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1

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

PubMed

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

Ramar, Vishwanathan; Balaya, Palani

2013-10-28

2

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, TN34 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, Rdiger; Bchner, Bernd

2013-08-01

3

Extended solid solutions and coherent transformations in nanoscale olivine cathodes.  

PubMed

Nanoparticle LiFePO4, the basis for an entire class of high power Li-ion batteries, has recently been shown to exist in binary lithiated/delithiated states at intermediate states of charge. The Mn-bearing version, LiMn(y)Fe(1-y)PO4, exhibits even higher rate capability as a lithium battery cathode than LiFePO4 of comparable particle size. To gain insight into the cause(s) of this desirable performance, the electrochemically driven phase transformation during battery charge and discharge of nanoscale LiMn0.4Fe0.6PO4 of three different average particle sizes, 52, 106, and 152 nm, is investigated by operando synchrotron radiation powder X-ray diffraction. In stark contrast to the binary lithiation states of pure LiFePO4 revealed in recent investigations, the formations of metastable solid solutions covering a remarkable wide compositional range, including while in two-phase coexistence, are observed. Detailed analysis correlates this behavior with small elastic misfits between phases compared to either pure LiFePO4 or LiMnPO4. On the basis of time- and state-of-charge dependence of the olivine structure parameters, we propose a coherent transformation mechanism. These findings illustrate a second, completely different phase transformation mode for pure well-ordered nanoscale olivines compared to the well-studied case of LiFePO4. PMID:24548146

Ravnsbk, D B; Xiang, K; Xing, W; Borkiewicz, O J; Wiaderek, K M; Gionet, P; Chapman, K W; Chupas, P J; Chiang, Y-M

2014-03-12

4

Synthesis and characterization of LiFePO4 electrode materials coated by graphene  

NASA Astrophysics Data System (ADS)

Olivine-type LiFePO4/graphene composite materials were synthesized via a high temperature solid-state method. In this paper, the sintering process of LiFePO4 precursor was conducted simultaneously with the reduction of graphene oxide, and then LiFePO4 with a thin and homogeneous graphene-shell coating can be obtained. The effects of different graphene coating amount on the structure and electrochemical properties of LiFePO4 cathode were investigated. Test results indicated that LiFePO4 material modified with high electrical conductive graphene exhibited a morphology of uniform and fine spherical particles with high crystallinity. LiFePO4/graphene (92:8 wt.) cathode had the lowest charge transfer resistance among all tested samples. It delivered a capacity of 167 mAh g-1 at 0.1 C and could tolerate various discharge currents with a capacity decay rate of only 27.2% after cycled stepwise under 0.1 C, 2 C, 5 C for 15 times, respectively.

Tian, Zhe; Liu, Shanshan; Ye, Feng; Yao, Sijia; Zhou, Zhufa; Wang, Shumei

2014-06-01

5

Olivine-type nanosheets for lithium ion battery cathodes.  

PubMed

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

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

2013-06-25

6

Fabrication and Characterization of LiFePO4 Nanotubes by a Sol-gel-AAO Template Process  

NASA Astrophysics Data System (ADS)

The LiFePO4 nanotubes were successfully fabricated by a sol-gel method with porous anodic aluminum oxide as the template. Transmission electron microscopy and scanning electron microscopy showed that the synthesized LiFePO4 nanotubes were monodispersed and parallel to one another. Selected area electron diffraction pattern, X-ray diffraction and X-ray photoelectron spectroscopy investigations jointly demonstrated that the synthesized LiFePO4 nanotubes were pure olivine structure. This approach offered a potentially way for fabricating ordered LiFePO4 nanotubes at room temperature and ambient conditions, which might be expected to find promising application as a new cathode material in lithium ion battery.

Liu, Xiao-hong; Wang, Jin-qing; Zhang, Jun-yan; Yang, Sheng-rong

2006-12-01

7

Facile low-temperature polyol process for LiFePO4 nanoplate and carbon nanotube composite  

NASA Astrophysics Data System (ADS)

Crystalline LiFePO4 nanoplates were incorporated with 5 wt.% multi-walled carbon nanotubes (CNTs) via a facile low temperature polyol process, in one single step without any post heat treatment. The CNTs were embedded into the LiFePO4 particles to form a network to enhance the electrochemical performance of LiFePO4 electrode for lithium-ion battery applications. The structural and morphological characters of the LiFePO4-CNT composites were investigated by X-ray diffraction, Fourier Transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were analyzed by cyclic voltammetry, electrochemical impedance spectroscopy and charge/discharge tests. Primary results showed that well crystallized olivine-type structure without any impurity phases was developed, and the LiFePO4-CNT composites exhibited good electrochemical performance, with a reversible specific capacity of 155 mAh g-1 at the current rate of 10 mA g-1, and a capacity retention ratio close to 100% after 100 cycles.

Wu, Guan; Zhou, Yingke; Gao, Xuefeng; Shao, Zongping

2013-10-01

8

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

9

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

SciTech Connect

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

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

2010-08-11

10

High-capacity cathodes for lithium-ion batteries from nanostructured LiFePO4 synthesized by highly-flexible and scalable flame spray pyrolysis  

NASA Astrophysics Data System (ADS)

Olivine, LiFePO4 is a promising cathode material for lithium-ion batteries due to its low cost, environmental acceptability and high stability. Its low electric conductivity prevented it for a long time from being used in large-scale applications. Decreasing its particle size along with carbon coating significantly improves electronic conductivity and lithium diffusion. With respect to the controlled formation of very small particles with large specific surface, gas-phase synthesis opens an economic and flexible route towards high-quality battery materials. Amorphous FePO4 was synthesized as precursor material for LiFePO4 by flame spray pyrolysis of a solution of iron acetylacetonate and tributyl phosphate in toluene. The pristine FePO4 with a specific surface from 126-218m2g-1 was post-processed to LiFePO4/C composite material via a solid-state reaction using Li2CO3 and glucose. The final olivine LiFePO4/C particles still showed a large specific surface of 24m2g-1 and were characterized using X-ray diffraction (XRD), electron microscopy, X-ray photoelectron spectrocopy (XPS) and elemental analysis. Electrochemical investigations of the final LiFePO4/C composites show reversible capacities of more than 145mAhg-1 (about 115mAhg-1 with respect to the total coating mass). The material supports high drain rates at 16C while delivering 40mAhg-1 and causes excellent cycle stability.

Hamid, N. A.; Wennig, S.; Hardt, S.; Heinzel, A.; Schulz, C.; Wiggers, H.

2012-10-01

11

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

12

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

Microsoft Academic Search

LiMnPO4, with a particle size of 50150nm, was prepared by oleic acid-assisted solid-state reaction. The materials were characterized\\u000a by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical\\u000a properties of the materials were investigated by galvanostatic cycling. It was found that the introduction of oleic acid in\\u000a the precursor led to smaller particle size and more

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

13

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

14

Solvothermal synthesis of Fe-doping LiMnPO4 nanomaterials for Li-ion batteries  

NASA Astrophysics Data System (ADS)

The Fe-doping LiMnPO4 (LiMn1-xFexPO4, x?0.5) nanomaterials are solvothermally synthesized in a mixed solvent of water and polyethylene glycol (PEG). The particle morphology can be controlled simply by adjusting the pH values of precursor suspensions. Electrochemical test shows that LiMn0.9Fe0.1PO4 nanoplates with a thickness of 20-30nm could deliver the largest discharge capacity, which is attributed to the fast Li+ diffusion in the diffusion path of [010] crystallographic axis along the short radial direction of the nanoplates. It is demonstrated that Fe doping could significantly increase the initial reversible capacity, cycle performance and rate capability. The first discharge capacities of Fe-doped LiMnPO4 are all above 150mAhg-1 at the discharge rate of 0.05C. Especially, LiMn0.5Fe0.5PO4 delivers 100% capacity retention with the reversible capacity of 147mAhg-1 at the discharge rate of 1C, and losses only about 23.4% capacity with the discharge rate varying from 0.1C to 5C. The variation of energy density predicts that LiMn0.5Fe0.5PO4 shows the potential application for high-power devices.

Hu, Lingjun; Qiu, Bao; Xia, Yonggao; Qin, Zhihong; Qin, Laifen; Zhou, Xufeng; Liu, Zhaoping

2014-02-01

15

Extraction of Layerwise Conductivities in Carbon-Enhanced, Multilayered LiFePO4 Cathodes  

E-print Network

by addition of carbon black and graphite. In order to extract these layerwise and interlayer properties, we % and types carbon black, graphite of conductive additives. LiFePO4 particles within the electrodes were% in electrical resistivities of LiFePO4 matrix with addition of carbon black from 3 to 10 wt %; addition

Sastry, Ann Marie

16

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

PubMed

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

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

2013-02-01

17

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

SciTech Connect

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

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

2003-11-25

18

Rate-dependent, Li-ion insertion/deinsertion behavior of LiFePO4 cathodes in commercial 18650 LiFePO4 cells.  

PubMed

We have performed operando synchrotron high-energy X-ray diffraction (XRD) to obtain nonintrusive, real-time monitoring of the dynamic chemical and structural changes in commercial 18650 LiFePO4/C cells under realistic cycling conditions. The results indicate a nonequilibrium lithium insertion and extraction in the LiFePO4 cathode, with neither the LiFePO4 phase nor the FePO4 phase maintaining a static composition during lithium insertion/extraction. On the basis of our observations, we propose that the LiFePO4 cathode simultaneously experiences both a two-phase reaction mechanism and a dual-phase solid-solution reaction mechanism over the entire range of the flat voltage plateau, with this dual-phase solid-solution behavior being strongly dependent on charge/discharge rates. The proposed dual-phase solid-solution mechanism may explain the remarkable rate capability of LiFePO4 in commercial cells. PMID:24521163

Liu, Qi; He, Hao; Li, Zhe-Fei; Liu, Yadong; Ren, Yang; Lu, Wenquan; Lu, Jun; Stach, Eric A; Xie, Jian

2014-03-12

19

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

20

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

21

Synthesis of Nanowire and Hollow LiFePO4 Cathodes for High-Performance Lithium Batteries  

E-print Network

Articles Synthesis of Nanowire and Hollow LiFePO4 Cathodes for High-Performance Lithium Batteries of the electrode materials for lithium batteries, such as TiO2,1­4 Li4Ti5O12,5 and LiFePO4,6­11 have been reported LiFePO4 cathodes using the hard templates KIT-6 and SBA-15 is reported for high-performance lithium

Cho, Jaephil

22

Dispersion properties of aqueous-based LiFePO 4 pastes and their electrochemical performance for lithium batteries  

Microsoft Academic Search

Aqueous-based LiFePO4 pastes to fabricate the cathode of lithium-ion battery were investigated with an emphasis on chemical control of suspension component interactions among LiFePO4 particulates, carbon black, carboxymethyl cellulose (CMC), and poly(acrylic acid) (PAA). The dispersion properties of LiFePO4 were characterized using electroacoustic, flow behavior and green microstructural observation. Correlation was made between the dispersion properties and electrochemical performance of

Jin-Hyon Lee; Jeom-Soo Kim; Yoon Chang Kim; Dong Sik Zang; Ungyu Paik

2008-01-01

23

Comparison of LiMnPO4 made by Combustion and Hydrothermal Syntheses  

SciTech Connect

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

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

2008-05-15

24

Comparison of LiMnPO4 made by Combustion and Hydrothermal Syntheses  

SciTech Connect

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

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

2008-10-12

25

LiFePO 4/gel/natural graphite cells for the BATT program  

NASA Astrophysics Data System (ADS)

LiFePO 4/gel/natural graphite (NG) cells have been prepared and cycled under a fixed protocol for cycle and calendar life determination. Cell compression of 68 kPa was found to represent an optimal balance between cell impedance and the first cycle losses on the individual electrodes with the gel electrolyte. Cells with a Li anode showed capacities of 160 and 78 mAh/g LiFePO 4 for C/25 and 2 C discharge rates, respectively. Rapid capacity and power fade were observed in the LiFePO 4/gel/NG cells during cycling and calendar life studies. Diagnostic evaluations point to the consumption of cycleable Li though a side reaction as the reason for performance fade with minimal degradation of the individual electrodes.

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

26

TEM Studies of Carbon Coated LiFePO4 after Charge DischargeCycling  

SciTech Connect

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

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

2006-11-30

27

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

28

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 for battery management system (BMS) applications and comprehensive aging investigations. Based on a modified

Paris-Sud XI, Université de

29

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

SciTech Connect

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

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

2012-01-01

30

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

31

Low cost synthesis of LiFePO4/C cathode materials with Fe2O3  

NASA Astrophysics Data System (ADS)

LiFePO4/C composite materials have been synthesized from a low cost Fe2O3 precursor by a hydrothermal method to make LiFePO4(OH) in a first step followed by a fast calcination and carbon coating. This method combines the advantages of both hydrothermal and solid state synthetic methods. The as-prepared LiFePO4/C provides enhanced discharge capacity and cycling stability compared to LiFePO4 synthesized using a solid state method with the same precursors. Thus, the method to be described herein is a promising option in the search to reduce the cost of large-scale synthesis of LiFePO4/C for use in lithium-ion batteries, while maintaining adequate electrochemical performance.

Cheng, Lifeng; Liang, Guoxian; El Khakani, Soumia; MacNeil, Dean D.

2013-11-01

32

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

33

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

34

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

35

Lithium extraction\\/insertion in LiFePO 4: an X-ray diffraction and Mssbauer 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 Mssbauer 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 Hggstrm; John O Thomas

2000-01-01

36

Nanocomposite of LiFePO4 and mesoporous carbon prepared by microwave heating for rechargeable lithium batteries  

NASA Astrophysics Data System (ADS)

A nanocomposite of LiFePO4 and mesoporous carbon was synthesized from MgO-templated mesoporous carbon by microwave heating for use as a cathode material in rechargeable Li batteries. Our research group reported a composition method using a porous template in the a previous paper.[1] Despite its low carbon content, the present composite shows better electrochemical performance than our previously reported version. The LiFePO4 nanoparticles were homogeneously dispersed in the template because of the suppressed growth of LiFePO4 crystals in the template pores and small thermal gradient resulting from microwave heating. The three-dimensional conducting carbon network between the LiFePO4 nanoparticles led to excellent cycling stability and rate capability. No decrease in discharge capacity was observed up to 100 cycles, and 85% of the reversible capacity at a Crate of 0.1 was retained at a C-rate of 30.

Roh, Kwang Chul; Lee, Ho Jun; Lee, Jae-Won

2013-11-01

37

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 700W for 5min. The as-obtained LiFePO4/C sample is prepared via MIAS consisting of nanopores (20-30nm) and nanoparticles (20-30nm) which are coated with uniform, complete carbon layers (about ?3nm). These superior physical characters provide LiFePO4/C (MIAS) excellent electrochemical performance at 0.1C including the high discharge capacity of 156.9mAhg-1 and the low polarization of 51.5mV. At the discharge rate of 1C, LiFePO4/C (MIAS) exhibits the low polarization of 202.3mV, high capacity of 126.7mAhg-1, high discharge voltage of 3.33V, and specific energy of 398.5kWhkg-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 95.5mAhg-1. The low polarization of LiFePO4/C (MIAS) results in the good discharge voltage of 3.06V, high specific energy of 278.8Whkg-1, and excellent energy efficiency of 72.0% at 5C.

