun-Yen

2013-10-01

312

Deformation of Olivine Under High Pressure and High Temperature Using a Rotational Drickamer Apparatus  

NASA Astrophysics Data System (ADS)

Although many experimental studies have been performed on olivine deformation, two major issues remain controversial. They include the pressure dependence of deformation (activation volume, V*) and the pressure dependence of deformation fabrics. The rotational Drickamer apparatus (RDA) is ideal for making direct measurements of olivine rheological properties and deformation fabrics at deep upper mantle conditions. We previously demonstrated the capability of the RDA for olivine and wadsleyite deformation, and are continuing our work on detailed observations of olivine deformation between 3 and 14 GPa. In the RDA, a ring-shaped sample with outer diameter of 1.6 mm is compressed between two opposed tungsten carbide anvils. After annealing at the desired conditions, shear deformation of the sample is achieved by rotating an upper anvil at a constant rate. Typically, RDA samples are deformed to strains of 0.6-0.7 at a strain rate of ~ 5 x 10-5 s-1. Under these conditions, olivine reaches steady-state stress by a strain of ~ 0.2. Shear and uniaxial stresses were calculated using d-spacing of (130) calculated from in-situ X-ray diffraction at 6 different azimuth angles. In addition, stress is estimated from dislocation density in the recovered olivine sample. The steady state shear stress for olivine estimated by these two methods agree within the experimental errors and is 1.8 ± 0.3 GPa at 11 GPa and 1800 K. To make RDA measurements that are relevant to Earth, it is important to reduce sample stress and minimize the uniaxial stress component related to extrusion during shear deformation. Our ongoing efforts are focused on reducing stress in the deformed sample. Our initial approach is to develop an assembly that is stable to T ? 2000 K for long-duration, high-strain experiments, with minimal sample extrusion during shear deformation. These goals have been achieved by developing a hot-pressed, porous sintered diamond sample holder. The porosity of the sintered diamond is critical to allow sample pressurization, but at high pressures the compressed diamond layer is strong enough to stabilize the sample assembly. The improved RDA assembly has been used for deformation experiments on olivine at ~ 14 GPa and ~ 2000 K. In these experiments, the sintered diamond sample holder supports the TiC+Diamond disc heaters to allow stable heating during deformation. The strong sample holder also reduces sample extrusion during shear deformation, which is the main cause of high uniaxial stresses observed in real-time experiments.

Kawazoe, T.; Tinker, D.; Karato, S.; Jing, Z.; Mookherjee, M.

2006-12-01

313

Seismic Evidence for Olivine Phase Changes at the 410- and 660-Kilometer Discontinuities  

NASA Astrophysics Data System (ADS)

The view that the seismic discontinuities bounding the mantle transition zone at 410- and 660-kilometer depths are caused by isochemical phase transformations of the olivine structure is debated. Combining converted-wave measurements in East Asia and Australia with seismic velocities from regional tomography studies, we observe a correlation of the thickness of, and wavespeed variations within, the transition zone that is consistent with olivine structural transformations. Moreover, the seismologically inferred Clapeyron slopes are in agreement with the mineralogical Clapeyron slopes of the (Mg,Fe)2SiO4 spinel and postspinel transformations.

Lebedev, Sergei; Chevrot, Sébastien; van der Hilst, Rob D.

2002-05-01

314

Reaction-induced fracturing during olivine serpentinization: A mechanistic investigation at the interface scale  

NASA Astrophysics Data System (ADS)

Serpentinization of the Earth's impermeable upper mantle is one of the most fundamental metamorphic hydration reactions. It governs lithospheric weakening, geochemical subduction zone input and possibly even the formation of life-essential building blocks. Serpentinization relies on fluid pathway generation due to low initial permeability and the large positive solid volume change associated with hydration. Although these pathways can be produced as a tectonic stress response, there is substantial evidence that the volume increase during olivine serpentinization itself generates stresses sufficient to fracture the rock. Nonetheless, the actual fracturing mechanism during olivine serpentinization is largely unexplored. Unconstrained batch experiments (Okamoto et al. 2011, this study) produce comparable hierachial fracture patterns to those found in natural samples demonstrating that no external forces (e.g., tensile stress) are required for fracturing to take place. Combining this with the observation that fluid-mediated mineral replacement advances via an interface-coupled dissolution-reprecipitation mechanism (e.g., Putnis 2009) without solid-state diffusion into the dissolving mineral indicates that classical (stress) corrosion cracking mechanisms cannot describe fracturing during olivine serpentinization. By uniting micro- and nanostructural characteristics ubiquitous to serpentinized olivine grains with a coupled diffusion-reaction-deformation model and crack growth theory this study explores the sub-critical fracturing mechanism at the interfacial scale. We present a new multistep reaction process and test the feasibility of a molecular wedge-assisted fracturing mechanism based on the following ubiquitously identified features: (1) no rotation of grain domains during fragmentation, (2) isotropic fracture orientation distribution with a uniform average width of individual finite length serpentine veins, (3) cumulative fragment area distribution with a log-normal scaling behavior following a hierachical fracturing model, (4) etch pit development at olivine-lizardite reaction interfaces, (5) crack initiation at these surface perturbations and (6) amorphous layer formation during olivine dissolution prior to serpentine nucleation (e.g., Rumori et al. 2004). Based on these observations we propose an entirely self-propagating reaction-driven fracturing process, where fractures nucleate at dissolution-induced surface perturbations assisted by a molecular wedge of amorphous 'gel', followed by further olivine dissolution and serpentine (±brucite) reprecipitation coupled with the force of crystallization. This process results in the observed hierarchical fracture network. Our results suggest that the mechanical force needed to advance serpentinization at the grain-scale does not rely on external forces but is due to interface-coupled, chemomechanical feedback during olivine re-equilibration in the presence of a fluid phase. Nevertheless, the influence of tectonic forces will need to be accounted for at larger scales.

Plümper, O.; Røyne, A.; Malthe-Sørenssen, A.; King, H. E.; Jamtveit, B.

2012-04-01

315

Genesis of ilmenite rods and palisades along humite-type defects in olivine from Alpe Arami  

NASA Astrophysics Data System (ADS)

Rod-shaped ilmenite inclusions in olivine have been observed in numerous peridotite lenses of the Adula-Cima Lunga unit, Central Alps. The rods are elongated parallel to [010]ol and identical in size, shape and concentration to those reported from garnet peridotite at Alpe Arami (AA). TEM investigation of the rods at AA, Cima di Gagnone (CDG) and Monte Duria (MD) demonstrates that the titanate inclusions correspond to a Mg-bearing ilmenite with exclusively a trigonal crystal structure. No other FeTiO3 polymorphs have been identified. The shape of the ilmenite inclusions concurs with minimum topotactic misfits between the lattices of olivine and Mg-bearing ilmenite. Optical microscopy reveals that the ilmenite rods are not randomly distributed within olivine but have, at all localities, a preferred alignment parallel to (001)ol, forming palisades. TEM images of the ilmenite palisades at AA and CDG show that they are controlled by the presence of (001) planar defects in olivine along which the rods nucleated. The defects have been characterised by high-resolution TEM and identified as 4.4 Å-wide humite-type layers, i.e. (Mg2SiO4).Mg(OH,F)2, intergrown within olivine. In such layers substitution of up to 50 mol% MgH2 by Ti4+ is possible. Assuming Ti-saturated humite slabs, the maximum density of (001) faults observed at AA, approximately 1900 mm-1, can accommodate about 170 ppm TiO2 in olivine. This represents about half the values obtained by UV-laser ablation ICP-MS and EMPA analysis. Evidence for annealing of the defects, however, suggests that only parts of the defects are still preserved. The formation of ilmenite rods is considered to be a consequence of the breakdown of isolated humite layers in olivine. The apparent TiO2 content in olivine at AA, CDG and MD is regarded as a function of the Ti-humite defect density.

Risold, A.-C.; Trommsdorff, V.; Grobéty, B.

2001-02-01

316

Genesis of ilmenite rods and palisades along humite-type defects in olivine from Alpe Arami  

NASA Astrophysics Data System (ADS)

Rod-shaped ilmenite inclusions in olivine have been observed in numerous peridotite lenses of the Adula-Cima Lunga unit, Central Alps. The rods are elongated parallel to [010]ol and identical in size, shape and concentration to those reported from garnet peridotite at Alpe Arami (AA). TEM investigation of the rods at AA, Cima di Gagnone (CDG) and Monte Duria (MD) demonstrates that the titanate inclusions correspond to a Mg-bearing ilmenite with exclusively a trigonal crystal structure. No other FeTiO3 polymorphs have been identified. The shape of the ilmenite inclusions concurs with minimum topotactic misfits between the lattices of olivine and Mg-bearing ilmenite. Optical microscopy reveals that the ilmenite rods are not randomly distributed within olivine but have, at all localities, a preferred alignment parallel to (001)ol, forming palisades. TEM images of the ilmenite palisades at AA and CDG show that they are controlled by the presence of (001) planar defects in olivine along which the rods nucleated. The defects have been characterised by high-resolution TEM and identified as 4.4 Å-wide humite-type layers, i.e. (Mg2SiO4).Mg(OH,F)2, intergrown within olivine. In such layers substitution of up to 50 mol% MgH2 by Ti4+ is possible. Assuming Ti-saturated humite slabs, the maximum density of (001) faults observed at AA, approximately 1900 mm-1, can accommodate about 170 ppm TiO2 in olivine. This represents about half the values obtained by UV-laser ablation ICP-MS and EMPA analysis. Evidence for annealing of the defects, however, suggests that only parts of the defects are still preserved. The formation of ilmenite rods is considered to be a consequence of the breakdown of isolated humite layers in olivine. The apparent TiO2 content in olivine at AA, CDG and MD is regarded as a function of the Ti-humite defect density.

Risold, A.-C.; Trommsdorff, V.; Grobéty, B.

2000-11-01

317

Deformation of olivine-orthopyroxene aggregates: Implications for the strength of the lithosphere  

NASA Astrophysics Data System (ADS)

In order for plate tectonics to occur on Earth, the base of the oceanic lithosphere must be relatively weak ("yield stress" less than ~200 MPa). Such a weak layer is not consistent with a model where homogeneous deformation of pure olivine by dislocation creep is assumed. Previous studies on orthopyroxene (opx) showed (i) opx (with certain orientations) has much lower strength than olivine at low temperature and (ii) recrystallized grain-size of opx is smaller than that of olivine. These observations suggest that opx might play an important role in reducing the strength of an olivine + opx mixture at lithospheric conditions. To explore this idea, we have started a series of experimental studies to investigate the rheological behavior of olivine + opx mixtures. The rheology of a synthetic coarse-grained aggregate (oli: 75%, opx: 25%), was explored at high confining pressure (1.5 GPa) in the Griggs-type apparatus to avoid opx transformation to proto-enstatite. The range of temperature was 900 - 1200C and deformation experiments were (nearly) constant strain-rate. In the first stage, relatively dry San Carlos olivine powders were encapsulated in nickel and hot-pressed in the Griggs apparatus at 1300C and 1.3 GPa for 7.5 hours to promote grain growth. A nearly homogeneous grain-size of 10 - 50 ?m was obtained (to ensure dislocation creep during deformation). The hot-pressed pellet was subsequently cut into thin slices, 400 ?m thick. Each slice was sandwiched between two grooved alumina pistons and again placed in a nickel capsule. The pressure medium used in these experiments was CsCl, which reduced friction considerably (in comparison to e.g. MgO) and provided a clear indication of the 'hit point' and improved stress estimation. At 1200C CsCl was mixed with MgO to minimize persuasive melting of the salt. Results have shown that the olivine - opx aggregate began to deform above 900C at high pressure. At 1000C deformation was accompanied by the onset of dynamic recrystallisation on the boundaries of parent grains. At 1100C, the degree of recrystallization increased with deformation becoming increasingly concentrated on grain boundaries near parallel to the orientation of the strain marker. In all experiments we have performed so far, the stress continuously increased with strain, and no evidence of weakening nor shear localization was observed. However, the degree of recrystallization systematically increased with temperature, and evidence for mixing of recrystallised orthopyroxene and olivine grains was observed. At higher temperature, higher water content and/or lower strain-rates, the influence of dynamic recrystallization will be more extensive.

Farla, R.; Cai, Z.; Karato, S.

2011-12-01

318

Surface destabilization and laboratory-induced non-stoichiometry in San Carlos olivine  

Microsoft Academic Search

Annealing experiments on natural olivine (Mg1-xFex)2SiO4 (with x˜0.11) crystals (San Carlos, Arizona, spinel-lherzolite context) have been performed between T=1,100° C and 1,500° C for oxygen partial pressures pO2=10-3 to 10-13 bar and times of 1 to 140 h in CO\\/CO2 or H2\\/H2O gas mixtures. Even specimens annealed within the T-pO2theoretical stability field (TSF) calculated for stoichiometric olivine (Nitsan 1974) show

O. Jaoul; B. Houlier; M. Cheraghmakani; R. Pichon; R. C. Liebermann

1987-01-01

319

Development of olivine Crystal Preferred Orientation in Oshima peridotite body as a remnant of oceanic lithosphere  

NASA Astrophysics Data System (ADS)

To know the mantle flow kinematics, investigation of the seismic anisotropy is common method in upper mantle. Anisotropy is linked to crystal preferred orientations (CPOs) of olivine which is most abundant and weakest mineral in upper mantle. However the quantitative investigation analyses of natural CPO data have not succeeded yet. So, we must understand how olivine CPOs develops with strain in deformation settings. The Oshima peridotite body is the lower part of the Yakuno ophiolite in SW Japan (Ishiwatari, 1985a, b). This body consists dominantly of dunite and harzburgite deformed in upper mantle. This peridotites display various microstructures such as coarse grained granoblastic texture (0.7-1.0mm), elongated porphyroclastic texture (1.0mm-) and fine grained equigranular texture (0.1mm-). We analyzed CPOs of olivine using EBSD method. The results show that CPOs of olivine was formed by (0kl)[100] or (010)[100] slip system. In order to characterize the CPOs, we first determined the fabric strength and orientation distribution density of the principal crystallographic axes (J-index and M-index; Tommasi et al., 2000 and Skemer et al., 2005). According to those studies with increasing monotonously strain, the value of J- and M-index also increases. The Oshima peridotite body shows the various fabric strength from J=2.95 to 16.26 (M=0.040 to 0.384). On this presentation, we propose a new inversion method of mantle deformation by matching the model CPO patterns with natural CPOs in the Alpine type peridotites. Furthermore, we investigated two kind of angles of olivine together with CPOs at the same time to analyze CPOs development during mantle deformation. There are; (1) Angles between slip plane of each olivine grain and sample lineation. (2) Misorientation angles between adjacent olivine grains. The different angles between the slip plane of olivine grains and the rock lineation (1) are controlled by lattice rotation due to dislocation glide (Sevillano et al., 1976). And the misorientation angles between neighboring grains (2) are governed by the local deformation kinetics involving dislocation climb process. From these two parameters (1) and (2) associated with strain, we can construct "gfabric distribution diagrams"h for deformed mantle rocks which can be compared to the J-index of the some samples. The more strain increases (=stronger fabrics), the more "gfabric distribution diagrams"h tends to concentrate. This study enables us to study together dislocation glide and recrystallization, which both contribute to CPO development.

Tasaka, M.; Toriumi, M.; Wataru, N.

