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1

Electrochemical Performance of LiMnPO4 Synthesized with Off-Stoichiometry  

E-print Network

,4 Although LiMnPO4 shows a higher potential5-7 than LiFePO4, the higher energy density of LiMnPO4 can only a more intrinsic kinetic limitation of the material for LiMnPO4 in contrast to LiFePO4 Nature (London), 458, 190 2009 . This is further corroborated by the difference in the overpotential between the two

Ceder, Gerbrand

2

Raman spectroscopy of carbon-coated LiCoPO4 and LiFePO4 olivines  

NASA Astrophysics Data System (ADS)

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 a 4.3 mW laser beam. The mild removal of the carbon layer makes it possible to analyze the details of the LiCoPO4 structure in air without interference from carbon. LiFePO4-C powder, together with carbon layer gasification, undergoes oxidative decomposition by the oxygen with the formation of Li3Fe2(PO4)3 and Fe2O3, even at a laser power of 1 mW. Thus, care should be taken when measuring and interpreting the Raman spectra of this material both in air and in an inert atmosphere, as obvious decomposition of the LiFePO4 olivine structure takes place even at a moderate power of the excitation laser. A comparative study of the stability of these two carbon-coated nano powders under laser beam irradiation and heating was carried out with the use of TGA-mass spectrometry.

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

2011-08-01

3

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

4

Electrical conductivity and reaction with lithium of LiFe 1? y Mn y PO 4 olivine-type cathode materials  

Microsoft Academic Search

Structural, electrical and electrochemical properties of Mn-substituted phospho-olivines LiFe1?yMnyPO4 were investigated and compared to those of LiFePO4. Rietvield refined XRD patterns taken in the course of delithiation process showed apparent difference between phase compositions of these cathode materials upon lithium extraction. Contrary to the LiFePO4 and LiMnPO4 compositions for which a two-phase mechanism of electrochemical lithium extraction\\/insertion is observed, in

J. Molenda; W. Ojczyk; J. Marzec

2007-01-01

5

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

6

Enhanced thermal safety and high power performance of carbon-coated LiFePO4 olivine cathode for Li-ion batteries  

NASA Astrophysics Data System (ADS)

The carbon-coated LiFePO4 Li-ion oxide cathode was studied for its electrochemical, thermal, and safety performance. This electrode exhibited a reversible capacity corresponding to more than 89% of the theoretical capacity when cycled between 2.5 and 4.0 V. Cylindrical 18,650 cells with carbon-coated LiFePO4 also showed good capacity retention at higher discharge rates up to 5C rate with 99.3% coulombic efficiency, implying that the carbon coating improves the electronic conductivity. Hybrid Pulse Power Characterization (HPPC) test performed on LiFePO4 18,650 cell indicated the suitability of this carbon-coated LiFePO4 for high power HEV applications. The heat generation during charge and discharge at 0.5C rate, studied using an Isothermal Microcalorimeter (IMC), indicated cell temperature is maintained in near ambient conditions in the absence of external cooling. Thermal studies were also investigated by Differential Scanning Calorimeter (DSC) and Accelerating Rate Calorimeter (ARC), which showed that LiFePO4 is safer, upon thermal and electrochemical abuse, than the commonly used lithium metal oxide cathodes with layered and spinel structures. Safety tests, such as nail penetration and crush test, were performed on LiFePO4 and LiCoO2 cathode based cells, to investigate on the safety hazards of the cells upon severe physical abuse and damage.

Zaghib, K.; Dubé, J.; Dallaire, A.; Galoustov, K.; Guerfi, A.; Ramanathan, M.; Benmayza, A.; Prakash, J.; Mauger, A.; Julien, C. M.

2012-12-01

7

Hyperfine fields at the Li site in LiFePO(4)-type olivine materials for lithium rechargeable batteries: a (7)Li MAS NMR and SQUID study.  

PubMed

The (7)Li NMR isotropic shift for olivine LiMPO(4) (M = Fe, Mn, Co, Ni) is assigned to hyperfine coupling between the (7)Li nucleus and the transition metal unpaired electrons on the basis of the Curie-Weiss temperature dependence of the shift. The hyperfine shift arises from a linear combination of Li-O-M through-bond interactions wherein the unpaired A' electrons contribute a negative shift and the unpaired A' ' electrons contribute a positive shift. The hyperfine coupling constant is determined for each composition. PMID:11942811

Tucker, Michael C; Doeff, Marca M; Richardson, Thomas J; Fiñones, Rita; Cairns, Elton J; Reimer, Jeffrey A

2002-04-17

8

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. PMID:22222099

2012-01-01

9

Studies on electrochemical behaviour of zinc-doped LiFePO 4 for lithium battery positive electrode  

Microsoft Academic Search

The effects of zinc oxide doping on LiFePO4 have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic measurements. The XRD patterns demonstrate that the samples have the phase of LiFePO4 with an ordered olivine structure indexed to the orthorhombic Pmna space group. Also, XRD patterns show with the presence

Atef Y. Shenouda; Hua K. Liu

2009-01-01

10

Solution Deposition of Thin Carbon Coatings on LiFePO4.  

PubMed

We report the synthesis of ultrathin carbon coatings on polycrystalline LiFePO4 via solution deposition and subsequent annealing. The annealing temperature was systematically investigated with polymer systems on LiFePO4 nanostructures. The crystal structures, sizes, and morphologies were monitored and analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Micro-Raman and TEM were used to interrogate the carbon coatings after heat-treatments. Electrochemical performance of coated materials was investigated by cyclic voltammograms (CVs) and galvanostatic charge-discharge analysis. The olivine structured LiFePO4 remained stable up to 600 °C but underwent a rapid reduction reaction from LiFePO4 to Fe2P above 700 °C. The good compatibility between polyethylene glycol (PEG) and the surface of LiFePO4 enabled the formation of core-shell structure, which was transformed into a thin carbon coating on LiFePO4 after annealing. Both PEG and sucrose carbon-based sources yielded high-quality carbon coatings after annealing, as determined by the graphitic/disordered (G/D) ratios of 1.30 and 1.20, respectively. By producing more uniform and coherent coatings on LiFePO4 particles, batteries with significantly less carbon (i.e., 0.41 wt %) were fabricated and demonstrated comparable performance to traditionally synthesized carbon-coated LiFePO4 with higher carbon loadings (ca. 2.64 wt %). This will enable development of batteries with higher active material loading and therefore significantly larger energy densities. PMID:25387242

Zhu, Jianxin; Yoo, Kevin; El-Halees, Ibrahim; Kisailus, David

2014-12-10

11

Restricted growth of LiMnPO4 nanoparticles evolved from a precursor seed  

NASA Astrophysics Data System (ADS)

Herein, we report on a novel precipitation method to enable LiMnPO4 olivine (LMP) as a cathode material for lithium ion batteries (LIBs) to reach high capacity at high discharge rates. By confining Mn3(PO4)2 precipitation on surface of a precursor seed of Li3PO4, the size of LMP particles is limited to less than 100 nm for a smaller dimension. The cathode material delivers discharge capacities of 145 mAh g-1 at 0.1 C, 112 mAh g-1 at 1 C to 62 mAh g-1 at 5 C (comparable with top three performances [1-3]). Even if precipitation is one of the versatile strategies to prepare the cathode material, it has not been reported that such a first-tier high performance is obtained from LMP prepared by precipitation methods. When compared with LMP particles synthesized by a conventional co-precipitation method, the performances are recognized to be considerably enhanced. Also, the surface-confined precipitation process described in this work does not involve a ball milling step with a conductive agent such as carbon black [1,2,4-10] so that a low cost synthesis is feasible.

Kim, Tae-Hee; Park, Han-Saem; Lee, Myeong-Hee; Lee, Sang-Young; Song, Hyun-Kon

2012-07-01

12

Ion dynamics in nanocrystalline LiMnPO4 synthesised by novel template free hydrothermal approach  

NASA Astrophysics Data System (ADS)

A dense core rectangular shaped nanocrystalline LiMnPO4 material was synthesized by template free sucrose assisted hydrothermal synthesis. The material possess orthorhombic crystal structure with Pnma, space group having four formula units. The structural characterization was accomplished through X-ray diffraction, thermo gravimetry/differential thermal analysis. Morphology was identified by the SEM, VSM was used to verify the magnetic behavior of the material and electrical characterization was done through impedance spectroscopy and the results were reported.

Vijayan, Lakshmi; Cheruku, Rajesh; Govindaraj, G.

2014-04-01

13

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

14

Electrochemical behaviors of solid LiFePO 4 and Li 0.99Nb 0.01FePO 4 in Li 2SO 4 aqueous electrolyte  

Microsoft Academic Search

LiFePO4 and Li0.99Nb0.01FePO4 with olivine structure were synthesized by an in situ synthesis technique. Their electrochemical behaviors in Li2SO4 aqueous electrolytes were investigated by cyclic voltammetry (CV). It shows that both compounds undergo lithium ion extraction and intercalation upon oxidation and reverse reduction at the safe potential window without causing the kinetic electrolysis of water. For LiFePO4, only one pair

C. H. Mi; X. G. Zhang; H. L. Li

2007-01-01

15

A polyethylene glycol-assisted carbothermal reduction method to synthesize LiFePO4 using industrial raw materials  

NASA Astrophysics Data System (ADS)

Olivine LiFePO4 is synthesized by a carbothermal reduction method (CTR) using industrial raw materials with polyethylene glycol (PEG) as a reductive agent and carbon source. A required amount of acetone is added to the starting materials for the ball milling process and the precursor is sintered at 973 K for 8 h to form crystalline phase LiFePO4. The structure and morphology of the LiFePO4/C composite samples have been characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, differential scanning calorimetry and magnetic susceptibility. Electrochemical measurements show that the LiFePO4/C composite cathode delivers an initial discharge capacity of 150 mAh g-1 at a 0.2C-rate between 4.0 and 2.8 V, and almost no capacity loss is observed for up to 50 cycles. Remarkably, the cell can sustain a 30C-rate between 4.6 and 2.0 V, and this rate capability is equivalent to charge or discharge in 2 min. The simple technique, low-cost starting materials, and excellent electrochemical performance make this process easier to commercialize than other synthesized methods.

Fey, George Ting-Kuo; Huang, Kai-Pin; Kao, Hsien-Ming; Li, Wen-Hsien

2011-03-01

16

New solid-state synthesis routine and mechanism for LiFePO 4 using LiF as lithium precursor  

Microsoft Academic Search

Li2CO3 and LiOH·H2O are widely used as Li-precursors to prepare LiFePO4 in solid-phase reactions. However, impurities are often found in the final product unless the sintering temperature is increased to 800°C. Here, we report that lithium fluoride (LiF) can also be used as Li-precursor for solid-phase synthesis of LiFePO4 and very pure olivine phase was obtained even with sintering at

Deyu Wang; Hong Li; Zhaoxiang Wang; Xiaodong Wu; Yucheng Sun; Xuejie Huang; Liquan Chen

2004-01-01

17

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

18

Studies of selected synthesis procedures of the conducting LiFePO 4-based composite cathode materials for Li-ion batteries  

Microsoft Academic Search

In this paper technological aspects of a synthesis of phospho-olivine LiFePO4 based composite cathode materials for lithium batteries are presented. An effective synthesis route yielding a highly conductive composite cathode material was developed. The structural, electrical and electrochemical properties of these materials were investigated. It was shown that the enhanced conductivity of the cathode material is due to the presence

W. Ojczyk; J. Marzec; K. ?wierczek; W. Zaj?c; M. Molenda; R. Dziembaj; J. Molenda

2007-01-01

19

Optimization of carbon coatings on LiFePO 4  

Microsoft Academic Search

The electrochemical performance of LiFePO4 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

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

2006-01-01

20

Effects of Nb-doped on the structure and electrochemical performance of LiFePO4/C composites  

NASA Astrophysics Data System (ADS)

The olivine-type niobium doping Li1-xNbxFePO4/C (x=0, 0.005, 0.010, 0.015, 0.025) cathode materials were synthesized via a two-step ball milling solid state reaction. The effects of Nb doping were charactered by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and galvanostatic charge-discharge. It is found that Nb doping enlarges the interplanar distance of crystal plane parallel to [0 1 0] direction in LiFePO4. In other words, it widens the one dimensional diffusion channels of Li+ along the [0 1 0] direction. Electrochemical test results indicate that the Li0.99Nb0.01FePO4/C composite exhibits the best electrochemical performance with initial special discharge capacity of 139.3 mA h g-1 at 1 C rate. The present synthesis route is promising in making the solid state reaction method more practical for preparation of the LiFePO4 material.

Ma, Zhipeng; Shao, Guangjie; Wang, Guiling; Zhang, Ying; Du, Jianping

2014-02-01

21

Lithium-Ion Insertion Kinetics of Na-Doped LiFePO4 as Cathode Materials for Lithium-Ion Batteries  

NASA Astrophysics Data System (ADS)

Na-doped Li1-x Na x FePO4 (x = 0, 0.05, 0.1, and 0.2) materials were synthesized by a simple high-temperature solid-state method. The structure, morphology, and kinetic performances of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). XRD indicates that all samples are in accordance with the standard LiFePO4 with olivine structure. SEM reveals that the particle size of all samples is about 1 to 2 µm. CV exhibits that Na doping obviously improves the reversibility and dynamic behaviors of lithium intercalation and deintercalation. EIS shows that Na doping decreases the charge transfer resistance of LiFePO4 and improves the lithium diffusion coefficients. It can be concluded that Na doping results in lower electrode polarization and higher lithium-ion diffusion coefficient, which can effectively improve the kinetic performance of LiFePO4.

Zhu, Yan-Rong; Zhang, Rui; Deng, Li; Yi, Ting-Feng; Ye, Ming-Fu; Yao, Jin-Han; Dai, Chang-Song

2015-01-01

22

Mesoporous carbon-coated LiFePO4 nanocrystals co-modified with graphene and Mg2+ doping as superior cathode materials for lithium ion batteries  

NASA Astrophysics Data System (ADS)

In this work, mesoporous carbon-coated LiFePO4 nanocrystals further co-modified with graphene and Mg2+ doping (G/LFMP) were synthesized by a modified rheological phase method to improve the speed of lithium storage as well as cycling stability. The mesoporous structure of LiFePO4 nanocrystals was designed and realized by introducing the bead milling technique, which assisted in forming sucrose-pyrolytic carbon nanoparticles as the template for generating mesopores. For comparison purposes, samples modified only with graphene (G/LFP) or Mg2+ doping (LFMP) as well as pure LiFePO4 (LFP) were also prepared and investigated. Microscopic observation and nitrogen sorption analysis have revealed the mesoporous morphologies of the as-prepared composites. X-ray diffraction (XRD) and Rietveld refinement data demonstrated that the Mg-doped LiFePO4 is a single olivine-type phase and well crystallized with shortened Fe-O and P-O bonds and a lengthened Li-O bond, resulting in an enhanced Li+ diffusion velocity. Electrochemical properties have also been investigated after assembling coin cells with the as-prepared composites as the cathode active materials. Remarkably, the G/LFMP composite has exhibited the best electrochemical properties, including fast lithium storage performance and excellent cycle stability. That is because the modification of graphene provided active sites for nuclei, restricted the in situ crystallite growth, increased the electronic conductivity and reduced the interface reaction current density, while, Mg2+ doping improved the intrinsically electronic and ionic transfer properties of LFP crystals. Moreover, in the G/LFMP composite, the graphene component plays the role of ``cushion'' as it could quickly realize capacity response, buffering the impact to LFMP under the conditions of high-rate charging or discharging, which results in a pre-eminent rate capability and cycling stability.In this work, mesoporous carbon-coated LiFePO4 nanocrystals further co-modified with graphene and Mg2+ doping (G/LFMP) were synthesized by a modified rheological phase method to improve the speed of lithium storage as well as cycling stability. The mesoporous structure of LiFePO4 nanocrystals was designed and realized by introducing the bead milling technique, which assisted in forming sucrose-pyrolytic carbon nanoparticles as the template for generating mesopores. For comparison purposes, samples modified only with graphene (G/LFP) or Mg2+ doping (LFMP) as well as pure LiFePO4 (LFP) were also prepared and investigated. Microscopic observation and nitrogen sorption analysis have revealed the mesoporous morphologies of the as-prepared composites. X-ray diffraction (XRD) and Rietveld refinement data demonstrated that the Mg-doped LiFePO4 is a single olivine-type phase and well crystallized with shortened Fe-O and P-O bonds and a lengthened Li-O bond, resulting in an enhanced Li+ diffusion velocity. Electrochemical properties have also been investigated after assembling coin cells with the as-prepared composites as the cathode active materials. Remarkably, the G/LFMP composite has exhibited the best electrochemical properties, including fast lithium storage performance and excellent cycle stability. That is because the modification of graphene provided active sites for nuclei, restricted the in situ crystallite growth, increased the electronic conductivity and reduced the interface reaction current density, while, Mg2+ doping improved the intrinsically electronic and ionic transfer properties of LFP crystals. Moreover, in the G/LFMP composite, the graphene component plays the role of ``cushion'' as it could quickly realize capacity response, buffering the impact to LFMP under the conditions of high-rate charging or discharging, which results in a pre-eminent rate capability and cycling stability. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04611g

Wang, Bo; Xu, Binghui; Liu, Tiefeng; Liu, Peng; Guo, Chenfeng; Wang, Shuo; Wang, Qiuming; Xiong, Zhigang; Wang, Dianlong; Zhao, X. S.

2013-12-01

23

Mesoporous carbon-coated LiFePO4 nanocrystals co-modified with graphene and Mg2+ doping as superior cathode materials for lithium ion batteries.  

PubMed

In this work, mesoporous carbon-coated LiFePO4 nanocrystals further co-modified with graphene and Mg(2+) doping (G/LFMP) were synthesized by a modified rheological phase method to improve the speed of lithium storage as well as cycling stability. The mesoporous structure of LiFePO4 nanocrystals was designed and realized by introducing the bead milling technique, which assisted in forming sucrose-pyrolytic carbon nanoparticles as the template for generating mesopores. For comparison purposes, samples modified only with graphene (G/LFP) or Mg(2+) doping (LFMP) as well as pure LiFePO4 (LFP) were also prepared and investigated. Microscopic observation and nitrogen sorption analysis have revealed the mesoporous morphologies of the as-prepared composites. X-ray diffraction (XRD) and Rietveld refinement data demonstrated that the Mg-doped LiFePO4 is a single olivine-type phase and well crystallized with shortened Fe-O and P-O bonds and a lengthened Li-O bond, resulting in an enhanced Li(+) diffusion velocity. Electrochemical properties have also been investigated after assembling coin cells with the as-prepared composites as the cathode active materials. Remarkably, the G/LFMP composite has exhibited the best electrochemical properties, including fast lithium storage performance and excellent cycle stability. That is because the modification of graphene provided active sites for nuclei, restricted the in situ crystallite growth, increased the electronic conductivity and reduced the interface reaction current density, while, Mg(2+) doping improved the intrinsically electronic and ionic transfer properties of LFP crystals. Moreover, in the G/LFMP composite, the graphene component plays the role of "cushion" as it could quickly realize capacity response, buffering the impact to LFMP under the conditions of high-rate charging or discharging, which results in a pre-eminent rate capability and cycling stability. PMID:24287590

Wang, Bo; Xu, Binghui; Liu, Tiefeng; Liu, Peng; Guo, Chenfeng; Wang, Shuo; Wang, Qiuming; Xiong, Zhigang; Wang, Dianlong; Zhao, X S

2014-01-21

24

Electrochemical performance of patterned LiFePO4 nano-electrode with a pristine amorphous layer  

NASA Astrophysics Data System (ADS)

A patterned LiFePO4 nanorod with a pristine amorphous LiFePO4 surface layer was fabricated by controlling the temperature gradient from the interior to the exterior layer in high-temperature annealing process through designing hierarchical multilayer electrode structure. The three dimensional patterned LiFePO4 nanorods were prepared using tobacco mosaic virus nanoforest arrays. The results indicate that the nano-electrodes nearly reached the theoretical capacity at a very low C rate even without conductive coatings. The amorphous LiFePO4 can fast transport the Li-ion to inside crystal LiFePO4, thus enhancing the rate capability.

Wang, Mao; Zhang, Wei; Liu, Yihang; Yang, Yong; Wang, Chunsheng; Wang, Yuan

2014-04-01

25

Battery management system with dual-balancing mechanism for LiFePO4 battery module  

Microsoft Academic Search

This paper presents a battery management system of LiFePO4 battery module with dual-balancing mechanism. First, the employed battery management can accurately capture some important parameters of the LiFePO4 battery module, including voltage, current, temperature, and providing protection functions for the battery module. Next, these obtained parameters of the battery are transmitted to the microcontroller through the inter-integrated circuit (I2C-bus). And

Chang-Hua Lin; Hsuan-Yi Chao; Chien-Ming Wang; Min-Hsuan Hung

2011-01-01

26

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

27

Enhanced electrochemical performances of LiFePO4/C by surface modification with Sn nanoparticles  

NASA Astrophysics Data System (ADS)

The surface of LiFePO4/C cathode material is coated with nano-sized Sn via a simple electroless deposition (ED) process, and the effects of the Sn-coating on the electrochemical performances of LiFePO4/C are investigated systematically by the charge/discharge testing, cyclic voltammograms and AC impedance spectroscopy, respectively. In comparison with the pristine LiFePO4/C, the Sn-coated LiFePO4/C exhibits higher capacity, better cyclability and higher rate capability in a wide operation temperature range. An analysis of the electrochemical measurements reveals that Sn-coated LiFePO4/C has good electric contact among particles, much lower charge-transfer resistances and higher lithium diffusion rate, especially at low temperature. In addition, the Sn-coating layer protects the active materials from chemical attack by HF and thus suppresses the dissolution of Fe from LiFePO4 in the LiPF6 based electrolyte.

Lin, Yingbin; Lin, Ying; Zhou, Ting; Zhao, Guiying; Huang, Yandan; Huang, Zhigao

2013-03-01

28

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

29

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

30

Hole polaron formation and migration in olivine phosphate materials  

NASA Astrophysics Data System (ADS)

By combining first-principles calculations and experimental x-ray photoemission (XPS) spectroscopy measurements, we investigate the electronic structure of potential Li-ion battery cathode materials LiMPO4 (M=Mn, Fe, Co, Ni) to uncover the underlying mechanisms that determine small hole polaron formation and migration. We show that small hole polaron formation depends on features in the electronic structure near the valence-band maximum and that, calculationally, these features depend on the methodology chosen for dealing with the correlated nature of the transition-metal d-derived states in these systems. Comparison with experiment reveals that a hybrid functional approach is superior to GGA+U in correctly reproducing the XPS spectra. Using this approach, we find that LiNiPO4 cannot support small hole polarons, but that the other three compounds can. The migration barrier is determined mainly by the strong- or weak-bonding nature of the states at the top of the valence band, resulting in a substantially higher barrier for LiMnPO4 than for LiCoPO4 or LiFePO4.

Johannes, M. D.; Hoang, Khang; Allen, J. L.; Gaskell, K.

2012-03-01

31

Kinetics of non-equilibrium lithium incorporation in LiFePO4.  

PubMed

Lithium-ion batteries are a key technology for multiple clean energy applications. Their energy and power density is largely determined by the cathode materials, which store Li by incorporation into their crystal structure. Most commercialized cathode materials, such as LiCoO(2) (ref. 1), LiMn(2)O(4) (ref. 2), Li(Ni,Co,Al)O(2) or Li(Ni,Co,Mn)O(2) (ref. 3), form solid solutions over a large concentration range, with occasional weak first-order transitions as a result of ordering of Li or electronic effects. An exception is LiFePO(4), which stores Li through a two-phase transformation between FePO(4) and LiFePO(4) (refs 5-8). Notwithstanding having to overcome extra kinetic barriers, such as nucleation of the second phase and growth through interface motion, the observed rate capability of LiFePO(4) has become remarkably high. In particular, once transport limitations at the electrode level are removed through carbon addition and particle size reduction, the innate rate capability of LiFePO(4) is revealed to be very high. We demonstrate that the reason LiFePO(4) functions as a cathode at reasonable rate is the availability of a single-phase transformation path at very low overpotential, allowing the system to bypass nucleation and growth of a second phase. The Li(x)FePO(4) system is an example where the kinetic transformation path between LiFePO(4) and FePO(4) is fundamentally different from the path deduced from its equilibrium phase diagram. PMID:21765400

Malik, Rahul; Zhou, Fei; Ceder, G

2011-08-01

32

Particle-size and morphology dependence of the preferred interface orientation in LiFePO4 nano-  

E-print Network

Particle-size and morphology dependence of the preferred interface orientation in LiFePO4 nano insights into the equilibrium properties and potential two-phase lithiation mechanisms in LiFePO4 nano, if experimentally-relevant nano-particles were to (de)lithiate under a thermodynamic two-phase mechanism

Ceder, Gerbrand

33

A Simplified Electrochemical and Thermal Aging Model of LiFePO4-Graphite Li-ion Batteries  

E-print Network

1 A Simplified Electrochemical and Thermal Aging Model of LiFePO4-Graphite Li-ion Batteries: Power of a commercial LiFePO4-graphite Li-ion battery. Compared to the isothermal reference, the mechanism of porosity;2 Due to their high power and energy densities, Li-ion technologies are the leading battery systems

34

Simplified Electrochemical and Thermal Model of LiFePO4-Graphite Li-Ion Batteries for Fast Charge Applications  

E-print Network

Simplified Electrochemical and Thermal Model of LiFePO4- Graphite Li-Ion Batteries for Fast Charge, a simplified electrochemical and thermal model of LiFePO4-graphite based Li-ion batteries is developed : 10.1149/2.064209jes #12;Over the past 15 years, Li-ion batteries have received much attention

Paris-Sud XI, Université de

35

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

36

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. PMID:24071818

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

2013-01-01

37

LiFePO4 - 3D carbon nanofiber composites as cathode materials for Li-ions batteries  

NASA Astrophysics Data System (ADS)

The characterization of carbon nanofiber 3D nonwovens, prepared by electrospinning process, coated with olivine structured lithium iron phosphate is reported. The LiFePO4 as cathode material for lithium ion batteries was prepared by a Pechini-assisted reversed polyol process. The coating has been successfully performed on carbon nanofiber 3D nonwovens by soaking in aqueous solution containing lithium, iron salts and phosphates at 70 °C for 2-4 h. After drying-out, the composites were annealed at 600 °C for 5 h under nitrogen. The surface investigation of the prepared composites showed a uniform coating of the carbon nonwoven nanofibers as well as the formation of cauliflower-like crystalline structures which are uniformly distributed all over the surface area of the carbon nanofibers. The electrochemical measurements on the composites showed good performances delivering a discharge specific capacity of 156 mAhg- 1 at a discharging rate of C/25 and 152 mAhg- 1 at a discharging rate of C/10 at room temperature.

Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Zhang, Y.; Yarin, A. L.

2012-03-01

38

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

39

Lithium extraction\\/insertion in LiFePO 4: an X-ray diffraction and Mössbauer spectroscopy study  

Microsoft Academic Search

The extraction and insertion of lithium in solid-state synthesized LiFePO4 has been followed by in situ X-ray diffraction and Mössbauer spectroscopy in ‘coffee-bag’ cells of type ?Li-metal | liq. el. | LiFePO4? during the first cycle. Two-phase Rietveld refinement of the X-ray diffractograms gives the triphylite (LiFePO4) to heterosite (FePO4) phase-ratios as charging and discharging of the cell proceeds. The

Anna S Andersson; Beata Kalska; Lennart Häggström; John O Thomas

2000-01-01

40

Optimized electrochemical performance of three-dimensional porous LiFePO4/C microspheres via microwave irradiation assisted synthesis  

NASA Astrophysics Data System (ADS)

Microwave irradiation assisted synthesis (MIAS) is successfully employed to prepare three-dimensional (3D) porous microspherical aggregation of LiFePO4/C nanoparticles as the cathode material of lithium ion battery. XRD, SEM, and TEM studies confirm that highly crystalline LiFePO4 without any impurity phase can be synthesized under microwave irradiation of 700 W for 5 min. The as-obtained LiFePO4/C sample is prepared via MIAS consisting of nanopores (20-30 nm) and nanoparticles (20-30 nm) which are coated with uniform, complete carbon layers (about ?3 nm). These superior physical characters provide LiFePO4/C (MIAS) excellent electrochemical performance at 0.1C including the high discharge capacity of 156.9 mAh g-1 and the low polarization of 51.5 mV. At the discharge rate of 1C, LiFePO4/C (MIAS) exhibits the low polarization of 202.3 mV, high capacity of 126.7 mAh g-1, high discharge voltage of 3.33 V, and specific energy of 398.5 kWh kg-1, all of which are much better than those measured for the sample prepared via conventional heat treatment (CHT). At even high rate of 5C, LiFePO4/C (CHT) fails to discharge whereas LiFePO4/C (MIAS) is able to deliver the discharge capacity of 95.5 mAh g-1. The low polarization of LiFePO4/C (MIAS) results in the good discharge voltage of 3.06 V, high specific energy of 278.8 Wh kg-1, and excellent energy efficiency of 72.0% at 5C.

Yu, Feng; Lim, San Hua; Zhen, Yongda; An, Yongxin; Lin, Jianyi

2014-12-01

41

Strain accommodation and potential hysteresis of LiFePO 4 cathodes during lithium ion insertion\\/extraction  

Microsoft Academic Search

Equilibrium potential hysteresis of electrode materials refers to the phenomenon that discharge equilibrium potential is lower than charge equilibrium potential. It is induced by the strain accommodation energy of phase transformation. Taking LiFePO4 as an example, the equilibrium potential hysteresis and accommodation energy of two LiFePO4 with different particle sizes were characterized using galvanostatic intermittent titration technique (GITT), cyclic voltammetry

Yujie Zhu; Chunsheng Wang

2011-01-01

42

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

2011-02-23

43

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

44

Characterization of LiFePO 4 as the cathode material for rechargeable lithium batteries  

Microsoft Academic Search

We investigated the electrochemical characteristics of LiFePO4 when used as the cathode material for rechargeable lithium batteries. We also studied the change in the crystal structure of the material during discharge. The material prepared at a relatively low temperature of 675°C showed a higher charge and discharge capacity than that prepared at higher temperatures. This was because material prepared at

Masaya Takahashi; Shinichi Tobishima; Koji Takei; Yoji Sakurai

2001-01-01

45

LiFePO 4 water-soluble binder electrode for Li-ion batteries  

Microsoft Academic Search

A new water-soluble elastomer from ZEON Corp. was evaluated as binder with LiFePO4 cathode material in Li-ion batteries. The mechanical characteristic of this cathode was compared to that with PVdF-based cathode binder. The elastomer-based cathode shows high flexibility with good adhesion. The electrochemical performance was also evaluated and compared to PVdF-based cathodes at 25 and at 60°C. A lower irreversible

A. Guerfi; M. Kaneko; M. Petitclerc; M. Mori; K. Zaghib

2007-01-01

46

Optimized Operating Range for Large-Format LiFePO4/Graphite Batteries  

SciTech Connect

e investigated the long-term cycling performance of large format 20Ah LiFePO4/graphite batteries when they are cycled in various state-of-charge (SOC) ranges. It is found that batteries cycled in the medium SOC range (ca. 20~80% SOC) exhibit superior cycling stability than batteries cycled at both ends (0-20% or 80-100%) of the SOC even though the capcity utilized in the medium SOC range is three times as large as those cycled at both ends of the SOC. Several non-destructive techniques, including a voltage interruption approach, model-based parameter identification, electrode impedance spectra analysis, ?Q/?V analysis, and entropy change test, were used to investigate the performance of LiFePO4/graphite batteries within different SOC ranges. The results reveal that batteries at the ends of SOC exhibit much higher polarization impedance than those at the medium SOC range. These results can be attributed to the significant structural change of cathode and anode materials as revealed by the large entropy change within these ranges. The direct correlation between the polarization impedance and the cycle life of the batteries provides an effective methodology for battery management systems to control and prolong the cycle life of LiFePO4/graphite and other batteries.

Jiang, Jiuchun; Shi, Wei; Zheng, Jianming; Zuo, Pengjian; Xiao, Jie; Chen, Xilin; Xu, Wu; Zhang, Jiguang

2014-06-01

47

A new insight into the LiFePO 4 delithiation process  

Microsoft Academic Search

Raman and Fourier transform infrared measurements for LixM0.03Fe0.97PO4, M=Cr, Cu, Al, Ti were performed. The spectra for delithiated samples to a low content of lithium extraction are practically the same as those of LiFePO4. For a high content of lithium extraction, the spectra repeat that of FePO4. In the case of the Li0.11FePO4 oxide the spectra cannot be reproduced just

V. Lemos; S. Guerini; J. Mendes Filho; S. M. Lala; L. A. Montoro; J. M. Rosolen

2006-01-01

48

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

49

LiFePO4\\/polymer\\/natural graphite: low cost Li-ion batteries  

Microsoft Academic Search

The aging and performance of natural graphite\\/PEO-based gel electrolyte\\/LiFePO4 cells are reported. The gel polymer electrolytes were produced by electron-beam irradiation and then soaked in a liquid electrolyte. The natural graphite anode in gel electrolyte containing LiBF4-EC\\/GBL exhibited high reversible capacity (345mAh\\/g) and high coulombic efficiency (91%). The LiFePO4 cathode in the same gel-polymer exhibited a reversible capacity of 160mAh\\/g

K. Zaghib; K. Striebel; A. Guerfi; J. Shim; M. Armand; M Gauthier

2004-01-01

50

First-principles study of the chemical bonding and conduction behavior of LiFePO4  

NASA Astrophysics Data System (ADS)

The electronic structure and chemical bonding of LiFePO4 were calculated using maximally-localized Wannier functions within the framework of the first-principles method. Comparison of the shifts in Wannier centers between LiFePO4 and delithiated reference (FePO4)r structures demonstrated the unstable chemical bonding of Fe-O1 and Fe-O2 during delithiation. The contribution of each orbital to the small-polaron polarization field was discussed in detail. The small polaron hopping is accompanied by a very small polarization field with the value of 0.049 C/m2. Results of our calculations showed that the chemical bonding of Fe-O3 has an important function in the low-temperature conductivity of LiFePO4.

Kou, Xiao-jing; Ke, Hua; Zhu, Chun-bo; Rolfe, Peter

2015-01-01

51

Origin of valence and core excitations in LiFePO(4) and FePO(4).  

PubMed

Electronic structures of LiFePO(4) and FePO(4) have been investigated using valence and core electron energy loss spectroscopy (EELS) supported by ab initio calculations. Valence electron energy loss spectra of FePO(4) are characterized by interband transitions found between 0 and 20 eV, which are not observed in LiFePO(4). Spectra are fully analysed using band structure calculations and calculated dielectric functions. In particular, we show that interband transitions observed in FePO(4) spectra originate from the states at the top of the valence band, which have mainly oxygen p character. From core-loss EELS, it is observed that the O-K edge in FePO(4) has a pre-edge peak below the threshold of the main O-K edge. This pre-edge peak is not observed in the O-K spectra of LiFePO(4). The position of the pre-edge peak is determined by a charge transfer process, which shifts the position of the iron 3d bands with respect to the conduction band. The intensity of the pre-edge peak is also determined by the changes in the hybridization of iron 3d and oxygen states as a result of extraction of lithium ions from the LiFePO(4) lattice. We show that the extraction of lithium ions from LiFePO(4) results in large changes in the electronic structure, such that FePO(4) can be considered to be a charge transfer insulator while LiFePO(4) is a typical Mott-Hubbard insulator. PMID:21399256

Kinyanjui, M K; Axmann, P; Wohlfahrt-Mehrens, M; Moreau, P; Boucher, F; Kaiser, U

2010-07-14

52

Synthesis and characterization of high power LiFePO4/C nano-plate thin films Nan Zhou a,b  

E-print Network

battery Solvothermal growth Nano-carbon coating a b s t r a c t Tunable LiFePO4/C thin films demonstrating, and were directly assembled into cells for testing. The LiFePO4/C nano-composite film cathode delivered.V. All rights reserved. 1. Introduction Thin film lithium ion batteries have been developed over recent

Cao, Guozhong

53

Carbon nanotube-loaded electrospun LiFePO4/carbon composite nanofibers as stable and binder-free cathodes for rechargeable lithium-ion batteries.  

PubMed

LiFePO(4)/CNT/C composite nanofibers were synthesized by using a combination of electrospinning and sol-gel techniques. Polyacrylonitrile (PAN) was used as the electrospinning media and carbon source. Functionalized CNTs were used to increase the conductivity of the composite. LiFePO(4) precursor materials, PAN and functionalized CNTs were dissolved or dispersed in N,N-dimethylformamide separately and they were mixed before electrospinning. LiFePO(4) precursor/CNT/PAN composite nanofibers were then heat-treated to obtain LiFePO(4)/CNT/C composite nanofibers. Fourier transform infrared spectroscopy measurements were done to demonstrate the functionalization of CNTs. The structure of LiFePO(4)/CNT/C composite nanofibers was determined by X-ray diffraction analysis. The surface morphology and microstructure of LiFePO(4)/CNT/C composite nanofibers were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of LiFePO(4)/CNT/C composite nanofibers was evaluated in coin-type cells. Functionalized CNTs were found to be well-dispersed in the carbonaceous matrix and increased the electrochemical performance of the composite nanofibers. As a result, cells using LiFePO(4)/CNT/C composite nanofibers have good performance, in terms of large capacity, extended cycle life, and good rate capability. PMID:22301674

Toprakci, Ozan; Toprakci, Hatice A K; Ji, Liwen; Xu, Guanjie; Lin, Zhan; Zhang, Xiangwu

2012-03-01

54

Surfactant based sol–gel approach to nanostructured LiFePO 4 for high rate Li-ion batteries  

Microsoft Academic Search

Porous nanostructured LiFePO4 powder with a narrow particle size distribution (100–300nm) for high rate lithium-ion battery cathode application was obtained using an ethanol based sol–gel route employing lauric acid as a surfactant. The synthesized LiFePO4 powders comprised of agglomerates of crystallites <65nm in diameter exhibiting a specific surface area ranging from 8m2g?1 to 36m2g?1 depending on the absence or presence

Daiwon Choi; Prashant N. Kumta

2007-01-01

55

LiFePO 4 safe Li-ion polymer batteries for clean environment  

NASA Astrophysics Data System (ADS)

The performance of natural graphite-fibers/PEO-based gel electrolyte/LiFePO 4 cells (7 mAh, 4 cm 2) is reported. The gel polymer electrolytes were produced by electron-beam irradiation and then soaked in a liquid electrolyte. The natural graphite-fiber composite anode in gel electrolyte containing 1.5 M LiFSI-EC/GBL (1:3) exhibited high reversible capacity (361 mAh g -1) and high Coulombic efficiency (92%). The LiFePO 4 cathode in the same gel polymer exhibited a reversible capacity of 161 mAh g -1 and 93% Coulombic efficiency. A 1.5 M solution of LiFSI in ethylene carbonate (EC)/?-butyrolactone (GBL) (1:3, v/v) mixed solvent is advantageous for use as the electrolyte in the laminated film bag because of its high flame point (135 °C), high boiling point (219 °C), low vapor pressure and high conductivity (10.2 mS cm -1 at 20 °C). The Li-ion gel polymer battery shows a very low capacity fade of 5% after 500 cycles and also has high-rate capability. The Li-ion gel polymer cell using LiFePO 4 cathodes is suitable for HEV applications.

Zaghib, K.; Charest, P.; Guerfi, A.; Shim, J.; Perrier, M.; Striebel, K.

56

Effect of carbon source on the morphology and electrochemical performances of LiFePO4/C nanocomposites.  

PubMed

The carbon coated LiFePO4 (LiFePO4/C) nanocomposites materials were successfully synthesized by sol-gel method. The microstructure and morphology of LiFePO4/C nanocomposites were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The results showed that the carbon layers decomposed by different dispersant and carbon source had different graphitization degree, and the sugar could decompose to form more graphite-like structure carbon. The carbon source and heat-treatment temperature had some effect on the particle size and morphology, the sample LFP-S700 synthesized by adding sugar as carbon source at 700 degrees C had smaller particle size, uniform size distribution and spherical shape. The electrochemical behavior of LiFePO4/C nanocomposites was analyzed using galvanostatic measurements and cyclic voltammetry (CV). The results showed that the sample LFP-S700 had higher discharge specific capacities, higher apparent lithium ion diffusion coefficient and lower charge transfer resistance. The excellent electrochemical performance of sample LFP-S700 could be attributed to its high graphitization degree of carbon, smaller particle size and uniform size distribution. PMID:24745239

Liu, Shuxin; Wang, Haibin; Yin, Hengbo; Wang, Hong; He, Jichuan

2014-03-01

57

Antisite defects and Mg doping in LiFePO4: a first-principles investigation  

NASA Astrophysics Data System (ADS)

Atomic and electronic structures of LiFePO4 with the antisite defect and Mg doping at Li and Fe sites have been investigated using first-principles density-functional theory with the on-site Coulomb interaction taken into account. It is demonstrated that the most favorable antisite defect type is the exchange defect, in which Li and Fe ions exchange positions. The resultant longer Fe-O bond and narrower band gap drop a hint that the electronic and ionic transport properties may be improved. For the case of Mg doping, Mg is preferentially doped at the Fe site instead of the Li site to form a new LiFe1- y Mg y PO4 solid solution, leading to a higher ionic conductivity. Moreover, the dependence of the electrochemical properties on the concentration of Mg dopant has also been discussed.

Zhang, Hua; Tang, Yuanhao; Shen, Jingqin; Xin, Xiaogui; Cui, Lixia; Chen, Lijiang; Ouyang, Chuying; Shi, Siqi; Chen, Liquan

2011-08-01

58

Simple and fast synthesis of LiFePO 4-C composite for lithium rechargeable batteries by ball-milling and microwave heating  

Microsoft Academic Search

A very simple and rapid method for synthesizing LiFePO4-C composite has been developed by vibrant type ball-milling for 30min and microwave heating for 2–4min. X-ray diffraction and Mössbauer spectroscopy verify that well-crystallized LiFePO4 without Fe3+ impurities is obtained. From laser particle size analysis and transmission electron microscopy, it is confirmed that a LiFePO4-C composite with fine and uniform particle size

Min-Sang Song; Yong-Mook Kang; Jin-Ho Kim; Hyun-Seok Kim; Dong-Yung Kim; Hyuk-Sang Kwon; Jai-Young Lee

2007-01-01

59

Crystal Structure, Physical Properties, and Electrochemistry of Copper Substituted LiFePO4 Single Crystals  

E-print Network

indicate that the dark brown color originates from interionic d-d transitions. A part of the lithium ions phosphate, with the olivine structure, has been synthesized hydrothermally as dark-brown single crystals

Ceder, Gerbrand

60

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

61

Monodisperse porous LiFePO4/C microspheres derived by microwave-assisted hydrothermal process combined with carbothermal reduction for high power lithium-ion batteries  

NASA Astrophysics Data System (ADS)

A microwave-assisted hydrothermal approach combined with carbothermal reduction has been developed to synthesize monodisperse porous LiFePO4/C microspheres, which possess the diameter range of 1.0-1.5 ?m, high tap density of ?1.3 g cm-3, and mesoporous characteristic with Brunauer-Emmett-Teller (BET) surface area of 30.6 m2 g-1. The obtained microspheres show meatball-like morphology aggregated by the carbon-coated LiFePO4 nanoparticles. The electrochemical impedance spectra (EIS) results indicate that carbon coating can effectively enhance both of the electronic and ionic conductivities for LiFePO4/C microspheres. The Li-ion diffusion coefficient of the LiFePO4/C microspheres calculated from the cyclic voltammetry (CV) curves is ?6.25 × 10-9 cm2 s-1. The electrochemical performance can achieve about 100 and 90 mAh g-1 at 5C and 10C charge/discharge rates, respectively. As cathode material, the as-prepared LiFePO4/C microspheres show excellent rate capability and cycle stability, promising for high power lithium-ion batteries.

Chen, Rongrong; Wu, Yixiong; Kong, Xiang Yang

2014-07-01

62

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. PMID:22221711

2012-01-01

63

Etched Colloidal LiFePO4 Nanoplatelets toward High-Rate Capable Li-Ion Battery Electrodes  

PubMed Central

LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently “plagued” by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of ?155 mAh/g, ?135 mAh/g, and ?125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of ?70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was ?30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries. PMID:25372361

2014-01-01

64

Etched colloidal LiFePO4 nanoplatelets toward high-rate capable Li-ion battery electrodes.  

PubMed

LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently "plagued" by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of ? 155 mAh/g, ? 135 mAh/g, and ? 125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of ? 70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was ? 30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries. PMID:25372361

Paolella, Andrea; Bertoni, Giovanni; Marras, Sergio; Dilena, Enrico; Colombo, Massimo; Prato, Mirko; Riedinger, Andreas; Povia, Mauro; Ansaldo, Alberto; Zaghib, Karim; Manna, Liberato; George, Chandramohan

2014-12-10

65

Reversible chemical delithiation/lithiation of LiFePO4: towards a redox flow lithium-ion battery.  

PubMed

Reversible chemical delithiation/lithiation of LiFePO(4) was successfully demonstrated using ferrocene derivatives, based on which a novel energy storage system--the redox flow lithium-ion battery (RFLB), was devised by integrating the operation flexibility of a redox flow battery and high energy density of a lithium-ion battery. Distinct from the recent semi-solid lithium rechargeable flow battery, the energy storage materials of RFLB stored in separate energy tanks remain stationary upon operation, giving us a fresh perspective on building large-scale energy storage systems with higher energy density and improved safety. PMID:23262995

Huang, Qizhao; Li, Hong; Grätzel, Michael; Wang, Qing

2013-02-14

66

Li-Ion Battery with LiFePO4 Cathode and Li4Ti5O12 Anode for Stationary Energy Storage  

SciTech Connect

i-ion batteries based on commercially available LiFePO4 cathode and Li4Ti5O12 anode were investigated for potential stationary energy storage applications. The full cell that operated at flat 1.85V demonstrated stable cycling for 200 cycles followed by a rapid fade. A significant improvement in cycling stability was achieved via Ketjen black coating of the cathode. A Li-ion full cell with Ketjen black modified LiFePO4 cathode and an unmodified Li4Ti5O12 anode exhibited negligible fade after more than 1200 cycles with a capacity of ~130mAh/g. The improved stability, along with its cost-effectiveness, environmentally benignity and safety, make the LiFePO4/ Li4Ti5O12 Li-ion battery a promising option of storing renewable energy.

Wang, Wei; Choi, Daiwon; Yang, Zhenguo

2013-01-01

67

In Situ Catalytic Synthesis of High-Graphitized Carbon-Coated LiFePO4 Nanoplates for Superior Li-Ion Battery Cathodes.  

PubMed

The low electronic conductivity and one-dimensional diffusion channel along the b axis for Li ions are two major obstacles to achieving high power density of LiFePO4 material. Coating carbon with excellent conductivity on the tailored LiFePO4 nanoparticles therefore plays an important role for efficient charge and mass transport within this material. We report here the in situ catalytic synthesis of high-graphitized carbon-coated LiFePO4 nanoplates with highly oriented (010) facets by introducing ferrocene as a catalyst during thermal treatment. The as-obtained material exhibits superior performances for Li-ion batteries at high rate (100 C) and low temperature (-20 °C), mainly because of fast electron transport through the graphitic carbon layer and efficient Li(+)-ion diffusion through the thin nanoplates. PMID:25584530

Ma, Zhipeng; Fan, Yuqian; Shao, Guangjie; Wang, Guiling; Song, Jianjun; Liu, Tingting

2015-02-01

68

Polaron formation and transport in olivine cathode materials  

NASA Astrophysics Data System (ADS)

One of the critical factors limiting Li ion battery performance is electronic conduction through the cathode material. In the olivine structure type materials, such as LiFePO4, the parent materials are insulators with a gap of approximately 4 (or more) eV. The withdrawal of an electron results not in a band-type hole state, but rather a localized polaronic state. Transport then occurs via hopping of the polaron through the crystal. The measured electronic conduction in olivine materials depends on the transition metal cation type. In this study, we use density functional theory to compare formation of polarons in olivine materials with different transition metal cations: Mn, Fe, Co, and Ni. We show that the underlying electronic structure of the fully lithiated material (or fully delithiated material) essentially determines whether or not polaron formation is possible in localized d-states or whether the holes that result from adding or removing an electron reside in oxygen-derived states. We also investigate the facility of polaronic hopping by calculating the barrier between adjacent polaron sites in each of the four materials.

Johannes, Michelle; Hoang, Khang

2011-03-01

69

Impact of carbon structure and morphology on the electrochemical performance of LiFePO4/C composites  

SciTech Connect

The electrochemical performance of LiFePO4/C composites in lithium cells is closely correlated to pressed pellet conductivities measured by AC impedance methods. These composite conductivities are a strong function not only of the amount of carbon but of its structure and distribution. Ideally, the amount of carbon in composites should be minimal (less than about 2 wtpercent) so as not to decrease the energy density unduly. This is particularly important for plug-in hybrid electric vehicle applications (PHEVs) where both high power and moderate energy density are required. Optimization of the carbon structure, particularly the sp2/sp3 and disordered/graphene (D/G) ratios, improves the electronic conductivity while minimizing the carbon amount. Manipulation of the carbon structure can be achieved via the use of synthetic additives including ironcontaining graphitization catalysts. Additionally, combustion synthesis techniques allow co-synthesis of LiFePO4 and carbon fibers or nanotubes, which can act as"nanowires" for the conduction of current during cell operation.

Doeff, Marca M.; Doeff, Marca M.; Wilcox, James D.; Yu, Rong; Aumentado, Albert; Marcinek, Marek; Kostecki, Robert

2007-09-19

70

Enhanced electrochemical properties of LiFePO4 by Mo-substitution and graphitic carbon-coating via a facile and fast microwave-assisted solid-state reaction.  

PubMed

A composite cathode material for lithium ion battery applications, Mo-doped LiFePO(4)/C, is obtained through a facile and fast microwave-assisted synthesis method. Rietveld analysis of LiFePO(4)-based structural models using synchrotron X-ray diffraction data shows that Mo-ions substitute onto the Fe sites and displace Fe-ions to the Li sites. Supervalent Mo(6+) doping can act to introduce Li ion vacancies due to the charge compensation effect and therefore facilitate lithium ion diffusion during charging/discharging. Transmission electron microscope images demonstrate that the pure and doped LiFePO(4) nanoparticles were uniformly covered by an approximately 5 nm thin layer of graphitic carbon. Amorphous carbon on the graphitic carbon-coated pure and doped LiFePO(4) particles forms a three-dimensional (3D) conductive carbon network, effectively improving the conductivity of these materials. The combined effects of Mo-doping and the 3D carbon network dramatically enhance the electrochemical performance of these LiFePO(4) cathodes. In particular, Mo-doped LiFePO(4)/C delivers a reversible capacity of 162 mA h g(-1) at a current of 0.5 C and shows enhanced capacity retention compared to that of undoped LiFePO(4)/C. Moreover, the electrode exhibits excellent rate capability, with an associated high discharge capacity and good electrochemical reversibility. PMID:22311165

Li, Dan; Huang, Yudai; Sharma, Neeraj; Chen, Zhixin; Jia, Dianzeng; Guo, Zaiping

2012-03-14

71

Vacancy-driven anisotropic defect distribution in the battery-cathode material LiFePO4.  

PubMed

Li-ion mobility in LiFePO(4), a key property for energy applications, is impeded by Fe antisite defects (Fe(Li)) 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 (V(Li)) are confined in one-dimensional b-axis channels, shuttling between neighboring Fe(Li). Segregation in select channels results in shorter Fe(Li)-Fe(Li) spans, whereby the energy is lowered by the V(Li)'s spending more time bound to end-point Fe(Li)'s. V(Li)-Fe(Li)-V(Li) complexes also form, accounting for observed electron energy loss spectroscopy features. PMID:21929178

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

2011-08-19

72

Simplified electrochemical multi-particle model for LiFePO4 cathodes in lithium-ion batteries  

NASA Astrophysics Data System (ADS)

A simplified physics-based model is developed to predict the performance of an LiFePO4 cathode at various operating and design conditions. Newman's full-order porous-electrode model is simplified using polynomial approximations for electrolyte variables at the electrode-level while a multi-particle model featuring variable solid-state diffusivity is employed at the particle level. The computational time of this reduced-order model is decreased by almost one order of magnitude compared to the full-order model without sacrificing the accuracy of the results. The model is general and can be used to expedite the simulation of any composite electrode with active-material particles of non-uniform properties (e.g., size, contact resistance, material chemistry etc.). In a broader perspective, this model is of practical value for electric vehicle power train simulations and battery management systems.

Mastali Majdabadi, Mehrdad; Farhad, Siamak; Farkhondeh, Mohammad; Fraser, Roydon A.; Fowler, Michael

2015-02-01

73

Structural study of LiFePO4-LiNiPO4 solid solutions  

NASA Astrophysics Data System (ADS)

Modifications of the local structure and lattice parameters in LiFe1-x NixPO4 (0 < x < 0.15,0.9,1.0) olivine-type solid solutions have been studied by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Samples have been synthesized and characterized in our laboratory, and a preliminary electrochemical characterization shows that Ni doping increases slightly the performances in Li-ion cells at low Ni concentrations x. Results of both XRD and XAS techniques are consistent and indicate ordering of Li in the M1 site, and of Fe and Ni in the M2 site of the olivine structure. Ni doping is found to induce an anisotropic shrinking of the unit cell with both Fe and Ni six-coordinated with oxygens, occupying distorted octahedral sites. The local structure measured by XAS shows that average Fe-O and Ni-O distances do not change appreciably with Ni doping indicating that the reduction of cell size is mainly associated with the presence of shorter Ni-O distances at M2 sites. Possible connections among the presence of a distribution of distorted octahedra of different size in the structure and different electrochemical performances of the material as a function of doping are briefly discussed.