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

2014-12-01

38

A new charging mode of Li-ion batteries with LiFePO 4 \\/C composites under low temperature  

Microsoft Academic Search

Li-ion batteries with LiFePO4\\/C composites are difficult to be charged at low temperatures. In order to improve the low temperature performance of LiFePO4\\/C power batteries, the chargedischarge characteristics were studied at different temperatures, and a new charging mode under\\u000a low temperature was proposed. In the new charging mode, the batteries were excited by current pulses with the charge rates\\u000a between

Xiao Wei Zhao; Guo Yu Zhang; Lin Yang; Jia Xi Qiang; Zi Qiang Chen

2011-01-01

39

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 675C 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

40

Charge-discharge rate of spinel lithium manganese oxide and olivine lithium iron phosphate in ionic liquid-based electrolytes  

NASA Astrophysics Data System (ADS)

Rate capability of Li/spinel LiMn2O4 or olivine LiFePO4 positive electrode cells containing mixed imidazolium ionic liquids electrolytes has been investigated under comparison with conventional organic solvent electrolyte and piperidinium ionic liquid. The LiMn2O4 electrode provides variation of rate capabilities among the ionic liquid electrolytes, while ionic liquid electrolytes provide similar extent of capacity degradation under high rate compared with organic solvent electrolyte for LiFePO4 electrode. Such differences in electrolyte dependences of the rate capabilities can be explained in relation to parameters in the high frequency resistances on AC impedance, assumed as interfacial resistances. The rate capability of LiMn2O4 is somewhat related to the activation energy of the high frequency resistance, while for LiFePO4 the resistance value appears to contribute to the rate capability.

Egashira, Minato; Kanetomo, Akinori; Yoshimoto, Nobuko; Morita, Masayuki

2011-08-01

41

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 consisted of well-packed LiFePO4 nano-plates coated with nano-carbon, a result of sucrose pyrolysis, and were directly assembled into cells for testing. The LiFePO4/C nano-composite film cathode delivered

Cao, Guozhong

42

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

43

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 20eV, 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

44

Redirected charge transport arising from diazonium grafting of carbon coated LiFePO4.  

PubMed

The morphological and the electrical properties of carbon coated LiFePO4 (LFPC) active material functionalized by 4-ethynylbenzene tetrafluoroboratediazonium salt were investigated. For this purpose, FTIR, Raman, XPS, High Resolution Transmission Electron Microscopy (HRTEM) and Broadband Dielectric Spectroscopy (BDS) were considered. Electronic conductivities of LFPC samples at room temperature were found to decrease in a large frequency range upon simple immersion in polar solvents and to decrease further upon functionalization. Due to their high dipole moment, strongly physisorbed molecules detected by XPS likely add barriers to electron hopping. Significant alteration of the carbon coating conductivity was only observed, however, upon functionalization. This effect is most presumably associated with an increase in the sp(3) content determined by Raman spectroscopy, which is a strong indication of the formation of a covalent bond between the organic layer and the carbon coating. In this case, the electron flux appears to be redirected and relayed by short-range (intra chain) and long-range (inter chain) electron transport through molecular oligomers anchored at the LFPC surface. The latter are controlled by tunnelling and slightly activated hopping, which enable higher conductivity at low temperature (T < 250 K). Alteration of the electron transport within the carbon coating also allows detection of a relaxation phenomenon that corresponds to small polaron hopping in bulk LiFePO4. XPS and HRTEM images allow a clear correlation of these findings with the island type oligomeric structure of grafted molecules. PMID:25234701

Madec, L; Seid, K A; Badot, J-C; Humbert, B; Moreau, P; Dubrunfaut, O; Lestriez, B; Guyomard, D; Gaubicher, J

2014-11-01

45

Electron Microscopy Study of the LiFePO4 to FePO4 PhaseTransition  

SciTech Connect

The mechanism by which LiFePO4 is transformed intoisostructural FePO4 has been elucidated using electron microscopy onlarge, hydrothermally-grown LiFePO4 crystals following chemicaldelithiation. Lithium is extracted at narrow, disordered transition zoneson the ac crystal surface as the phase boundary progresses in thedirection of the a-axis. The substantial lattice mismatch along a (ca. 5percent) causes crack formation in the bc plane. Despite considerabledisorder in the transition zone, the general structural arrangement ispreserved, leading to good crystallinity in the newly created FePO4domains. Implications for improved electrode performance arediscussed.

Chen, Guoying; Song, Xiangyun; Richardson, Thomas J.

2006-01-06

46

Experimental and numerical study of phase transition of LiFePO 4 material in lithium ion batteries  

NASA Astrophysics Data System (ADS)

Phase transition behavior of LiFePO4 material has been studied in this work. During electrochemical charge/discharge processes, LiFePO 4 transforms into FePO4 and this electrochemically driven phase transition of the two-phase system results in a potential plateau in a battery discharge curve. Besides, battery performance, especially under high rates, depends critically on this two-phase transition. However, this phase transition mechanism in the LiFePO4 crystal structure has yet not been understood in details. Developing better understanding is essential for designing high performing, safe and stable batteries. Currently available phase transition models for LiFePO4, such as the classical `core-shrinking model' and recently the `domino cascade model', have shed lights on the phase transition mechanism, however, with somewhat contradicting conclusions. The former predicted a continuous phase transition between LiFePO4 and FePO4 within an individual particle. In contrast, the latter, based on the fact of anisotropic diffusion of Li, provided a microscopically heterogeneous picture of phase transition: phase transition is abrupt, and de-lithiated and lithiated particles co-exist in a battery electrode. To achieve a better understanding of the two-phase transition phenomena, two specially designed sophisticated methods, i.e., in-situ Raman spectroscopy and in-situ X-ray Diffraction (XRD), have been developed in this work. The particle level phase transition of LiFePO4 was probed in the in-situ Raman study. Under slow-rate discharge/charge, it was found that the particles were either fully transformed or untransformed indicating that the phase transition in LiFePO4 material was not uniform at the particle level. Electronic conductivity and local electrode microstructure determined the preferred sequence of phase transition of the particles. This study also revealed that non-equilibrium phase transition occurred as a result of delayed phase transition. The in-situ XRD study attempted to investigate the bulk level phase transition behavior of LiFePO4 and was conducted at four different discharge rates. Analysis of the high-resolution diffraction patterns showed a gradual and continuous change in phase transition. Again, a delayed phase transition was observed at high-rate discharge due to the non-equilibrium pathway. From both in-situ Raman and in-situ XRD experiments, only two stoichiometric compounds (LiFePO4 and FePO4) was detected, indicating that during electrochemical charge/discharge processes once Li ion de-intercalates/intercalates, it immediately forms the end-members and no intermediate compounds exist. Particle size and morphology of LiFePO4 were also studied using numerical models in the phase transition behavior. At a slow discharge rate, plate shaped particles showed higher capacity than spherical particles and the opposite trend was observed at high discharge rates above some critical discharge rates. Big particles and high discharge rates induced non-equilibrium phase transition in the LiFePO4 particles which expands the miscibility gap between the end-members and gave sharp narrow two-phase interfaces.

Siddique, Md Noor E. Alam

47

Dispersion properties of aqueous-based LiFePO4 pastes and their electrochemical performance for lithium batteries.  

PubMed

Aqueous-based LiFePO(4) pastes to fabricate the cathode of lithium-ion battery were investigated with an emphasis on chemical control of suspension component interactions among LiFePO(4) particulates, carbon black, carboxymethyl cellulose (CMC), and poly(acrylic acid) (PAA). The dispersion properties of LiFePO(4) were characterized using electroacoustic, flow behavior and green microstructural observation. Correlation was made between the dispersion properties and electrochemical performance of the particles. It was found that the addition of PAA significantly decreases the viscosity of the LiFePO(4) paste. The decrease of viscosity leads to increasing the solid concentration, which affects the electrochemical properties. The electrochemical characteristics of formulated pastes were evaluated using coin-type half cells. Although there is no significant difference between coin cells fabricated with CMC only and CMC/PAA combination in electrochemical cycling test, the dispersion properties of pastes indicate that the electrode fabricated with CMC/PAA, potentially, has much improved discharge capacity compared to that with CMC alone because of the possibility to increase active mass portion in electrode paste. PMID:18550285

Lee, Jin-Hyon; Kim, Jeom-Soo; Kim, Yoon Chang; Zang, Dong Sik; Paik, Ungyu

2008-09-01

48

Electrochemical performance of LiFePO4/C cathode material modified with V2O5  

NASA Astrophysics Data System (ADS)

LiFePO4/C composites are prepared from amorphous FePO4 xH2O and are modified with crystalline metal oxide V2O5 by using a solid-state reaction process. The crystalline structure and the morphology of the synthesized powders have been characterized by using X-ray diffraction and scanning electron microscopy, and the electrochemical performances have been evaluated by using cyclic voltammetry measurements and galvanostatic charge/discharge tests. The vanadium, which is present as vanadium trioxide, is found to manipulate the residual amount of carbon in LiFePO4/C, which is related to the electrical conductivity of the material. Based on the investigated samples, the pristine LiFePO4/C material exhibits the best electrochemical properties. The results in this study indicate that surface modification with crystalline V2O5 may not be an effective way to improve the overall properties of LiFePO4/C, which is often used as a cathode for lithium-ion batteries.

Islam, Mobinul; Ur, Soon-Chul; Yoon, Man-Soon

2014-07-01

49

Li ion diffusion mechanisms in LiFePO4: an ab initio molecular dynamics study.  

PubMed

The mechanisms for thermal (self) diffusion of Li ions in fully lithiated LiFePO(4) have been investigated with spin polarized ab initio molecular dynamics calculations. The effect of electron correlation is taken into account with the GGA+U formalism. It was found that Li ion diffusion is not a continuous process but through a series of jumps from one site to another. A dominant process is the hopping between neighboring Li sites around the PO(4) groups, which results in a zigzag pathway along the crystallographic b-axis. This observation is in agreement with a recent neutron diffraction experiment. A second process involves the collaborative movements of the Fe ions leading to the formation of antisite defects and promotes Li diffusion across the Li ion channels. The finding of the second mechanism demonstrates the benefit of ab initio molecular dynamics simulation in sampling diffusion pathways that may not be anticipated. PMID:21932862

Yang, Jianjun; Tse, John S

2011-11-17

50

In situ construction of carbon nano-interconnects between the LiFePO 4 grains using ultra low-cost asphalt  

Microsoft Academic Search

LiFePO4\\/C composite cathode materials with carbon nano-interconnect structures were synthesized by one-step solid state reaction using low-cost asphalt as both carbon source and reducing agent. Based on the thermogravimetry, differential scanning calorimetry, transmission electron microscopy and high-resolution transmission electron microscopy, a growth model was proposed to illustrate the formation of the carbon nano-interconnect between the LiFePO4 grains. The LiFePO4\\/C composite

Wenkui Zhang; Xiaozheng Zhou; Xinyong Tao; Hui Huang; Yongping Gan; Chuntao Wang

2010-01-01

51

Research Update: Retardation and acceleration of phase separation evaluated from observation of imbalance between structure and valence in LiFePO4/FePO4 electrode  

NASA Astrophysics Data System (ADS)

LiFePO4 is a potential positive electrode material for lithium ion batteries. We have experimentally observed an imbalance between the valence change of Fe ions and the structure change from the LiFePO4 phase to the FePO4 phase during delithiation by simultaneous in situ XRD and XANES measurements in an LiFePO4/FePO4 electrode. The ratio of structure change to valence change clearly indicates that the phase separation from LiFePO4 to FePO4 is suppressed at the beginning of delithiation, while it is accelerated at the latter stage, which is due to the coherent strain caused by the lattice misfit between the two phases.

Tokuda, Kazuya; Kawaguchi, Tomoya; Fukuda, Katsutoshi; Ichitsubo, Tetsu; Matsubara, Eiichiro

2014-07-01

52

Encapsulation of LiFePO4 by in-situ graphitized carbon cage towards enhanced low temperature performance as cathode materials for lithium ion batteries  

NASA Astrophysics Data System (ADS)

The severe capacity decay of LiFePO4 at low temperatures (?0 C) limits its wide applications as cathode materials for energy storage batteries. Creating comprehensive carbon network between particles with improved electronic conductivity is a well known solution to this problem. Here, a novel structured LiFePO4/C composite was prepared by a facile solid state route, in which nanosized LiFePO4 spheres were encapsulated by in-situ graphitized carbon cages. With the enhancement in electronic conductivity (2.15e-1 S cm-1), the composite presented excellent rate performance at room temperature and remarkable capacity retention at -40 C, with charge transfer resistance much lower than commercial LiFePO4.

Yao, Bin; Ding, Zhaojun; Zhang, Jianxin; Feng, Xiaoyu; Yin, Longwei

2014-08-01

53

Performance of LiFePO 4 as lithium battery cathode and comparison with manganese and vanadium oxides  

Microsoft Academic Search

LiFePO4 was synthesized by a high temperature method and high purity was confirmed by both powder X-ray diffraction and thermal analysis. It can deliver 136Ah\\/kg, 80% of theoretical capacity at 1mA\\/cm2 at high cathode load levels at room temperature; 100% capacity can be obtained by raising the temperature to 60C or reducing the discharge rate to 0.1mA\\/cm2. The method of

Shoufeng Yang; Yanning Song; Katana Ngala; Peter Y. Zavalij; M. Stanley Whittingham

2003-01-01

54

Excellent Temperature Performance of Spherical LiFePO4/C Composites Modified with Composite Carbon and Metal Oxides  

PubMed Central

Nanosized spherical LiFePO4/C composite was synthesized from nanosized spherical FePO42H2O, Li2C2O4, aluminum oxide, titanium oxide, oxalic acid, and sucrose by binary sintering process. The phases and morphologies of LiFePO4/C were characterized using SEM, TEM, CV, EIS, EDS, and EDX as well as charging and discharging measurements. The results showed that the as-prepared LiFePO4/C composite with good conductive webs from nanosized spherical FePO42H2O exhibits excellent electrochemical performances, delivering an initial discharge capacity of 161.7?mAhg?1 at a 0.1?C rate, 152.4?mAhg?1 at a 1?C rate and 131.7?mAhg?1 at a 5?C rate, and the capacity retention of 99.1%, 98.7%, and 95.8%, respectively, after 50 cycles. Meanwhile, the high and low temperature performance is excellent for 18650 battery, maintaining capacity retention of 101.7%, 95.0%, 88.3%, and 79.3% at 55C, 0C, ?10C, and ?20C by comparison withthat of room temperature (25C) at the 0.5 C rate over a voltage range of 2.2?V to 3.6?V, respectively. PMID:24526888

Zhang, Bao; Zeng, Tao; Zhang, Jiafeng; Peng, Chunli; Zheng, Junchao; Chen, Guomin

2014-01-01

55

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

NASA Astrophysics Data System (ADS)

In order to elucidate the magnetism and Li diffusion in LiFePO4, we have measured muon-spin rotation and relaxation (?+SR) spectra for the polycrystalline LiFePO4 sample in the temperature range between 1.8 and 500 K. Below TN52 K, two oscillatory signals together with one fast relaxation signal were clearly found in the zero-field (ZF) ?+SR spectrum. The three signals are reasonably explained using an antiferromagnetic (AF) spin structure proposed by neutron measurements, because electrostatic potential calculations suggests multiple different muon sites in the LiFePO4 lattice. However, the AF ordered moment estimated from ?+SR was about 3/4 of that reported by neutron, probably due to a different time window between the two techniques. In the paramagnetic state, ZF and longitudinal-field (LF) ?+SR spectra exhibited a dynamic nuclear field relaxation. From the temperature dependence of the field fluctuation rate, a diffusion coefficient of Li+ ions (DLi) at 300 K was estimated about 3.610-10 cm2/s, assuming that diffusing Li+ ions jump between the regular site and interstitial sites.

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

2011-08-01

56

A synthesis of LiFePO4 starting from FePO4 under reducing atmosphere  

NASA Astrophysics Data System (ADS)

A fast and easy way to produce LiFePO4 starting from FePO4, used as iron and phosphorus source, is proposed. 5% hydrogen is employed as a reducing agent and various compounds containing lithium as lithiation agents. The selected lithiation agents included: LiCl, CH3COOLi, LiOH, Li2S, LiH, and Li2CO3. Solid state synthesis is used for the LiFePO4 preparation and the so obtained materials are structurally characterized by XRD. The materials are used to fabricate composite electrode and their specific capacity is evaluated by low rate galvanostatic charge/discharge cycles (C/10 rate). Among the various lithium salts, the acetate give rise to the LiFePO4 with the best electrochemical performance. The morphology of this material is further investigated by SEM microscopy and the specific capacity is evaluated as a function of the discharge rate and the cycle number.