2008-12-01

320

Shock-Induced Transformation Exsolution Lamellae in Olivine in Black Veins of the Mbale Meteorite  

NASA Astrophysics Data System (ADS)

Mbale is a shocked L6 chondrite [1]. Some shock-induced veins of 0.1 to 2 mm width intersect the meteorite. The veins consist of diaplectic plagioclase glass, unmelted silicate fragments including olivines and pyroxenes, and the shock-induced melt materials consisting of metal-troilite intergrowths, microcrystalline pyroxene and olivine, and silicate glass. Here we report the first finding of shock-induced exsolutions in olivine that appear as compositionally different lamellae which presumably formed at high pressure by inversion of olivine (alpha) to the beta+gamma polymorphs. Olivine compositions in the chondritic part of Mbale range from Fa(sub)22.5 to Fa(sub)26 (average Fa(sub)24). In contrast, the exsolved olivines in the shock-induced veins (30 to 100 mm in diameter) consist of alternating Fe-rich (Fa(sub)22-32) and Fe-poor (Fa(sub)9.9-18.5) lamellae that range in width from less than 0.5 micrometers to up to 10 micrometers. Each individual lamella actually consists of microcrystals of less than 0.5 micrometers in diameter with rather diffuse borders within the lamella. The lamellae occur in ~30 micrometer segments which were formed by faulting and displacement. Micro-Raman spectroscopy confirms that both types of exsolution lamellae currently have the olivine (alpha) structure. The partially melted veins of Mbale may have reached a post-shock peak temperature of 1473 K >= T <= 1873 K. Based on the phase diagrams of the olivine(alpha)-wadsleyite(beta)-ringwoodite(gamma) transformations in the system Mg(sub)2SiO(sub)4-Fe(sub)2SiO(sub)4 at 1473 K [2], olivine of composition ~Fa(sub)24 should exsolve at equilibrium conditionsins to beta- + gamma-phases at P >12.7 GPa, and transform to a single gamma-phase at >15 GPa. Figure 1 shows that the determined compositions of the Fe-rich and Fe-poor lamellae in Mbale match perfectly the compositions at the beta + gamma/gamma and the beta + gamma/beta phase boundaries, respectively. Since these grains depict well ordered lamellar structure displaced by several faults, the exsolution lamellae of olivine must have nucleated before faulting. TEM studies of ringwoodite in black veins in other shocked chondrites indicate that the original olivine has transformed into a mosaic of ringwoodite grains in nano-meter size range [3,4]. The observed lamellar structure in Mbale olivines is indicative of exsolution transformation from single grains before faulting of the olivines and definitely before solidification of the silicate melt to glass in the vein. We therefore consider it unlikely that the shock-induced olivine lamellae were produced via retrograde exsolution from gamma to gamma + beta. Our findings strongly suggest that the exsolutions were produced from an originally homogeneous olivine (alpha) by the following mechanism: Original homogenous olivine exsolved at P>12.7 GPa and 1473 K >=T <= 1873 K into Fe-poor beta- and Fe-rich gamma-phases possibly along [001] which is the predominant dislocation orientation in olivine during deformation [4,5]. The dislocations in olivine may have provided the nucleation sites for the beta- and gamma-phases due to their reduced activation barrier to nucleation. The grains were then faulted to several segments of 30 micrometers in diameter. A cooling rate of >= 260 K/s during the solidification of the shock-induced melt was estimated in the interval of 1223-1673 K, based on the metallic dendrite arm spacing or cell width of ~14 micrometers [6]. The cooling of the veins after the solidification of metal and silicate melts should have been much slower than 260 K/s because of the homogeneous Ni-concentration within the metallic dendrites. We interpret the survival of the lamellar structure as due to a nonlinear cooling rate: (1) very fast cooling after pressure release thus inhibiting obliteration of the lamellae by diffusion; followed by (2) slow cooling <1223 K thus leading to inversion of gamma and beta lamellae to alpha without chemical homogenization. References: [1] Jenniskens P. et al. (1994) Meteoritics ,

Chen, M.; Wopenka, B.; El Goresy, A.

1995-09-01

321

Role of Crustal Recycling in The Upwelling Mantle: Data on Olivines From OIBs, LIPs Basalts, Komatiites And MORBs  

Microsoft Academic Search

At pressures higher than around 2.5 GPa, subducted oceanic crust transforms to eclogite (clinopyroxene + garnet) with a free SiO2 phase. If recycled in the upwelling mantle this assemblage starts to melt at higher pressures than peridotite, producing high silica melt, which reacts with olivine from peridotite, producing olivine free garnet pyroxenite (Sobolev et al, Nature, 2005). The predicted geochemical

A. V. Sobolev; A. W. Hofmann; D. Kuzmin; G. Yaxley

2006-01-01

322

Sound velocities of hydrous olivine and the effects of water on the equation of state of nominally anhydrous minerals  

Microsoft Academic Search

Here we report the sound velocities and elastic constants of olivine containing 0.8 wt% H2O. We will also summarize some emerging trends on the effects of water on the equation of state of nominally anhydrous mantle minerals as they pertain to seismological observation. Olivine is thought to be the most abundant mineral in the mantle to a depth of 410

S. D. Jacobsen; F. Jiang; J. R. Smyth; T. S. Duffy; Z. Mao; C. M. Holl; D. J. Frost

2006-01-01

323

Analysis of the results of calibrating meteoritic olivine crystals with 238 U nuclei at the Bevalac accelerator  

Microsoft Academic Search

The results are presented of calibrating the sensitivity of olivine crystals from meteorites by the238U nuclei produced at the Bevalac accelerator. The comparative studies of the spectra of the etchable track lengths due to the238U nuclei and to “fossil” tracks in these olivines have shown that the group of the 210 µm “fossil” tracks observed in 1980 at the LNR,

V. P. Perelygin; S. G. Stetsenko; H. J. Crawford; T. J. M. Symons

1991-01-01

324

Electrical conductivity of magnesiowüstite\\/perovskite produced by laser heating of synthetic olivine in the diamond anvil cell  

Microsoft Academic Search

Samples prepared from synthetic single crystals of olivine have electrical conductivity that differs significantly from samples prepared, under similar conditions, from San Carlos olivine. In particular, the oxygen fugacity with which the sample was treated before being loaded into the laser-heated diamond anvil cell (LHDAC) has a large effect on the electrical conductivity of magnesiowüstite\\/perovskite assemblages synthesized from San Carlos

Al Duba; Jean Peyronneau; Fabrice Visocekas; Jean-Paul Poirier

1997-01-01

325

Reduced chromium in olivine grains from lunar basalt 15555 - X-ray Absorption Near Edge Structure (XANES)  

NASA Astrophysics Data System (ADS)

The oxidation state of Cr in 200-micron regions within individual lunar olivine and pyroxene grains from lunar basalt 15555 was inferred using X-ray Absorption Near Edge Structure (XANES). Reference materials had previously been studied by optical absorption spectroscopy and included Cr-bearing borosilicate glasses synthesized under controlled oxygen fugacity and Cr-doped olivines. The energy dependence of XANES spectral features defined by these reference materials indicated that Cr is predominantly divalent in the lunar olivine and trivalent in the pyroxene. These results, coupled with the apparent f(02)-independence of partitioning coefficients for Cr into olivine, imply that the source magma was dominated by divalent Cr at the time of olivine crystallization.

Sutton, S. R.; Jones, K. W.; Gordon, B.; Rivers, M. L.; Bajt, S.; Smith, J. V.

1993-01-01

326

Petrogenesis of augite-bearing ureilites Hughes 009 and FRO 90054\\/93008 inferred from melt inclusions in olivine, augite and orthopyroxene  

Microsoft Academic Search

Melt inclusions in ureilites occur only in the small augite- and orthopyroxene-bearing subgroups. Previously [Goodrich C.A., Fioretti A.M., Tribaudino M. and Molin G. (2001) Primary trapped melt inclusions in olivine in the olivine–augite–orthopyroxene ureilite Hughes 009. Geochim. Cosmochim. Acta65, 621–652] we described melt inclusions in olivine in the olivine–augite–orthopyroxene ureilite Hughes 009 (Hughes). FRO 90054\\/93008 (FRO) is a near-twin of

Cyrena Anne Goodrich; Anna Maria Fioretti; James Van Orman

2009-01-01

327

The behavior of Mg, Fe, and Ni during the replacement of olivine by orthopyroxene: experiments relevant to mantle metasomatism  

NASA Astrophysics Data System (ADS)

Replacement of olivine by orthopyroxene is a frequently observed phenomenon in mantle metasomatism. In order to study element redistribution in SiO2 metasomatism we synthesised orthopyroxene reaction rims at the contacts between forsterite-rich olivine and quartz. The orthopyroxene rims grew from the original quartz-olivine interface into both directions implying counterdiffusion of iron/magnesium and silicon. Following local equilibrium partitioning the XFe is lower in the orthopyroxene than in the reactant olivine at the olivine-orthopyroxene replacement front. The resulting local iron excess is compensated by formation of orthopyroxene with a higher XFe at the quartz-orthopyroxene interface, which is out of equilibrium with the reactant olivine. This is facilitated through short circuit diffusion along grain boundaries within the orthopyroxene rim. Due to the low capacity of orthopyroxene to accommodate Ni, this component is forced to diffuse back into the olivine producing a Ni enriched zone ahead of the replacement front. This leads to Ni contents in the orthopyroxene rim, which are higher than what is expected in equilibrium with the unaltered olivine. Taking quartz as a proxy for a silica rich fluid or liquid metasomatising agent, we conclude that the overall element fractionation between olivine and the silica rich phase may deviate from equilibrium partitioning so that the Fe and Ni concentrations in the orthopyroxene which is in contact with quartz are higher than in equilibrium with the reactant olivine. This indicates that kinetic fractionation is important for the chemical evolution of both the mantle rocks and the metasomatising agents.

Milke, Ralf; Abart, Rainer; Keller, Lukas; Rhede, Dieter

2011-11-01

328

The oxygen isotopic composition of olivine and pyroxene from CI chondrites  

Microsoft Academic Search

The CI chondrites are taken to represent average solar system material based on the similarity of their elemental compositions to that of the solar photosphere. However, their oxygen isotope geochemistry is dominated by secondary minerals that formed during aqueous alteration on the CI parent body. Precursors to this alteration, namely olivine and pyroxene, are extremely rare in CI chondrites, precluding

Laurie A. Leshin; Alan E. Rubin; Kevin D. McKeegan

1997-01-01

329

More on Nano-Particles in Olivine from the Northwest Africa 1950 Shergottite  

NASA Astrophysics Data System (ADS)

We analyzed olivine in NWA 1950 shergottite by an advanced TEM (FEI Titan 80-300) and found abundant nano-particles (1-20 nm). They are primarily Fe metal with minor hematite. The Fe metal formed by shock and probably altered to hematite by FIB.

Mikouchi, T.; Kasama, T.; Kurihara, T.

2011-03-01

330

Studying the pseudomorphic replacement of olivine by silica at acidic conditions  

Microsoft Academic Search

Silicification is an important reaction occurring in volcanic environments that aids the neutralisation of the extremely acidic fluids produced. Replacement of the original minerals by silica results in the reacting fluid becoming enriched in cations that can be subsequently transported through the hydrothermal system (Varekamp et al., 2000). In some examples olivine and pyroxene phenocrysts within the reacted layers are

Helen E. King; Thorsten Geisler; Andrew Putnis

2010-01-01

331

In situ Ultrasonic Velocity Measurements Across the Olivine-spinel Transformation in Fe2Si04  

SciTech Connect

Compressional (P) and shear (S) wave velocities across the olivine-spinel transformation in Fe{sub 2}SiO{sub 4} were investigated in situ using combined synchrotron X-ray diffraction, X-ray imaging, and ultrasonic interferometry up to 5.5 GPa along the 1173 K isotherm. The onset of the spinel to olivine transformation at 4.5 GPa and olivine to spinel transition for Fe{sub 2}SiO{sub 4} at 4.8 GPa was concurrently observed from X-ray diffraction, the amplitude of the ultrasonic signals, the calculated velocities, and the ratio of P and S wave velocities (v{sub P}/v{sub S}). No velocity softening was observed prior to the fayalite to spinel transition. The velocity contrasts across the Fe{sub 2}SiO{sub 4} spinel to fayalite phase transition are derived directly from the measured velocities, which are 13 and 12% for P and S waves, respectively, together with a density contrast of 9.4%. A comparison with literature data indicates that the changes in compressional-wave velocity and density across the olivine-spinel transformation in Fe{sub 2}SiO{sub 4} are comparable to those with different iron concentrations in the (Mg,Fe){sub 2}SiO{sub 4} solid solution, whereas the shear wave velocity contrast decreases slightly with increasing iron concentration.

Liu, Q.; Liu, W; Whitaker, M; Wang, L; Li, B

2010-01-01

332

Thermally modulated absorption of Fe2+ ions in micas, vivianite and olivine  

Microsoft Academic Search

The thermally modulated absorption (TMA) spectra of Fe ions in micas, vivianite and olivine have been measured in the visible and near infrared region at room temperature and they agree with the corresponding static absorption spectra. The micas show a strong negative TMA peak, located between 12000 cm-1 and 14000 cm-1, corresponding to Fe2+ to Fe3+ intervalence charge transfer and

E. Loh

1972-01-01

333

Effect of water on compressibility of San Carlos olivine and its implications  

Microsoft Academic Search

Water has been proved playing an important role in effecting physical properties of minerals. Previous studies have demonstrated that incorporating small amounts of water significantly reduce bulk moduli of wadsleyite and ringwoodite by 10% and 16% respectively (Yusa and Inoue, 1997; Inoue et al. 1998). Although olivine takes much smaller amount of water (10 times less) than wadsleyite and ringwoodite,

J. Chen; H. Liu; T. Yu; J. Hu

2005-01-01

334

Search for the Tracks of Heavy and Superheavy Cosmic Ray Nuclei in Olivines from Meteorites.  

National Technical Information Service (NTIS)

The results of investigating the tracks of cosmic nuclei with Z >= 50 in olivine crystals from meteorites are presented. The obtained spectrum of track lengths for the Z >= 50 nuclei exhibits two pronounced groups of tracks: 190-230 mu m tracks, attribute...

V. P. Perelygin S. G. Stetsenko G. N. Flerov

1985-01-01

335

Search for the tracks of galactic cosmic nuclei with Z> or = 110 in meteorite olivines  

SciTech Connect

The results of investigations of nuclear tracks from galactic cosmic rays in meteorite olivine crystals are presented. Among the identified tracks of nuclei with z> or =60, about 150 tracks are associated with the nuclei of the uranium group; the 365-mm-long track probably belongs to a nucleus with Z> or =110.

Perelygin, V.P.; Stetsenko, S.G.

1980-11-20

336

Deformation mechanisms of olivine single crystals compressed at 300 MPa and 800-1100°C  

NASA Astrophysics Data System (ADS)

Rheology of mantle rocks at lithospheric temperatures remains poorly constrained, since most experimental studies on creep mechanisms of olivine single crystals ((MgFe)2SiO4, Pbnm) and polycrystalline olivine aggregates were performed at high-temperatures (T >> 1200oC). In this study, we have performed deformation experiments on oriented single crystals of San Carlos olivine and polycrystalline olivine aggregate at temperatures relevant of the uppermost mantle (ranging from 800o to 1090oC) in tri-axial compression. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at various constant strain rates (from 7 × 10-6 s-1 to 1 × 10-4 s-1). Mechanical tests yield differential stresses ranging from 88 to 1076 MPa. All samples were deformed at constant displacement rate and for finite strains ranging from 4 to 23 %, to provide insight into possible effects of hardening, softening or stick-and-slip. The single crystals were compressed along several crystallographic directions to test the possibility of activating different slip systems (e.g. [100](001), [001](100), [001](010) and [100](010)). We will present the characterization of the dislocation microstructures performed in the TEM.