Tabassam, Lubna; Giuli, Gabriele; Moretti, Arianna; Nobili, Francesco; Marassi, Roberto; Minicucci, Marco; Gunnella, Roberto; Olivi, Luca; Di Cicco, Andrea

2012-09-01

74

Olivines and olivine coronas in mesosiderites  

NASA Technical Reports Server (NTRS)

The paper presents a study of olivines and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. Olivine composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; olivine occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified olivine orthopyroxenites. Fine-grained coronas surround olivine, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.

Nehru, C. E.; Zucker, S. M.; Harlow, G. E.; Prinz, M.

1980-01-01

75

Synthesis, characterization and modification of LiFePO4 by doping with platinum and palladium for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

Lithium iron phosphate (LiFePO4) with features of excellent thermal stability, non-toxicity, low cost and abundance in nature is one of the most promising cathode materials to be used in lithium ion batteries. However, as it suffers from the low electrical conductivity and poor ionic diffusion, it operates only at low charge/discharge current rates. In this thesis, a dual approach of metal doping and carbon coating was employed to solve the aforementioned problem. This work is mainly on the study, for the first time, of the effect of platinum and palladium doping of LiFePO 4 on its physical-chemical properties. The effect of Pt and Pd doping on the LiFePO4 performance as Li-ion cathode will be also shown. Sol-gel and hydrothermal methods were used to synthesize the LiFePO4 and doped-LiFePO4 cathode materials. The prepared materials were characterized using different methods such as XRD (X-ray Diffraction), XPS (X-ray Photoelectron Spectroscopy), SEM (Scanning Electron Microscopy) and BET (Brunauer Emmett Teller). The electrochemical characterization techniques including charge/discharge test, CV (Cyclic Voltammetry), EIS (Electrochemical Impedance Spectroscopy) and cycling were also used. The effects of metals doping on chemical-physical properties, particles sizes, morphology, structure and purity of the electrodes were investigated and their correlation to the electrochemical properties of materials were studied. In the first section, we determine the optimized amount of carbon support and morphology of the particles using SEM which help to obtain LiFePO 4/C cathode material with an excellent electrochemical performance. It was found that when the amount of coated carbon exceeds the optimized value, the discharge capacity of the LiFePO4/C material decreased. This might indicate a low diffusion of the Li+ ions through the carbon layers during the charge/discharge process. On the other hand, for LiFePO4 coated with carbon quantity lower than the optimum value, LiFePO4/C cathode exhibited poor capacity performance due to its low electrical conductivity. Therefore, both the quality and quantity of carbon coating on the surface of LiFePO4 particles are important and only optimized carbon content can lead to a more uniform carbon distribution. Optimized surface area and conductivity, which give high electrochemical performance, can be only achieved if the appropriate carbon content and method of electrode preparation are obtained. In the second part, the effect of doping the LiFePO4/C electrodes with Pt and Pd on the structure, their chemical compositions and electrochemical properties were investigated. The electrodes were prepared using sol-gel method. The chemical composition analysis by XPS of the Pd doped electrodes showed that Pd was detected in the Pd-doped nano composite materials. Also, for Pt doped electrode, Pt was detected in Pt-doped based nano composite materials. Based on the structure and morphology of the non doped and doped electrodes, the results showed that palladium doping facilitated formation of Li 3PO4 impurity in the LiFe0.98Pd0.02PO 4/C and LiFe0.96Pd0.04PO4/C electrodes. Consequently the presence of the Pd in the doped sample reduced the lattice parameters, increased the size of particles and caused their agglomeration. The electrochemical performances of the electrodes showed that their specific capacity decreased when the palladium content increases. Then, the Pd-doped electrodes fabricated using sol-gel method exhibit less discharge capacity than samples of the non-doped LiFePO4/C electrode. The reduction in the level of performance is attributed to several reasons such as the shrinking of the lattice parameters, the formation of Li3PO4 impurity phase, and large particles size. In contrast, for LiFePO4/C doped with Pt using sol-gel method, it was found that the crystallinity and the lattice parameters of LiFe 0.96Pt0.04PO4/C nanocomposite material increased when compared with LiFePO4/C electrode. No impurity was formed in the Pt-doped electrode. In addition, the Pt doped samples exhibited smalle

Talebi-Esfandarani, Majid

76

Particle shapes and surface structures of olivine NaFePO? in comparison to LiFePO?.  

PubMed

The expansion of batteries into electric vehicle and grid storage applications has driven the development of new battery materials and chemistries, such as olivine phosphate cathodes and sodium-ion batteries. Here we present atomistic simulations of the surfaces of olivine-structured NaFePO4 as a sodium-ion battery cathode, and discuss differences in its morphology compared to the lithium analogue LiFePO4. The calculated equilibrium morphology is mostly isometric in appearance, with (010), (201) and (011) faces dominant. Exposure of the (010) surface is vital because it is normal to the one-dimensional ion-conduction pathway. Platelet and cube-like shapes observed by previous microscopy studies are reproduced by adjusting surface energies. The results indicate that a variety of (nano)particle morphologies can be achieved by tuning surface stabilities, which depend on synthesis methods and solvent conditions, and will be important in optimising electrochemical performance. PMID:25200320

Whiteside, Alexander; Fisher, Craig A J; Parker, Stephen C; Islam, M Saiful

2014-10-21

77

Architectures of tavorite LiFe(PO4)(OH)0.5F0.5 hierarchical microspheres and their lithium storage properties  

NASA Astrophysics Data System (ADS)

Tavorite LiFe(PO4)(OH)0.5F0.5 microspheres with different morphologies were prepared by a facile solvothermal route, and were further investigated as cathode materials for Li-ion batteries. We highly expect that this research can provide a useful fundamental understanding of the shape-dependent electrochemical performance of tavorite electrode materials.Tavorite LiFe(PO4)(OH)0.5F0.5 microspheres with different morphologies were prepared by a facile solvothermal route, and were further investigated as cathode materials for Li-ion batteries. We highly expect that this research can provide a useful fundamental understanding of the shape-dependent electrochemical performance of tavorite electrode materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01754d

Zhou, Gang; Duan, Xiaochuan; Liu, Bin; Li, Qiuhong; Wang, Taihong

2014-09-01

78

First-principles investigation of the electronic and Li-ion diffusion properties of LiFePO4 by sulfur surface modification  

NASA Astrophysics Data System (ADS)

We present a first-principles calculation for the electronic and Li-ion diffusion properties of the LiFePO4 (010) surface modified by sulfur. The calculated formation energy indicates that the sulfur adsorption on the (010) surface of the LiFePO4 is energetically favored. Sulfur is found to form Fe-S bond with iron. A much narrower band gap (0.67 eV) of the sulfur surface-modified LiFePO4 [S-LiFePO4 (010)] is obtained, indicating the better electronic conductive properties. By the nudged elastic band method, our calculations show that the activation energy of Li ions diffusion along the one-dimensional channel on the surface can be effectively reduced by sulfur surface modification. In addition, the surface diffusion coefficient of S-LiFePO4 (010) is estimated to be about 10-11 (cm2/s) at room temperature, which implies that sulfur modification will give rise to a higher Li ion carrier mobility and enhanced electrochemical performance.

Xu, Guigui; Zhong, Kehua; Zhang, Jian-Min; Huang, Zhigao

2014-08-01

79

Core-Shell LiFePO4 /Carbon-Coated Reduced Graphene Oxide Hybrids for High-Power Lithium-Ion Battery Cathodes.  

PubMed

Core-shell carbon-coated LiFePO4 nanoparticles were hybridized with reduced graphene (rGO) for high-power lithium-ion battery cathodes. Spontaneous aggregation of hydrophobic graphene in aqueous solutions during the formation of composite materials was precluded by employing hydrophilic graphene oxide (GO) as starting templates. The fabrication of true nanoscale carbon-coated LiFePO4 -rGO (LFP/C-rGO) hybrids were ascribed to three factors: 1)?In-situ polymerization of polypyrrole for constrained nanoparticle synthesis of LiFePO4 , 2)?enhanced dispersion of conducting 2D networks endowed by colloidal stability of GO, and 3)?intimate contact between active materials and rGO. The importance of conducting template dispersion was demonstrated by contrasting LFP/C-rGO hybrids with LFP/C-rGO composites in which agglomerated rGO solution was used as the starting templates. The fabricated hybrid cathodes showed superior rate capability and cyclability with rates from 0.1 to 60?C. This study demonstrated the synergistic combination of nanosizing with efficient conducting templates to afford facile Li(+) ion and electron transport for high power applications. PMID:25430976

Ha, Sung Hoon; Lee, Yun Jung

2015-01-26

80

Thermal characteristics of a FeF3 cathode via conversion reaction in comparison with LiFePO4  

NASA Astrophysics Data System (ADS)

The thermal stability of a FeF3 cathode via a conversion reaction was quantitatively studied using differential scanning calorimetry (DSC). Mixtures of charged and discharged FeF3 electrodes and electrolyte were measured by changing the ratio of electrode to electrolyte. A mild exothermic peak was observed at temperatures ranging from 210 to 380 °C for the mixtures of charged electrode and electrolyte even if the electrode/electrolyte ratio was changed. Moreover, the cycling depth had no effect on the thermal stability of the charged electrode in the electrolyte. For the mixtures of discharged electrode and electrolyte, exothermic reactions occurred in the range of 250-350 °C, which varied with the electrode/electrolyte ratio. Although the exothermic reactions of the mixtures varied with the electrode/electrolyte ratio, the thermal risk for both charged and discharged electrodes coexisted with the electrolyte appeared to be mainly due to electrolyte decomposition. By comparing the heat values of mixtures of the charged and discharged electrodes and electrolyte, the FeF3 electrodes in the electrolyte demonstrated better thermal stability than LiFePO4 electrodes at elevated temperatures.

Zhou, Mingjiong; Zhao, Liwei; Okada, Shigeto; Yamaki, Jun-ichi

2011-10-01

81

LiFePO4 microcrystals as an efficient heterogeneous Fenton-like catalyst in degradation of rhodamine 6G  

PubMed Central

We present a novel heterogeneous Fenton-like catalyst of LiFePO4 (LFP). LFP has been widely used as an electrode material of a lithium ion battery, but we observed that commercial LFP (LFP-C) could act as a good Fenton-like catalyst to decompose rhodamine 6G. The catalytic activity of LFP-C microparticles was much higher than a popular catalyst, magnetite nanoparticles. Furthermore, we found that the catalytic activity of LFP-C could be further increased by increasing the specific surface area. The reaction rate constant of the hydrothermally synthesized LFP microcrystals (LFP-H) is at least 18 times higher than that of magnetite nanoparticles even though the particle size of LFP is far larger than magnetite nanoparticles. The LFP catalysts also exhibited a good recycling behavior and high stability under an oxidizing environment. The effects of the experimental parameters such as the concentration of the catalysts, pH, and the concentration of hydrogen peroxide on the catalytic activity of LFP were also analyzed. PMID:24948896

2014-01-01

82

Tungsten diffusion in olivine  

NASA Astrophysics Data System (ADS)

Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

Cherniak, D. J.; Van Orman, J. A.

2014-03-01

83

A novel sol-gel method based on FePO4·2H2O to synthesize submicrometer structured LiFePO4/C cathode material  

NASA Astrophysics Data System (ADS)

Carbon coated LiFePO4/C cathode material is synthesized with a novel sol-gel method, using cheap FePO4·2H2O as both iron and phosphorus sources and oxalic acid (H2C2O4·2H2O) as both complexant and reductant. In H2C2O4 solution, FePO4·2H2O is very simple to form transparent sols without controlling the pH value. Pure submicrometer structured LiFePO4 crystal is obtained with a particle size ranging from 100 to 500 nm, which is also uniformly coated with a carbon layer, about 2.6 nm in thickness. The as-synthesized LiFePO4/C sample exhibits high initial discharge capacity 160.5 mAh g-1 at 0.1 C rate, with a capacity retention of 98.7% after 50th cycle. The material also shows good high-rate discharge performances, about 106 mAh g-1 at 10 C rate. The improved electrochemical properties of as-synthesized LiFePO4/C are ascribed to its submicrometer scale particles and low electrochemical impedance. The sol-gel method may be of great interest in the practical application of LiFePO4/C cathode material.

Peng, Wenxiu; Jiao, Lifang; Gao, Haiyan; Qi, Zhan; Wang, Qinghong; Du, Hongmei; Si, Yuchang; Wang, Yijing; Yuan, Huatang

2011-03-01

84

Influence of pH Value on the Properties of NH4Fe2(OH)- (PO4)2·2H2O Precursor and LiFePO4/C Composite  

NASA Astrophysics Data System (ADS)

With the aim of investigating the influence of pH value on the properties of NH4Fe2(OH)(PO4)2·2H2O precursor and LiFePO4/C composite, we prepared a series of (NH4)Fe2(OH)(PO4)2·2H2O by adjusting the pH value in the chemical precipitation process. In addition, the LiFePO4/C composite was fabricated by using (NH4)Fe2(OH)(PO4)2·2H2O as precursor. The images of scanning electron microscopy demonstrate that the precursor particle size increases as the pH value increases, which facilitates the tuning of the properties of the LiFePO4/C composite. A further investigation indicates that an increase of viscosity of the precipitate slurry in the chemical precipitation process is responsible for the change of precursor particle size. In addition, the electrochemical performance of the LiFePO4/C composite is also governed by pH value. LiFePO4/C composite prepared at the pH value of 4.0 delivers a discharge capacity of 91 mAh g-1 and 114 mAh cm-3 at 10 C, showing a capacity retention of 99.48% after 100 cycles, which confirms the excellent rate capability and cycling stability.

Liu, Xue-Bao; Liu, Guo-Biao; Wang, Yan; Chen, Chen; Li, Jian-Long; Liu, Heng

2015-01-01

85

Titanium diffusion in olivine  

NASA Astrophysics Data System (ADS)

Diffusion of Ti has been characterized in natural olivine and synthetic forsterite. Experiments on the natural olivines were run under buffered conditions (IW and NNO), and those on synthetic forsterite were run in air. Titanium diffusion appears relatively insensitive to crystallographic orientation and oxygen fugacity under the range of investigated conditions, and diffusivities are similar for Fe-bearing olivine and forsterite. For Ti diffusion in synthetic forsterite, we obtain the following Arrhenius relation for diffusion over the temperature range 900-1400 °C:

Cherniak, Daniele J.; Liang, Yan

2014-12-01

86

Morphological investigation of sub-micron FePO 4 and LiFePO 4 particles for rechargeable lithium batteries  

Microsoft Academic Search

Microstructural variations of amorphous FePO4 and LiFePO4 (the latter obtained by chemical lithiation of the former) as a result of the annealing temperature have been studied by Thermogravimetric Analysis (TGA)\\/Differential Thermal Analysis (DTA), chemical analysis, Brunauer–Emmet–Taylor (BET) and Scanning Electron Microscopy (SEM) techniques. Round-shaped amorphous FePO4 particles 40–80nm in size are obtained after heating (at 400°C) amorphous FePO4·2H2O in air

Silvera Scaccia; Maria Carewska; Pawel Wisniewski; Pier Paolo Prosini

2003-01-01

87

Electrochemical performances for preferred oriented PLD thin-film electrodes of LiNi 0.8Co 0.2O 2, LiFePO 4 and LiMn 2O 4  

Microsoft Academic Search

The charge–discharge performances for lithium ion batteries using the PLD thin-film cathodes of LiNi0.8Co0.2O2, LiFePO4 and LiMn2O4 were investigated. LiMn2O4 and LiFePO4, which have a 3-D frame work crystal structure, showed smooth charging and discharging. On the contrary, LiNi0.8Co0.2O2, which consists of a 2-D layered crystal structure, exhibited a poor discharge capacity. The differences in electro-chemical behaviors might be related

Tadaaki Matsumura; Nobuyuki Imanishi; Atsushi Hirano; Noriyuki Sonoyama; Yasuo Takeda

2008-01-01

88

Direct Observation of Active Material Concentration Gradients and Crystallinity Breakdown in LiFePO4 Electrodes During Charge/Discharge Cycling of Lithium Batteries  

PubMed Central

The phase changes that occur during discharge of an electrode comprised of LiFePO4, carbon, and PTFE binder have been studied in lithium half cells by using X-ray diffraction measurements in reflection geometry. Differences in the state of charge between the front and the back of LiFePO4 electrodes have been visualized. By modifying the X-ray incident angle the depth of penetration of the X-ray beam into the electrode was altered, allowing for the examination of any concentration gradients that were present within the electrode. At high rates of discharge the electrode side facing the current collector underwent limited lithium insertion while the electrode as a whole underwent greater than 50% of discharge. This behavior is consistent with depletion at high rate of the lithium content of the electrolyte contained in the electrode pores. Increases in the diffraction peak widths indicated a breakdown of crystallinity within the active material during cycling even during the relatively short duration of these experiments, which can also be linked to cycling at high rate. PMID:24790684

2014-01-01

89

Phase evolution in single-crystalline LiFePO4 followed by in situ scanning X-ray microscopy of a micrometre-sized battery.  

PubMed

LiFePO4 is one of the most frequently studied positive electrode materials for lithium-ion batteries during the last years. Nevertheless, there is still an extensive debate on the mechanism of phase transformation. On the one hand this is due to the small energetic differences involved and hence the great sensitivity with respect to parameters such as size and morphology. On the other hand this is due to the lack of in situ observations with appreciable space and time resolution. Here we present scanning transmission X-ray microscopy measurements following in situ the phase boundary propagation within a LiFePO4 single crystal along the (010) orientation during electrochemical lithiation/delithiation. We follow, on a battery-relevant timescale, the evolution of a two-phase-front on a micrometre scale with a lateral resolution of 30?nm and with minutes of time resolution. The growth pattern is found to be dominated by elastic effects rather than being transport-controlled. PMID:25599854

Ohmer, Nils; Fenk, Bernhard; Samuelis, Dominik; Chen, Chia-Chin; Maier, Joachim; Weigand, Markus; Goering, Eberhard; Schütz, Gisela

2015-01-01

90

Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance.  

PubMed

In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4 nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm(-2) at 0.1 mA cm(-2) (lowest rate) and 1.1 mA h cm(-2) at 6 mA cm(-2) (highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium. PMID:24954747

Asfaw, Habtom D; Roberts, Matthew R; Tai, Cheuk-Wai; Younesi, Reza; Valvo, Mario; Nyholm, Leif; Edström, Kristina

2014-08-01

91

Artificial meteor ablation studies: Olivine  

NASA Technical Reports Server (NTRS)

Artificial meteor ablation was performed on a Mg-rich olivine sample using an arc-heated plasma of ionized air. Experimental conditions simulated a meteor traveling about 12 km/sec at an altitude of 70 km. The mineral content of the original olivine sample was 98% olivine (including traces of olivine alteration products) and 2% chromite. Forsterite content of the original olivine was Fo-89. After ablation, the forsterite content had increased to Fo-94 in the recrystallized olivine. In addition, lamella-like intergrowths of magnetite were prevalent constituents. Wherever magnetite occurred, there was an increase in Mg and a corresponding decrease in Fe for the recrystallized olivine. The Allende fusion crust consisted of a recrystallized olivine, which was more Mg-rich and Fe-deficient than the original meteorite's olivine, and abundant magnetite grains. Although troilite and pentlandite were the common opaque mineral constituents in this meteorite, magnetite was the principal opaque mineral found in the fusion crust.

Blanchard, M. B.; Cunningham, G. G.

1973-01-01

92

C-containing LiFePO 4 materials — Part I: Mechano-chemical synthesis and structural characterization  

Microsoft Academic Search

C–LiFePO4 composites were synthesized by mechano-chemical activation using iron and lithium phosphates, and also cellulose as carbon precursor; this mixture was treated with 2 thermal treatments (“slow” or “fast” treatment) and 2 temperatures (575 °C or 800 °C). The four synthesized samples were pure olivine-type materials (XRD), but chemical analyses and Mössbauer spectroscopy show Li\\/Fe and P\\/Fe ratios larger than 1 and

M. Maccario; L. Croguennec; A. Wattiaux; E. Suard; F. Le Cras; C. Delmas

2008-01-01

93

Surface-orientation-dependent distribution of subsurface cation-exchange defects in olivine-phosphate nanocrystals.  

PubMed

Atomic-scale exchange between two different cations of similar size in crystalline oxides is one of the major types of point defects when multiple cations in oxygen interstitials are arrayed in an ordered manner. Although a number of studies have been performed on a variety of Li-intercalation olivine phosphates to determine the distribution of exchange defects in bulk, understanding of the thermodynamic stability of the defects in subsurface regions and its dependency on the crystallographic orientation at the surface has remained elusive. Through a combination of small-angle neutron scattering, atomic-scale direct probing with scanning transmission electron microscopy, and theoretical ab initio calculations, we directly demonstrate that the antisite exchange defects are distributed in a highly anisotropic manner near the surfaces of LiFePO4 crystals. Moreover, a substantial amount of cation exchanges between Li and Fe sites is identified as an energetically favorable configuration in some surface regions, showing excellent agreement with the calculation results of negative defect formation energies. The findings in this study provide insight into developing better ways to avoid degradation of lithium mobility through the surface as well as scientifically notable features regarding the distribution of exchange defects in olivine phosphates. PMID:25565086

Chung, Sung-Yoon; Choi, Si-Young; Kim, Tae-Hwan; Lee, Seongsu

2015-01-27

94

Microbial Weathering of Olivine  

NASA Technical Reports Server (NTRS)

Controlled microbial weathering of olivine experiments displays a unique style of nanoetching caused by biofilm attachment to mineral surfaces. We are investigating whether the morphology of biotic nanoetching can be used as a biosignature. Additional information is contained in the original extended abstract.

McKay, D. S.; Longazo, T. G.; Wentworth, S. J.; Southam, G.

2002-01-01

95

Exogenous Olivine on Vesta  

NASA Astrophysics Data System (ADS)

Vesta has conserved an early status of planetary evolution, demonstrated by the global coverage of HED lithology on its surface. Being sufficiently large to retain some material from slow projectiles, but small enough to prevent its complete evaporation during the impacts, this unique environment is ideal for distinction and identification of exogenous material. In particular, the distribution, concentration, and geological context of olivine exposures are poorly consistent with a Vestan mantle origin. Similar arguments are valid for the areas of dark carbonaceous chondrite-like lithology, and a few other features with unusual visual spectral slopes. Most olivine is found close to the large impact craters Bellicia, Arruntia, and Pomponia in the northern hemisphere, whose ejecta sheet is characterized by a mixing trend from an HED lithology to S- or A-type asteroid material. The olivine has diagnostic significance for the extent and duration of differentiation during the early accretion of parent bodies in the asteroid region. Sources for exogenous olivine are available in Vesta’s environment among A- and S-type asteroids. It is not clear, however, if it is derived mainly from achondritic or chondritic sources. On the other hand, the lack of evidence for Vesta’s mantle material implies constraints on its inner structure, e.g. the depth of the crust.

Hoffmann, Martin; Nathues, Andreas; Schäfer, Michael; Thangjam, Guneshwar; Le Corre, Lucille; Vishnu, Reddy; Christensen, Ulrich; Mengel, Kurt; Sierks, Holger; Vincent, Jean-Baptist; Cloutis, Edward A.; Russell, Christopher T.; Schäfer, Tanja; Gutierrez-Marques, Pablo; Hall, Ian; Ripken, Joachim; Büttner, Irene

2014-11-01

96

Enhanced electrochemical properties of LiFePO4 (LFP) cathode using the carboxymethyl cellulose lithium (CMC-Li) as novel binder in lithium-ion battery.  

PubMed

Novel water-based binder CMC-Li is synthesized using cotton as raw material. The mechanism of the CMC-Li as a binder is reported. Electrochemical properties of batteries cathodes based on commercially available lithium iron phosphate (LiFePO4, LFP) and CMC-Li as a water-soluble binder are investigated. CMC-Li is a novel lithium-ion binder. Compare with conventional poly(vinylidene fluoride) (PVDF) binder, and the battery with CMC-Li as the binder retained 97.8% of initial reversible capacity after 200 cycles at 176 mAh g(-1), which is beyond the theoretical specific capacity of LFP. Constant current charge-discharge test results demonstrate that the LFP electrode using CMC-Li as the binder has the highest rate capability, follow closely by that using PVDF binder. The batteries have good electrochemical property, outstanding pollution-free and excellent stability. PMID:25037391

Qiu, Lei; Shao, Ziqiang; Wang, Daxiong; Wang, Wenjun; Wang, Feijun; Wang, Jianquan

2014-10-13

97

Mixed Salts of LiTFSI and LiBOB for Stable LiFePO4-Based Batteries at Elevated Temperatures  

SciTech Connect

To achieve stable long-term cycling stability at elevated temperatures, mixed salts of LiTFSI and LiBOB are used to replace LiPF6 salt in non-aqueous electrolytes for LiFePO4-based batteries. It is found that adding LiBOB in LiTFSI-based electrolytes effectively prevents the severe corrosion to Al current collectors that often is observed in LiTFSI-based electrolytes, which have high thermal stability. The cells using LiTFSI-LiBOB-based electrolytes demonstrate superior high temperature (60 ?C) stability and very similar room temperature performance (i.e., cycling stability and rate capability) when compared to cells using the LiPF6-based electrolyte.

Chen, Xilin; Xu, Wu; Engelhard, Mark H.; Zheng, Jianming; Zhang, Yaohui; Ding, Fei; Qian, Jiangfeng; Zhang, Jiguang

2014-01-13

98

Optimizing LiFePO4@C Core-Shell Structures via the 3-Aminophenol-Formaldehyde Polymerization for Improved Battery Performance.  

PubMed

Polyanion-type cathode materials are well-known for their low electronic conductivity; accordingly, the addition of conductive carbon in the cathode materials becomes an indispensable step for their application in lithium ion batteries. To maximize the contribution of carbon, a core-shell structure with a full coverage of carbon should be favorable due to an improved electronic contact between different particles. Here, we report the formation of a uniform carbon nanoshell on a typical cathode material, LiFePO4, with the shell thickness precisely defined via the 3-aminophenol-formaldehyde polymerization process. In addition to the higher discharge capacity and the improved rate capability as expected from the carbon nanoshell, we identified that the core-shell configuration could lead to a much safer cathode material as revealed by the obviously reduced iron dissolution, much less heat released during the cycling, and better cyclability at high temperature. PMID:25453295

Chi, Zi-Xiang; Zhang, Wei; Wang, Xu-Sheng; Cheng, Fu-Quan; Chen, Ji-Tao; Cao, An-Min; Wan, Li-Jun

2014-12-24

99

X-ray absorption fine structure imaging of inhomogeneous electrode reaction in LiFePO4 lithium-ion battery cathode  

NASA Astrophysics Data System (ADS)

To improve the performance of rechargeable lithium-ion batteries, a microscopic understanding of the electrochemical reaction at the cathode is necessary. The spatial distribution of the electrode redox reaction for the LiFePO4 cathode was analyzed by X-ray absorption fine structure (XAFS) imaging. Chemical state maps of the planar cathode electrode obtained by the in situ XAFS imaging revealed the inhomogeneity of the chemical state of Fe during the charge/discharge process. The chemical state maps for the reverse charge/discharge process demonstrated the reversibility of the inhomogeneous distribution. The in-plane radial progress of the reaction distribution strongly suggests that the inhomogeneous electrode reaction is caused by the difference in electrical conductivity; the charging and discharging reactions proceed through reaction channels with low electrical resistance in the cathode.

Katayama, Misaki; Sumiwaka, Koichi; Miyahara, Ryota; Yamashige, Hisao; Arai, Hajime; Uchimoto, Yoshiharu; Ohta, Toshiaki; Inada, Yasuhiro; Ogumi, Zempachi

2014-12-01

100

Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance  

NASA Astrophysics Data System (ADS)

In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4 nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm-2 at 0.1 mA cm-2 (lowest rate) and 1.1 mA h cm-2 at 6 mA cm-2 (highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium.In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sol-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4 nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm-2 at 0.1 mA cm-2 (lowest rate) and 1.1 mA h cm-2 at 6 mA cm-2 (highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01682c

Asfaw, Habtom D.; Roberts, Matthew R.; Tai, Cheuk-Wai; Younesi, Reza; Valvo, Mario; Nyholm, Leif; Edström, Kristina

2014-07-01

101

Synthesis and Performance of LiFe1-xMnxPO4 in Lithium-ion Battery  

NASA Astrophysics Data System (ADS)

Olivine-type lithium transition metal phosphates (i.e. LiFePO4) have been intensively investigated as promising electrode materials for rechargeable lithium-ion batteries. There have been attempts to improve energy density and voltage quality of phosphate based electrode. In this study, we have partially substituted Fe^II/Fe^III redox center with Mn^II/Mn^III in LiFePO4 that provides over 600 mV higher voltage. We prepared various compositions of LiFe1-xMnxPO4 (x=0, 0.2, 0.4, 0.6, 0.8 and 1) between the two end members (LiFePO4 - LiMnPO4). Due to intrinsic low electronic conductivity of lithium transition metal phosphates, we coat these materials with a uniform conductive carbon through a unique sol-gel process developed in our laboratory. In addition, we made a composite of the carbon coated phosphate with carbon nano-tubes to develop a highly conductive matrix electrode. We report the materials structure, morphology, electrical conductivity and electrochemical performances of LiFe1-xMnxPO4 using XRD, Raman spectroscopy, SEM, TEM, XPS, electrical conductivity and galvanostatic charge/discharge measurements.

Bazzi, Khadije; Nazri, Maryam; Vaishnava, Prem; Naik, Vaman; Nazri, Gholam-Abbas; Naik, Ratna

2013-03-01

102

Helium Diffusion in Olivine  

NASA Astrophysics Data System (ADS)

Diffusion of helium has been characterized in natural Fe-bearing olivine (~Fo90) and synthetic forsterite. Polished, oriented slabs of olivine were implanted with 3He, at 100 keV at a dose of 5x1015/cm2 or at 3.0 MeV at a dose of 1x1016/cm2. A set of experiments on the implanted olivine were run in 1-atm furnaces. In addition to the one-atm experiments, experiments on implanted samples were also run at higher pressures (2.6 and 2.7 GPa) to assess the potential effects of pressure on He diffusion and the applicability of the measured diffusivities in describing He transport in the mantle. The high-pressure experiments were conducted in a piston-cylinder apparatus using an "ultra-soft" pressure cell, with the diffusion sample directly surrounded by AgCl. 3He distributions following experiments were measured with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. This direct profiling method permits us to evaluate anisotropy of diffusion, which cannot be easily assessed using bulk-release methods. For diffusion in forsterite parallel to c we obtain the following Arrhenius relation over the temperatures 250-950°C: D = 3.91x10-6exp(-159 ± 4 kJ mol-1/RT) m2/sec. The data define a single Arrhenius line spanning more than 7 orders of magnitude in D and 700°C in temperature. Diffusion parallel to a appears slightly slower, yielding an activation energy for diffusion of 135 kJ/mol and a pre-exponential factor of 3.73x10-8 m2/sec. Diffusion parallel to b is slower than diffusion parallel to a (by about two-thirds of a log unit); for this orientation an activation energy of 138 kJ/mol and a pre-exponential factor of 1.34x10-8 m2/sec are obtained. This anisotropy is broadly consistent with observations for diffusion of Ni and Fe-Mg in olivine. Diffusion in Fe-bearing olivine (transport parallel to b) agrees within uncertainty with findings for He diffusion in forsterite. The higher-pressure experiments yield diffusivities in agreement with those from the 1-atm experiments, indicating that the results reported here can be reasonably applied to modeling He transport in the upper mantle. The insensitivity of He diffusion to pressure over the investigated range of conditions suggests that compression of the mineral lattice is not sufficient to significantly influence migration of the relatively small helium atoms, which likely diffuse via crystal interstices. The He diffusivities in this work are generally consistent with results from the study of Futagami et al. (1993), who measured He diffusion in natural olivine by outgassing 4He implanted samples, and with the diffusivities measured by bulk-release of 4He and 3He by Shuster et al. (2003), but are about 2 orders of magnitude slower than the recent findings of Tolstikhin et al. (2010) and Blard et al. (2008) . An up-temperature extrapolation of our data also show reasonable agreement with the higher-temperature measurements of Hart (1984). Blard et al. (2008) GCA 72, 3788-3803; Futagami et al. (1993) GCA 57, 3177-3194; Hart (1984) EPSL 70, 297-302; Shuster et al.( 2003) EPSL 217, 19-32; Tolstikhin et al. (2010) GCA 74, 1436-1447

Cherniak, D. J.; Watson, E. B.

2011-12-01

103

Real-time investigation on the influences of vanadium additives to the structural and chemical state evolutions of LiFePO4 for enhancing the electrochemical performance of lithium-ion battery  

NASA Astrophysics Data System (ADS)

The influences of adding vanadium to the structure evolution and electrochemical performance of LiFePO4 are systematically investigated by in-situ X-ray powder diffraction and X-ray absorption near edge structure spectroscopy. The results indicate that the addition of a small amount of vanadium (less than at 1%) significantly reduces the formation of non-crystalline (highly disordered) triphylite and remnant heterosite phases in the cathode of battery especially at the rate capability higher than 0.5C. The cycle stability of LiFePO4 cathode with vanadium additive after 80 cycles is improved by 14.9% compared to that without vanadium additive. Such an enhancement could be attributed to the ion diffusion kinetics being improved and inactive triphylite being reduced by the supervalent-vanadium additive in cathode during electrochemical redox cycles.

Hu, Chih-Wei; Chen, Tsan-Yao; Shih, Kai-Sheng; Wu, Pin-Jiun; Su, Hui-Chia; Chiang, Ching-Yu; Huang, An-Feng; Hsieh, Han-Wei; Chang, Chia-Chin; Shew, Bor-Yuan; Lee, Chih-Hao

2014-12-01

104

Determination of the Lamb-Mössbauer factors of LiFePO 4 and FePO 4 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 LiFe IIPO 4 (triphylite) in Li-ion batteries results in Fe IIIPO 4 (heterosite). LiFePO 4 was synthesized by solid state reaction at 800 °C under Ar flow from Li 2CO 3, FeC 2O 4·2H 2O and NH 4H 2PO 4 precursors in stoichiometric composition. FePO 4 was prepared from chemical oxidation of LiFePO 4 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 LiFePO 4 and ?M=359 K for FePO 4, 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

105

Non-uniform aging of cycled commercial LiFePO4//graphite cylindrical cells revealed by post-mortem analysis  

NASA Astrophysics Data System (ADS)

Aging of power-optimized commercial 2.3 Ah cylindrical LiFePO4//graphite cells to be used in hybrid electric vehicle is investigated and compared for three different aging procedures; (i) using a simulated hybrid electric vehicle cycle within a narrow SOC-range, (ii) using a constant-current cycle over a 100% SOC-range, and (iii) stored during three years at 22 °C. Postmortem analysis of the cells is performed after full-cell electrochemical characterization and discharge. EIS and capacity measurements are made on different parts of the disassembled cells. Material characterization includes SEM, EDX, HAXPES/XPS and XRD. The most remarkable result is that both cycled cells displayed highly uneven aging primarily of the graphite electrodes, showing large differences between the central parts of the jellyroll compared to the outer parts. The aging variations are identified as differences in capacity and impedance of the graphite electrode, associated with different SEI characteristics. Loss of cyclable lithium is mirrored by a varying degree of lithiation in the positive electrode and electrode slippage. The spatial variation in negative electrode degradation and utilization observed is most likely connected to gradients in temperature and pressure, that can give rise to current density and potential distributions within the jellyroll during cycling.

Klett, Matilda; Eriksson, Rickard; Groot, Jens; Svens, Pontus; Ciosek Högström, Katarzyna; Lindström, Rakel Wreland; Berg, Helena; Gustafson, Torbjörn; Lindbergh, Göran; Edström, Kristina

2014-07-01

106

Morphology-controlled synthesis of self-assembled LiFePO4/C/RGO for high-performance Li-ion batteries.  

PubMed

Novel architectured LiFePO4 (LFP) that consisted of ordered LFP nanocubes was prepared through a facile hydrothermal method using polyethylene glycol (PEG) as a surfactant. The micro/nanostructured LFP with various morphologies ranging from cube cluster to rugby-like structure was synthesized via controlling the pH values of the precursor. A reasonable assembly process elucidating the formation of the hierarchical structure is also provided based on the experimental results. After a combination of carbon (C) coating and reduced graphene oxide (RGO) wrapping, the obtained LFP/C/RGO composites exhibit enhanced electrochemical performance compared to that of blank LFP synthesized under the same condition. Among as-synthesized cube-cluster-like, dumbbell-like, rod-like, and rugby-like composites, the rugby-like LFP/C/RGO reveal the best electrochemical properties with the discharge specific capacity of ?150 mA h g(-1) after 100 cycles and a high reversible specific capacity of 152 mA h g(-1) at 0.1 C. The prepared LFP/C/RGO composite can be a promising cathode material for high energy, low cost, and environmentally friendly lithium-ion batteries. PMID:25233480

Lin, Mei; Chen, Yuming; Chen, Bolei; Wu, Xiao; Kam, Kifung; Lu, Wei; Chan, Helen Lai Wa; Yuan, Jikang

2014-10-22

107

Experiment and simulation of a LiFePO4 battery pack with a passive thermal management system using composite phase change material and graphite sheets  

NASA Astrophysics Data System (ADS)

A passive thermal management system (TMS) for LiFePO4 battery modules using phase change material (PCM) as the heat dissipation source to control battery temperature rise is developed. Expanded graphite matrix and graphite sheets are applied to compensate low thermal conductivity of PCM and improve temperature uniformity of the batteries. Constant current discharge and mixed charge-discharge duties were applied on battery modules with and without PCM on a battery thermal characteristics test platform. Experimental results show that PCM cooling significantly reduces the battery temperature rise during short-time intense use. It is also found that temperature uniformity across the module deteriorates with the increasing of both discharge time and current rates. The maximum temperature differences at the end of 1C and 2C-rate discharges are both less than 5 °C, indicating a good performance in battery thermal uniformity of the passive TMS. Experiments on warm-keeping performance show that the passive TMS can effectively keep the battery within its optimum operating temperature for a long time during cold weather uses. A three dimensional numerical model of the battery pack with the passive TMS was conducted using ANSYS Fluent. Temperature profiles with respect to discharging time reveal that simulation shows good agreement with experiment at 1C-discharge rate.

Lin, Chunjing; Xu, Sichuan; Chang, Guofeng; Liu, Jinling

2015-02-01

108

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

109

Origin of olivine at Copernicus  

NASA Technical Reports Server (NTRS)

The central peaks of Copernicus are among the few lunar areas where near-infrared telescopic reflectance spectra indicate extensive exposures of olivine. Other parts of Copernicus crater and ejecta, which were derived from highland units in the upper parts of the target site, contain only low-Ca pyroxene as a mafic mineral. The exposure of compositionally distinct layers including the presence of extensive olivine may result from penetration to an anomalously deep layer of the crust or to the lunar mantle. It is suggested that the Procellarum basin and the younger, superposed Insularum basin have provided access to these normally deep-seated crustal or mantle materials by thinning the upper crustal material early in lunar history. The occurrences of olivine in portions of the compositionally heterogeneous Aristarchus Region, in a related geologic setting, may be due to the same sequence of early events.

Pieters, C. M.; Wilhelms, D. E.

1985-01-01

110

Petrogenesis of Depleted Olivine-Phyric Shergottites  

NASA Astrophysics Data System (ADS)

Model crystallization and phase diagram calculations are used to understand petrogenesis of depleted olivine-phyric shergottites, Tissint and Y 980459, and compare them with an enriched olivine-phyric shergottite, LAR 06319.

Basu Sarbadhikari, A.

2014-09-01

111

The characteristic of carbon-coated LiFePO4 as cathode material for lithium ion battery synthesized by sol-gel process in one step heating and varied pH  

NASA Astrophysics Data System (ADS)

This research has been done on the synthesis of carbon coated LiFePO4 through sol-gel process. Carbon layer serves for improving electronic conductivity, while the variation of pH in the sol-gel process is intended to obtain the morphology of the material that may improve battery performance. LiFePO4/C precursors are Li2CO3, NH4H2PO4 and FeC2O4?H2O and citric acid. In the synthesis process, consisting of a colloidal suspension FeC2O4?H2O and distilled water mixed with a colloidal suspension consisting of NH4H2PO4, Li2CO3, and distilled water. Variations addition of citric acid is used to control the pH of the gel formed by mixing two colloidal suspensions. Sol in this study had a pH of 5, 5.4 and 5.8. The obtained wet gel is further dried in the oven and then sintered at a temperature 700°C for 10 hours. The resulting material is further characterized by XRD to determine the phases formed. The resulting powder morphology is observed through SEM. Specific surface area of the powder was tested by BET, while the electronic conductivity characterized with EIS.

Triwibowo, J.; Yuniarti, E.; Suharyadi, E.

2014-09-01

112

1, 3750, 2006 Olivine in kimberlites  

E-print Network

eED 1, 37­50, 2006 Olivine in kimberlites N. T. Arndt et al. Title Page Abstract Introduction reviewed discussion forum of eEarth What olivine, the neglected mineral, tells us about kimberlite, 37­50, 2006 Olivine in kimberlites N. T. Arndt et al. Title Page Abstract Introduction Conclusions

Paris-Sud XI, Université de

113

Supernova olivine from cometary dust  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

114

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

115

Performance and kinetics of LiFePO4-carbon bi-material electrodes for hybrid devices: A comparative study between activated carbon and multi-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Activated Carbon (AC) and multi-walled carbon nanotubes (CNT) are investigated as components of LiFePO4 (LFP)-based bi-material electrodes for hybrid devices. Firstly, the influence of their different morphological and porosimetric characteristics is correlated to the electrochemical performance. Furthermore, kinetic aspects are carefully studied (by means of galvanostatic cycling and cyclic voltammetry), in order to address the processes which determine the power performance. The results indicate that, independently from the carbon, under high current loads the electrode kinetics are limited by the transport of reactant to the LFP particles. In such conditions CNT allow, better than AC, rapid electrons and Li+ ions flow through the open network established in the electrode, thus enabling superior high rate performance, especially during pulsed operation.

Varzi, Alberto; Ramirez-Castro, Claudia; Balducci, Andrea; Passerini, Stefano

2015-01-01

116

Olivine-hosted Melt Inclusions in Olivine-Phyric Shergottite LAR 06319  

NASA Astrophysics Data System (ADS)

A newly-found, Antarctic, olivine-phyric shergottite, LAR 06319 which contains an enriched REE signature are studied. The results on olivine-hosted MI and their implications on the evolution of the LAR 06319 parental melt are reported.

Basu Sarbadhikari, A.; Liu, Y.; Day, J. M. D.; Taylor, L. A.

2009-03-01

117

The origin of ferrous zoning in Allende chondrule olivines  

Microsoft Academic Search

Very similar major and minor element compositions are noted in the ferrous olivine occurring in chondrules at olivine grain boundaries, along cracks in olivine grains, interleaved with enstatite, and in the inner portions of exposed olivine grain surface rims; simultaneous formation by a single process is therefore suggested. The ferrous chondrule olivine probably formed by the reaction of chondrules with

J. A. Peck; J. A. Wood

1987-01-01

118

Crystallization kinetics of olivine-phyric shergottites  

NASA Astrophysics Data System (ADS)

Crystal size distribution (CSD) and spatial distribution pattern (SDP) analyses are applied to the early crystallizing phases, olivine and pyroxene, in olivine-phyric shergottites (Elephant moraine [EET] 79001A, Dar al Gani [DaG] 476, and dhofar [Dho] 019) from each sampling locality inferred from Mars ejection ages. Trace element zonation patterns (P and Cr) in olivine are also used to characterize the crystallization history of these Martian basalts. Previously reported 2-D CSDs for these meteorites are re-evaluated using a newer stereographically corrected methodology. Kinks in the olivine CSD plots suggest several populations that crystallized under different conditions. CSDs for pyroxene in DaG 476 and EET 79001A reveal single populations that grew under steady-state conditions; pyroxenes in Dho 019 were too intergrown for CSD analysis. Magma chamber residence times of several days for small grains to several months for olivine megacrysts are calculated using the CSD slopes and growth rates inferred from previous experimental data. Phosphorus imaging in olivines in DaG 476 and Dho 019 indicate rapid growth of skeletal, sector-zoned, or patchy cores, probably in response to delayed nucleation, followed by slow growth, and finally rapid dendritic growth with back-filling to form oscillatory zoning in rims. SPD analyses indicate that olivine and pyroxene crystals grew or accumulated in clusters rather than as randomly distributed grains. These data reveal complex solidification histories for Martian basalts, and are generally consistent with the formation at depth of olivine megacryst cores, which were entrained in ascending magmas that crystallized pyroxenes, small olivines, and oscillatory rims on megacrysts.

Ennis, Megan E.; McSween, Harry Y.

2014-08-01

119

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

120

Diffusion of highly charged cations in olivine  

NASA Astrophysics Data System (ADS)

Diffusion of tungsten, titanium and phosphorus have been measured in natural iron-bearing olivine (~Fo90) and synthetic forsterite. Experiments were run under buffered conditions (with iron-wustite or Ni-NiO buffers) in 1-atm furnaces. The sources of diffusant for experiments were MgWO4 for tungsten diffusion, Mg2TiO4 for Ti diffusion, and AlPO4 for P diffusion; in all cases these compounds were pre-reacted at high temperature with Mg2SiO4 or Fe-bearing olivine prior to diffusion anneals. Samples were placed with the source materials in noble metal or silica capsules, which were sealed under vacuum in silica glass ampoules with solid buffers. Rutherford backscattering spectrometry (RBS) was used to measure depth profiles for all sets of experiments; measurements of P were also made with Nuclear Reaction Analysis using the 31P(?,p)34S reaction. These new data suggest marked differences among diffusivities of these cations, with titanium diffusion faster than diffusion of tungsten, but slower than diffusion of phosphorus over the conditions investigated. Diffusivities of all of these elements appear significantly slower than those of divalent cations in olivine. These results will be discussed in context with extant diffusion data for major, trace and minor elements in olivine. The effects of oxygen fugacity and olivine composition on diffusion, and potential implications for diffusion mechanisms will also be considered.

Cherniak, D. J.; Watson, E. B.; Liang, Y.

2012-12-01

121

Shock-produced olivine glass - First observation  

NASA Technical Reports Server (NTRS)

Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, /Mg(0.88)Fe(0.12)/2SiO4, recovered from peak pressures of about 56 billion pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation of olivine 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 billion 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, G. L., Jr.; Christie, J. M.; Heuer, A. H.

1977-01-01

122

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

123

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

E-print Network

. When conductive carbons are added to the reaction medium, excellent electrochemical behavior for electrochemical applications Jiajun Chen a , Michael J. Vacchio a , Shijun Wang a , Natalya Chernova a , Peter Y this material is inherently low cost, a manufacturing process that produces electrochemically-active LiFePO4

Suzuki, Masatsugu

124

Shock Effects in Olivine from Mocs Chondrite  

NASA Astrophysics Data System (ADS)

The Mocs (syn. Moci) meteorite, classified as L6 chondrite by Van Schmus and Wood [1] and recently reclassified as L5-6 by Miura et al. [2], fell on February 3, 1882, 16.00 hrs. , over a large area (15 km by 3 km) in Transylvania (Cluj District). Olivine from six fragments of the Mocs chondrite was analyzed by optical microscopy, scanning electron microscopy with energy dispersive X-ray analysis and X-ray powder diffractometry. Olivine occurs as grains in matrix or chondrules: barred olivine chondrules, composed of parallel sets of prismatic olivine crystals and devitrified glass and porphyritic olivine chondrules, which consist mainly of fine-grained olivine crystals and glassy materials of feldspsr composition. In order to determine the mineralogical and chemical effects of shock metamorphism (induced by collisions in space of the Mocs chondrite parent body), in every thin section, ten to twenty of the largest, randomly distributed olivine single crystals were examined by optical polarizing microscope with 20X- or 40X- objectives [3] and with a JEOL JSM-5400 scanning electron microscope for higher magnifications. The mineralogical effects observed are: undulatory extinction, irregular fractures, planar fractures, mosaicism and planar deformation features. These, correlated with the presence of small amounts of maskelynite (An 12-19) indicate that the maximum shock degree this meteorite experienced was S-5 [3]. The quantitative chemical analysis of 77 olivine grains in matrix from all thin sections (6), determined by a JEOL JSM-5400 scanning electron microscope with JED 2001 energy dispersive X-ray analysis at the Yamaguchi University, shows a variation in composition from Fa23 to Fa27 mole % fayalite (Avg. Fa25; PMD 2.3%), indicative of the L-group. The Fayalite content of olivine from chondrules ranges from Fa23 to Fa27 (Avg. Fa25; PMD 1.74%). According to DEER et al. [4], olivine composition can be measured also by X-ray powder diffractometry as Fa (mol per cent) = 100-(4233.91-1494.59 x d130). By using a RIGAKU computer assisted-diffractometer (radiation Cu K alpha = 1.54059) at the Yamaguchi University, the d130 value of olivine from Mocs meteorite was calculated as 2.781 A and the fayalite content as Fa23 mole % fayalite (Forsterite-ferroan as of IMA files, 1993) consistent also with the L-group. The cell parameters and density determined from the X-ray diffraction pattern are: a=4.779; b=10.297; c=6.032; V=296.857 and Dx=3.446 g/cm3. References: [1] Van Schmus W. R. and Wood J. A. (1967) GCA, 31, 747-765. [2] Miura Y. et al. (1995) Proc. NIPR Symp. Antarct. Meteorites, 8, in press. [3] Stoffler D. et al. (1991) GCA, 55, 3845-3867. [4] Deer W. A. et al. (1992) 2nd edition, 4.

Iancu, O. G.; Miura, Y.; Iancu, G.

1995-09-01

125

The origin of ferrous zoning in Allende chondrule olivines  

NASA Technical Reports Server (NTRS)

Very similar major and minor element compositions are noted in the ferrous olivine occurring in chondrules at olivine grain boundaries, along cracks in olivine grains, interleaved with enstatite, and in the inner portions of exposed olivine grain surface rims; simultaneous formation by a single process is therefore suggested. The ferrous chondrule olivine probably formed by the reaction of chondrules with very hot nebular vapors over a period of several hours, followed by the condensation of residual metal vapors onto those olivine surfaces that were in direct contact with the gas as the system cooled. The ferrous chondrule olivine that occurs interleaved with enstatite in Allende does not have a composition idendical to, and is not the precursor of, matrix olivine.

Peck, Julia A.; Wood, John A.

1987-01-01

126

Olivine, and the Origin of Kimberlite N. T. ARNDT1  

E-print Network

Olivine, and the Origin of Kimberlite N. T. ARNDT1Ã? , M. GUITREAU2 , A.-M. BOULLIER3 , A. LE ROEX4 ADVANCE ACCESS PUBLICATION JANUARY 12, 2010 Two types of olivine occur in kimberlites from Greenland or polycrystal- line aggregates that are a common constituent of many kimberlites. Olivine compositions

Tommasi, Andrea

127

Toward a unified hydrous olivine electrical conductivity law  

NASA Astrophysics Data System (ADS)

has long been proposed that water incorporation in olivine has dramatic effects on the upper mantle properties, affecting large-scale geodynamics, and triggering high electrical conductivity. But the laboratory-based laws of olivine electrical conductivity predict contrasting effects of water, precluding the interpretation of geophysical data in term of mantle hydration. We review the experimental measurements of hydrous olivine conductivity and conclude that most of data are consistent when errors in samples water contents are considered. We report a new law calibrated on the largest database of measurements on hydrous olivine oriented single crystals and polycrystals. It fits most of measurements within uncertainties, and is compatible with most of geophysical data within petrological constraints on mantle olivine hydration. The conductivity anisotropy of hydrous olivine might be higher than dry olivine, but preferential orientation should produce moderate anisotropy (˜0-0.8 log unit). In the oceanic mantle, the enhancement of olivine conductivity is limited to ˜1 log unit in the maximum range of mantle olivine water concentrations (0-500 wt ppm). Strongest enhancements are expected in colder regions, like cratonic lithospheres and subduction settings. High conductivities in melt-free mantle require great depths and high water concentrations in olivine (>0.1 S/m at >250 km and >200 wt ppm). Thus, the hydration of olivine appears unlikely to produce the highest conductivities of the upper mantle.

Gardés, Emmanuel; Gaillard, Fabrice; Tarits, Pascal

2014-12-01

128

Dissolution of Olivine Promoted by Ion Irradiation  

NASA Astrophysics Data System (ADS)

Recent laboratory simulations of ion irradiation effects on planetary minerals show changes in the surface composition of surfaces that are different depending on whether the analysis is done in-situ (without removing the sample from vacuum) or ex-situ using an electron microscope. We found that olivine samples that have been irradiated by keV ions show preferential loss of magnesium when exposed to water. Irradiations were done with 4 keV argon ions to fluences between 1015 and 1018 ions/cm2. Soak times in high purity water ranged from minutes to days, and exhibit the same degree of Mg depletion, independent of soak time. The concentration of magnesium on the surface of irradiated natural olivine decreases by 40% upon contact with water, as measured with x-ray photoelectron spectroscopy. This finding is important for laboratory simulations of regolith processes and for establishing procedures for the handling of irradiated samples, including those from sample return missions.