Prosini, Pier Paolo; Cento, Cinzia; Masci, Amedeo; Carewska, Maria; Gislon, Paola

2014-06-01

57

A facile route to modify ferrous phosphate and its use as an iron-containing resource for LiFePO4 via a polyol process.  

PubMed

This study introduces an economical and environmentally friendly way of synthesizing LiFePO4/C to be used as cathode material in lithium ion batteries via two processes: (1) the synthesis of LiFePO4/C cathode material using a low cost divalent precursor ferrous phosphate, Fe3 (PO4)28H2O, as iron source in a polyol process and (2) the modification of the morphology of this precursor by varying the reaction time in a coprecipitation process. The study examines the effects of different structures and morphologies of the precursor on the structure and electrochemical performance of the as-synthesized LiFePO4/C. The LiFePO4/C shows an excellent rate capability and cycle performance, with initial discharge capacities of 153, 128, and 106 mA h g(-1) at 1 C, 5 C, and 10 C. The capacity retention is respectively 98.7%, 98.2%, and 98.7%, after 10 cycles at the corresponding rates. The capacity retention remains at 97% even after 300 cycles at the rate of 10 C. The outstanding electrochemical performance can be attributed to the improved rate of Li(+) diffusion and the excellent crystallinity of synthesized LiFePO4/C powders through the modified precursor. Therefore, this is an economical and environmentally friendly way of synthesizing LiFePO4/C to be used as cathode material in lithium ion batteries. PMID:24858212

Li, Shaomin; Liu, Xichuan; Mi, Rui; Liu, Hao; Li, Yinchuan; Lau, Woon-min; Mei, Jun

2014-06-25

58

Thermal analyses of LiFePO4/graphite battery discharge processes  

NASA Astrophysics Data System (ADS)

An electrochemical-thermal coupling model is developed to describe the LiFePO4/graphite battery discharge and charge processes. Various heat generations/consumptions including Joule heat, reversible entropy heat, contact resistance heat, irreversible electrochemical reaction heat, ionic migration heat, and convective heat release to the ambient during charge or discharge processes are calculated in detail. The developed model is first validated by experimental data. Then systematic and comprehensive thermal analyses with respect to various discharge processes are performed based on the simulated results. For the specific cell considered, the irreversible electrochemical reaction heat and contact resistance heat are found to be the two main heat generation sources; for discharge processes of higher C-rate, the contact resistance heat take more proportion of the total heat generation as it is directly proportional to the squared discharge current density; the ionic migration heat is a sink with magnitude being about 1/3 of the Joule heat. The reversible entropy heat changes its sign from a negative heat sink to a positive heat source during a discharge process and its changing magnitude may be comparable to the irreversible electrochemical reaction heat for all the discharge processes of different C-rates.

Jiang, Fangming; Peng, Peng; Sun, Yiqiong

2013-12-01

59

Lithium deintercalation in LiFePO4 nanoparticles via a domino-cascade model  

NASA Astrophysics Data System (ADS)

Lithium iron phosphate is one of the most promising positive-electrode materials for the next generation of lithium-ion batteries that will be used in electric and plug-in hybrid vehicles. Lithium deintercalation (intercalation) proceeds through a two-phase reaction between compositions very close to LiFePO4 and FePO4. As both endmember phases are very poor ionic and electronic conductors, it is difficult to understand the intercalation mechanism at the microscopic scale. Here, we report a characterization of electrochemically deintercalated nanomaterials by X-ray diffraction and electron microscopy that shows the coexistence of fully intercalated and fully deintercalated individual particles. This result indicates that the growth reaction is considerably faster than its nucleation. The reaction mechanism is described by a `domino-cascade model' and is explained by the existence of structural constraints occurring just at the reaction interface: the minimization of the elastic energy enhances the deintercalation (intercalation) process that occurs as a wave moving through the entire crystal. This model opens new perspectives in the search for new electrode materials even with poor ionic and electronic conductivities.

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

2008-08-01

60

Synthesis, characterization and electrochemical performances of LiFePO4/graphene cathode material for high power lithium-ion batteries  

NASA Astrophysics Data System (ADS)

LiFePO4/graphene (LiFePO4/G) cathode with exciting electrochemical performance was successfully synthesized by liquid phase method. LiFePO4 nanoparticles wrapped with multi-layered grapheme can be fabricated in a short time. This method did not need external heating source. Heat generated by chemical reaction conduct the process and removed the solvent simultaneously. The LiFePO4/G were analyzed by X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), transmission electron microscopy (TEM), magnetic properties analysis and electrochemical performance tests. The LiFePO4/G delivered a capacity of 160mAhg-1 at 0.1C and could tolerate various dis-charge currents with a capacity retention rate of 99.8%, 99.2%, 99.0%, 98.6%, 97.3% and 95.0% after stepwise under 5C, 10C, 15C, 20C, 25C and 30C, respectively.

Shang, Weili; Kong, Lingyong; Ji, Xuewen

2014-12-01

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 ?1.3gcm-3, and mesoporous characteristic with Brunauer-Emmett-Teller (BET) surface area of 30.6m2g-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 ?6.25נ10-9cm2s-1. The electrochemical performance can achieve about 100 and 90mAhg-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

Lithium Potential Variations for Metastable Materials: Case Study of Nanocrystalline and Amorphous LiFePO4.  

PubMed

Much attention has been paid to metastable materials in the lithium battery field, especially to nanocrystalline and amorphous materials. Nonetheless, fundamental issues such as lithium potential variations have not been pertinently addressed. Using LiFePO4 as a model system, we inspect such lithium potential variations for various lithium storage modes and evaluate them thermodynamically. The conclusions of this work are essential for an adequate understanding of the behavior of electrode materials and even helpful in the search for new energy materials. PMID:25133677

Zhu, Changbao; Mu, Xiaoke; Popovic, Jelena; Weichert, Katja; van Aken, Peter A; Yu, Yan; Maier, Joachim

2014-09-10

64

Cathode properties of phospho-olivine LiMPO 4 for lithium secondary batteries  

Microsoft Academic Search

Four types of orthorhombic olivine LiMPO4 (M:Co, Fe, Ni and Mn) were investigated as high-voltage cathode active materials for lithium secondary batteries. LiCoPO4 exhibited the highest 4.8V discharge plateau of 100mAh\\/g versus Li\\/Li+ after initial charging to 5.1V and its energy density was comparable to that of layered rocksalt LiCoO2 (120mAh\\/g4V=480mWh\\/g). In contrast, the open circuit voltage profile of LiFePO4

Shigeto Okada; Shoichiro Sawa; Minato Egashira; Jun-ichi Yamaki; Mitsuharu Tabuchi; Hiroyuki Kageyama; Tokuzo Konishi; Akira Yoshino

2001-01-01

65

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

66

Sequential Monte Carlo filter for state estimation of LiFePO4 batteries based on an online updated model  

NASA Astrophysics Data System (ADS)

Battery state monitoring is one of the key techniques in battery management systems e.g. in electric vehicles. An accurate estimation can help to improve the system performance and to prolong the battery remaining useful life. Main challenges for the state estimation for LiFePO4 batteries are the flat characteristic of open-circuit-voltage over battery state of charge (SOC) and the existence of hysteresis phenomena. Classical estimation approaches like Kalman filtering show limitations to handle nonlinear and non-Gaussian error distribution problems. In addition, uncertainties in the battery model parameters must be taken into account to describe the battery degradation. In this paper, a novel model-based method combining a Sequential Monte Carlo filter with adaptive control to determine the cell SOC and its electric impedance is presented. The applicability of this dual estimator is verified using measurement data acquired from a commercial LiFePO4 cell. Due to a better handling of the hysteresis problem, results show the benefits of the proposed method against the estimation with an Extended Kalman filter.

Li, Jiahao; Klee Barillas, Joaquin; Guenther, Clemens; Danzer, Michael A.

2014-02-01

67

Direct growth of FePO4/graphene and LiFePO4/graphene hybrids for high rate Li-ion batteries  

NASA Astrophysics Data System (ADS)

FePO4/graphene and LiFePO4/graphene hybrids have been synthesized by an eco-friendly RAAP-directed growth method. With this strategy, FePO4 and LiFePO4 particles have been grown on the exfoliated graphene-assembled scaffolds. Both of the hybrids present superior electrochemical properties, i.e., high rate capability combined with good capacity retention upon cycling, indicating the great potential as the cathode materials for Li-ion batteries.

Fan, Qi; Lei, Lixu; Xu, Xingyu; Yin, Gui; Sun, Yueming

2014-07-01

68

Olivine Thermometry  

NSDL National Science Digital Library

This assignment is ostensibly about geothermometry, but is also part of a sequence of assignments where students learn about mineral components â what they represent (in regards to solid solution phenomena especially), and how they calculated. I begin with olivine because its components are simple, and reasonably good thermometers do not require long equations. I also use this assignment to teach about binary solid solutions and phase diagrams, though the interpretations of such are based within other assignments. This is part of a sequence of assignments where students learn about mineral components â what they represent (in regards to solid solution phenomena especially), and how they calculated. Though students will not use a binary solid solution diagram per se, I use this HW assignment to re-emphasize such concepts. This assignment also allows students to begin tests of equilibrium, so they must understand the concept and use of an equilibrium constant.

Putirka, Keith

69

Challenges in synthesizing carbon-coated LiFePO4 nanoparticles from hydrous FePO4 and their electrochemical properties  

E-print Network

,22]. The resulting water solution contained polyaniline-coated FePO4. A vacuum filter with a $50 nm-pore membrane was used to collect the precipitates. After filtering, the obtained greenish powder was dried under vacuum that the low electronic conductivity of LiFePO4 (

Park, Byungwoo

70

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

71

Forming-free resistive switching memory based on LiFePO4 nano-particle embedded in conjugated polymer  

NASA Astrophysics Data System (ADS)

In this paper, we report the resistive switching characteristics of organic-inorgainc nanocomposite layer of LiFePO4 nano-particle (NP) embedded in conjugated polymer P3HT (P3HT:LiFePO4-NP). Memory devices with Al/P3HT/P3HT:LiFeP4-NP/ITO structure exhibit forming-free bipolar resistive switching behavior under bias voltage sweeping. Our devices achieved low set (??1.2 V) and reset voltage (??0.7 V), excellent data retention, high memory margin of more than 105 on/off resistance ratio and data endurance >100 times, indicating their great potential for memory application. The resistive switching mechanism was investigated by c-AFM measurement and temperature-current dependence results based on conductive filament model. It is deduced that the metallic filament was formed by diffusion and redox of Li+ ion under bias.

Liang, Jun; Su, YanTao; Lin, Qinxian; Zhou, Hang; Zhang, ShengDong; Pei, Yanli; Hu, RuiQin

2014-11-01

72

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

73

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

74

Synthesis of LiFePO4/C cathode materials by carbothermal reduction method using two kinds of Fe3+ precursors  

NASA Astrophysics Data System (ADS)

LiFePO4/C cathode materials were synthesized by carbothermal reduction method using FePO4 and citrate ferric (FeC6H5O75H2O) as Fe3+ precursors. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectrometry (XPS) and charge-discharge test. The results showed that both the crystallization degree and particle size increased markedly with the increase of synthesis temperature. Among the synthesized cathode materials, LiFePO4/C prepared at 650C showed the best electrochemical properties with an initial discharge specific capacity of 138 mAhg-1 at 0.2 C, 128 mAhg-1 at 0.5 C and 116 mAhg-1 at 1.0 C, respectively.

Zhong, M. E.; Zhou, Z. T.

2009-09-01

75

Size Control of LiFePO4/C Cathode Material by Surface Treated FePO4 with Citric Acid  

NASA Astrophysics Data System (ADS)

Size controllable LiFePO4/C composite with good electrochemical properties was synthesized via a novel FePO42H2O-based route: citric acid was used to partly dissociate FePO4 starting material and to chelate the dissolved ferric ions, where the size and morphology of FePO4 were controlled by adjusting the amount of citric acid. The LiFePO4/C composites synthesized with citric acid present high specific capacities (149.8 mAhg-1 at 0.2 C) and good rate performances (141.3 mAhg-1 at 1 C, 131.9 mAhg-1 at 2 C, and 107.0 mAhg-1 at 5 C), which can be attributed to small particle sizes and better carbon coating. The present route is economic and efficient, and suitable for mass production of LiFePO4 cathode material.

Hong, Jianhe; Lv, Lu; Wang, Yanfen; He, Mingzhong; He, Gang

2013-07-01

76

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

PubMed

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

Li, Zhan Jun; Ali, Ghafar; Kim, Hyun Jin; Yoo, Seong Ho; Cho, Sung Oh

2014-01-01

77

Cell degradation in commercial LiFePO4 cells with high-power and high-energy designs  

NASA Astrophysics Data System (ADS)

A quantitative analysis is presented to determine the degradation modes attributing to capacity fade in commercial LiFePO4 cells with high-power (HP) and high-energy (HE) designs. The capacity fade in the HP cell is predominantly due to the loss of lithium inventory. The fade in the HE cell is much more complicated as a function of rate. Using techniques including rest-cell-voltage measurements to track state-of-charge, dQ/dV analysis to trace peak area variations, and mechanistic model simulations (by the Alawa toolbox), the capacity fades in the initial 120 cycles and subsequent aging are analyzed and degradation modes identified. Detailed Alawa simulation with careful experimental validation explains the complexity of degradation in the HE cell. Peculiar rate-dependent initial capacity increases at rates higher than C/5 was likely attributed to electrochemical milling, resulting in active surface area increases and reduced polarization resistance (as the actual current density in the positive electrode was reduced). The mechanistic model and simulation capability illustrates the merits of this unique diagnostic approach with unprecedented holistic quantitative resolution for complicated cell degradation that seems hardly resolvable by other diagnostic methods.

Dubarry, Matthieu; Truchot, Cyril; Liaw, Bor Yann

2014-07-01

78

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

79

Electronic structure of phospho-olivines LixFePO4 (x=0,1) fromsoft-x-ray-absorption and -emission spectroscopies  

SciTech Connect

The electronic structure of the phospho-olivine LixFePO4 wasstudied using soft-x-ray-absorption (XAS) and emission spectroscopies.Characteristic changes in the valence and conduction bands are observedupon delithation of LiFePO4 into FePO4. In LiFePO4, the Fe-3d states arelocalized with little overlap with the O-2p states. Delithiation ofLiFePO4 gives stronger hybridization between Fe-3d states and O-2p statesleading to delocalization of the O-2p states. The Fe L-edge absorptionspectra yield "fingerprints" of the different valence states of Fe inLiFePO4 and FePO4. Resonant soft-x-ray-emission spectroscopy at the Fe Ledge shows strong contributions from resonant inelastic soft x-rayscattering (RIXS), which is described using an ionic picture of the Fe-3dstates. Together the Fe L-edge XAS and RIXS study reveals a bondingcharacter of the Fe 3d-O2p orbitals in FePO4 in contrast to a nonbondingcharacter in LiFePO4.

Augustsson, A.; Zhuang, G.V.; Butorin, S.M.; Osorio-Guillen,J.M.; Dong, C.L.; Ahuja, R.; Chang, C.L.; Ross, P.N.; Nordgren, J.; Guo,J.-H.