Cordier, Patrick; Demouchy, Sylvie; Mussi, Alexandre; Tommasi, Andrea

2013-04-01

337

Laminated olivine spinifex textures in the Mount Ayliff intrusion, South Africa  

Microsoft Academic Search

Summary A thin layer of spinifex troctolite occurs in the middle of the lherzolite unit of the Mount Ayliff Intrusion, South Africa. Olivine crystals reach 1 cm in length, have an aspect ratio up to 20, and lie parallel to the contact. This layer is considered to be intrusiveinto a pre-existing package of cumulates rather than to represent a layer

B. K. Sander; R. G. Cawthorn

1995-01-01

338

The fractionation of nickel between olivine and augite as a geothermometer  

Microsoft Academic Search

The coexisting olivine, clinopyroxene and glass of five samples collected from the Makaopuhi lava lake in Hawaii, at temperatures ranging from 1050 to 1160°C were analysed for nickel with an electron probe microanalyser. The results strongly suggest that the distribution of nickel between these three phase pairs well obeys the thermodynamic partition law, and that under favourable conditions, the distribution

T. A. Häkli; Thomas L. Wright

1967-01-01

339

The effect of many-body forces on the elastic properties of simple oxides and olivine  

Microsoft Academic Search

The single crystal elastic moduli bear evidence of non-central or many-body forces in the simple oxides with transition-metal oxides being very distinctive from alkaline-earth oxides. These features which persist in more complicated structures such as olivine, suggest that noncentral or many-body forces are important in defining the physical properties of these compounds as well.

Donald J. Weidner; Geoffery D. Price

1988-01-01

340

Deformation mechanism maps of olivine and rheology of the continental upper mantle  

Microsoft Academic Search

The reliability of straightforward extrapolation of the laboratory-determined constitutive equations to the upper mantle depends on good quality of experimental data as well as the activation of same deformation mechanism at the much lower natural strain rates and stress. Recent laboratory studies have provided more accurate flow law parameters for olivine under both dry and wet conditions, which allow us

Q. Wang

2009-01-01

341

Measurement of activation volume for creep of dry olivine at upper mantle pressure  

NASA Astrophysics Data System (ADS)

Olivine is the most abundant and weakest phase in the upper mantle, and thus its rheological properties have a critical role in controlling convective flow in this region. A resilient obstacle to understanding the behavior of olivine in the mantle has been the difficulty of determining activation volume (V*), the influence of hydrostatic pressure on flow strength. The bulk of previous studies examining V* were conducted at low pressure (<300 MPa) and small pressure ranges in gas-medium deformation apparatuses, limiting precision and raising questions about application to relevant geological conditions. For this study, we conducted deformation experiments on dry polycrystalline olivine in the D-DIA apparatus. The development of a new hybrid soft-fired pyrophyllite/mullite sample assembly allowed for a broadened pressure range (2-9 GPa), while stress and strain were measured in-situ with synchrotron x rays. Refinement in diffraction technique has allowed stress resolution of ±0.01 GPa. For the pressure range in this study, we have measured an average activation volume of about 17 cm^3/mol for dry polycrystalline San Carlos olivine. This is a substantial pressure effect, representing a pressure-induced viscosity increase of nearly 7 orders of magnitude from the base of the lithosphere to the bottom of the upper mantle.

Dixon, N. A.; Durham, W. B.; Suzuki, A. M.; Mei, S.; Kohlstedt, D. L.; Hustoft, J. W.

2011-12-01

342

Detection of iron containing crystalline olivines in the debris disk of beta-Pictoris  

NASA Astrophysics Data System (ADS)

We would like to present the results obtained from a Herschel PACS far-infrared spectrum of the debris disk of ? Pictoris. From the analysis of the 69? m band of crystalline olivine ( (Mg, Fe)2SiO4 ) and the Spitzer mid-infrared spectrum we have found that: - The grains are colder than expected (˜55 K vs ˜100 K expected from the bulk dust population) - Their composition is not purely magnesium rich. Which is contrary to what is concluded from detections in many other types of sources We can determine both the temperature and composition of the crystalline olivines grains because the position and shape of the 69? m band is sensitive to both. Looking at different kind of objects, from Young Stellar Objects to Asymptotic Giant Branch stars and Planetary Nebula, the crystalline olivines that are observed are always seen as pure forsterite (Mg2SiO4). It is the first time that crystalline olivine grains are found that contain 2-3% iron. This raises questions about the exact formation and origin of these minerals.

de Vries, B. L.; Acke, B.; Vandenbussche, B.; Waters, L. B. F. M.; Blommaert, J. A. D. L.; Waelkens, C.

2011-05-01

343

Short and Long-Term Olivine Weathering in Svalbard: Implications for Mars  

Microsoft Academic Search

Liquid water is essential to life as we know it on Earth; therefore, the search for water on Mars is a critical component of the search for life. Olivine, a mineral identified as present on Mars, has been proposed as an indicator of the duration and characteristics of water because it dissolves quickly, particularly under low-pH conditions. The duration of

E. M. Hausrath; A. H. Treiman; E. Vincenzi; D. L. Bish; D. Blake; P. Sarrazin; T. Hoehler; I. Midtkandal; A. Steele; S. L. Brantley

2008-01-01

344

Element partitioning between olivine and melt up to 10 GPa: Implications for the effect of pressure  

NASA Astrophysics Data System (ADS)

In order to investigate the effect of pressure on crystal-melt element partitioning, we have conducted partitioning experiments between olivine and coexisting peridotite melt up to 10 GPa determining minor and trace compositions using electron microprobe and laser-ablation inductively coupled plasma-mass spectrometry (ICP-MS). Partitioning data for monovalent and trivalent cations suggest a significant pressure effect. For monovalent cations, partition coefficients increase with pressure. In contrast, for trivalent cations, partition coefficients of smaller cations (Al, Ga) increase while those of large cations (Sc, REEs) decrease with pressure. To discuss the pressure effect on olivine-melt partitioning, data are interpreted using partition coefficient - ionic radii (PC-IR) diagrams, in conjunction with the lattice strain model. The results show that the optimum ionic radius (r0) and apparent Young's modulus (E) of the M-site in olivine both decrease with pressure. The decrease in r0 can be explained by compression of the M-site in olivine. In contrast, the observed decrease in E of the M-site (width of the parabola increases with pressure) cannot be explained by the pressure and temperature effects on the crystal structure. The apparent softening of a crystal site at high pressures is hard to reconcile with a change in crystal structure. We suggest that this effect may be explained by considering the change in structure of silicate melt at pressures that may increase the apparent "Young's modulus of the M-site in the melt".

Imai, Takamasa; Takahashi, Eiichi; Suzuki, Toshihiro; Hirata, Takafumi

2012-12-01

345

The distribution of olivine in the crater Aristarchus inferred from Clementine NIR data  

Microsoft Academic Search

Clementine imaged the Moon entirely at eleven wavelengths. This paper presents new results obtained on the crater Aristarchus using a heuristic method for the calibration of the near infrared (NIR) data set. We computed band ratios and we extracted spectra using a telescopic spectrum as reference. A new ~4×10km olivine rich area has been identified on the southeastern rim of

Stéphane Le Mouélic; Yves Langevin; Stéphane Erard

1999-01-01

346

Ultra-depleted primary melt included in an olivine from the Mid-Atlantic Ridge  

Microsoft Academic Search

The existence of very depleted melts in mid-ocean ridges was predicted previously in order to explain the presence of magnesian pyroxene and calcic plagioclase in mid-ocean ridge basalts. The discovery of melt is reported here that has major and trace element characteristics consistent with these predictions, occurring as an inclusion in an olivine phenocryst in a typical midocean ridge basalt

A. V. Sobolev; N. Shimizu

1993-01-01

347

Elasticity of Hydrous Olivine Polymorphs: Implications for Seismic Structure of the Transition Zone  

Microsoft Academic Search

The presence of water in the upper mantle and transition zone has the potential to explain various phenomena such as shear velocity anomalies or uplift and broadening of the 410-km discontinuity. The presence of H2O in the transition zone has also been frequently invoked to reconcile laboratory elasticity data on olivine polymorphs with seismic data for the amplitude of the

T. S. Duffy; Z. Mao; S. D. Jacobsen; F. Jiang; J. R. Smyth; C. M. Holl; D. J. Frost

2007-01-01

348

Amoeboid Olivine Aggregates in NWA 1152: Connection to CR Chondrites and the Cometary Particle T112  

NASA Astrophysics Data System (ADS)

We have examined the mineralogy of AOAs in NWA 1152 and compared with an AOA-like STARDUST particle. Based on our study, the coexistence of chromite and olivine suggests that the AOA-like cometary particle may have experienced incipient alteration.

Komatsu, M.; Fagan, T. J.; Mikouchi, T.; Zolensky, M.; Miyamoto, M.; Ohsumi, K.

2012-09-01

349

Post-entrapment modification of volatiles and oxygen fugacity in olivine-hosted melt inclusions  

NASA Astrophysics Data System (ADS)

The solubilities of volatiles (H2O, CO2, S, F, and Cl) in basaltic melts are dependent on variables such as temperature, pressure, melt composition, and redox state. Accordingly, volatile concentrations can change dramatically during the various stages of a magma's existence: from generation, to ascent through the mantle and crust, to final eruption at the Earth's surface. Olivine-hosted melt inclusions have the potential to preserve volatile concentrations at the time of entrapment due to the protection afforded by the host olivine against decompression and changes to the oxidation state of the external magma. Recent studies, however, have demonstrated that rapid diffusive re-equilibration of H2O and oxygen fugacity (f) can occur within olivine-hosted melt inclusions. Here we present volatile, hydrogen isotope, and major element data from dehydration experiments and a quantitative model that assesses proposed mechanisms for diffusive re-equilibration of H2O and f in olivine-hosted melt inclusions. Our comprehensive set of data for the behavior of common magmatic volatiles (H2O, CO2, F, Cl, and S) demonstrates that post-entrapment modification of CO2, and to a lesser extent S, can also occur. We show that the CO2 and S concentrations within an included melt decrease with progressive diffusive H2O loss, and propose that this occurs due to dehydration-induced changes to the internal pressure of the inclusion. Therefore, deriving accurate estimates for pre-eruptive CO2 and S concentrations from olivine-hosted melt inclusions requires accounting for the amount of CO2 and S hosted in vapor bubbles. We find, however, that Cl and F concentrations in olivine-hosted melt inclusions are not affected by diffusive re-equilibration through the host olivine nor by dehydration-induced pressure changes within the melt inclusion. Our results indicate that measured H2O, CO2 and S concentrations and Fe3+/?Fe ratios of included melts are not necessarily representative of the melt at the time of entrapment and thus are not reliable proxies for upper mantle conditions.

Bucholz, Claire E.; Gaetani, Glenn A.; Behn, Mark D.; Shimizu, Nobumichi

2013-07-01

350

Crystallographic preferred orientations and melt-rock interactions : olivine-rich troctolites from IODP Hole U1309D  

NASA Astrophysics Data System (ADS)

IODP Expeditions 304-305 sampled the Atlantis Massif, an oceanic core complex located at 30°N in the inside corner of the intersection of the Mid-Atlantic Ridge with the Atlantis Fracture Zone. The most primitive end-members of the recovered gabbroic sequence, olivine-rich troctolites (ol > ~70%), have textures and geochemical compositions intermediate between those of mantle peridotites and primitive cumulates, indicative of melt impregnation processes (Drouin et al., 2009). Olivine-rich troctolites from Hole U1309D (about 5% of recovered rocks) display poikilitic textures, with olivine ranging from coarse-grained subhedral crystals, commonly containing well-developed subgrains, to medium-grained rounded crystals with fewer or no substructures. Olivine substructures reveal dislocation creep that is consistent with activation of the main high-temperature slip systems, dominantly (010)[100]. Olivine crystallographic preferred orientation is very weak, but generally shows a relatively stronger, uncommon [001] concentration (Drouin et al., 2010). These unusual olivine fabrics are interpreted as resulting from dunitisation and melt impregnation of a previously deformed olivine matrix; the solid olivine framework is eventually disrupted by olivine corrosion along grain and subgrain boundaries, and the high-temperature plastic fabric is modified in a liquid-dominated regime. Similar fabrics are described in impregnated peridotites from the mantle/crust transition zone in the Oman ophiolite. A reduction of fabric strength in the presence of melt is also documented in deformation experiments performed in a gas-medium high-pressure high-temperature vessel. Experiments were conducted with olivine + melt (10 to 30 wt%) isostatically hot-pressed initial material. The olivine crystallographic preferred orientation is weaker in deformed sampled than in the undeformed hot pressed material. We propose that very weak fabrics such as those measured in the Atlantis Massif olivine-rich troctolites, in this case with unusual preferred [001] maxima, are a common result of melt-rock interactions in melt-impregnated peridotites or ultramafic cumulates in mid-ocean ridge environments. The joint study of in situ crystal geochemistry and microstructures is needed to characterize complex crystallization histories in open system with percolation of large volume of MORB-type melt that postdate olivine crystal-plastic deformation. - Drouin, M., Godard, M., Ildefonse, B., Bruguier, O., and Garrido, C., 2009. Chem. Geol., doi:10.1016/j.chemgeo.2009.02.013 - Drouin, M., B. Ildefonse, and M. Godard, 2010. Geochem. Geophys. Geosyst., doi:10.1029/2009GC002995

Drouin, M.; Ildefonse, B.; Hirth, G.; Waters, C. L.; Godard, M.

2010-12-01

351

Mineral Magnetism of Dusty Olivine: A Potential Carrier of Pre-Accretionary Remanence?  

NASA Astrophysics Data System (ADS)

The mechanism and location of chondrule formation is an important question in cosmochemistry. The remanent magnetisation of chondrules may provide clues to their formation environment, but requires magnetic carriers with extraordinary thermal and magnetic stability. Recently, the search for a suitable magnetic carrier has focussed on ‘dusty olivine’: relict grains that survived the chondrule heating event without fully melting. Dusty olivine grains contain submicron inclusions of metallic Fe-Ni, formed by sub-solidus reduction of the Fe-bearing olivine during heating. The Fe inclusions within dusty olivine potentially possess the ideal magnetic characteristics for acquiring and maintaining primary remanence. Here we describe a mineral magnetic characterisation of synthetic dusty olivine formed by laboratory reduction of terrestrial olivine. Crushed olivine grains were packed in a graphite crucible and reduced in a CO atmosphere at 1350°C for 10 minutes, before quenching into water. Samples were characterised by X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), temperature-dependent magnetic susceptibility (?-T), and first-order-reveral-curve (FORC) diagrams. The results demonstrate the potential, as well as the pitfalls, of using dusty olivine for paleomagnetism. Microscopy reveals abundant Fe-Ni particles with sizes ranging from > 1 ?m to < 20 nm. ?-T reveals the presence of both a bcc-Fe phase with Tc = 770°C and bcc/fcc Fe-Ni phases with varying Ni content. The presence of Ni complicates the magnetic properties due to the effect of the bcc-fcc martensitic transition. Evidence for Fe-Ni redistribution within the particles at high temperature is found in the ?-T measurements, which leads to the formation of a ferromagnetic Ni-rich alloy with fcc structure and Tc = 200°C. Further complications arise due to the formation of magnetite above 300°C, and its subsequent transformation to wustite above 580 °C. EBSD analysis reveals the presence of magnetite rims on the surface of some large Fe inclusions that have been exposed to air. FORC analysis demonstrates the presence of MD signals associated with > 1 ?m Fe particles, as well as an SD-like signal with broad coercivity distribution (extending to over 500 mT in some cases) and a narrow vertical spread. Comparison with TEM observations indicates that the coercivity distribution is consistent with SD particles dominated by shape anisotropy. This work highlights the combination of high magnetic stability and thermal stability that make dusty olivine a potential carrier of pre-accretionary remanence. It also demonstrates that a thorough characterisation of the Fe particles within natural dusty olivine and a detailed understanding of the mineral magnetic phase relations is necessary in order to design an effective paleointensity protocol capable of extracting the value of the paleofield.