Cantando, E. D.; Dukes, C. A.; Baragiola, R. A.

2006-12-01

129

Shock-Produced Olivine Glass: First Observation  

Microsoft Academic Search

Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, (Mg0.88Fe0.12)2SiO4, 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 of olivine glass. The shocked sample exhibits a wide variation in the

Raymond Jeanloz; Thomas J. Ahrens; J. S. Lally; G. L. Nord Jr.; J. M. Christie; A. H. Heuer

1977-01-01

130

Water and Carbon Dioxide Adsorption at Olivine Surfaces  

SciTech Connect

Plane-wave density functional theory (DFT) calculations were performed to simulate water and carbon dioxide adsorption at the (010) surface of five olivine minerals, namely, forsterite (Mg2SiO4), calcio-olivine (Ca2SiO4), tephroite (Mn2SiO4), fayalite (Fe2SiO4), and Co-olivine (Co2SiO4). Adsorption energies per water molecule obtained from energy minimizations varied from -78 kJ mol-1 for fayalite to -128 kJ mol-1 for calcio-olivine at sub-monolayer coverage and became less exothermic as coverage increased. In contrast, carbon dioxide adsorption energies at sub-monolayer coverage ranged from -20 kJ mol-1 for fayalite to -59 kJ mol-1 for calcio-olivine. Therefore, the DFT calculations show a strong driving force for carbon dioxide displacement by water at the surface of all olivine minerals in a competitive adsorption scenario. Additionally, adsorption energies for both water and carbon dioxide were found to be more exothermic for the alkaline-earth (AE) olivines than for the transition-metal (TM) olivines and to not correlate with the solvation enthalpies of the corresponding divalent cations. However, a correlation was obtained with the charge of the surface divalent cation indicating that the more ionic character of the AE cations in the olivine structure relative to the TM cations leads to greater interactions with adsorbed water and carbon dioxide molecules at the surface and thus more exothermic adsorption energies for the AE olivines. For calcio-olivine, which exhibits the highest divalent cation charge of the five olivines, ab initio molecular dynamics simulations showed that this effect leads both water and carbon dioxide to react with the surface and form hydroxyl groups and a carbonate-like species, respectively.

Kerisit, Sebastien N.; Bylaska, Eric J.; Felmy, Andrew R.

2013-11-14

131

Tubular symplectic inclusions in olivine from the Fukang pallasite  

Microsoft Academic Search

Olivine from the Fukang meteorite, like that from many other pallasites, contains distinctive arrays of parallel, straight, tubular inclusions. They differ in their extension and linearity from those in terrestrial olivines. They comprise approximately 1% of the total volume. Most have lens-shaped cross-sections, but some are rounded. The major axis of the lens-shaped inclusions is rigorously oriented along olivine [001],

Michael R. Stevens; David R. Bell; Peter R. Buseck

2010-01-01

132

Search for Olivine Spectral Signatures on the Surface of Vesta  

NASA Technical Reports Server (NTRS)

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 groundbased 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 m 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.

2012-01-01

133

A scanning electron microscope study of olivine crystal surfaces  

NASA Technical Reports Server (NTRS)

SEM photographs were taken of euhedral olivine grains from the Murchison C2 chondrite and several terrestrial and lunar occurrences. In general, the crystal faces of the meteorite grains are rough and uneven, with irregular growth patterns. They are very similar to crystal faces on terrestrial olivine grains that formed by sublimation from a vapor phase. They are very different from the relatively smooth and featureless surfaces of magmatic olivine crystals that precipitated from igneous melts. Qualitatively, the surface morphology of the crystal supports the contention that many euhedral crystals of olivine in C2 meteorites condensed from a gas phase.

Olsen, E. J.; Grossman, L.

1974-01-01

134

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

135

Olivine in an unexpected location on Vesta's surface  

NASA Astrophysics Data System (ADS)

Olivine is a major component of the mantle of differentiated bodies, including Earth. Howardite, eucrite and diogenite (HED) meteorites represent regolith, basaltic-crust, lower-crust and possibly ultramafic-mantle samples of asteroid Vesta, which is the lone surviving, large, differentiated, basaltic rocky protoplanet in the Solar System. Only a few of these meteorites, the orthopyroxene-rich diogenites, contain olivine, typically with a concentration of less than 25 per cent by volume. Olivine was tentatively identified on Vesta, on the basis of spectral and colour data, but other observations did not confirm its presence. Here we report that olivine is indeed present locally on Vesta's surface but that, unexpectedly, it has not been found within the deep, south-pole basins, which are thought to be excavated mantle rocks. Instead, it occurs as near-surface materials in the northern hemisphere. Unlike the meteorites, the olivine-rich (more than 50 per cent by volume) material is not associated with diogenite but seems to be mixed with howardite, the most common surface material. Olivine is exposed in crater walls and in ejecta scattered diffusely over a broad area. The size of the olivine exposures and the absence of associated diogenite favour a mantle source, but the exposures are located far from the deep impact basins. The amount and distribution of observed olivine-rich material suggest a complex evolutionary history for Vesta.

Ammannito, E.; de Sanctis, M. C.; Palomba, E.; Longobardo, A.; Mittlefehldt, D. W.; McSween, H. Y.; Marchi, S.; Capria, M. T.; Capaccioni, F.; Frigeri, A.; Pieters, C. M.; Ruesch, O.; Tosi, F.; Zambon, F.; Carraro, F.; Fonte, S.; Hiesinger, H.; Magni, G.; McFadden, L. A.; Raymond, C. A.; Russell, C. T.; Sunshine, J. M.

2013-12-01

136

Did Ordinary Chondrite Impactors Deliver Olivine to Vesta?  

NASA Astrophysics Data System (ADS)

Ground-based and Hubble Space Telescope observations of asteroid Vesta suggested the presence of olivine. However, subsequent analysis of data from NASA’s Dawn mission proved that this “olivine-bearing unit”, identified as Oppia crater and its ejecta blanket, was composed of HED impact melt rather than olivine. The lack of widespread olivine in the 19 km deep Rheasilvia basin on the South Pole suggests that the crust-mantle boundary was not breached during the formation of the basin, and that Vesta’s crust is thicker than originally anticipated. Recently, local-scale olivine units have been reported in the walls and ejecta of two craters, Arruntia and Bellicia, located in the northern hemisphere of Vesta, 350-430 km from the Rheasilvia basin (Ammannito et al., 2013). These units were interpreted as exposed plutons by Clenet et al. (2014) rather than of mantle origin excavated during the formation of the Rheasilvia basin. We explored alternative sources for these olivine-rich units by reanalyzing the data published by Ammannito et al. (2013). Our mineralogical analysis gives olivine abundance between 70-80 vol.% consistent with those obtained previously (>60%). The pyroxene ferrosilite content and olivine abundance of the olivine-rich units are similar to ordinary chondrites. Meteoritic evidence suggests contamination of HEDs by several ordinary chondrite impactors including H, L and LL chondrites. This includes howardite JaH 556, which contains ~20 vol.% H chondrite material mixed with HED impact melt. Based on the non-diagnostic curve match and detailed mineralogical analysis using diagnostic spectral band parameters, we conclude that the olivine units in the northern hemisphere of Vesta could be explained by the delivery of exogenic H/L chondrite material rather than being a product of planetary differentiation.

Le Corre, Lucille; Reddy, Vishnu; Sanchez, Juan A.; Cloutis, Edward A.; Izawa, Matthew R.; Mann, Paul

2014-11-01

137

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

138

Development of crystal preferred orientation of olivine during diffusion creep: a matter of olivine crystal shape  

NASA Astrophysics Data System (ADS)

Crystalloagraphic preferred orientation (CPO) of olivine produced during dislocation creep is considered the primary cause of elastic anisotropy in the upper mantle of Earth and is used by seismologists to determine the direction of flow. Here we show that synthetic Fe-free olivine aggregates with either diopside or melt develop strong to weak CPO during grain boundary sliding (GBS) accommodated by diffusion. GBS on boundaries that correspond to specific crystallographic planes produces CPO. By combining the CPO patterns developed during tension and compression experiments, we predict formation in the mantle of three different CPO patterns depending on temperature and the presence of melt. Strong radial anisotropy is anticipated for GBS accommodated by diffusion during simple shear deformation at temperatures from 0.92*Ts to Ts (Ts: solidus temperature). These conditions correspond to depths where melting initiates to 50-100 km deeper and where strongly anisotropic and low seismic velocities are detected.

Miyazaki, T.; Sueyoshi, K.; Hiraga, T.

2013-12-01

139

Origin of ferrous zoning in Allende chondrule olivines  

SciTech Connect

Olivine crystals in Allende Type 1 chondrules have ferrous rims (Fa/sub 15-44/), a few microns thick, at grain surfaces and along crosscutting cracks. This ferrous olivine contains as much as 2 atomic pct. Al and Cr, and 0.2 pct. Ti. Along cracks, profiles of Fe, Al, Cr, and Ti are consistent with diffusional emplacement: these elements moved from an external source through the cracks as a vapor or by grain boundary diffusion, then into the olivine by lattice diffusion. The emplacement did not occur during an epoch of planetary metamorphism that partly equilibrated matrix and chondrule olivines, because (e.g.) neither matrix nor primary magnesian chondrule olivine contains even 1/10 this much, Al, Cr, and Ti. The authors argue that the source of these elements was the nebular gas, and emplacement occurred prior to accretion. The ferrous zones at olivine grain boundaries do not display simple diffusion profiles: rather they appear to be a composite of two concentric rims. The inner rims have compositions similar to those of the ferrous zones along cracks, and contain the highest concentrations of Al, Cr, and Ti. The outer rims are of uniformly high Fa content and relatively low Al, Cr, and Ti concentration. These outer rims appear to be additional material that condensed onto the chondrules after the diffusional emplacement event discussed earlier. Matrix olivine grains, which are identical to these rims in composition, condensed simultaneously.

Peck, J.A.; Wood, J.A.

1987-06-01

140

Exploring Exogenic Sources for the Olivine on Asteroid (4) Vesta  

E-print Network

The detection of olivine on Vesta is interesting because it may provide critical insights into planetary differentiation early in our Solar System's history. Ground-based and Hubble Space Telescope (HST) observations of asteroid (4) Vesta have suggested the presence of olivine on the surface. These observations were reinforced by the discovery of olivine-rich HED meteorites from Vesta in recent years. However, analysis of data from NASA's Dawn spacecraft has shown that this olivine-bearing unit is actually impact melt in the ejecta of Oppia crater. The lack of widespread mantle olivine, exposed during the formation of the 19 km deep Rheasilvia basin on Vesta's South Pole, further complicated this picture. Ammannito et al., (2013a) reported the discovery of local scale olivine-rich units in the form of excavated material from the mantle using the Visible and InfraRed spectrometer (VIR) on Dawn. Here we explore alternative sources for the olivine in the northern hemisphere of Vesta by reanalyzing the data from ...

Corre, Lucille Le; Sanchez, Juan A; Dunn, Tasha; Cloutis, Edward A; Izawa, Matthew R M; Mann, Paul; Nathues, Andreas

2015-01-01

141

Experimental Reproduction of Olivine rich Type-I Chondrules  

NASA Technical Reports Server (NTRS)

Ordinary chondritic meteorites are an abundant type of stony meteorite characterized by the presence of chondrules. Chondrules are small spheres consisting of silicate, metal, and sulfide minerals that experienced melting in the nebula before incorporation into chondritic meteorite parent bodies. Therefore, chondrules record a variety of processes that occurred in the early solar nebula. Two common types of unequilibrated chondrules with porphyritic textures include FeO-poor (type I) and FeO-rich (type II) each subdivided into an A (SiO2-poor) and B (SiO2-rich) series. Type IA chondrules include those with high proportions of olivine phenocrysts (>80% olivine) and type IB chondrules include those with high proportions of pyroxene phenocrysts (<20% olivine). An intermediate composition, type IAB chondrules include those chondrules in which the proportion of olivine phenocrysts is between 20-80%. We conducted high-temperature laboratory experiments (melting at 1550 C) to produce type I chondrules from average unequilibrated ordinary chondrite (UOC) material mixed with small amounts of additional olivine. The experiments were conducted by adding forsteritic rich olivine (San Carlos olivine, Fo 91) to UOC material (GRO 95544) in a 30/70 ratio, respectively. Results of these high temperature experiments suggest that we have replicated type IA chondrule textures and compositions with dynamic crystallization experiments in which a heterogeneous mixture of UOC (GRO 95544) and olivine (San Carlos olivine) were melted at 1550 C for 1 hr. and cooled at 5-1000 C/hr using graphite crucibles in evacuated silica tubes to provide a reducing environment.

Smith, Robert K.

2005-01-01

142

Olivine Deposits Associated with Impact Basins and Craters on Mars  

NASA Astrophysics Data System (ADS)

An analysis of the 1?m olivine spectral signature applied to the entire and final OMEGA dataset [1] shows numerous olivine-bearing deposits in the 3 main basins of Mars (Argyre, Isidis and Hellas). These signatures are among the strongest of Mars, which suggests compositions with higher iron content and/or larger grain size and/or larger abundance than the ones of widespread olivine-bearing deposits observed on large parts of the southern highlands [1]. A spectral modeling based on a radiative transfer model [2] indicates that their compositions are still close to the forsterite one with abundance in the range of [15,40%] and grain sizes of a few hundreds of ?m. These deposits are exclusively localized on Noachian terrains. Distribution of these deposits around Argyre basin clearly takes the form of discontinuous patches of olivine-bearing rocks on the basin terrace, which strongly suggest that their formation is related to the basin formation event. Recent numerical simulations of basin formation show that impact that formed the Argyre basin could have excavated upper mantle materials and emplaced discontinuous patches of melted mantle on the basin terraces [3]. The observed olivine deposits in Argyre are thus interpreted as olivine-bearing material excavated from the upper mantle during the impact. Olivine deposits distribution around the Hellas basin is not as clear as for Argyre because of young resurfacing processes that strongly affected its region. Olivine deposits are fewer and mainly localized on the northern terrace of Hellas. Most of them are detected in crater ejecta, while a few similar to Argyre olivine discontinuous patches are also observed suggesting that a mantle origin as for Argyre is possible. Olivine has been detected by several datasets in the Nili Fossae region and in the south of Isidis basin. The spectral modeling of OMEGA spectra indicates an olivine abundance of about 40% and megacrysts of several millimeters for the region of Nili Fossae [2]. Several plausible hypotheses has been discussed to explain this unusual concentration of olivine-rich outcrops in Nili Fossae assuming three possibilities for their emplacement relative to the formation of the Isidis basin : pre-impact [4,5], contemporaneous [6], or post-impact [7]. The pretty unique settings and compositions of these deposits in comparison to the two other major basins indicate a different origin, with the post-impact one as the preferred one. Other several localized exposures with strong olivine signature are also found throughout the southern highlands and the northern plains mostly associated with craters. Olivine-bearing material is found in craters floors but also in some crater ejecta implying the presence of an olivine-rich underlying layer. Of special interest are some craters totally filled by olivine-rich lava lakes, which could have erupted through local (impact-related) fractures. [1] A. Ody et al. (2011) LPSC XXXXII.[2] F. Poulet et al. (2009), Icarus 201, 84-101.[3] Stewart S. (2010) AGU, San Francisco, abstract #P43A-08. [4] Hoefen et al. (2003) Science,302,627-630.[5] Hamilton and Christensen (2005), Geology,33,433-436.[6]J.F. Mustard et al. (2007), JGR, 112, E08S03.[7] L.L Tornabene et al. (2008), JGR, 113, E10001.

Ody, A.; Poulet, F.; Langevin, Y.; Gondet, B.; Bibring, J.; Carter, J.

2011-12-01

143

Olivine Weathering: Abiotic Versus Biotic Processes as Possible Biosignatures  

NASA Technical Reports Server (NTRS)

A preliminary study to determine how abiotic versus biotic processes affect the weathering of olivine crystals. Perhaps the differences between these weathering processes could be used as biosignatures. Additional information is contained in the original extended abstract.

Longazo, T. G.; Wentworth, S. J.; McKay, D. S.; Southam, G.; Clemett, S. J.

2001-01-01

144

Systematics of Vanadium in Olivine from Planetary Basalts  

NASA Technical Reports Server (NTRS)

The systematics of vanadium in olivines from the Earth, Moon and Mars allows for the comparison of planetary basalt origin and igneous setting and process. Additional information is contained in the original extended abstract.

Karner, J. M.; Papike, J. J.; Shearer, C. K.

2002-01-01

145

Noble Gas Partitioning Between Olivine and Melt to 2 GPa  

NASA Astrophysics Data System (ADS)

We have extended our experimental measurements of noble gas partition coefficients to 2 GPa in the piston-cylinder device. The experimental set-up involves surrounding wafers of gem quality San Carlos olivine (250-1000 microns thick, 3-4 mm diameter) with diamond powder or vitreous carbon spheres. A layer of melt is placed at the bottom of the capsule which infiltrates the porous media and touches the olivine. This allows the original surface of the crystal to be identified and large coherent pieces of olivine to be recovered intact. The inner capsule is graphite and the outer capsule is Pt. Up to 60 bars of HeNeAr were preloaded into the Pt capsule before it was welded shut. This method combines a number of desireable qualities: 1) it avoids producing melt inclusions in the olivine, 2) it yields large areas of olivine to analyze by laser-ablation and 3) it has both melt and crystals present and in contact. The experimental glasses and olivine wafers were analyzed by laser-ablation noble gas mass spectrometry at the Open University, UK. Both depth profiles and cross-sections were analyzed on the olivine wafers. Equilibrium (flat) concentration profiles were only obtained for He in our experiments (up to 20 hr run durations). These yield olivine-melt partition coefficients (D) between 0.0007 and 0.002 at 1-2 GPa and at 1450. These values are within the range of measurements at low pressures (100 MPa or less), suggesting a minimal pressure effect on noble gas partitioning in the upper mantle. Henry’s Law behavior is maintained over 4 orders of magnitude variation in He concentration in the olivine (0.0001 to 1 ppm He). High near-surface concentrations of He (21ppm), Ne (36ppm) and Ar (4,360ppm) were observed in the olivine. The thickness of the enriched layer (5 microns) was the same for all three noble gases. We do not know the origin of the high near-surface concentrations, but if they were due to lattice diffusion of the noble gases, the thickness of the high concentration layer should decrease with the diffusivity of the noble gas from He to Ne to Ar. Thus we speculate that the high near-surface concentrations are due to a change in the material properties of the olivine.

Parman, S. W.; Kelley, S. P.; Ballentine, C. J.; van Orman, J. A.; Holland, G.

2009-12-01

146

Dissolution of olivine in basaltic liquids: experimental observations and applications.  

USGS Publications Warehouse

Rates of olivine dissolution in synthetic lunar basalt 77115 and a silica-enriched 77115 composition (Sil-77115) at superliquidus temperatures have been determined. Dissolution-rate data have been applied to the problem of the thermal history of fragment-laden impact-melt rocks of the lunar highlands. Textural and chemical criteria are discussed for the recognition of olivine resorption (and growth) phenomena in igneous rocks. -J.A.Z.

Thornber, C.R.; Huebner, J.S.

1985-01-01

147

Dislocation creep of fine-grained olivine  

NASA Astrophysics Data System (ADS)

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 ???n with n ˜ 7-8, or equally well by a Peierls creep law with exponential stress dependence. Due to the observed strong stress dependence the samples deform at significantly higher strain rates at a given stress than single crystals or coarse-grained polycrystals with n ˜ 3.5. TEM observations indicate the presence of dislocations with at least two different Burgers vectors, with free dislocations predominantly of screw character. Subgrain walls are present but are only weakly developed and have small misorientation angles. Both the rheology and dislocation structures are consistent with creep rate-limited by dislocation glide or cross slip for aggregates with grain sizes smaller than or approaching the recrystallized grain size. Deformation mechanism maps extrapolated to lithospheric temperatures using the melt-free diffusion creep rheology of Faul and Jackson (2007), the dislocation creep rheology of Hirth and Kohlstedt (2003), and the results described here indicate that deformation conditions of ultramylonitic shear zones fall near the triple point of Peierls, dislocation, and diffusion creep.

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

2011-01-01

148

Thermal properties of fully delithiated olivines  

NASA Astrophysics Data System (ADS)

Carbon-coated LiMnxFe1-xPO4 (x = 0, 0.5 and 1) is fully delithiated using NO2BF4 oxidant to investigate thermal behavior as a function of temperature as high as 700 °C in an Ar atmosphere. Reitveld refinement of X-ray diffraction (XRD) studies indicates readiness of chemical delithiation, except for Li0MnPO4, hydrated to amorphous MnPO4·2H2O. Thermal studies coupled with thermogravimetric analysis and in situ high temperature XRD demonstrate that the phase stability is affected by substituted Mn at an elevated temperature. The Li0FePO4 is stable up to 500 °C, maintaining the original olivine structure with a small amount of oxygen release. At higher temperatures, the phase was transformed to Fe3(PO4)2 and Fe2P2O7. In contrast, the phase transformation temperature is apparently reduced to as low as 200 °C by the addition of Mn into the crystal structure, which is related to the phase transformation to (Mn0.5Fe0.5)3(PO4)2 associated with fast oxygen loss from the original structure. As a result, the better thermal stability of Li0FePO4 is attributed to less oxygen loss, which delays the phase transformation, resulting in less exothermic heat in the temperature range.

Park, Jae-Sang; Oh, Seung-Min; Sun, Yang-Kook; Myung, Seung-Taek

2014-06-01

149

Thermal Emission Spectroscopy of 1 Ceres: Evidence for Olivine  

NASA Technical Reports Server (NTRS)

Thermal emission spectra of the largest asteroid 1 Ceres obtained from the Kuiper Airborne Observatory display features that may provide information on its surface mineralogy. A plot of the Ceres spectrum (calibrated using alpha Boo as a standard) divided by a standard thermal model (STM) is shown. Also shown is the emissivity spectrum deduced from reflectivity measurements for olivine grains <5 microns in diameter. The general shape of the Ceres and the olivine curves agree in essential details, such as the maxima from 8 to 12 microns, the minimum between 12 and 14 microns, the broad peak near 17.5 micron, and the slope beyond 22 micron. (Use of the 10 to 15-micron grain reflectivities provides a better match to the 12- to 14-micron dip. We used a value of unity for beta, the beaming factor associated with small-scale surface roughness in our STM. Adjustment of beta to a lower value raises the long-wavelength side of the Ceres spectrum, providing an even better match to the olivine curve.) The emissivity behavior roughly matches the emission coefficients which were calculated for olivine particles with a particle radius of 3 microns. Their calculations show not only the negative slope from 23 to 25 pm, but a continued decrease past 30 micron. The Ceres emissivity is thus similar to that of small olivine grains from 8 to 30 micron, but olivine's emissivity is lower from 5 to 8 pm.

Witteborn, F. C.; Roush, T. L.; Cohen, M.

1999-01-01

150

The origin of high hydrogen content in kimberlitic olivine: Evidence from hydroxyl zonation in olivine from kimberlites and mantle xenoliths  

NASA Astrophysics Data System (ADS)

Olivine macrocrysts in kimberlites are the most H-rich natural olivines known. Their xenocrystic provenance makes unclear whether H-enrichment occurred in the mantle prior to entrainment in kimberlite magma or during ascent. We present a Fourier transform infrared (FTIR) spectroscopy-based study of H zonation in kimberlite-derived olivine macrocrysts and/or olivine in xenoliths from the kimberlites Jericho (Nunavut, Canada), Beartooth (Northwest Territories, Canada), and Pipe 200 and Matsoku (Lesotho). The objective of the study was to determine whether changes in the concentration or speciation of H defects in proximity to the host kimberlite could yield insights into the origin of H-enrichment. Within the Group 1 region of the FTIR spectrum (~ 3420-3700 cm- 1), we find that olivines within xenoliths and macrocrysts show weak zonation or significant H depletions in rims. Peaks in the Group 2 region (~ 3260-3420 cm- 1) in Beartooth olivines show marked decrease in the crystal margins in comparison to Group 1 peaks. We find no preserved evidence for kimberlite-related H-enrichment in our dataset. We ascribe H depletion to diffusive H loss to infiltrating kimberlitic media. Diffusion models using coefficients previously applied to dehydrogenation of olivine and assuming a dry environment produce extremely short ascent durations incompatible with the results of other geospeedometers. This mismatch suggests that the poorly developed zonation in Jericho and Beartooth olivines indicates water-enrichment and/or faster ascent of these melts (in comparison to Pipe 200 and Matsoku), resulting in greater retention of mantle-derived H. A further significant factor in the mismatch is the differing speciation of H in most natural mantle-derived olivines in comparison to those used in diffusion experiments. We argue that the presence of presumably mantle-derived Group 2 H in olivine macrocrysts indicates rapid ascent of magma exsolving water-rich fluid, permitting preservation of these faster-diffusing defects only in particularly rapidly ascending kimberlite magmas. This interpretation explains empirical correlations between the presence of Group 2 bands, water-derived diamond resorption features, and volcaniclastic kimberlite facies.

Hilchie, Luke; Fedortchouk, Yana; Matveev, Sergei; Kopylova, Maya G.

2014-08-01

151

Galapagos Plume Source Lithology : Implications from Olivine Phenocryst Compositions C. Vidito ,C. Herzberg and D.Geist  

E-print Network

83844, USA. Ca (ppm) Mn (ppm) Fe/Mn (ppm) Ni (ppm) Mg-Number Mg-Number Olivines Peridotite Derivative Magmas (13-20% MgO) Olivines Peridotite Derivative Magmas (8-13% MgO) Olivines Peridotite Primary Magmas (8-38% MgO) Olivine Phenocryst Composition Fertile Peridotite Source (3.45% CaO) Olivine Phenocryst

Geist, Dennis

152

Formation of a metastable olivine wedge in a descending slab  

SciTech Connect

We present a thermal model of a descending slab in which the transformation of olivine to spinel is controlled by pressure- and temperature-dependent reaction kinetics. Two different formulations of the kinetics are considered with the main discriminant being the temperature range over which olivine converts to spinel at pressures of about 15 GPa (about 500{degree}{endash}515{degree}C and 560{degree}{endash}650{degree}C). We use a finite element method to solve the coupled heat conduction (perpendicular and parallel to the dip of the slab) and kinetics equations, and we include the latent heat of the phase transformation. Latent heat release together with heat conduction parallel to the dip of the slab reduces significantly the length of the metastable olivine wedge and results in a very thin ({approx_lt}5km) two-phase region. We employ the thermal parameter v{tau}sin{delta} (v is the velocity of the descending slab, {tau} is the age of the slab, and {delta} is the dip of the slab to the horizontal) to interpret the results for the length of the metastable wedge. For values of the thermal parameter smaller than about 4000 and 7000 km, depending on the model of the kinetics, no metastable olivine wedge exists (the critical value of 7000 km for the thermal parameter corresponds to the kinetics model with the lowest transition temperature range). The length of the metastable olivine wedge is also found to be very sensitive to the model of the kinetics and to the effects of adiabatic heating. If the occurrence of deep earthquakes is related to the transformation of metastable olivine to spinel, then data on earthquake depth versus thermal parameter require that the onset of the reaction takes place at temperatures of about 550{degree}{endash}575{degree}C. In this case the slab thermal parameter must be larger than 10,000 km for the metastable olivine wedge to extend down to 660 km depth. But deep earthquakes occur near 660 km depth in slabs with thermal parameter as small as about 5000 km (South America, for example). Either some deep earthquakes are unrelated to olivine metastability or our knowledge of olivine-spinel reaction kinetics is incomplete.{copyright} 1997 American Geophysical Union

Devaux, J.P. [Department of Earth and Space Sciences, University of California, Los Angeles, California (United States)] [Department of Earth and Space Sciences, University of California, Los Angeles, California (United States); Schubert, G. [Department of Earth and Space Sciences, University of California, Los Angeles, California (United States)] [Department of Earth and Space Sciences, University of California, Los Angeles, California (United States); [Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California (United States); Anderson, C. [Engineering Sciences and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Engineering Sciences and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

1997-11-01

153

Extraction of in situ cosmogenic 14C from olivine  

USGS Publications Warehouse

Chemical pretreatment and extraction techniques have been developed previously to extract in situ cosmogenic radiocarbon (in situ 14C) from quartz and carbonate. These minerals can be found in most environments on Earth, but are usually absent from mafic terrains. To fill this gap, we conducted numerous experiments aimed at extracting in situ 14C from olivine ((Fe,Mg)2SiO4). We were able to extract a stable and reproducible in situ 14C component from olivine using stepped heating and a lithium metaborate (LiBO2) flux, following treatment with dilute HNO3 over a variety of experimental conditions. However, measured concentrations for samples from the Tabernacle Hill basalt flow (17.3 ?? 0.3 ka4) in central Utah and the McCarty's basalt flow (3.0 ?? 0.2 ka) in western New Mexico were significantly lower than expected based on exposure of olivine in our samples to cosmic rays at each site. The source of the discrepancy is not clear. We speculate that in situ 14C atoms may not have been released from Mg-rich crystal lattices (the olivine composition at both sites was ~Fo65Fa35). Alternatively, a portion of the 14C atoms released from the olivine grains may have become trapped in synthetic spinel-like minerals that were created in the olivine-flux mixture during the extraction process, or were simply retained in the mixture itself. Regardless, the magnitude of the discrepancy appears to be inversely proportional to the Fe/(Fe+Mg) ratio of the olivine separates. If we apply a simple correction factor based on the chemical composition of the separates, then corrected in situ 14C concentrations are similar to theoretical values at both sites. At this time, we do not know if this agreement is fortuitous or real. Future research should include measurement of in situ 14C concentrations in olivine from known-age basalt flows with different chemical compositions (i.e. more Fe-rich) to determine if this correction is robust for all olivine-bearing rocks. ?? 2010 by the Arizona Board of Regents on behalf of the University of Arizona.

Pigati, J.S.; Lifton, N.A.; Timothy, Jull A.J.; Quade, Jay

2010-01-01

154

Tracing Oxygen Fugacity in Asteroids and Meteorites Through Olivine Composition  

NASA Technical Reports Server (NTRS)

Olivine absorptions are known to dominate telescopic spectra of several asteroids. Among the meteorite collection, three groups (excluding Martian meteorites), the pallasites, brachinites, and R group chondrites are plausible analogs to olivine-rich asteroids in that they are dominated by olivine. These meteorite groups have distinct petrologic origins. The primitive achondrite brachinites (which include both depleted and undeleted subgroups) are products of relatively minor differentiation and evolved in oxidizing environments. R chondrites are also thought to have formed in high oxygen states, but are closely related to ordinary chondrites (yet with their own distinct compositions and oxygen isotopic signatures). In contrast, pallasites, widely thought to be mantle components from much more evolved bodies, formed in more reducing environments. Petrologic indicators that are identifiable in spectral data must be used in order to infer the petrologic history of asteroids from surveys of their actual population. As discussed below, olivine composition (e.g. Fa#) can provide key constraints in exploring the origin and significance of olivine dominated asteroids.

Sunshine, J. M.; Bus, S. J.; Burbine, T. H.; McCoy, T. J.

2005-01-01

155

Exotic Olivine in Antarctic Angrites LEW 87051 and Asuka 881371  

NASA Astrophysics Data System (ADS)

Angrites are basaltic meteorites with very early formation ages [e.g., 1] suggesting magrnatic activity on their parent body shortly after accretion. To constrain the nature of this magmatism, it is necessary to determine the composition of the melts parental to the angrite meteorites so that these melts can be compared with known phase relationships. Of the four known angrites, Angra dos Reis is highly differentiated and has had a complex history [e.g.,2]. LEW 86010 is probably a low-temperature partial melt containing minor accumulated plagioclase [3]. LEW 87051 (LEW 87) contains porphyritic olivine in a fine-grained groundmass, and the olivine crystals have variously been interpreted as phenocrysts [e.g., 4], xenocrysts [e.g., 5], and compound crystals in which exotic xenocryst cores have been overgrown by olivine that crystallized from the melt [e.g 6]. Asuka 881371 (Asuka 88) contains large olivine crystals in a medium-grained groundmass [7 and these large olivines are unambiguously xenocrysts that are not directly related to the melt in which they now reside [9], and may shed light on the olivines in LEW 87. Several lines of evidence point towards the exotic nature of the large olivines in Asuka 88. Despite being internally homogeneous, these crystals show large variations in composition from one crystal to another. Such variations are shown for Ca and Mg/Mg+Fe in Fig. 1, but are also observed for Cr, Al, and Y. Moreover, the concentrations of these elements in the large olivines are different from the concentrations in the cores of the groundmass olivines that were obviously the first minerals to crystallize from the Asuka 88 melt (Fig 1). Thus the large olivines could not have been in equilibrium with one another nor with the host melt. Furthermore, along healed fractures the the large olivines have been altered towards the groundmass olivine composition either through physical invasion of melt or by enhanced surface diffusion along the fractures. However, despite the clear exotic relationship to the Asuka 88 melt, the O isotopic composition of one olivine xenocryst falls within the angrite group [9], so the xenocrysts are probably not completely exotic to the angrite parent body. By analogy with Asuka 88, we infer that the Mg-rich cores of some porphyritic olivines in LEW 87 are xenocrysts (Fig. 1), but the main portions of these crystals surrounding the cores (labeled LEW 87 phenos in Fig. 1) grew from the LEW 87 melt. Agreement in minor elements between the main portions of LEW 87 olivines and synthetic olivines from LEW 87 experiments supports this interpretation (Fig. 1). We plan to use elemental mapping to locate more cores in LEW 87, to look for core-to-core variation and to measure additional profiles to test for diffusive equilibration between xenocrysts and the outer part of the olivine or groundmass. Using the compositions of first olivines to crystallize from the parent melts of both meteorites and K(sub)(DFe/Mg) of 0.29 from LEW 87 crystallization experiments, we calculate that the bulk compositions reported for Asuka 88 by [9] and LEW 87 by [12] have about 11% and 20% excess olivine (exotic or accumulated) of Fo(sub)83 and Fo(sub)81 respectively. References: [1] Nyquist L. et al. (1994) Meteoritics, 29, 872-885. [2] Mittlefehldt D. and Lindstrom M. (1990) GCA, 54, 3209-3218. [3] McKay G. et al. (1988) LPS XIX, 762-763. [4] McKay G. et al. (1990) LPS XXI, 771-772. [5] Prinz et al. (1990) LPS XXI, 979. [6] Mikouchi T. et al. (1995) LPS XXVI, 973-974. [7] Yanai K. (1994) Proc. NIPR Symp. Antarc. Meteorites, 7, 30-41. [8] McKay G. et al. (1995) Antarc. Meteorites, XX, 155-158. [9] Warren P. et al. (1995) Antarc. Meteorites, XX, 261-264. [10] Warren P. and Kallemeyn G. (1990) LPS XXI, 1295-1296.

McKay, G.; Crozaz, G.; Mikouchi, T.; Miyamoto, M.

1995-09-01

156

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

157

The identification of crystalline olivine in cometary silicates  

NASA Astrophysics Data System (ADS)

An intermediate-resolution spectrum of the 8-13 micron region in comet Halley is obtained which shows a prominent silicate emission feature with structure not observed before in other comets or in interstellar silicates. The presence of a strong 11.3 micron peak reported by Bregman and coworkers is confirmed, and evidence is found for additional structure in the band. By comparison with spectra of interplanetary dust particles and laboratory silicates, it is concluded that small crystalline olivine particles are a major component of the silicates in this comet; other silicates (e.g., amorphous or hydrated) must also be present. The identification of crystalline olivine in this part of the spectrum is supported by the observation of four peaks in 20-50 micron airborne spectra of this comet which have also been attributed to olivine.

Campins, H.; Ryan, E. V.

1989-06-01

158

Thermal Emission Spectroscopy of 1 Ceres: Evidence for Olivine  

NASA Technical Reports Server (NTRS)

Thermal emission spectra of the largest asteroid, 1 Ceres, obtained from the Kuiper Airborne Observatory display features that may provide information about its surface mineralogy. The emissivity, obtained by dividing the spectra by a standard thermal model, is compared with emissivity spectra of olivines and phyllosilicates deduced via Kirchoff's law from reflectivity measurements. The spectra provide a fairly good match to fine grained olivines (0 to 5 micrometer size range). The smoothness of the spectrum beyond 18 micrometers is an indication of particles smaller than 50 micrometers. While the abrupt rise in emissivity near 8 micrometers matches many silicates, the distinct emissivity minimum centered near 12.8 micrometers is consistant with iron-poor olivines, but not with phyllosilicates. It suggests the presence of opaques and does not exclude a mixture with organics and fine-grained phyllosilicates.

Witteborn, Fred. C.; Roush, Ted L.; Cohen, Martin

1999-01-01

159

Water Retention and Rheology of Ti-doped, Synthetic Olivine  

NASA Astrophysics Data System (ADS)

Upper mantle flow laws are currently based almost entirely on experiments with olivine from San Carlos in Arizona. Synthetically produced olivine enables the exploration of the effects of trace elements on the rheology. We have conducted a range of experiments in a gas medium apparatus with solution-gelation derived olivine that show that titanium is the most effective in binding water in the olivine structure. The FTIR signature of this structurally bound water is most similar to that of water-undersaturated natural olivine with absorption bands at 3575 and 3525 cm-1. Water added, titanium-free solgel contains little water after hotpressing and shows adsorption bands at wavenumbers near 3200 cm-1. Noble metal capsules such as Pt or AuPd, providing more oxidizing conditions, are more effective in retaining water. Experiments with NiFe-lined welded Pt capsules retain no more water than NiFe lined samples without Pt capsule. Water retention is, however, again dependent on trace element content, with Ti doped samples containing tens of ppm after hotpressing. By comparison undoped samples run under the same conditions contain little water, again with different FTIR spectra to Ti-doped samples. Our experiments suggest that Ti by itself, or with water contents at the FTIR detection limit enhances diffusion creep rates relative to undoped, dry solgel olivine. Water contents around 10 ppm in NiFe wrapped samples show an enhancement of strain rates of more than one order of magnitude. The addition of Ti, together with the presence of water, also enhances grain growth. For more coarse-grained samples in the dislocation creep regime the enhancement of the stain rate as a function of water content is approximately consistent with the flow laws of Hirth and Kohlstedt (2003).

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

2012-12-01

160

A Survey of Olivine Alteration Products Using Raman Spectroscopy  

NASA Technical Reports Server (NTRS)

Identification of mineral alteration products will aid in the crucial task of interpreting past Martian environmental conditions, especially aqueous environments. Olivine has been identified at the surface of Mars and is readily altered in aqueous environments. Using Raman spectroscopy, we studied three rocks with altered olivine and compared the data with mineral chemistry from electron microprobe analysis. Although the alteration in all three samples has loosely been called iddingsite their appearances and modes of occurrences differ as described. Alteration products in all three samples are likely fine-grained mixtures.

Kuebler, K.; Jolliff, B. L.; Wang, A.; Haskin, L. A.

2004-01-01

161

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

162

Amoeboid olivine aggregates from CH carbonaceous chondrites  

NASA Astrophysics Data System (ADS)

Amoeboid olivine aggregates (AOAs) in CH carbonaceous chondrites are texturally and mineralogically similar to those in other carbonaceous chondrite groups. They show no evidence for alteration and thermal metamorphism in an asteroidal setting and consist of nearly pure forsterite (Fa<3; in wt%, CaO = 0.1-0.8, Cr2O3 = 0.04-0.48; MnO < 0.5), anorthite, Al-diopside (in wt%, Al2O3 = 0.7-8.1; TiO2 < 1), Fe,Ni-metal, spinel, and, occasionally, low-Ca pyroxene (Fs1Wo2-3), and calcium-aluminum-rich inclusions (CAIs). The CAIs inside AOAs are composed of hibonite, grossite, melilite (Åk13-44), spinel, perovskite, Al,Ti-diopside (in wt%, Al2O3 up to 19.6; TiO2 up to 13.9), and anorthite. The CH AOAs, including CAIs within AOAs, have isotopically uniform 16O-rich compositions (average ?17O = -23.4 ± 2.3‰, 2SD) and on a three-isotope oxygen diagram plot along ?slope-1 line. The only exception is a low-Ca pyroxene-bearing AOA 1-103 that shows a range of ?17O values, from -24‰ to -13‰. Melilite, grossite, and hibonite in four CAIs within AOAs show no evidence for radiogenic 26Mg excess (?26Mg). In contrast, anorthite in five out of six AOAs measured has ?26Mg corresponding to the inferred initial 26Al/27Al ratio of (4.3 ± 0.7) × 10-5, (4.2 ± 0.6) × 10-5, (4.0 ± 0.3) × 10-5, (1.7 ± 0.2) × 10-5, and (3.0 ± 2.6) × 10-6. Anorthite in another AOA shows no resolvable ?26Mg excess; an upper limit on the initial 26Al/27Al ratio is 5 × 10-6. We infer that CH AOAs formed by gas-solid condensation and aggregation of the solar nebula condensates (forsterite and Fe,Ni-metal) mixed with the previously formed CAIs. Subsequently they experienced thermal annealing and possibly melting to a small degree in a 16O-rich gaseous reservoir during a brief epoch of CAI formation. The low-Ca pyroxene-bearing AOA 1-103 may have experienced incomplete melting and isotope exchange in an 16O-poor gaseous reservoir. The lack of resolvable ?26Mg excess in melilite, grossite, and hibonite in CAIs within AOAs reflects heterogeneous distribution of 26Al in the solar nebula during this epoch. The observed variations of the inferred initial 26Al/27Al ratios in anorthite of the mineralogically pristine and uniformly 16O-rich CH AOAs could have recorded (i) admixing of 26Al in the protoplanetary disk during the earliest stages of its evolution and/or (ii) closed-system Mg-isotope exchange between anorthite and Mg-rich minerals (spinel, forsterite, and Al-diopside) during subsequent prolonged (days-to-weeks) thermal annealing at high temperature (?1100 °C) and slow cooling rates (?0.01 K h-1) that has not affected their O-isotope systematics. The proposed thermal annealing may have occurred in an impact-generated plume invoked for the origin of non-porphyritic magnesian chondrules and Fe,Ni-metal grains in CH and CB carbonaceous chondrites about 5 Myr after formation of CV CAIs.

Krot, Alexander N.; Park, Changkun; Nagashima, Kazuhide

2014-08-01

163

Influence of aluminum on the hydrothermal alteration rate of olivine  

NASA Astrophysics Data System (ADS)

The reactivity of ultramafic rocks under hydrothermal conditions controls chemical fluxes at the interface between the internal and external reservoirs of silicate planets. On Earth, hydration of ultramafic rocks is ubiquitous and operates from deep subduction zones to shallow lithospheric environments where it considerably affects the physical and chemical properties of rocks and can interact with the biosphere. This process also has key emerging societal implications, such as the production of hydrogen as a source of carbon-free energy. To date, the chemical model systems used to reproduce olivine hydrothermal alteration lead to the formation of serpentine with sluggish reaction rates. Although aluminum is common in geological environments and in hydrothermal systems in particular, its role in serpentinization or olivine dissolution has not been investigated under hydrothermal conditions. Nevertheless, abundant Al supply is expected in fluids released from dehydration of metapelites in subduction zones as well as during the hydrothermal alteration of gabbros at mid-ocean ridges. Aluminum was also abundant in primitive environments of both the Earth and Mars, stored in either Al-rich minerals like plagioclase or Al-enriched ultramafic lavas. We have investigated the role of Al on the hydrothermal alteration of olivine in a series of experiments performed in a low-pressure diamond anvil cell while following the reaction progress in situ by optical imaging and by confocal Raman spectroscopy. Experiments were run for 4.5 to 7.5 days with two olivine grains reacted in saline water (0.5 molal NaCl) at 200°C and 300°C, and P=200 MPa. After two days, olivine crystals were fully transformed to an aluminous serpentine, also enriched in iron. The very fast precipitation of serpentine may inhibit magnetite nucleation here. However, this does not rule out an H2 production since serpentines classically incorporate non negligible amount of ferric iron in their structure. The presence of Al in the hydrothermal fluid increases the rate of olivine serpentinization by more than one order of magnitude by increasing olivine solubility and enhancing serpentine precipitation. The mechanism responsible for this increased solubility has to be investigated further but this result motivates a re-evaluation of the natural rates of olivine serpentinization and of olivine hydrolysis in general in a wide range of settings where olivines or peridotites are intimately associated with Al-providers. Such a fast reaction rate may affect the contribution of reaction-enhanced processes at the micrometer-scale, such as reaction-driven cracking, already proposed for enhancing serpentinization or carbonation of olivine. The effect of Al on lower crust and upper mantle metasomatism is expected to be even stronger at higher pressure in subduction zones where those reactions control the rheology and physical properties of the subducting plate and mantle wedge. Finally, this study also provides a way to accelerate serpentinization reactions towards economically feasible time-scale and temperature for industrial H2 production and/or CO2 remediation.

Andreani, M.; Daniel, I.; Pollet-Villard, M.

2013-12-01

164

Chemical zonation in olivine-hosted melt inclusions  

NASA Astrophysics Data System (ADS)

Significant zonation in major, minor, trace, and volatile elements has been documented in naturally glassy olivine-hosted melt inclusions from the Siqueiros Fracture Zone and the Galapagos Islands. Components with a higher concentration in the host olivine than in the melt (e.g., MgO, FeO, Cr2O3, and MnO) are depleted at the edges of the zoned melt inclusions relative to their centers, whereas except for CaO, H2O, and F, components with a lower concentration in the host olivine than in the melt (e.g., Al2O3, SiO2, Na2O, K2O, TiO2, S, and Cl) are enriched near the melt inclusion edges. This zonation is due to formation of an olivine-depleted boundary layer in the adjacent melt in response to cooling and crystallization of olivine on the walls of the melt inclusions, concurrent with diffusive propagation of the boundary layer toward the inclusion center. Concentration profiles of some components in the melt inclusions exhibit multicomponent diffusion effects such as uphill diffusion (CaO, FeO) or slowing of the diffusion of typically rapidly diffusing components (Na2O, K2O) by coupling to slow diffusing components such as SiO2 and Al2O3. Concentrations of H2O and F decrease toward the edges of some of the Siqueiros melt inclusions, suggesting either that these components have been lost from the inclusions into the host olivine late in their cooling histories and/or that these components are exhibiting multicomponent diffusion effects. A model has been developed of the time-dependent evolution of MgO concentration profiles in melt inclusions due to simultaneous depletion of MgO at the inclusion walls due to olivine growth and diffusion of MgO in the melt inclusions in response to this depletion. Observed concentration profiles were fit to this model to constrain their thermal histories. Cooling rates determined by a single-stage linear cooling model are 150-13,000 °C h-1 from the liquidus down to ~1,000 °C, consistent with previously determined cooling rates for basaltic glasses; compositional trends with melt inclusion size observed in the Siqueiros melt inclusions are described well by this simple single-stage linear cooling model. Despite the overall success of the modeling of MgO concentration profiles using a single-stage cooling history, MgO concentration profiles in some melt inclusions are better fit by a two-stage cooling history with a slower-cooling first stage followed by a faster-cooling second stage; the inferred total duration of cooling from the liquidus down to ~1,000 °C ranges from 40 s to just over 1 h. Based on our observations and models, compositions of zoned melt inclusions (even if measured at the centers of the inclusions) will typically have been diffusively fractionated relative to the initially trapped melt; for such inclusions, the initial composition cannot be simply reconstructed based on olivine-addition calculations, so caution should be exercised in application of such reconstructions to correct for post-entrapment crystallization of olivine on inclusion walls. Off-center analyses of a melt inclusion can also give results significantly fractionated relative to simple olivine crystallization. All melt inclusions from the Siqueiros and Galapagos sample suites exhibit zoning profiles, and this feature may be nearly universal in glassy, olivine-hosted inclusions. If so, zoning profiles in melt inclusions could be widely useful to constrain late-stage syneruptive processes and as natural diffusion experiments.

Newcombe, M. E.; Fabbrizio, A.; Zhang, Youxue; Ma, C.; Le Voyer, M.; Guan, Y.; Eiler, J. M.; Saal, A. E.; Stolper, E. M.

2014-07-01

165

ORIGINAL PAPER Titanium-and water-rich metamorphic olivine in high-pressure  

E-print Network

ORIGINAL PAPER Titanium- and water-rich metamorphic olivine in high-pressure serpentinites from 2013 Ã? Springer-Verlag Berlin Heidelberg 2014 Abstract Titanium- and water-rich metamorphic olivine (Fo

Jung, Haemyeong

166

Olivine-Phyric Shergottite LAR 06319: Its Relation to the Enriched Components in Martian Basalts  

NASA Astrophysics Data System (ADS)

Detailed petrology of Larkman Nunatak (LAR) 06319 are discussed for its olivine megacryst population in olivine-phyric shergottites, as well as the nature of the incompatible-element enriched component in martian basaltic magmas.

Basu Sarbadhikari, A.; Day, J. M. D.; Liu, Y.; Taylor, L. A.

2009-03-01

167

Metal-olivine associations and Ni-Co contents in two Apollo 12 mare basalts  

NASA Technical Reports Server (NTRS)

Olivine crystals in mare basalts 12004,8 and 12022,12 are normally zoned with Cr-poor rims. The Ni content of rare 2- to 10-micron metal inclusions in olivine decreases markedly as Fe/Mg in their immediate olivine hosts increases. Each metal grain appears to have been enclosed by late olivine almost immediately after it crystallized. The fractionation trend for the olivine and metal contrasts with the subsolidus equilibration trend for pallasites. For the basalts, not even local equilibrium of Fe, Ni and Co at metal/olivine interfaces can be detected by microprobe. Ni and Co concentrations range from about 300 ppm in olivine cores to about 70 ppm in rims. The limits of detection, at 95% confidence, are 36 ppm (Ni) and 25 ppm (Co). The distribution of Ni and Co in olivine, like that of Mg and Cr, records the depletion of these elements in the melt.

Hewins, R. H.; Goldstein, J. I.

1974-01-01

168

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

169

Textural evidence bearing on the origin of isolated olivine crystals in C2 carbonaceous chondrites  

NASA Technical Reports Server (NTRS)

In some cases the mechanical competence of chondrules in carbonaceous chondrites has been reduced by alteration of their mesostasis glass to friable phyllosilicate, providing a mechanism by which euhedral olivines can be separated from chondrules. Morphological features of isolate olivine grains found in carbonaceous chondrites are similar to those of olivine phenocrysts in chondrules. These observations suggest that the isolated olivine grains formed in chondrules, by crystallization from a liquid, rather than by condensation from a vapor.

Richardson, S. M.; Mcsween, H. Y., Jr.

1978-01-01

170

Spinel-olivine geothermometry in peridotites from ultramafic complexes  

Microsoft Academic Search

An empirical calibration of the spinel-olivine geothermometer (Evans and Frost, 1975) is attempted and applied to parageneses of lherzolitic rocks. In ultramafic complexes, most of the derived temperature estimates range between 700 ° and 850 °C, and appear generally lower than those given by other geothermometers, based upon Ca or Al contents of coexisting pyroxenes. A comparison of the different

Jacques Fabriès

1979-01-01

171

A reevaluation of the flow data for olivine  

NASA Astrophysics Data System (ADS)

The solid medium deformation experiments on polycrystalline olivine at pressures of 500-1500 MPa show steadily increasing creep strength with decreasing water content. Thus water content can significantly influence the strength of olivine. Room pressure experiments on olivine single crystals have been conducted under conditions of low pH2O and therefore should be compared with solid medium experiments on dried samples deformed under anhydrous conditions. The single crystals flow more rapidly by 2-3 decades in strain rate for a given stress. Three hypotheses regarding the origin of this strength discrepancy are: (1) solid medium sample strengths are higher due to the finite strength of the confining medium; (2) temperature gradients in the solid medium samples render them stronger; (3) the application of high confining pressure has significantly increased strength. These hypotheses have been analyzed and none of them appears to alter strain rates by more than a decade. Another hypothesis, that dislocations are pinned by iron oxide precipitates in the "dry" solid medium experiments, also does not appear likely. Unless some unknown effect in the solid medium apparatus results in anomalously high strength for olivine, the discrepancy must be attributed to fundamentally different behavior of the single crystal and the aggregate.

Vaughan, Peter J.

172

Scanning electron microscope observation of dislocations in olivine  

Microsoft Academic Search

Dislocations in olivine decorated by oxidation in air were observed with a scanning electron microscope (SEM) using a backscattered electron image (BEI). The decorated dislocations (and grain boundaries) were found to give clear bright images in this mode, indicating an increase of mean atomic number near the dislocation cores (and grain boundaries). This method of dislocation observation has a resolution

S. Karato

1987-01-01

173

A Study of Olivine Alteration to Iddingsite Using Raman Spectroscopy  

NASA Technical Reports Server (NTRS)

A crucial task of Mars surface science is to determine past environmental conditions, especially aqueous environments and their nature. Identification of mineral alteration by water is one way to do this. Recent work interprets TES spectra as indicating altered basalt on Mars. Olivine, a primary basaltic mineral, is easily altered by aqueous solutions. Alteration assemblages of olivine may be specific to deuteric, hydrothermal, surface water, or metamorphic environments. Raman spectra are produced by molecular vibrations and provide direct means for studying and identifying alteration products. Here, we present a combined study of changes in the chemical composition and Raman spectra of an olivine as it alters to iddingsite. Iddingsite is found in some SNC meteorites and is presumably present on Mars. The term 'iddingsite' has been used as a catch-all term to describe reddish alteration products of olivine, although some authors ascribe a narrower definition: an angstrom-scale intergrowth of goethite and smectite (presumably saponite) formed in an oxidizing and fluid-rich environment. Alteration conserves Fe (albeit oxidized) but requires addition of Al and H2O and removal of Mg and Si. The smectite that forms may be removed by continued alteration. Dehydration of the goethite forms hematite. Our purpose is to study the mineral assemblage, determine the structural and chemical variability of the components with respect to the degree of alteration, and to find spectral indicators of alteration that will be useful during in-situ analyses on Mars.