2005-07-17

80

A novel sol-gel method based on FePO42H2O 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 FePO42H2O as both iron and phosphorus sources and oxalic acid (H2C2O42H2O) as both complexant and reductant. In H2C2O4 solution, FePO42H2O 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

81

Improvement of electrochemical performance for spherical LiFePO4 via hybrid coated with electron conductive carbon and fast Li ion conductive La0.56Li0.33TiO3  

NASA Astrophysics Data System (ADS)

The LiFePO4/(C+La0.56Li0.33TiO3) composites with spherical morphology are synthesized for the first time via ammonia assisted hydrothermal method. The structure and electrochemical performance of LiFePO4/(C+La0.56Li0.33TiO3) are investigated by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), charge/discharge tests and cyclic voltammetry (CV). It has been found that the hybrid coating layer composing of electron conductive C and fast Li ion conductive La0.56Li0.33TiO3 is synchronously deposited on the surface of LiFePO4 microspheres. The hybrid coating layer can be favourable for fast electron and Li+ transport, and avoid HF eroding LiFePO4 in electrolyte, thus improve the electrochemical performance. The initial discharge capacity of LiFePO4/(C+La0.56Li0.33TiO3) is 126.3mAhg-1, the capacity retention is still as high as 98.3% even after 100 cycles at 5C. Even at high rate of 30C, it still reveals a high discharge capacity of 62.3mAhg-1.

Shu, Hongbo; Chen, Manfang; Fu, Yanqing; Yang, Xiukang; Yi, Xin; Bai, Yansong; Liang, Qianqian; Wei, Qiliang; Hu, Benan; Tan, Jinli; Wu, Chun; Zhou, Meng; Wang, Xianyou

2014-04-01

82

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

PubMed

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

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

2013-04-26

83

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; Edstrm, Kristina

2014-08-01

84

Structural evolution in LiFePO4-based battery materials: In-situ and ex-situ time-of-flight neutron diffraction study  

NASA Astrophysics Data System (ADS)

Neutron diffraction has been used for in-situ studying of the charge-discharge processes in commercial lithium batteries with LiFePO4 (LFP) and graphite electrodes. The diffraction data were obtained with time-of-flight diffractometer in the process of three complete charge-discharge cycles performed at a low rate (0.1C) at room temperature. The experimental data allowed detailed tracing of the multistage process of Li insertion into graphite followed by the formation of several LiCn phases, as well as the reversible transition of LiFePO4?FePO4. A comparison of the charge-discharge processes in a battery with a pure LFP cathode and LFP containing ?1% of vanadium (LFPV) is made. In the second case, an evidently larger part of the anode material passes into the final LiC6 state. Analysis of the diffraction patterns of LFP and LFPV powders revealed a marked shrinkage of crystallite size in the LFPV case, which correlates with better electrochemical properties of LFPV compared to LFP.

Bobrikov, I. A.; Balagurov, A. M.; Hu, Chih-Wei; Lee, Chih-Hao; Chen, Tsan-Yao; Deleg, Sangaa; Balagurov, D. A.

2014-07-01

85

Simulation of effect of interfacial lithium flux on miscibility gap innon-equilibrium phase transformation of LiFePO4 particles  

NASA Astrophysics Data System (ADS)

Non-equilibrium phase transformation and effect of interfacial Li flux on miscibility gap in two-phase transformation of LiFePO4 have been explored in this study. Our previously developed Mushy-Zone (MZ) model, accounting for sluggish Li diffusion across the two-phase interface, has been employed to study the non-equilibrium phase transformation in LiFePO4 materials of Li-ion batteries. Phase transformation rate, variation of two-phase miscibility gap, and interfacial Li composition profiles have been studied for different particle shapes at varying discharge rates. Sluggish Li flux across the two-phase interface, which is believed to be the origin of the kinetically-induced non-equilibrium phase transformation, has been calculated to explain the obtained results. It is found that small particle sizes (radii of 20nm) and slow discharge rates tend to create homogenous phase transformation (i.e., shrunk or no miscibility gap). Two-phase transformation is remarkably delayed for spherical particles at low discharge rates, leading to a lower capacity compared to that of plated-shaped particles. However, at higher discharge rates spherical particles show better capacity.

Siddique, N. A.; Allen, Ashley M.; Mukherjee, Partha P.; Liu, Fuqiang

2014-01-01

86

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

87

Microbial Weathering of Olivine  

NASA Astrophysics Data System (ADS)

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.

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

2002-03-01

88

Olivine-liquid equilibrium  

Microsoft Academic Search

A number of experiments have been conducted in order to study the equilibria between olivine and basaltic liquids and to try and understand the conditions under which olivine will crystallize. These experiments were conducted with several basaltic compositions over a range of temperature (11501300 C) and oxygen fugacity (10-0.6810-12 atm.) at one atmosphere total pressure. The phases in these experimental

P. L. Roeder; R. F. Emslie

1970-01-01

89

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

90

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; Edstrm, Kristina

2014-07-01

91

Sintering of olivine and olivine-basalt aggregates  

Microsoft Academic Search

The sintering behavior of olivine and olivine-basalt aggregates has been examined at temperatures near 1,300 C. Experimental factors contributing to rapid sintering kinetics and high-density, fine-grained specimens include: (i) the uniform dispersion of basalt throughout the specimen, (ii) a very fine, uniform particle size for the olivine powder, (iii) oxygen fugacities near the high PO2 end of the olivine stability

R. F. Cooper; D. L. Kohlstedt

1984-01-01

92

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 Vestas 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 Vestas mantle material implies constraints on its inner structure, e.g. the depth of the crust.

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

2014-11-01

93

Olivine Crystal Structure  

NSDL National Science Digital Library

This exercise is based on recent crystallographic research on the olivine crystal structure published by Redfern et al. (2000). The authors of this study synthesized Fa50 olivine olivine (MgFeSiO4) in an experimental apparatus at temperatures ranging from 100 to 1250 °C, quenched the experiments, and used in situ neutron powder diffraction techniques to investigate changes in the synthesized olivines as a function of temperature. While this study reports cutting-edge materials research carried out with the latest crystallographic techniques, the results are educationally instructive and illustrate important concepts normally covered in an undergraduate mineralogy course. In this exercise, students are guided into the American Mineralogist Crystal Structure Database to retrieve and download published crystal structure data for viewing in either the CrystalMaker or XtalDraw visualization software packages. The students are instructed on how to manipulate the structures and are asked to plot some of the crystallographic data from this study on graphs using a spreadsheet program such as Excel.

Ratajeski, Kent

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

Electrical conduction in olivine  

Microsoft Academic Search

This paper reports detailed measurements of electrical conductivitysigma and thermoelectric effect \\/ital S\\/ in the mineral olivine and in syntheticforsterite as functions of temperature in the range from 1000\\/degree\\/ to1500 \\/degree\\/C and oxygen partial pressure in the range from 10\\/sup \\/minus\\/10\\/ to10⁴ Pa. The two most striking observations are strong conductivityanisotropy in forsterite and a sign change in \\/ital S\\/

Robert N. Schock; Alfred G. Duba; Thomas J. Shankland

1989-01-01

96

Electrical Conductivity of Olivine  

Microsoft Academic Search

The electrical conductivity a of single crystals of olivine of 0, 7.7, 8.2, 9.4, and 26.4 mole % fayalite has been measured up to 1200C and 7.5 kb. Samples from different localities with approximately the same fayalite content and impurity levels have electrical conductivities that differ by 2-3 orders of magnitude. It is proposed that the oxidation state of the

Al Duba

1972-01-01

97

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

98

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 2.3Ah 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 22C. 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 Hgstrm, Katarzyna; Lindstrm, Rakel Wreland; Berg, Helena; Gustafson, Torbjrn; Lindbergh, Gran; Edstrm, Kristina

2014-07-01

99

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 250-950C: 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 700C 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

100

Nano-network electronic conduction in iron and nickel olivine phosphates.  

PubMed

The provision of efficient electron and ion transport is a critical issue in an exciting new group of materials based on lithium metal phosphates that are important as cathodes for lithium-ion batteries. Much interest centres on olivine-type LiFePO(4), the most prominent member of this family. Whereas the one-dimensional lithium-ion mobility in this framework is high, the electronically insulating phosphate groups that benefit the voltage also isolate the redox centres within the lattice. The pristine compound is a very poor conductor (sigma approximately 10(-9) S cm(-1)), thus limiting its electrochemical response. One approach to overcome this is to include conductive phases, increasing its capacity to near-theoretical values. There have also been attempts to alter the inherent conductivity of the lattice by doping it with a supervalent ion. Compositions were reported to be black p-type semiconductors with conductivities of approximately 10(-2) S cm(-1) arising from minority Fe(3+) hole carriers. Our results for doped (and undoped) LiMPO(4) (M = Fe, Ni) show that a percolating nano-network of metal-rich phosphides are responsible for the enhanced conductivity. We believe our demonstration of non-carbonaceous-network grain-boundary conduction to be the first in these materials, and that it holds promise for other insulating phosphates. PMID:14991015

Herle, P Subramanya; Ellis, B; Coombs, N; Nazar, L F

2004-03-01

101

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 700C 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

102

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

103

Defects in Microwave Solvothermally Grown Phospho-Olivine Nanoparticles  

SciTech Connect

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

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

2013-01-01

104

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.; Lebgue, S.; Larsson, P.; Ahuja, R.

2009-08-01

105

Olivine-dominated asteroids: Mineralogy and origin  

NASA Astrophysics Data System (ADS)

Olivine-dominated asteroids are a rare type of objects formed either in nebular processes or through magmatic differentiation. The analysis of meteorite samples suggest that at least 100 parent bodies in the main belt experienced partial or complete melting and differentiation before being disrupted. However, only a few olivine-dominated asteroids, representative of the mantle of disrupted differentiated bodies, are known to exist. Due to the paucity of these objects in the main belt their origin and evolution have been a matter of great debate over the years. In this work we present a detailed mineralogical analysis of twelve olivine-dominated asteroids. We have obtained near-infrared (NIR) spectra (0.7-2.4 ?m) of asteroids (246) Asporina, (289) Nenetta, (446) Aeternitas, (863) Benkoela, (4125) Lew Allen and (4490) Bamberry. Observations were conducted with the Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i. This sample was complemented with spectra of six other olivine-dominated asteroids including (354) Eleonora, (984) Gretia, (1951) Lick, (2501) Lohja, (3819) Robinson and (5261) Eureka obtained by previous workers. Within our sample we distinguish two classes, one that we call monomineralic-olivine asteroids, which are those whose spectra only exhibit the 1 ?m feature, and another referred to as olivine-rich asteroids, whose spectra exhibit the 1 ?m feature and a weak (Band II depth 4%) 2 ?m feature. For the monomineralic-olivine asteroids the olivine chemistry was found to range from Fo49 to Fo70, consistent with the values measured for brachinites and R chondrites. In the case of the olivine-rich asteroids we determined their olivine and low-Ca pyroxene abundance using a new set of spectral calibrations derived from the analysis of R chondrites spectra. We found that the olivine abundance for these asteroids varies from 0.68 to 0.93, while the fraction of low-Ca pyroxene to total pyroxene ranges from 0.6 to 0.9. A search for dynamical connections between the olivine-dominated asteroids and asteroid families found no genetic link (of the type core-mantel-crust) between these objects.

Sanchez, Juan A.; Reddy, Vishnu; Kelley, Michael S.; Cloutis, Edward A.; Bottke, William F.; Nesvorn, David; Lucas, Michael P.; Hardersen, Paul S.; Gaffey, Michael J.; Abell, Paul A.; Corre, Lucille Le

2014-01-01

106

Exsolved Ferromagnesian Olivine: Why Only in Divnoe?  

NASA Astrophysics Data System (ADS)

Recently Petaev and Brearley [1] showed that lamellar structure in olivine grains in the Divnoe meteorite was produced by the low-temperature exsolution of primary homogeneous grains. Exsolved olivine in Divnoe is in accordance with the thermodynamic model of olivine solid solution of [2], which predicts a miscibility gap in ferromagnesian olivines below ~340 degrees C within a compositional range that widens with decreasing temperature. Experiments on the coexistence of olivines having a range of compositions with aqueous solutions of (Fe,Mg)Cl2 [3] suggest that exsolution in ferromagnesian olivines could occur even at temperatures as high as ~400 - 450 degrees C. However, [1] remains the only observation of exsolution in natural olivines so far. This means either that (1) the exsolution in Divnoe olivine is unique, or (2) olivine grains in other slowly cooled coarse-grained rocks has not been studied closely enough to detect them. This work attempts to clarify the issue. Olivine grains from selected meteorites (Springwater pallasite, Lowitz mesosiderite, ALHA 84025 brachinite, Gorlovka H3-4 chondrite and Krymka L3 chondrite, and the Calcalong Creek lunar meteorite) and terrestrial rocks (San Carlos forsterite and Rockport fayalite) were studied by EPMA using the same equipment and technique as in [1]. Among meteorites, pallasites and mesosiderites are known to have slowest cooling rates at low temperatures. Olivines in the Springwater pallasite (Fa18) [4] and the Lowitz mesosiderite (Fa15-37) [5] are compositionally comparable with that of Divnoe (Fa23-29) [1], and it was expected that exsolved olivine grains would be found there. Olivines from other samples were studied for comparison. No lamellar structure was observed in BSE images of the olivine grains studied. The variations of Fa contents in olivine grains from all samples but Springwater and Lowitz meteorites display no regular pattern, and are basically within the 2sigma uncertainty range (+/-0.2 mole % Fa). As expected, olivines from the Lowitz mesosiderite and, especially, from the Springwater pallasite display somewhat larger variations, within the ranges of 20.1 - 21.0 and 15.8 -17.7 mole % Fa, respectively. The olivine in Springwater shows a surprisingly regular pattern of minima spaced at ~ 16 micrometers. For reasons that are unclear all 'minima' analyses have low totals (90.47-94.31 wt.%), whereas most other analyses have totals > 97%. However, stoichiometry of all analyses is perfect; cation totals per 4 oxygens are 3.00+/-0.01, with very minor excess of Si over Mg+Fe in the 'minima' analyses. The results obtained so far suggest that lamellar structure of olivine grains in the Divnoe meteorite is unique. While chemical variability is found in the Springwater and Lowitz olivines, there is no lamellar structure, and the magnitude of the variations is 1.5 - 2 times smaller than it is in Divnoe olivines. Since olivine compositions in Divnoe, Lowitz and Springwater are similar, the structural differences among them must be due to different thermal histories. The lack of lamellar structure in the Lowitz olivine implies that even the slowest cooling down to 250 degrees C recorded in mesosiderites [6] does not result in olivine exsolution. It is possible that Divnoe experienced secondary reheating followed by prolonged low-temperature annealing. This would also account for the lack of shock features in the Divnoe opaque minerals [7] and the difference in distributions of cosmic-ray track lengths and densities between olivine and pyroxene [8]. References: [1] Petaev M. I. and Brearley A. J. (1994) Science, 266, 1545-1547. [2] Sack R. O. and Ghiorso M. S. (1989) Contrib. Mineral. Petrol., 102, 41-68. [3] Schulien S. (1980) Contrib. Mineral. Petrol., 74, 85-91. [4] Buseck P. R. (1977) GCA, 41, 711-740. [5] Delaney J. S. et al. (1980) Proc. LPSC 11th, 1073-1087. [6] Ganguly J. et al. (1994) GCA, 58, 2711-2723. [7] Petaev M. I. et al. (1994) Meteoritics, 29, 182-199. [8] Petaev M. I. et al. (1990) LPS XXI, 950-951.

Petaev, M. I.