Harrison, R. J.; Lappe, S.; Feinberg, J. M.; Russell, S.; Bromiley, G.; Bastos da Silva Fanta, A.; Dunin-Borkowski, R.

2009-12-01

352

Mechanisms and Timescales for Reequilibration of Water in Olivine-Hosted Melt Inclusions  

NASA Astrophysics Data System (ADS)

Water solubility in silicate melts drops substantially with decreasing pressure. A magma containing several weight % dissolved H2O in the shallow crust is left with only a few thousand ppm following eruption. Olivine-hosted melt inclusions provide information on the pre-eruptive H2O contents of degassed magmas because the strength of the host crystal protects the melt inclusion from the decompression experienced by the entraining magma. The principal uncertainty involved with interpreting pre-eruptive H2O concentrations from melt inclusions is the potential for diffusive loss or gain of H+ (protons) through the host olivine. It has been proposed that Fe redox reactions severely limit the proton flux, and that episodes of H2O loss/gain are easily identifiable through changes in oxidation state of the inclusion [1,2]. Results from hydration and dehydration experiments carried out on natural inclusion-bearing olivines and analyzed by SIMS confirm that H2O re-equilibratrion occurs rapidly via proton diffusion through the host olivine, and demonstrate that re-equilibration of oxygen fugacity within the inclusions occurs on comparable timescales via diffusion of point defects. Therefore, an olivine-hosted melt inclusion only provides a reliable record for the H2O content of the external melt with which it most recently equilibrated. Hydration experiments were performed on olivines from Puu Wahi, a scoria cone on the NE rift zone of Mauna Loa volcano. Melt inclusions initially containing 0.36±0.05 wt% H2O were held at 1 GPa and 1250°C in water enriched in 18O (18O/?O = 0.977) and D (2H/?H = 0.998) to map the transport of protons and oxygen during equilibration of melt inclusions with an external fluid. Dehydration experiments were carried out for 1 to 18 hrs at 1 bar and 1250 °C on inclusion-bearing olivines in scoria erupted from Cerro Negro volcano, Nicaragua, in 1999. The initial concentration of H2O in these melt inclusions is uniformly high (3.6±0.6 wt%). All run products were analyzed by SIMS on the Cameca 1280 ion microprobe at WHOI. Results from our experiments confirm that the mechanism for loss or gain of H2O from olivine-hosted melt inclusions is lattice diffusion of protons. This process leaves behind an O2- for every 2 protons lost, and scavenges an O2- for every 2 protons gained, producing an increase or decrease, respectively, of the fugacity of oxygen within the inclusion. However, H2O loss/gain for olivine-hosted melt inclusions is coupled with point defect-mediated oxygen fugacity re-equilibration. Therefore, Fe redox reactions do not limit either the amount or rate of water loss or gain by the inclusion. The H2O concentration of an olivine-hosted melt inclusion can change rapidly, and that change is not recorded by the oxygen fugacity of the melt. References: [1] A. V. Sobolev, L. V. Danyushevsky, J Petrol 35, 1183 (1994); [2] L. V. Danyushevsky, A. W. McNeill, A. V. Sobolev, Chem Geol 183, 5 (2002).

Gaetani, G. A.; O'Leary, J. A.; Shimizu, N.

2009-12-01

353

Studying the pseudomorphic replacement of olivine by silica at acidic conditions  

NASA Astrophysics Data System (ADS)

Silicification is an important reaction occurring in volcanic environments that aids the neutralisation of the extremely acidic fluids produced. Replacement of the original minerals by silica results in the reacting fluid becoming enriched in cations that can be subsequently transported through the hydrothermal system (Varekamp et al., 2000). In some examples olivine and pyroxene phenocrysts within the reacted layers are pseudomorphically replaced by silica (Africano and Bernard, 2000). We have performed unstirred batch experiments using sulphuric acid and whole olivine crystals to explore the parameters that control phase precipitation and the pseudomorphic replacement of forsteritic olivine. The experiments were conducted in Teflon-lined steel autoclaves at temperatures between 80 and 120 ° C. In lower temperature experiments the reaction of olivine with 0.1 M sulphuric acid produced a red precipitate coating the olivine surface. The red phase was too low in concentration to be identified but is expected to be hematite (Fe2O3). In contrast, experiments conducted in sulphuric acid between 1 and 3.6 M produced an amorphous silica pseudomorph of olivine. The dependence of phase precipitation on pH was tested using a sulphuric acid solution neutralised to pH 2 with a resulting ionic strength equivalent to 1 M. At low temperatures the olivine reacted to produce amorphous silica and a yellow fluid indicating that Fe remained in solution, possibly as a complex with sulphate. Higher temperatures allowed the iron to be liberated from the fluid and precipitated as hematite in association with amorphous silica. Elemental content microprobe data for the olivine and silica rim from pseudomorphic replacement reactions suggests that the majority of cations from olivine dissolution remained in solution. This observation was confirmed by inductively coupled plasma-mass spectroscopy, which showed a high content of Mg and Fe in the fluid. The variation of replacement products at different reaction conditions highlights the sensitivity of olivine replacement in acidic conditions to factors such as pH. We used an 18O-enriched fluid to trace the mechanism of the pseudomorphic replacement. Raman spectroscopy of the silica layer showed that the 18O was taken into the silica rim in enough concentration to produce a shift in the Raman peaks resulting from 18O-Si bonding within the silica network. The products from experiments with different sulphuric acid concentrations showed that as concentration was reduced the silica layer became increasingly fragile until it no longer precipitated as a pseudomorph. This observation and the incorporation of 18O into the amorphous silica structure indicate that the formation of a pseudomorph occurs via an interface-coupled dissolution-reprecipitation mechanism (Putnis and Putnis, 2007). References Africano F. and Bernard A. (2000), J. Volcanol. Geoth. Res., 97 475-495 Putnis A. and Putnis C. V. (2007), J. Solid State Chem., 180, 1783-1786 Varekamp J. C., Pasternack G. B. and Rowe Jr. G. L. (2000), J. Volcanol. Geoth. Res., 97 161-179

King, Helen E.; Geisler, Thorsten; Putnis, Andrew

2010-05-01

354

Midinfrared Multi-technique Spectroscopy of Synthetic Olivines (Forsterite to Fayalite)  

NASA Astrophysics Data System (ADS)

Olivine minerals are one of the most dominant minerals in the solar system and their chemistry is highly variable, as is the chemistry of many naturally occurring minerals. Olivines that range in composition from Mg-bearing (forsterite [Fo100], Mg2SiO4) to Fe-bearing (fayalite [Fo0], Fe2SiO4) can have any amount of substitution of those 2 cations in this common binary solid solution series. Changes in chemistry across this binary series cause the structure of the mineral to be affected, in turn affecting the appearance of the midinfrared spectra thereof that are governed by the vibrations of the constituent molecules. Here, synthetic olivine samples ranging in composition from forsterite (Mg2SiO4) to fayalite (Fe2SiO4) were analyzed using midinfrared thermal emission, midinfrared specular and diffuse reflectance, and midinfrared attenuated total reflectance spectroscopies to study the affects of Mg-Fe solid solution on the spectra acquired. Our findings suggest that for each spectroscopic method, features in the spectra systematically grade from one endmember (e.g., forsterite) at higher frequencies to the other (e.g., fayalite) at lower frequencies and that each spectrum is diagnostic of the chemistry of the sample across the entire chemical continuum. The range of olivine spectra generated from this work can be used to interpret hand-sample spectra (of rocks, sediments, or meteorites) and remote-sensing spectra of Earth and other planetary surfaces, as well as of asteroids or dead comets, and can help to identify specific olivine composition.

Lane, M. D.; Glotch, T. D.; Dyar, M. D.; Pieters, C. M.; Klima, R.; Hiroi, T.; Bishop, J. L.; Sunshine, J. M.

2009-12-01

355

Pressure Dependence of Creep in Olivine and its Importance for Measurement of Mantle Rheology  

NASA Astrophysics Data System (ADS)

Rheological properties of mantle minerals are critical for understanding the dynamics of the Earth’s interior. Mantle rocks are made of 60-100% olivine which is also the weakest mineral, hence the rheology of the upper mantle is probably dominated by that of polycrystalline olivine. Previous deformation experiments conducted at various pressures to measure the rheological properties of olivine at high temperature have resulted in controversial results. The result from gas pressure-medium apparatus were of high quality, but were restricted to low pressures (< 500MPa); on the other hand, multianvil and diamond-cell apparatus can achieve very much higher pressures, but the ability to use these machines for quantitative deformation studies is still under development. In order to address this issue and provide a standard for strength comparison for various apparatus types, we are conducting a series of experiments on synthetic polycrystalline forsterite, the Mg end member of olivine, in a modified Griggs apparatus with liquid pressure-medium that is capable of precisely measuring the stress during deformation experiments with a confining pressure from 0.5GPa to 3.5GPa. Hot-pressed Fe-free forsterite is the starting material, which avoids the myriad problems that Fe could add experimentally as Fe is sensitive to the oxygen fugacity. A small amount of SiO2 (equivalent to 3% enstatite) was added to ensure the defect populations in olivine are in equilibrium with enstatite, not periclase. Preliminary results indicate a significant effect of pressure on flow stress, in agreement with some previous results but contrary to others. We are now exploring the apparent effects of strain rate to test the robustness of this result.

Xia, G.; Green, H. W.; Zhang, J.

2009-12-01

356

Distinguishing between Apollo 14 impact melt and pristine mare basalt samples by geochemical and textural analyses of olivine  

NASA Astrophysics Data System (ADS)

Apollo 14 (A-14) impact melt olivine vitrophyres (OVs), composed of olivine phenocrysts in an opaque glass matrix with minor amounts of pyroxene and plagioclase, are petrographically similar to pristine quenched A-14 high-alumina (high-Al) and Apollo 12 (A-12) basalts. Textural and chemical analyses have been conducted on olivines within impact melt and pristine mare basalt clasts from A-14 breccia 14321 as well as various olivine-phyric Apollo 12 and 17 basalts to be able to distinguish between the petrographically similar samples. The A-14 high-Al basalts examined here represent samples from each of the three chemical groups (A, B, C). Examples from the three A-12 basalt suites (Ilmenite, Olivine, Pigeonite) and olivine-rich Apollo 17 (A-17) Type C basalt, 74275, have also been analyzed. As a complement to the chemical analyses, crystal size distributions (CSDs) were determined for approximately half of the samples investigated here (due to a small number of olivine crystals that did not produce statistically meaningful CSDs on half of the samples), and confirm that although similar, the basalts and impact melts are texturally distinct. Olivines from A-14 impact melts have the highest average forsterite contents (average Fo ˜0.82) and generally the lowest average Co (37 ppm) and Mn (1544 ppm) abundances, thus chemically distinguishing them from the pristine basalts. In addition, chemical compositions obtained for olivine from 14321,1486 are most likely representative of an impact melt and thus contradict its previous classification as a high-Al basalt (Neal et al., 1988); olivine from, 1486 have similar average forsterite (average Fo ˜0.82) and Ti/V-ratio to the OVs. Furthermore, on the basis of their chemical compositions, olivines have been identified within the impact melts that are likely inherited from basalts; these olivines are chemically distinct from the rest of the impact melt olivine population with lower forsterite (0.67-0.80) and low Ti/V (˜10), which are similar to olivine compositions from the A-14 high-Al basalts. In addition to distinguishing between sample types from A-14, olivine compositions can also be used to distinguish between pristine mare basalts from various missions. Olivine within the selected samples from the individual A-12 basalt suites can also be distinguished chemically from one another using the Ti/V ratio, where Olivine suite basalts have Ti/V <3 and Ilmenite suite basalts have Ti/V >3.5. The results indicate that combined use of CSDs and chemical analyses of olivine can be used to reliably distinguish between (1) impact melts and pristine Apollo 14 basalts, (2) basalts from different landing sites, and (3) individual basalt suites from a single site.

Fagan, A. L.; Neal, C. R.; Simonetti, A.; Donohue, P. H.; O'Sullivan, K. M.

2013-04-01

357

Low-pressure fractionation of strongly undersaturated alkaline ultrabasic magma: the olivine-melilite-nephelinite at Moiliili, Oahu, Hawaii  

NASA Astrophysics Data System (ADS)

The olivine-melilite-nephelinite at Moiliili, a representative of the Honolulu Volcanic Series, experienced post-eruptive fractional crystallization which resulted in the formation of pegmatoids of restricted volume. The pegmatoids can be equated in composition with melilite-bearing nephelinite (?melilite-bearing titanaugite melteigite and titanaugite ijolite). Pegmatoid olivine, titaniferous Ca-rich pyroxene and melilite display mild decreases in their 100 Mg/(Mg + Fe) ratios, largely in response to olivine fractionation. Titanomagnetite Fe2TiO4 components increased with fractionation, mainly at the expense of Fe3O4. Nepheline and sodalite show only restricted compositional variation, although sodalite solid solution is more extensive than in plutonic analogues. Compared with the host olivine-melilite-nephelinite, the pegmatoids are highly depleted in Cr and Ni and enriched in Rb, Sr, Y, Zr, Nb and Ba. The Moiliili fractionation sequence confirms the low-pressure trend olivine-melilite-nephelinite?melilite-bearing nephelinite, previously defined on the basis of relationships in the synthetic system diopside-akermanite-nepheline, but it provides no support for the proposal that olivine-melilite-nephelinite ultimately may fractionate to phonolite. Phonolitic differentiates can be generated by the low-pressure fractionation of alkali feldspar-bearing olivine nephelinites but the relative volumes of the salic derivatives are minor. These volumetric and other constraints inherent in low-pressure fractionation models employing nephelinitic parents suggest that at least some phonolites may be the products of deep crustal or upper mantle anatexis.

Wilkinson, J. F. G.; Stolz, A. J.

1983-09-01

358

Olivine weathering in soil, and its effects on growth and nutrient uptake in Ryegrass (Lolium perenne L.): a pot experiment.  