Kuebler, K. E.; Wang, Alian; Haskin, L. A.; Jolliff, B. L.

2003-01-01

174

Influence of the olivine additive fineness on the oxidation of magnetite pellets  

Microsoft Academic Search

Olivine is used as an additive in Luossavaara–Kiirunavaara AB (LKAB) blast furnace pellets. The LKAB iron ore is magnetite which oxidizes to hematite during the sintering process. Olivine retards the oxidation of magnetite pellets if the threshold temperature of magnesioferrite formation is exceeded.In this study, we have developed a thermogravimetric measuring method to study the relationship between the olivine reactivity

S. P. E. Forsmo; A. Hägglund

2003-01-01

175

Olivine in kimberlites: metasomatism of the deep lithospheric mantle  

NASA Astrophysics Data System (ADS)

Most kimberlites contain abundant mantle microxenoliths (nodules) and xenocrysts, mainly composed of olivine. We present here a geochemical and microstructural study of nodules from well-preserved type-I kimberlites from Kangamiut region in Greenland, the sequel of a preliminary study of Arndt et al. (2010). A striking feature of these and many other kimberlites is the wide range of olivine composition (Fo83 to Fo94) from nodule to nodule in a single kimberlite sample, contrasting with the olivine homogeneity within a single nodule (variation of less than 0.5 mol. %). We defined three chemical zones within normally zoned nodules based on Fo and Ni variations. Xenocrystic cores have high and constant Fo and Ni contents. Outer rims crystallized from the kimberlitic magma have constant Fo content (Fo88) coupled with significant decrease in Ni content (from 2500 to 500 ppm). Transition zones between cores and rims, along grain boundaries and along fluid inclusion trails have variable Fo content (Fo93 to Fo88) but roughly constant Ni content (from 3000 to 25000 ppm) and their composition mimics that defined by the nodules. Microstructural study of transition zones associated with curvilinear grain boundaries suggests these zones are produced during fluid-assisted plastic deformation. We propose that the transition zones formed during reaction of mantle peridotite with CO2-rich fluid, a process that removes the pyroxene and garnet components. The compositional variations of the transition zones monitor at the fine scale the processes that produce the chemical variability of olivine from nodule to nodule. We propose that the range of olivine composition records the position of sample relative to fluid-rich zones, grain boundaries for transition zones and larger conduits for broader scale variations registered in the nodules. This conclusion implies that metasomatic processes that produced the range of olivine composition and removed pyroxene and garnet from the initial peridotite occurred within the lithospheric mantle and not within the kimberlite magma during it ascent toward the surface. Arndt, N. T.; Guitreau, M.; Boullier, A. M.; Le Roex, A.; Tommasi, A.; Cordier, P. & Sobolev, A. V. (2010): Olivine, and the origin of kimberlite. Journal of Petrology, 51, 573-602.

Cordier, Carole; Sauzeat, Lucie; Arndt, Nicholas; Boullier, Anne-Marie

2014-05-01

176

The effect of mineral paragenesis on Al diffusion in olivine  

NASA Astrophysics Data System (ADS)

Al is the most abundant trivalent impurity of olivine and is particularly important because its concentration in olivine is temperature dependant, and it therefore has potential as a geothermometer (Wan, et al. 2008). Furthermore recent studies show that the incorporation of water into the olivine lattice is affected by the presents of trivalent cations such as Al3+ (Berry, et al. 2007; Hauri, et al. 2006). The Al distribution in olivines from volcanic rocks is often zoned and mantle olivines may also show an inhomogeneous distribution of Al, whereas the majority of other trace elements homogenized by diffusion (Mallmann, et al. 2009; McKibbin, et al.). However, there are no quantitative experimental data for Al diffusion in olivine, probably because the combination of low concentration rate and low diffusion rate make measurement difficult. We investigated the effect of silica activity on the diffusion rate of Al in forsterite at varying temperatures using solid-state buffer assemblages. Our study aimed to quantify the effect of major cation activities on the diffusion and concentration of Al in forsterite and also provide insights into the mechanism of Al substitution into the olivine lattice. The activities of SiO2, MgO and Al2O3 were buffered in each experiment by four different mineral associations: forsterite + periclase + spinel (fo+per+sp); forsterite + spinel + sapphirine (fo+sp+spr); forsterite + sapphirine + cordierite (fo+spr+cor); forsterite + cordierite + enstatite (fo+cor+en). Iron oxide in proportion of FeO/(FeO+MgO) = 0.1 was added to mixtures for San Carlos olivine experiments. Diffusion experiments were performed at the one-atmosphere vertical tube furnaces modified to control the fO2 by CO-CO2 gas mixing or in a box furnace in air for 10 - 28 days at temperatures from 1100 to 1500oC and logfO2 -0.7 and -5.7. The experiment with the San Carlos olivine was performed at 1300oC and at logfO2 = -5.7. In order to obtain equilibrium concentrations of the point defects we performed some experiments with pre-annealing. Diffusion profiles were measured by LA-ICP-MS in a traverse mode. The Al content of forsterite decreases with temperature dependence, increasing the potential of Al in olivine as a geothermometer. We obtain the activation energy of 379 kJ/mol for the high aSiO2 experiments, which is close within error of the value of 364 kJ/mol for the low aSiO2 experiments implying a common diffusion mechanism. The pre-exponential factor, however, increases by 5 orders of magnitude from low aSiO2 (fo+per+sp buffer) to high aSiO2 (fo+cor+en buffer). The much higher diffusivity at high aSiO2 indicates that Al diffusion occurs through octahedral cation site vacancies.

Zhukova, Irina; O'Neill, Hugh; Capbell, Ian

2014-05-01

177

Geoengineering potential of artificially enhanced silicate weathering of olivine.  

PubMed

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 CO(2) 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. PMID:21059941

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

2010-11-23

178

The geoengineering potential of artificially enhanced silicate weathering of olivine  

NASA Astrophysics Data System (ADS)

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, because it influences the global climate via the carbon cycle. We here show the consequences of this technique for the chemistry of the surface ocean at rates necessary for geoengineering. We calculate that olivine dissolution has the potential to sequestrate up to one Pg C yr-1 directly, if olivine is distributed as fine powder over land areas of the humid tropics. The carbon sequestration potential 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 C yr-1. 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 to 5 Pg C yr-1 for the 21st century by this technique. At maximum this technique would reduce global warming by 1 K and counteract ocean acidification by a rise in surface ocean pH by 0.1 in the year 2100.

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

2010-05-01

179

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. PMID:21059941

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

2010-01-01

180

High-temperature elasticity of iron-bearing olivines  

NASA Astrophysics Data System (ADS)

The first high-temperature data on the nine adiabatic elastic moduli for iron-bearing olivine are reported. These measurements are on two single-crystal specimens of natural olivine at ambient pressure and from room temperature to a maximum of 1500 K. The two specimens contain 8 and 9 modal percent fayalite, which required the oxygen fugacity be controlled at high temperature to preserve their chemical stability. The rectangular parallelepiped resonance apparatus was adapted to buffer the specimens from the atmosphere with a mixture of CO and CO2 gas. A small increase (˜1-2 GPa) in the adiabatic bulk modulus of each specimen, over that of end-member forsterite, was found. The data are high quality to extreme temperatures, with good agreement found when comparing the temperature derivatives of the elastic moduli of the two specimens. Neither specimen exhibits measurable nonlinear temperature dependence in the computed isotropic bulk and shear moduli, which is in contrast to published forsterite data. The temperature derivatives of the isotropic bulk modulus KS are (-1.69, -1.80) × 10-2 GPa K-1 for the two olivine specimens, and the shear modulus G derivatives are (-1.38, -1.36) × 10-2 GPa K-1. These derivatives are only slightly larger in magnitude than |(?KS/?T)P| = 1.56 × 10-2 and |(?G/?T)P| = 1.30 × 10-2 GPa K-1 found previously for iron-bearing olivine over a very small temperature range. There are also no significant differences between the temperature derivatives found here and the average derivatives of end-member forsterite from data retrieved over a slightly larger temperature range. Several dimensionless parameters have been calculated from these results and are discussed in view of systematics which bear on high-pressure phases in Earth's transition zone. One result from these systematics related to the seismic velocities in the Earth, and especially the shear wave velocities, is that an olivine content of less than 50% is implied at the 400-km discontinuity if Earth's upper mantle is isochemical. Furthermore, the substitution of almost 10% iron for magnesium at the forsterite end of the olivine solid solution series has little effect on the dimensionless parameters or on the temperature derivatives of the elastic moduli at high temperature.

Isaak, Donald G.

1992-02-01

181

Olivine separates from Murchison and Cold Bokkeveld - Particle tracks and noble gases  

NASA Technical Reports Server (NTRS)

Olivine separates from Murchison and Cold Bokkeveld were analyzed for particle tracks and noble gases. The matrix remaining after olivine separation was also analyzed for noble gases. The olivines from both meteorites have comparable fractions of solar-flare-irradiated grains, but the highest track densities in Murchison are an order of magnitude greater than those in Cold Bokkeveld. Solar Ne content in Murchison olivines follows this trend, being at least an order of magnitude higher than that in Cold Bokkeveld. Track gradients in Cold Bokkeveld olivines are flatter than those in Murchison or recently exposed lunar crystals. Relative to the matrix, olivine separates in both meteorites have small enrichments at the heavy and light Xe isotopes and smaller Ar-36/Ar-38 ratios. These noble-gas effects may be related to a chromite impurity in the olivine separates.

Macdougall, J. D.; Phinney, D.

1977-01-01

182

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

183

The solubility of olivine in basaltic liquids - An ionic model  

NASA Technical Reports Server (NTRS)

A model is presented which enables the temperature at which olivine is in equilibrium with any alkali-depleted basaltic compound to be calculated to within + or - 30 C. It is noted that the error increases substantially when applied to terrestrial basalts which contain several weight percent alkalis. In addition the model predicts and quantifies the reduced activity of SiO4(4-) monomers due to increasing SiO2 concentrations in the melt. It is shown that the coordination of alumina in melts which precipitate olivine only appears to be dominantly octahedral, while titanium acts as a polmerizing agent by interconnecting previously isolated SiO4(4-) monomers. It is concluded that the model is sufficiently sensitive to show that there are small repulsive forces between Mg(2+) and calcium ions which are in association with normative diopside in the melt.

Herzberg, C. T.

1979-01-01

184

First-principles studies of native defects in olivine phosphates  

NASA Astrophysics Data System (ADS)

Olivine phosphates LiMPO4 (M=Mn, Fe, Co, Ni) are promising candidates for rechargeable Li-ion battery electrodes because of their energy storage capacity and electrochemical and thermal stability. It is known that native defects have strong effects on the performance of olivine phosphates. Yet, the formation and migration of these defects are not fully understood, and we expect that once such understanding has been established, one can envisage a solution for improving the materials' performance. In this talk, we present our first-principles density-functional theory studies of native point defects and defect complexes in LiMPO4, and discuss the implications of these defects on the performance of the materials. Our results also provide guidelines for obtaining different native defects in experiments.

Hoang, Khang; Johannes, Michelle

2011-03-01

185

Carbonation Reaction Layer Study of San Carlos Olivine  

Microsoft Academic Search

Increasing CO2 levels in the earth's atmosphere due to combustion processes are leading researchers to develop several methods to store sequestered CO_2. Oceans, subsurface reservoirs such as depleted oil fields, and terrestrial carbon pools have all been suggested. Our research focuses on mineral sequestration of CO_2. Olivine (e.g., forsterite, Mg_2SiO_4), a widely available mineral, reacts with CO2 to form magnesite

Ryan Nunez; Ray Carpenter; Kim Youngchul; Michael McKelvy; Andrew Chizmeshya; Dierdra Gormley

2004-01-01

186

Diffusion creep of dry, melt-free olivine  

Microsoft Academic Search

Deformation experiments were conducted on fine-grained (3–6 ?m), fully synthetic Fo90 olivine aggregates in a gas-medium apparatus at 300 MPa confining pressure and temperatures of 1150–1360°C. The strain rates of the solution-gelation-derived and therefore genuinely melt-free, dry samples are about two orders of magnitude lower than the strain rates for nominally melt-free aggregates at the same pressure and temperature conditions

Ulrich H. Faul; Ian Jackson

2007-01-01

187

Chemical frost weathering of olivine: Experimental study and implications  

NASA Technical Reports Server (NTRS)

New experimental results are reported on the frost weathering of olivine. After first weathering, a decrease in Fe sup 2(+)M(2) absorption bands were noted. This decrease is related to the protonation of O(+) in the mineral. It is contented that this reaction may result in the regolith storage of 100 to 1000 m of H(sub 2) over the history of Mars.

Harris, S. L.; Huguenin, R. L.

1987-01-01

188

A re-evaluation of the olivine-spinel geothermometer  

Microsoft Academic Search

The Irvine olivine-spinel geothermometer, as formulated by Jackson (1969), appears to yield magmatic temperatures when applied\\u000a to plutonic rocks such as the Stillwater Complex but Evans and Wright (1972) have demonstrated that it gives temperatures\\u000a in excess of 2,000 ° C when applied to volcanic assemblages. A re-evaluation of the geothermometer has shown that more realistic\\u000a temperatures can be obtained

Peter L. Roeder; Ian H. Campbell; Heather E. Jamieson

1979-01-01

189

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

190

Performance improvement of lithium manganese phosphate by controllable morphology tailoring with Acid-engaged nano engineering.  

PubMed

Olivine-type lithium manganese phosphate (LiMnPO4) has been considered as a promising cathode for next-generation Li-ion batteries. Preparation of high-performance LiMnPO4 still remains a great challenge because of its intrinsically low Li-ion/electronic conductivity. In this work, significant performance enhancement of LiMnPO4 has been realized by a controllable acid-engaged morphology tailoring from large spindles into small plates. We find that acidity plays a critical role in altering the morphology of the LiMnPO4 crystals. We also find that size decrease and plate-like morphology are beneficial for the performance improvement of LiMnPO4. Among the plate-like samples, the one with the smallest size shows the best electrochemical performance. After carbon coating, it can deliver high discharge capacities of 104.0 mAh g(-1) at 10 C and 85.0 mAh g(-1) at 20 C. After 200 cycles at 1 C, it can still maintain a high discharge capacity of 106.4 mAh g(-1), showing attractive applications in high-power and high-energy Li-ion batteries. PMID:25559416

Guo, Hui; Wu, Chunyang; Liao, Longhuan; Xie, Jian; Zhang, Shichao; Zhu, Peiyi; Cao, Gaoshao; Zhao, Xinbing

2015-01-20

191

Fe/Mn in olivine of carbonaceous meteorites  

NASA Technical Reports Server (NTRS)

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 these earliest conditions. Initial Fe/Mn in cores of isolated, euhedral forsterite in both C2 and C3 meteorites ranges from 25 to 35 but differs at grain edge. Murchison (C2) forsterites show Fe/Mn approaching 1.0 at the grain edge while Ornans Fe/Mn is near 60 at grain edge. These values are lower than the matrix Fe/Mn for both meteorites and the distinct difference in zoning profile indicates different processes operating during and after grain growth. The Fe/Mn of bulk samples from a particular source such as the Moon is nearly constant. Individual samples show variation suggesting that there is some fractionation of Mn from Fe. Minerals have their individual ranges of Fe/Mn which has been used to recognize different types of olivine within one meteorite. Extreme values of Fe/Mn below 1.0 occur in forsterite from some IDP's, UOC matrix, and C1 meteorites. There are apparently no detailed studies of Fe/Mn variation within single olivine grains. Forsterite grains in C2 and C3 carbonaceous chondrites show complex zoning, and the nearly pure forsterites (Fo greater than approximately 99.5) have high levels of some minor elements including Ti, Al, V, and Sc. There is disagreement on the original source of these grains and both chondrule and vapor growth have been proposed. In addition, there is clear evidence that diffusion has affected the outer margins but in some cases the whole grain. Within the cores, the FeO range is limited, and if growing under constant conditions, the Fe/Mn should be near constant as there is little fractionation of Mn from Fe by forsterite. Additionally, there are apparently no co-crystallizing phases as evidenced by a lack of common inclusions in the forsterites. These observations are now followed by analyses of isolated olivine grains in C2 and C3 meteorites.

Steele, Ian M.

1993-01-01

192

A 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  

NASA Technical Reports Server (NTRS)

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 [1]. That paper was followed by several on QUE94201 melt composition and specifically on Cr, V, and Eu partitioning between pyroxene and melt [2-5]. This paper represents the continuation of our examination of the partitioning of multivalent V between olivine, spinel, and melt in martian olivine-phyric basalts of Y980459 composition [6, 7]. Here we introduce a new, potentially powerful oxybarometer, V partitioning between spinel and olivine, which can be used when no melt is preserved in the meteorite. The bulk composition of QUE94201 was ideal for our study of martian pyroxene-phyric basalts and specifically the partitioning between pyroxene-melt for Cr, V, and Eu. Likewise, bulk composition Y980459 is ideal for the study of martian olivine-phyric basalts and specifically for olivine-melt, spinel-melt, and spinel-olivine partitioning of V as a function of oxygen fugacity.

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

2013-01-01

193

Annealing of deformed olivine single-crystals under 'dry' conditions  

NASA Astrophysics Data System (ADS)

Knowledge of rheological properties of Earth's materials is essential to understand geological processes. Open questions are the water content and crystallographic orientation dependences of dislocation creep rate, because the dominant slip system changes with increasing water content, which suggest different dislocations have different water content dependence. This project focuses on olivine, which is the most abundant mineral of the upper mantle. It is also considered to be the weakest phase and hence should control the rheology of the upper mantle. Several slip systems were reported for olivine, which are [100](010), [001](010), [001](100) and [100](001), each of which appear under different water content and stress conditions [1]. For this purpose we started to obtain data for 'dry' conditions, providing basic knowledge to understand the effect of water. Variation in dislocation creep rate according to change in physical conditions can be estimated by dislocation recovery experiments [2]. In this technique, deformed crystals are annealed, in which the dislocation density is expected to decrease due to coalescence of two dislocations. Dislocation densities are measured before and after the annealing. Dislocation mobility, which should be directly proportional to the dislocation creep rate, is estimated based on the change in dislocation density and duration of annealing. This technique has significant advantages partly because informations of strain rate and deviatoric stress, which are difficult to measure, are unnecessary, and partly because dislocation annealing is conducted under quasi-hydrostatic conditions, which allows wide ranges of P and T conditions. The first step of the experiments is to deform a single crystal of olivine. For this purpose, we developed an assembly, which deforms a single crystal in simple-shear geometry and prevent breakage, sub-grain formation and recrystallization of the crystal. Olivine single-crystals were placed in the high-pressure assembly so that a particular slip system is activated. The assemblies were compressed to 3 GPa. The shear deformation was conducted at 1600 K. EBSD measurements indicate that the recovered crystals are single crystals and sub-grain formation did not occur in most cases. The second step is to anneal the samples under the same P-T conditions as those of the deformation experiments. Annealing experiments are also performed at ambient pressures at 1600 K. Dislocation density was measured by means of the oxidation decoration technique [3]. The samples were firstly polished and then oxidized at 1200 K for 50 min. The dislocations are preferably oxidized, so that presence of dislocation can be observed using SEM. First Results indicate that the dislocation density decreased by annealing by 1/4 with an annealing period of 10 h for dislocations with b = [001]. References [1] H. Jung and S. I. Karato. Water-induced fabric transitions in olivine. Science, 293(5534):1460-1463, 2001. [2] S. I. Karato, D. C. Rubie, and H. Yan. Dislocation recovery in olivine under deep upper mantle conditions: Implications for creep and diffusion. Journal of Geophysical Research, 98(B6):9761-9768, 1993. [3] D. L. Kohlstedt, C. Goetze, W. B. Durham, and J. V. Sande. New technique for decorating dislocations in olivine. Science, 191(4231):1045-1046, March 1976.

Blaha, Stephan; Katsura, Tomoo

2013-04-01

194

Solubility of Helium in Olivine at 1 Atmosphere  

NASA Astrophysics Data System (ADS)

We have measured the solubility of He in olivine at 1 atm. Previous measurements of noble gas solubility in mantle minerals have found mineral/melt partition coefficients (D) that are higher [1;2] or close to [3] the D values of U and Th in the mantle. In contrast, geochemical systematics suggest that DHe is lower than DU and DTh. Our experiments were specifically designed to avoid gas trapped in melt pockets or between sintered grains, which may have affected previous studies [1;2]. The starting materials are gem quality San Carlos olivine and synthetic pure forsterite. These materials were examined before and after the experiments for inclusions and bubbles using optical, scanning electron and scanning transmission electron microscopic techniques. No bubbles were found. The primary experiments were performed on cm size grains to avoid trapping of gas in sintered powders. The experiments were run for 17-21 days at 1350° C, in crucibles made from large San Carlos olivine crystals, in an atmosphere of 50% He and 50% a mix of CO2 and H2 (to control fO2 at NNO and QFM). At no time was the olivine in contact with a melt phase. To examine the effects of powder sintering, experiments that span a range of smaller grain sizes (100-1000 microns) were also performed. He concentrations in the olivines were measured by noble gas mass spectrometry using sequential in vacuo crushing followed by melting of the powders. The experimental results are consistent: 8.3(+/-2.6) e-7 cc STP He/g are released by crushing and 6.2(+/-1.3) e-7 cc He STP/g are released by melting. Over 50% of the total gas is released by crushing. Powdered samples release unusually high amounts of gas on the first crush step (interpreted to be trapped between grains), but subsequently follow the same release pattern as the unpowdered samples and yield the same solubility values (excluding the first step). The consistency of the results over a range of compositions, grain sizes and fO2 conditions, and our careful examination of the experimental materials indicate that the gas released during crushing is not trapped in bubbles or inclusions, but is loosely bound within the crystal lattice. Where it resides in the olivine crystal structure is not clear. Using only the gas released by melting, along with published solubilities of He in basaltic melts [4], the ol/melt DHe is 0.003(+/-0.001) at 1 atm. This is most likely an upper limit because the crushing experiments may not have completely eliminated the loosely bound helium. If the gas from both the crushing and melting steps are combined, the apparent DHe is 0.006(+/-0.001). We caution against extrapolating these preliminary values to mantle melting conditions until the location of He in olivine is identified and the effects of pressure and temperature are quantified. [1] Broadhurst et al. (1990) GCA 54: 299-309 [2] Hiyagon and Ozima (1986) GCA 50: 2045-2057 [3] Brooker et al. (2003) Nature 423: 738-741 [4] Jambon et al. (1986) GCA 50: 401-408

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

2004-12-01

195

Nepheline and sodalite in a barred olivine chondrule from the Allende meteorite  

NASA Technical Reports Server (NTRS)

The discovery of nepheline and sodalite in association with glass in a barred olivine chondrule from the Allende C3V meteorite is reported, and the possible origin of the minerals is discussed. Scanning electron microscope/energy dispersive analysis indicates that the major minerals of the chondrule are olivine, bronzite and chromite, with olivine bars separated by glass of nearly pure plagioclase composition. The olivine is observed to have a composition richer in Fe than that predicted from olivine-liquid equilibria, indicating, along with the presence of plagioclase glass and small amounts of subcalcic diopside, the nonequilibrium crystallization of the barred olivine chondrule. The textural features of the chondrule are consistent with a liquid origin for nepheline and sodalite from the chondrule-forming liquid under nonequilibrium conditions.

Lumpkin, G. R.

1980-01-01

196

Producing Ni-rich olivine phenocrysts by mixing partial melts of eclogite and peridotite: an alternative to an olivine-free source for Hawaiian shield basalts  

NASA Astrophysics Data System (ADS)

It has been posited that presence of unusually Ni-rich (2500-4000 ppm) magnesian olivine phenocrysts in SiO2-enriched Hawaiian shield-building basalts, most notably the Koolau lavas, is inconsistent with a deep, olivine-bearing source rock. Instead, Sobolev et al. (2005) proposed that these lavas are generated by a multi- stage process in which partial melts of eclogite react with peridotite within the plume to form an olivine-free source rock with high Ni concentration. As the plume continues to ascend, partial melts of this "hybrid" pyroxenite mix with peridotite melts to produce SiO2- enriched Hawaiian shield-building lavas that crystallize high-Ni olivine. This model has also been used to argue for significant amounts of "hybrid" pyroxenite in the source regions of lavas from other ocean islands, continental basalts, and even MORB, implying that the upper mantle is highly heterogeneous (Sobolev et al., 2007). New experimental results demonstrate that Ni-rich magnesian olivine crystallizes from mixtures of peridotite partial melt and Ni-poor eclogite partial melt that have equilibrated with mantle olivine. This occurs because the concentration of Ni decreases linearly as eclogite partial melt is added to peridotite partial melt, whereas changing major element composition of the mixed melts causes DNi to increase hyperbolically. Experiments were conducted in which either (1) siliceous partial melt of eclogite or (2) primitive basalt was equilibrated with San Carlos olivines at 1 bar and 1201-1350°C. Experimental results demonstrate that eclogite partial melts in equilibrium with mantle olivine retain their high SiO2, low FeO and MgO characteristics. Theoretical modeling calibrated from these experimental results suggest that reaction of siliceous eclogite melt with mantle olivine at low pressure produces a melt containing ~300 ppm Ni. Despite its low Ni content, mixing of this melt with peridotite partial melt produces a high SiO2 melt that crystallizes Ni-rich, magnesian olivine. The dependence of olivine-melt partition coefficients on melt composition also explains the enrichment or depletion of other minor element in Koolau olivines (e.g., Ca and Mn). Our results obviate the need for a multi-step melt generation process in which reaction with large amounts of siliceous eclogite partial melt exhausts olivine from portions of mantle peridotite within the Hawaiian plume. As a result, the amount of eclogite required to explain the composition of the Koolau lavas is greatly reduced. Reference Sobolev, A.V. et al., (2005), Nature, 434, 590-597 Sobolev, A.V. et al., (2007), Science, 316, 412-417

Wang, Z.; Gaetani, G.

2007-12-01

197

Coronas in olivine gabbros and iron ores from Susimäki and Riuttamaa, Finland  

Microsoft Academic Search

Coronas have been studied by petrographie and microprobe techniques in metamorphosed olivine gabbros and associated iron ores\\u000a from Susimäki and Riuttamaa in Southwest Finland. Three types of coronas are distinguished occurring between the following\\u000a primary minerals: (1) olivine-plagioclase, (2) opaque oxides-plagioclase, (3) opaque oxides-clinopy-roxene. Secondary corona\\u000a minerals are, in order of decreasing abundance, hornblende, orthopyroxene, spinel, olivine, ilmenite, and magnetite.

Hans van Lamoen

1979-01-01

198

[Study on the FTIR spectra of OH in olivines from mengyin kimberlite].  

PubMed

The results of FTIR spectra study of OH in olivines from Mengyin kimberlite show that there are more than 60 OH absorption peaks in the range of 3800-3000 cm(-1). We identified four major spectral features in the OH absorption bands of kimberlitic olivines. One is with nuOH in the range of 3800-3700 cm(-1), which is caused by the vapour of the room circumstance, and can not be regarded as intrinsic or non-intrinsic nuOH of the olivines. Another one is with nuOH in the range of 3710-3620 cm(-1), which belongs to three "water"-bearing minerals including serpentine, talc and Mg-bearing amphiboles, which is the non-intrinsic nuOH of the olivines. There is the possibility that H in hydrous minerals mainly entered into olivines during post-emplacement processes of the kimberlite magma. The third one is with nuOH in the range of 3620-3425 cm(-1), which originated from H occupying the Si-defect in the olivine structure, forming humite-like defects, and/or the defects that H occupies (Mg,Fe)-depletion, which is certainly attributed to the intrinsic nuOH of the olivines. In this case, H possibly entered into olivines following its immersion in the high temperature and rich fluid kimberlite magma in the mantle circumstance. The last one is with nuOH in the range of 3425-3000 cm(-1). In this area, nuOH is assigned to fluid inclusions of the olivines, and is the non-intrinsic nuOH of olivines. Fluid inclusions can enter into the olivines either during post-emplacement processes of the kimberlite magma or during the periods that olivines were formed in the mantle. PMID:24369634

Ai, Qun; Yang, Zhi-jun; Zeng, Xiang-qing; Zheng, Yun-long; Hu, Piao-ye

2013-09-01

199

Magnetic properties of natural and synthetic olivines: high-field measurements  

Microsoft Academic Search

Olivine [(Fex, Mg1-x)2 SiO4] is an orthosilicate solid solution between fayalite [Fe2 SiO4] and forsterite [Mg2 SiO4]. Olivine is a major constituent of the Earth mantle that is abundant in oceanic and continental peridotites and mantle xenoliths. The magnetic properties of olivines have been previously investigated using gem quality natural crystals known as peridots (Zabargad) or using laboratory grown synthetic

E. C. Ferre; F. Martin-Hernandez

2004-01-01

200

Extreme Ni Concentrations in High Forsterite Olivine from a Cascade Forearc Basalt  

NASA Astrophysics Data System (ADS)

We have evaluated olivine phenocrysts and host glass from a basalt lava flow and associated scoria cone in the Quartzville mining district located on the western forearc margin of the Oregon Cascades. Both lavas and scoria are contemporaneous determined through detailed field mapping, and they share similar petrological and geochemical characteristics. Ar-Ar dating indicates a lava eruption age of 82.3±3.1 ka. Minor clinopyroxene is also present as a phenocryst phase while the groundmass contains apatite, magnetite and plagioclase. Abundant Cr-spinel and lesser magnetite occur as mineral inclusions within olivine phenocrysts and olivine-hosted melt inclusions. Olivine compositions vary from Fo88 to Fo94, and are accompanied by Ni concentrations that range from 0.06 to 0.63 wt%, but average ~0.4 wt%. Ni abundances are positively correlated with olivine composition from Fo88-92. In this compositional range, olivines from the lavas tend to have higher Fo contents and consequently higher Ni concentrations, which is consistent with the idea that the scoria is slightly more evolved than the basaltic melt. At forsterite values above Fo92, however, Ni concentrations decrease to concentrations comparable to Fo88-92 olivines. Fo92-94 olivine compositions are predominantly located at the rims of the olivine phenocrysts. Olivine-hosted melt inclusion compositions were also determined to provide important constraints on volatiles and oxygen fugacity of the magma at time of entrapment. Oxygen fugacity was determined in melt inclusions through sulfur speciation measurements and ranged from ?FMQ + 1.9 log units. This high fO2 is corroborated by oxygen fugacity calculations from spinel-olivine pairs. Additionally, oxygen isotope measurement on an olivine separate records a typical mantle value of ?18O = 5.6‰. Prior studies have identified high Ni olivine in calc-alkaline and highly potassic lavas and have proposed that these magmas are not derived from a peridotite source but rather a pyroxenite source. Additionally, the high Fo and Ni concentrations may be a function of the high oxygen fugacities as recorded by olivine-hosted melt inclusions and spinel-olivine pairs. In the present study we apply detailed petrography and geochemistry of mineral phases and glass to better constrain the source composition and magma evolution for this magmatic system. Our plan is to test our observations against the current hypothesis that high-Ni olivines can be produced from a progressively hybridized peridotite or pyroxenite source (Straub et al., 2008).

Tepley, F. J.; Rowe, M. C.

2009-12-01

201

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

202

Magmatic history and parental melt composition of olivine-phyric shergottite LAR 06319: Importance of magmatic degassing and olivine antecrysts in Martian magmatism  

NASA Astrophysics Data System (ADS)

Several olivine-phyric shergottites contain enough olivine that they could conceivably represent the products of closed-system crystallization of primary melts derived from partial melting of the Martian mantle. Larkman Nunatak (LAR) 06319 has been suggested to represent a close approach to a Martian primary liquid composition based on approximate equilibrium between its olivine and groundmass. To better understand the olivine-melt relationship and the evolution of this meteorite, we report the results of new petrographic and chemical analyses. We find that olivine megacryst cores are generally not in equilibrium with the groundmass, but rather have been homogenized by diffusion to Mg# 72. We have identified two unique grain types: an olivine glomerocryst and an olivine grain preserving a primary magmatic boundary that constrains the time scale of eruption to be on the order of hours. We also report the presence of trace oxide phases and phosphate compositions that suggest that the melt contained approximately 1.1% H2O and lost volatiles during cooling, also associated with an increase in oxygen fugacity upon degassing. We additionally report in situ rare earth element measurements of the various mineral phases in LAR 06319. Based on these reported trace element abundances, we estimate the oxygen fugacity in the LAR 06319 parent melt early in its crystallization sequence (i.e., at the time of crystallization of the low-Ca and high-Ca pyroxenes), the rare earth element composition of the parent melt, and those of melts in equilibrium with later formed phases. We suggest that LAR 06319 represents the product of closed-system crystallization within a shallow magma chamber, with additional olivine accumulated from a cumulate pile. We infer that the olivine megacrysts are antecrysts, derived from a single magma chamber, but not directly related to the host magma, and suggest that mixing of antecrysts within magma chambers may be a common process in Martian magmatic systems.

Balta, J. Brian; Sanborn, Matthew; McSween, Harry Y.; Wadhwa, Meenakshi

2013-08-01

203

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

204

Olivine-rich exposures in the South Pole-Aitken Basin  

NASA Astrophysics Data System (ADS)

The distribution and the geological context of the olivine-rich exposures in the South Pole-Aitken (SPA) Basin on the Moon were investigated based on the spectral data obtained from the Spectral Profiler (SP) and Multiband Imager (MI) onboard the Japanese lunar explorer Kaguya/SELENE. The olivine-rich exposures are found only in the peak rings or central peaks of the Schrödinger basin and Zeeman crater, which are located in the outer region of the SPA Basin and not in the center region. On a localized scale, the olivine-rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings. Another observational finding is the co-existence of olivine-rich and plagioclase-rich materials on a kilometer scale spanning most of the olivine-rich sites in the Schrödinger basin. Pyroxene-rich materials are found in fresh craters outside the peak rings or the central peaks with olivine-rich materials. Based on these results, the following scenario are proposed: (1) the impact to form the SPA Basin melted a large amount of the lunar upper mantle and crust, and distributed the melted materials to the outer region; (2) local differentiation of melted materials hid the olivine-rich materials in the center region of the SPA Basin; (3) later impacts that formed the Schrödinger and Zeeman craters excavated and exposed the olivine-rich materials to the surface again; and (4) space weathering and regolith gardening obscured the olivine-rich spectra at the exposure sites, but recent, small scale impacts or landslides on the sloped wall exposed fresh olivine-rich materials, allowing the identification of the olivine-rich exposures by spectral remote-sensing. This suggests that several, different scale events play an important role in forming the surface distributions of originally deep-seated materials on the Moon, as well as on other planetary bodies.

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

2012-03-01

205

Morphology and surface features of olivine in kimberlite: implications for ascent processes  

NASA Astrophysics Data System (ADS)

Most kimberlite rocks contain large proportions of ellipsoidal-shaped xenocrystic olivine grains that are derived mainly from disaggregation of peridotite. Here, we describe the shapes, sizes and surfaces of olivine grains recovered from kimberlite lavas erupted from the Quaternary Igwisi Hills volcano, Tanzania. The Igwisi Hills kimberlitic olivine grains are compared to phenocrystic olivine, liberated from picritic lavas, and mantle olivine, liberated from a fresh peridotite xenolith. Image analysis, scanning electron microscopy imagery and laser microscopy reveal significant differences in the morphologies and surface features of the three crystal populations. The kimberlitic olivine grains form smooth, rounded to ellipsoidal shapes and have rough flaky micro-surfaces that are populated by impact pits. Mantle olivine grains are characterised by flaked surfaces and indented shapes consistent with growth as a crystal aggregate. Phenocrystic olivine exhibit faceted, smooth-surfaced crystal faces. We suggest that the unique shape and surface properties of the Igwisi Hills kimberlitic olivine grains are products of the transport processes attending kimberlite ascent from mantle source to surface. We infer that the unique shapes and surfaces of kimberlitic olivine grains result from three distinct mechanical processes attending their rapid transport through the thick cratonic mantle lithosphere: (1) penetrative flaking from micro-tensile failure induced by rapid decompression; (2) sustained abrasion and attrition driven by particle-particle collisions between grains within a turbulent, volatile-rich flow regime; and (3) higher-energy particle-particle collisions producing impact cavities superimposed on decompression structures. The combination of these processes during the rapid ascent of kimberlite magmas is responsible for the distinctive ellipsoidal shape of olivine xenocrysts found in kimberlites worldwide.

Jones, T. J.; Russell, J. K.; Porritt, L. A.; Brown, R. J.

2014-05-01

206

Temperature-dependent Infrared Optical Constants of Olivine and Enstatite  

NASA Astrophysics Data System (ADS)

Since the Infrared Space Observatory (ISO) mission, it has become clear that dust in circumstellar disks and outflows consists partly of crystalline silicates of pyroxene and olivine type. An exact mineralogical analysis of the dust infrared emission spectra relies on laboratory spectra, which, however, have been mostly measured at room temperature so far. Given that infrared spectral features depend on the thermal excitation of the crystal's vibrational modes, laboratory spectra measured at various (low and high) temperatures, corresponding to the thermal conditions at different distances from the star, can improve the accuracy of such analyses considerably. We have measured the complex refractive index in a temperature range of 10-973 K for one mineral of each of those types of silicate, i.e., for an olivine and an enstatite of typical (terrestrial) composition. Thus, our data extend the temperature range of previous data to higher values and the compositional range to higher iron contents. We analyze the temperature dependence of oscillator frequencies and damping parameters governing the spectral characteristics of the bands and calculate absorption cross-sectional spectra that can be compared with astronomical emission spectra. We demonstrate the usefulness of our new data by comparing spectra calculated for a 100 K dust temperature with the ISO SWS spectrum of IRAS 09425-6040.

Zeidler, S.; Mutschke, H.; Posch, Th.

2015-01-01

207

Annealing behaviour of ion tracks in olivine, apatite and britholite  

NASA Astrophysics Data System (ADS)

Ion tracks were created in olivine from San Carlos, Arizona (95% Mg2SiO4), apatite (Ca5(PO4)3(F,Cl,O)) from Durango, Mexico, and synthetic silicates with the apatite structure: Nd8Sr2(SiO4)6O2 and Nd8Ca2(SiO4)6O2 using 1.6 and 2.2 GeV Au ions. The morphology and annealing behaviour of the tracks were investigated by means of synchrotron based small angle X-ray scattering in combination with ex situ annealing. Tracks in olivine annealed above ?400 °C undergo a significant change in track radius due to recrystallisation of the damage tracks. At temperatures higher than 620 °C, the scattering images indicate fragmentation of the track cylinders into smaller subsections. Ion tracks were annealed at elevated temperatures up to 400 °C in the Durango and Ca-britholite, and up to 560 °C in Sr-britholite. While there was a significant change in the track radii in the Durango apatite, tracks in the two synthetic samples remained almost unchanged.

Afra, B.; Lang, M.; Bierschenk, T.; Rodriguez, M. D.; Weber, W. J.; Trautmann, C.; Ewing, R. C.; Kirby, N.; Kluth, P.

2014-05-01

208

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

209

Experimental modeling of the cooling history of Apollo 12 olivine basalts  

NASA Technical Reports Server (NTRS)

An analog of the Apollo 12 olivine vitrophyres has been crystallized in a 1-atm gas-mixing furnace at cooling rates ranging between 1250 and 0.7 C/hr and isothermally at degrees of supercooling ranging from 10 C to 325 C. Mineral chemistry, crystal shapes, grain sizes and textures are systematically related to cooling rate and degree of supercooling. At linear cooling rates not exceeding 40 C/hr the texture is porphyritic - large olivine crystals are set in a groundmass of finer-grained pyroxene, plagioclase, and ilmenite; a later generation of olivine never crystallizes. There are three shapes of olivine crystals in the Apollo 12 olivine vitrophyres: glomerocrysts of subhedral crystals, large subequant skeletons, and highly elongate skeletons. These result from three generations of nucleation and a two-stage cooling history - a slow preeruption stage and a rapid continuously increasing posteruption stage. It seems likely that the Apollo 12 olivine basalt magmas were erupted with olivine crystals in suspension. The nucleation temperature of olivine in cooling-rate experiments is dependent on the experimental technique, and hence results of cooling experiments should be applied with caution.

Donaldson, C. H.; Usselman, T. M.; Williams, R. J.; Lofgren, G. E.

1975-01-01

210

Cooling rates in the lower crust of the Oman ophiolite: Ca in olivine, revisited  

E-print Network

Cooling rates in the lower crust of the Oman ophiolite: Ca in olivine, revisited Jill A. Van crust of the Khafifah section in the Wadi Tayin massif of the Oman ophiolite. Additionally, very high B.V. All rights reserved. Keywords: calcium; olivine; oman; hydrothermal; cooling; crust 1

VanTongeren, Jill A.

211

SPINELS AND OXYGEN FUGACITY IN OLIVINE-PHYRIC AND LHERZOLITIC SHERGOTTITES. C.A. Goodrich, 2  

E-print Network

SPINELS AND OXYGEN FUGACITY IN OLIVINE-PHYRIC AND LHERZOLITIC SHERGOTTITES. 1 C.A. Goodrich, 2 C (possibly paired with NWA 1068 [9,10]), and to lherzolitic shergottite ALHA77005. Spinels in Olivine-Phyric Shergottites: Spinels in SaU 005 and EET-A are described by [11,12]. Spinels in Dhofar 019 (see also [8

Taylor, Lawrence A.

212

Relict olivine grains, chondrule recycling, and implications for the chemical, thermal, and mechanical processing  

E-print Network

Relict olivine grains, chondrule recycling, and implications for the chemical, thermal other incompatible ele- ments in olivine. Terrestrial weathering in a hot desert environment may have repeated thermal, chemical, and mechanical process- ing during a ``recycling" process over an extended time

213

Viscoplasticity of polycrystalline olivine experimentally deformed at high pressure and 900 C  

E-print Network

crystals are rare, because of technical difficulties (i.e., high stresses, close to the brittle failureViscoplasticity of polycrystalline olivine experimentally deformed at high pressure and 900 °C mantle Lithosphere TEM EBSD We have performed tri-axial compression experiments on olivine aggregates

Tommasi, Andrea

214

High-temperature condensation of iron-rich olivine in the solar nebula  

Microsoft Academic Search

The origin of oxidized iron in chondritic meteorites is a fundamental problem in meteoritics. Conventional models of meteorite formation assume FeO incorporation into olivine and pyroxene at around 500 K. There is evidence that at least some fayalitic olivine in Allende must have formed by condensation. Thermodynamic equilibrium calculations presented here define the nebular conditions that would enable condensation of

Herbert Palme; Bruce Fegley Jr.

1990-01-01

215

Systematics of Ni, Co, Cr and V in Olivine from Planetary Melt Systems: Martian Basalts  

NASA Technical Reports Server (NTRS)

Secondary Ion Mass Spectrometry (SIMS) data for Ni, Co, Cr, and V in olivine in martian basalts is compared to data from lunar and terrestrial basalts. We use experimentally-derived and published D values to calculate as-yet unsampled, olivine-bearing, non-cumulus melt compositions. Additional information is contained in the original extended abstract.

Herd, C. D. K.; Jones, J. H.; Shearer, C. K.; Papike, J. J.

2001-01-01

216

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

217

Fine, nickel-poor Fe-Ni grains in the olivine of unequilibrated ordinary chondrites  

NASA Astrophysics Data System (ADS)

Nickel-poor Fe-Ni grains smaller than 2.0 microns are common inclusions in ordinary, unequilibrated chondrites' porphyritic chondrule olivine, where the olivine grains seem to be relicts that survived chondrule formation without melting. This 'dusty' metal, whose most common occurrence is in the core of olivine grains having clear, Fe-poor rims, appears to be the product of the in situ reduction of FeO from the host olivine, with H2 or carbonaceous matter being the most likely reductants. H2 may have been implanted by solar wind or solar flare irradiation, but this requires the dissipation of nebular gas before the end of the chondrule formation process. Carbonaceous matter may have been implanted by shock. The large relict olivine grains may be nebular condensates or fragments broken from earlier chondrule generations.

Rambaldi, E. R.; Wasson, J. T.

1982-06-01

218

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

219

Termination and hydration of forsteritic olivine (0 1 0) surface  

NASA Astrophysics Data System (ADS)

Termination and hydration of the forsteritic (Fo90Fa10) olivine (0 1 0) surface have been investigated with high-resolution specular X-ray reflectivity and Atomic Force Microscopy. The surface was prepared by polishing a naturally grown {0 1 0} face, from which we found the polished surface in acidic (pH 3.5) alumina suspension exhibits regular steps while the basic (pH 9.5) silica polished surface is irregularly roughened, indicating there are two distinguishable mechanochemical processes for the surface dissolution. The quantitative interpretation of the regular steps from the alumina-polished surface suggests that the observed step heights correspond to multiples of crystallographic unit cell. Only this atomically terraced surface is investigated with the high-resolution X-ray reflectivity (HRXR) to determine the surface termination and hydration. The basic silica paste polished surface turned out too rough to measure with X-ray reflectivity. HRXR reveals that the alumina polished olivine (0 1 0) surface in pure water is terminated at a plane including half-occupied metal ion sites (M1), an oxygen vacancy site, and a silicate tetrahedral unit with one of its apices pointing outward with respect to the surface. An ideal termination with the oxygen vacancy would fulfill the stoichiometry of the formula unit; however, in the observation, the vacancy site is filled by an adsorbed water species and about a quarter of the remaining metal ions are further depleted. The terminating plane generates two distinct atomic layers in the laterally averaged electron density profile, on which two highly ordered adsorbed water layers are formed. The first layer formation is likely through the direct interaction with the M1 plane and the second layer is likely through the hydrogen bonding interaction with the first water layer. With this multilayered adsorbed water structure, the surface metal ion is partially hydrated by the vacancy-filling water species and adsorbed water molecules. The bulk water links to these distinct adsorbed water layers, with weak density oscillations that almost completely damp out after the first bulk water layer. The total thickness of the layered water structure including the two distinct adsorbed layers and the first layer of bulk water is slightly less than 1 nm, which corresponds to roughly three molecular layers of water. These results describe the steric constraints of the surface metal ion hydration and the iron redox environment during water-olivine interactions in this particular crystallographic orientation.

Yan, Hongping; Park, Changyong; Ahn, Gun; Hong, Seungbum; Keane, Denis T.; Kenney-Benson, Curtis; Chow, Paul; Xiao, Yuming; Shen, Guoyin

2014-11-01

220

Effect of Water on Fe-Mg Interdiffusion in Olivine  

NASA Astrophysics Data System (ADS)

To quantify the effect of water on the kinetics of Fe-Mg interdiffusion in olivine, diffusion couples composed of two single crystals of San Carlos olivine were hydrothermally annealed in a Paterson gas-medium high-pressure apparatus. Crystals were oriented using a micro-diffractometer with an orientation accuracy of approximately 1° . Samples with approximate dimensions 6x5x1 mm were cut with their large surfaces perpendicular to the [001] crystallographic axis. These (001) surfaces were mechanically polished to a 0.1 ? m finish on diamond lapping film and then mechanically polished and chemically etched with colloidal silica with an average grain size 0.04 ? m to remove the work-hardened surface layer. Each diffusion couple was formed from a Fo83 and a Fo91 crystal by placing their (001) planes in contact. Annealing experiments under both dry and water-saturated conditions were carried out at 1373 K and 300 MPa with oxygen fugacity buffered near the Ni-NiO phase boundary and a water fugacity about 300 MPa. Diffusion-bonded bi-crystals were successfully prepared following this procedure. In our hydrothermal experiments, hydrogen diffusion out of the sample capsule limits the annealing time to a few hours. Fourier transform infrared analyses demonstrate that the samples are water-saturated after the hydrothermal anneal. After each diffusion anneal, the Fe-Mg concentration profile was determined using energy dispersive x-ray spectroscopy in an analytical transmission electron microscope and/or Rutherford backscattering spectroscopy. The interdiffusion coefficient was calculated using the Boltzmann-Matano method. Under the imposed hydrous conditions, the interdiffusion coefficient is about 10-16 m2/s, a value approximately one order of magnitude larger than that determined under anhydrous conditions. The enhancement in Fe-Mg interdiffusion coefficient in the presence of water is a combined effect of the increase in the concentrations of water-derived point defects and the associated increase in the concentrations of intrinsic point defects in olivine as governed by the electroneutrality condition. The present result provides a basis for a quantitative understanding of the influence of water on the homogenization of geochemical anomalies through interdiffusion in the upper mantle.

Wang, Z.; Hiraga, T.; Mei, S.; Kohlstedt, D. L.

2001-12-01

221

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

222

The x ray microprobe determination of chromium oxidation state in olivine from lunar basalt and kimberlitic diamonds  

NASA Technical Reports Server (NTRS)

The synchrotron x-ray microprobe is being used to obtain oxidation state information on planetary materials with high spatial resolution. Initial results on chromium in olivine from various sources including laboratory experiments, lunar basalt, and kimberlitic diamonds are reported. The lunar olivine was dominated by Cr(2+) whereas the diamond inclusions had Cr(2+/Cr(3+) ratios up to about 0.3. The simpliest interpretation is that the terrestrial olivine crystallized in a more oxidizing environment than the lunar olivine.

Sutton, S. R.; Bajt, S.; Rivers, M. L.; Smith, J. V.

1993-01-01

223

Fe 2+-Mg partitioning between olivine and basaltic melts: Applications to genesis of olivine-phyric shergottites and conditions of melting in the Martian interior  

NASA Astrophysics Data System (ADS)

Fe 2+-Mg partitioning between olivine and basaltic melt, expressed by the exchange coefficient, K Dol - melt Fe - Mg [=( XmeltMg/ XolivineMg)/( XmeltFe 2 + / XolivineFe 2 + )] is widely used to check if a rock composition may represent a mantle-derived magma, to demonstrate equilibrium between coexisting olivine and groundmass in mafic-ultramafic systems, both in experiments and in natural assemblages, and to constrain liquid lines of descent where olivine is the dominant fractionating phase. However, K Dol - melt Fe - Mg of 0.30, which is appropriate for understanding most terrestrial basalts petrogenesis may not apply for Martian basalts as K Dol - melt Fe - Mg is known to depend strongly on the melt compositions and Martian systems produce basalts that are distinctly richer in iron than terrestrial basalts. Here we compiled experimental data on olivine-melt equilibria of Martian and terrestrial basalt compositions to parameterize the effect of magma composition on K Dol - melt Fe - Mg and derive the K Dol - melt Fe - Mg applicable for Martian magmatic systems. We find that the equilibrium relationship between olivine and basaltic melt in Martian systems is described by K Dol - melt Fe - Mg of 0.35 ± 0.01. Applying the newly parameterized values of K Dol - melt Fe - Mg to olivine-phyric shergottites suggest that the only known Martian meteorites where the olivine cores and the bulk composition are in equilibrium and therefore could represent magma compositions are: Yamato 980459, NWA 5789, and NWA 2990. LAR 06319, which has been suggested to represent a near magma composition, actually contains ~ 11 wt.% excess olivine. All other ol-phyric shergottites contain significant excess olivine (20-52 wt.%). Further, assuming that the basalts analyzed by the Mars Exploration Rovers at Gusev crater and the Bounce Rock in Meridiani Planum lie on olivine control lines, we have used our newly parameterized K Dol - melt Fe - Mg to estimate primary magmas in equilibrium with the model Martian mantle. Application of geothermobarometers to new primitive magma compositions suggest that basalt generation in the Martian mantle occurs at greater depths and higher temperatures than previously thought.

Filiberto, Justin; Dasgupta, Rajdeep

2011-04-01

224

Serpentinization of Sintered Olivine during Seawater Percolation Experiments  

NASA Astrophysics Data System (ADS)

Hydration of the mantle lithosphere exposed at slow spreading ridges leads to significant changes of the rock rheological, geophysical, mineralogical and geochemical properties, and to the production of large amounts of H2 and CH4, and of complex carbon molecules that support primitive ecosystems. The onset and efficiency of these hydrothermal processes requires penetration and renewal of fluids at the mineral-fluid interface. However, the mechanisms and the depth of fluid penetration are still poorly understood. Moreover, serpentinization is exovolumic, if a mass-conservative system is assumed, or chemical elements are leached out to conserve rock volume. Thus, the durability and extent of serpentinisation depends of the system capacity to create space and/or to drive mass transfers. In order to investigate these hydrodynamic and chemical mechanisms, we did a series of laboratory experiments during which seawater was injected in sintered San Carlos olivine samples at conditions representative of low temperature ultramafic hydrothermal systems. The percolation-reaction experiments were carried out using the ICARE 2 experimental bench at a confined pressure of 19 MPa and a temperature of 190°C; water flow was set at a constant specific discharge of 0.06 mL/h. During experiments (up to 23 days), 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 expense of olivine. Mass balance calculations indicate that, on average, 15 wt. % olivine was dissolved while the same mass of serpentine (+/- brucite) was formed; concurrently, porosity decreased 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. The estimated total hydrogen content of outlet fluids is 4.5 mmol/kg. Although these values are in the same range as those measured at the Lost City hydrothermal vent (e.g., Kelley et al, 2001), they are significantly lower than theoretical estimates of hydrogen composition of serpentinisation fluids (e.g., 21-170 mmol/kg, Wetzel & Shock, 2000). We infer that these differences result, in part, from poor fluid renewal at the mineral interface during experiments, and maybe also in natural systems. These experimental results are used to constrain numerical reactive transport models and better understand the scale and efficiency of serpentinization reactions (effective reaction rates in porous/fractured media) at the scale of spreading ridges. Ref.: Kelley et al., Nature, 412, 145-149, 2001; Wetzel & Shock, JGR, 105, 8319-8340, 2000.