1995-09-01

107

Unusual olivine zoning --- Evidence for complex physico-chemical changes during the evolution of olivine melilitite and kimberlite magmas  

Microsoft Academic Search

Olivine melilitites from Namaqualand, South Africa are characterized by a broad range in olivine compositions on the scale of individual hand specimens. It is possible to distinguish four petrographically and chemically distinct olivine populations in both the northern and southern pipe clusters studied: (a) Scarce anhedral or subhedral olivines that display marked disequilibrium features with the surrounding matrix, and which

A. E. Moore; A. J. Erlank

1979-01-01

108

Olivine dissolution in sulphuric acid at elevated temperaturesimplications for the olivine process, an alternative waste acid neutralizing process  

Microsoft Academic Search

A kinetic model for the dissolution of olivine in sulphuric acid at elevated temperatures is presented. Such a model is essential for the design of an industrial process for the neutralization of waste acids by olivine, or for the production of precipitated silica from olivine. The effects of temperature, grainsize fraction and olivine amount on the neutralization rate have been

R. C. L. Jonckbloedt

1998-01-01

109

Electrochemical performance of V-doped spinel Li4Ti5O12/C composite anode in Li-half and Li4Ti5O12/LiFePO4-full cell  

NASA Astrophysics Data System (ADS)

This work reports the preparation of a V-doped Li4Ti5O12/C (donated as V-doped LTO/C) composite material, applying a solid-state method. Both metal doping and carbon coating are applied on the Li4Ti5O12 material, enhancing its rate capability and cycle stability. Furan polymer is used as a carbon source, and vanadium (V) is selected as a dopant. The properties of the materials are examined by X-ray diffraction (XRD), micro-Raman, scanning electron microscopy (SEM), high-resolution transmission microscopy (HR-TEM), the AC impedance method, and the galvanostatic charge/discharge method. For comparison, Li4Ti5O12/C composite materials with and without V doping are also examined. The Li4Ti4.90V0.10O12/C composite material achieves discharge capacities of 165.59 and 76.76mAhg-1 at a 0.2/1C and 0.2/20C rate, respectively. A Li4Ti5O12/LiFePO4 full cell (LTO capacity-limited) is constructed and investigated. The full cell exhibits discharge capacities of 181, 178, 167, 142, 110, and 78mAhg-1 at 0.2, 0.5, 1, 3, 5, and 10C, respectively. We determine that the Li4Ti4.95V0.05O12/C composite anode is an outstanding candidate for application in high-power Li-ion batteries.

Yang, Chun-Chen; Hu, Huai-Chou; Lin, S. J.; Chien, Wen-Chen

2014-07-01

110

Atom Probe Tomography of Olivine  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

111

Raman spectra of shocked minerals. I - Olivine  

NASA Technical Reports Server (NTRS)

The Raman spectra of olivine contained in a chip of the Twin Sisters Peak (Washington) dunite shocked to 22.2 GPa is shown to be identical to that of unshocked olivine in the same rock. The Raman spectra of powder of the rock shocked to 20.1 GPa and of chips shocked to 59.5 GPa and 60.7 GPa display strong and broad low-frequency features with crests at 475/cm, 556/cm, and 572/cm, and broad high-frequency features near 1100/cm. It is suggested that these features are due to the formation of olivine glass with a considerable degree of three-dimensional Si-O-Si linkage having scattered domains of greatly variable grain size, internal structure, and chemical composition.

Heymann, D.; Celucci, T. A.

1988-01-01

112

A Chemical Model of Micrometeorite Impact into Olivine  

NASA Technical Reports Server (NTRS)

Laboratory simulations of space weathering using laser irradiation have been successful in reproducing space weathering characteristics such as the reduction of olivine to form nanophase iron particles. However, the chemistry of the reduction of Fe2+ in olivine to Fe metal has not been fully explored. We present a thermodynamic model of olivine undergoing post-impact cooling and decompression.

Sheffer, A. A.; Melosh, H. J.

2005-01-01

113

Water loss from olivine hosted melt inclusions  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

114

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

115

Manganese olivine II: point defect relaxation  

Microsoft Academic Search

To investigate the point defect chemistry and the kinetic properties of manganese olivine Mn2SiO4, the point defect relaxation time (tau) characterizing the rate of re-equilibration of electrical conductivity following a change in oxygen fugacity was measured for single crystals oriented for electrical conduction along the [010] direction. The experiments were carried out at temperatures T = 1173-1473 K and oxygen

Q. Bai; Z.-C. Wang; D. L. Kohlstedt

1998-01-01

116

Manganese olivine II: point defect relaxation  

Microsoft Academic Search

To investigate the point defect chemistry and the kinetic properties of manganese olivine Mn2SiO4, the point defect relaxation time (?) characterizing the rate of re-equilibration of electrical conductivity following a\\u000a change in oxygen fugacity was measured for single crystals oriented for electrical conduction along the [010] direction. The\\u000a experiments were carried out at temperatures T?=?11731473?K and oxygen fugacities with the

Q. Bai; Z.-C. Wang; D. L. Kohlstedt

1998-01-01

117

Mechanisms of electrical conductivity in olivine  

SciTech Connect

Data on the electrical conductivity and the thermoelectric effect in single crystals indicate that the charge conduction mechanism in pure magnesium forsterite is electrons. The concentration of electrons can be varied by controlling the number of oxygen vacancies through manipulation of the oxygen pressure. For iron bearing olivine, the conduction mechanism is by electron holes localized on an iron ion. Since iron strongly affects the creep process as well, oxidation of iron is probably accompanied by the production of magnesium vacancies. 15 references.

Schock, R.N.; Duba, A.G.; Shankland, T.J.

1984-01-01

118

Diffusive behavior in LiMPO4 with M=Fe, Co, Ni probed by muon-spin relaxation  

NASA Astrophysics Data System (ADS)

In order to study the diffusive nature of lithium transition-metal phospho-olivines, we measured muon-spin relaxation (?+SR) spectra for the polycrystalline LiMPO4 samples with M=Mn, Fe, Co, or Ni in the temperature range between 50 and 500 K. The ?+SR spectra under zero applied field are strongly affected by the magnetic moments of the 3d electrons in the M2+ ions so that, for LiMnPO4, it was difficult to detect the relaxation change caused by the diffusion due to the large Mn2+(S=5/2) moments. However, diffusive behavior was clearly observed via the relaxation due to nuclear dipolar fields above 150 K for LiFePO4, LiCoPO4, and LiNiPO4 as S decreased from 2 to 1. From the temperature dependence of the nuclear field fluctuation rate, self-diffusion coefficients of Li+ ions (DLi) at 300 K and its activation energy (Ea) were estimated, respectively, as 3.6(2)10-10 cm2/s and Ea=0.10(2) eV for LiFePO4, 1.6(1)10-10 cm2/s and Ea=0.10(1) eV for LiCoPO4, and 2.7(4)10-10 cm2/s and Ea=0.17(2) eV for LiNiPO4, assuming that the diffusing Li+ ions jump between the regular site and interstitial sites.

Sugiyama, Jun; Nozaki, Hiroshi; Harada, Masashi; Kamazawa, Kazuya; Ikedo, Yutaka; Miyake, Yasuhiro; Ofer, Oren; Mnsson, Martin; Ansaldo, Eduardo J.; Chow, Kim H.; Kobayashi, Genki; Kanno, Ryoji

2012-02-01

119

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

120

Experimental Determination of Scattering Matrices of Olivine  

NASA Astrophysics Data System (ADS)

Mid- and far-infrared spectra have provided striking evidence for the presence of crystalline olivine in comets, circumstellar envelopes and planetary nebulae. In many cases the light scattering properties of these particles are required for the interpretation of observations of these objects. Since many data on the scattering behaviour of irregular mineral particles in general, and of crystalline olivine in particular, are lacking in the literature, we have measured the whole scattering matrix as a function of the scattering angle of a sample of Olivine (Mg2yFe_{2-2y}SiO4 y=0.9) at two wavelengths (633nm and 442nm). In our experimental setup we use a laser as a light source. This light is scattered by randomly oriented particles located in a jet stream. We employ polarization modulation in combination with lock-in detection to obtain all elements of the four-by-four Mueller matrix (Fij), which describes the scattering process. The elements depend on the wavelength of the laser light, the scattering angle as well as size, shape and complex refractive index of the particles. The sample has been prepared so that the measurements have been repeated for three different size distributions: d=6, 32 and 100 microns respectively, where d is the median diameter for volume equivalent spheres. One of the interesting results pertains to the element ratio -F21/F11, which equals the degree of linear polarization for unpolarized incident light. This shows negative values at angles close to the backward direction for the three size distributions and at both wavelengths. Such negative polarization has been observed for many objects in the Solar System. We intend to compare the measured matrix elements with calculated elements using the T-matrix method.

Munoz, O.; Volten, H.; Vermeulen, K.; de Haan, J. F.; Vassen, W.; Hovenier, J. W.

1999-09-01

121

Discovery of Olivine in the Nili Fossae Region of Mars  

USGS Publications Warehouse

We have detected a 30,000-square-kilometer area rich in olivine in the Nili Fossae region of Mars. Nili Fossae has been interpreted as a complex of grabens and fractures related to the formation of the Isidis impact basin. We propose that post-impact faulting of this area has exposed subsurface layers rich in olivine. Linear mixture analysis of Thermal Emission Spectrometer spectra shows surface exposures of 30% olivine, where the composition of the olivine ranges from Fo30 to Fo70.

Hoefen, T.M.; Clark, R.N.; Bandfield, J.L.; Smith, M.D.; Pearl, J.C.; Christensen, P.R.

2003-01-01

122

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

123

S1. Modal olivine abundances of diogenites Most diogenites contain some olivine, usually <5 vol%31  

E-print Network

of such areas vary for the two scenarios. Multispectral images obtained with Hubble Space Telescope (HST) have rotational spectral variations observed with ground-based telescopes3 and two possible maps of the major hemisphere and dominated by more diogenitic minerals. S3. Exogenic source Delivery of olivine by impacts

Cai, Long

124

Olivine in an unexpected location on Vesta's surface.  

PubMed

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. PMID:24196707

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

125

Olivine in the Southern Isidis Basin  

NASA Technical Reports Server (NTRS)

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this observation of the transition region between Libya Montes and the Isidis Basin on Mars at 17:16 UTC (12:16 p.m. EST) on January 2, 2007, near 3.6 degrees north latitude, 84.1 degrees east longitude. The image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 18 meters (60 feet) across. The image is about 11 kilometers (7 miles) wide at its narrowest point.

The Isidis Basin resulted from of a gigantic impact on the surface of Mars early in the planet's history. The southern rim, where this target is located, is a region of complex geology and part of the planetary dichotomy boundary that separates the older southern highlands from the lower, younger northern plains. The image on the left was constructed from three visible wavelengths (RGB: 0.71, 0.60, 0.53 microns) and is a close approximation of how the surface would appear to the human eye. The image on the right was constructed from three infrared wavelengths (RGB: 2.49, 1.52, 1.08 microns) chosen to highlight variations in the mineralogy of the area. Of interest is that features in this image not only differ in color, but also in texture and morphology. The gray areas absorb similarly at all wavelengths used in this image, but display absorptions at other wavelengths related to the iron- and magesium-rich mineral pyroxene. The reddest areas absorb strongly at the wavelengths used for green and blue, which is attributable to another iron- and magesium-rich mineral, olivine. The brownish areas show subdued mineral absorptions and could represent some type of mixture between the other two materials. The presence of the mineral olivine is particularly interesting because olivine easily weathers to other minerals; thus, its presence indicates either the lack of weathering in this region or relatively recent exposure.

CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials -- leading to new understanding of the climate.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.

2007-01-01

126

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 NASAs 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 Vestas 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

127

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

128

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

129

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

130

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. Henrys 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

131

Aluminum speeds up the hydrothermal alteration of olivine  

NASA Astrophysics Data System (ADS)

The reactivity of ultramafic rocks toward hydrothermal fluids 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 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 200C and 300C, and P=200 MPa. After two days, olivine crystals were fully transformed to an aluminous serpentine, also enriched in iron. The presence of Al in the hydrothermal fluid increases the rate of olivine serpentinization by more than one order of magnitude by enhancing olivine solubility and serpentine precipitation. The mechanism responsible for this increased solubility has to be further investigated 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.

Andreani, Muriel; Daniel, Isabelle; Pollet-Villard, Marion

2014-05-01

132

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

133

A Method for the Flux Growth of Intermediate Composition Olivine  

Microsoft Academic Search

Though solid solution of iron and magnesium between forsterite (Mg2SiO4) and fayalite (Fe2SiO4) is possible in the olivine crystal structure, the high oxygen fugacity condition of the terrestrial mantle inhibits the widespread crystallization of intermediate (Fo40-Fo60) composition olivine. This limitation is not the same for some other inner solar system bodies (e.g. the Moon and Mars), where conditions are reducing

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

2009-01-01

134

Anisotropy of magnetic susceptibility in natural olivine single crystals  

NASA Astrophysics Data System (ADS)

flow dynamics can cause preferential alignment of olivine crystals that results in anisotropy of physical properties. To interpret anisotropy in mantle rocks, it is necessary to understand the anisotropy of olivine single crystals. We determined anisotropy of magnetic susceptibility (AMS) for natural olivine crystals. High-field AMS allows for the isolation of the anisotropy due to olivine alone. The orientations of the principal susceptibility axes are related to the olivine's crystallographic structure as soon as it contains >3 wt % FeO. The maximum susceptibility is parallel to the c axis both at room temperature (RT) and at 77 K. The orientation of the minimum axis at RT depends on iron content; it is generally parallel to the a axis in crystals with 3-5 wt % FeO, and along b in samples with 6-10 wt % FeO. The AMS ellipsoid is prolate and the standard deviatoric susceptibility, k', is on the order of 8*10-10 m3/kg for the samples with <1wt % FeO, and ranges from 3.1*10-9 m3/kg to 5.7*10-9 m3/kg for samples with 3-10 wt % FeO. At 77 K, the minimum susceptibility is along b, independent of iron content. The shape of the AMS ellipsoid is prolate for samples with <5 wt % FeO, but can be prolate or oblate for higher iron content. The degree of anisotropy increases at 77 K with p'77 = 7.1 0.5. The results from this study will allow AMS fabrics to be used as a proxy for olivine texture in ultramafic rocks with high olivine content.

Biedermann, Andrea R.; Pettke, Thomas; Reusser, Eric; Hirt, Ann M.

2014-07-01

135

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, J.

2010-01-01

136

Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance  

SciTech Connect

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

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

2006-01-01

137

Textural evolution of polyhedral olivine experiencing rapid cooling rates  

NASA Astrophysics Data System (ADS)

Dynamic crystallization experiments in the CaO MgO Al2O3 SiO2 (CMAS) system have been used to investigate the change in crystal shape when pre-existing polyhedral olivine crystals are cooled rapidly (1,639 2,182C/h). Polyhedral olivines are crystallized initially in a first step using a slow cooling rate (2C/h), then skeletal and dendritic overgrowths develop on the polyhedral crystals during a subsequent fast cooling event. During this second episode small dendritic olivines also nucleate within the liquid phase. Observation of the experimental sample by optical microscopy shows that the polyhedral olivine shape progressively changes to a skeletal and then to a dendritic morphology in the following sequence: polyhedral ? hopper polyhedral ? dendritic polyhedral. This evolutional sequence is discussed in terms of changes in the crystal growth conditions during cooling and a general relation between these olivine dynamic crystallization experiments and the integrated model of crystal growth by Sunagawa (Bull Minr 104:81 87, 1981, Morphology of crystals, Terra Scientific Publishing Company, 1987) is proposed.

Faure, Franois; Schiano, Pierre; Trolliard, Gilles; Nicollet, Christian; Soulestin, Bernard

2007-04-01

138

Early crystallization history of alkali olivine basalts, Diamond Craters, Oregon  

NASA Astrophysics Data System (ADS)

Basaltic lavas form the isolated Quaternary volcanic centers of Diamond Craters and occur at Cow Lakes in S.E. Oregon. The exposed rocks are olivine and plagioclase phyric alkali olivine basalts. The holocrystalline groundmasses contain plagioclase, titanaugite, olivine, Fe-Ti oxides and minor apatite, and occur in the high-alumina (greater than 17%) petrographic province of the northwestern Great Basin. The whole rock and phenocryst compositions provide enough information to define the equilibrium state of the magmas. The solutions to the thermodynamic equations are valid for systems of known bulk composition and can be used to evaluate whether rock compositions are close to magma compositions. Two of the lavas from Diamond Craters have whole rock and phenocryst compositions consistent with their being natural melts. Rock compositions that reflect the effects of crystal separation (open systems) are recognized by significant differences in predicted versus observed phenocryst modes. The P-T conditions of phenocryst saturation and the crystallization history of the magmas can be inferred from petrologic data combined with thermodynamic modelling and mass balance constraints. The initial melts are inferred to have equilibrated at 0.8-1.0 GPa and 1210-1240C. The majority of the lavas from Diamond Craters have compositions that reflect olivine and plagioclase crystal separation. These lavas can be related to two possible parent rock compositions by small amounts (2-8% by weight) of olivine and plagioclase separation.