PubMed

Mineral carbonation of basic silicate minerals regulates atmospheric CO(2) on geological time scales by locking up carbon. Mining and spreading onto the earth's surface of fast-weathering silicates, such as olivine, has been proposed to speed up this natural CO(2) sequestration ('enhanced weathering'). While agriculture may offer an existing infrastructure, weathering rate and impacts on soil and plant are largely unknown. Our objectives were to assess weathering of olivine in soil, and its effects on plant growth and nutrient uptake. In a pot experiment with perennial ryegrass (Lolium perenne L.), weathering during 32 weeks was inferred from bioavailability of magnesium (Mg) in soil and plant. Olivine doses were equivalent to 1630 (OLIV1), 8150, 40700 and 204000 (OLIV4) kg ha(-1). Alternatively, the soluble Mg salt kieserite was applied for reference. Olivine increased plant growth (+15.6%) and plant K concentration (+16.5%) in OLIV4. At all doses, olivine increased bioavailability of Mg and Ni in soil, as well as uptake of Mg, Si and Ni in plants. Olivine suppressed Ca uptake. Weathering estimated from a Mg balance was equivalent to 240 kg ha(-1) (14.8% of dose, OLIV1) to 2240 kg ha(-1) (1.1%, OLIV4). This corresponds to gross CO(2) sequestration of 290 to 2690 kg ha(-1) (29 10(3) to 269 10(3) kg km(-2).) Alternatively, weathering estimated from similarity with kieserite treatments ranged from 13% to 58% for OLIV1. The Olsen model for olivine carbonation predicted 4.0% to 9.0% weathering for our case, independent of olivine dose. Our % values observed at high doses were smaller than this, suggesting negative feedbacks in soil. Yet, weathering appears fast enough to support the 'enhanced weathering' concept. In agriculture, olivine doses must remain within limits to avoid imbalances in plant nutrition, notably at low Ca availability; and to avoid Ni accumulation in soil and crop. PMID:22912685

ten Berge, Hein F M; van der Meer, Hugo G; Steenhuizen, Johan W; Goedhart, Paul W; Knops, Pol; Verhagen, Jan

2012-08-09

359

Olivine Weathering in Soil, and Its Effects on Growth and Nutrient Uptake in Ryegrass (Lolium perenne L.): A Pot Experiment  

PubMed Central

Mineral carbonation of basic silicate minerals regulates atmospheric CO2 on geological time scales by locking up carbon. Mining and spreading onto the earth's surface of fast-weathering silicates, such as olivine, has been proposed to speed up this natural CO2 sequestration (‘enhanced weathering’). While agriculture may offer an existing infrastructure, weathering rate and impacts on soil and plant are largely unknown. Our objectives were to assess weathering of olivine in soil, and its effects on plant growth and nutrient uptake. In a pot experiment with perennial ryegrass (Lolium perenne L.), weathering during 32 weeks was inferred from bioavailability of magnesium (Mg) in soil and plant. Olivine doses were equivalent to 1630 (OLIV1), 8150, 40700 and 204000 (OLIV4) kg ha?1. Alternatively, the soluble Mg salt kieserite was applied for reference. Olivine increased plant growth (+15.6%) and plant K concentration (+16.5%) in OLIV4. At all doses, olivine increased bioavailability of Mg and Ni in soil, as well as uptake of Mg, Si and Ni in plants. Olivine suppressed Ca uptake. Weathering estimated from a Mg balance was equivalent to 240 kg ha?1 (14.8% of dose, OLIV1) to 2240 kg ha?1 (1.1%, OLIV4). This corresponds to gross CO2 sequestration of 290 to 2690 kg ha?1 (29 103 to 269 103 kg km?2.) Alternatively, weathering estimated from similarity with kieserite treatments ranged from 13% to 58% for OLIV1. The Olsen model for olivine carbonation predicted 4.0% to 9.0% weathering for our case, independent of olivine dose. Our % values observed at high doses were smaller than this, suggesting negative feedbacks in soil. Yet, weathering appears fast enough to support the ‘enhanced weathering’ concept. In agriculture, olivine doses must remain within limits to avoid imbalances in plant nutrition, notably at low Ca availability; and to avoid Ni accumulation in soil and crop.

ten Berge, Hein F. M.; van der Meer, Hugo G.; Steenhuizen, Johan W.; Goedhart, Paul W.; Knops, Pol; Verhagen, Jan

2012-01-01

360

Experimental Investigation of the Dissolution and Alteration of Olivine at Low Temperatures and Pressures  

NASA Astrophysics Data System (ADS)

We have determined the surface characteristics of single crystals of olivine that have been altered under a variety of experimental conditions relevant to processes occurring on the Martian surface and in shallow crustal environments (i.e. mid-ocean ridge systems and hydrothermal environments). Most previous experiments have focused on dissolution rates of mineral powders at near-surface conditions of temperature (25 °C), pressure (1 atm), and pH (2--7) (see Brantley, 2003, for summary). The intent of our study is to explore the surface physical, chemical and mineralogical features attendant with reactions of single crystals of olivine. Surface analytical methods such as SEM, XRD, TEM, SIMS, IR and XPS are being used to interrogate the reacted mineral surfaces. Our experiments were performed over a range of T=25--150 °C, t=1--30 d, and pH=2--7. The starting material for these experiments consisted of single grains of San Carlos olivine (Fo90) that were cut to a size of ~4 mm in diameter and ~1 mm in thickness. The larger, flat surfaces of these olivine 'slices' were polished to ensure a uniform surface layer. Initial starting solutions included doubly-distilled water (pH=7), HCl (pH=2) and H2SO4 (pH=2). Two olivine crystals per experiment were loaded into a pyrex tube, and the accompanying solution was added with a fluid to rock ratio of either 5:1 or 15:1. Solutions were frozen and tubes were evacuated prior to sealing, ensuring that any reaction or dissolution occurred at an internal pressure corresponding to the temperature of interest along the liquid-vapor curve for the solution. Preliminary results indicate that all olivine samples, regardless of experiment duration, temperature, or pH conditions, have some measurable amount of weight loss (0.1--0.3%). SEM analysis shows the development of dissolution pits in most of the experimental samples, and the presence of secondary phases on the surface of olivine samples reacted with acidic starting solutions (pH=2). BSE and SE images indicate that these secondary phases (as yet not quantitatively determined) are compositionally distinct from starting olivine. A characteristic of these experiments is that the reaction rapidly increases the pH of the solution, even in experiments with a fluid to rock ratio of 15:1. At a fluid to rock ratio of 5:1, the short duration experiments (t=1d, T=150 °C) exhibited a change in pH from 2 to 6.17 for HCl (aq) starting solutions, and a similar change was also observed for H2SO4 (aq) starting solutions. These results have an important bearing on the interpretation of olivine reactivity in acidic solutions relevant to numerous planetary crustal settings.

Deangelis, M. T.; Labotka, T. C.; Cole, D. R.

2007-12-01

361

A new version of the spinel-olivine-pyroxene oxybarometer and extreme redox differentiation in magmatic systems of mantle sources  

NASA Astrophysics Data System (ADS)

A new version of an oxybarometer for olivine + clinopyroxene + spinel phase association based on consideration of the equilibrium (2) has been developed. Assessments of the oxygen fugasity for mineral associations of meimechites, Gulinskaya intrusion olivine-containing rocks, and microphenocrysts of olivine and clinopyroxene from intergranular glasses in mantle xenoliths from Sal Island, the Cape Verde archipelago, which contain grains of metallic alloys, were made. The oxygen fugasity values that characterize magmatic systems of mantle sources are shown to be capable of being varied by 7-8 orders of magnitude.

Ryabchikov, I. D.; Kogarko, L. N.

2010-02-01

362

A New Insight into the Polaron--Li Complex Diffusion in Cathode Material LiFe1-yMnyPO4 for Li Ion Batteries  

NASA Astrophysics Data System (ADS)

Based on the Heyd--Scuseria--Ernzerhof hybrid density functionals study, we proposed a new insight into the diffusion of polaron--Li vacancy complexes in LiFe1-yMnyPO4 (y=0,1/2,1). It is found that the polaron migrates along a crossing or a parallel path relative to the Li moving direction. In LiFePO4, the complex diffusion along the zigzag pathway is favorable and has a barrier of 600 meV, while the diffusion along the parallel pathway with a barrier of 623 meV is favorable in LiMnPO4. For LiFe1/2Mn1/2PO4, since the polaron is formed within a single Fe layer, the diffusion proceeds along the parallel pathway with a barrier of 635 meV.

Dinh, Van An; Nara, Jun; Ohno, Takahisa

2012-04-01

363

Deformation Microstructures of Olivines from Deep Mantle Xenoliths: The Roles of Water and Dynamic Recrystallization  

NASA Astrophysics Data System (ADS)

The presence and distributional heterogeneity of water in the upper mantle is critically important to our study of plate dynamics and continental evolution. Recent experimental results have shown that there are several discrete lattice-preferred-orientation (LPO) patterns in olivine, which vary as a function of water content and stress. These experimental data are part of our large laboratory dataset that considers the relationships between deformation mechanisms and water content of deformed, synthetic, olivine aggregates. To better understand the relationship between water content and deformation fabrics in natural rocks, we conducted comprehensive investigations of four sheared-lherzolite xenoliths from 5.5-5.7 GPa. The xenoliths in this study were collected from the Jagersfontein kimberlite in South Africa (kindly supplied by F.R. Boyd). Compositions were analyzed using EPMA, and depths were constrained using pyroxene thermobarometry (by F.R. Boyd). There is no obvious foliation/lineation pattern in any of the samples, so strain was defined by the shape-preferred-orientation of recrystallized olivines; therefore, the recorded strain reflects the orientations of recrystallized olivine grains, not the orientations of any visible macroscopic deformation textures. The finite strain for each sample was determined using an in-house digitization and software package that calculates a finite strain ellipsoid (FSE) from the elliptical projections of olivine grains in several thin-sections. Olivine LPO was measured using a TSL electron backscatter diffraction (EBSD) system on a Philips XL30 SEM. Dislocations were illuminated using the oxidation decoration technique. Water content was measured using Fourier-transform infrared (FTIR) spectroscopy. Although the strength and form of the LPO patterns vary, all samples show characteristically "dry" fabrics. The low water content is inferred to reflect the chemical environment of the rock immediately prior to its rapid deformation and exhumation. The absence of any "wet" fabrics determine an upper limit of ~400 ppm H/Si to the amount of water contained in this region of the upper mantle. FTIR analyses show only small absorption peaks from OH vibrations, suggesting that some water may have been lost during exhumation. Optical observation shows that the samples have experienced nearly complete dynamic recrystallization. There is a strong correlation between the LPO fabrics and the microscopic strain recorded by the FSE of the recrystalized grains. This suggests that the orientation of seismic anisotropy may deviate from the geometry defined by the macroscopic flow plane.

Skemer, P. A.; Jiang, Z.; Brandon, M. T.; Karato, S.

2002-12-01

364

Experimental investigation of LPO development and recrystallized grain size evolution in plagioclase and plagioclase + olivine aggregates  

NASA Astrophysics Data System (ADS)

Plagioclase rheology is important in directing the strength evolution of the lower oceanic and continental crust. However, our ability to utilize natural plagioclase microstructures to quantify the strength and conditions of deformation of the lower crust is restricted by our still limited understanding of the mechanics of plagioclase deformation and associated microstructural development in experiments. This is particularly the case when plagioclase is present in a polyphase rock. The work presented here represents the initial results of a systematic study focused on exploring the strength and microstructural evolution of plagioclase and plagioclase-olivine aggregates. Specifically, this study is aimed at exploring the role of a second phase in affecting the progressive development and strengthening of lattice preferred orientations (LPO) of plagioclase. In addition to strength and LPO development, these experiments should provide constraints on plagioclase recrystallization mechanisms and recrystallized grain size evolution with progressive deformation. The effects of water content and modal abundance of olivne on plagioclase recrystallization and LPO development will also be explored. Initial deformation experiments have been conducted on mixtures of Sonoran labradorite and San Carlos olivine (90-10% plagioclase and olivine respectively). Deformation experiments have been carried out in a Griggs apparatus using a molten salt assembly. A subset of samples are to be dried in a controlled atmosphere furnace to compare the effect of dry and wet rheology on the development and strength of LPO as well as the effect of water content on recrystallized grain size development. Experimental conditions range in pressure from 1-1.5 GPa and in temperature from 900-1100C. Experiments were conducted using constant displacement rates ranging from 1e-6-1e-5 /s. Thus far, experiments have been conducted in a standard shear assembly to shear strains of ~2. Mechanical data of these initial experiments are consistent with steady state deformation with some slight weakening at shear strains higher than ?=1. Preliminary microstructural observations and electron backscatter diffraction (EBSD) data reveal development of a strong SPO and moderate LPO in plagioclase as well as evidence for the onset of recrystallization. Olivine grains form sigma clasts within the plagioclase matrix. However, despite this evidence for active crystal-plastic processes in olivine, preliminary EBSD investigations do not reveal a strong olivine LPO.

Goergen, E. T.; Meyers, C.; Hirth, G.

2011-12-01

365

CO2 Geological Storage in Olivine Rich Basaltic Aquifers: New Insights From Flow-Through Experiments  

NASA Astrophysics Data System (ADS)

Injection of CO2-rich fluids into basaltic aquifers is one of the methods envisaged for mitigation of increasing atmospheric CO2. Basalts are rich in Mg, Fe and Ca and have a high potential to trap CO2 as carbonate minerals. However, the role of reaction-transport processes has yet to be investigated in order to predict the capacity and sustainability for CO2 storage of these highly reactive systems. We present the results of three flow-through experiments performed at 180°C and total pressure 12 MPa. NaHCO3 rich water (0.5 mol/L) mixed with CO2 (PCO2 = 10 MPa) was injected through sintered analogues of olivine-accumulation zones in basaltic flows (~ 95% olivine Fo87, MORB glass, minor chromite). The injection rate was 1 mL/h for exp. 1 and 2, and 0.1 mL/h for exp. 3. The initial porosity and permeability of samples ranges from 3 to 7% and 250.10-18 to 2500.10-18 m2 respectively. All experiments show a strong permeability decrease (down to 10-18 m2) after 90 hours for exp. 1 and 2, earlier for exp 3. Yet dissolution occurs: high concentrations of Zr and Al and of Co in the outlet fluids indicate dissolution of basaltic glass and olivine respectively. Si concentration changes reveal a more complex system with olivine dissolution and the precipitation of Si rich phases: we observed the growth of relatively large (up to 5 microns) Mg-Fe rich phyllosilicates mostly perpendicular to olivine surface. This reaction is typically associated to hydration of (ultra-)mafic rocks and may explain the decrease in permeability during experiments. Finally, the low Ca and Mg fluid concentrations suggest trapping by Ca-Mg rich phases. Ankerite and dolomite were identified by Raman spectrometry in the reacted samples after exp. 1 and 2, while exp. 3 was characterized by precipitation of well-developed and abundant magnesite (Mg0.88 Fe0.11 Ca0.01 CO3) replacing dissolved olivine. Carbonation appears to be an efficient process: ~ 0.015g of CO2 per gram of sample is stored as carbonates during exp. 1, that is, if these results were directly upscaled to the size of an injection site, an average yield of ~ 45 kg/m3/day. Our results indicate a strong control of flow rates on carbonation, but also on hydration reactions. This implies that CO2 storage capacity of the basaltic aquifer will change with the distance to the injection well and time.

Peuble, S.; Godard, M.; Luquot, L.; Gouze, P.

2011-12-01

366

Experimental Determination of Olivine Reaction Rim Growth Rates in the Lassen Peak, CA Magma Chamber  

NASA Astrophysics Data System (ADS)

A series of hydrothermal (high-pressure and -temperature) experiments have been performed on starting materials consisting of ~5 wt% of Fo85 olivine separated from a spinel lherzolite xenolith (UM-5) from Kilbourne Hole, NM combined with powdered natural dacite pumice from the 1915 eruption of Lassen Peak, CA. The dacite represents the silicic end member (67.8 wt% SiO2) of mixed dacite and andesite magmas present in the 1915 Lassen Peak eruptive products. The olivine represents xenocrystic grains from the admixed andesite that combined with the dacite magma prior to the eruption. In the natural dacitic eruptive products, xenocrystic olivine grains display morphologically complex reaction rims of orthopyroxene. These rims are interpreted to have grown during magma mixing/mingling prior to the eruption. The growth rate of these rims may be used to constrain the length of time between magma recharge and eruption. Time series experiments were performed to reproduce olivine reaction rims within the dacite. Experiments were performed with run durations of 50, 100, 200, 400, and 600 hours at 50 MPa and 825°C and 875°C. Water-saturated run conditions at the Ni-NiO buffer represent plausible dacite equilibration conditions based on earlier phase equilibria experiments. Preliminary measurements of orthopyroxene rim widths measured on two olivine grains from experiments run at 50 MPa and 825°C for 50 and 600 hours show an increase in rim width from 2.2±1.8 ?m to 3.3±2.5 ?m, respectively (average and 1? standard deviation of 490 and 651 linear measurements). In the 50-hour experiment, rim widths range from 0 to 13.4 ?m, whereas in the 600 hour run, widths are 0.63-23.1 ?m. The 600 hour run also has a larger percentage of width measurements above 5 ?m (24.8% of measured widths, compared to 2.8% of measurements in the 50-hour experiment.) In the 50-hour experiment, 21.0% of the rim width measurements are 1 ?m or less, whereas only 6.4% of measured olivine reaction rim widths are <1?m in the 600-hour run. Additional measurements on these and other experiments are under way using the linear measurement technique applied here, as well as other methods to estimate rim width and area. Experimentally determined rim growth rates will be compared with rims on the natural samples in order to constrain the timing and duration of magma mixing prior to the eruption.