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

2010-12-01

225

Collisional Processing of Comet Surfaces: Impact Experiments into Olivine  

NASA Technical Reports Server (NTRS)

A new paradigm has emerged where 3.9 Ga ago, a violent reshuffling reshaped the placement of small bodies in the solar system (the Nice model). Surface properties of these objects may have been affected by collisions caused by this event, and by collisions with other small bodies since their emplacement. In addition, objects in the Kuiper Belt are believed to undergo extensive collisional processing while in the Kuiper Belt. Physical manifestations of shock effects (e.g., planar dislocations) in minerals typically found in comets will be correlated with spectral changes (e.g. reddening, loss and shift of peaks, new signatures) to allow astronomers to better understand geophysical impact processing that has occurred on small bodies. Targets will include solid and granular olivine (forsterite), impacted over a range of impact speeds with the Experimental Impact Laboratory at NASA JSC. Analyses include quantification of the dependence of the spectral changes with respect to impact speed, texture of the target, and temperature.

Lederer, S. M.; Jensen, E. A.; Cintala, M. J.; Smith, D. C.; Nakamura-Messenger, K.; Keller, L. P.; Wooden, D. H.; Fernandez, Y. R.; Zolensky, M. E.

2011-01-01

226

Olivines in angrite LEW 87051: Phenos or xenos  

NASA Technical Reports Server (NTRS)

Nyquist et al. recently reported the presence of live Mn-53 in angrite LEW 86010 when it crystallized. Hence, melting must have occurred within approx. 10 Ma of the accretion of the angrite parent body, and LEW 86010 is the oldest known differentiated meteorite. This discovery has made it even more desirable to understand teh petrogenesis of angrites, which presumably were all formed at a similar time. As part of the continuing work on angrite petrogenesis, crystallization experiments were conducted on LEW 87051, the other Antarctic angrite, to clarify its petrogenesis. Several aspects of the experimental work is reported. Although the details are not understood, it is clear that the Cr abundance in the experimental olivines must be controlled by spinel crystallization.

Mckay, G.; Le, L.; Wagstaff, J.

1991-01-01

227

The distribution of olivine in the crater Copernicus  

NASA Technical Reports Server (NTRS)

Multispectral imaging in the visible and near-IR at four wavelengths (0.73, 0.96, 1.45, and 1.99 micron) of Copernicus crater has been used to map the distribution of olivine-rich, pyroxene-poor material known previously to occur in the central peak complex. Three additional portions of the crater exhibit spectral characteristics similar to those of the central peaks, strongly suggesting the presence of material similar to that exposed in the central peaks. These areas are a scarp forming a portion of the northern rim of Copernicus, and two slump blocks in the north wall which may have been derived from the same portion of the ejecta now exposed in the rim scarp. These occurrences decrease the minimum allowable depth for this unusual material in the Copernicus target site though still represent some of the deepest material exposed by Copernicus.

Lucey, Paul G.; Hawke, B. R.; Horton, Keith

1991-01-01

228

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. M.

2007-01-01

229

Stereochemically constrained complex organic molecules extracted from olivine crystal matrix  

NASA Astrophysics Data System (ADS)

Paradoxically, the dense solid state of magmatic minerals is a medium, in which organic synthesis can take place. The reason is that gas-fluid components such as H2O, CO/CO2/N2 and H2S are omnipresent in terrestrial magmatic environments. Any silicate mineral that crystallizes from such magmas will incorporate small quantities of the fluid-phase components in the form of structurally incompatible low-z impurities. During cooling the solute species undergo a redox conversion, resulting in chemically reduced low-z elements. To the extent that these low-z impurities are diffusively mobile, they will exsolve to the surface and/or to major structural defects inside the crystal matrix such as dislocations. Dislocations provide a 3-D structured environment, where the low-z impurities will tend to form stereochemically constrained polyatomic Cn-H-O-N-S entities, which we call organic protomolecules. In Nature, during weathering, such protomolecules will be released into the environment in the form of complex organic molecules. In our study we crush samples under clean conditions as a way to expose Cn-H-O-N-S entities at the fracture surfaces. We conduct identical experiments with selected large olivine single crystals, mm-sized olivine from peridiotite nodules from the San Carlos Volcanic Field, Arizona, and the vesiculated basalt that had carried the nodules upward in the volcanic conduit. We Soxhlet-extract the crushed powders with water, THF and ethyl acetate. The extracts are analyzed at the FTICR-MS facility at Florida State University using ultrahigh resolution Mass Spectrometry techniques capable of determining the chemical composition of the organic molecules up to 600 amu and more. So far we have found several analog sequences of oxygen-rich aliphatic hydrocarbons, families with up to 34 carbon atoms, probably poly-carboxylic acids, and some families containing sulfur.

Gerasimenko, I.; Freund, F. T.; Imanaka, H.; Rodgers, R.

2011-12-01

230

A Re-appraisal of Olivine Sorting and Accumulation in Hawaiian Magmas.  

NASA Astrophysics Data System (ADS)

Bowen never used the m-words (magma mixing) in his highly influential book "The Origin of the Igneous Rocks". Yet, in the past 20-30 years, magma mixing has been proposed as an important, almost ubiquitous, process at volcanoes in all tectonic environments ranging from oceanic basalts to large silicic magma bodies, and as the possible trigger of eruptions. Bowen regarded Hawaiian olivine basalts and picrites as the result of olivine accumulation in a lower MgO magma that was crystallizing and fractionating olivine. This, with variants, has been the party line ever since, the only debate being over the MgO content of the proposed parental magmas. Although magma mixing has been recognized as an important process in differentiated, low-MgO (below 7 percent), Hawaiian magmas, the wide range in MgO (7-30 percent) in Hawaiian olivine tholeiites and picrites is invariably attributed to olivine crystallization, fractionation and accumulation. In this paper I will re-evaluate this hypothesis using well-documented examples from Kilauea, Mauna Kea and Mauna Loa that exhibit well-defined, coherent linear trends of major oxides and trace elements with MgO . If olivine control is the only factor responsible for these trends, then the intersection of the regression lines for each trend should intersect olivine compositions at a common forsterite composition, corresponding to the average accumulated olivine in each of the magmas. In some cases (the ongoing Puu Oo eruption) this simple test holds and olivine fractionation and accumulation can clearly be shown to be the dominant process. In other examples from Mauna Kea and Mauna Loa (1852, 1868, 1950 eruptions, and Mauna Loa in general) the test does not hold, and a more complicated process is required. Additionally, for those magmas that fail the test, CaO/Al2O3 invariably decreases with decreasing MgO content. This should not happen if only olivine fractionation and accumulation are involved. The explanation for these linear trends that approach, but fail to intersect, appropriate olivine compositions is a combination of magma mixing accompanied by olivine crystallization and accumulation. One of the mixing components is a is a high-MgO (about13-15 percent) magma laden with olivine phenocrysts and xenocrysts and the other is a consanguineous low-MgO (about 7 percent) quasi "steady-state" magma, with a prior history of clinopyroxene and plagioclase fractionation.

Rhodes, J. M.

2002-12-01

231

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

232

Timescales for Reequilibration of Major Elements in Olivine-Hosted Melt Inclusions  

NASA Astrophysics Data System (ADS)

Geochemical evidence demonstrates that near-fractional partial melts form over a range of upper mantle conditions from peridotites with variable bulk compositions. The importance of determining the initial compositions of melt inclusions lies in the ability of the major elements to record information about the conditions at which melt generation takes place, and the involvement of exotic lithologies in the melt generation process. However, before the major-element compositions of melt inclusions can be interpreted reliably, the effects of post-entrapment processes must be quantitatively understood. Diffusive reequilibration of olivine-hosted melt inclusions during cooling, magma mixing, or decompression can produce irreversible compositional changes in response to changes to the melt outside of the host olivine. Factors that influence the timescales for reequilibration of major elements in olivine-hosted melt inclusions are the sizes of the inclusion and the host olivine, which control the diffusion lengthscale, and the olivine-melt partition coefficient and diffusivity, which control the flux through the olivine grain. Among the major elements, Fe, Mg and Ca have the greatest potentials for undergoing diffusive reequilibration. The concentration of H2O in olivine-hosted melt inclusions must also be evaluated with care. Based on experimentally determined diffusivities and partition coefficients, reequilibration of Fe and Mg occurs on a timescale of years, while Ca reequilibrates over a few decades. Diffusion of H in olivine is rapid enough to allow reequilibration in a matter of hours. Important questions the must be answered in order to fully assess the reliability of the melt inclusion compositions are whether the history of Fe/Mg transport through the olivine can be uniquely determined, whether there are factors that rate limit transport of H, and whether gradients in slower diffusing elements can be used to constrain re-equilibration timescales.

Gaetani, G. A.; Hauri, E. H.

2008-12-01

233

Magnetic properties of natural and synthetic olivines: high-field measurements  

NASA Astrophysics Data System (ADS)

Olivine [(Fex, Mg1-x)2 SiO4] is an orthosilicate solid solution between fayalite [Fe2 SiO4] and forsterite [Mg2 SiO4]. Olivine is a major constituent of the Earth mantle that is abundant in oceanic and continental peridotites and mantle xenoliths. The magnetic properties of olivines have been previously investigated using gem quality natural crystals known as peridots (Zabargad) or using laboratory grown synthetic crystals. Magnetic investigations are generally performed using low magnetic field or neutron diffraction techniques. Optical microscopy and TEM imagery reveal that most olivine crystals host iron oxides formed by exsolution during cooling. Theoretically, the magnetic susceptibility of olivine should decrease linearly from fayalite to fayalite as a function of the Fe content. The magnetic behavior should range from antiferromagnetic at high Fe content, paramagnetic at intermediate Fe contents and diamagnetic at very low Fe contents. New magnetic measurements, performed on various high field instruments (vibrating sample magnetometer, torque magnetometer, cantilever magnetometer), both on natural and synthetic samples, display ferromagnetic behavior, interpreted as due to the systematic presence of titanomagnetite inclusions in olivine crystals. These results emphasize the need to conduct measurements in high field in order to isolate the intrinsic paramagnetic properties of olivines. These measurements demonstrate the orthorhombic nature of the intrinsic paramagnetic properties, but also yield new data concerning the relationship between crystallographic axes, magnetic anisotropy and other physical anisotropies: [100] = K1, [010] = K2 and [001] = K3. Preliminary results also indicate substantial variations in degree of paramagnetic anisotropy (P) and paramagnetic shape factor (T). For Fo92, P = 1.359 and T = -0.845. These intrinsic paramagnetic properties are used to model the magnetic behavior of olivine across a range of temperatures relevant to planetary exploration. They are also used to evaluate the possible effects of olivine deformation on its intrinsic properties. For example, deformation-induced striped iron zoning is anticipated to strongly modify crystal magnetic anisotropy.

Ferre, E. C.; Martin-Hernandez, F.

2004-12-01

234

Cellular Precipitates Of Iron Oxide in Olivine in a Stratospheric Interplanetary Dust Particle  

NASA Technical Reports Server (NTRS)

The petrology of a massive olivine-sulphide interplanetary dust particle shows melting of Fe,Ni-sulphide plus complete loss of sulphur and subsequent quenching to a mixture of iron-oxides and Fe,Ni-metal. Oxidation of the fayalite component in olivine produced maghemite discs and cellular intergrowths with olivine and rare andradite-rich garnet. Cellular reactions require no long-range solid-state diffusion and are kinetically favourable during pyrometamorphic oxidation. Local melting of the cellular intergrowths resulted in three dimensional symplectic textures. Dynamic pyrometamorphism of this asteroidal particle occurred at approx. 1100 C during atmospheric entry flash (5-15 s) heating.

Rietmeijer, Frans J. M.

1996-01-01

235

Cr, Mn, and Ca distributions for olivine in angritic systems: Constraints on the origins of Cr-rich and Ca-poor core olivine in angrite LEW87051  

NASA Technical Reports Server (NTRS)

Angrite meteorites are a type of basaltic achondrites that are noted for their very old cyrstallization ages (4.55 b.y.) and unusual chemical and mineralogical properties. In spite of great interest, only four angrites have been found. LEW87051 is the smallest one which weighs 0.6 g. It is a porphyritic rock with coarse subhedral to euhedral olivines set in a fine-grained groundmass which clearly represents a crystallized melt. The largest uncertainty about the petrogenesis of LEW87051 is the relationship between the large olivine crystals and the groundmass. Prinz et al. suggests that olivines are xenocrysts, while McKay et al. proposed a fractional cyrstallization model based on experimental studies. However, the crystals have Cr-rich and Ca-poor cores which do not match experimental olivines. Although Jurewicz and McKay tried to explaine the zoning of the rim by diffusion, some features are not explained. There also exists a definite composition boundary of Fe(2+) and MnO between the core and the rim. To clarify the origin of these olivines, we have performed experiments using LEW87051 analogs to measure the effects of oxygen fugacity on distribution coefficients of various elements in an angritic system.

Mikouchi, T.; Mckay, G.; Le, L.

1994-01-01

236

An Olivine-Rich Crater in Tyrrhena Terra  

NASA Technical Reports Server (NTRS)

This image of the ejecta of a crater in the Tyrrhena Terra region was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 0328 UTC on February 23, 2007 (10:28 p.m. EST on February 22, 2007), near 13 degrees south latitude, 67 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 18 meters (60 feet) across. The region covered is roughly 9 kilometers (5.6 miles) wide at its narrowest point.

Named for a classic albedo feature, Tyrrhena Terra is an extensive, heavily-cratered part of Mars' southern highlands, some 2,300 kilometers (1,430 miles) at its broadest extent. It is located to the northeast of the Hellas basin. The region imaged by CRISM is to the north of Hellas Planitia and just east of the crater Huygens in Tyrrhena Terra's western end.

The uppermost image in the montage above reveals the location of the CRISM image on a mosaic taken by the Mars Odyssey spacecraft's Thermal Emission Imaging System (THEMIS). The CRISM image is located inside a large, flat-floored crater measuring about 52 kilometers (32 miles) across. The image includes a small crater and its ejecta blanket, an apron of material thrown out during a crater's formation, both located inside the larger crater.

The lower left image is an infrared false-color image that reveals the extent of the ejecta blanket. It also includes ejecta from another small crater located just east of the CRISM image.

The lower right image shows the strengths of mineral absorptions, and reveals the composition of the ejecta and surrounding material. The ejecta surrounding the small impact crater is thickest at the crater's rim, and becomes thinner to discontinuous at the blanket's outer edge. This small crater's ejecta blanket shows an enhanced spectral signature of the mineral olivine, as does the ejecta from the small crater just out of view to the east. In contrast the surrounding material is rich in the volcanic mineral pyroxene. This relationship demonstrates the layered characteristic of rocks forming the southern highlands: olivine-rich rock was buried by pyroxene-rich materials on the larger crater's floor, probably volcanic lavas. Later, the small crater penetrated the pyroxene-rich rock, excavated the underlying olivine-bearing unit, and deposited it as ejecta.

CRISM is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, Laurel, Md., the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter and the Mars Science Laboratory for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter.

2008-01-01

237

First-principles investigation of Li intercalation kinetics in phospho-olivines  

E-print Network

This thesis focuses broadly on characterizing and understanding the Li intercalation mechanism in phospho-olivines, namely LiFePO? and Li(Fe,Mn)PO?, using first-principles calculations. Currently Li-ion battery technology ...

Malik, Rahul

2013-01-01

238

Phase behavior and phase transformation kinetics during electrochemical cycling of lithium transition metal olivine compounds  

E-print Network

Olivine LiMPO4 (M = Fe, Mn, Co, Ni) compounds have received most attention from the battery research community as the cathodes for Li-ion batteries because of several advantages, including a high theoretical capacity, 170 ...

Meethong, Nonglak

2009-01-01

239

Are Megacrysts in Olivine-Phyric Shergottites Xenocrysts, Phenocrysts, or Something Else?  

NASA Astrophysics Data System (ADS)

We argue based on detailed analyses and modeling of shergottite LAR 06319 that its olivines are antecrysts, formed from a melt similar to the current groundmass and entrained from a cumulate pile prior to eruption.

Balta, J. B.; McSween, H. Y.

2011-03-01

240

NEBULAR FORMATION OF FAYALITIC OLIVINE: INEFFECTIVENESS OF DUST ENRICHMENT. A. V. Fedkin1  

E-print Network

to form fayalite, is con- sumed by reaction with H2S to form troilite, FeS. Be- cause all three dust,5], making diffusion slower; as well as recognition of non-ideality in olivine solid solutions, lowering

Grossman, Lawrence

241

FULL PAPER Open Access Characterization of olivine fabrics and mylonite in  

E-print Network

of the surrounding anorthosite complex is displayed in ultramafic lenses as a modal variation in olivine, pyroxenes, and spinel, and the Caledonian eclogite-facies structure in the surrounding anorthosite gabbro is represented

Jung, Haemyeong

242

Trace Element Distribution Between Olivine and Kirschsteinite in Angra Dos Reis  

NASA Technical Reports Server (NTRS)

The angrites are a small and enigmatic group of basaltic achondrites that possess unique mineralogical and chemical properties. The dominant mineralogy of the seven angrite members (Angra dos Reis, LEW 86010, LEW 87051, Asuka 881371, Sahara 99555, D Orbigny, and a new Moroccan member) is fassaite, olivine, and plagioclase. Angrites display a wide range of thermal histories, with Angra dos Reis (AdoR) exhibiting a cooling history different from that of the rapidly cooled members and from LEW86010, a more slowly cooled member. AdoR could represent either a cumulate or a porphyritic igneous rock that was later altered by metamorphism. We are re-examining the thermal history of AdoR in light of the more recently described angrite members. Our emphasis is a trace element study of low-Ca olivine, which we refer to as olivine, and high-Ca olivine, which we refer to as kirschsteinite, in AdoR.

Fittipaldo, M. M.; Jones, R. H.; Shearer, C. K.

2003-01-01

243

Olivine-Orthopyroxene Equilibrium in Metal-rich Systems: Applications to Achondrites and Equilibrated Chondrites  

NASA Technical Reports Server (NTRS)

Olivine and orthopyroxene are major minerals in every type of stony meteorite. The majority of achondritic meteorites and silicate-bearing iron meteorites have experienced high temperatures. If these temperatures persisted for an extended period of time then the iron contents of olivine and orthopyroxene should be in equilibrium. In their study of ungrouped clasts and chondritic meteorites, suggested that the equilibrium compositions of olivine and orthopyroxene should fall on a mixing line between LL chondrites and aubrites. Here we show that this is not necessarily the case and that a range of FeO contents in olivine and orthopyroxene can be in equilibrium with each other. The key parameters that determine the equilibrium Fe content in these minerals are temperature, oxygen fugacity (fO2), and silica activity (aSiO2).

Lauretta, D. S.; Benedix, G. K.; McCoy, T. J.

2003-01-01

244

Carbon sequestration via aqueous olivine mineral carbonation: role of passivating layer formation  

Microsoft Academic Search

COâ sequestration via carbonation of widely available low-cost minerals, such as olivine, can permanently dispose of COâ in an environmentally benign and a geologically stable form. The paper reports the results of studies of the mechanisms that limit aqueous olivine carbonation reactivity under the optimum sequestration reaction conditions observed to date: 1 M NaCl + 0.64 M NaHCOâ at T

Hamdallah Bearat; Michael J. McKelvy; Andrew V. G. Chizmeshya; Deirdre Gormley; Ryan Nunez; R. W. Carpenter; Kyle Squires; George H. Wolf

2006-01-01

245

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

Microsoft Academic Search

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

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

2011-01-01

246

Demonstration of the Electrical Conductivity Jump Produced by the Olivine-Spinel Transition  

Microsoft Academic Search

The electrical conductivity of both the olivine and spinel polymorphs of Fe2SiO, has been determined at 300 to 1200øK and at 31 to 62 kb by means of a tetrahedral anvil-type high-pressure apparatus. It is established that the olivine-spinel transition is responsible for the discontinuous change in the electrical conductivity of Fe2SiO, the conductivity jump at the time of the

Syun-Iti Akimoto; Hideyuki Fujisawa

1965-01-01

247

Eutectoid phase transformation of olivine and spinel into perovskite and rock salt structures  

Microsoft Academic Search

Microstructural observations of the products of the transformation of (Mg, Fe)2SiO4 olivine and spinel and Ca2GeO4 olivine into magnesiowuesite, a transformation postulated to occur in the mantle. The transformation was achieved using a diamond anvil cell with a center pressure of about 400 kbar. The specimens were also heated with a YAG laser up to 2000 C to study the

J. P. Poirier; J. Peyronneau; M. Madon; F. Guyot; A. Revcolevschi

1986-01-01

248

Water diffusion as a natural process in olivine crystals from garnet-perodotite xenoliths in basalts  

Microsoft Academic Search

Experimental work on the kinetics of hydration\\/dehydration of olivine indicates that the water content in natural olivine is representative only of the last hydration\\/dehydration event in its geologic history. This dissolved water would be lost in just a few hours on ascent from depths at which temperatures are over 800oC. However, to date, water diffusion profiles in natural nominally anhydrous

S. Demouchy; F. Gaillard; C. R. Stern; S. Mackwell

2003-01-01

249

A Tale of Two Olivines: Magma Ascent in the Auckland Volcanic Field, New Zealand  

NASA Astrophysics Data System (ADS)

The Auckland Volcanic Field (AVF) is a nephelinitic to subalkali basaltic monogenetic field centered on the city of Auckland, New Zealand. Lavas are olivine-phyric, and the deposits of several volcanoes in the field contain olivine crystals with chrome spinel (Cr-spinel) inclusions. Microprobe analyses show at least two populations of olivine, categorised by their Mg# and their spinel inclusion compositions: the first has olivines that are euhedral, have compositions slightly less forsteritic than expected for whole rock Mg#, and have Cr-spinel inclusions with relatively low Cr2O3 contents of ~20%. These are interpreted as antecrysts inherited from the mantle source that yielded their host magma. The second population is characterised by olivines that are sub- to euhedral, are significantly more forsteritic than expected from their host whole rock Mg#, and have Cr-spinel inclusons with relatively high Cr2O3 contents of ~50%. These are interpreted as xenocrysts. The composition of these high Cr2O3 spinels very closely resembles the composition of spinels within olivines in dunite sampled from the Dun Mountain Ophiolite on the South Island of New Zealand. The northward extension of the Dun Mountain complex beneath the North Island is defined by the Junction Magnetic Anomaly, marking a crustal terrane boundary that underlies the Auckland Volcanic Field. These data indicate that the magmas that have risen to produce the volcanoes of the Auckland Volcanic Field have carried crystals from an underlying ultramafic crust as well as from their asthenospheric source. Euhedral olivine crystals which do not contain Cr-spinel are also present in AVF lavas and these are interpreted as true phenocrysts that crystallised directly from their host magmas. The lack of reaction textures at crystal margins suggests rapid ascent rates. A crustal origin for the xenocrysts not only has large implications for ascent rate modelling of olivines, but also for the crustal structure of the Auckland area and possible magma ascent paths under the AVF.

Smid, E. R.; McGee, L. E.; Smith, I. E.; Lindsay, J. M.

2013-12-01

250

Excitation and relaxation of olivine after swift heavy ion impact  

NASA Astrophysics Data System (ADS)

A multiscale model was developed to describe excitation and initial relaxation of an insulator after an impact of a swift heavy ion (SHI) decelerated in the electronic stopping regime. This model consists of a combination of three methods: (a) Monte Carlo simulations of the nonequilibrium kinetics of the electron subsystem of a solid at the femtosecond scale after the projectile passage. The complex dielectric function (CDF) is used to construct the cross sections for the MC model taking into account a collective response of the electron ensemble to excitation. (b) A molecular-kinetic approach describing further spatial spreading of electrons after finishing of ionization cascades up to hundred femtoseconds. And (c) molecular dynamics simulations of a reaction of the lattice on the excess energy transferred from the relaxing electron subsystem at the picosecond time scale. The dynamic structure factor (DSF) formalism is used to calculate the electron-lattice energy exchange in a general way which is valid for sub-picosecond timescales, beyond the phononic approximation of the lattice dynamics. The calculations were performed for 2 GeV Au ion in olivine, demonstrating a heating of the lattice up to 700 K in the nanometric scale picoseconds after the projectile passage.

Gorbunov, S. A.; Medvedev, N. A.; Rymzhanov, R. A.; Terekhin, P. N.; Volkov, A. E.

2014-05-01

251

Water in Pyroxene and Olivine from Martian Meteorites  

NASA Technical Reports Server (NTRS)

Water in the interior of terrestrial planets can be dissolved in fluids or melts and hydrous phases, but can also be locked as protons attached to structural oxygen in lattice defects in nominally anhydrous minerals (NAM) like olivine, pyroxene, or feldspar [1-3]. Although these minerals contain only tens to hundreds of ppm H2O, this water can amount to at least one ocean in mass when added at planetary scales because of the modal dominance of NAM in the mantle and crust [4]. Moreover these trace amounts of water can have drastic effects on melting temperature, rheology, electrical and heat conductivity, and seismic wave attenuation [5]. There is presently a debate on how much water is present in the martian mantle. Secondary ionization mass spectrometry (SIMS) studies of NAM [6], amphiboles and glass in melt inclusions [7-10], and apatites [11, 12] from Martian meteorites report finding as much water as in the same phases from Earth's igneous rocks. Most martian hydrous minerals, however, generally have the relevant sites filled with Cl and F instead of H [13, 14], and experiments using Cl [15] in parent melts can reproduce Martian basalt compositions as well as those with water [16]. We are in the process of analyzing Martian meteorite minerals by Fourier transform infrared spectrometry (FTIR) in order to constrain the role of water in this planet s formation and magmatic evolution

Peslier, A. H.

2012-01-01

252

The effect of manganese on olivine-quartz-orthopyroxene stability  

NASA Astrophysics Data System (ADS)

The effect of manganese on the stability of ferrosilite relative to fayalite + quartz has been experimentally determined to assess its importance to orthopyroxene barometry. Reaction reversals in a piston-cylinder apparatus were obtained to within 0.1-kbar intervals indicating instability of Fs 95Rh 5 below 10.3, 10.9, 11.4, 12.2, 12.9, 13.7 kbar and Fs 90Rh 10 below 9.8, 10.4, 10.9, 11.6, 12.4 and 13.2 kbar at 750, 800, 850, 900, 950 and 1000°C, respectively. Each mole % MnSiO 3 extends the pyroxene stability by approximately 0.12 kbar relative to FeSiO 3. Electron microprobe analyses of run products indicate a small preference of Mn for pyroxene over olivine with KDMn-Fe opx-oliv = 1.2-1.5, similar to values observed for natural pairs. Mössbauer spectra are consistent with a random distribution of Mn between the M1 and M2 sites in the orthopyroxene. These experimental data allow downward revision of pressure estimates based on the orthopyroxene barometer in areas where Mn is a significant component in orthopyroxene.

Bohlen, Steven R.; Boettcher, Arthur L.; Dollase, Wayne A.; Essene, Eric J.

1980-03-01

253

Deformation induced slip-system transition in olivine at high pressures  

NASA Astrophysics Data System (ADS)

Deformation-induced olivine fabrics provide vital information for understanding seismic anisotropy in the upper mantle since olivine is the primary mineral in this region. Our recent analysis of the fabric of deformed olivine aggregates has documented the influence of deformation conditions (e.g., temperature and stress) on the fabric evolution of olivine at high pressures. Experiments were carried out using a deformation-DIA on an X-ray beamline at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory. Samples of polycrystalline olivine were deformed at a constant displacement rate of ~ 3.0 × 10- 5 s-1 over true axial strains of ~ 30% at temperatures of 673 to 1573 K and pressures of 5 to 9 GPa. Electron backscattered diffraction (EBSD) analyses of the fabrics of the deformed samples reveal a transition in slip system. For low temperatures (T < 1173 K) and high stresses (? > 2 GPa), the normals to the (100) lattice planes are parallel to the maximum principal stress; while at high temperatures (T > 1473 K) and lower stresses (? < 1 GPa), the normals to the (010) lattice planes switch to be parallel to the maximum principal stress. This transition in fabric occurs even if pressure is fixed, indicating that pressure is not a primarily factor causing the transition in dominant slip system. Our observations indicate that deformation of olivine is dominated by the (100) [001] slip system at low temperatures and high stresses and by the (010) [100] slip system at high temperatures and low stresses.

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

2008-12-01

254

A comparison of FeO-rich, porphyritic olivine chondrules in unequilibrated chondrites and experimental analogues  

NASA Astrophysics Data System (ADS)

Experimentally produced analogues of porphyritic olivine (PO) chondrules in ordinary chondrites provide an important insight into chondrule formation processes. We have studied experimental samples with PO textures grown at three different cooling rates (2, 5 and 100 C/h), and samples that have been annealed at high temperatures (1000-1200 C) subsequent to cooling. These are compared with natural chondrules of similar composition and texture from the ordinary chondrites Semarkona (LL3.0) and ALH 81251 (LL3.3). Zoning properties of olivine grains indicate that the Semarkona chondrules cooled at comparable rates to the experiments. Zoning in olivine from chondrules in ALH 81251 is not consistent with cooling alone but indicates that the chondrules underwent an annealing process. Chromium loss from olivine is very rapid during annealing and calculated diffusion coefficients for Cr in olivine are very similar to those of Fe-Mg interdiffusion coefficients under the same conditions. Annealed experimental samples contain an aluminous, low-Ca pyroxene which forms by reaction of olivine and liquid. No similar reaction texture is observed in ALH 81251 chondrules, and this may be evidence that annealing of the natural samples took place at considerably lower temperatures than the experimental analogues. The study supports the model of chondrule formation in a cool nebula and metamorphism of partly equilibrated chondrites during reheating episodes on the chondrite parent bodies.

Jones, R. H.; Lofgren, G. E.

1993-06-01

255

Characterization and Petrologic Interpretation of Olivine-Rich Basalts at Gusev Crater, Mars  

NASA Technical Reports Server (NTRS)

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., III; 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, A.; DesMarais, D. J.; Economou, T.; Farmer, J. D.; Farrand, W.; Ghosh, A.; Golombek, M.; Gorevan, S.; Greeley, R.

2006-01-01

256

Disclinations provide the missing mechanism for deforming olivine-rich rocks in the mantle.  

PubMed

Mantle flow involves large strains of polymineral aggregates. The strongly anisotropic plastic response of each individual grain in the aggregate results from the interactions between neighbouring grains and the continuity of material displacement across the grain boundaries. Orthorhombic olivine, which is the dominant mineral phase of the Earth's upper mantle, does not exhibit enough slip systems to accommodate a general deformation state by intracrystalline slip without inducing damage. Here we show that a more general description of the deformation process that includes the motion of rotational defects referred to as disclinations can solve the olivine deformation paradox. We use high-resolution electron backscattering diffraction (EBSD) maps of deformed olivine aggregates to resolve the disclinations. The disclinations are found to decorate grain boundaries in olivine samples deformed experimentally and in nature. We present a disclination-based model of a high-angle tilt boundary in olivine, which demonstrates that an applied shear induces grain-boundary migration through disclination motion. This new approach clarifies grain-boundary-mediated plasticity in polycrystalline aggregates. By providing the missing mechanism for describing plastic flow in olivine, this work will permit multiscale modelling of the rheology of the upper mantle, from the atomic scale to the scale of the flow. PMID:24572356

Cordier, Patrick; Demouchy, Sylvie; Beausir, Benoît; Taupin, Vincent; Barou, Fabrice; Fressengeas, Claude

2014-03-01

257

Petrogenesis of olivine-phyric shergottite Larkman Nunatak 06319: Implications for enriched components in martian basalts  

NASA Astrophysics Data System (ADS)

We report on the petrography and geochemistry of the newly discovered olivine-phyric shergottite Larkman Nunatak (LAR) 06319. The meteorite is porphyritic, consisting of megacrysts of olivine (?2.5 mm in length, Fo 77-52) and prismatic zoned pyroxene crystals with Wo 3En 71 in the cores to Wo 8-30En 23-45 at the rims. The groundmass is composed of finer grained olivine (<0.25 mm, Fo 62-46), Fe-rich augite and pigeonite, maskelynite and minor quantities of chromite, ulvöspinel, magnetite, ilmenite, phosphates, sulfides and glass. Oxygen fugacity estimates, derived from the olivine-pyroxene-spinel geo-barometer, indicate that LAR 06319 formed under more oxidizing conditions (QFM -1.7) than for depleted shergottites. The whole-rock composition of LAR 06319 is also enriched in incompatible trace elements relative to depleted shergottites, with a trace-element pattern that is nearly identical to that of olivine-phyric shergottite NWA 1068. The oxygen isotope composition of LAR 06319 (? 17O = 0.29 ±0.03) confirms its martian origin. Olivine megacrysts in LAR 06319 are phenocrystic, with the most Mg-rich megacryst olivine being close to equilibrium with the bulk rock. A notable feature of LAR 06319 is that its olivine megacryst grains contain abundant melt inclusions hosted within the forsterite cores. These early-trapped melt inclusions have similar trace element abundances and patterns to that of the whole-rock, providing powerful evidence for closed-system magmatic behavior for LAR 06319. Calculation of the parental melt trace element composition indicates a whole-rock composition for LAR 06319 that was controlled by pigeonite and augite during the earliest stages of crystallization and by apatite in the latest stages. Crystal size distribution and spatial distribution pattern analyses of olivine indicate at least two different crystal populations. This is most simply interpreted as crystallization of megacryst olivine in magma conduits, followed by eruption and subsequent crystallization of groundmass olivine. LAR 06319 shows close affinity in mineral and whole-rock chemistry to olivine-phyric shergottite, NWA 1068 and the basaltic shergottite NWA 4468. The remarkable features of these meteorites are that they have relatively similar quantities of mafic minerals compared with olivine-phyric shergottites (e.g., Y-980459, Dho 019), but flat and elevated rare earth element patterns more consistent with the LREE-enriched basaltic shergottites (e.g., Shergotty, Los Angeles). This relationship can be interpreted as arising from partial melting of an enriched mantle source and subsequent crystal-liquid fractionation to form the enriched olivine-phyric and basaltic shergottites, or by assimilation of incompatible-element enriched martian crust. The similarity in the composition of early-trapped melt inclusions and the whole-rock for LAR 06319 indicates that any crustal assimilation must have occurred prior to crystallization of megacryst olivine, restricting such processes to the deeper portions of the crust. Thus, we favor LAR06319 forming from partial melting of an "enriched" and oxidized mantle reservoir, with fractional crystallization of the parent melt upon leaving the mantle.

Basu Sarbadhikari, Amit; Day, James M. D.; Liu, Yang; Rumble, Douglas, III; Taylor, Lawrence A.

2009-04-01

258

CO2-induced small water solubility in olivine and implications for properties of the shallow mantle  

NASA Astrophysics Data System (ADS)

H2O and CO2 are important components of fluids in the mantle at ?30-150 km depth, and may affect strongly water dissolution in nominally anhydrous olivine; however, available experimental hydrogenation of olivine has been nearly exclusively carried out in coexistence with H2O (CO2-free). In this study, the effect of CO2 on water solubility in olivine has been investigated by H-annealing natural olivine under peridotite- and fluid-saturated conditions. Experiments were conducted at 1.5-5 GPa and 1100-1300 °C, with oxygen fugacity controlled by Ni-NiO and with either H2O or H2O-CO2 as buffering fluid. The olivine shows no change in composition during the experiments. The infrared spectra of the hydrated olivine are characterized by prominent OH bands from ?3650 to 3000 cm in all the runs, at both high frequency (>3450 cm) and low frequency (<3450 cm), and the H2O solubility is ?120-370 ppm for the olivine in coexisting with H2O, and ?65-180 ppm for the olivine in coexisting with H2O-CO2. When CO2 is present in the buffering fluid, the H2O solubility of olivine is reduced by a factor of ?2, due to effect on the partitioning of water between minerals and coexisting fluid, and the measured H2O solubility shows independence on fluid composition (the molar ratio of CO2 to CO2 + H2O at ?0.2-0.5) given pressure, temperature and oxygen fugacity. Olivine equilibrated in the shallow mantle is probably dominated by OH groups in the wavenumber ?3650-3000 cm, and the intensity of OH bands at low frequency may be higher than or comparable to those at higher frequencies. The storage capacity of water in the shallow mantle in previous estimates may have been overestimated by a factor of at least ?4 if the observed effect of CO2 on water solubility is correct. Our results have profound influence on understanding partial melting, electrical conductivity anomalies and metasomatism in the shallow mantle.

Yang, Xiaozhi; Liu, Dingding; Xia, Qunke

2014-10-01

259

Diffusive Fractionation of Lithium Isotopes in Olivine Grain Boundaries  

NASA Astrophysics Data System (ADS)

Diffusive fractionation of isotopes has been documented in silicate melts, aqueous fluids, and single crystals. In polycrystalline rocks, the meeting place of two grains, or grain boundaries, may also be a site of diffusive fractionation of isotopes. We have undertaken an experimental and modeling approach to investigate diffusive fractionation of lithium (Li) isotopes by grain boundary diffusion. The experimental procedure consists of packing a Ni metal capsule with predominantly ground San Carlos olivine and subjecting the capsule to 1100C and 1GPa for two days in a piston cylinder apparatus to create a nominally dry, 'dunite rock'. After this synthesis step, the capsule is sectioned and polished. One of the polished faces of the 'dunite rock' is then juxtaposed to a source material of spodumene and this diffusion couple is subject to the same experimental conditions as the synthesis step. Li abundances and isotopic profiles (ratios of count rates) were analyzed using LA-ICP-MS. Li concentrations linearly decrease away from the source from 550ppm to the average concentration of the starting olivine (2.5ppm). As a function of distance from the source, the 7Li/6Li ratio decreases to a minimum before increasing to the background ratio of the 'dunite rock'. The 7Li/6Li ratio minimum coincides with the lowest Li concentrations above average 'dunite rock' abundances. The initial decrease in the 7Li/6Li ratio is similar to that seen in other studies of diffusive fractionation of isotopes and is thought to be caused by the higher diffusivity (D) of the lighter isotope relative to the heavier isotope. The relationship between D and mass (m) is given by (D1/D2) =(m2/m1)^?, where ? is an empirical fractionation factor; 1 and 2 denote the lighter and heavier isotope, respectively. A fit to the Li isotopic data reveals an effective DLi of ~1.2x10^-12 m/s^2 and a ? of 0.1. Numerical modelling was utilized to elucidate the relationship between diffusive fractionation produced in the grain boundaries versus the lattices of the individual grains of the 'dunite rock'. The model assumes a linear grain boundary juxtaposed to the long side of a rectangular crystal lattice. During a simulation, the diffusant may directly enter the lattice or the grain boundary. Once in the grain boundary, the diffusant may then continue to diffuse away from the source until the end of the simulation or, alternatively, it may be incorporated into the lattice at some point during its travels down the grain boundary. The model system is similar to that considered by Whipple-LeClaire (1963) and our model results agree well with their analytical solution. Preliminary modeling results show that the distinctive minimum in the isotopic ratio is only produced when diffusive fractionation occurs in the grain boundary and not when the fractionation occurs only in the lattice. This suggests that the isotopic profile observed in the experiments may be a product of diffusive fractionation in grain boundaries. Implications of these results extend to the longevity of Li isotopic heterogeneities in the mantle, and suggest that the isotopes of other elements, which have a large relative mass difference, may also be diffusively fractionated by grain boundary diffusion.

Homolova, V.; Watson, E. B.

2012-12-01

260

Abiotic Versus Biotic Weathering Of Olivine As Possible Biosignatures  

NASA Technical Reports Server (NTRS)

We are investigating the weathering of silicate minerals by both purely inorganic, and biologically mediated processes using field-emission scanning electron microscopy (FESEM) and energy dispersive x-ray spectroscopy (EDS). By resolving surface textures and chemical compositions of weathered surfaces at the sub-micron scale we hope to be able to distinguish abiotic from biotic weathering processes and so establish a new biosignature applicable to the study of astromaterials including but not limited to the Martian meteorites. Sterilized olivine grains (San Carlos, Arizona) no more than 1-2 mm in their longest dimension were optically assayed to be uniform in color and free of inclusions were selected as weathering subjects. Prior to all experiments surface morphologies and Fe/Mg ratios were determined for each grain using FE-SEM and EDS. Experiments were divided into two categories abiotic and biotic and were compared with "naturally" weathered samples. For the preliminary experiments, two trials (open and closed to the ambient laboratory environment) were performed under abiotic conditions, and three trials under biotic conditions (control, day 1 and day 2). The open system abiotic trials used sterile grains heated at 98 C and 200 C for both 24 and 48 hours in 1L double distilled de-ionized water. The closed system abiotic trials were conducted under the same conditions but in a sealed two layer steel/Teflon "bomb" apparatus. The biotic trials used sterile grains mounted in a flow-through device attached to a wellhead on the Columbia River aquifer. Several discolored, altered, grains were selected to document "natural" weathering surface textures for comparison with the experimental samples. Preliminary results indicate there are qualitative differences in weathered surface textures among all the designed experiments. The olivine grains in abiotic trials displayed etching, pitting, denticulate margins, dissolution and clay formation. The scale of the features ranged from tens to a few microns with textures that remained relatively sharp and were crystallographically controlled. These results were comparable to that observed in the "naturally" weathered comparison/reference grains. Chemical analysis by EDS indicates these textures correlated with the relative loss of Mg and Fe cations by diffusional processes. In contrast the biotic results indicated changes in the etching patterns on the scale of hundreds of nm, which are neither sharp nor crystallographically controlled (nanoetching). Organisms, organic debris and/or extracellular polymeric substances (biofilm) were often in close proximity or direct contact with the nanoetching. While there are many poorly constrained variables in natural weathering experiments to contend with, such as the time scale, the chemistry of the fluids and degree of biologic participation, some preliminary observations can be made: (1) certain distinct surface textures appear correlated with the specific processes giving rise to these textures; (2) the process of diffusing cations can produce many similar styles of surface textural changes; and (3) the main difference between abiotic and biotically produced weathering is the scale (microns versus nanometers) and the style (crystallographically versus noncrystallographically controlled) of the textural features. Further investigation into nanosize scale surface textures should attempt to quantify both textures and chemical changes of the role of microorganisms in the weathering of silicates. Additional experiments addressing nanoscale textures of shock features for comparison with the current data set.

Longazo, Teresa G.; Wentworth, Susan J.; Clemett, Simon J.; Southam, Gordon; McKay, David S.

2001-01-01

261

Experimental petrology, crystallization history, and parental magma characteristics of olivine-phyric shergottite NWA 1068: Implications for the petrogenesis of ``enriched'' olivine-phyric shergottites  

NASA Astrophysics Data System (ADS)

Northwest Africa (NWA) 1068 is one of the few olivine-phyric shergottites (e.g., NWA 1068, Larkman Nunatak [LAR] 06319, and Roberts Massif [RBT] 04262) that is not depleted in light rare earth elements (LREE). Its REE pattern is similar to that of the basaltic shergottite Shergotty, suggesting a possible connection between the olivine-phyric and the basaltic shergottites. To test this possible link, we have investigated the high-pressure near-liquidus phase equilibria for the NWA 1068 meteorite bulk composition. Our results show that the NWA 1068 bulk composition does not represent an unmodified mantle-derived melt; the olivine and pyroxene in our near-liquidus experiments are more magnesian than in the rock itself, which suggests that NWA 1068 contains cumulate minerals (extra olivine). We have then used these experimental results combined with the pyroxene compositions in NWA 1068 to constrain the possible high-pressure crystallization history of the parental magma. These results suggest that NWA 1068 had a complex polybaric history. Finally, we have calculated a model parental magma composition for the NWA 1068 meteorite. The calculated parental magma is an evolved basaltic composition which is too ferroan to be a primitive melt directly derived from the mantle. We suggest that it ponded and crystallized at approximately the base of the crust. This provided an opportunity for the magma to become contaminated by an ``enriched'' crustal component prior to crystallization. The results and modeling from these experiments are applicable not only to the NWA 1068 meteorite, but also to LAR 06319 and possibly any other enriched olivine-phyric shergottite.

Filiberto, Justin; Musselwhite, Donald S.; Gross, Juliane; Burgess, Katherine; Le, Loan; Treiman, Allan H.

2010-08-01

262

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

263

Diffusion kinetics of Cr in olivine and 53Mn– 53Cr thermochronology of early solar system objects  

Microsoft Academic Search

We have determined the diffusion coefficient of Cr in olivine as function of temperature, oxygen fugacity (fO2), and crystallographic orientation and used these data to develop a quantitative understanding of the resetting of the short-lived 53Mn–53Cr decay system in olivine during cooling within meteorite parent body. The diffusion of Cr in olivine was found to be anisotropic, and effectively independent

Motoo Ito; Jibamitra Ganguly

2006-01-01

264

Space Weathering in Olivine and the Mineralogy of (Some) M-Class Asteroids  

NASA Astrophysics Data System (ADS)

One aspect of space weathering of airless bodies is the production of nanophase iron (npFe0) from Fe bearing silicate minerals. The combined effects of low oxygen fugacity and solar-wind implanted H tend to result in strongly-reduced surfaces that can be chemically activated by heating due to micrometeorite impacts. The mineral kinetics of olivine makes it particularly vulnerable to reduction, decomposition, and npFe0 production. Kohout et al. has recently developed a new method of controlled npFe0 production on olivine powder grains that mimics the essential features of this weathering process and was developed to quantitatively evaluate spectral changes related to space weathering and presence of npFe0. Compared to fresh olivine the treated samples exhibit spectral characteristics of space weathering including spectral darkening, shallowing and attenuation of 1 µm olivine absorption band, and reddening. The attenuation of the 1 µm band significantly shrinks the band FWHM and shifts the much reduced band center to shorter wavelengths around 0.95 µm. These spectral changes are related to increasing amounts of npFe0 and the disruption of the crystal structure of the parent olivine. Significantly, the darkened, reddened, and band attenuated olivine spectra are a close match to a number of M-class asteroids. What is particularly interesting is the match with the weak absorption band near 0.95 µm seen in many M-class asteroids (i.e. 16 Psyche, 22 Kalliope, 55 Pandora to name a few). One of the major issues in asteroid science is the relative scarcity of olivine asteroids (the ”Great Dunite Shortage” coined by Bell et al in Asteroids II). One possibility worth further study is that asteroidal olivine may be hidden by the relative ease with which it weathers. The surface chemical and micrometeorite environment in the asteroid belt may produce over time a spectrum for an olivine-rich surface that is remarkably similar to that of an M-class asteroid.

Britt, Daniel; Kohout, Tomas; Schelling, Patrick; Consolmagno, Guy J.

2014-11-01

265

Temperature-dependent distribution of Cr between olivine and pyroxenes in lherzolite xenoliths  

NASA Astrophysics Data System (ADS)

The temperature effect on the exchange reaction Cr2O3(ol)=Cr2O3(px) was studied for coexisting olivine and both clino and ortho pyroxenes. The distribution of Cr between olivine and clinopyroxene in 31 coarse garnet lherzolites and 10 porphyroclastic garnet lherzolites from kinberlites, and in 17 coarse spinel lherzolites from basalts, obeys a van't Hoff relation (c.f. Stosch 1981) with the Wells two-pyroxene temperature: T(Kelvin)=8,787 (In D Cr+ 2.87) where D Cr(opx/ol)=wt.% Cr(clinopyroxene)/Cr(olivine). An analogous exchange for olivine and orthopyroxene with 0.7 1.6 wt.% Al2O3 in 41 garnet lherzolites from kimberlites shows considerable scatter about the following relation: T(Kelvin)=5,540/(ln D cr+1.86) where D cr(opx/ol)= wt.% Cr(orthopyroxene)/Cr(olivine). Spinel lherzolites and a garnet lherzolite from the Malaita alnöite do not obey the second relation. For orthopyroxene with 2.5 5.1 wt.% Al2O3, D cr(opx/ol) is 1.7 to 3 times higher, and for 0.1 wt.% Al2O3 is 2 times lower than for the garnet lherzolites. Experimental calibration is needed, especially to check the possible effect of Al on D cr(opx/ol).

Hervig, R. L.; Smith, J. V.

1982-12-01

266

The influence of bulk composition and dynamic melting conditions on olivine chondrule textures  

NASA Technical Reports Server (NTRS)

The effects of the bulk composition and the dynamic melting conditions on the texture of olivine chondrules were investigated in a series of heating experiments. It is shown that variations in the olivine chondrule textures can be produced by varying the FeO/(FeO + MgO) ratio between the average Type IA and Type II chondrule compositions, could affect the texture of a chondrule at a constant initial melting temperature and heating time. A range of the heating times and the masses of precursor spheres caused variations in the degree of melting and in chondrule textures. Chondrule textures were distributed on a graph of initial temperatures vs. FeO/(FeO + MgO) ratios as bands parallel to the olivine disappearance curve. This graph could be used to predict chondrule textures from Fe/(FeO + MgO) ratios at specific initial melting temperatures.

Connolly, Harold C., Jr.; Hewins, Roger H.

1991-01-01

267

Peridotite and pyroxenite components in the sources of Grande Comore lavas: evidence from olivine compositions  

NASA Astrophysics Data System (ADS)

Grande Comore (Ngazidja) is the youngest Island of the Comores Archipelego in the Indian Ocean, located in the Somali Basin between Africa and Madagascar. The island formed by two volcanoes. Karthala is an active shield volcano, and La Grille is composed mainly of monogenetic cinder cones. The island represents interaction between a mantle plume and oceanic lithosphere and previous studies suggested, based on the major, trace elements and Sr-Nd-Pb-Os isotopic relationships of the lavas, that the alkali basalts of Karthala reflect mainly plume derived melts, while the basanites of La Grille are the products of interaction of plume melts with the metasomatized oceanic lithosphere. Here we report the chemical composition of olivine phenocrysts of Karthala lavas (5 samples), old Karthala (1) and La Grille (3) that were previously analyzed for their major, trace elements and Sr, Nd, Pb, Os and He isotopic compositions. Olivine phenocrysts from Karthala lavas have higher Mn and Ca, lower Al and slightly lower Ni content compared to olivines from La Grille at similar Mg#. Olivines from ';Old Karthala'are close in composition to those from La Grille and the content of Cr is similar between all three groups. The average Mn/Fe and Ca/Fe ratios of olivines of the samples positive correlate with the Sr-Pb-Os isotope ratios of the corresponding whole rocks, and Karthala has higher values than La Grille. These ratios negatively correlate with Nd-He isotope ratios, as well as with the La/Gd, Gd/Yb and Nb/K of the host lavas. The average Ni/Mg and Al/Mg ratios of the olivines correlate with the isotopic and trace element ratios of the whole rocks as well, but display trends in the opposite direction to the ones observed for Mn/Ca over Fe. Previous studies have proposed that the minor element (Ni, Mn and Ca) composition in olivine can be used to infer the proportions of peridotite vs pyroxenite and thus, the amount of recycled ocean crust in the source lithologies of magmas (Sobolev et al., 2007. The amount of recycled crust in sources of mantle-derived melts. Science, 306, 412-417). The Karthala olivines have high Mn/Fe and Ca/Fe and are similar in composition to olivines in MORB, suggesting 10-35% melt contribution from a pyroxenite source. La Grille and old Karthala olivines, on the other hand, are closer in composition to olivines from the Makapuu stage of the Koolau Island in Hawaii and represent 50-75% pyroxenite-derived melt. However, the Ni/Mg ratios in the Grande Comore lavas are relatively constant, unlike MORB, Koolau and other OIBs. Indeed the pyroxenite, which melts within the lithosphere to contribute to the La Grille and old Karthala lavas, most probably, due to metasomatic processes, differs from asthenospheric pyroxenite, which has been suggested to form by the interaction of recycled oceanic crust and peridotite in a rising plume. Thus, our data indicate that lithospheric pyroxenite formed by metasomatism of the lithospheric mantle can be distinguished from pyroxenite from mantle recycling from olivine phenocryst compositions in OIBs.

Weiss, Y.; Class, C.; Goldstein, S. L.