Russell, J. K.; Nicholls, J.

1987-01-01

139

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

140

Applicability of Henry's Law to helium solubility in olivine  

NASA Astrophysics Data System (ADS)

Applicability of Henry's Law to helium solubility in olivine We have experimentally determined helium solubility in San Carlos olivine across a range of helium partial pressures (PHe) with the goal of quantifying how noble gases behave during partial melting of peridotite. Helium solubility in olivine correlates linearly with PHe between 55 and 1680 bar. This linear relationship suggests Henry's Law is applicable to helium dissolution into olivine up to 1680 bar PHe, providing a basis for extrapolation of solubility relationships determined at high PHe to natural systems. This is the first demonstration of Henry's Law for helium dissolution into olivine. Averaging all the data of the PHe series yields a Henry's coefficient of 3.8(3.1)10-12 mol g-1 bar-1. However, the population of Henry's coefficients shows a positive skew (skewness = 1.17), i.e. the data are skewed to higher values. This skew is reflected in the large standard deviation of the population of Henry's coefficients. Averaging the median values from each experiment yields a lower Henry's coefficient and standard deviation: 3.2( 2.3)10-12 mol g-1 bar-1. Combining the presently determined helium Henry's coefficient for olivine with previous determinations of helium Henry's coefficients for basaltic melts (e.g. 1) yields a partition coefficient of ~10-4. This value is similar to previous determinations obtained at higher PHe (2). The applicability of Henry's Law here suggests helium is incorporated onto relatively abundant sites within olivine that are not saturated by 1680 bar PHe or ~510-9 mol g-1. Large radius vacancies, i.e. oxygen vacancies, are energetically favorable sites for noble gas dissolution (3). However, oxygen vacancies are not abundant enough in San Carlos olivine to account for this solubility (e.g. 4), suggesting the 3x10-12 mol g-1 bar-1 Henry's coefficient is associated with interstitial dissolution of helium. Helium was dissolved into olivine using an externally heated pressure vessel (Brown University). The starting materials were prepared by cutting gem-quality San Carlos olivine (~Fo90) into small blocks (~421 mm) using a diamond wafering blade saw and polishing with alumina slurries and colloidal silica. Analysis was completed by laser ablation-mass spectrometry using a 193 nm excimer laser and a MAP 215-50 specifically tuned for He (Open University, UK). Laser ablation pit depth varied from 2 to 40 ?m, and no correlation between pit depth and [He] is observed after accounting for variations PHe across the different experiments. This lack of correlation indicates a close approach to equilibrium was achieved over the experimental durations. Two analyses yielded spuriously high [He] (>3 std. dev. from the population mean, n = 85), and these analyses were not used to calculate Henry's coefficients. The two spuriously high analyses, in combination with the right skew of Henry's coefficients calculated from individual data points, suggests gem-quality San Carlos olivine contains volumes with anomalously high helium solubility. The nature of these volumes is currently under investigation. However, despite their presence, helium is still highly incompatible in olivine during partial melting. [1] Lux GCA 1987 [2] Heber et al. GCA 2007 [3] Shcheka & Keppler Nature 2012 [4] Walker et al. PEPI 2009

Jackson, C.; Parman, S. W.; Kelley, S. P.; Cooper, R. F.

2013-12-01

141

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

142

Electrical Conductivity of Hydrous Single Crystal San Carlos Olivine  

NASA Astrophysics Data System (ADS)

The electrical conductivity of anhydrous San Carlos olivine is too low to explain the observed electrical conductivity of Earth's upper mantle. Although the solubility of hydrogen in olivine is relatively low at mantle P and T conditions, it has been estimated that even at concentrations of less than 1000 ppm, electrical conductivity is enhanced by as much as a factor of one hundred, based on a conduction mechanism involving hydrogen diffusion (Karato, Nature 347, 272-273, 1990). In this study we have measured the electrical conductivity of hydrated San Carlos olivine single crystals, oriented along (100), (010) and (001). SCO single crystals were first oriented, machined into 2 mm diameter cylinders, and then sandwiched between layers of a talc+brucite mix in sealed Pt capsules for hydration runs at pressures up to 8 GPa and 1200C in a multianvil apparatus. Recovered samples were then cut into wafers ranging from 0.2 to 0.6 mm in thickness for subsequent complex impedance measurements to determine electrical conductivity, also carried out at high pressure. For the electrical measurements, temperatures were limited to about 700C in order to minimize loss of water from the sample. FTIR spectroscopy was used to determine water content of samples both before and after the electrical measurements. Preliminary results indicate that at concentrations of a few hundred ppm water, conductivities are several orders of magnitude higher than for dry olivine. Activation energies decrease with increasing water content, indicating that extrapolation of conductivities to higher temperatures leads to a smaller overall effect. However, based on these results, at upper mantle conditions, the presence of minor amounts of hydrogen in olivine is sufficient to bridge the gap between the conductivity of dry olivine and that of the mantle.

Poe, B.; Romano, C.; Nestola, F.; Rubie, D.

2005-12-01

143

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 (k13-44), 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

144

Grain Boundary Structurally-Bonded Water in Olivine Aggregates  

NASA Astrophysics Data System (ADS)

Water storage capacity of nominally anhydrous olivine has been extensively investigated because of its numerous geophysical and geochemical implications for the Earth's dynamic mantle. However, all previous experimental research has been concentrated on the water solubility in single crystals of olivine. Grain boundary as potential storage sites for water in the mantle has not been experimentally studied, in part because solubility experiments were always performed under water-saturated condition, rendering the examination of grain boundaries nearly impossible due to the presence of free water. In the present study we have conducted annealing experiments on forsterite at 5 - 6 GPa and 1200 C and at water- undersaturated condition. Duration was typically 2 - 3 hours. A small amount of enstatite or periclase was added to the starting forsterite powder (including a few large olivine grains) to buffer the silica activity, while oxygen fugacity was controlled by using various capsule materials (Re, Fe, or BN). FTIR analyses were performed on both single crystal and polycrystalline olivine in doubly-polished thin section of each experimental charge. The results are as follows: (1) single crystal and polycrystalline olivine in the same charge always yielded similar IR pattern, indicating all absorption peaks are due to similar structurally-bonded water (i.e., hydroxyl); (2) water content of periclase-buffered (i.e., low silica activity) sample is at least one order of magnitude higher than those of enstatite-buffered and unbuffered (pure forsterite) samples; (3) under reducing environment (Fe or BN capsule), water content of polycrystalline olivine is always higher than that of single crystal by at lease a factor of 5, regardless of silica activity buffering. We therefore infer that large amount of structurally-bonded water is stored at grain boundaries; (4) with decreasing oxygen fugacity, IR spectra of olivine are increasingly dominated by an absorption peak centered around 3600 cm-1, indicating a gradual change in dominant water incorporation mechanism in olivine. These results strongly suggest that grain boundaries could be significant storage sites for water in the Earth's mantle, especially at locations where oxygen fugacity and silica activity are low.

Wang, L.

2008-12-01

145

BROWN AND CLEAR OLIVINE IN CHASSIGNITE NWA 2737: WATER AND DEFORMATION. A.H. , M. McCanta1  

E-print Network

section plane show interfingering bands and flame-shaped patches of vc olivine traversing the brown chemical composition and orientations in the host brown olivine. VC olivine has the same bulk chemical chemical transformation. The differences in color and

Hiroi, Takahiro

146

Trace Element Compositions of Pallasite Olivine Grains and Pallasite Origin  

NASA Technical Reports Server (NTRS)

Pallasites are mixtures of metal with magnesian olivine. Most have similar metal compositions and olivine oxygen isotopic compositions; these are the main-group pallasites (PMG). The Eagle Station grouplet of pallasites (PES) have distinctive metal and olivine compositions and oxygen isotopic compositions. Pallasites are thought to have formed at the core-mantle boundary of their parent asteroids by mixing molten metal with solid olivine of either cumulatic or restitic origin. We have continued our investigation of pallasite olivines by doing in situ trace element analyses in order to further constrain their origin. We determined Al, P, Ca, Ga and first row transition element contents of olivine grains from suite of PMG and PES by LA-ICP-MS at JSC. Included in the PMG suite are some that have anomalous metal compositions (PMG-am) and atypically ferroan olivines (PMG-as). Our EMPA work has shown that there are unanticipated variations in olivine Fe/Mn, even within those PMG that have uni-form Fe/Mg. Manganese is homologous with Fe2+, and thus can be used the same way to investigate magmatic fractionation processes. It has an advantage for pallasite studies in that it is unaffected by redox exchange with the metal. PMG can be divided into three clusters on the basis of Mn/Mg; low, medium and high that can be thought of as less, typically and more fractionated in an igneous sense. The majority of PMG have medium Mn/Mg ratios. PMG-am occur in all three clusters; there does not seem to be any relationship between putative olivine igneous fractionation and metal composition. The PMG-as and one PMG-am make up the high Mn/Mg cluster; no PMG are in this cluster. The high Mn/Mg cluster ought to be the most fractionated (equivalent to the most Fe-rich in igneous suites), yet they have among the lowest contents of incompatible lithophile elements Al and Ti and the two PMG-as in this cluster also have low Ca and Sc contents. This is inconsistent with simple igneous fractionation on a single, initially homogeneous parent asteroid. For Al and Ti, the low and high Mn/Mg clusters have generally uniform contents, while the medium cluster has wide ranges. This is also true of analyses of duplicate grains from the medium cluster pallasites which can have very different Al and Ti contents. Those from the low and high clusters do not. These observations suggest that pallasite olivines are not cumulates, but rather are restites from high degrees of melting. The moderately siderophile elements P and Ga show wide ranges in the high Mn/Mg cluster, but very uniform compositions in the medium cluster, opposite the case for Al and Ti. There is no correlation of P or Ga and Fe/Mn as might be expected if redox processes controlled the contents of moderately siderophile elements in the olivines. The lack of correlation of P could reflect equilibration with phosphates, although there is no correlation of Ca with P as might be expected

Mittlefehldt, David W.; Herrin, J. S.

2010-01-01

147

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

148

The electrical conductivity of an isotropic olivine mantle  

Microsoft Academic Search

In order to extend the useful temperature range of interpretation of olivine electrical conductivity sigma, the nonlinear iterative Marquardt technique is used to fit experimental data over the range 720-1500 C to a parametric form. The model describes conduction by migration of two different thermally activated defect populations with activation energies A1 and A2, and preexponential terms sigma (1) and

Steven Constable; Thomas J. Shankland; Al Duba

1992-01-01

149

Effect of secondary phase formation on the carbonation of olivine.  

PubMed

Large-scale olivine carbonation has been proposed as a potential method for sequestering CO(2) emissions. For in situ carbonation techniques, understanding the relationship between the formation of carbonate and other phases is important to predict the impact of possible passivating layers on the reaction. Therefore, we have conducted reactions of olivine with carbonated saline solutions in unstirred batch reactors. Altering the reaction conditions changed the Mg-carbonate morphology. We propose that this corresponded to changes in the ability of the system to precipitate hydromagnesite or magnesite. During high-temperature reactions (200 degrees C), an amorphous silica-enriched phase was precipitated that was transformed to lizardite as the reaction progressed. Hematite was also precipitated in the initial stages of these reactions but dissolved as the reaction proceeded. Comparison of the experimental observations with reaction models indicates that the reactions are governed by the interfacial fluid composition. The presence of a new Mg-silicate phase and the formation of secondary products at the olivine surface are likely to limit the extent of olivine to carbonate conversion. PMID:20704252

King, Helen E; Plmper, Oliver; Putnis, Andrew

2010-08-15

150

The geoengineering potential of artificially enhanced silicate weathering of olivine  

Microsoft Academic Search

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

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

2010-01-01

151

How robust are melt inclusions in olivine for mantle study?  

NASA Astrophysics Data System (ADS)

Melt inclusions in olivine are commonly used to address composition of mantle sources and processes of mantle melting. Here I will assess basic assumption of such studies: ability of melt inclusions to preserve chemical characteristics of parental melts formed in the mantle. Using published and new data I will demonstrate that olivines generally trap their melt inclusions during shallow crystallization in the crust by fast growth in the thermal boundary layers of mixing magma batches. Whether such trapped melts represent parental melts or they were modified by reaction on route could be recognized by chemical evidence of shallow equilibrium with plagioclase or pyroxene. Some inclusions reveal post-trapping modification of heaviest REE and H2O by volume diffusion through host olivine as predicted by the high diffusion coefficients for these elements in olivine (e.g . Spandler et al, Nature 2007 and Portnyagin et al, EPSL 2008). However, the contents of the middle and light REE and those of all highly incompatible trace elements are fully preserved. I conclude that (1) time scales in the magmatic system are short enough to preserve the abundances of highly and moderately incompatible elements inherited from primary melts, and (2) there is no evidence that wall-rock interaction has contributed significantly to the incompatible-element composition of Hawaiian melt inclusions.

Sobolev, A. V.

2008-12-01

152

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

153

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

154

Oxygen isotope heterogeneity and disequilibria of olivine crystals in large volume Holocene basalts from Iceland: Evidence  

E-print Network

and compositional zoning in selected grains, and subtle to severe D18 O (melt-olivine) and D18 O (plagioclase isotope laser fluorination analyses of 55 individual and bulk olivine crystals, coexisting individual different lavas, and variable core-to-rim oxygen isotopic zoning is present in selected olivine grains. Many

Bindeman, Ilya N.

155

Effect of water and stress on the lattice-preferred orientation of olivine  

E-print Network

) of olivine aggregates was investigated through large strain, shear deformation experiments at high pressures are hot-pressed synthetic olivine aggregates or single crystals of olivine. Water was supplied to the sample by decomposition of a mixture of talc and brucite. Deformation experiments were conducted up

Jung, Haemyeong

156

Evidence for equilibrium conditions during the partitioning of nickel between olivine and komatiite liquids.  

USGS Publications Warehouse

Olivine-liquid partition coefficients for Ni(DNi), calculated from Ni vs MgO abundance variations in komatiite series basalts, compare favourably with experimentally determined values, if Ni variations in olivine-controlled basalts can be modelled with an equation that assumes equilibrium between the entire olivine crystal and its coexisting liquid.-J.A.Z.

Budahn, J. R.