Schwab, B. E.; Castro, J. M.

2007-12-01

367

Weathering of olivine and pyroxene on Mars: Evidence from missions, meteorites, and terrestrial mineral analogs  

NASA Astrophysics Data System (ADS)

Mineral-water interactions modify primary minerals, produce new minerals as alteration products, and modify the solute loads of the solutions. Except for situations in which the solutions still coexist with reactant and product minerals, properties of the solutions (e.g., the abundances of various solutes; the duration of their contact with the minerals) must be inferred from the mineral assemblages left behind. Abundant literature exists on identifying and interpreting the paleoenvironmental significance of mineral products of such reactions on Mars (e.g., clay minerals and other phyllosilicates; sulfates; carbonates). Less literature exists on interpreting the paleoenvironmental significance of primary minerals and their properties in altered Mars materials. Since the arrival of the Mars Exploration Rovers in 2004 and the Phoenix Mars Lander in 2008, a number of new observations of primary-mineral destruction have been enabled by deployment of microscopic imagers on Mars and continued microscopic investigation of Mars meteorites in terrestrial laboratories. These include examples of alteration of both of the major minerals of Mars’ igneous rocks, olivine and pyroxene. Olivine alteration is indicated by selective removal of euhedral olivine from weathered rinds on basalt at Gusev crater, and elongate cavities of non-uniform width in olivine in the Mars meteorite Nakhla; the latter exhibit some similarities to and some differences from common arrays of corrosion pits on weathered terrestrial olivine. Pyroxene dissolution and corrosion are indicated by sharp pointed alteration features on clinopyroxene in the Mars meteorite Nakhla, scaly features on orthopyroxene at the orthopyroxene-carbonate interface in the Allan Hills 84001 Mars meteorite, and angular sawtooth features on soil grains from the Phoenix landing site, all of which are similar or identical to common corrosion textures on weathered terrestrial pyroxene and related chain-silicate minerals. Primary-mineral corrosion occurs in Mars meteorites of a range of alteration ages, from ~3.9 Ga (~ Mid-Noachian; orthopyroxene corrosion and associated carbonate formation in ALH 84001), through ~670 Ma (~ Mid-Late Amazonian; clinopyroxene corrosion and diverse alteration minerals in nakhlites), and possibly quite recently (Late Amazonian; pre-terrestrial carbonate and sulfate in the ~170 Ma-old shergottite EET 79001). Primary-mineral removal of indeterminate but possibly quite recent age is also recorded from Mars-surface microscopic imagery, including euhedral olivine molds in weathered rinds on basaltic boulders at Gusev crater and possible pyroxene corrosion in unconsolidated granular material at the Phoenix landing site, preserved despite possible physical transport and abrasion processes. These occurrences of primary-mineral modification and destruction record aqueous alteration processes over a broad range of times in the paleoenvironmental history of Mars’ surface.

Velbel, M. A.

2010-12-01

368

Origin of iron-rich olivine in the matrices of type 3 ordinary chondrites - an experimental study  

NASA Astrophysics Data System (ADS)

The reaction of metallic iron and enstatite, with and without forsterite and SiO2, is experimentally studied at temperatures between 1150 and 800 C in order to investigate the origin of iron-rich olivine in the matrices of type 3 chondrites. The composition of olivine is shown to become more iron-rich with increasing silica/enstatite ratio. Possible scenarios for the origin of this olivine include: (1) free silica having been present if the iron-rich olivine was formed by solid-state reactions under oxidizing conditions in the solar nebula; and (2) the reaction of silicon-rich gas with metallic iron having taken place under oxidizing conditions in the solar nebula.

Nagahara, H.; Kushiro, I.

1987-10-01

369

Petrography and classification of Ca, Al-rich and olivine-rich inclusions in the Allende CV3 chondrite  

NASA Astrophysics Data System (ADS)

The results of a detailed, systematic petrographic survey of Ca, Al-rich and olivine-rich inclusions in the Allende CV3 chondrite are reported, and a new classification system based on clearly defined and readily applied petrographic criteria is presented. Most Allende inclusions are aggregates containing one or more of three distinct constituents: (1) rimmed concentric objects enriched in Al- and Ti-rich oxide minerals and various amounts of Ca-rich silicates; (2) porous, 'fine-grained' chaotic material enriched in Ca-rich silicates, especially clinopyroxenes and garnets; and (3) porous, 'fine-grained', mafic inclusion matrix, enriched in olivine, pyroxene, and feldspathoids. Two texturally distinct varieties of inclusions consist primarily of inclusion matrix: unrimmed olivine aggregates and rimmed olivine aggregates. Ca, Al-rich inclusions are classified on the basis of the size and abundance of their constituent concentric objects. Some fundamental relationships among Allende inclusions that previusly have not been emphasized are discussed.

Kornacki, A. S.; Wood, J. A.

1984-02-01

370

Detection of Serpentine on Mars by MRO-CRISM and Possible Relationship with Olivine and Magnesium Carbonate in Nili Fossae  

NASA Astrophysics Data System (ADS)

Reports the first orbital detection of serpentine on Mars’ surface, made by CRISM in the Thaumasia and Nili Fossae regions. Evidence for serpentinization of an olivine-magnesium carbonate-serpentine bearing rock unit in Nili Fossae is discussed.

Ehlmann, B. L.; Mustard, J. F.; Murchie, S. L.

2009-03-01

371

Elasticity of iron-bearing olivine polymorphs investigated by first principles  

NASA Astrophysics Data System (ADS)

We calculate by first principles the effect of iron on the high pressure-temperature elasticity of olivine polymorphs: ?-phase (olivine), ?-phase (wadsleyite) and ?-phase (ringwoodite), the major constituents of the Earth's upper mantle and transition zone (TZ). We combine the LDA, the quasiharmonic approximation, and a model vibrational density of states for the solid solution to calculate the full elastic tensor Cij, bulk (K) and shear (G) moduli of (Mg0.875Fe0.125)2SiO4. Comparison with experimental data at ambient conditions validates our results. In the pressure and temperature range of the upper mantle and TZ we study single crystal wave propagation anisotropy and polarization anisotropy in aggregates with preferred orientation.[4pt] Research supported by NSF EAR-1019853 and EAR-0810272. Computations were performed at the Minnesota Supercomputing Institute.

Núñez Valdez, Maribel; Yu, Yonggang; Wentzcovitch, Renata

2011-03-01

372

Electrical conductivity of olivine, wadsleyite, and ringwoodite under upper-mantle conditions  

PubMed

Geophysical models show that electrical conductivity in Earth's mantle rises about two orders of magnitude through the transition zone in the depth range 410 to 660 kilometers. Impedance measurements obtained on Mg1.8Fe0.2SiO4 olivine, wadsleyite, and ringwoodite at up to 20 gigapascals and 1400 degreesC show that the electrical conductivities of wadsleyite and ringwoodite are similar and are almost two orders of magnitude higher than that of olivine. A conductivity-depth profile to 660 kilometers, based on these laboratory data, shows a conductivity increase of almost two orders of magnitude across the 410-kilometer discontinuity; such a profile favors a two-layer model for the upper mantle. Activation enthalpies of 1.2 to 1.7 electron volts permit appreciable lateral variations of conductivity with lateral temperature variations. PMID:9603726

Xu; Poe; Shankland; Rubie

1998-05-29

373

THE IRRADIATION-INDUCED OLIVINE TO AMORPHOUS PYROXENE TRANSFORMATION PRESERVED IN AN INTERPLANETARY DUST PARTICLE  

SciTech Connect

Amorphization of crystalline olivine to glass with a pyroxene composition is well known from high-energy irradiation experiments. This report is on the first natural occurrence of this process preserved in a chondritic aggregate interplanetary dust particle. The Fe-rich olivine grain textures and compositions and the glass grain compositions delineate this transformation that yielded glass with Fe-rich pyroxene compositions. The average glass composition, (Mg, Fe){sub 3}Si{sub 2}O{sub 7}, is a serpentine-dehydroxylate with O/Si = 3.56 +- 0.25, (Mg+Fe)/Si = 1.53 +- 0.24, and Mg/(Mg+Fe) = 0.74 +- 0.1. These measured atomic ratios match the ratios that have been proposed for amorphous interstellar silicate grains very well, albeit the measured Mg/(Mg+Fe) ratio is lower than was proposed for amorphous interstellar silicate grains, Mg/(Mg+Fe) > 0.9.

Rietmeijer, Frans J. M., E-mail: fransjmr@unm.ed [Department of Earth and Planetary Sciences, MSC 03-2040, 1-University of New Mexico, Albuquerque, NM 87131-0001 (United States)

2009-11-01

374

Crystal size distribution of olivine porphyrocrysts from the M?cinka Basalt (SW Poland)  

NASA Astrophysics Data System (ADS)

The occurrence of basalt in M?cinka (near Jawor) belongs to the Lower Silesian part of the Tertiary Central European Volcanic Province, extending from the Eifel Mts. in Germany through the Czech Republic to Lower Silesia. Volcanic activity began at the turn of the Eocene and Oligocene and lasted up to early Miocene. Here, we present data on chemical composition of basalt from M?cinka, chemical composition of individual minerals and crystal size distribution of olivine phenocrysts. Crystal size distribution (CSD) of olivine porphyrocrysts from volcanic rocks can be used to reconstruct rates of magma crystalization. They provide insight into the variations in nucleation and growth rates with time. Large crystals can give us information on crystallization before eruption, and small crystal give us information on crystallization after eruption. Here, we compare the information from mineral chemistry with that from CSD to reconstruct stages of basaltic magma crystallization. The M?cinka basalt is exposed in a quarry and forms two lava flows, overlain and interbedded by tuffs. Tertiary sedimentary rocks, lying on the Paleozoic metamorphic schists, occur below the lower lava flow. The thickness of the flows reaches maximum of 100 m. The rock is strongly cracked, in some places the cracks are irregular and wavy, and in some, they are regular and form columnar jointing. According to TAS, two types of basaltoids occur, i.e., basalt and basanite. In both types olivine, and rarely clinopyroxene, occur as phenocrysts and the matrix consists of plagioclase, Al - diopside, Ti magnetite/ilmenite, nepheline and glass.. The olivine is characterized by variable degrees of alteration. The major differences between basalt and basanite are observed in composition of olivine phenocrysts. In basalt two types of olivine phenocrysts occur. The first type typically contains 74 % Fo in cores to 68 % in margins. The second type contains 80 % Fo in cores to 75 % in margins. Olivine porphyrocrysts from basanite rocks typically contain 85 % Fo in cores to 80 % in margins. Pyroxene porphyrocrysts from both groups have similar Mg/(Mg+Fe) ratios from 85% (core) - 71 % (rim). Composition of matrix minerals is also similar between basalt and basanite. Plagioclase is zoned, contains up to 70 % of anorthite in cores and from 16 to 58 % in margins. Pyroxenes have the composition of Al-rich diopside, Mg/(Mg+Fe) varies from 68 % to 80 %. We measured sizes of olivine crystals in thin sections and plotted them against population densities. Two types of patterns with different slopes are seen for the rocks from M?cinka. Basalt is characterized by 0,10 - 0,16 values of G (growth rates) multiply t (crystalization time) for small crystals, and 0,20 - 0,28 for large crystals. On the other hand, basanite is characterized by 0,08 - 0,11 values for small crystals and 0,18 - 0,21 for large crystals. Difference in Gt values for large crystals is significant between basalt and basanite. It is consistent with long residence times and slow crystallization of the largest phenocrysts. Values of Gt for small crystals do not vary so much between basalt and basanite and probably reflect slightly different cooling rates after eruption. Both groups probably represent different stages of eruption or different lava flows.

Ja?wa, Aleksandra; Pietranik, Anna

2010-05-01

375

Tracking early melt differentiation in Ugandan potassic rocks using trace elements in olivine phenocrysts  

NASA Astrophysics Data System (ADS)

Olivine is commonly the earliest abundant crystallizing phase in mafic igneous rocks, and therefore has the potential to record information about melts closer to the original, unfractionated compositions than other, better studied, phenocryst phases such as clinopyroxene. Here, the trace element abundances in olivine phenocrysts in ugandite from the Toro Ankole volcanic field and leucite basanite from the Virunga volcanic field in the western branch of the East African Rift are reported for up to 34 trace elements by Laser-ICP-MS with detection limits as low as 1ppb. The ugandites contain abundant olivine phenocrysts of varying sizes, prompting the suspicion that many olivines may be xenocrystic. In the leucite basanites, olivine phenocrysts are less common than clinopyroxene. To investigate the best method of analysis of trace elements in olivine, analyses were compared from cylindrical ablation holes ("point analyses") with varying ablation crater diameters (40-140µm) and from line scans peformed by automatically moving the sample stage beneath a rectangular 100 x 10µm laser beam. Both methods allow identification of subtle zonations from core to rim, whereas the line scan analyses potentially allow characterization of larger crystals and the chemical effects of contamination along cracks. Results show that line scan analyses are contaminated in several elements (Al, Ca, Cu, Ga, Sr, Zr, Nb, La and Ce) that are also concentrated in microcracks between subgrains. This indicates that contamination is due to smearing out of material contained along subgrain boundaries during polishing, and is not due to the choice of polishing agent itself. These tests demonstrate that large diameter large spot analyses produce the best results for trace elements in olivine. In the ugandites, trace element concentrations are remarkably uniform between large and small phenocrysts that show a small range in Mg# (91.8-86.4). Zonation is seen in elements with cation charges from 5+ to 2+ (P, Ti, Zr, Cr, Al, Sc, V, Cu, Mn, Ni) and show correlation between Ti and Al, but not P. Zonation patterns do not conform simply to those identified in basaltic rocks, and also not to a simple increase in diffusion rates with decreasing cation charge. Early phenocryst cores with slightly higher Li or Ni, lower Mn, or enrichments in many trace elements can be identified, whereas the very rare xenocrysts have exceptionally low Na, Cr, Ti, V and Co. Partition coefficients for Ni are 31-35, less than in lamproites, with which they demonstrate an approximately linear correlation between D(Ni) and K2O content, K2O/Al2O3 and K2O/Na2O of the melt, but no correlation with SiO2 content or Mg#. D-values for Cr, Mn and Co overlap with those of basalts, whereas those for Sc (0.011-0.018), Zn (0.44-0.49) and Ga (0.006-0.007) are lower. D(V) of various potassic rocks (0.015 in the Ugandan rocks) confirms the dependence on fO2 calibrated by the Fe3+/(Fe3++Fe2+) of spinels. The V/Sc ratios of the ugandites indicate log fO2 of the source slightly above the FMQ buffer. Leucite basanites have olivines with a greater range of Mg# (92.6 to 70.5) and consequently more variability in trace elements. The more fractionated lecuite basanites (Mg# 59) have less fractionated LREE/HREE than MgO-rich ugandites (Mg# 75-80).