2013-12-01

268

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

269

Kinetics of evaporation of forsterite and Fe-Mg olivine in vacuum  

NASA Astrophysics Data System (ADS)

Evaporation of forsterite, which plays an important role in chemical and isotope fractionation in the early solar nebula, is governed by surface kinetics strongly affected by surface conditions, such as surface roughness as well as density and orientation of dislocation outcrops. We have revealed anisotropies in evaporation rate and surface microstructure of forsterite and Fe-Mg olivine [1-3]. In order to better understand the kinetics of evaporation of forsteriete and olivine, we carried out experiments in a wider range of temperature and examined evaporation mode on the basis of temperature dependence of evaporation rates and surface microstructures. Experiments were carried out in a vacuum chamber internally heated by W mesh heater. Starting materials are single crystals of synthetic forsterite and natural Fe-Mg olivine (Fo~90), which are cut into crystallographically oriented rectangular parallelepipeds. The experimental temperature in the present and our previous studies ranged from 1300 to 1600 °C for Fe-Mg olivine and from 1500 to 1800 °C for forsterite. Surface microstructures of experimental residues were observed with SEM and EBSD, and face-specific evaporation rates were calculated from sample sizes and weight losses on at least three parallelepipeds with different [001]:[010]:[001] ratios. Development of Fe-Mg zoning due to preferential evaporation of Fe and Fe-Mg lattice diffusion in the sample was taken into consideration in rate estimation for olivine evaporation. The experimental results for both forsterite and olivine experiments demonstrated systematic temperature dependence of anisotropy in evaporation rate: (010)>(001)>(010) above ~1750°C, (001)>(100)>(010) at temperatures between ~1750 and ~1500°C, and (001)>(010)>(100) below ~1500°C. The maximum anistoropy in the evaporation rate is factor of 5 below ~1750°C, but the anisotropy is significantly suppressed above ~1750°C, where the differences among three evaporation rates are within 70% at ~1800°C. These crossovers in evaporation rate were intimately associated with changes in surface microstructures not directly related to surface morphologies originated from dislocation outcrops. Facets of (010) disappear on the (010) surface above ~1750°C, and (100) facets appear on the (100) surface below ~1500°C, which is consistently observed both for forsterite and olivine. The facets observed in SEM were confirmed to be atomistically flat consisting of stacking of layers with one or few unit-cells height through STM observations. On the contrary, non-facetted surfaces were confirmed to be atomistically rough. Therefore, the rate crossovers are attributed to rough-smooth transitions [4-5] at ~1500°C for (100) and at ~1750°C for (010). Such rough-smooth transition for the (001) surface is expected to exist below ~1500°C. The anisotropy in the rough-smooth transition temperature identified for forsterite and olivine cannot be explained solely by the differences in slice energy or attachment energy (anisotropy in bond stength) for the three crystallographic faces [6], which predicts that the transition temperture decreases in the order of (010), (001), and (100). The presence of Fe notably enhances stoichiometric evaporation of Fe-Mg olivine at 1500°C without forming any reaction product [3]. This suggests that stoichiometric evaporation from olivine or congruent evaporation from forsterite is controlled by removal of Mg2+ and Fe2+ from either the M1 or M2 site followed by spontaneous destruction of SiO4 tetrahedron at least above 1500°C, which is required not to result in incongruent evaporation forming enstatite layer. On the contrary, Fe-Mg olivine evaporates nonstoichiometrically to form enstatite at the forsterite surface at ~1300°C (Ozawa and Nagahara, 2002), where removal of Fe2+ or Mg2+ is not the rate-controlling process but Si removal or breaking Si-O bonds governs the overall reaction. The slow removal of Si results in nonstoichiometric evaporation via reaction with olivine residue to produce enstatite on the sur

Ozawa, K.; Nagahara, H.

2009-04-01

270

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

NASA Technical Reports Server (NTRS)

The largest Mars trojan, 5261 Eureka, is one of two prototype "Sa" asteroids in the Bus-Demeo taxonomy. Analysis of its visible/near-IR spectrum 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 micrometers) have enabled us to resolve this ambiguity. The thermal-IR spectrum exhibits strong olivine reststrahlen features consistent with a composition of approximately equals Fo60-70. Laboratory spectra of R chondrites, brachinites, and chassignites are dominated by similar features.

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

2011-01-01

271

Experimental Constraints on Lithium Exchange Between Clinopyroxene, Olivine and Aqueous Fluids at Elevated P and T  

NASA Astrophysics Data System (ADS)

Lithium partitioning has been experimentally determined between clinopyroxene, olivine and hydrous fluid at 800-1100°C and 1 GPa. Experiments were done by equilibrating natural mineral powders with Li-doped fluids in sealed noble metal capsules for durations of 48 to 142 hours. Lithium concentrations were determined in run-product solids using LA-ICPMS, and partition coefficients determined by mass balance. Lithium was found to be more compatible in olivine than clinopyroxene, and both sets of D-values decrease with temperature following the relationships: ln DLicpx/fluid = -7.38(±0.55) + 7.04(±0.66) × 1000/T and ln DLiol/fluid = -5.93(±1.60) + 6.46(±2.09) × 1000/T. Similar slopes indicate that lithium partitioning between olivine and clinopyroxene is independent of temperature, which has been confirmed in experiments containing both these phases. Preliminary experiments examining the effect of REE content and fO2 suggest that DLiol/cpx may be a function of crystal chemistry. Lithium isotope partitioning between clinopyroxene + fluid and olivine + clinopyroxene has also been determined in experiments in which fluids of known isotopic composition were equilibrated with natural cpx and olivine. Run-product solids were analysed by MC-ICPMS and SIMS. The isotopic fractionation between clinopyroxene and fluid at temperatures greater than 900°C is ˜2.5‰ (±2‰) and the measured isotopic exchange between olivine and clinopyroxene is ˜5‰ (±4‰). These results have been supplemented by lithium diffusion measurements done on a natural clinopyroxene at 800-1000°C and in San Carlos olivine at 1000°C. The experiments were conducted in sealed silica tubes with either a LiCl Li-source or NaCl Li- sink and containing solid oxygen buffers. The lithium diffusion coefficient is independent of the diffusion gradient as values are the same if the flux of lithium is into or out of the crystal. Additionally the lithium diffusion coefficient in clinopyroxene appears to be independent of fO2. A single measurement of lithium diffusion in olivine was made and found to be two orders of magnitude slower than for clinopyroxene at similar conditions. Our results indicate that slab-derived fluids migrating by porous flow will rapidly exchange Li with their mantle wall-rock, effectively buffering the fluid composition close to ambient mantle values, and rapidly attenuating the slab Li signature.

Caciagli, N.; Brenan, J.; McDonough, W.; Phinney, D.

2009-05-01

272

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

273

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

274

First finding of burkeite in melt inclusions in olivine from sheared lherzolite xenoliths.  

PubMed

For the first time burkeite was observed as a daughter phase in the melt inclusions in olivine by Raman spectroscopy. The olivine comes from sheared lherzolite xenoliths from the Udachnaya-East kimberlite pipe (Yakutia, Russia). This anhydrous sulfate-carbonate mineral (Na(6)(CO(3))(SO(4))(2)) is generally considered to be a characteristic mineral in saline soils or in continental lacustrine evaporite deposits. Recently, however, this mineral was identified in hydrothermal fluids. Our observations indicate that burkeite can also be formed from a mantle-derived melt. PMID:19058996

Korsakov, Andrey V; Golovin, Alexander V; De Gussem, Kris; Sharygin, Igor S; Vandenabeele, Peter

2009-08-01

275

Solubility of Hydrogen in Olivine as a Function of Pressure and Oxygen Fugacity  

NASA Astrophysics Data System (ADS)

The incorporation of hydrogen into olivine is influenced by many of thermodynamic variables (pressure, temperature, oxygen fugacity, etc.) [1, 2, 3]. Given the strong influence that water has on the melting and mechanical behavior of mantle peridotite, it is necessary to determine the solubility of hydrogen in olivine over the range of chemical environments found in the upper mantle. We present results from new high temperature water-saturated hydration experiments to determine the effect of pressure and oxygen fugacity on hydrogen solubility in San Carlos olivine at upper mantle conditions. Our results indicate that at 1 to 2 GPa varying the fugacity of oxygen between the Fe-FeO and Ni-NiO buffers produces significantly smaller change in the concentration of hydrogen in the olivine than has been found at in previous experiments carried out at 300 MPa. Experiments were carried out in a piston-cylinder device at 1 to 2 GPa and 1200 °C using natural San Carlos olivine as a starting material. The fugacity of oxygen was controlled at Fe-FeO, FeO-Fe3O4 and Ni-NiO using solid buffers. Water content in experimental products was measured by secondary ionization mass spectrometry. Variable duration experiments indicate that hydrogen is homogeneously distributed in the olivine at 12 hrs. Our experimental results indicate that pressure strongly effects water content, in agreement with previous studies. For example, as pressure increases from 1 to 2 GPa, the water content of olivine increases from 32 ± 3 to 78 ± 7 ppm at the Ni-NiO buffer, and from 29 ± 3 to 69 ± 3 ppm at the FeO- Fe3O4 buffer. At each pressure the water content is only weakly affected by changing oxygen fugacity conditions, a result that disagrees with a recent report of a 5 times increase in water content between Fe-FeO and Ni-NiO at 2 GPa [3]. Differences between studies may result from variable degrees of defect equilibration or from differences in measurement techniques. However, when compared with the relationship between olivine water content and fslash O2 determined by [2], data from both this study and [3] suggest that the effect of oxygen fugacity on total water content is significantly weaker at upper mantle pressures than at 300 MPa. [1] Kohlstedt, Keppler, and Rubie (1996) Contrib Mineral Petrol 123:345-357. [2] Bai and Kohlstedt (1993) Phys Chem Minerals 19:460-471. [3] Grant et al. (2007) EPSL, doi:10.1016/j.epsl.2007.06.024

O'Leary, J. A.; Hauri, E. H.; Gaetani, G. A.

2007-12-01

276

Hydration of mantle olivine under variable water and oxygen fugacity conditions  

NASA Astrophysics Data System (ADS)

The incorporation of H into olivine is influenced by a significant number of thermodynamic variables (pressure, temperature, oxygen fugacity, etc.). Given the strong influence that H has on the solidus temperature and rheological behavior of mantle peridotite, it is necessary to determine its solubility in olivine over the range of conditions found in the upper mantle. This study presents results from hydration experiments carried out to determine the effects of pressure, temperature, and the fugacities of H2O and O2 on H solubility in San Carlos olivine at upper mantle conditions. Experiments were carried out at 1-2 GPa and 1,200 °C using a piston-cylinder device. The fugacity of O2 was controlled at the Fe0-FeO, FeO-Fe3O4, or Ni0-NiO buffer. Variable duration experiments indicate that equilibration is achieved within 6 h. Hydrogen contents of the experimental products were measured by secondary ion mass spectrometry, and relative changes to the point defect populations were investigated using Fourier transform infrared spectroscopy. Results from our experiments demonstrate that H solubility in San Carlos olivine is sensitive to pressure, the activity of SiO2, and the fugacities of H2O and O2. Of these variables, the fugacity of H2O has the strongest influence. The solubility of H in olivine increases with increasing SiO2 activity, indicating incorporation into vacancies on octahedral lattice sites. The forsterite content of the olivine has no discernible effect on H solubility between 88.17 and 91.41, and there is no correlation between the concentrations of Ti and H. Further, in all but one of our experimentally hydrated olivines, the concentration of Ti is too low for H to be incorporated dominantly as a Ti-clinohumite-like defect. Our experimentally hydrated olivines are characterized by strong infrared absorption peaks at wavenumbers of 3,330, 3,356, 3,525, and 3,572 cm-1. The heights of peaks at 3,330 and 3,356 cm-1 correlate positively with O2 fugacity, while those at 3,525 and 3,572 cm-1 correlate with H2O fugacity.

Gaetani, Glenn A.; O'Leary, Julie A.; Koga, Kenneth T.; Hauri, Erik H.; Rose-Koga, Estelle F.; Monteleone, Brian D.

2014-02-01

277

1 Thermal diffusivity of olivine single-crystals and polycrystalline 2 aggregates at ambient conditions--a comparison  

E-print Network

1 Thermal diffusivity of olivine single-crystals and polycrystalline 2 aggregates at ambient mantle materials highlights a large 16 scatter of absolute values of thermal diffusivity. In 17. Here 19 we present new thermal diffusivity measurements on San 20 Carlos olivine single crystals

Tommasi, Andrea

278

Noble-metal mineralization in olivine clinopyroxenite within idgimskiy gabbro-peridotite-pyroxenite complex (West Sayan Mountains)  

NASA Astrophysics Data System (ADS)

The study of noble-metal mineralization in olivine clinopyroxenite within idgimsky gabbro- peridotite-pyroxenite complex was carried out. Palladium minerals were identified: palladium telluride and palladium and platinum telluride with mercury impurity. The discovered noble- metal mineralization in olivine clinopyroxenites suggests the presence of perspective low sulfidation platinemetal mineralization in mafic within Verkhne-Amyl ore field.

Cherkasova, T. Y.; Korotchenko, T. V.

2014-08-01

279

Kinetics of the olivine-spinel transformation in subducting lithosphere: experimental constraints and implications for deep slab processes  

Microsoft Academic Search

The persistence of metastable olivine to depths greater than 400 km in subducting slabs has implications for the generation of deep-focus earthquakes, the magnitude of buoyancy forces driving plate motion, and the state of stress in the slab. The depth to which metastable olivine (alpha) can survive in a subduction zone and the depth interval over which transformation to beta-

David C. Rubie; Charles R. Ross II

1994-01-01

280

Grain-size evolution in subducted oceanic lithosphere associated with the olivine-spinel transformation and its effects on rheology  

Microsoft Academic Search

We investigate the role of grain-size reduction during the olivine-spinel transformation on rheological properties of subducting slabs on the basis of a scaling model for microstructural development during nucleation and growth. In this model, the size of spinel grains nucleating at olivine grain boundaries is controlled by the relative rates of nucleation and growth, taking into account the impingement through

Michael R. Riedel; Shun-Ichiro Karato

1997-01-01

281

Space Weathering of Olivine in Lunar Soils: A Comparison to Itokawa Regolith Samples  

NASA Technical Reports Server (NTRS)

Regolith particles from airless bodies preserve a record of the space weathering processes that occurred during their surface exposure history. These processes have major implications for interpreting remote-sensing data from airless bodies. Solar wind irradiation effects occur in the rims of exposed grains, and impact processes result in the accumulation of vapordeposited elements and other surface-adhering materials. The grains returned from the surface of Itokawa by the Hayabusa mission allow the space weathering "style" of a chondritic, asteroidal "soil" to be compared to the lunar case. Here, we present new studies of space-weathered olivine grains from lunar soils, and compare these results to olivine grains from Itokawa. Samples and Methods: We analyzed microtome thin sections of olivine grains from the 20-45 micron fractions of three lunar soils: 71061, 71501 and 10084 (immature, submature and mature, respectively). Imaging and analytical data were obtained using a JEOL 2500SE 200kV field-emission scanning-transmission electron microscope equipped with a thin-window energy-dispersive x-ray spectrometer. Similar analyses were obtained from three Hayabusa olivine grains. Results and Discussion: We observed lunar grains showing a range of solar flare track densities (from <10(exp 9) to approx.10(exp 12)/sq cm). The lunar olivines all show disordered, highly strained, nanocrystalline rims up to 150-nm thick. The disordered rim thickness is positively correlated with solar flare track density. All of the disordered rims are overlain by a Si-rich amorphous layer, ranging up to 50-nm thick, enriched in elements that are not derived from the host olivine (e.g., Ca, Al, and Ti). The outmost layer represents impact-generated vapor deposits typically observed on other lunar soil grains. The Hayabusa olivine grains show track densities <10(exp 10)/sq cm and display disordered rims 50- to 100-nm thick. The track densities are intermediate to those observed in olivines in immature and submature lunar soils and indicate surface exposures of approx. 10(exp 5) years. The outermost few nanometers of the disordered rims on Hayabusa olivines are more Si-rich and Mg- and Fe-depleted relative to the cores of the grains and likely represent a minor accumulation of impact-generated vapors or sputter deposits. Nanophase Fe metal particles are less abundant in the Hayabusa rims compared to the rims on lunar grains. Conclusions: The Hayabusa and lunar olivine grain rims have widths and microstructures consistent with formation from atomic displacement damage from solar wind ions. The space weathering features in the Hayabusa grains are similar to those observed in olivines from immature to submature lunar soils. A major difference, however, is that the Hayabusa grains appear to lack the hypervelocity impact products (melt spherules, thick vapor deposits, and abundant nanophase Fe metal particles) that are common in lunar soil grains with a similar exposure history.

Keller, L. P.; Berger, E. L.

2014-01-01

282

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

NASA Technical Reports Server (NTRS)

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

283

In situ observation of texture development in olivine, ringwoodite, magnesiowqstite and silicate perovskite at high pressure  

E-print Network

perovskite at high pressure H.-R. Wenka,*, I. Lonardellia , J. Pehla , J. Devineb , V. Prakapenkac , G. Shenc, perovskite and magnesiowqstite display transformation textures that are then modified by continuing towards h001i with increasing deformation. Perovskite, transforming from olivine, has a pronounced (100

Shen, Guoyin

284

Moessbauer spectra of olivine-rich achondrites - Evidence for preterrestrial redox reactions  

NASA Technical Reports Server (NTRS)

Moessbauer spectral measurements at 4.2 K were made on several ureilites and the two shergottites found in Antarctica, as well as two ureilite falls, three SNC meteorite falls, and two finds in order to distinguish products of preterrestrial redox reactions from phases formed during oxidative weathering on the earth. The spectra indicated that several ureilites contain major proportions of metallic iron, much of which resulted from preterrestrial carbon-induced reduction of ferrous iron in the outermost 10-100 microns of olivine grains in contact with carbonaceous material in the ureilites. The cryptocrystalline nature of these Fe inclusions in olivine renders the metal extremely vulnerable to aerial oxidation, even in ureilites collected as falls. It is inferred that the nanophase ferric oxides or oxyhydroxides identified in Brachina and Lafayette were produced by terrestrial weather of olivines before the meteorites were found. The absence of goethite in two olivine-bearing Antarctic shergottites suggests that the 2 percent ferric iron determined in their Moessbauer spectra also originated from oxidation on Mars.

Burns, R. G.; Martinez, S. L.

1991-01-01

285

Numerical models of ionic diffusion in one and three dimensions: application to dehydration of mantle olivine  

NASA Astrophysics Data System (ADS)

The hydrogen content of nominally anhydrous minerals is of great interest, because it can influence many physical and mechanical properties of mantle rocks. Moreover, the hydrogen diffusion profiles can be used to constrain timescales related to magma eruptions. Here, we report models of ionic diffusion for trace elements in anisotropic crystals and apply them to hydrogen diffusing out of mantle-derived olivine. We first compare and discuss the characteristics of 1D and 3D models and show that only 3D anisotropic diffusion models can lead to diffusion profiles exhibiting non-equilibrium plateau at the center of the solid along the slowest axis, as measured in natural samples. In a second part, we discuss the differences between hydration and dehydration of olivine for diffusion that is linked to two different atomic sites involved in hydrogen mobility. Finally, we apply our 3D anisotropic model to previous results on mantle-derived olivine from Pali-aike to better characterize diffusion coefficients and their anisotropy that could be relevant for dehydration of olivine. Our results show that dehydration has to be strongly anisotropic, with a fast [100] axis and a significantly slower [001] axis.

Thoraval, Catherine; Demouchy, Sylvie

2014-10-01

286

Fe-Ni Metal and Magnetite Nano-Particles in ``Brown'' Color Olivines from Martian Meteorites  

NASA Astrophysics Data System (ADS)

Our TEM study revealed that brown olivines in Dhofar 019, LAR 06319 and NWA 1950 contained magnetite nano-particles instead of Fe-Ni metal nano-particles. These results indicate that magnetite nano-particles are widely present in martian meteorites.

Kurihara, T.; Mikouchi, T.; Saruwatari, K.; Kameda, J.; Miyamoto, M.

2009-03-01

287

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

288

Structure of the Olivine-Spinel Phase Boundary in the Descending Lithosphere  

Microsoft Academic Search

Seismic evidence shows that the descending lithosphere penetrates the mean depth at which the olivine-spinel phase change occurs. As a result of the low temperature in the sinking lithosphere, the phase boundary will be elevated about 150 km. An analysis is given for the structure of a univariant phase boundary in the presence of flow. The phase boundary is discontinuous

D. L. Turcotte; G. Schubert

1971-01-01

289

Chlorine/Bromine Ratios in Fracture-filling Aqueous Alteration Products in Nakhla Olivine  

NASA Technical Reports Server (NTRS)

The Cl/Br ratios in fracture-filling materials in veins in Nakhla olivine was determined using x-ray microprobe (Br) and EDX (Cl) techniques. The Cl/Br ratio of 55 (standard deviation: 13) shows that the secondary altered material is pristine, extraterrestrial and akin to the Martian soil. Additional information is contained in the original extended abstract.

Sutton, S. R.; Rao, M. N.; Dreibus, G.; McKay, D. S.; Waenke, H.; Wentworth, S.; Newville, M.; Trainor, T.; Flynn, G. J.

2002-01-01

290

Spinel from Apollo 12 Olivine Mare Basalts: Chemical Systematics of Selected Major, Minor, and Trace Elements  

NASA Technical Reports Server (NTRS)

Spinels from Apollo 12 Olivine basalts have been studied by Electron and Ion microprobe techniques. The zoning trends of major, minor and trace elements provide new insights into the conditions under which planetary basalts form. Additional information is contained in the original extended abstract.

Papike, J. J.; Karner, J. M.; Shearer, C. K.; Spilde, M. N.

2002-01-01

291

Petrogenesis of olivine-phyric shergottite Larkman Nunatak 06319: Implications for enriched components in martian basalts  

E-print Network

components in martian basalts Amit Basu Sarbadhikari a , James M.D. Day b,*, Yang Liu a , Douglas Rumble III in mineral and whole-rock chemistry to olivine-phyric shergottite, NWA 1068 and the basaltic shergottite NWA and elevated rare earth element patterns more consistent with the LREE-enriched basaltic shergottites (e

Perfect, Ed

292

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

293

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

294

doi:10.1016/j.gca.2003.08.012 Northwest Africa 773: Lunar mare breccia with a shallow-formed olivine-cumulate  

E-print Network

volcanic components, including a prominent igneous clast lithology. The clast lithology is an olivine-gabbro compositionally to volcanic components in the meteorite. The olivine-gabbro lithology exhibits cumulus textures, including extremely low Eu concentration, that make it a candidate parent melt for the olivine-gabbro

295

Origin of Aristarchus Olivine Deposits Based on M3, WAC, and Diviner Analyses  

NASA Astrophysics Data System (ADS)

The Aristarchus region contains geologically diverse deposits and the Aristarchus impact crater, located on the SE margin of the plateau near the contact between plateau materials and western Procellarum basalts, has exposed materials with variable compositions. Of particular interest is the origin of olivine-bearing deposits that occur on the SE portion of the crater rim and ejecta in association with impact melt [1]. NW portions of the rim and ejecta expose plateau materials and are spectrally dominated by pyroxene in the VNIR. Spectra of the NW rim and ejecta are consistent with a noritic composition and with the inferred origin of the plateau as uplifted upper crust [2,3,4]. Therefore, it is unlikely that the olivine- bearing materials, which exhibit a strong 1 micron olivine absorption and only minor pyroxene contributions, are derived from plateau materials similar to those exposed in the NW portion of the crater. Potential sources of the olivine-bearing material excavated by the impact include western Procellarum basalts or buried material associated with the Marius Hills volcanic complex. Alternatively, the olivine-bearing deposits could be derived from a shallow pluton that is not represented by other surface exposures or could have formed as re-crystallized impact melt. Both the western Procellarum basalts [5,6] and some units associated with the Marius Hills [7] are olivine-bearing. In order to differentiate between these hypotheses, we are integrating spectral data in the UV/VIS (LRO WAC), VIS/NIR (Chandrayaan-1 M3), and TIR (LRO Diviner) to further characterize the assemblages of minerals that occur in association with the olivine-bearing deposits in Aristarchus crater, western Procellarum, and units within the Marius Hills volcanic complex. [1] Mustard et al., 2011, JGR 116. [2] McEwen et al., 1994, Science 266. [3] Lucey et al., 1986, LPSC 16. [4] Chevrel et al., 2009, Icarus 199. [5] Staid and Pieters 2001, JGR. [6] Staid et al., 2011, JGR 116. [7] Besse et al., 2011, JGR 116.

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

2011-12-01

296

Olivine alteration and H2 production in carbonate-rich, low temperature aqueous environments  

NASA Astrophysics Data System (ADS)

Hydrous alteration of olivine is capable of producing molecular hydrogen (H2) under a wide variety of hydrothermal conditions. Although olivine hydrolysis (i.e., serpentinization) has commonly been assessed at elevated temperatures (>100 °C), the nature of these reactions in relation to H2 production at lower temperatures has not been systematically evaluated, especially with regard to carbonate-rich fluids. Specifically, carbonate formation may kinetically infringe on geochemical routes related to serpentinization and H2 production at lower temperatures. Here time-dependent interactions of solid, liquid, and gaseous phases with respect to olivine hydrolysis in a carbonate-rich solution (20 mM HCO3-) at 30, 50 and 70 °C for 315 days is investigated experimentally. Within the first two months, amorphous Si-rich (i.e., talc-like) and carbonate phases precipitated; however, no inhibition of olivine dissolution is observed at any temperature based on surface chemistry analyses. High-resolution surface analyses confirm that precipitates grew as spheroids or vertically to form topographic highs allowing further dissolution of the free olivine surfaces and exposing potential catalysts. Despite no magnetite (Fe3O4) being detected, H2 increased with time in experiments carried out at 70 °C, indicating an alternative coupled route for Fe oxidation and H2 production. Spectrophotometry analyses show that aqueous Fe(II) is largely converted to Fe(III) potentially integrating into other phases such as serpentine and talc, thus providing a viable pathway for H2 production. No increase in H2 production was observed in experiments carried out at 30 and 50 °C supporting observations that incorporation of Fe(II) into carbonates occurred faster than the intertwined processes of olivine hydrolysis and Fe(III) oxidation. Overall, carbonate formation is confirmed to be a major influence related to H2 production in low-temperature serpentinization systems. We studied low temperature aqueous alteration of olivine in carbonate and silica-rich solutions. H2 was formed linearly at 70 °C, probably coupled to Fe(II) oxidation. Gas, liquid and solid phases were studied and coupled to geochemical modeling. Amorphous and microcrystalline talc-like precipitations were formed. Zn concentration in solution is increasing linearly with time and temperature.

Neubeck, Anna; Duc, Nguyen Thanh; Hellevang, Helge; Oze, Christopher; Bastviken, David; Bacsik, Zoltán; Holm, Nils G.

2014-06-01

297

High Melt Porosity in the Lower Oceanic Crust Inferred from Phosphorus Zoning in Olivine  

NASA Astrophysics Data System (ADS)

The canonical view that the lower oceanic crust is composed of cumulates of fractional crystallization has been intensely debated in recent years. Migrating melts, reacting with previously crystallized minerals in the crystal mush, can modify the mineralogy and phase proportions inside the lower crust, as well as the composition of erupted MORB [1]. An extreme product of reactive melt migration was discovered during IODP Legs 304/305 at Atlantis Massif (MAR 30N). In this 1.5 km deep drillhole, there are several sequences of olivine-rich troctolite with ';textbook cumulate texture', which may be associated with the contact of a gabbroic pluton into peridotite [2,3]. While there is little ambiguity about the geological relationships, the exact mechanism for the in-situ reactive transformation of mantle peridotites into lower crustal gabbroic lithologies is still poorly understood. One widespread textural feature in support of the dominant role of reactive melt migration is the occurrence of interstitial and vermicular high-Mg# cpx, which form post-compaction at very low melt porosities. The rare screens of opx-bearing mantle peridotites in this drillhole also preserve evidence for low-porosity replacement of mantle opx by gabbroic cpx [4], with minimal volume change. However, we will show that a significant and possibly the main mass of the olivine crystals in the olivine-rich troctolites do not form at low melt porosities, but instead in a melt-rich local environment. Initially, olivines crystallize as rapidly grown dendrites, which is marked by distinct enrichments of the slowly diffusing element phosphorus. Subsequent slow growth produces the main mass of the otherwise P-free olivine crystal. Our observations on natural basalt-hosted and experimentally grown olivines indicate that strong undercooling in a crystal-poor environment is required for dendrite formation. By extrapolation, this would require a crystal-poor melt lens at the top of an evolving gabbroic intrusion into overlying lithospheric mantle peridotites. Disintegration and partial dissolution of the peridotite minerals can provide the conditions for compositional (rather than thermal) undercooling and promote the rapid growth of new olivines inside the deep melt lens. [1] Lissenberg, C.J. & Dick, H.J.B. (2008) EPSL 271, 311-325. [2] Suhr, G. et al. (2008) G3, doi: 10.1029/2008GC002012. [3] Drouin, M. et al. (2009) Chem. Geol. 264, 71-88. [4] von der Handt, A. & Hellebrand, E. (2010) AGU Fall Meeting abstract.

Hellebrand, E.; Welsch, B. T.; Hammer, J. E.

2013-12-01

298

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

299

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

300

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

301

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

302

Partitioning of Ni between olivine and siliceous eclogite partial melt: experimental constraints on the mantle source of Hawaiian basalts  

NASA Astrophysics Data System (ADS)

Olivine is abundant in Earth’s upper mantle and ubiquitous in basaltic lavas, but rarely occurs in eclogite. Partial melts of eclogite are, therefore, not in equilibrium with olivine, and will react with peridotite as they migrate through the upper mantle. If such melts erupt at Earth’s surface, their compositions will be highly modified and they may be olivine-saturated. We investigated experimentally the reaction between olivine and siliceous eclogite partial melt, and determined element partitioning between olivine and the melt produced by this reaction. Our results demonstrate that mixing of reacted eclogite partial melt with primitive basalt is capable of producing the positive correlation between melt SiO2 content and olivine Ni content observed in some Hawaiian lavas. Experiments were carried out by equilibrating eclogite partial melt or basalt with San Carlos olivine at 1 bar and 1,201 1,350°C. Our results show that eclogite partial melts equilibrated with mantle olivine retain their high SiO2, low FeO and MgO characteristics. Further, olivine-melt partition coefficients for Ni measured in these experiments are significantly larger than for basalt. Mixing of these melts with primitive Hawaiian tholeiitic lavas results in crystallization of high-Ni olivines similar to those in Makapuu-stage Koolau lavas, even though the mixed magmas have only moderate Ni contents. This results from a hyperbolic increase of the Ni partition coefficient with increasing polymerization of the mixed melt. Note that while eclogite partial melt in contact with peridotite will equilibrate with pyroxene as well as olivine, this will have the effect of buffering the activity of SiO2 in the reacted melt at a higher level. Therefore, an eclogite partial melt equilibrated with harzburgite will have higher SiO2 than one equilibrated with dunite, enhancing the effects observed in our experiments. Our results demonstrate that an olivine-free “hybrid” pyroxenite source is not required to explain the presence of high-Ni olivines in Hawaiian lavas and, therefore, indicate that the proportion of eclogite in the Hawaiian plume is less than has been estimated in recent studies.

Wang, Zhengrong; Gaetani, Glenn A.

2008-05-01

303

Rheological feedbacks between hydration, strain localization, and olivine deformation mechanisms in the oceanic lithosphere  

NASA Astrophysics Data System (ADS)

Transform faults in the oceanic lithosphere play a key role in the tectonic water cycle by enabling deep circulation of seawater into the shallow lithosphere. We investigate dredge peridotite mylonite samples from the transform fault section of the Shaka Fracture Zone, Southwest Indian Ridge, in order to evaluate the relationships between hydration state, strain localization, and olivine deformation mechanisms. Initial petrographic analyses reveal growth of hydrous amphibole phases and mineral fluid inclusions, as well as the development of heterogeneous strain localization. To further investigate these features, we performed integrated electron backscatter diffraction and energy dispersive spectroscopy characterization. These analyses constrain the amphibole phase as tremolite and document hydration reaction textures associated with orthopyroxene porphyroclast tails and exsolution lamellae. Additionally, detailed examination of mylonitized zones illustrates systematic relationships between hydrous phase fraction, olivine grain size, and lattice preferred orientation (LPO). In particular, localized grain size reduction and absence of any LPO correlate with high hydrous phase fraction, while relatively coarse grained olivine with strong LPO are found in essentially monomineralic regions, suggesting likely feedbacks between hydration reactions, transitions in olivine deformation mechanisms, and mylonitization. We assess these relationships to develop a conceptual model for the concomitant hydration and deformation of peridotite in the brittle-ductile transition zone and evaluate implications for the rheological evolution of faults in the oceanic lithosphere.; (Left) Electron backscatter diffraction phase map. Blue - Forsterite, Cyan - Tremolite, Green - Opx, Red - Chromite. (Center) Average forsterite grain size and tremolite fraction as functions of position calculated in 50 ?m bins. (Right) M-indices for forsterite and tremolite as functions of position calculated in 50 ?m bins. The strong correlation of forsterite fabric strength with average grain size and tremolite fraction illustrates feedbacks between hydration, strain localization, and olivine deformation mechanisms.

Kohli, A. H.; Warren, J. M.

2012-12-01

304

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. PMID:22912685

ten Berge, Hein F. M.; van der Meer, Hugo G.; Steenhuizen, Johan W.; Goedhart, Paul W.; Knops, Pol; Verhagen, Jan

2012-01-01

305

Chemical zonation in olivine-hosted melt inclusions: A record of syn-eruptive cooling  

NASA Astrophysics Data System (ADS)

During the last few minutes to hours of a volcanic eruption, olivine-hosted melt inclusions (MIs) cool and crystallize olivine on their walls, producing olivine-depleted boundary layers in the melt adjacent to their olivine hosts. Competition between diffusive relaxation of these boundary layers into the centers of the MIs and replenishment of the boundary layers by continued olivine crystallization produces concentration profiles that are preserved in glassy MIs. The concentration profile of a given element in a single MI depends on the diffusion coefficient of the element in the melt, its partition coefficient between melt and olivine, and the growth rate of the olivine. Concentration profiles thus differ from element to element in a single MI, and also from inclusion to inclusion depending on the size of the MI and its thermal history. An implication of this chemical zonation is that analyses of zoned MIs, even if made near the centers of the MIs, will be diffusively fractionated relative to a simple olivine extraction path (i.e., the diffusion of fast-diffusing elements such as Ca can extend to the center of a ~150 ?m radius MI). We have developed a model that uses measured MgO concentration profiles across compositionally zoned, naturally glassy, olivine-hosted MIs to constrain the thermal histories of the MIs in the last few minutes to hours of an eruption. We have applied this model to MIs sampled from three different magmatic settings: (1) glassy rims of pillow basalts sampled from the Siqueiros transform fault; (2) a hornito on Santiago Island, (Galapagos); (3) a lava flow on a submarine flank of Fernandina Island (Galapagos). Cooling rates of five MIs from the Siqueiros transform fault range from ~0.08-3 K/s. Most MIs from this sample suite require two-stage, linear cooling histories from liquidus temperatures to ~1000°C with a slower-cooling first stage followed by a faster-cooling second stage, over a time period of a few minutes to just over one hour. MgO profiles in eight MIs from the subaerial hornito on Santiago Island are well described by single-stage linear cooling histories, with cooling rates ranging from ~1-4 K/s and durations of < 2 mins. MgO profiles in the two MIs so far studied from the submarine Fernandina flow show different behaviors, with one being well described by a single-stage linear cooling history with a cooling rate of ~1 K/s and the other requiring a two-stage cooling history with the lowest recorded cooling rates of the entire sample set (0.02 K/s for ~1 hr, then 0.09 K/s for ~20 mins). The differences in thermal histories determined for the three different magmatic settings may reflect differences in their eruptive styles: The two-stage cooling histories required by most of the submarine MIs could reflect slow cooling of the MIs as they travel through a lava flow or pillow interior followed by rapid quenching of the MIs as the host phenocrysts near the melt-water interface. The short, single-stage cooling histories determined by the model for MIs from a subaerial hornito are consistent with the efficient fragmentation observed during this style of volcanic eruption.

Newcombe, M. E.; Fabbrizio, A.; Zhang, Y.; Ma, C.; Le Voyer, M.; Guan, Y.; Eiler, J. M.; Saal, A. E.; Stolper, E. M.

2013-12-01

306

Potential Temperatures of Sources of MORB, OIB and LIPs Based on AL Partitioning Between Olivine and Spinel  

NASA Astrophysics Data System (ADS)

Knowledge of potential temperatures of convecting mantle is required for the understanding the global processes on the Earth [1]. The common way to estimate these is the reconstruction of primary melt compositions and liquidus temperatures based on the Fe-Mg partitioning between olivine and melt. This approach requires knowledge of the compositions of primitive melts in equilibrium with olivine alone as well as composition of olivine equilibrium with primary melts. This information is in most cases unavailable or of questionable quality. Here we report a new approach to obtain crystallization temperatures of primary melts based on the olivine-spinel Al-Cr geothermometer [2]. The advantages of this approach are: (1) low rate of diffusion of Al in the olivine, which promises to preserve high magmatic temperatures and (2) common presence of spinel in assemblage with high-Mg olivine. In order to decipher influence of elevated Ti concentrations in spinel we have run several experiments at high temperatures (1400-1200 degree C), atmospheric pressure and controled oxygen fugacity. We also analysed over two thousand spinel inclusions and high-Mg host olivines from different MORB, OIB, LIP and Archean komatiites on the JXA-8230 EPMA at ISTerre, Grenoble, France. Concentrations of Al, Ti, Na, P, Zn, Cr, Mn, Ca, Co, Ni were determined with a precision of 10 ppm (2 standard errors) using a newly developed protocol [3]. When available, we also analysed matrix glass and glass inclusions in olivine and found that temperature estimations from olivine-spinel (Al-Cr) and olivine-melt (Fe-Mg) [4] equilibrium match within (+/-30 degree C). The results show contrasting crystallization temperatures of Mg-rich olivine of the same Fo content from different types of mantle-derived magmas, from the lowest (down to 1220 degree C) for MORB to the highest (up to 1550 degree C) for komatiites and Siberian meimechites. These results match predictions from Fe-Mg olivine-melt equilibrium and confirm the relatively low temperature of the convecting mantle source of MORB and higher temperatures in the mantle plumes that produce the OIB of Iceland, Hawaii, Gorgona, Archean komatiites and several LIPs (e.g. Siberian, Decan). [1] McKenzie & Bickle, 1988, J. Petr. 29, p 625-679. [2] Wan et al, 2008, Am. Min. 93, p1142-1147. [3] Batanova & Sobolev, 2013, Min. Mag.,p 667, DOI :10.1180/minmag2013.077.5.2 [4] Ford et al, 1983, J. Petr. 24, p 256-265.

Sobolev, A. V.; Batanova, V. G.; Krasheninnikov, S.; Borisov, A.; Arndt, N.; Kuzmin, D.; Krivolutskaya, N.; Sushevskaya, N.

2013-12-01

307

Mineralogy and Petrology of Amoeboid Olivine Inclusions in CO3 Chondrites: Relationship to Parent-Body Aqueous Alteration  

NASA Technical Reports Server (NTRS)

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 (Fa(sub 0-1)) is systematically converted into ferroan olivine (Fa(sub 60-75)). We infer that the Fe, Si and O entered the assemblage along grain boundaries, forming ferroan olivine that filled fractures and voids. As temperatures increased, Fe(+2) from the new olivine exchanged with Mg(+2) from the original AOI to form diffusive haloes around low-FeO cores. Cations of Mn(+2), Ca(+2) and Cr(+3) were also mobilized. The systematic changes in AOI textures and olivine compositional distributions can be used to refine the classification of CO3 chondrites into subtypes. In subtype 3.0, olivine occurs as small forsterite grains (Fa(sub 0-1)), free of ferroan olivine. In petrologic subtype 3.2, narrow veins of FeO-rich olivine have formed at forsterite grain boundaries. With increasing alteration, these veins thicken to form zones of ferroan olivine at the outside AOI margin and within the AOI interior. By subtype 3.7, there is a fairly broad olivine compositional distribution in the range Fa(sub 63-70), and by subtype 3.8, no forsterite remains and the high-Fa peak has narrowed, Fa(sub 64-67). Even at this stage, there is incomplete equilibration in the chondrite as a whole (e.g., data for coarse olivine grains in Isna (CO3.8) chondrules and lithic clasts show a peak at Fa(sub39)). We infer that the mineral changes in A01 identified in the low petrologic types required aqueous or hydrothermal fluids whereas those in subtypes greater than or equal to 3.3 largely reflect diffusive exchange within and between mineral grains without the aid of fluids.

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

2003-01-01

308

Magnesium isotopes constraints on the origin of Mg-rich olivines from the Allende chondrite: Nebular versus planetary?  

NASA Astrophysics Data System (ADS)

High precision Mg isotope measurements by multi-collector ion microprobe show that refractory olivines from the Allende chondrite, either olivines isolated in the matrix (2 samples studied) or olivines in type I chondrules (6 samples studied), have variable ?26Mg* enrichments and deficits (calculated in permil as the 26Mg deviation from the instrumental mass fractionation line) relative to the Earth. Most average ?26Mg* (noted ?26Mg*av) values (between 10 and 20 analyses per chondrule) are negative but the total range is from -0.029 (± 0.010) ‰ (2 sigma errors) to + 0.011 (± 0.011) ‰ with an exception of one olivine at + 0.043 (± 0.023) ‰. These variations in ?26Mg*av reflect the formation of the olivines from reservoirs enriched in various amounts of 26Mg by the decay of short-lived 26Al (T1/2 = 0.73 Ma). Similarly, 30 analyses of olivines from the Eagle Station pallasite show a ?26Mg*av value of -0.033 ± 0.008‰, as negative as some olivines from Allende chondrules and the Solar system initial ?26Mg* value of -0.038 ± 0.004‰ (defined at the time of formation of type B Ca-Al-rich inclusions - CAIs - when 26Al/27Al = 5.23 × 10-5, Jacobsen et al., 2008). Because olivines are Al-poor and because their Mg isotopic compositions are not reset during the chondrule forming events, their ?26Mg*av can be used to calculate model crystallization ages relative to various theoretical Mg isotope growth curves. The two end-member scenarios considered are (i) a “nebular” growth in which the Al/Mg ratio remains chondritic and (ii) a “planetary” growth in which a significant increase of the Al/Mg ratio can be due to, for instance, olivine magmatic fractionation. The low ?26Mg*av value of olivines from the Eagle Station pallasite demonstrate that metal-silicate differentiation occurred as early as ~ 0. 15- 0. 23+ 0. 29 Ma after CAIs in either of the growth scenarios. Similarly the variable ?26Mg*av values of refractory olivines can be understood if they were formed in planetesimals which started to differentiate as early as the Eagle Station parent body. Accretion of these planetesimals must have been coeval to the formation of CAIs and their disruption could explain why their fragments (Mg-rich olivines) were distributed in the chondrule forming regions of the disk.

Villeneuve, Johan; Chaussidon, Marc; Libourel, Guy

2011-01-01

309

Tranzition zone origins for olivine inclusions in diamond? A multianvil experimental study  

NASA Astrophysics Data System (ADS)

Diamonds and their inclusions are deep Earth probes that record the composition, geochemistry and evolution of Earth's mantle. Studies of mineral inclusions in diamond demonstrate that some diamonds originate in the transition zone and uppermost part of the lower mantle (400 to 700 km). However, it is not possible to determine if inclusions with (Mg,Fe)2SiO4 compositions formed as olivine or the higher-pressure polymorphs wadsleyite and ringwoodite in the transition zone, because the high-pressure mineral structures revert to olivine upon decompression. Chemical fingerprinting appears to be the only way to recognize former single-phase wadsleyite and ringwoodite inclusions in diamond. The crystal chemistry and element partitioning among olivine, wadsleyite and ringwoodite and associated minerals crystallized from fertile peridotite KLB-1 are being studied in multianvil experiments at 10 to 20 GPa and 1300 to 1700°C. Run products contain (Mg,Fe)2SiO4 (55%), garnet/majorite garnet (33%), clinopyroxene/CaSi-perovskite (12%) and a relict Cr-spinel phase (1%), with modal abundances largely remaining constant across the P-T range. The average Mg number for (Mg,Fe)2SiO4 polymorphs decreases with increasing pressure: olivine (90.0), wadsleyite (89.7) and ringwoodite (88.3). The decrease in Mg number between phases is accompanied by an increase in Ni and Ti and a decrease in Mn and Ca. Partition coefficients between wadsleyite and olivine are approximately 3 (Al), 1.5 (Cr), 1.5 (Ti), 1.4 (Na), 1.1 (Ni), 0.9 (Mn) and 0.8 (Ca). Elements such as Al, Cr, Mn, Ca and Na have higher abundances in wadsleyite compared to ringwoodite (DRw/Wad: 2.5 (Ti), 1.2 (Ni), 0.95 (Cr), 0.7 (Al), 0.8 (Na), 0.5 (Mn), and 0.3 (Ca)). The experiments demonstrate that wadsleyite or ringwoodite may be precursor phases for some olivine inclusions in diamond.

Davies, R. M.; Harlow, G. E.

2005-12-01

310

Alteration of Al-rich inclusions inside amoeboid olivine aggregates in the Allende meteorite  

NASA Technical Reports Server (NTRS)

The primary phases of Al-rich inclusions in amoeboid olivine aggregates have undergone alteration reactions with the solar nebular gas. The simplest interpretation of the present observations is that melilite was the first primary phase to disappear with falling temperature, and was replaced by grossular + anorthite + feldspathoids, followed by fassaite; spinel was the last phase to be altered. Thermodynamic calculations suggest that Na-rich phlogopite could have formed at about 470 K and chlorite at about 328 K at a water fugacity of 0.000001, which is that of a gas of solar composition in this temperature range. The olivine around Al-rich inclusions is not serpentized, indicating the cessation of gas-solid equilibrium above 274 K.

Hashimoto, Akihiko; Grossman, Lawrence

1987-01-01

311

Magnetic petrology of eastern North America diabases. I - Olivine-normative dikes from western South Carolina  

NASA Technical Reports Server (NTRS)

The oxide mineralogy and the magnetic behavior of 15 olivine-normative samples obtained from South-Caroline diabase dikes were investigated using electron microprobe and SEM analyses and measurements of natural remanence magnetization (NRM), saturation isothermal remanence magnetization (SIRM), and anhysteritic remanence magnetization. It was found that chromite (which for these olivine-normative diabases is a sensitive petrologic indicator) constitutes up to 0.5 vol pct and that its abundance and composition correlate with bulk rock Cr. Microscopic analyses showed that titanomagnetite compositions were mostly between 0.4 and 0.55. The values of NRM and the NRM/SIRM ratios varied between 4 and 0.01 A sq m/kg and 0.0019 and 0.032, respectively. These properties inversely correlate with Cr content and demonstrably contrast Cr-rich and Cr-poor samples.

Warner, Richard D.; Wasilewski, Peter J.

1990-01-01

312

Morphology of craters generated by hypervelocity impacts of micron-sized polypyrrole-coated olivine particles  

NASA Astrophysics Data System (ADS)

To understand the process of cosmic dust particle impacts and translate crater morphology on smoothed metallic surfaces to dust properties, correct calibration of the experimental impact data is needed. This article presents the results of studies of crater morphology generated by impacts using micron-sized polypyrrole (PPy)-coated olivine particles. The particles were accelerated by an electrostatic dust accelerator to high speeds before they impacted onto polished aluminum targets. The projectile diameter and velocity ranges were 0.3-1.2 ?m and 3-7 km s-1. After impact, stereopair images of the craters were taken using scanning electron microscope and 3-D reconstructions made to provide diameter and depth measurements. In this study, not just the dimensions of crater diameters and depths, but also the shape and dimensions of crater lips were analyzed. The craters created by the coated olivine projectiles are shown to have complicated shapes believed to be due to the nonspherical shape of the projectiles.

Li, Y. W.; Bugiel, S.; Trieloff, M.; Hillier, Jon K.; Postberg, F.; Price, M. C.; Shu, A.; Fiege, K.; Fielding, L. A.; Armes, S. P.; Wu, Y. Y.; Grün, E.; Srama, R.

2014-08-01

313

The Effect of Alkalis and Titanium on the Fe-Mg K(sub D) Between Olivine and Liquid  

NASA Technical Reports Server (NTRS)

Experimental evidence shows that compositional effects on Fe-Mg exchange between olivine and liquid cannot be overlooked. High contents of alkalis and/or titanium decrease K(sub D), in contrast to the weak positive pressure dependence.

Xirouchakis, D.; Hirschmann, M. M.; Draper, D. S.

2000-01-01

314

Melt Inclusions in Olivine-Phyric Shergottite LAR 06319: Important Considerations in Using Melt Inclusions to Retrieve Parent Magmas  

NASA Astrophysics Data System (ADS)

This work focuses on melt inclusions in coarse olivine grains in LAR 06319 which does not have a cumulate component and its melt inclusions present a relatively simple case that allows us to address several methodological issues.

Basu Sarbadhikari, A.; Goodrich, C. A.; Liu, Y.; Taylor, L. A.

2010-03-01

315

An experimental study of trace element partitioning between olivine, orthopyroxene and melt in chondrules - Equilibrium values and kinetic effects  

NASA Technical Reports Server (NTRS)

Mineral/melt partition coefficients were measured using an ion microprobe for 32 elements in orthopyroxene and olivine in equilibrium and dynamic crystallization experiments on compositions corresponding to chondrules. The mineral/melt partition coefficients calculated from the measured concentrations for both olivine and orthopyroxene show very little change between equilibrium experiments and dynamic experiments with cooling rates of up to 100 C/h. The results provide a self-consistent set of partition coefficients that can be used in thermodynamic models of equilibrium and kinetic partitioning between olivine, orthopyroxene, and melt. These data can be used in models of partial melting and crystal fractionation in olivine- and orthopyroxene-rich systems, such as chondrules. The results may also be applicable to mantle peridotites, komatiitic and picritic lavas, and ultramafic intrusions.

Kennedy, A. K.; Lofgren, G. E.; Wasserburg, G. J.

1993-01-01

316

An experimental study of trace element partitioning between olivine, orthopyroxene and melt in chondrules - Equilibrium values and kinetic effects  

NASA Astrophysics Data System (ADS)

Mineral/melt partition coefficients were measured using an ion microprobe for 32 elements in orthopyroxene and olivine in equilibrium and dynamic crystallization experiments on compositions corresponding to chondrules. The mineral/melt partition coefficients calculated from the measured concentrations for both olivine and orthopyroxene show very little change between equilibrium experiments and dynamic experiments with cooling rates of up to 100 C/h. The results provide a self-consistent set of partition coefficients that can be used in thermodynamic models of equilibrium and kinetic partitioning between olivine, orthopyroxene, and melt. These data can be used in models of partial melting and crystal fractionation in olivine- and orthopyroxene-rich systems, such as chondrules. The results may also be applicable to mantle peridotites, komatiitic and picritic lavas, and ultramafic intrusions.

Kennedy, A. K.; Lofgren, G. E.; Wasserburg, G. J.

1993-03-01

317

Effects of chemical environment on the solubility and incorporation mechanism for hydrogen in olivine  

Microsoft Academic Search

To investigate the solubility and the sites of incorporation of hydrogen in olivine as a function of point defect concentration, two-stage high-temperature annealing experiments have been carried out. The first annealing stage (the dry preannealing stage) was conducted at a total pressure of 0.1 MPa, a temperature of 1300° C and various oxygen fugacities in the range 10-11–10-4 MPa for

Quan Bai; D. L. Kohlstedt

1993-01-01

318

Natural Fumarolic Alteration of Fluorapatite, Olivine, and Basaltic Glass, and Implications for Habitable Environments on Mars  

PubMed Central

Abstract Fumaroles represent a very important potential habitat on Mars because they contain water and nutrients. Global deposition of volcanic sulfate aerosols may also have been an important soil-forming process affecting large areas of Mars. Here we identify alteration from the Senator fumarole, northwest Nevada, USA, and in low-temperature environments near the fumarole to help interpret fumarolic and acid vapor alteration of rocks and soils on Mars. We analyzed soil samples and fluorapatite, olivine, and basaltic glass placed at and near the fumarole in in situ mineral alteration experiments designed to measure weathering under natural field conditions. Using synchrotron X-ray diffraction, we clearly observe hydroxyl-carbonate-bearing fluorapatite as a fumarolic alteration product of the original material, fluorapatite. The composition of apatites as well as secondary phosphates has been previously used to infer magmatic conditions as well as fumarolic conditions on Mars. To our knowledge, the observations reported here represent the first documented instance of formation of hydroxyl-carbonate-bearing apatite from fluorapatite in a field experiment. Retreat of olivine surfaces, as well as abundant NH4-containing minerals, was also characteristic of fumarolic alteration. In contrast, alteration in the nearby low-temperature environment resulted in formation of large pits on olivine surfaces, which were clearly distinguishable from the fumarolic alteration. Raman signatures of some fumarolically impacted surfaces are consistent with detection of the biological molecules chlorophyll and scytenomin, potentially useful biosignatures. Observations of altered minerals on Mars may therefore help identify the environment of formation and understand the aqueous history and potential habitability of that planet. Key Words: Fumaroles—Mars—Olivine—Acidophile—Geothermal—Search for life (biosignatures)—Synchrotron X-ray diffraction. Astrobiology 13, 1049–1064. PMID:24283927

Tschauner, Oliver

2013-01-01

319

Diffusion-driven magnesium and iron isotope fractionation in Hawaiian olivine  

USGS Publications Warehouse

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. ?? 2011 Elsevier B.V.