1986-01-01

157

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

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

2010-11-23

158

Geoengineering potential of artificially enhanced silicate weathering of olivine  

PubMed Central

Geoengineering is a proposed action to manipulate Earths 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 1Pg 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 0.4Pg of olivine seems possible, corresponding to the sequestration of 0.5 and 0.1Pg 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 15Pg of C per year for the 21st century by this technique. PMID:21059941

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

2010-01-01

159

Lattice preferred orientations of olivine in the schistosed antigorite serpentinite  

NASA Astrophysics Data System (ADS)

The lattice preferred orientation (LPO) of the schistosed antigorite serpentinite is considered as causes of the seismic anisotropy observed at the subduction zones (Katayama et al., 2009; Jung, 2011) and the natural examples are reported by several researchers (Bezacier et al., 2010; Hirauchi et al., 2010; Soda and Takagi, 2010). Formation process of the antigorite LPO is unclear, especially at primary serpentinized stage. To understand the development of micro-structures of antigorite serpentinite, we made structural analyses of serpentinite schist and the former peridotite fabric. Samples were taken from lenticular serpentinite bodies (< 1km) stack in Jurassic accretionary complex, Toba area, Southwest Japan. The serpentinite consist of olivine, antigorite, meta-clinopyroxene and Cr-spinel. The foliation and lineation of serpentinite is defined by parallel alignment of elongated olivine grain and antigorite blades, which make up mylonitic textures, such as a porphyroclast system and composite planar fabric. Antigorite blades show syn-kinematic growth in pressure shadows and pull-apart of olivine porphyroclast. In the less serpentinized part, antigorite blades are crystallized along the grain boundary of olivine. We measure the LPOs of coarse olivine grains in the serpentinite schist using a u-stage. The X, Y and Z directions represent directions of lineation, normal to lineation within the foliation and normal to foliation, respectively. The LPOs of olivine show point maximum or partial girdle distribution, and these concentrated crystal axes are incongruous with X, Y and Z direction. The a[100] axes of olivine are parallel to the serpentinite foliation, and form a point maximum several degrees away from the Y direction. The b[010] axes and the c[001] axes are concentrated Z and X direction forming a partial girdle normal to Y direction, respectively. Boudier et al. (2010) have reported the topotactic relationship between olivine and antigorite. They show that the (100)ol is parallel to the (001)atg or the (010)ol is parallel to the (001)atg. And, the a[100] axes of olivine are normal to serpentinite foliation with point maximum in the thin section scale. However, in the case of this study, the simple topotactic relationship does not connect the fabric in the thin section scale of serpentinite schist. Although, more detail analysis need to discuss the formation of antigorite LPO, the other mechanisms, such as crystal plastic deformation or diffusion-precipitation, might cause rearrangement of antigorite fabric. References Bezacier, L. et al., 2010, Earth and Planetary Science Letters, 289, 198-208. Boudier, F. et al., 2010, Journal of Petrology 51, 495-512. Hirauchi et al., 2010, Earth and Planetary Science Letters, 299, 196-206. Jung, H., 2011, Earth and Planetary Science Letters, 307, 535-543. Katayama, I., et al., 2009, Nature, 461, 1114-1118. Soda, Y. and Takagi, H., 2010, Journal of Structural Geology, 32, 792-802.

Soda, Y.; Ando, J.; Mizukami, T.; Morishita, T.

2011-12-01

160

Chemical variation and zoning of olivine in lunar dunite 72415 - Near-surface accumulation  

NASA Technical Reports Server (NTRS)

Electron microprobe remeasurements have been used to reevaluate the range of olivine compositions, including CaO, in lunar dunite sample 72415 and compare that range with olivines in established plutonic rocks. Olivines from ferroan anorthosite 62237 and samples from the Stillwater intrusion were analyzed; literature data for other lunar and terrestrial plutonic samples were used for comparisons. The analyses show that the lunar dunite 72415 contains a range of olivine compositions, that the olivines are zoned, and that they have CaO abundances that are consistent with shallow hypabyssal rather than deep plutonic accumulation.

Ryder, Graham

1992-01-01

161

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

162

Synthesis and characterization of LiCo1/3Mn1/3Fe1/3PO4/C nanocomposite cathode of lithium batteries with high rate performance  

NASA Astrophysics Data System (ADS)

Olivine structured LiCo1/3Mn1/3Fe1/3PO4/C nanocomposites were prepared by a combination of spray pyrolysis at 300 C and wet ball-milling followed by heat treatment at 500 C for 4 h in a 3%H2 + N2 atmosphere. The formation of a solid solution between LiCoPO4, LiMnPO4, and LiFePO4 at this composition was confirmed by X-ray diffraction analysis. Scanning electron microscopy and transmission electron microscopy with equipped energy dispersive spectroscopy verified that the LiCo1/3Mn1/3Fe1/3PO4/C nanocomposites were agglomerates of LiCo1/3Mn1/3Fe1/3PO4 primary particles with a geometric mean diameter of 107 nm and a uniform chemical composition, and carbon was well distributed on the surface of the agglomerates. The LiCo1/3Mn1/3Fe1/3PO4/C nanocomposite cathode exhibited a high discharge capacity of 159 mAh g-1 at 0.05 C in the potential range of 2.0-5.0 V, corresponding to 94% of theoretical capacity. The capacity retention was 87% after 50 cycles at a charge-discharge rate of 1 C. Furthermore, the rate capability test showed that the high capacity still was retained even at 5 C and 20 C rate with 106 and 72 mAh g-1, respectively.

Akimoto, Sou; Taniguchi, Izumi

2013-11-01

163

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

164

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

165

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

166

Electrical conductivity of olivine single crystals at high temperature  

Microsoft Academic Search

The electrical conductivity in three single crystal specimens of olivine (fayalite mole %; 7.4, 8.4 and 12.6) is measured along the three crystallographic orientations in the temperature range of 600 to 1200K. There are two different mechanisms with different activation energy for electrical conduction; presumably the impurity (Fe) conduction is predominant above 800K and extrinsic conduction is predominant below 800K.

Yoji Kobayashi; Hiroshi Maruyama

1971-01-01

167

Space Weathering Evolution on Airless Bodies - Laboratory Simulations with Olivine  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

168

Experimental Replication of Relict "Dusty" Olivine in Type 1B Chondrules  

NASA Technical Reports Server (NTRS)

Introduction: Relict "dusty" olivine is considered to be a remnants of previous chondrule forming events based on petrographic and chemical evidence. Dynamic crystallization experiments confirm that dusty olivine can be produced by reduction of FeO-rich olivine in Unequilibrated Ordinary Chondrite (UOC) material. The results of these experiments compliment those of who also produced dusty olivine, but from synthetic starting materials. Techniques: Dynamic crystallization experiments were conducted in which UOC material was reduced in presence of graphite. Starting material was coarsely ground GR095554 or WSG95300 that contained olivine of Fo 65-98. Approximately 75 mg. of UOC material was placed in a graphite crucible and sealed in an evacuated silica tube. The tube was suspended in a gas-mixing furnace operated at 1 log unit below the IW buffer. The experiments were as brief as 1.5 hrs up to 121 hrs. Results: Dusty olivine was produced readily in experiments melted at 1400 C for I hr. and cooled between 5 and 100 C/hr or melted at 1300-1400 C for 24 hours. Fe-rich olivine (dusty olivine precursors) that have been partially reduced were common in the experiments melted at 1400 C and cooled at 1000 C/hr or melted at 1200 C for 24 hrs. Relict olivine is absent in experiments melted at 1400 for 24 hrs, melted above 1400 C, or cooled more slowly than 10 C/hr. Relict olivine in the experiments has minimum Fo value of 83 . Thus even in the shortest experiments the most Fe-rich olivine has been altered significantly. The precursor olivine disappears in a few to many hours depending on temperature. The experiments show Fe-rich olivine in all stages of transition to the new dusty form. The olivine is reduced to form dusty olivine in a matter of a few hours at temperatures less than 1400 C and in minutes at higher temperatures. The reduction appears to proceed from the rim of the crystal inward with time. The reduction appears initially rectilinear as if controlled by crystallography, but with time Fe-metal blebs are randomly distributed throughout the olivine. In a given experiment, dusty olivine can be found in varying stages of development, but in the longest experiments, the Fe-metal blebs are dominant and they appear to be migrating out of the olivine. The composition of the dusty olivine ranges from Fo 94-99. The Cr, Mn, and Ca content of the newly formed, dusty olivine is slightly less on average that the precursor olivine, but is till with the range of type 1 olivine. Chadacrysts in the low Ca pyroxene are most common in the higher temperature, more slowly cooled experiments and range in composition from Fo 90-99. Application to chondrule formation: These experiments place time-temperature limits on the preservation of Fe-rich olivine and the production of dusty olivine during chondrule forming events. The reduction process proceeds in a few hours at temperatures above 1400 C and in 10's of hours at temperature between 1200 and 1300 C. This result further confirms th at chondrules form in a few hours to days as suggested earlier. The experiments also confirm that dusty olivine can form from typical Fe-rich olivine in UOC material during the recycling of such olivine in the chondrule forming process.

Lofgren, Gary E.; Le, L.

2002-01-01

169

In Situ Investigation of Preirradiated Olivines in CM Chondrites  

NASA Astrophysics Data System (ADS)

Most CM chondrites are breccias that contain fragments of primary rock representing densely packed agglomerates of chondrules, CAIs, etc., all of which are mantled by thick layers of fine-grained mineral dust [1]. These dust mantles seem to be the result of dust sampling by the various components during their isolated existence in the solar nebula prior to the formation of the CM parent body [1]. Metzler et al. [1] concluded that these rock fragments are well-preserved remnants of the freshly accreted CM parent body(ies). There is an opposing hypothesis that favors an origin of the dust mantles in an active regolith on the CM parent body [e.g., 2]. A list of arguments against the latter view is given by Metzler et al. [1], including a hint at the absence of solar-wind-implanted gases in dust mantles and in fragments of primary rock. In analogy to brecciated ordinary chondrites and lunar breccias, the most probable residence of the solar gases in CM chondrites is their clastic matrix. The same holds for track-rich olivines that were observed in CM chondrites. The occurrence of these grains in the clastic matrix and their absence in the primary rock would give an additional argument for the idea of a dust mantle origin in the solar nebula rather than in a planetary regolith. To answer this important question, mosaics of backscattered electron images of several large polished thin sections of Murchison and Cold Bokkeveld were prepared. The thin sections (1.5-5 cm^2 each) were etched in a WN solution [3] for about 4 hr to reveal the heavy ion tracks in olivines. Results: The background GCR track density produced during meteoroid transit is on the order of 10^4 tracks/cm^2, as was previously observed by [4]. Following the definition given by Goswami and Lal [4], olivines with track densities >10^5 tracks/cm^2 were classified as preirradiated grains and were found in both meteorites in a very small quantity. In both meteorites, 39 preirradiated isolated olivine grains were found in the clastic matrix, whereas the investigated fragments of primary rock do not contain preirradiated olivines. In Murchison about 1.8% (15 out of 850 investigated grains) of the isolated olivines in the clastic matrix show high track densities in the range between 1.9 x 10^6 and >5 x 10^7, comparable to the results of Goswami and co-workers [4,5]. Both Fe-poor and Fe-rich olivines with grain sizes between 40 and 710 micrometers were found to be preirradiated. Track gradients were found in 33% of these olivines, which is very similar to the values obtained by Goswami and Lal [4] and identical to those obtained by MacDougall and Phinney [6]. About 0.4% (2 out of 530) of the investigated olivine-bearing chondrules and chondrule fragments are preirradiated. In the case of Cold Bokkeveld, 3.7% (24 out of 650) of the isolated olivines show high track densities. Thirteen of these 24 grains were found to be concentrated in a distinct inclusion (1 x 4 mm) that is characterized by its elongated appearence and clastic fabric. The track densities of its preirradiated olivines show a very narrow range, indicating a common irradiation history of these grains. The petrography of this inclusion is currently under investigation. Conclusions: Track-rich (preirradiated) olivines in CM chondrites occur exclusively in the clastic matrix of these meteorites, comparable to observations in brecciated ordinary chondrites. Fragments of primary rock in CM chondrites do not contain solar-wind-implanted gases [1] or preirradiated grains. This confirms the view that the dust mantles around various components of these rocks are the products of dust accretion in the solar nebula rather than of regolith processes on the parent body surface. References: [1] Metzler K. et al. (1992) GCA, 56, 2873. [2] Kerridge J. (1992) personal communication. [3] Krishnaswami S. et al. (1971) Science, 174, 287. [4] Goswami J. N. and Lal D.(1979) Icarus, 40, 510. [5] Goswami J. N. and MacDougall J. D. (1983) Proc. LPSC 13th, in JGR, 88, A755. [6] MacDougall J. D. and Phinney D. (1977) Proc. LS

Metzler, K.

1993-07-01

170

Evaporation of olivine - Low pressure phase relations of the olivine system and its implication for the origin of chondritic components in the solar nebula  

Microsoft Academic Search

Vapor pressures and the mode of evaporation of forsterite and fayalite and the low-pressure phase relations of the olivine solid solution system were studied using the Knudsen method. The results are applied to evaluate the genetic relationships among type IA chondrules, type II chondrules, and matrix olivine of chondrites.

Hiroko Nagahara; Bjorn O. Mysen; Ikuo Kushiro

1994-01-01

171

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

172

Electrode materials for aqueous rechargeable lithium batteries  

Microsoft Academic Search

In this review, we describe briefly the historical development of aqueous rechargeable lithium batteries, the advantages and\\u000a challenges associated with the use of aqueous electrolytes in lithium rechargeable battery with an emphasis on the electrochemical\\u000a performance of various electrode materials. The following materials have been studied as cathode materials: LiMn2O4, MnO2, LiNiO2, LiCoO2, LiMnPO4, LiFePO4, and anatase TiO2. Addition of

H. Manjunatha; G. S. Suresh; T. V. Venkatesha

2011-01-01

173

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

174

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

175

Normalized Homologous Temperature of Olivine: Implications for the Effect of Iron Content on Mantle Deforamtio  

NASA Astrophysics Data System (ADS)

The flow laws and fabric transition of olivine under different thermal-mechanical conditions are generally obtained from HP-HT experiments on San Carlos olivine (Fo90), which hampers our understanding of the effect of iron content on the mantle flow and deforamtion. Because the melting temperature is related with the strength of the bonds binding a crystalline material together, the normalized homologous temperature T/Tm(P), is defined by the ratio between the absolute temperature of olivine and its melting point Tm at certain pressure P. Using the forsterite-fayalite melting loop at room pressure, the generalized mean is adopted to predict the dependence of Tm on pressure and iron content of olivine up to 7.5 GPa. Using T/Tm(P), we can evaluate the integreted effect of temperature and pressure on the deformation mechanisms of olivine. A new olivine fabric diagram is set up as a function T/Tm(P) and water content. The result indicates that the A-type olivine fabric becomes dominant at T/Tm(P) > 0.72, while the B- and C-type olivine fabrics are favorable at T/Tm(P) < 0.7, no matter their water content. Partial melting will produce resudies with higher Fo number in olivine, and consequently, a more rigid mantle with higher Tm. The relatively smaller T/Tm(P) of olivine beneath cratons can explain the long-term stability of the continental roots. In addition, a 2D profile of olivine T/Tm(P) for the oceanic lithosphere shows good correlation between T/Tm(P) and the distribution of earthquakes. Therefore T/Tm(P) of olivine can be used as a parameter to model the rheology of the upper manlte, especailly when taking into account of the compostional change in different tectonic processes.

Wang, Q.

2012-12-01

176

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

Microsoft Academic Search

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

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

2004-01-01

177

Destabilization of olivine by 10kV electron irradiation  

NASA Astrophysics Data System (ADS)

Mineral phases in the interplanetary medium are subjected to the solar wind irradiation. Irradiation induces fractional volatilization of chemical elements in silicates; if large scale directional flow occurs, such as predicted by numerous models in the early solar system, then large scale chemical fractionnations occur. Electron irradiation experiments were performed using a 30 keV electron beam on single crystals of olivine in a scanning electron microscope (SEM) and in an electron microprobe (EMP) (Lemelle et al. 2003). Structural damage is caused to the irradiated surface of the iron-bearing olivines. The irradiated areas comprise spherules with sizes of hundreds of nanometers and micrometer-sized holes observed on Focused Ion Beam cuts. In the immediate vicinities of the irradiated areas, droplets with sizes of tens of nanometers and tracks are observed. With increasing total charge, the hundreds of nanometer-sized spherules become larger and more irregular in shape. The size and shape of the nanometer-sized droplets remain almost constant, but their surface density increases (in cm-2). Compared to the initial olivine, irradiated areas are slightly enriched in MgO, whereas the deposits are enriched in SiO_2. This destabilization of olivine results most probably from electrostatic discharges leading to the breakdown of the dielectric lattice. The possibility that such processes could be responsible for significant space weathering of interplanetary dust particles and regoliths of planetary surfaces should be taken into account. In the interplanetary medium, 10 keV-range electrons are carried by the solar wind, whereas at 1 AU from the Sun, the lifetime of cometary dust and the exposure time of lunar regolith are, at least, 10 to 100 times greater than the duration required to accumulate the damaging electronic doses applied in this study. Moreover, the comparison of the microstructures of samples irradiated in the present study with features of lunar regolith grains reveals several chemical and structural similarities. Interestingly, experiments carried out in transmission EM, with 100 keV-range electrons (Carrez et al. 2002) showed different mechanism of destabilization and chemical fractionation elemental loss from the silicate matrix. Lemelle et al. (2003) to be printed in Geochimica Cosmochimica Acta. Carrez P., Leroux H., Cordier P. and Guyot F. (2001) Philos. Mag. A 81, 2823-2840.