Foley, Stephen; Jacob, Dorrit; O'Neill, Hugh

2010-05-01

376

Shock-induced ringwoodite rims around olivine fragments in melt vein of Antarctic chondrite GRV022321 : Transforma-tion Mechanism  

NASA Astrophysics Data System (ADS)

Here we report electron microprobe (EMAP), Raman spectroscopy, and FIB-transmission electron microscopy (TEM) results of the ringwoodite rims around olivine cores in shock-induced melt veins of the Antarctic chondrites GRV022321. The purpose of this study is to elucidate the mechanisms of transformation and Mg-Fe diffusion of the olivine to ringwoodite, and estimate the shock duration using kinetics. GRV022321 chondrite has a network of black veins which enclose abundant host-rock fragments of olivine, partially trans-formed to ringwoodite. Most of the enclosed fragments have sizes ranging from 5 ?m to 30 ?m, with a brighter rim up to several ?m wide and a dark core in reflected light and BSE images. The Raman data reveal that the rim mineral is ringwoodite, and the core minerals are dominated by olivine with minor ringwoodite. EMAP data confirm that the ringwoodite in rim is richer in fay-lite (Fa50) than the olivine core (Fa10). The olivine-rich cores are heterogeneous with variable BSE contrast, and some points have the same Fa value as the host olivine Fa 23. The occurrence of the rounded and smooth grains of partially transformed olivine embedded in the fine matrix in shock-induced melt veins indicates that they were host-rock fragments entrained into the shock melt. The rims of these entrained oli-vines transformed to ringwoodite by solid-state transformation. The variable extent of transformation is likely a result of local temperature variations within the entrained olivines, with the hotter rim regions transforming to ringwoodite. Iron partitioned into the ringwoodite from the cooler olivine core by Mg-Fe interdiffusion. This Fe interdiffusion implies that either the diffusion was very rapid or that the shock duration was very long. We are using ringwoodite growth rates and Fe-Mg diffusion to explore transformation temperatures and times for the growth of fayalite-rich ringwoodite rims. This will be discussed in the context of impact processes.

Xie, Z.; Liu, X.; Sharp, T. G.; De Carli, P. S.

2011-12-01

377

Coexisting garnets and ilmenites synthesized at high pressures from pyrolite and olivine basanite and their significance for kimberlitic assemblages  

Microsoft Academic Search

Coexisting garnets and ilmenites have been synthesized at high pressure (21–40 kb) within the temperature range between 900 and 1100 °C from pyrolite-less-40% olivine and olivine basanite with various water contents. The two compositions yield phases with a range in the 100 Mg\\/Mg+Fe ratio for both garnet (41–76) and ilmenite (15–47). The distribution coefficient for iron and magnesiaum (KD(Fe, Mg)ilm-ga=

D. H. Green; N. V. Sobolev

1975-01-01

378

Alkali Olivine Basalt dredged near St. Paul's Rocks, Mid-Atlantic Ridge  

Microsoft Academic Search

RECENT studies of deep sea basalts have revealed the great predominance of olivine tholeiites over both normative nepheline and normative quartz basalts1. An alkali basalt recently dredged between 2,950 and 1,975 m near St. Peter and St. Paul Rocks (St. Paul's Rocks) consequently seemed worthy of prompt description. Although mentioned in an abstract2, we have not previously published a chemical

William G. Melson; Eugene Jarosewich; Richard Cifelli; GEOFFREY THOMPSON

1967-01-01

379

Experimental Investigation of the Dissolution and Alteration of Olivine at Low Temperatures and Pressures  

Microsoft Academic Search

We have determined the surface characteristics of single crystals of olivine that have been altered under a variety of experimental conditions relevant to processes occurring on the Martian surface and in shallow crustal environments (i.e. mid-ocean ridge systems and hydrothermal environments). Most previous experiments have focused on dissolution rates of mineral powders at near-surface conditions of temperature (25 °C), pressure

M. T. Deangelis; T. C. Labotka; D. R. Cole

2007-01-01

380

Experimental deformation of olivine single crystals at mantle pressures and temperatures  

NASA Astrophysics Data System (ADS)

Deformation experiments were carried out in a deformation-DIA high-pressure apparatus (D-DIA) on oriented San Carlos olivine single crystals, at pressure ( P) ranging from 3.5 to 8.5 GPa, temperature ( T) from 1373 to 1673 K, and in poor water condition. Oxygen fugacity ( fO 2) was maintained within the olivine stability field and contact with enstatite powder ensured an orthopyroxene activity aopx = 1. Two compression directions were tested, promoting either [1 0 0] slip alone or [0 0 1] slip alone in (0 1 0) crystallographic plane, here called, respectively, a-slip and c-slip. Constant applied stress ( ?) and specimen strain rates ( ??) were monitored in situ using time-resolved X-ray synchrotron diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of run products revealed that dislocation creep was responsible for sample deformation. Comparison of the obtained high- P deformation data with the data obtained at room- P by Bai et al. [Bai, Q., Mackwell, S.L., Kohlstedt D.L., 1991, High-temperature creep of olivine single crystals. 1. Mechanical results for buffered samples, Journal of Geophysical Research, 96, 2441-2463] - on identical materials deformed at comparable T- ?- fO 2- aopx conditions - allowed quantifying the P effect on a-slip and c-slip rheological laws. A slip transition with increasing pressure, from dominant a-slip to dominant c-slip, is documented. a-slip appears sensitive to pressure, which translates into the high activation volume Va*=12±4 cm/mol in the corresponding rheological law, while pressure has little effect on c-slip with Vc*=3±4 cm/mol. These results may explain the discrepancy between olivine low- P and high- P deformation data which has been debated in the literature for more than a decade.

Raterron, Paul; Amiguet, Elodie; Chen, Jiuhua; Li, Li; Cordier, Patrick

2009-01-01

381

Ca-Fe-Mg olivines: phase relations and a solution model  

Microsoft Academic Search

Reversed phase equilibrium experiments in the system (Ca, Mg, Fe)2SiO4 provide four tielines at P?1 bar and 1 kbar and 800 C–1,100 C. These tielines have been used to model the solution properties\\u000a of the olivine quadrilateral following the methods described by Davidson et al. (1981) for quadrilateral clinopyroxenes. The\\u000a discrepancy between the calculated phase relations and the experimentally determined

Paula M. Davidson; Dilip K. Mukhopadhyay

1984-01-01

382

Orthorhombic perovskite phases observed in olivine, pyroxene and garnet at high pressures and temperatures  

Microsoft Academic Search

Ferromagnesian silicate olivines, pyroxenes and garnets with Mg\\/(Mg + Fe)>~0.3 (molar) have been found to transform to high-pressure phases characterized by the orthorhombic perovskite structure when compressed to pressures above 250 kbar in a diamond-anvil press and heated to temperatures above 1,000°C with a YAG laser. The zero-pressure density of the perovskite phase of (Mg,Fe)SiO3 is about 3-4% greater than

Lin-Gun Liu

1976-01-01

383

Oxygen isotope heterogeneity of the mantle beneath the Canary Islands: insights from olivine phenocrysts  

Microsoft Academic Search

A relatively narrow range of oxygen isotopic ratios (?\\u000a 18O = 5.0–5.4‰) is preserved in olivine of mantle xenoliths, mid-ocean ridge (MORB), and most ocean island basalts (OIB). The\\u000a values in excess of this range are generally attributed either to the presence of a recycled component in the Earth’s mantle\\u000a or to shallow level contamination processes. A viable way forward to trace

Andrey A. GurenkoIlya; Ilya N. Bindeman; Marc Chaussidon

2011-01-01

384

Crystal melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene  

Microsoft Academic Search

Mineral melt partition coefficients of all noble gases (min\\/meltDi) have been obtained for olivine (ol) and clinopyroxene (cpx) by UV laser ablation (213 nm) of individual crystals grown from melts at 0.1 GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems

Veronika S. Heber; Richard A. Brooker; Simon P. Kelley; Bernard J. Wood

2007-01-01

385

Neon diffusion kinetics in olivine, pyroxene and feldspar: Retentivity of cosmogenic and nucleogenic neon  

NASA Astrophysics Data System (ADS)

We performed stepwise degassing experiments by heating single crystals of neutron- or proton-irradiated olivine, pyroxene and feldspar to study diffusion kinetics of neon. This is important in evaluating the utility of these minerals for cosmogenic 21Ne measurements and, potentially, for Ne thermochronometry. Degassing patterns are only partially explained by simple Arrhenius relationships; most samples do not exhibit a precisely-determined activation energy in an individual diffusion domain. Regardless, we find clear differences in diffusion kinetics among these minerals. Based on sub-selected data, our estimates for neon diffusion kinetics (activation energy Ea and pre-exponential factor Do, assuming the analyzed fragments approximate the diffusion domain) in each mineral are as follows: for the feldspars, Ea ranges from ˜65 to 115 kJ/mol and Do from 3.9 × 10-3 to 7.1 × 102 cm2s-1; for the pyroxenes, Ea ranges from ˜292 to 480 kJ/mol and Do from 1.6 × 102 to 2.9 × 1011 cm2s-1; for the olivines, Ea ranges from ˜360 to 370 kJ/mol and Do from 1.5 × 106 to 5.0 × 106 cm2s-1. Differences in these parameters are broadly consistent with the expected effect of structural differences between feldspar, and olivine and pyroxene. These results indicate that cosmogenic 21Ne will be quantitatively retained within olivine and pyroxene at Earth surface temperatures over geological timescales. The diffusion kinetics for feldspars, on the other hand, predicts that 21Ne retention at Earth surface temperatures will vary significantly with domain size, crystal microtexture, surface temperature, and exposure duration. Quantitative retention is expected only in favorable conditions. This conclusion is reinforced by additional measurements of cosmogenic 21Ne in coexisting quartz and feldspar from naturally irradiated surface samples; sanidine from a variety of rhyolitic ignimbrites exhibits quantitative retention, whereas alkali-feldspar from several granites does not.

Gourbet, Loraine; Shuster, David L.; Balco, Greg; Cassata, William S.; Renne, Paul R.; Rood, Dylan

2012-06-01

386

Melt segregation, strain partitioning, olivine CPO, and the origin of seismic anisotropy in oceanic lithosphere  

Microsoft Academic Search

Early in the development of the theory of plate tectonics, seismic anisotropy in the upper mantle beneath the ocean basins was associated with mantle flow-induced crystallographic preferred orientation (CPO) of olivine. Now, seismologists are able to resolve depth-dependent anisotropy in oceanic lithosphere with surface waves, and perform detailed regional studies with P-and S-wave tomography to understand the spatial distribution of

B. K. Holtzman; D. L. Kolhstedt; M. E. Zimmerman; J. Kendall

2003-01-01

387

Diffusion-driven magnesium and iron isotope fractionation in Hawaiian olivine  

NASA Astrophysics Data System (ADS)

Diffusion plays an important role in Earth sciences to estimate the timescales of geological processes such as erosion, sediment burial, and magma cooling. In igneous systems, these diffusive processes are recorded in the form of crystal zoning. However, meaningful interpretation of these signatures is often hampered by the fact that they cannot be unambiguously ascribed to a single process (e.g., magmatic fractionation, diffusion limited transport in the crystal or in the liquid). Here we show that Mg and Fe isotope fractionations in olivine crystals can be used to trace diffusive processes in magmatic systems. Over sixty olivine fragments from Hawaiian basalts show isotopically fractionated Mg and Fe relative to basalts worldwide, with up to 0.4‰ variation in 26Mg/ 24Mg ratios and 1.6‰ variation in 56Fe/ 54Fe ratios. The linearly and negatively correlated Mg and Fe isotopic compositions [i.e., ? 56Fe = (- 3.3 ± 0.3) × ? 26Mg], co-variations of Mg and Fe isotopic compositions with Fe/Mg ratios of olivine fragments, and modeling results based on Mg and Fe elemental profiles demonstrate the coupled Mg and Fe isotope fractionation to be a manifestation of Mg-Fe inter-diffusion in zoned olivines during magmatic differentiation. This characteristic can be used to constrain the nature of mineral zoning in igneous and metamorphic rocks, and hence determine the residence times of crystals in magmas, the composition of primary melts, and the duration of metamorphic events. With improvements in methodology, in situ isotope mapping will become an essential tool of petrology to identify diffusion in crystals.

Teng, Fang-Zhen; Dauphas, Nicolas; Helz, Rosalind T.; Gao, Shan; Huang, Shichun

2011-08-01

388

Structural and chemical alteration of crystalline olivine under low energy He+ irradiation  

Microsoft Academic Search

We present the results of irradiation experiments on crystalline olivine with He+ ions at energies of 4 and 10 keV and fluences varying from 5 1016 to 1018 ions\\/cm2. The aim of these experiments is to simulate ion implantation into interstellar grains in shocks in the ISM. Irradiated samples were analysed by transmission electron microscopy (TEM). The irradiation causes the

K. Demyk; Ph. Carrez; H. Leroux; P. Cordier; A. P. Jones; J. Borg; E. Quirico; P. I. Raynal; L. d'Hendecourt

2001-01-01

389

Fundamentals of elasticity of (Mg1?x, Fex)2SiO4 olivine  

Microsoft Academic Search

We study the influence of iron on the elasticity of (Mg1?x, Fex)2SiO4 olivine (0 ? x ? 0.125), a major constituent of the Earth's upper mantle. We calculate static elastic properties by first principles for this solid solution and investigate the effect of atomic arrangement, an artifact of supercell calculations, on all single crystal and poly-crystalline elastic moduli. From calculated

M. Núñez-Valdez; K. Umemoto; R. M. Wentzcovitch

2010-01-01

390

Crossover of cation partitioning in olivines: a combination of ab initio and Monte Carlo study  

Microsoft Academic Search

We report studies based on a combination of ab initio electronic structure and Monte Carlo (MC) technique on the problem of\\u000a cation partitioning among inequivalent octahedral sites, M1 and M2 in mixed olivines containing Mg2+ and Fe2+ ions. Our MC scheme uses interactions derived out of ab initio, density functional calculations carried out on measured crystal\\u000a structure data. Our results

Swastika Chatterjee; Sirshendu Bhattacharyya; Surajit Sengupta; Tanusri Saha-Dasgupta

2011-01-01

391

Comprehensive paleomagnetic study of a succession of Holocene olivine-basalt flow: Xitle Volcano (Mexico) revisited  

Microsoft Academic Search

A detailed paleomagnetic study of a young Late Holocene olivine-basalt flow from the Xitle volcano in the southern Basin of Mexico was completed to evaluate the consistency and reliability of the record derived from fresh well-preserved and exposed lava flows. One-hundred oriented standard paleomagnetic cores corresponding to 10 different lava effusion episodes were collected from unit-flow V. Thermomagnetic analyses show

Luis M. Alva-Valdivia

2005-01-01

392

Electron microscopy of high-pressure phases synthesized from natural olivine in diamond anvil cell  

Microsoft Academic Search

The products of the transformation of natural (Mg0.83Fe0.17)2SiO4 olivine have been prepared at various high pressures (between 25 GPa and 90 GPa), and high temperature in a laser-heated diamond-anvil cell (DAC). Studies of the high-pressure phases have been made by transmission electron microscopy (TEM), and X-ray microanalysis.