Teng, F.-Z.; Dauphas, N.; Helz, R.T.; Gao, S.; Huang, S.

2011-01-01

320

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

321

Mineralogy and petrology of the diabasic rocks in a differentiated olivine diabase sill complex, Sierra Ancha, Arizona  

Microsoft Academic Search

The Precambrian Sierra Ancha sill complex, more than 700 feet thick, is a multiple intrusion with a central layer of feldspathic olivine-rich diabase, and upper and lower layers of olivine diabase derived from a high-alumina basalt magma. Minor rock types include albite diabase and albite-diabase pegmatite. Deuteric alteration was extensive. Principal primary minerals are plagioclase (An72 to An16), augite (Wo43En44Fs13

Douglas Smith

1970-01-01

322

Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization  

NASA Astrophysics Data System (ADS)

The Lindås Nappe, Bergen Arc, is located in western Norway and displays two high-grade metamorphic structures. A Precambrian granulite facies foliation is transected by Caledonian fluid-induced eclogite-facies shear zones and pseudotachylytes. To understand how a superimposed tectonic event may influence olivine fabric and change seismic anisotropy, two lenses of spinel lherzolite were studied by scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD) techniques. The granulite foliation of the surrounding anorthosite complex is displayed in ultramafic lenses as a modal variation in olivine, pyroxenes, and spinel, and the Caledonian eclogite-facies structure in the surrounding anorthosite gabbro is represented by thin (<1 cm) garnet-bearing ultramylonite zones. The olivine fabrics in the spinel bearing assemblage were E-type and B-type and a combination of A- and B-type lattice preferred orientations (LPOs). There was a change in olivine fabric from a combination of A- and B-type LPOs in the spinel bearing assemblage to B- and E-type LPOs in the garnet lherzolite mylonite zones. Fourier transform infrared (FTIR) spectroscopy analyses reveal that the water content of olivine in mylonite is much higher (approximately 600 ppm H/Si) than that in spinel lherzolite (approximately 350 ppm H/Si), indicating that water caused the difference in olivine fabric. Fabric strength of olivine gets weaker as the grain size reduced, and as a result, calculated seismic properties for the two deformation stages reveal that P- and S-velocity anisotropies are significantly weaker in the mylonite. Microtextures and LPO data indicate that the deformation mechanism changed from dominant dislocation creep in spinel lherzolite to dislocation creep accompanied by grain-boundary sliding in mylonite. Shear localization in the mylonite appears to be originated from the grain size reduction through (1) enhanced dynamic recrystallization of olivine in the presence of water and (2) Zener pinning of clinopyroxene or (3) by ultracomminution during the pseudotachylyte stage.

Jung, Sejin; Jung, Haemyeong; Austrheim, Håkon

2014-12-01

323

Experimental constraints on the partitioning of rhenium and some platinum-group elements between olivine and silicate melt  

NASA Astrophysics Data System (ADS)

We have performed partitioning experiments to assess the role of olivine in controlling the behavior of rhenium and the platinum group elements (PGEs) during basalt petrogenesis. Olivines were crystallized from an iron-bearing basalt at 1 bar (10 5 Pa) and log fO 2 of -2.6, -4.9 and -7.4 (FMQ +4.3, +2 and -0.5, respectively). In situ analyses of olivine and glass by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) reveal a homogeneous distribution of Ru, Rh, Pd, Re, and Pt, but significant Os heterogeneity at the ?m scale. This latter behavior arises from the presence of undissolved Os micronuggets suspended in the melt, and included in olivine crystals. Olivine-melt partition coefficients ( Ds) for Re and the PGEs follow the order: DRh> DRu? DPd˜ DRe˜ DPt. With decreasing fO 2, Rh and Ru become more compatible, with maximum partition coefficients of ˜2.6 and ˜2, respectively, at log fO 2 of -4.9. In contrast, D values for Pd become smaller with decreasing fO 2, to a value of ˜0.006 at log fO 2 of -7.4. Olivine-melt partitioning of Rh, Ru, Pd, Re and Pt derived from our experiments is confirmed by the behavior of these elements in lavas that have evolved by olivine fractionation. An elastic strain model predicts the olivine-melt partitioning of these elements, excepting our measured value of DPt, which is much lower. The fO 2 dependence on partitioning implies that at higher fO 2 some portion of PGEs exist in higher valence states than predicted from their solubility.

Brenan, J. M.; McDonough, W. F.; Dalpé, C.

2003-07-01

324

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

325

STRUCTURE ET ENREGISTREMENT DES TRACES LATENTES D'IONS ARGON ET FER DANS L'OLIVINE ET LE MICA MUSCOVITE  

E-print Network

939 STRUCTURE ET ENREGISTREMENT DES TRACES LATENTES D'IONS ARGON ET FER DANS L'OLIVINE ET LE MICA le mica muscovite. Dans les deux cas, il se forme des zones endommagées qu'on caractérise par leur and Ar ions (energy range : 1-7 MeV/a.m.u.) in olivine and muscovite mica. In both cases, zones

Boyer, Edmond

326

Extracting Olivine (Fo-Fa) Compositions from Raman Spectral Peak Positions  

NASA Technical Reports Server (NTRS)

Olivine and pyroxene are two major basaltic minerals that have been identified at Gusev Crater and Meridiani Planum by the Mars Exploration Rovers. Full petrologic characterization of a sample (rock or soil), however, requires determining the range of mineral compositions, extent of zoning, range of grain sizes, mineral associations, presence of xenocrysts, etc. Information of this sort will aid the interpretation of sample crystallization and differentiation histories and help discriminate between lithologies. In Raman spectroscopic experiments, minerals are identified by their spectral patterns and mineral compositions can be inferred from the peak positions. Instruments currently in use or slated for impending surface exploration missions provide only average elemental compositions for relatively large rock or soil targets or bulk mineral analysis. No techniques currently in use or scheduled for flight can characterize both structure and composition of individual mineral grains, in-situ, like the Mars Microbeam Raman Spectrometer (MMRS). The MMRS is designed to take 100 spectra along a 1 cm linear traverse on the surface of a sample, with contributions from one or a few mineral phases per spectrum. We presented a method to extract structural and compositional information from the Raman spectra of quadrilateral pyroxenes. The pyroxene calibration was applied to a Raman spectroscopic study of Martian meteorite EETA79001 along with a preliminary olivine calibration, where we demonstrated the capability to discriminate related lithologies using Raman point counts. This paper presents an improved olivine calibration that will further aid sample characterization and the study of alteration processes.

Kuebler, K.; Jolliff, B. J.; Wang, Alian; Haskin, L. A.

2005-01-01

327

Synchrotron X-Ray Diffraction Studies of Olivine from Comet Wild 2  

NASA Technical Reports Server (NTRS)

We have analyzed a collection of the Comet Wild 2 coma grains returned by the NASA Stardust Mission, using micro-area Laue diffraction equipment. The purpose of the diffraction experiment is to permit the structure refinement of olivine including site occupancies. In addition to the intrinsic importance of the olivine structures for revealing the thermal history of Wild 2 materials, we wish to test reports that olivine recovered after hypervelocity capture in silica aerogel has undergone a basic structural change due to capture heating [1]. The diffraction equipment placed at beam line BL- 4B1 of PF, KEK was developed with a micropinhole and an imaging plate (Fuji Co. Ltd.) using the Laue method combined with polychromatic X-ray of synchrotron radiation operated at energy of 2.5 GeV. The incident beam is limited to 1.6 m in diameter by a micropinhole set just upstream of the sample [2, 3]. It is essential to apply a microbeam to obtain diffracted intensities with high signal to noise ratios. This equipment has been successfully applied to various extraterrestrial materials, including meteorites and interplanetary dust particles [4]. The Laue pattern of the sample C2067,1,111,4 (Fig. 1) was successfully taken on an imaging plate after a 120 minute exposure (Fig. 2).

2008-01-01

328

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

329

Recycled Crust in the Mantle: Is High-Ni Olivine the Smoking Gun or a Red Herring?  

NASA Astrophysics Data System (ADS)

It is widely accepted that small amounts of recycled crustal components are present in some mantle-derived mafic and ultramafic magmas. This concept is supported by many isotopic and trace element studies of basalts, picrites and komatiites in the last 30 years. Recently Sobolev et al. [1,2] used olivine compositions such as Ni content and Mn/Fe ratio to demonstrate that the amounts of the recycled crustal component (i.e. pyroxenite) in these mantle-derived melts are much larger than previously appreciated. Their calculations show that the pyroxenite-derived component varies mostly between 40 and 80% for Hawaiian shield basalts and Siberian flood basalts, and mostly between 10 and 40% for mid-ocean ridge basalts and Archean komatiities. However, a critical test using olivine-liquid Mg-Fe equilibrium that was overlooked by Sobolev et al. [1,2] reveals that mixing of the two end-members (pyroxenite-derived and peridotite-derived melts) that were used in their models cannot generate the parental melts for the above natural samples. Such a discrepancy prompts us to reexamine the conventional view of a peridotite-dominant source for the Hawaiian shield basalts. This hypothesis has been criticized recently by many people because the contents of Ni in olivine phenocrysts in the basalts are significantly higher than mantle olivines in associated peridotite xenoliths and because total pressure has little effect on olivine-liquid Ni partition coefficient (DNi). What has not been generally considered is that the depth of olivine crystallization/equilibration has a negative effect on olivine Ni content because DNi is negatively correlated with melt temperature which decreases during adiabatic ascent. To evaluate such an effect quantitatively we have used all available experimental results of Ni partitioning between olivine and liquid to construct a robust empirical equation for DNi based on melt composition and temperature. The results of our calculations indicate that the contrasting Ni contents between mantle olivines and olivine phenocrysts in the Hawaiian shield basalts can be explained by variation in their crystallization/equilibration temperatures at different depths. [1] Sobolev et al. (2005) Nature 434, 590-597. [2] Sobolev et al. (2007) Science 316, 412-417.

Li, C.; Ripley, E. M.

2008-12-01

330

Theoretical evaluation of high-energy lithium metal phosphate cathode materials in Li-ion batteries  

Microsoft Academic Search

Lithium metal phosphates (olivines) are emerging as long-lived, safe cathode materials in Li-ion batteries. Nano-LiFePO4 already appears in high-power applications, and LiMnPO4 development is underway. Current and emerging Fe- and Mn-based intercalants, however, are low-energy producers compared to Ni and Co compounds. LiNiPO4, a high voltage olivine, has the potential for superior energy output (>10.7Wh in 18650 batteries), compared with

Wilmont F. Howard; Robert M. Spotnitz

2007-01-01

331

Evidence for heterogeneous enriched shergottite mantle sources in Mars from olivine-hosted melt inclusions in Larkman Nunatak 06319  

NASA Astrophysics Data System (ADS)

Larkman Nunatak (LAR) 06319 is an olivine-phyric shergottite whose olivine crystals contain abundant crystallized melt inclusions. In this study, three types of melt inclusion were distinguished, based on their occurrence and the composition of their olivine host: Type-I inclusions occur in phenocryst cores (Fo 77-73); Type-II inclusions occur in phenocryst mantles (Fo 71-66); Type-III inclusions occur in phenocryst rims (Fo 61-51) and within groundmass olivine. The sizes of the melt inclusions decrease significantly from Type-I (˜150-250 ?m diameter) to Type-II (˜100 ?m diameter) to Type-III (˜25-75 ?m diameter). Present bulk compositions (PBC) of the crystallized melt inclusions were calculated for each of the three melt inclusion types based on average modal abundances and analyzed compositions of constituent phases. Primary trapped liquid compositions were then reconstructed by addition of olivine and adjustment of the Fe/Mg ratio to equilibrium with the host olivine (to account for crystallization of wall olivine and the effects of Fe/Mg re-equilibration). The present bulk composition of Type-I inclusions (PBC1) plots on a tie-line that passes through olivine and the LAR 06319 whole-rock composition. The parent magma composition can be reconstructed by addition of 29 mol% olivine to PBC1, and adjustment of Fe/Mg for equilibrium with olivine of Fo 77 composition. The resulting parent magma composition has a predicted crystallization sequence that is consistent with that determined from petrographic observations, and differs significantly from the whole-rock only in an accumulated olivine component (˜10 wt%). This is consistent with a calculation indicating that ˜10 wt% magnesian (Fo 77-73) olivine must be subtracted from the whole-rock to yield a melt in equilibrium with Fo 77. Thus, two independent estimates indicate that LAR 06319 contains ˜10 wt% cumulate olivine. The rare earth element (REE) patterns of Type-I melt inclusions are similar to that of the LAR 06319 whole-rock. The REE patterns of Type-II and Type-III melt inclusions are also broadly parallel to that of the whole-rock, but at higher absolute abundances. These results are consistent with an LAR 06319 parent magma that crystallized as a closed-system, with its incompatible-element enrichment being inherited from its mantle source region. However, fractional crystallization of the reconstructed LAR 06319 parent magma cannot reproduce the major and trace element characteristics of all enriched basaltic shergottites, indicating local-to-large scale major- and trace-element variations in the mantle source of enriched shergottites. Therefore, LAR 06319 cannot be parental to the enriched basaltic shergottites.

Basu Sarbadhikari, Amit; Goodrich, Cyrena A.; Liu, Yang; Day, James M. D.; Taylor, Lawrence A.

2011-11-01

332

The influence of microstructure on deformation of olivine in the grain-boundary sliding regime  

NASA Astrophysics Data System (ADS)

Although microstructural evolution is critical to strain-dependent processes in Earth's mantle, flow laws for dunite have only been calibrated with low-strain experiments. Therefore, we conducted a series of high-strain torsion experiments on thin-walled cylinders of iron-rich olivine aggregates. Experiments were performed in a gas-medium apparatus at 1200°C and constant strain rate. In our experiments, each at a different strain rate, a peak stress was observed followed by significant strain weakening. We first deformed samples to high enough strain that a steady state microstructure was achieved and then conducted strain rate stepping tests to characterize the creep behavior of each sample with constant microstructure. A global fit to the data yields a stress exponent of 4.1 and a grain-size exponent of 0.73, values which agree well with those from previous small-strain experiments conducted on olivine in the dislocation-accommodated grain-boundary sliding (GBS) regime. Strong crystallographic preferred orientations provide support for GBS accommodated by movement of (010)[100] dislocations. The observed strain weakening is not entirely explained by grain-size reduction; thus, we propose that the remaining 30% reduction in stress is related to CPO development. To incorporate microstructural evolution in a constitutive description of GBS in olivine, we (1) derive a flow law for high-strain deformation with steady state microstructure, which results in an apparent stress exponent of 5.0, and (2) present a system of evolution equations that recreate the observed strain weakening. Our results corroborate flow-law parameters and microstructural observations from low-strain experiments and provide a means for incorporating strain weakening into geodynamic simulations.

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

2012-09-01

333

3D crystal size distributions: A case study on quantifying olivine populations in kimberlites  

NASA Astrophysics Data System (ADS)

New advances in textural analysis and imaging allow the possibility for the true distribution of mineral phases in a rock to be quantified to high resolution. Also we are able to explore the relations between 2D to 3D datasets more rigorously. In this study the application of 2D and 3D textural analysis to the quantification of olivine populations in kimberlites is investigated. Crystal size distribution studies (CSD) are carried out on two kimberlite samples: 1) one from the Venetia K2 kimberlite pipe, South Africa; and 2) one from the Dutoitspan kimberlite pipe, Kimberley, South Africa. A 3D X-ray CT study is undertaken to investigate the application of this developing technique in kimberlite research and to test the 2D and 3D data sets. CSD profiles show markedly curved upwards profiles synonymous with fragmented CSDs, supporting an initial crystal population which is modified by fragmentation of crystals on ascent. Raw plots of 2D area size frequency provide a powerful first estimate of the population 3D statistics in terms of volume size frequency, allowing a quick analysis of olivine phases during exploration which can be quality controlled using more detailed 3D studies where necessary. The 3D data set provides accurate analysis over a range of 6-~0.5 mm, below which the separation of grains becomes very difficult. Additionally the 3D data provides valuable information on crystal shape which can further be used to distinguish different olivine populations. Both 2D and 3D textural studies using state of the art textural analysis techniques have been successfully tested on complex kimberite textures, and will prove useful techniques in the routine quantification of key indicator phases in kimberlite analysis.

Jerram, Dougal A.; Mock, Alex; Davis, Graham R.; Field, Matthew; Brown, Richard J.

2009-11-01

334

Natural fumarolic alteration of fluorapatite, olivine, and basaltic glass, and implications for habitable environments on Mars.  

PubMed

Fumaroles represent a very important potential habitat on Mars because they contain water and nutrients. Global deposition of volcanic sulfate aerosols may also have been an important soil-forming process affecting large areas of Mars. Here we identify alteration from the Senator fumarole, northwest Nevada, USA, and in low-temperature environments near the fumarole to help interpret fumarolic and acid vapor alteration of rocks and soils on Mars. We analyzed soil samples and fluorapatite, olivine, and basaltic glass placed at and near the fumarole in in situ mineral alteration experiments designed to measure weathering under natural field conditions. Using synchrotron X-ray diffraction, we clearly observe hydroxyl-carbonate-bearing fluorapatite as a fumarolic alteration product of the original material, fluorapatite. The composition of apatites as well as secondary phosphates has been previously used to infer magmatic conditions as well as fumarolic conditions on Mars. To our knowledge, the observations reported here represent the first documented instance of formation of hydroxyl-carbonate-bearing apatite from fluorapatite in a field experiment. Retreat of olivine surfaces, as well as abundant NH4-containing minerals, was also characteristic of fumarolic alteration. In contrast, alteration in the nearby low-temperature environment resulted in formation of large pits on olivine surfaces, which were clearly distinguishable from the fumarolic alteration. Raman signatures of some fumarolically impacted surfaces are consistent with detection of the biological molecules chlorophyll and scytenomin, potentially useful biosignatures. Observations of altered minerals on Mars may therefore help identify the environment of formation and understand the aqueous history and potential habitability of that planet. PMID:24283927

Hausrath, Elisabeth M; Tschauner, Oliver

2013-11-01

335

Dielectric constants of tephroite, fayalite and olivine and the oxide additivity rule  

NASA Astrophysics Data System (ADS)

The dielectric constants and dissipation factors of synthetic tephroite (Mn2SiO4), fayalite (Fe3SiO4) and a forsteritic olivine (Mg1.80Fe0.22SiO4) were measured at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: tephroite, ?'a= 8.79 tan ?a = 0.0006 ?'b = 10.20 tan ?b = 0.0006 ?'c= 8.94 tan ?c= 0.0008 fayalite, gk'a = 8.80 tan ?a = 0.0004 gk'b= 8.92 tan ?b = 0.0018 gk'c = 8.58 tan ?c = 0.0010 olivine, gk'a = 7.16 tan ?a = 0.0006 gk'b = 7.61 tan ?b = 0.0008 gk'c = 7.03 tan ?c = 0.0006 The low dielectric constant and loss of the fayalite indicate an exceptionally low Fe3+ content. An FeO polarizability of 4.18 Å3, determined from ?D(FeO) = [?D (Fe2SiO4)-?D(SiO2)]/2, is probably a more reliable value for stoichiometric FeO than could be obtained from FexO where x = 0.90 0.95. The agreement between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to ?D(M2M'X2) = 2?D(MX) + ?D(M'X2) is ˜+2.8% for tephroite and +0.2% for olivine. The deviation from additivity in tephroite is discussed.

Shannon, R. D.; Subramanian, M. A.; Hosoya, S.; Rossman, G. R.

1991-07-01

336

P-rich olivines in a melt vein of a composite mantle xenolith: implications for crystal growth and kinetics  

NASA Astrophysics Data System (ADS)

The mineral chemistry of mantle xenoliths, and in particular the presence of phosphorus (P) - a moderately incompatible and slowly diffusing element - may preserve the history of mineral growth and constrain timescales of pre-eruption petrogenetic processes (Boesenberg & Hewins 2010). P-rich zones in olivine may reflect incorporation of P in excess of equilibrium partitioning during rapid growth, in which case zoning patterns primarily record crystal growth rate variations (Milman-Barris et al. 2008; Stolper et al. 2009). We investigated using EMP analyses and X-ray maps a composite amphibole-bearing, mantle xenolith (sample: Ci-1-196) from Cima Volcanic Field (California, USA) that contains second generation P-rich olivines. The xenolith contains multiple lherzolite, websterite, and dunite layers. The host magma (not preserved in our hand-specimen) is thought to be a hawaiite (Wilshire et al. 1988). A thin (average ~200 ?m width), dark layer is present along the contact between lherzolite and websterite. Interpreted as a rapidly crystallized melt, this layer consists of olivine + glass + plagioclase + spinel + clinopyroxene + apatite + ilmenite. The layer contains olivines (Fo83-89.3) with 0.03-0.52 wt.% P2O5; the P-rich olivines (P2O5 >0.1 wt.%) are Fo85 to Fo89.3. Apatite inclusions are present near the rim of P-rich olivine (Fo85) and in plagioclase (An54). Glass is widespread (~15 vol.%) in the layer, having variable composition with P2O5 up to 1.2 wt.%. Plagioclase occurs as prismatic, flow-oriented crystals, parallel to the elongation of the layer or intergranular crystals between olivine and/or clinopyroxene. Clinopyroxene formed either as crystallized products within the melt layer or by reaction at the interface between melt and matrix olivine. Spinel occurs as inclusions in the olivine or associated with plagioclase and glass, showing anhedral shape and linear edges; spinel composition varies from chromite to Ti-chromite from core to rim, with an outer rim rich in ulvöspinel. Ilmenite occurs as idiomorphic crystals within the layer or as thin rims (

Baziotis, Ioannis; Asimow, Paul D.; Ntaflos, Theodoros; Koroneos, Antonios; Perugini, Diego; Stolper, Edward M.

2014-05-01

337

Dislocation-accommodated grain boundary sliding - from olivine to ice (Invited)  

NASA Astrophysics Data System (ADS)

Dislocation-accommodated grain boundary sliding is likely the dominant mechanism of deformation throughout much of the upper mantle, within major portions of glaciers and ice sheets on Earth, and in icy planetoids. In this creep regime, strain rate depends non-linearly on stress, similar to dislocation creep, and exhibits a marked dependence on grain size, similar to diffusion creep. Furthermore, a strong crystallographic preferred orientation (CPO) develops during deformation in this creep regime. We explored the evolution of rheological behavior and grain-scale microstructure of olivine aggregates in this regime with a series of high-strain torsion experiments on thin-walled cylindrical samples. Hot-pressed specimens with a starting grain size of ~40 ?m were deformed under anhydrous conditions at 1200oC to shear strains of ? > 5 at constant strain rates between 1x10-4 and 3x10-3 s-1. Each sample underwent a period of strain weakening prior to reaching steady-state flow. Post-deformation grain sizes ranged from 27 to 7 ?m with grain size decreasing with increasing strain rate (i.e., with increasing shear stress). All samples exhibited a strong CPO characteristic of dislocation glide on the (010)[100] (easy) slip system. The evolution of stress as a function of strain for each sample is well explained by the combined effects of grain size reduction and CPO development. The stress exponent, n ? 4, and grain size exponent, p ? 1, obtained from the steady-state flow behavior are characteristic of deformation occurring by dislocation-accommodated grain boundary sliding. Observations of dislocation-accommodated grain boundary sliding in olivine are similar to those in other geological materials, indicating that this mechanism is important in a variety of natural environments. For both olivine and ice, extrapolation of the laboratory-derived flow laws for dislocation-accommodated grain boundary sliding, dislocation creep, and diffusion creep indicates that dislocation-accommodated grain boundary sliding is the primary deformation mechanism over a wide range of geological conditions in the mantle as well as in ice sheets, glaciers, and icy satellites. Importantly, the CPOs developed in olivine and ice in the dislocation-accommodated grain boundary sliding regime are similar to those observed in nature, allowing confident extrapolation of our laboratory-derived flow laws to the larger temporal and spatial scales important to modeling the dynamic behavior of planetary interiors and the Earth's cryosphere.

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

2013-12-01

338

Petrography and mineralogy of two basalts and olivine-pyroxene-spinel fragments in achondrite EETA79001  

Microsoft Academic Search

Three lithologies occur in shocked achondrite EETA79001: A1, exotic irregular crystals and clusters of coarse-grained olivine (Fo81-55:CaO 0.2, Cr203 0.06, NiO 0.5 wt.%), low-Ca pyroxene (En82Wo 2 - En58Wo12 ) , and low- Ti chromite (Cr203 59, FeO 27, TiO 2 0.7 wt.%); A2 basaltic host to A1 containing pyroxene (mainly pigeonite En67Wo12 - En52Wo13) , mask- elynite (An61_55Or0.7), high-Ti

Joseph V. Smith; Ian M. Steele

1982-01-01

339

The influence of magma degassing on entrapment pressures recorded in olivine-hosted melt inclusions  

NASA Astrophysics Data System (ADS)

The concentrations of H2O and CO2 in olivine-hosted melt inclusions provide estimates for the pressures at which they were entrapped, and represent an important source of information on the depths at which basaltic magmas crystallize [1]. Results from recent dehydration experiments demonstrate that diffusive loss of H2O from melt inclusions, driven by degassing of the external magma, leads to significant decreases to pressure within the inclusion [2, 3]. This, in turn, lowers the solubility of CO2 in the included melt causing a vapor to exsolve and form a bubble. This process has the potential to significantly modify estimates of entrapment pressures derived from volatile concentrations in olivine hosted melt inclusions. I have developed a quantitative model that describes this process, allowing the influence of degassing on entrapment pressures to be rigorously evaluated. Diffusive loss of H2O from the inclusions was determined using the model of [3]. An equation of state (EOS) for the silicate melt was taken from the results of [4] and [5], while the EOS for H2O-CO2 vapor was taken from [6]. The solubilities of H2O and CO2 in the silicate melt were derived from VolatileCalc [7]. Modeling results demonstrate that degassing of H2O-rich magma produces significant pressure drops, so that entrapment pressures never exceed crustal values and always represent a minimum. Conversely, degassing of H2O-poor magma does not significantly perturb the H2O content of olivine-hosted melt inclusions. Therefore, these inclusions preserve reliable records of the pressures at which they were entrapped. These results are consistent with a global compilation of olivine-hosted melt inclusion entrapment pressures presented by [3]. References: [1] Wanless, VD, and Shaw, AM, Nature Geosci, 5, 651-655 (2012); [2] Gaetani, GA, et al., Geology, 40, 915-918 (2012); [3] Bucholz, CE, et al., Earth Planet Sci Lett, 374, 145-155 (2013); [4] Lange, R. A., and Carmichael, ISE, Geochim Cosmochim Acta, 51, 2931-2946, (1987); [5] Kress, VC, and Carmichael, ISE, Contrib Mineral Petrol, 108, 82-92 (1991); [6] Duan, Z, and Zhang, Z, Geochim Cosmochim Acta, 70, 2311-2324 (2006); [7] Newman, S, and Lowenstern, JB, Comput Geosci, 28, 597-604 (2002).

Gaetani, G. A.

2013-12-01

340

Origin of spinel lamella and/or inclusions in olivine of harzburgite form the Pauza ultramafic rocks from the Kurdistan region, northeastern Iraq  

NASA Astrophysics Data System (ADS)

Exsolution lamellae and octahedral inclusions of chromian spinel occur in olivine of harzburgite of the Pauza ultramafic rocks, Kurdistan region, northeastern Iraq. The lamella is up to 80?m long and up to 50 ?m wide. The lamellae and octahedral inclusions of chromian spinel are distributed heterogeneously in the host olivine crystal. They are depleted in Al2O3 relative to the subhedral spinel grains in the matrix and spinel lamella in orthopyroxene. Olivine (Fo92 - 93) with spinel lamellae occurs as fine-grained crystals around orthopyroxene, whereas olivine (Fo90-91) free from spinel is found in matrix. Based on back-scattered images analyses, enrichments of both Cr # and Fe+3 in the chromian spinel lamella in olivine (replacive olivine) relative to that in adjacent orthopyroxene. As well as the compositions of chromian spinel lamellae host olivine are more Mg-rich than the matrix olivine. Furthermore the restriction of olivine with spinel lamellae and octahedral inclusions on around orthopyroxene, and the similarity of spinel lamella orientations in both olivine and adjacent orthopyroxene. This study concludes that the spinel inclusions in olivine are remnant (inherited from former orthopyroxene) spinel exsolution lamella in orthopyroxene, that has been formed in upper mantle conditions ( T = 1200 °C, P = 2.5 GPa ). Replacive olivine are formed by reaction of ascending silica poor melt and orthopyroxene in harzburgite as pressure decrease the solubility of silica-rich phase (orthopyroxene) in the system increase, therefore ascending melt dissolve pyroxene with spinel exsolution lamella and precipitate replacive olivine with spinel inclusions. We can conclude that the olivines with spinel lamella are not necessary to be original and presenting ultrahigh-pressure and/or ultra deep-mantle conditions as previously concluded. It has been formed by melting of orthopyroxene (orthopyroxene with spinel exsolution lamella = olivine with spinel lamellae and octahedral inclusions + Si-rich melt; 2Mg SiO3= Mg2SiO4+SiO2) in about 700 °C.

Mohammad, Y.; Maekawa, H.; Karim, K.

2009-04-01

341

Catalytic reforming of toluene as tar model compound: effect of Ce and Ce-Mg promoter using Ni/olivine catalyst.  

PubMed

Tar produced by biomass gasification as a route of renewable energy must be removed before the gas can be used. This study was undertaken using toluene as a model tar compound for evaluating its steam reforming conversion with three Ni-based catalysts, Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. Effects of Ce and Mg promoters on the reaction activity and coke deposition were studied. Overall the performance of Ce and Mg promoted Ni/olivine catalysts is better than that of only Ce promoter and Ni/olivine alone. The experimental results indicate that Ni-Ce-Mg/olivine catalysts could improve the resistance to carbon deposition, enhance energy gases yield and resist 10ppm H2S poison at 100mLmin(-1) for up to 400min. Furthermore, the activity of catalysts was related to the steam/carbon (S/C) ratios; at S/C ratio=5, T=790°C, space velocity=782h(-1) and t=2h, the Ni-Ce-Mg/olivine system yielded 89% toluene conversion, 5.6Lh(-1) product gas rate, 62.6mol% H2 content and 10% (mol useful gas mol(-1) toluene) energy yield. Moreover, at low S/C ratio, it had higher reaction activity and better ability to prevent coking. There is a small amount of carbon deposition in the form of amorphous carbon after 7h. Various characterization techniques such as XRD, FTIR and thermogravimetric were performed to investigate the coke deposition of Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. It is suggested that 3% Ni-1% Ce-1% Mg/olivine was the most promising catalyst due to its minimum coke amount and the lower activation energy of coke burning. PMID:24275153

Zhang, Ruiqin; Wang, Huajian; Hou, Xiaoxue

2014-02-01

342

Carbon sequestration via aqueous olivine mineral carbonation: role of passivating layer formation.  

PubMed

CO2 sequestration via carbonation of widely available low-cost minerals, such as olivine, can permanently dispose of CO2 in an environmentally benign and a geologically stable form. We report the results of studies of the mechanisms that limit aqueous olivine carbonation reactivity under the optimum sequestration reaction conditions observed to date: 1 M NaCl + 0.64 M NaHCO3 at Te 185 degrees C and P(CO2) approximately equal to 135 bar. A reaction limiting silica-rich passivating layer (PL) forms on the feedstock grains, slowing carbonate formation and raising process cost. The morphology and composition of the passivating layers are investigated using scanning and transmission electron microscopy and atomic level modeling. Postreaction analysis of feedstock particles, recovered from stirred autoclave experiments at 1500 rpm, provides unequivocal evidence of local mechanical removal (chipping) of PL material, suggesting particle abrasion. This is corroborated by our observation that carbonation increases dramatically with solid particle concentration in stirred experiments. Multiphase hydrodynamic calculations are combined with experimentto better understand the associated slurry-flow effects. Large-scale atomic-level simulations of the reaction zone suggest that the PL possesses a "glassy" but highly defective SiO2 structure that can permit diffusion of key reactants. Mitigating passivating layer effectiveness is critical to enhancing carbonation and lowering sequestration process cost. PMID:16913142

Béarat, Hamdallah; McKelvy, Michael J; Chizmeshya, Andrew V G; Gormley, Deirdre; Nunez, Ryan; Carpenter, R W; Squires, Kyle; Wolf, George H

2006-08-01

343

The effect of pressure on the electrical conductivity of olivine under the hydrogen-rich conditions  

NASA Astrophysics Data System (ADS)

The influence of pressure on the hydrogen-assisted electrical conductivity in olivine has been studied under conditions of 4-10 GPa and 873-1273 K. Synthetic polycrystalline olivine samples with the water content of 160 ppm wt (Paterson calibration) were used and the electrical conductivity was determined from the results of the impedance spectroscopy. We found that the pressure reduces the hydrogen-assisted electrical conductivity, but its magnitude is small: between 4 and 10 GPa, the difference is a factor of ?2.5 for the same water content and temperature. The pressure dependence is characterized by a negative activation volume and the negative dependence of the pre-exponential factor on pressure. Such anomalous behavior is explained by a model where hydrogen-related defect is considered as a weak inclusion in a strong matrix. We use these new data to calculate the electrical conductivity contrast at the 410-km discontinuity. We found that if the water content of the mantle does not change with depth, there should be a large (a factor of ?10) drop in conductivity from above to below the 410-km discontinuity. In contrast, geophysically inferred electrical conductivity increases at 410-km suggesting the increase in water content from above to below the 410-km discontinuity. The present results are used to compare several previous results obtained at different pressures. It was shown that our results agree well with most of previous studies but not with (Yoshino et al., 2009). Possible causes for this discrepancy are discussed.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

344

A Plagioclase-Olivine-Spinel-Magnetite Inclusion from Maralinga (CK): A Record of Sequential Condensation  

NASA Astrophysics Data System (ADS)

An unusual inclusion of triangular cross section (5 mm x 2.5 mm in size) from the Maralinga CK chondrite has a zonal structure, consisting of core, mantle, and crust. The core (2.5 x 1 mm) consists mainly of plagioclase-olivine intergrowth (troctolite) with ophitic texture, but also contains minor clinopyroxene and Cl-apatite, as well as some calcite, which partially fills pore space. The mantle varies in thickness (0.1-1.5 mm) and consists of a dense intergrowth of green spinel and plagioclase with abundant dispersed magnetite grains of widely varying sizes (1-100 micrometer) and shapes. The spinel-plagioclase intergrowth has, in places, symplectitic texture and variable plag/sp ratios and grain-sizes. The mantle is frequently cut by plagioclase-rich veins connecting the core with the crust. Minor phases in the mantle are ilmenite (exsolution lamellae in magnetite) and calcite (in rare pore space). The thin (^about10 micrometer) discontinuous crust consists mainly of plagioclase with some olivine and magnetite and is commonly intimately intergrown with the chondrite matrix. An indentation contains an olivine-plagioclase intergrowth with subophitic texture in places. A super-crust of calcite almost continuously covers the inclusion. Phase compositions, as determined by EMP, are: Olivine - Fa = 33.1, NiO = 0.62 wt%, plagioclase - An 55-74 with high-An compositions in the mantle, clinopyroxene - Fs 10, Wo 46.7, spinel - Fe/Fe+Mg = 0.55, NiO = 1.53 wt%, and magnetite - TiO2 = 0.50 wt%, NiO = 0.57 wt%. Abundances of up to 37 trace elements were determined by secondary ion mass spectrometry[1]. Most phases are rich in trace elements and have group II REE patterns[2] with depletions of the refractory HREEs, a strong positive Tm anomaly and, commonly, a negative Eu anomaly. The exceptions are olivine, which has LREE depletions relative to the HREEs, and calcite, which does not show any significant REE fractionation at the 1xCI abundance level. Thus, trace element abundances in most phases are determined by volatility[3] and not by interphase distribution coefficients, and only olivine appears to have lost the LREEs. This suggests formation of the Maralinga inclusion by condensation from a gas depleted in the superrefractory REEs. Similar patterns have been reported from spinel-hibonite inclusions in Murchison[4], spinel-rich inclusions in Mighei[5], grossite-hibonite inclusions in Acfer 182[6], and spinel inclusions in micrometeorites[7]. The essentially unfractionated REE abundances in calcite must represent an independent reservoir. A search for ^26Al in plagioclase was mostly negative, with only one measurement giving a small ^26Mg excess. The Ti isotope ratios in ilmenite are normal, as expected. The formation history of the inclusion appears to be the following: plagioclase and olivine condensed simultaneously from a gas depleted in superrefractory elements, forming the igneous-looking troctolite core. Plagioclase continued to condense and was joined by spinel and magnetite (or a phase that was subsequently replaced by magnetite). Finally, plagioclase was again joined by olivine, forming the crust. Subsequently, metasomatic exchange reactions under oxidizing conditions in a volatile-rich gas added Fe^2+ and Na (among others) to the phases and led to the formation of phosphate (from phosphide ?) and magnetite (from a reduced precursor ?). Continuing oxidizing conditions caused mobilization of Ca from inside (and probably also outside) the inclusion that precipitated calcite into available pore spaces and at the inclusion's surface. References: [1] Zinner E. and Crozaz G. (1986) Int. J. Mass Spectr. Ion Processes, 69, 17-38. [2] Mason B. and Martin P. M. (1974) Nature, 249, 333-334. [3] Boynton W. V. (1975) GCA, 39, 569-584. [4] Ireland T. R. et al. (1988) GCA, 52, 2841-2854. [5] MacPherson G. J. and Davis A. M. (1994) GCA, 58, 5599-5625. [6] Weber D. et al. (1995) GCA, 59, 803-823. [7] Kurat G. et al. (1994) LPS XXV, 763-764.

Zinner, E.; Brandstatter, F.; Kurat, G.

1995-09-01

345

In situ texture development in dry olivine at upper mantle pressures  

NASA Astrophysics Data System (ADS)

Unresolved issues in geodynamics demand a better understanding of the bulk mechanical properties of mantle minerals, and also careful analysis of the complex lattice-scale physics behind these properties. As olivine is the majority component of the upper mantle, its characterization is particularly important. In the last decade, developments in high-pressure deformation techniques have allowed experimentation at deep upper mantle conditions, with precise measurement of stress from synchrotron x-ray diffraction. These in situ diffraction patterns also contain a wealth of information on evolving sample microstructures, an added benefit that until recently had not been carefully explored. With the use of the mtex toolbox for Matlab and energy-dispersive x-ray diffraction, we have observed the in situ development of lattice preferred orientation in deforming dry San Carlos olivine samples, at pressures from 2-7 GPa. These results suggest active dislocation mechanisms, and a depth for a possible pressure-induced shift in dominant slip system. This technique also demonstrates the promising future of deformation experiments, which will not only explore a broad volume of the earth's interior, but also allow precise measurement of the conditions within deforming samples at the grain scale and below.

Dixon, N. A.; Durham, W. B.; Hunt, S. A.; Homburg, J. M.

2013-12-01

346

Melt migration in a silicate liquid-olivine system: An experimental test of compaction theory  

SciTech Connect

To investigate the kinetics of porous flow in partially molten peridotite, a melt migration couple - formed from a disc of fine-grained olivine plus {approximately}15% of a synthetic K-Al silicate glass and a disc of polycrystalline olivine - was heated at 1,255C under a confining pressure of 300 MPa for 2 hr. Driven by capillary forces, silicate liquid in the source disc infiltrates along three-grain junctions into the sink disc. To analyze the resulting melt migration profile in terms of compaction theory, the equations developed by McKenzie (1984) to describe porous flow of a liquid in a deformable matrix were modified by replacing the buoyancy force term with a capillary force term. The governing equations were then solved numerically with the governing equations were then solved numerically with the initial and boundary conditions specified by the experimental design. Comparison of the melt migration profile obtained from the experiment with those generated by numerical simulation demonstrates that compaction theory provides a good description of the experimental results provided that the permeability of these solid-liquid materials increases linearly with increasing liquid fraction.

Riley, G.N. Jr.; Kohlstedt, D.L. (Univ. of Minnesota, Minneapolis (USA)); Richter, F.M. (Univ. of Chicago, IL (USA))

1990-11-01

347

In-situ X-ray Synchrotron Microtomography: Real Time Pore Structure Evolution during Olivine Carbonation  

NASA Astrophysics Data System (ADS)

Mineral carbonation has been proposed as a promising method for long-term, secure sequestration of carbon dioxide. In porous rocks, fluid-rock interactions can significantly alter the pore space and thus exert important controls over the rate and extent of carbonation. We constructed an x-ray transparent pressure cell [Fusseis et al., 2013] to investigate the real time pore structure evolution during mineral carbonation in porous olivine aggregates. In each experiment, a sintered olivine sample was subjected to a confining pressure of 13 MPa and a pore pressure of 10 MPa, with a sodium bicarbonate solution (NaHCO3 at 1.5 M) as pore fluid. At these pressure conditions, the cell was heated to 473 K. Constant pressure and temperature conditions were maintained during the length of the experiments, lasting 72-120 hours. Using a polychromatic beam in the 2-BM upstream hutch at the Advanced Photon Source, 3-dimensional (3-D) microtomography data were collected in 20 seconds with 30-minute interval. A novel phase retrieval reconstruction algorithm [Paganin et al., 2002] was used to reconstruct microtomographic datasets with a voxel size of ~1.1 micron. The microtomography images at different stages of the carbonation process reveal progressive growth of new crystals in the pore space. Integration of a x-ray transparent pressure vessel with flow through capacity and 3-D microtomography provides a novel research direction of studying the coupled chemo-hydro-thermal-mechanical processes in rocks.

Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xiao, X.

2013-12-01

348

Experimental study of the incorporation of Li, Sc, Al and other trace elements into olivine  

NASA Astrophysics Data System (ADS)

We performed a series of synthesis experiments at 1 atm pressure to investigate the substitution mechanisms of 1+ and 3+ ions into olivine. Forsterite crystals were grown from bulk compositions that contained the element of interest (e.g. Li) and different amounts of additional single trace elements. By working at constant (major element) liquid composition and temperature we eliminated all compositional effects other than those due to the trace elements. Mineral-melt pairs were then analysed to determine the compositional-dependence of the partition coefficient ( D), which corresponds to {[element]}/{[element]}, and where [element] refers to weight concentration of the element in the respective phase. We find that Li forms a stable coupled substitution with Sc and, at above ˜500 ppm Sc in the crystal, Li + and Sc 3+ ions form an ordered neutral complex ([LiSc]). This complex dissociates at lower trace element concentrations and a second, concentration-independent, mechanism begins to dominate. This second solution mechanism is most likely 2Li + ? Mg 2+ where one of the Li atoms is in an interstitial position in the crystal lattice. Natural olivines show Li contents slightly greater than Sc (on an atomic basis), indicating that both substitution mechanisms are significant. Unlike Sc, Al does not appear to form a stable complex with Li in the olivine structure. Sodium is highly incompatible in olivine with DNaFo-melt of ˜0.00015-0.03. Olivine-liquid partitioning of Na + is independent of Sc 3+ or Al 3+ concentration. This indicates that the coupled substitution of Na + with any 3+ ions is unlikely. Instead, the relevant substitution mechanism appears to be 2Na + ? Mg 2+. Although independent of 3+ ion concentration, DNaFo-melt is inversely correlated with the Li concentration of both melts and crystals, implying that Na competes (unsuccessfully) with Li to replace Mg in the olivine structure. Aluminium is highly incompatible in forsterite DAlFo-melt=0.006±0.0005n=7. Values DAlFo-melt of are similar for all phase pairs synthesised from starting materials containing between 10 and 100,000 ppm Al. This suggests that Al is principally incorporated in forsterite by replacing one Mg and one Si atom MgMgx+SiSix?AlMg•+AlSi', where the Al atoms on octahedral (Mg) and tetrahedral (Si) sites are dissociated from one another. The incorporation of gallium into forsterite is influenced by the presence of Li. Where Li concentration in the crystal is much greater than that of Ga (on an atomic basis) we find an excellent correlation between DGaFo-melt and melt Li content. This relationship indicates that Ga 3+ and Li + replace 2Mg 2+ on octahedral sites and that the Ga and Li atoms are, like Sc and Li, strongly associated in the crystal structure. The mechanism by which scandium is incorporated into forsterite is strongly governed by the presence Li. As discussed above, ordered LiMg'ScMg• complexes form readily in forsterite in Li-rich experiments. Under Li-absent but Sc-rich conditions (Sc in the crystal >˜500 ppm), DScFo-melt is proportional to the concentration of Sc in the melt. This indicates that Sc incorporation is charge-balanced by the formation of magnesium vacancies 3MgMgx?2ScMg•+VMg?, and that both species are associated [ScMg•VMg?]. At lower Sc concentrations (<500 ppm in the crystal), the concentration-dependence of partitioning indicates that the ScMg•VMg? complexes dissociate. Our results demonstrate that partitioning of 1+ and 3+ ions into olivine is complex and involves a range of point defects which yield strongly composition-dependent crystal-melt partition coefficients. Since physical and chemical properties of natural olivine, such as diffusion of 6Li and 7Li and H 2O solubility, depend on the concentrations of the defects identified in this study, our results provide an important insight into how determining substitution mechanisms can improve our understanding of large-scale mantle processes and properties.

Grant, Kevin J.; Wood, Bernard J.

2010-04-01

349

Detection of metastable olivine wedge in the western Pacific slab and its geodynamic implications  

NASA Astrophysics Data System (ADS)

Seismic tomography and numerical simulations show that the western Pacific slab bends horizontally when it reaches the boundary between the upper mantle and lower mantle beneath northeast Asia. It is expected that a metastable olivine wedge (MOW) exists in the cold core of the slab because of a delayed phase transition from olivine to its high-pressure polymorphs. However, it is still debated whether the MOW actually exists or not, and even if it exists, its physical properties, such as seismic velocity and density, are still unclear. In this work we use high-quality arrival-time data of 17 deep earthquakes occurring within the Pacific slab under northeast Asia to study the detailed structure of the slab. The deep earthquakes are relocated precisely by applying a modified double-difference location method to arrival-time data recorded at both Chinese and Japanese stations. Based on the precise hypocentral locations, a forward modeling method and differential travel-time residuals data are used to estimate seismic velocity within the deep source zone, which can decrease or remove the influence of ambient velocity heterogeneities. Our results show that the MOW does exist within the Pacific slab under northeast Asia, and the MOW has a mean velocity anomaly of 7-9% lower than the iasp91 Earth model. The existence of MOW in the slab has important geodynamic implications. It can reduce the speed of slab subduction and affect the generation of deep earthquakes.

Jiang, Guoming; Zhao, Dapeng; Zhang, Guibin

2015-01-01

350

Whole-rock 26Al-26Mg systematics of amoeboid olivine aggregates from the oxidized CV3 carbonaceous chondrite Allende  

NASA Astrophysics Data System (ADS)

We report on mineralogy, petrography, and whole-rock 26Al-26Mg systematics of eight amoeboid olivine aggregates (AOAs) from the oxidized CV chondrite Allende. The AOAs consist of forsteritic olivine, opaque nodules, and variable amounts of Ca,Al-rich inclusions (CAIs) of different types, and show evidence for alteration to varying degrees. Melilite and anorthite are replaced by nepheline, sodalite, and grossular; spinel is enriched in FeO; opaque nodules are replaced by Fe,Ni-sulfides, ferroan olivine and Ca,Fe-rich pyroxenes; forsteritic olivine is enriched in FeO and often overgrown by ferroan olivine. The AOAs are surrounded by fine-grained, matrix-like rims composed mainly of ferroan olivine and by a discontinuous layer of Ca,Fe-rich silicates. These observations indicate that AOAs experienced in situ elemental open-system iron-alkali-halogen metasomatic alteration during which Fe, Na, Cl, and Si were introduced, whereas Ca was removed from AOAs and used to form the Ca,Fe-rich silicate rims around AOAs. The whole-rock 26Al-26Mg systematics of the Allende AOAs plot above the isochron of the whole-rock Allende CAIs with a slope of (5.23 ± 0.13) × 10-5 reported by Jacobsen et al. (2008). In contrast, whole-rock 26Al-26Mg isotope systematics of CAIs and AOAs from the reduced CV chondrite Efremovka define a single isochron with a slope of (5.25± 0.01) × 10-5 (Larsen et al. 2011). We infer that the excesses in 26Mg* present in Allende AOAs are due to their late-stage open-system metasomatic alteration. Thus, the 26Al-26Mg isotope systematics of Allende CAIs and AOAs are disturbed by parent body alteration processes, and may not be suitable for high-precision chronology of the early solar system events and processes.

Olsen, M. B.; Krot, A. N.; Larsen, K.; Paton, C.; Wielandt, D.; Schiller, M.; Bizzarro, M.

2011-11-01

351

Influence of Water on Olivine-Wadsleyite Phase Transformation and Water Partitioning near 410-km Seismic Discontinuity  

SciTech Connect

In order to evaluate influence of water on the pressure and transition interval of the olivine-wadsleyite transition, synthesis experiments were carried out in hydrous Forsterite90 composition at 9-16 GPa and 1273-1873 K. Three additional starting materials, representing (a) Mg2SiO4 (b) San-Carlos olivine (Fo89) and (c) CaO-MgO-Al2O3-FeO-SiO2 peridotite, were loaded in every experimental assembly simultaneously. We observed significant expansion of olivine + wadsleyite stability loop to the lower pressure for 2-3 GPa at 1473 K, whereas there was no significant shift of the phase transition boundary at 1873 K. These results are consistent with thermodynamic calculations made by Wood and inconsistent with recent experimental data by Chen et al. We report here preliminary results on water content of coexisting phases. Water solubility of olivine increases with pressure up to 0.15 wt.% H2O at 14 GPa. At 12-15 GPa H2O content of olivine is almost the same at temperatures from 1373 to 1773 K, whereas the H2O content of wadsleyite decreases from about 2.1 wt.% at 1373 K to 0.7 wt.% at 1773 K. We determined the partition coefficient of H2O between two phases. Dwd/ol is 11.8 at 1473 K, 7.2 at 1673 K and 4.5 at 1773 K. However if we apply recent calibration of H2O content in olivine by Bell et al. these Dwd/ol values are three times lower.

Litasov, Konstantin D.; Ohtani, Eiji; Ghosh, Sujoy [Inst. Mineral. Petrol. Geol., Faculty of Science, Tohoku University, Sendai (Japan); Kagi, Hiroyuki [Laboratory for Earthquake Chemistry, Graduate School of Science, University of Tokyo, Tokyo (Japan)

2006-05-15

352

Carbon dioxide sequestration via olivine carbonation: Examining the formation of reaction products  

NASA Astrophysics Data System (ADS)

Due to its abundance and natural ability to sequester CO2, olivine has been proposed as one mineral that could be used in the control of CO2 emissions into the atmosphere (Metz, 2005). Large scale peridotite deposits found in locations such as the Western Gneiss Region in Norway could provide in-situ sites for sequestration or the raw materials for ex-situ mineral carbonation. Determining the conditions under which magnesite (MgCO3) forms most efficiently is crucial to conduct a cost effective process. Understanding the development of secondary minerals is particularly important for in-situ methods as these phases can form passivating layers and affect the host rock porosity. The final solution of flow-through experiments conducted at alkaline pH have been shown to be supersaturated with respect to talc and chrysotile (Giammer et al., 2005), although these phases were not found to have precipitated the formation of a passivating, amorphous silica layer has been observed on reacted olivine surfaces (Bearat et al., 2006). By studying magnesite and other products produced during the carbonation of olivine within Teflon lined steel autoclaves we have begun to form a more comprehensive understanding of how these reactions would proceed during sequestration processes. We have performed batch experiments using carbonated saline solutions in the presence of air or gaseous CO2 from 80 to 200 Ë? C. X-ray powder diffraction was used to identify magnesite within the reaction products. Crystals of magnesite up to 20 m in diameter can be observed on olivine grain surfaces with scanning electron microscopy. Secondary reaction products formed a platy layer on olivine surfaces in reactions above 160 Ë? C and below pH 12. Energy dispersive X-ray analysis of the platy layer revealed an increase in Fe concentration. The macroscopically observable red colouration of the reaction products and Raman spectroscopy indicate that hematite is present in these layers. For experiments with a duration of 4 weeks, lizardite has also been identified using X-ray powder diffraction. The Mg/Si ratio obtained from energy dispersive X-ray analysis of the secondary phases from shorter period experiments indicates that lizardite may also be present. However, the components of these platy layers are closely associated and too low in concentration to be distinguishable with X-ray diffraction analysis. We have not observed the precipitation of talc or chrysotile phases in any of our experiments. Amorphous silica has also not been identified in any of the reaction rims. Higher temperature experiments and those with an initial solution slightly undersaturated with respect to magnesite produced well formed carbonate crystals. The presence of CO2 above the solution did not affect the final magnesite crystal shape but did increase the rate of precipitation. References: Bearat H., McKelvy M. J., Chizmeshya A. V. G., Gormley D., Nunez R., Carpenter R. W., Squires K. and Wolf G. H. (2006), Environ. Sci. Technol., 40 4802-4808. Giammar D. E., Bruant R. G. and Peters C. A. (2005), Chem. Geol., 217 257-276. Metz B. D. O., de Coninck H., Loos M. and Meyer L. (2005), IPCC Special Report on Carbon Dioxide Capture and Storage, Cambridge University Press.

King, H. E.; Plümper, O.; Putnis, A.

2009-04-01

353

Detecting pyroxenite in the genesis of Afar plume lavas using Ni concentrations in olivine  

NASA Astrophysics Data System (ADS)

The lithology of recycled oceanic crust (eclogite) has a profound effect on the composition of mantle-derived lavas. When melts of eclogite react with surrounding peridotitic mantle, solid pyroxenite is formed (Sobolev et al., 2005). Pyroxenite is a clinopyroxene-rich, olivine-poor lithology that, when melted, produces lavas with higher SiO2 and NiO and lower CaO and MnO than are found in peridotite-derived melts (e.g. Kogiso et al., 2004). These chemical signatures are mirrored in the compositions of equilibrium olivine that crystallize from these basaltic lavas. We investigated the role of pyroxenite - and by extension recycled oceanic crust - in the source region for East African Rift System basalts by examining major and minor element concentrations in olivine phenocrysts from high-Ti lavas in northwest Ethiopia that are derived from the Afar plume. Afar plume lavas (87Sr/86Sr ~ 0.7035-0.7040, 143Nd/144Nd ~ 0.51295, and 206Pb/204Pb ~ 18.8) demonstrate a strong contribution from the “C” mantle component (Hanan & Graham, 1996). The high-Ti lavas contain MgO-rich olivine (Fo82-88) with high NiO (0.30-0.48 wt %), low CaO (0.21-0.30 wt %), and low MnO (0.21-0.36 wt %) concentrations. We interpret these compositions as clearly reflecting contributions from melts of a pyroxenite source rock. Interestingly, 187Os/188Os values measured on the Ethiopian high-Ti picrites are only mildly radiogenic (0.125-0.131; Nelson, 2009), inconsistent with the involvement of recycled oceanic crust (187Os/188Os ? 0.15). Isotopic and olivine compositional data can be reconciled by considering the process responsible for generating and melting pyroxenite beneath a thick lithospheric overburden. Sobolev et al. (2007) suggest pyroxenite is generated by the reaction between melts of recycled oceanic crust (eclogite) and solid mantle peridotite. Eclogite entrained in upwelling mantle plumes can melt at greater depths than surrounding peridotite, enabling the solid-liquid reaction. Early mafic melts of the Afar plume were produced in regions of thick lithosphere (>110 km) where peridotite melting may have been suppressed in favor of eclogite melting. In this scenario, melts of eclogite reacted with solid peridotite to form pyroxenite, which subsequently melted more readily than peridotite at depth. The resultant pyroxenite retains most of the isotopic signature of the parent peridotite; this signature is reflected in geochemistry of mafic liquids derived subsequently from the pyroxenite. Therefore, the isotopic signatures of Afar-derived high-Ti mafic lavas do not reflect those of recycled oceanic crust even though this lithology plays an important role in the generation of mantle plume lavas.

Magner, G.; Nelson, W. R.; Furman, T.

2009-12-01

354

Evidence for melt partitioning between olivine and orthopyroxene in partially molten harzburgite  

NASA Astrophysics Data System (ADS)

During melting at mid-ocean ridges, melt is driven into an equilibrium, minimum-energy configuration by surface energy gradients between solid-solid and solid-liquid phase boundaries. Such a configuration, where melt is mostly restricted to three and four-grain junctions, acts as a porous medium through which melt can percolate to the surface. For a monomineralic system, melt is distributed evenly among all grains. However, in mineralogical heterogeneous systems, melt partitions unevenly between the various solid phases to minimize the total energy of the system. In a ocean ridge melting environment, where olivine is often juxtaposed against orthopyroxene (opx), lithologic partitioning is expected to turn olivine-rich regions into high-permeability conduits, through which melt can be quickly extracted, drastically increasing the permeability of the mantle [Zhu and Hirth, 2003]. Lithologic partitioning has been demonstrated in experiments using analogue systems [Watson, 1999]; however, to date, no experiment has confirmed its existence in partially molten mantle systems. We present experimental results that determine the degree of melt partitioning between olivine and opx in partially molten harzburgites. Samples were prepared from a powdered mixture of oxides and carbonates and then hot-pressed in a solid-media piston-cylinder apparatus at 1350°C and 1.5GPa [Zhu et al., 2011] to achieve an 82/18 vol. % ratio of olivine to opx. Prior to hot-pressing, basalt was added to the powdered mixtures in various proportions to test for lithologic partitioning across a range of melt fractions. Three-dimensional, 700nm-resolution images of our samples were obtained using synchrotron X-ray microtomography on the 2BM station of the Advanced Photon Source at Argonne National Labs. Image data were filtered using an anisotropic diffusion filter to enhance phase contrast and then segmented to produce binary representations of each phase. In order to quantitatively demonstrate lithologic melt partitioning in our samples, we digitally segment each grain and then fit a sample window, slightly larger than the grain, to calculate the local melt volume fraction. Our results show strong evidence for lithologic partitioning in partially molten harzburgite systems, in a ~2 to 1 ratio of local melt fraction, between olivine and opx across the range of melt fractions tested. We also present permeability, grain size, and connectivity analyses of our samples in order to evaluate the effects of melt partitioning on melt migration rates at mid-ocean ridges, as well as at other locations in the Earth where partial melting occurs. References Watson, E. B. (1999), Lithologic partitioning of fluids and melts, American Minerologist, 84, 1693-1710. Zhu, W., and G. Hirth (2003), A network model for permeability in partially molten rocks, Earth Planet. Sci. Lett., 212(3-4), 407-416, doi:10.1016/S0012-821X(03)00264-4. Zhu, W., G. A. Gaetani, F. Fusseis, L. G. J. Montési, and F. De Carlo (2011), Microtomography of partially molten rocks: three-dimensional melt distribution in mantle peridotite, Science, 332(6025), 88-91, doi:10.1126/science.1202221.

Miller, K.; Zhu, W.; Montesi, L. G.; Le Roux, V.; Gaetani, G. A.

2013-12-01

355

Solubility of Cr, Ti, and Al in co-existing olivine, spinel, and liquid at 1 atm  

NASA Technical Reports Server (NTRS)

The partitioning of chromium between olivines, spinels and silicate liquids was studied as a function of temperature, oxygen fugacity, and cooling rate between 1175 and 1300 C and redox states near the Fe-FeO buffer. It is found that the weight ratio of Cr2O3 in olivine to that in the liquid increases slightly as oxygen fugacity decreases, but the effect is very small. The cooling experiments showed that the Cr2O3 content does not re-equilibrate with cooling.

Akella, J.; Williams, R. J.; Mullins, O.

1976-01-01

356

Rapid olivine and pyroxene weathering in volcanic plume during the Mount Etna pyroclastic activity (2001)  

NASA Astrophysics Data System (ADS)

Mt. Etna is the most active volcano in Europe and a continuous source of pyroclastic products. In summer 2001 began the most spectacular Etna's eruptive activity in the last 300 years producing an impressive eruptive plume with several million of m3 of volcanic ejecta. Samples of ash collected during the falling of pyroclastic material were separated with sodium metatungstate. Heavy and light fractions have recovered and mounted on slides for optical observations. Selected olivine and pyroxenes were hand-picked and mounted on a stub to Scanning Electron Microscopy observations. On the same minerals Raman spectra spectrum analysis were carried out, both to confirm their chemical nature and to analyse the possible relationship between crystallographic orientation of different faces and dissolution features. Observations at different scales reveal, on selected minerals surfaces, the presence of common corrosion features such as grooves, each pits and irregular shapes with signs of favoured dissolution on particular areas. Chemical analyses carried out by Raman and EDS, confirm the chemical nature of olivine and augite and highlight an intense weathering on particular crystals faces, according to specific crystallographic direction, that is parallel to c axes, in correspondence of cleavages and rim intersection. In particular we have observed well developed etch pits and saw termination in clinopyroxenes, mainly on (001) and (111) faces. Moreover clinopyroxenes have got smooth or not so deeply corroded surfaces on the prismatic faces: (100);(110);(010). Olivines have shown a deeply corrosion on oblique faces respect the c axis and well preserved surfaces, without signs of corrosion, on the prismatic faces parallel to c axis. We interpret these structures as index of chemical and physical alteration processes whose minerals are subject in the volcanic plume, before interaction with seawater or weathering on land. In particular there are clear dissolution features in minerals sites where cations (Ca2+ and Mg2+) can be easily extracted by Cl- and F- into the plume and where cleavages interact, that is in (001) face, in which we can see typical alteration forms such as "sawteeth". The alteration process is thus anisotropic since minerals are undergone to a selective attack on their surface. Knowledge about morphological and chemical features and the dissolution degree of minerals just after their emission, takes a relevant importance if we consider the following environmental dynamics, such as minerals-seawater interactions. In fact it allow us to well understanding the minerals dissolution behaviour and the following trace metal release in marine system.

Antonella Randazzo, Loredana; Andò, Sergio; Censi, Paolo; Zuddas, Pierpaolo; Garzanti, Eduardo

2010-05-01

357

Recycling bacteria for the synthesis of LiMPO4 (M = Fe, Mn) nanostructures for high-power lithium batteries.  

PubMed

In this work, a novel waste-to-resource strategy to convert waste bacteria into a useful class of cathode materials, lithium metal phosphate (LiMPO4; M = Fe, Mn), is presented. Escherichia coli (E. coli) bacteria used for removing phosphorus contamination from wastewater are harvested and used as precursors for the synthesis of LiMPO4. After annealing, LiFePO4 and LiMnPO4 nanoparticles with dimensions around 20 nm are obtained. These particles are found to be enveloped in a carbon layer with a thickness around 3-5 nm, generated through the decomposition of the organic matter from the bacterial cell cytoplasm. The battery performance for the LiFePO4 is evaluated. A high discharge capacity of 140 mAh g(-1) at 0.1 C with a flat plateau located at around 3.5 V is obtained. In addition, the synthesized particles display excellent stability and rate capabilities. Even under a high C rate of 10 C, a stable discharge capacity of 75.4 mAh g(-1) can still be achieved. PMID:24930375

Zhou, Yanping; Yang, Dan; Zeng, Yi; Zhou, Yan; Ng, Wun Jern; Yan, Qingyu; Fong, Eileen

2014-10-15

358

Materials Science and Engineering A 442 (2006) 170174 Contrasting viscoelastic behavior of melt-free and melt-bearing olivine  

E-print Network

-free and melt-bearing olivine: Implications for the nature of grain-boundary sliding Ian Jacksona,, Ulrich H bstract Melt-free and basaltic (complex alumino-silicate) melt-bearing specimens of fine oscillation and microcreep, display markedly different behavior. For the melt-bearing aterials, superimposed

359

Materials Science and Engineering A 442 (2006) 170174 Contrasting viscoelastic behavior of melt-free and melt-bearing olivine  

E-print Network

-free and melt-bearing olivine: Implications for the nature of grain-boundary sliding Ian Jacksona,, Ulrich H Abstract Melt-free and basaltic (complex alumino-silicate) melt-bearing specimens of fine oscillation and microcreep, display markedly different behavior. For the melt-bearing materials, superimposed

360

Distribution of FeO and MgO Between Olivine and Melt in Natural and Experimental Chondrules  

Microsoft Academic Search

FeO and MgO partitioning between olivine and melt for UOC chondrules has been investigated in order to understand their crystallization behavior. In addition, cooling rate experiments on synthetic chondrules have helped define the limits of the Fe-Mg exchange coefficient.

S. J. Symes; G. E. Lofgren

1999-01-01

361

Reply to comment by Nozaka (2014) on “Dehydration breakdown of antigorite and the formation of B-type olivine CPO”  

NASA Astrophysics Data System (ADS)

We would like to thank Dr. Nozaka for his interest in our work and also for supplying some of the crystal orientation data that we used in our study. He presents a detailed discussion of differences in interpretation between our two studies. The main difference is whether the strong B-type olivine CPO developed as a result of topotactic static growth after breakdown of antigorite (Nagaya et al., 2014) or if it developed due to homoepitaxial growth on a limited number of olivine grains that already showed a general B-type CPO (Nozaka, 2014). In both of our studies static growth of olivine due to the breakdown of antigorite is key in the strengthening or formation of B-type olivine CPO. This conclusion has potentially far reaching implications for the interpretation of mantle seismic anisotropy in subduction zones and is the most important take home message. However, the details of interpretation are also important. In our reply, we focus on what we consider to be the 5 main points of disagreement. We refer to Fig. 1 to explain different microstructural domains.

Nagaya, Takayoshi; Wallis, Simon R.; Kobayashi, Hiroaki; Michibayashi, Katsuyoshi; Mizukami, Tomoyuki; Seto, Yusuke; Miyake, Akira; Matsumoto, Megumi

2014-12-01

362

Forsteritic Olivine Grains in Unequilibrated Ordinary Chondrites: Additional Evidence for a Link Between Ordinary and Carbonaceous Chondrites  

NASA Technical Reports Server (NTRS)

We report mineral-chemical and Secondary Ion Mass Spectrometry (SIMS) oxygen-isotopic studies of forsteritic olivine grains from various Unequilibrated Ordinary Chondrites (UOCs). Our studies provide additional evidence for a genetic link between ordinary and carbonaceous chondrites and between various lithologies in these meteorites.

Ruzicka, A.; Hiyagon, H.; Prinz, M.; Taylor, L. A.

2000-01-01

363

QUE97416 and A-88882094, Two CO3 Breccias: Evidence from Petrologic Subtypes Determined from Amoeboid Olivine Inclusions  

NASA Astrophysics Data System (ADS)

AOIs in QUE 97416 and Asuka -882094 have differing ratios of Fe:Mg olivine which seems to indicate a range of subtypes from 3.2 to 3.6. This can be best explained if these meteorites are brecciated representatives of the CO3 parent body asteroid.

Chizmadia, L. J.; Bravo-Ruiz, H.

2012-03-01

364

Characterization of the glide planes of the [001] screw dislocations in olivine using electron tomography  

NASA Astrophysics Data System (ADS)

A San Carlos olivine polycrystal has been deformed under uppermost mantle conditions, by compression at 900 °C, at a strain rate of 1.1 × 10-5 s-1, under a confining pressure of 300 MPa, using the Paterson press. Transmission electron tomography of dislocations has been performed by scanning transmission electron microscopy, by conventional transmission electron microscopy using the weak-beam dark-field technique, associated with precession or not, in order to determine the glide planes of [001] screw dislocations. This recent technique is the most suitable one since most [001] dislocations exhibit straight screw segments due to the high lattice friction on this character at low temperature. We find that [001] dislocations glide in (100), (010) and {110} as already reported, but also more unexpectedly in {120} and {130}. We show that at 900 °C, [001] {110} glide is dominant in polycrystals. We have, however, noted and characterized numerous cross-slip events in the specimen.

Mussi, Alexandre; Cordier, Patrick; Demouchy, Sylvie; Vanmansart, Claude

2014-07-01

365

Crossover of cation partitioning in olivines: a combination of ab initio and Monte Carlo study  

NASA Astrophysics Data System (ADS)

We report studies based on a combination of ab initio electronic structure and Monte Carlo (MC) technique on the problem of 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 structure data. Our results show that there is no reversal of the preference of Fe for M1 over M2 as a function of temperature. Our findings do not agree with the experimental findings of Redfern et al. (Phys Chem Miner 27:630-637, 2000), but are in agreement with those of Heinemann et al. (Eur J Mineral 18:673-689, 2006) and Morozov et al. (Eur J Mineral 17:495-500, 2005).

Chatterjee, Swastika; Bhattacharyya, Sirshendu; Sengupta, Surajit; Saha-Dasgupta, Tanusri

2011-04-01

366

Experimental Studies on Dehydration Embrittlement of Serpentinized Peridotite and Effect of Pressure on Creep of Olivine  

NASA Astrophysics Data System (ADS)

The origin of intermediate depth earthquakes has been debated for 90 years yet is still under active discussion. These earthquakes are localized in double seismic zones in descending lithosphere; both zones originate very close to oceanic trenches. A leading proposed initiation mechanism for these earthquakes since 1968 has been dehydration embrittlement of serpentine under stress. Despite the considerable evidence favoring this mechanism, a major argument against it has been that the lower seismic zone initiates at ˜40 km depth almost immediately below trenches and there does not appear to be a vehicle to carry water sufficiently deep to hydrate otherwise dry lithosphere. To directly address this problem, an experimental study has been carried out to investigate the minimum amount of serpentine that is required to trigger the dehydration embrittlement instability in serpentinized peridotite at high pressure (1-3 GPa) and temperature (720-750?C). The results show that embrittlement occurs during dehydration of antigorite (the phase of serpentine stable at elevated pressure) in a wide range of compositions but both nearly dry peridotite and extensively altered peridotite are ductile. Fresh, unaltered, synthetic harzburgite and harzburgite with 4 vol% distributed antigorite are ductile, as are specimens with greater than 65% antigorite. Only compositions between 8 vol% and 65 vol% antigorite develop the instability. We suggest that very small degrees of serpentinization do not release sufficient H 2O to trigger the instability and that extensive serpentinization avoids the instability because soft, ductile, antigorite becomes the interconnected matrix with olivine and pyroxene existing only as isolated crystals. In that case, dehydration simply facilitates flow. These systematics suggest that small amounts of H2O transported down deep normal (bending) faults at trenches are sufficient to enable the instability in the lower seismic zones, thus providing additional support for dehydration embrittlement as the mechanism of intermediate-depth earthquakes. At the other end of the spectrum of serpentinization, these results are consistent with previous suggestions that extensive dehydration of altered subducting crust and mantle release copious amounts of H2O that rise to the surface of the descending slab and react with the cool mantle of the overlying plate to lead to extensive serpentinization, thereby explaining serpentine diapers in the forearc and lack of seismicity along the plate interface deeper than about 35 km. Another long-lived controversy in mantle geophysics involves the pressure dependence of creep in olivine, the most abundant and softest phase in unaltered mantle rocks. The pressure dependence of any thermodynamically-controlled phenomenon is commonly expressed as the activation volume, DeltaV*. Previous experimental investigations on the effect of pressure on creep in olivine have produced bimodal results. DeltaV* obtained from solid-medium (Griggs) and gas-medium (Paterson) deformation apparatus at relatively lower pressures is ˜15 cm3/mol or higher. In contrast, higher-pressure studies using multianvil apparatus at sites of synchrotron X-radiation (D-DIA apparatus) report a DeltaV* near zero. To decipher this enigma and to provide a much-needed calibration of stress in the D-DIA apparatus, I have conducted systematic experiments on a synthetic, iron-free, forsterite at 1200 ?C and pressure between 1 and 2.5 GPa using the UCR 5 GPa modified Griggs apparatus, the only apparatus capable of performing these experiments. Our results show a robust DeltaV* value of 12 +/- 2 cm3/mol, indicating a fairly significant pressure dependence of creep in olivine to pressures of ˜3 GPa (approximately 100 km). In collaboration with other experimentalists, we plan to measure the DeltaV* for creep of this material over a pressure range of 2-8 GPa in the D-DIA apparatus to both calibrate stress measurement in the D-DIA and resolve the question of change in DeltaV* at higher pressures.

Xia, Gang

367

The primary liquid condensation model and the origin of barred olivine chondrules  

NASA Astrophysics Data System (ADS)

Barred olivine (BO) chondrules are some of the most striking objects in chondrites. Their ubiquitous presence and peculiar texture caught the attention of researchers and, as a consequence, considerable effort has been expensed on unraveling their origin(s). Here we report on a detailed study of two types of chondrules: the Classic and the Multiple-Plate Type of BO chondrules from the Essebi (CM2), Bishunpur (LL3.1), Acfer 214 (CH3) and DAG 055 (C3-UNGR) chondrites, and discuss the petrographic and chemical data of their major mineral phases and glasses. Glasses occur as mesostasis or as glass inclusions, the latter either enclosed inside the olivine bars (plates) or still connected to the mesostasis. The chemical composition of all glasses, characterized by being Si-Al-Ca-rich and free of alkali elements, is similar to those of the constituents (the building blocks, such as chondrules, aggregates, inclusions, mineral fragments, etc.) of CR and CV3 chondrites. They all have high trace element contents ( ˜10×CI) with unfractionated CI-normalized abundances of refractory trace elements and depletions in moderately volatile and volatile elements with respect to the refractory trace elements. The presence of alkali elements (Na + K + Rb) is coupled with a low Ca content and is only observed in those glasses that have behaved as open systems. This result supports the previous finding that Ca was replaced by alkalis (e.g., Na-Ca exchange), presumably through a vapor-solid reaction. The glasses apparently are the quenched liquid from which the olivine plates crystallized. However, they do not show any chemical fractionation that could have resulted from the crystallization of the olivines, but rather have a constant chemical compositions throughout the formation of the chondrule. In a previous contribution we were able to demonstrate the role of these liquids in supporting crystal growth directly from the vapor. Here we extend application of the primary liquid condensation model to formulate a new model for the origin of BO chondrules. The primary liquid condensation model is based on the ability of dust-enriched solar-nebula gas to directly condense into a liquid, provided the gas/dust ratio is sufficiently low. Thus, we propose that chondrules can be formed by condensation of a liquid droplet directly from the solar nebula. The extensive variability in chemical composition of BO chondrules, which ranges from alkali-poor to alkali-rich, can be explained by elemental exchange reactions with the cooling nebula. We calculate the chemical composition of the initial liquid droplet from which BO chondrules could have formed and speculate about the physical and chemical conditions that prevail in the specific regions of the solar nebula that can promote creation of these objects.

Varela, M. E.; Kurat, G.; Zinner, E.

2006-10-01

368

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

NASA Astrophysics Data System (ADS)

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 consequences of replacement of olivine by pyroxene are a significant increase of Ni, Zn and Fe/Mn ratio and decrease in Ca and Sc of pyroxenite-derived melt compared to partial melts from peridotite. The other predicted differences between these lithologies are higher melting rates for pyroxenite than peridotite, and higher Si and lower Mg in pyroxenite-derived melt. We have tested these predictions by experimental melting of a model reaction pyroxenite and use these results along with experimental data for peridotite melting to calculate mixing proportions of melts derived from the two end-member sources (pyroxenite and peridotite) for the olivine datasets representing different geodynamic settings. Olivines from the within plate magmas emplaced on thick (over 70 km) lithosphere (WPM-THICK group of basalts) yield average of around 60 percent of pyroxenite derived component, similar to results derived from Ni data in Hawaiian basalts and olivines only (Sobolev et al, Nature, 2005). The olivines from some continental LIPs (Siberia, Karoo, Etendeka) indicate almost purely pyroxenitic sources. Corresponding results for the other groups are: within plate magmas emplaced on thin (50-10 km) lithosphere (WPM-THIN) 20-30 percent, MORB 5-10 percent. We also note that although MORB contain the lowest proportion of pyroxenite-derived melt (close to zero on average), the spread of MORB data is significant and many samples do contain substantial amounts of pyroxenite derived component. This yields the following average estimates for the amounts of recycled oceanic crust in the mantle sources: few percent for MORB, 10 percent for WPM-THIN group and 15-20 percent for WPM-THICK group. These results suggest that amount of recycled oceanic crust in the convecting mantle is probably high and is likely controlled by the potential mantle temperature which is highest for WPM-THIN and lowest for MORB.

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

2006-12-01

369

Crystallization, melt inclusion, and redox history of a Martian meteorite: Olivine-phyric shergottite Larkman Nunatak 06319  

NASA Astrophysics Data System (ADS)

The Larkman Nunatak (LAR) 06319 olivine-phyric shergottite is composed of zoned megacrysts of olivine (Fo 76-55 from core to rim), pyroxene (from core to rim En 70Fs 25Wo 5, En 50Fs 25Wo 25, and En 45Fs 45Wo 10), and Cr-rich spinel in a matrix of maskelynite (An 52Ab 45), pyroxene (En 30-40Fs 40-55Wo 10-25,), olivine (Fo 50), Fe-Ti oxides, sulfides, phosphates, Si-rich glass, and baddeleyite. LAR 06319 experienced equilibration shock pressures of 30-35 GPa based on the presence of localized shock melts, mechanical deformation of olivine and pyroxene, and complete transformation of plagioclase to maskelynite with no relict birefringence. The various phases and textures of this picritic basalt can be explained by closed system differentiation of a shergottitic melt. Recalculated parent melt compositions obtained from melt inclusions located in the core of the olivine megacrysts (Fo >72) resemble those of other shergottite parent melts and whole-rock compositions, albeit with a lower Ca content. These compositions were used in the MELTS software to reproduce the crystallization sequence. Four types of spinel and two types of ilmenite reflect changes in oxygen fugacity during igneous differentiation. Detailed oxybarometry using olivine-pyroxene-spinel and ilmenite-titanomagnetite assemblages indicates initial crystallization of the megacrysts at 2 log units below the Fayalite-Magnetite-Quartz buffer (FMQ - 2), followed by crystallization of the groundmass over a range of FMQ - 1 to FMQ + 0.3. Variation is nearly continuous throughout the differentiation sequence. LAR 06319 is the first member of the enriched shergottite subgroup whose bulk composition, and that of melt inclusions in its most primitive olivines, approximates that of the parental melt. The study of this picritic basalt indicates that oxidation of more than two log units of FMQ can occur during magmatic fractional crystallization and ascent. Some part of the wide range of oxygen fugacities recorded in shergottites may consequently be due to this process. The relatively reduced conditions at the beginning of the crystallization sequence of LAR 06319 may imply that the enriched shergottite mantle reservoir is slightly more reduced than previously thought. As a result, the total range of Martian mantle oxygen fugacities is probably limited to FMQ - 4 to - 2. This narrow range could have been generated during the slow crystallization of a magma ocean, a process favored to explain the origin of shergottite mantle reservoirs.

Peslier, A. H.; Hnatyshin, D.; Herd, C. D. K.; Walton, E. L.; Brandon, A. D.; Lapen, T. J.; Shafer, J. T.

2010-08-01

370

The role of kinking in plastic deformation of olivine polycraystals: In-situ diffraction and EPSC models  

NASA Astrophysics Data System (ADS)

The mineral olivine is a major component of the upper mantle and since it is weaker than the other major components of the upper mantle, it is generally thought that the rheology of olivine controls flow in the upper mantle. It is therefore problematic that we do not fully understand how an olivine crystal oriented such that there is no resolved shear stress on its available Burgers vectors, manages to accommodate the deformation required of it by its neighbors in the polycrystal. In-situ diffraction during deformation and elastic plastic self-consistent (EPSC) modelling, combined with post-mortem microstructural observations can help to solve this problem. We report here on in-situ synchrotron x-ray diffraction from high pressure deformation experiments conducted using San Carlos and fayalite olivine in the D-DIA apparatus at beamline X17b2 at the NSLS. We observe the diffraction behaviour of x-ray reflections for lattice planes oriented nearly perpendicular to compression and at several other orientations including the transverse orientation. Sample strain is measured using radiographs of the sample (which is bounded by metal foils). We used EPSC modelling to analyse diffraction from the sample collected during deformation. The EPSC model assumes that rheology of the bulk is controlled by the orientation of the grains in the polycrystal and the critical resolved shear stress of the slip systems in the modelled material. The failure of olivine slip systems to meet the von Mesis criteria for arbitrary shape change causes the EPSC models to exhibit very strong work hardening and nearly elastic behaviour for many grain populations. This is in stark contrast to our experimental data which consistently shows little or no work hardening after yield. Building on recent work in our group on kink band formation in olivine, we have introduced unidirectional slip systems into the EPSC model that target the grains in which we observe kink band formation. Inclusion of these slip systems that model kink band formation into our EPSC models dramatically improves the fit of the model to the diffraction data. These results imply that kink band formation is an important accommodation mechanism in plastically deforming olivine and that more effort needs to be devoted to understanding this long overlooked deformation mechanism.

Burnley, P. C.; Cline, C. J.

2012-12-01

371

Chemically fractionated olivine-wadsleyite-ringwoodite assemblages in Grove Mountains meteorites: Constraints on formation mechanism of ringwoodite  

NASA Astrophysics Data System (ADS)

A crucial issue in the olivine (Ol)-ringwoodite (Rgt) transformation mechanisms is whether they formed via incoherent crystallization along grain boundaries or coherent intracrystalline nucleation and growth. Discovery of ringwoodite lamellae in olivine [1,2] was interpreted as evidence for coherent crystallization [1]. However, recent FIB-TEM studies revealed that they are polycrystalline assemblages (incoherent mechanism) [3]. In addition, some ringwoodite show a large compositional gap with coexisting wadsleyite (Wd), suggestive of a new mechanism of fractional crystallization from olivine melts [4,5]. Abundant Ol-Wd-Rgt assemblages were found in heavily shocked L5-6 Grove Mountains (GRV) chondrites. Ringwoodite and coexisting olivine show different compositions and textures, shedding light on Ol-Wd-Rgt transformation mechanism. Here we report textures and compositions of these assemblages from the shock-induced melt vein mainly in GRV 050249 (L5). Ringwoodite in the entrained Ol-Wd-Rgt assemblages occur as: (1) Polycrystalline ringwoodite rims (up to 10?m wide), and polycrystalline ringwoodite rounded or band-like objects inside the fragments. The ringwoodite crystallites (most ~1?m) are Fa36-82 and show 120°triple junctions; the cores of the fragments are Mg-rich (Fa8-14) submicron-sized Ol-Wd coexistence intermingling with the ringwoodite rims. The compositional gap is up to 74 mol% of Fa (the largest value reported), indicative of extreme fractionation (the host rock olivine is homogeneous, Fa24-25); (2) Submicron-sized irregular grains of ringwoodite in the Ol-Wd cores, consisting of Mg-rich lathes (probably wadsleyite) and Fe-rich matrix (probably olivine) with various proportions. The ringwoodite grains are exclusively embedded in the matrix. Repetitions of concentric zoning (Fa13-17 and Fa26-28) were observed on several entrained olivine fragments depicting polycrystalline ringwoodite rims and inclusions. Each zone exhibits different proportions of the Mg-rich lathes and Fe-rich matrix. The sharp boundaries of ringwoodite-rimmed olivine fragments entrained in the melt veins suggest that the whole fragments were not completely molten. This is supported by the repeated concentric zoning of the ringwoodite-bearing olivine grains. However, the huge compositional gap between ringwoodite and olivine indicates crystallization of ringwoodite from liquid of partial melting. The Rgt-Wd-Ol coexistence superimposed on the repeated concentric zoning suggests that crystallization of Rgt-Wd-Ol might postdate than the latter. In addition, The 120°triple junctions of ringwoodite polycrystalline assemblages indicate annealing under high pressure. Detailed information of the assemblages is expected by the going on FIB-TEM work. References: [1] Chen M., et al. 2004. PNAS 101: 15033-15037. [2] Ohtani E., et al. 2004. EPSL 227: 505-515. [3] Chen M., et al. 2007. EPSL 264: 277-283. [4] El Goresy A. 2006. AGU Fall Meeting Abstracts 54: 08. [5] Miyahara M., et al. 2008. PNAS 105: 8542-8547.

Feng, L.; Miyahara, M.; Nagase, T.; Ohtani, E.; Hu, S.; Lin, Y.

2009-12-01

372

Trace element partitioning in lamproitic magmas—the Gaussberg olivine leucitite  

NASA Astrophysics Data System (ADS)

Partition coefficients for compatible and incompatible trace elements for use in modelling the origin and evolution of lamproitic and other potassic rocks are reported. These are based on values obtained by in situ determination using laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) on mineral/glass pairs in examples of the Gaussberg olivine leucitite, a classic leucite lamproite. Leucite/melt partition coefficients for 32 elements show values above 1 only for Cs and Rb, whereas values for Ni, Ga and Co are 0.4-0.1. DLc/Lq for most other elements are in the range 0.07-0.0005, and delineate a gently sloping pattern to lower values for elements generally considered to be "incompatible". Olivine/melt partition coefficients show higher values for the compatible elements Ni, Co, Mn and Cr than in all basaltic systems investigated experimentally to date. DOl/Lq for heavy rare earth elements (HREE) are slightly lower than in basalts, whereas most other elements give similar values. Clinopyroxene/melt partition coefficients appear to vary widely as a function of the Al 2O 3 content of the rock. Values obtained here for the Gaussberg rock consistently show appreciably higher DCpx/Lq than in basaltic systems for the incompatible elements Cs, Rb, Ba, Th, U, Nb, Ta, La and Ce, which is attributed to a larger M2 site. Early salitic cores have patterns with lower D-values for these elements and higher values for HREE, similar to those known from alumina-rich potassic rocks. Thus, the values obtained here should be applied only with caution to nonlamproitic rocks. Other notable characteristics are high DU/ DTh and low DZr and DHf, the latter of which is attributed to structural characteristics of peralkaline melts.

Foley, Stephen F.; Jenner, George A.

2004-07-01

373

Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C  

PubMed Central

Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine. The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution. It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies. PMID:21707970

2011-01-01

374

Deformation of olivine under mantle conditions: An in situ high-pressure, high-temperature study using monochromatic synchrotron radiation  

SciTech Connect

Polycrystalline samples of San Carlos olivine were deformed at high-pressure (2.8-7.8 GPa), high-temperature (1153 to 1670 K), and strain rates between 7.10{sup -6} and 3.10{sup -5} s{sup -1}, using the D-DIA apparatus. Stress and strain were measured in situ using monochromatic X-rays diffraction and imaging, respectively. Based on the evolution of lattice strains with total bulk strain and texture development, we identified three deformation regimes, one at confining pressures below 3-4 GPa, one above 4 GPa, both below 1600 K, and one involving growth of diffracting domains associated with mechanical softening above {approx}1600 K. The softening is interpreted as enhanced grain boundary migration and recovery. Below 1600 K, elasto-plastic self-consistent analysis suggests that below 3-4 GPa, deformation in olivine occurs with large contribution from the so-called 'a-slip' system [100](010). Above {approx}4 GPa, the contribution of the a-slip decreases relative to that of the 'c-slip' [001](010). This conclusion is further supported by texture refinements. Thus for polycrystalline olivine, the evolution in slip systems found by previous studies may be progressive, starting from as low as 3-4 GPa and up to 8 GPa. During such a gradual change, activation volumes measured on polycrystalline olivine cannot be linked to a particular slip system straightforwardly. The quest for 'the' activation volume of olivine at high pressure should cease at the expense of detailed work on the flow mechanisms implied. Such evolution in slip systems should also affect the interpretation of seismic anisotropy data in terms of upper mantle flow between 120 and 300 km depth.

Hilairet, Nadège; Wang, Yanbin; Sanehira, Takeshi; Merkel, Sébastien; Mei, Shenghua (CNRS-UMR); (UC); (UMM)

2012-03-15

375

Enhanced olivine carbonation within a basalt as compared to single-phase experiments: reevaluating the potential of CO2 mineral sequestration.  

PubMed

Batch experiments were conducted in water at 150 °C and PCO2 = 280 bar on a Mg-rich tholeiitic basalt (9.3 wt % MgO and 12.2 wt % CaO) composed of olivine, Ti-magnetite, plagioclase, and clinopyroxene. After 45 days of reaction, 56 wt % of the initial MgO had reacted with CO2 to form Fe-bearing magnesite, (Mg0.8Fe0.2)CO3, along with minor calcium carbonates. The substantial decrease in olivine content upon carbonation supports the idea that ferroan magnesite formation mainly follows from olivine dissolution. In contrast, in experiments performed under similar run durations and P/T conditions with a San Carlos olivine separate (47.8 wt % MgO) of similar grain size, only 5 wt % of the initial MgO content reacted to form Fe-bearing magnesite. The overall carbonation kinetics of the basalt was enhanced by a factor of ca. 40. This could be explained by differences in the chemical and textural properties of the secondary silica layer that covers reacted olivine grains in both types of sample. Consequently, laboratory data obtained on olivine separates might yield a conservative estimate of the true carbonation potential of olivine-bearing basaltic rocks. PMID:24735106

Sissmann, Olivier; Brunet, Fabrice; Martinez, Isabelle; Guyot, François; Verlaguet, Anne; Pinquier, Yves; Daval, Damien

2014-05-20

376

Lattice-preferred orientation of olivine found in diamond-bearing garnet peridotites in Finsch, South Africa and implications for seismic anisotropy  

NASA Astrophysics Data System (ADS)

Seismic anisotropy in the upper mantle provides important constraints on mantle dynamics, continental evolution and global tectonics and is believed to be produced by the flow-induced lattice-preferred orientation (LPO) of olivine. Recent experimental studies at high pressure and temperature have suggested that the LPO of olivine is affected by pressure in addition to water and stress. However, there has been no report yet for the pressure-induced LPO of natural olivine because samples from the deep upper mantle are rare and often unsuitable for study due to ambiguous foliation and lineation. Here we show evidence of the pressure-induced LPO of natural olivine in diamond-bearing garnet peridotites from Finsch, South Africa. We found that the [010] axes of olivine are aligned subnormal to foliation and that the [001] axes are aligned subparallel to lineation, which is known as B-type LPO of olivine. The equilibrium pressure of the samples, as estimated using geobarometer, was greater than 4 GPa, indicating that the samples originated from a depth greater than ?120 km. In addition, FTIR spectroscopy of the olivine showed that the samples are dry, with a water content of less than 90 ± 20 ppm H/Si (5.5 ± 1.2 ppm wt. H2O). These data suggest that the samples are the first natural examples of olivine displaying B-type LPOs produced due to high pressure under dry condition. Our data indicate that the trench-parallel seismic anisotropy observed in many subduction zones in and below subducting slabs at depths greater than ?90 km under dry condition may be attributed to the pressure-induced olivine fabrics (B-type LPO) and may be interpreted as the entrainment of the sub-lithospheric mantle in the direction of subduction rather than anomalous trench-parallel flow.

Lee, Jaeseok; Jung, Haemyeong

2015-01-01

377

Hydration of mantle olivine under variable water and oxygen fugacity conditions: a combined SIMS and FTIR study  

NASA Astrophysics Data System (ADS)

Trace concentrations of H+ dissolved in peridotite strongly affect both its rheology and solidus. Olivine comprises ~70% of a peridotite mode and is capable of incorporating substantial H+ at upper mantle conditions. Recently, Grant et al. (2007) conducted olivine hydration experiments to determine the influence of oxygen fugacity on H+ incorporation. FTIR analyses of their run products show that absorption bands at 3325 and 3355 cm-1 (Group II bands of Bai and Kohlstedt (1993)) are sensitive to oxygen fugacity and, therefore, likely correspond to Fe3+-bearing point defects. New olivine hydration experiments were conducted to quantify H+ concentration changes associated with these defects. SIMS was used to quantify the H+ concentration and FTIR analyses were used to monitor changes in point defect populations. Our results agree with those of Grant et al. (2007) that Group II absorption bands are sensitive to fO2, but SIMS analyses indicate that changing oxygen fugacity from Fe-Fe1-XO to Ni-NiO at constant P, T and olivine composition only increases the concentration of H+ by ~50%. Olivine hydration experiments were conducted at 1.0, 1.5, or 2.0 GPa and 1200 °C using a piston cylinder device. Oxygen fugacity was controlled at the Fe-Fe1-XO, Fe1-XO-Fe3O4, or Ni-NiO buffer. Mixed H2O-CO2 experiments were used to resolve the influence of P from that of H2O fugacity. Starting materials, fabricated from large single crystals of San Carlos olivine (Fo88-91), were pressure-sealed in either a Fe0 or Ni0 capsule. The H+ concentration of run products were measured using a Cameca 6F ion microprobe and the protocols of Koga et al. (2003). Total infrared absorption spectra were determined by a combined polarized absorption spectra taken at three orthogonal orientation, roughly parallel to crystallographic orientation. Spectra were taken on single crystal olivines shaped as parallelapipeds with several 100s of micron thicknesses. Results from our experiments confirm that H2O fugacity is the dominant influence on the solubility of H+ in mantle olivine. Increasing the fugacity of oxygen produces a modest increase in H+ solubility despite a significant increase in Group II absorption bands. Increasing pressure or Al3+ produce modest decreases. The negative dependence on Al3+ concentration is thought to reflect changing SiO2 activity. The solubility of H+ is insensitive to the Fe/Mg ratio of the olivine over the compositional range explored in our experiments. References. Grant et al. (2007) Earth Planet Sci Lett 261:217-229; Bai and Kohlstedt (1993) Phys Chem Minerals 19:460-471; Koga et al. (2003) Geochem, Geophys, Geosys doi: 10.1029/2002GC000378.

Gaetani, G. A.; O'Leary, J. A.; Koga, K. T.; Hauri, E. H.; Rose-Koga, E. F.

2012-12-01

378

New thermo-kinetic models of olivine metastability in subducting lithosphere: implications for deep-focus earthquakes  

NASA Astrophysics Data System (ADS)

A shear instability postulated to occur during the transformation of metastable olivine to its high-pressure polymorphs, wadsleyite and ringwoodite, has been proposed as the mechanism for deep-focus earthquakes. In order to evaluate this possibility we have formulated updated thermo-kinetic models to predict the amount of metastable olivine in a variety of subduction zones. Our models use newly derived activation energy parameters based on recent experiments in the (Mg,Fe)2SiO4 system, and we incorporate latent heat feedback due to the transformation into both the kinetics and the thermal model. We also consider the effects of transformation stress on growth kinetics and intracrystalline transformation, previously thought to be important only at high shear stresses. Our modeling predicts substantially smaller metastable olivine wedges than previous models that did not properly account for latent heat (Kirby et al., 1996) or used older kinetic parameters (e.g. Daessler et al., 1996; Devaux et al., 1997). Results of models considering only grain boundary nucleation and growth include the following: 1) In subduction zones with a thermal parameter (? = vertical convergence rate ¥ age of the lithosphere at the trench) less than ~5000 km, no significant metastable olivine wedge develops; this includes the Nazca subduction zone, in which the 1994 Bolivian earthquake occurred at a depth of 630 km. 2) For subduction zones such as Izu-Bonin, the Marianas, and Eastern Indonesia, with ? in the range 6000-10000 km, our models predict a maximum depth of metastability of 450-500 km. The maximum depths of earthquakes in these subduction zones are, respectively, 550, 670 and 670 km (e.g., Kirby et al, 1996). 3) In Tonga, the subduction zone with the most rapid convergence rates on Earth, an olivine wedge may persist to depths >660 km only if trench rollback (due to back-arc spreading) is taken into account. This depth is reduced by 80-120 km if trench rollback is not considered in the overall convergence rate. When intracrystalline transformation is taken into account, the maximum depth of metastability is further reduced by as much as 100 km, due to the large increase in the density of nucleation sites. Inhibition of growth by transformation stress can increase the depth interval over which transformation takes place, but is unlikely to be a dominant factor, especially if the intracrystalline mechanism operates. These results indicate that other mechanisms besides transformational faulting in metastable olivine must operate to cause the deepest earthquakes. References: Daessler et al, 1996, PEPI 94, 217-239\\Devaux et al, 1997, JGR 102, 24627-24637\\Kirby et al, 1996, Rev. Geophys., 34, 261-306\\

Mosenfelder, J. L.; Marton, F. C.; Rubie, D. C.

2001-12-01

379

Diffusive Re-equilibration of Volatiles and Oxygen Fugacity in Olivine-Hosted Melt Inclusions: Experiments and Numerical Models  

NASA Astrophysics Data System (ADS)

Determining the pre-eruptive volatile contents of magmas is of critical importance to understanding their generation and evolution. Mineral-hosted melt inclusions can provide information on the pre-eruptive H2O content of the magma as the host mineral shields the interior melt inclusion from decompression that the exterior magma undergoes as it ascends through the crust [1]. Consequently, melt inclusions have been widely used to provide pre-eruptive water contents (eg. [2]). Yet, there is strong evidence of rapid changes to H2O via proton diffusion through the olivine host crystal [3] that are not limited by redox reactions within the melt inclusion [4]. To quantify the extent to which H2O and other volatiles are faithfully recorded in olivine-hosted melt inclusions, we have combined experiments with numerical models to investigate the processes controlling diffusive re-equilibration of water and oxygen fugacity in an olivine-hosted melt inclusion. Dehydration experiments were performed on olivines from the 1999 Cerro Negro Volcano (Nicaragua) eruption. Melt inclusions with initially high water contents (~3.6 ± 0.6 wt. % H2O) were held at 1 atm and 1100°C at the Ni-NiO buffer for 4 to 72 hours. All run products were analyzed by SIMS on the Cameca 1280 ion microprobe at WHOI for H2O, CO2, SO2, F, and Cl. Using COMSOL Multiphysics finite-element modeling software we modeled the diffusive re-equilibration of water, oxygen fugacity, and other volatiles. To interpret our experimental results we used the geometry of the olivines and melt inclusions from the experiments in the numerical models. Our work confirms that the mechanism for loss or gain of H2O from an olivine-hosted melt inclusion is lattice diffusion of protons. Results from XANES analyses on previous dehydration experiments at 1250 °C indicate that H loss occurs through a process decoupled from fO2 re-equilibration. Re-equilibration of fO2 occurs independently via diffusion of point defects on timescales comparable to proton diffusion. Our numerical model is the first to incorporate this point-defect mediated re-equilibration mechanism. Furthermore, the ability to model not only water contents, but also the oxygen fugacity and multiple volatile species is a powerful tool to assess the degree, temperature, and duration of diffusive re-equilibration that a melt inclusion has undergone and the integrity of its composition in yielding estimates of pre-eruptive volatile contents.

Bucholz, C. E.; Gaetani, G. A.; Behn, M. D.

2011-12-01

380

Co-synthesis of LiFePO4 and Carbon Nanotubes  

SciTech Connect

The rate capabilities of LiFePO{sub 4} composites are dependent on the structure of the carbon that coats the powders, formed during co-calcination with carbon containing precursors. The addition of readily decomposed pyromellitic acid and graphitization catalysts such as ferrocene during synthesis results in coatings with low D/G (disordered/graphene) ratios, while maintaining the carbon content of the powders below 2 wt. %. This is important to avoid adversely affecting the tap density. The good correlation between the pressed pellet conductivities of the LiFePO{sub 4}/C composites and their rate capability in lithium cells is further confirmation of the importance of the carbon structure, because graphitic carbons generally have higher conductivities than disordered ones.

Wilcox, James; Doeff, Marca M.

2006-05-26

381

TEM Study of Fracturing in Spherical and Plate-like LiFePO4Particles  

SciTech Connect

An investigation of fracturing in LiFePO{sub 4} particles as a function of the particle morphology and history is presented. Two types of samples, one subjected to electrochemical cycling and another to chemical delithiation are compared. We observe the formation of micro fractures parallel to low indexed lattice planes in both samples. The fracture surfaces are predominantly parallel to (100) planes in the chemically delithiated powder and (100) and (010) planes in the electrochemically cycled powder. A consideration of the threshold stresses for dislocation glide shows that particle geometry plays an important role in the observed behavior.

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

2007-12-20

382

Graphene Modified LiFePO4 Cathode Materials for High Power Lithium ion Batteries  

SciTech Connect

Graphene-modified LiFePO{sub 4} composite has been developed as a Li-ion battery cathode material with excellent high-rate capability and cycling stability. The composite was prepared with LiFePO{sub 4} nanoparticles and graphene oxide nanosheets by spray-drying and annealing processes. The LiFePO{sub 4} primary nanoparticles embedded in micro-sized spherical secondary particles were wrapped homogeneously and loosely with a graphene 3D network. Such a special nanostructure facilitated electron migration throughout the secondary particles, while the presence of abundant voids between the LiFePO{sub 4} nanoparticles and graphene sheets was beneficial for Li{sup +} diffusion. The composite cathode material could deliver a capacity of 70 mAh g{sup -1} at 60C discharge rate and showed a capacity decay rate of <15% when cycled under 10C charging and 20C discharging for 1000 times.

Zhou, X.; Wang, F.; Zhu, Y.; Liu, Z.

2011-01-24

383

Olivine or Impact Melt: Origin of the “Orange” Material on Vesta  

NASA Astrophysics Data System (ADS)

NASA’s Dawn spacecraft entered orbit around asteroid (4) Vesta in July 2011 for a year-long mapping orbit, which allowed for complete imaging of the surface with the Dawn Framing Camera (FC). During the approach phase, enigmatic “orange” material was discovered on Vesta (Reddy et al. 2012). This “orange” material exhibits a red spectral slope and therefore is seen in FC ratio images (with red=0.75/0.45 microns, green=0.75/0.92 microns, and blue=0.45/0.75 microns) as orange. Here the green channel helps quantify the pyroxene band depth at 0.90 microns (greener areas have higher ratio, i.e. deeper band). The two other channels depend on the visible spectral slope (redder areas have positive visible slope; bluer areas have negative visible slope). FC images revealed diffuse “orange” ejecta around three impact craters: 34-km diameter Oppia, 30-km diameter Octavia, and 11-km Arruntia as well as numerous lobate “orange” deposits distributed around Rheasilvia’s basin rim. Additionally, some fresh-looking craters (like Cornelia or Rubria) display impact ejecta rays made of “orange” material. Even though some of the “orange” deposits are not directly linked with nearby impact craters, these observations suggest an impact related origin. The distribution of all of the lobate “orange” material is constrained to outside Rheasilvia, which suggests a link with the basin’s formation. Interestingly, as noted in Reddy et al. (2013) and Le Corre et al. (2013), the “orange” ejecta around Oppia corresponds to the olivine-rich unit that was postulated by Gaffey (1997). We will present our study of the geomorphology and composition of this material and explore meteoritical analogs (Le Corre et al. 2013). Several possible options for the composition are investigated in-depth including a cumulate eucrite layer exposed during impact, metal delivered by impactors, an olivine-orthopyroxene mixture, and impact melt. Combining all our analyses, the most probable analog for the orange material on Vesta appears to be impact melt. This work is supported by Dawn UCLA subcontract# 2090-S-MB170, NASA Dawn Participating Scientist Program Grant NNH09ZDA001N-DAVPS, and NASA Planetary Geology and Geophysics Grant NNX07AP73G.

Le Corre, Lucille; Reddy, V.; Schmedemann, N.; Becker, K.; O'Brien, D.; Yamashita, N.; Peplowski, P.; Prettyman, T.; Li, J.; Cloutis, E.; Denevi, B.; Kneissl, T.; Palmer, E.; Gaskell, R.; Nathues, A.; Gaffey, M.; Garry, W.; Sierks, H.; Russell, C.; Raymond, C.

2013-10-01

384

Partitioning of trace elements between carbonate melt and clinopyroxene and olivine at mantle P - T conditions  

NASA Astrophysics Data System (ADS)

In order to further assess the potential of molten carbonate as a transport agent in the mantle, gamma-ray spectroscopy was used to determine partition coefficients ( Ds) for several trace elements (Ba, Cs, Sr, Be, Ce, Gd, and Yb) between lherzolite phases (Cr-diopsidic clinopyroxene, Fo 90 olivine) and synthetic carbonate melt at 1150°C and 1.5 GPa. Trace elements were added as radiotracers, and D values were determined either by mass balance involving whole-sample and acid-washed mineral activities or by combining the latter with the activity of carbonate melt leachate. Results from 2-4 day forward experiments as well as from reversal experiments involving pre-doped minerals and radiotracer-free melt are in general accord and indicate mineral/melt equilibrium was closely approached. Average clinopyroxene/melt D values from mass balance are 0.00047 (Ba), 0.00023 (Cs), 0.043 (Sr), 0.17 (Be), 0.16 (Ce), 0.50 (Gd), and 0.30 (Yb). Ytterbium and strontium were the only elements for which olivine melt D values were determined, and averages of 0.10 (Yb) and 0.00020 (Sr) are reported. Partition coefficients determined in these experiments show an overall similarity to D values from studies involving low-Si melt compositions. This is an expected result in light of the near unity of two-liquid (carbonate/silicate) partition coefficients determined for some of these elements in the high-pressure experiments of Hamilton et al. (1989). The apparent lack of melt compositional preference among the trace elements examined in this study indicates that the levels of those elements in the spectrum of melts that can be produced from volatile-bearing lherzolite (i.e., carbonatites through to more Si-rich compositions) may be adequately modelled with a single set of D values. We illustrate that carbonate melt interaction with depleted lherzolite may markedly raise levels of large ion lithophile (LIL) elements in clinopyroxene from such rocks with only subtle mineralogical change. This result further substantiates the suggestion of Green and Wallace (1988) that ephemeral carbonatites may account for the LIL element-enriched character of otherwise refractory mantle xenoliths.

Brenan, James M.; Watson, E. Bruce

1991-08-01

385

Helium Isotopes in Basalt-Hosted Olivines From the Yellowstone Plateau: Implications on Volcanic Processes  

NASA Astrophysics Data System (ADS)

The Yellowstone Plateau volcanic field is the youngest part of a magmatic system that began its northeastward propagation along the path of the eastern Snake River Plain in the mid-Miocene. Previous noble gas isotopic studies in Yellowstone have focused on samples from hydrothermal features. Such samples are often subject to shallow crustal contamination that may mask a deeper magmatic component. Most of the reported He-isotope ratios within the Yellowstone caldera perimeter are ~7 ± 1 RA, with peaks occurring around Mud Volcano (~16 RA) and Gibbon Geyser Basin (~13 RA). Outside the caldera, the He-isotope ratios generally drop to <3 RA. The elevated helium isotope data from Mud Volcano and Gibbon Geyser Basin was interpreted as unequivocal evidence for the presence of a deep mantle plume underlying the Yellowstone volcanic field (Craig et al., 1978; Kennedy et al., 1985). However, in an attempt to reconcile the available geochemical and geophysical data some researchers argue solely for a shallow mantle source for the magmatism related to Yellowstone (Christiansen et al., 2002). To gain a better understanding of the helium isotope composition of the mantle source below Yellowstone and