M. Madon; F. Guyot; J. Peyronneau; J. P. Poirier

1989-01-01

393

Petrogenetic significance of minor elements in olivines from diamonds and peridotite xenoliths from kimberlites of Yakutia  

Microsoft Academic Search

Peridotite xenoliths and diamonds from kimberlites represent an important source of information about the composition of the continental lithosphere at depths exceeding 120–150 km. Ultramafic (or peridotitic) U(P)-type of geological environment is dominating at these depths compared to eclogitic (E-type). Olivine is the most typical mineral both of peridotite xenoliths and as diamond inclusions in most kimberlites worldwide. In spite of

N. V. Sobolev; A. M. Logvinova; D. A. Zedgenizov; N. P. Pokhilenko; E. V. Malygina; D. V. Kuzmin; A. V. Sobolev

2009-01-01

394

Two-Stage Deformation of Olivine Aggregates with Changing Deformation Kinematics  

NASA Astrophysics Data System (ADS)

Two-stage deformation experiments have been conducted on synthetic olivine aggregates to investigate the influence of pre-existing fabric on the evolution of lattice-preferred orientation (LPO), seismic anisotropy, and grain morphology. This study is motivated by recent work on naturally and experimentally deformed peridotites, which suggest that the alignment of olivine axes with the shear plane requires more strain in samples with a strong pre-existing LPO than in samples with weak or random LPO. In the first stage of deformation, aggregates synthesized from San Carlos olivine are deformed at P = 1 GPa and T = 1500 K in a triaxial geometry to produce axi-symmetric LPOs of varying strength. In a second stage of deformation, the aggregates are re-deformed in simple shear to varying shear strains. Microstructural analyses are performed after each step (synthesis, triaxial deformation, simple shear deformation) using optical microscopy and electron backscatter diffraction (EBSD). These results are compared to numerical models of microstructural evolution. Our results provide constraints on the evolution of LPO and consequent seismic signature as a function of preexisting rock fabric. These data are necessary to interpret seismic anisotropy in settings where kinematics are complex, such as mid-ocean ridges and subduction zones.

Mahan, B. M.; Skemer, P. A.; Griera, A.

2011-12-01

395

Effects of Temperature and Composition on Spectral Features of the Olivine minerals.  

NASA Astrophysics Data System (ADS)

Crystalline olivine minerals (Mg2xFe(2-2x)SiO4 ; x=[0,1] ) has been detected in many astronomical environments. The Infrared Space Observatory (ISO), Spitzer Space Telescope, Herschel Space Telescope detected several sharp near and far infrared (IR) spectral features around young stars, comets and evolved stars, which have been attributed to crystalline silicates (mostly as forsterite, Mg2SiO4, the Mg-rich end member of the olivine series). Laboratory measurements of the different mineral spectral features are compared to astronomical observations in order to match and identify the dust species present in circumstellar envelopes. However, the positions, widths and amplitudes of the spectral features are strongly influenced by the temperature and composition of the dust grains. Consequently there is degeneracy such that a given spectral feature may have more than one explanation. We present these competing effects for crystalline olivine minerals and investigate how the spectral features change in position, shape and strength with varying Mg/[Mg+Fe] ratio and with temperature and develop a scheme for mapping the degeneracy space. Our goal is to determine to what extent this degeneracy can be broken observationally in order to improve our understanding of astromineralogy around the evolved stars.

Guha Niyogi, Suklima; Speck, A.; Dijkstra, C.

2011-01-01

396

The infrared signature of water associated with trivalent cations in olivine  

NASA Astrophysics Data System (ADS)

Forsterite crystals were synthesised under water saturated conditions at 1400 °C and 1.5 GPa doped with trace amounts of either B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ga, Y, Zr, In, Sm, Gd, Dy, Tm, or Lu. The common and intense hydroxyl stretching bands in the infrared spectra of spinel peridotite olivine, at 3572 and 3525 cm -1, were only reproduced in the presence of Ti. Those samples where the trace element substitutes as the trivalent cation on the Mg 2+ site were identified from a systematic variation in concentration with the trivalent ionic radius. The hydroxyl region of all samples is essentially identical except for between 3300 and 3400 cm -1. This region is characterised by one or more bands, with the energy of the most intense feature being correlated with the ionic radius of the trivalent cation. The integrated intensity of these hydroxyl bands also correlates with the concentration of the trivalent cation. These correlations provide unambiguous evidence that bands, or peaks, in this region correspond to water at defect sites associated with trivalent cations. "Trivalent peaks" are sometimes observed in samples of mantle olivine and most likely indicate water associated with Fe 3+. The water at this site is not incorporated under normal mantle conditions and should not be included in estimates of the water capacity of mantle olivine. These results emphasise the importance of identifying the infrared signature of different water substitution mechanisms.

Berry, Andrew J.; O'Neill, Hugh St. C.; Hermann, Jörg; Scott, Dean R.

2007-09-01

397

First-principles calculations of equilibrium Mg isotope fractionations between garnet, clinopyroxene, orthopyroxene, and olivine: Implications for Mg isotope thermometry  

NASA Astrophysics Data System (ADS)

Equilibrium fractionation factors of Mg isotopes at high temperature and pressure are investigated for pyrope, majorite, clinopyroxene, orthopyroxene, and olivine using density functional theory. The calculated equilibrium fractionation factors are in good agreement with previous study (Schauble, 2011), suggesting that our calculations are reliable and accurate. The results reveal significant inter-mineral Mg isotope fractionations due to different coordination environment of Mg in minerals. Specifically, pyrope, where Mg is in eight-fold coordination, is more enriched in light Mg isotopes than olivine and pyroxene where Mg is in six-fold coordination. The calculated isotope fractionation for Mg isotopes between clinopyroxene and pyrope is consistent with observations from natural eclogites (Li et al., 2011; Wang et al., 2012). Our calculation also reveals substantial pressure effect on Mg isotope fractionations among garnet, pyroxene, and olivine. Equilibrium fractionation of Mg isotopes between pyrope and pyroxene (and olivine) could be used as a novel and independent thermometry with precision much better than the traditional garnet-clinopyroxene Fe-Mg exchange thermometry because such fractionation is significantly greater than the current uncertainties of Mg isotope analyses (˜0.05‰ amu-1). These Mg isotope thermometries could have wide applications in high-temperature mafic igneous and metamorphic rocks where garnet co-exists with pyroxene or olivine. Equations for equilibrium Mg isotope fractionation factors between garnet (pyrope and majorite) and pyroxene and between garnet and olivine as a function of temperature and pressure are also presented in this study.

Huang, Fang; Chen, Lijuan; Wu, Zhongqing; Wang, Wei

2013-04-01

398

Geoengineering impact of open ocean dissolution of olivine on atmospheric CO2, surface ocean pH and marine biology  

NASA Astrophysics Data System (ADS)

Ongoing global warming induced by anthropogenic emissions has opened the debate as to whether geoengineering is a ‘quick fix’ option. Here we analyse the intended and unintended effects of one specific geoengineering approach, which is enhanced weathering via the open ocean dissolution of the silicate-containing mineral olivine. This approach would not only reduce atmospheric CO2 and oppose surface ocean acidification, but would also impact on marine biology. If dissolved in the surface ocean, olivine sequesters 0.28 g carbon per g of olivine dissolved, similar to land-based enhanced weathering. Silicic acid input, a byproduct of the olivine dissolution, alters marine biology because silicate is in certain areas the limiting nutrient for diatoms. As a consequence, our model predicts a shift in phytoplankton species composition towards diatoms, altering the biological carbon pumps. Enhanced olivine dissolution, both on land and in the ocean, therefore needs to be considered as ocean fertilization. From dissolution kinetics we calculate that only olivine particles with a grain size of the order of 1 ?m sink slowly enough to enable a nearly complete dissolution. The energy consumption for grinding to this small size might reduce the carbon sequestration efficiency by ˜30%.

Köhler, Peter; Abrams, Jesse F.; Völker, Christoph; Hauck, Judith; Wolf-Gladrow, Dieter A.

2013-03-01

399

Relict olivine grains, chondrule recycling, and implications for the chemical, thermal, and mechanical processing of nebular materials  

NASA Astrophysics Data System (ADS)

Chondrules and isolated forsterites in five low-subtype ordinary chondrites [NWA 3127 (LL3.1), Sahara 97210 (LL3.2), Wells (LL3.3), Chainpur (LL3.4), and Sahara 98175 (LL3.5)] were studied using petrographic, EMPA, and SIMS techniques to better constrain the origin of chondrules and the olivine grains within them. Our results imply that igneous crystallization, vapor fractionation, redox effects, and open-system behavior were important processes. All olivine grains, including normal, relict, and isolated forsterite grains, show evidence for igneous fractionation under disequilibrium conditions, with olivine crystallizing during rapid cooling (closer to 2000 °C/h than to 100 °C/h). Vapor fractionation is manifested by anti-correlated abundances between refractory elements (Al, Sc, Y, Ti, Ca, V) and volatile elements (Cr, Mn, P, Rb, Fe) in olivine. Redox effects are evidenced in various ways, and imply that Fe, Co, Ni, and P were partitioned more into metal, and V was partitioned more into olivine, under reducing conditions in the most FeO-poor melts. There is no obvious evidence for systematic variations in olivine composition according to meteorite subtype, but shock melting in Sahara 97210 resulted in the injection of glass-derived melt into olivine, resulting in artificially high abundances of Ba, Sr, Na, Ti, and some other incompatible elements in olivine. Terrestrial weathering in a hot desert environment may have mobilized Ba and Sr in some glasses. Our data suggest that chondrules in ordinary chondrites experienced repeated thermal, chemical, and mechanical processing during a "recycling" process over an extended time period, which involved multiple episodes of melting under fluctuating redox and heating conditions, and multiple episodes of chondrule break-up in some cases. Forsterite grains, including normal grains in forsterite-bearing type I chondrules, the cores of isolated forsterites, and relict forsterite in type II chondrules, all crystallized from similar, refractory melts under reducing conditions; relict Mg-olivine and isolated forsterite grains were thus derived from type I chondrules. Olivine in type II chondrules, including normal grains and ferroan overgrowths on relict Mg-olivine, crystallized from more volatile-rich, oxidized, and relatively unfractionated melts. Relict dusty olivine grains in type I chondrules were derived from type II chondrules during incomplete melting episodes involving reduction and some vaporization, with clear (non-dusty) grains in dusty olivine-bearing chondrules crystallizing from the reduced and partly vaporized melts. Melt compositions parental to normal olivine grains in type I and II chondrules are systematically enriched in refractory elements compared to bulk chondrule compositions, implying that chondrules often experienced open-system exchange with more volatile-rich surroundings after some olivine had crystallized, possibly while the chondrules were still partly molten. Type II chondrules could have been derived from type I chondrules by the addition of relatively volatile-rich material, followed by re-melting and little evaporation under oxidizing conditions. In contrast, type I chondrules could have been derived from type II chondrules by re-melting involving more-or-less evaporation under reducing conditions. Chemical, oxygen isotope, and petrographic data are best accommodated by a model in which there were several (>2-3, sometimes ?4-5) melting episodes for most chondrules in ordinary chondrites.

Ruzicka, Alex; Floss, Christine; Hutson, Melinda

2008-11-01

400

Magnetite-orthopyroxene symplectites in gabbros of the Urals: A structural track of olivine oxidation  

NASA Astrophysics Data System (ADS)

The chemical compositions of magnetite-orthopyroxene symplectites (MOS) and rock-forming minerals—olivine (Ol), clinopyroxene (Cpx), and magnetite(Mt)—have been studied in 20 samples of olivine-bearing rocks in the Urals, including troctolite, olivine gabbro, and gabbronorite. MOS are orthopyroxene (Opx) monocrystals up to 500 ?m in size containing myrmekite-like magnetite intergrowths up to 20-30 ?m in width. According to the microprobe examination, the dark-colored minerals are characterized by a high Fe mole fraction F = Fe/(Fe + Mg) = 0.20-0.50, whereas F = 0.33-0.65 is typical of the bulk rock compositions. The plagioclase varies in composition from An90 to An50. No significant compositional difference has been established between the MOS and rock-forming minerals. The F opx and F Ol are closely correlated (linear trend, r = 0.97); F Ol/ F Opx is ˜1.2. Similarly, a positive correlation between F Opx and F Cpx is noted (linear trend, r = 0.90); F Opx/ F Cpx is ˜1.2. The crystallization temperature of the Ol-Opx-Cpx assemblage is roughly estimated at 700-800°C. A high positive correlation ( r = 0.95) is established between the TiO2 contents in the magnetites from the MOS (Mt1) and host rock (Mt2). The Mt1/Mt2 ratio reaches ˜0.8, implying that Mt1 contains somewhat less TiO2 than Mt2. Hence, the rock-forming and MOS minerals make up an equilibrium assemblage. As follows from the structural pattern, symplectites were formed as products of the reaction between olivine and oxygen in the solid state with the entire volume of the rock involved in the oxidation; i.e., the distance of the diffusion was significant. Free oxygen appeared as a product of the dissociation of the water penetrating into the hot gabbro and ultramafic rocks at the initial stage of the tectonic extension and high-temperature hydration. According to the redox state of dunite coexisting with gabbro, the oxygen fugacity is estimated at +2.7 log units of fO2 relative to the QFM buffer. The structure and products of the olivine oxidation were eventually obliterated in the course of the hydration.

Efimov, A. A.; Malitch, K. N.

2012-12-01

401

Anisotropic lattice thermal diffusivity in olivines and pyroxenes to high temperatures  

NASA Astrophysics Data System (ADS)

The anisotropic lattice thermal diffusivity of three olivines (Fo 0, Fo78, and Fo91), one orthopyroxene (En 91), and one clinopyroxene (Di72He9Jd3Cr 3Ts12) have been measured via impulsive stimulated light scattering, permitting the calculation of their lattice thermal diffusivity tensors to high temperatures. For Fo0 olivine, measurements extend from room temperature to 600°C, for Fo78 to 900°C, and for Fo91 to 1000°C, all in steps of 100°C. The orthopyroxene also was taken in steps to 1000°C, while the clinopyroxene was measured at room temperature. A limited set of room-temperature measurements to 5 GPa on a fourth olivine (Fo89) is also included. Diffusivities have been combined with calculations of density and specific heat to determine the lattice thermal conductivity tensors. An earlier theory that explains the observed behavior in terms of a positive lower bound on the phonon mean free path is discussed, and the data are used to constrain a model of thermal conductivity at high temperature. The relative contributions of optic and acoustic modes are evaluated from analysis of published dispersion curves. Five conclusions are reached: First, the anisotropy of lattice thermal conductivity remains essentially unchanged over the observed range of temperatures, indicating that anisotropy remains significant under upper-mantle conditions, and, in regions displaying preferred alignment, may account for observed lateral variations in the geotherm. Second, thermal conductivity departs significantly from earlier predictions of its temperature dependence; this may be understood in terms of a phonon mean free path that cannot diminish below 1.75 times the mean interatomic spacing. Third, for olivine, the optic modes have group velocities that are approximately one-third those of the acoustic modes, and do not dominate lattice conduction despite their greater number. Fourth, impurity scattering is significant along the olivine Fe-Mg solid solution series, but is not appreciable near the endpoints and therefore likely does not play a major role in the upper mantle. Fifth, the historic underestimation of lattice thermal conductivity at temperature has led to an overestimation of radiative conductivity; radiative transport, although significant, plays an even smaller role in the upper mantle than has heretofore been assumed.

Harrell, Michael Damian

402

Effect of water on the slip systems in olivine single crystals at high pressure  

NASA Astrophysics Data System (ADS)

Seismic velocity anisotropies observed in the upper mantle are interpreted by lattice-preferred orientations (LPO) produced experimentally in olivine, which depends on the dominant dislocation slip systems. At low pressure P<3GPa and mantle temperature, olivine [100] dislocation slip dominates the slip system (over the less active [001] slip) in dry condition. This tends to align crystal fast velocity [100] axis with the principal shear direction. Yet recent high-pressure deformation experiments [1] show that [001](010) slip system becomes dominant over the [100](010) system in the (P,T) range of the deep upper mantle. This may promote a shear-parallel slow-velocity [001] axis and may explain the seismic-velocity attenuation observed at depth >200 km [2]. According to those studies, the slip systems activities depend on pressure. However previous studies revealed that the water could affect the olivine plastic deformation and induce the transition between the [100] slip to the [001] slip. [3] The main goal of this study was to show the effect of water on olivine slip system activities at high pressure. Deformation experiments were carried out in wet condition, at 4GPaolivine single crystals using the Deform