Lemelle, L.; Beaunier, L.; Borensztajn, S.; Fialin, M.; Guyot, F.

2003-04-01

178

Chromium valences in ureilite olivine and implications for ureilite petrogenesis  

NASA Astrophysics Data System (ADS)

Ureilites are a group of ultramafic achondrites commonly thought to be residues of partial melting on a carbon-rich asteroid. They show a large variation in FeO content (olivine Fo values ranging from ?74 to 95) that cannot be due to igneous fractionation and suggests instead variation in oxidation state. The presence of chromite in only a few of the most ferroan (Fo 75-76) samples appears to support such a model. MicroXANES analyses were used in this study to determine the valence states of Cr (previously unknown) in olivine cores of 11 main group ureilites. The goal of this work was to use a method that is independent of Fo to determine the oxidation conditions under which ureilites formed, in order to evaluate whether the ureilite FeO-variation is correlated with oxidation state, and whether it is nebular or planetary in origin. Two of the analyzed samples, LEW 88774 (Fo 74.2) and NWA 766 (Fo 76.7) contain primary chromite; two others, LAP 03587 (Fo 74.4) and CMS 04048 (Fo 76.2) contain sub-micrometer-sized exsolutions of chromite + Ca-rich pyroxene in olivine; and one, EET 96328 (Fo 85.2) contains an unusual chromite grain of uncertain origin. No chromite has been observed in the remaining six samples (Fo 77.4-92.3). Chromium in olivine in all eleven samples was found to be dominated by the divalent species, with valences ranging from 2.10 0.02 (1?) to 2.46 0.04. The non-chromite-bearing ureilites have the most reduced Cr, with a weighted mean valence of 2.12 0.01, i.e., Cr2+/Cr3+ = 7.33. All low-Fo chromite-bearing ureilites have more oxidized Cr, with valences ranging from 2.22 0.03 to 2.46 0.04. EET 96328, whose chromite grain we interpret as a late-crystallizing phase, yielded a reduced Cr valence of 2.15 0.07, similar to the non-chromite-bearing samples. Based on the measured Cr valences, magmatic (1200-1300 C) oxygen fugacities (fO2) of the non-chromite-bearing samples were estimated to be in the range IW-1.9 to IW-2.8 (assuming basaltic melt composition), consistent with fO2 values obtained by assuming olivine-silica-iron metal (OSI) equilibrium. For the primary chromite-bearing-ureilites, the corresponding fO2 were estimated (again, assuming basaltic melt composition) to be ?IW to IW+1.0, i.e., several orders of magnitude more oxidizing than the conditions estimated for the chromite-free ureilites. In terms of Fo and Cr valence properties, ureilites appear to form two groups rather than a single Cr-valence (or fO2) vs. Fo trend. The chromite-bearing ureilites show little variation in Fo (?74-76) but significant variation in Cr valence, while the non-chromite-bearing ureilites show significant variation in Fo (?77-95) and little variation in Cr valence. These groups are unrelated to petrologic type (i.e., olivine-pigeonite, olivine-orthopyroxene, or augite-bearing). The chromite-bearing ureilites also have lower contents of Cr in olivine than most non-chromite-bearing ureilites, consistent with predictions based on Cr olivine/melt partitioning in spinel saturated vs. non-spinel-saturated systems. Under the assumption that at magmatic temperatures graphite-gas equilibria controlled fO2 at all depths on the ureilite parent body, we conclude: (1) that ureilite precursor materials having the Fo and Cr valence properties now observed in ureilites are unlikely to have been preserved during planetary processing; and (2) that the Fo and Cr valence properties now observed in ureilites are consistent with having been established by high-temperature carbon redox control over a range of depths on a plausible-sized ureilite parent body. The apparent limit on ureilite Fo values around 74-76 suggests that the precursor material(s) had bulk mg# ? that of LL chondrites.

Goodrich, C. A.; Sutton, S. R.; Wirick, S.; Jercinovic, M. J.

2013-12-01

179

Olivine-rich exposures at Bellicia and Arruntia craters on (4) Vesta from Dawn FC  

NASA Astrophysics Data System (ADS)

We present an analysis of olivine-rich exposures at Bellicia and Arruntia craters using Dawn Framing Camera (FC) color data. Our results confirm the existence of olivine-rich materials at these localities as described by Ammannito et al. using Visual Infrared Spectrometer (VIR) data. Analyzing laboratory spectra of various howardite-eucrite-diogenite meteorites, high-Ca pyroxenes, olivines, and olivine-orthopyroxene mixtures, we derive three FC spectral band parameters that are indicators of olivine-rich materials. Combining the three band parameters allows us, for the first time, to reliably identify sites showing modal olivine contents >40%. The olivine-rich exposures at Bellicia and Arruntia are mapped using higher spatial resolution FC data. The exposures are located on the slopes of outer/inner crater walls, on the floor of Arruntia, in the ejecta, as well as in nearby fresh small impact craters. The spatial extent of the exposures ranges from a few hundred meters to few kilometers. The olivine-rich exposures are in accordance with both the magma ocean and the serial magmatism model (e.g., Righter and Drake; Yamaguchi et al.). However, it remains unsolved why the olivine-rich materials are mainly concentrated in the northern hemisphere (approximately 36-42N, 46-74E) and are almost absent in the Rheasilvia basin.

Thangjam, Guneshwar; Nathues, Andreas; Mengel, Kurt; Hoffmann, Martin; Schfer, Michael; Reddy, Vishnu; Cloutis, Edward A.; Christensen, Ulrich; Sierks, Holger; Corre, Lucille Le; Vincent, Jean-Baptiste; Russell, Christopher T.

2014-10-01

180

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

181

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

182

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 Schrdinger 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 Schrdinger 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 Schrdinger 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

183

Serpentinization of Olivine by Seawater: A Flow-Through Experiment  

NASA Astrophysics Data System (ADS)

The mantle exposed at slow spreading ridges is pervasively serpentinized, down to ca. 5km according to geophysical data. The onset and durability of this hydration process require efficient penetration and renewal of fluids at the mineral-fluid interface. However, the mechanisms 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 extent of serpentinization 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 laboratory experiment during which seawater was injected in a sintered San Carlos olivine sample at conditions representative of low temperature ultramafic hydrothermal systems. The percolation-reaction experiment was carried out at 19 MPa and 190C; the initial water flow was set at 0.2 mL/h then decreased down to 0.06 mL/h after 8 days. During the experiment (23 days), permeability decreased continuously. The composition of the outlet fluid varied strongly during the first 24h of the experiment, then reached equilibrium values. The high Si concentrations in outlet fluids indicated steady olivine dissolution, while their low Fe and Mg concentrations suggested precipitation of Fe- and Mg-rich mineral phases. The reacted sample acquired a reddish brown color, indicating oxidation reactions occurred. Optical observation and SEM imaging revealed the presence of a soft white material filling the pores of the reacted sample. It was identified as a poorly crystallized serpentine type material by AEM/TEM analyses. This proto-serpentine is intimately associated to <100 nm Fe-oxide patches (probably hematite) growing on the olivine surface. We interpret the precipitation of this proto-serpentine together with Fe-oxides throughout the sample as marking the early stages of serpentinization. The fluid composition not being modified by changes in fluid flow, we posit that olivine serpentinization is not controlled by elemental transport and/or by chemical kinetics, but takes place at-equilibrium; the reaction velocity is very fast and independent on the changes in the reaction surface area. Indeed, mass balance calculations indicate that more than 15 wt. % olivine was dissolved while the same mass of proto-serpentine was formed; concurrently, porosity decreased from 12% to 5 %. We infer that the structure of the newly formed proto-serpentine resulted in the clogging of fluid paths and explain the decrease of permeability during experiments. Yet the loose structure of the proto-serpentine allows maintaining a connected pore structure ensuring the perennial renewing (diffusion and/or advection) of the reactants at the reaction surfaces. 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.

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

2011-12-01

184

Nitrogen Isotopes in Olivine Separates from Volcanic Arcs, Hot Spots and Continental Mantle Xenoliths  

Microsoft Academic Search

We report the first nitrogen isotopic data of olivine separates from volcanic arcs (Cerro Negro, Nicaragua; Izalco, El Salvador; Turrialba, Costa Rica; Ichinomegata, Japan). In addition, we report nitrogen isotopic data of olivine separates from ocean islands (Hawaii, Reunion, Iceland) and continental mantle xenoliths (San Carlos, Arizona). Samples were processed by crushing and analyzed using a modified noble gas mass

T. P. Fischer; N. Takahata; Y. Sano; D. R. Hilton

2004-01-01

185

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.

186

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

187

Concentration and Mobility of Electrically-Conducting Defects in Olivine  

NASA Astrophysics Data System (ADS)

We have collected measurements of electrical conductivity and thermopower as a function of temperature and oxygen fugacity (f O2) on a sample of San Quintin dunite (95% olivine), and measurements of electrical conductivity equilibration after changes in f O2 on Mt.Porndon lherzolite (65% olivine). Both data sets have been analysed using nonlinear parameter inversion of mathematical models relating conductivity, thermopower, and diffusion kinetics to temperature, f O2, time, and defect concentration and mobility. From the dunite thermopower/conductivity data we are able to estimate the concentration and mobilities of electrically conducting defects. Our model allows electrons, small polarons (Fe+++ on Fe++ sites), and magnesium vacancies (V'' Mg) to contribute to conduction, but only polarons and V'' Mg are required by our data. Polarons dominate conduction below 1300~C; at this temperature conduction, is equal for the two defects at all f O2 tested. Thermopower measurements allow us to estimate defect concentration independently from mobility, and so we can back out polaron mobility as 12.2x 10-6 exp(-1.05~eV/kT) m2V-1s-1 and magnesium vacancy mobility as 2.72x 10-6 exp(-1.09~eV/kT) m2V-1s-1. Electrical conductivity of the lherzolite, measured as a function of time after changes in the oxygen fugacity of the surrounding CO2/CO atmosphere, is used to infer the diffusivity of the point defects associated with the oxidation reactions. An observed f O2 dependence in the time constants associated with equilibration implies two species of fixed diffusivity, each with f O2-dependent concentrations. Although the rate-limiting step may not necessarily be associated with conducting defects, when time constants are converted to mobilities, the magnitudes and activation energies agree extremely well with the model presented above for the dunite, after one free parameter (effective grain size) is fit at a plausible 1.6~mm diameter. Not only does this study represent one of the few direct measurements of polaron mobility, but the very good agreement between two independent measurement techniques (thermopower versus equilibration kinetics) and two independent samples (dunite versus lherzolite) provides some level of confidence in the results. We are currently extending these modeling techniques to study olivine defect mobility anisotropy.

Constable, S.; Roberts, J.; Duba, A.

2002-12-01

188

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

189

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

190

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

NASA Technical Reports Server (NTRS)

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.

1993-01-01

191

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

192

Mantle-crust interactions in the oceanic lithosphere: Constraints from minor and trace elements in olivine  

NASA Astrophysics Data System (ADS)

Minor and trace element compositions of olivines are used as probes into the melt-rock reaction processes occurring at the mantle-crust transition in the oceanic lithosphere. We studied mantle and lower crustal sections from the Alpine Jurassic ophiolites, where lithospheric remnants of a fossil slow-spreading ocean are exposed. Olivines from plagioclase-harzburgites and replacive dunites (Fo = 91-89 mol%) and from olivine-rich troctolites and troctolites (Fo = 88-84 mol%) were considered. Positive correlations among the concentrations of Mn, Ni, Co, Sc and V characterize the olivines from the dunites. These chemical variations are reconciled with formation by melts produced by a mixed source consisting of a depleted peridotite and a pyroxene-rich, garnet-bearing component melted under different pressure conditions. We thereby infer that the melts extracted through these dunites channels were not fully aggregated after their formation into the asthenospheric mantle. Olivines from the olivine-rich troctolites and the troctolites are distinct by those in the dunites by lower Ni and higher concentrations of Mn and incompatible trace elements (Ti, Zr, Y and HREE). Fractional crystallization cannot reproduce the chemical variations of the olivines from the olivine-rich troctolites and the troctolites. In these rock-types, the olivines commonly show heterogeneous Ti, Zr, Y and HREE compositions, which produce variable Ti/Y and Zr/Y values. We correlate these olivine characteristics with events of reactive melt migration occurred during the formation of the primitive lower oceanic crust. We propose that the migrating melts formed at the mantle-crust transition via interaction with mantle peridotites during periods of low melt supply.

Sanfilippo, Alessio; Tribuzio, Riccardo; Tiepolo, Massimo

2014-09-01

193

Origin of plagioclase-olivine inclusions in carbonaceous chondrites  

NASA Astrophysics Data System (ADS)

The origin of plagioclase-olivine inclusions (POIs) from three CV chondrites and one ungrouped chondrite was investigated by examining the chemical, mineralogical, and isotopic characteristics of a group of POIs from these chondrites. Results of these analyses demonstrate that the mixing and the partial melting processes in these inclusions were superimposed on more ancient isotopically heterogeneous material. A comparison of the essential characteristics of POIs and CAIs suggests that the major processes leading to the formation of POIs (such as condensation, dust/gas fractionation, aggregation of chemically and isotopically disparate materials, and partial melting) are common to most CAIs and chondrules. A scenario for the origin of POIs is proposed, showing that the homogeneity of the final assemblage (whether a POI, a CAI, or a chondrite) is primarily a reflection of the thermal history rather than the nature of precursor materials.

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

1991-02-01

194

Phyllosilicate and Olivine around a Fracture in Nili Fossae  

NASA Technical Reports Server (NTRS)

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this observation of part of the Nili Fossae region at the western margin of the Isidis impact basin at 3:07 (UTC) on December 12, 2006, near 21.9 degrees north latitude, 78.2 degrees east longitude. The image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 18 meters (60 feet) across. The image is about 11 kilometers (7 miles) wide at its narrowest point.

The Isidis basin resulted from a gigantic impact on the surface of Mars early in the planet's history. The image of the Isidis basin at the top left is the colored elevation data from the Mars Orbiter Laser Altimeter (MOLA) overlain on a digital image mosaic from the Viking mission. Reds represent higher elevations, and blue lower elevations. The western rim of the Isidis basin has numerous, concentric troughs (or 'fossae') which may have formed during faulting associated with the impact event. Since then, the Nili Fossae region has since been heavily eroded, and is one of the most mineralogically diverse spots on Mars.

This CRISM image targets one of region's smaller fractures. The image is shown overlain on the Viking digital image mosaic at lower left. The lower right CRISM image was constructed from three visible wavelengths (0.71, 0.60 and 0.53 microns in the red, green and blue image planes, respectively) and is close to what the human eye would see. The blue on the right of the image is an artifact from light scattering in the atmosphere. The upper right image was constructed from three infrared channels (2.38, 1.80 and 1.15 microns in the red, green and blue image planes, respectively) to highlight the mineralogy of the area. The bright green areas are rich in 'phyllosilicates,' a category of minerals including clays. The purple material along the walls of the fracture likely contains small amounts of the iron- and magnesium-rich mineral pyroxene. The yellow-brown material contains the iron- and magnesium-rich mineral olivine. Olivine and pyroxene are minerals associated with igneous activity.

Overlaying CRISM data with images from the High-Resolution Imaging Science Experiment (HiRISE) camera shows that the phyllosilicates are in small, eroded outcrops of rock. The olivine is most abundant in sand dunes on the surface. The use of these two instruments together reveals more about the history of the region: Olivine sands covered the area shown in the image after the interaction of water and rock formed the phyllosilicates and after the fracture formed.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.

2007-01-01

195

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 190C; 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

196

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

197

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

198

Serpentinization of sintered olivine during seawater percolation experiments  

NASA Astrophysics Data System (ADS)

Hydration of the mantle lithosphere exposed along detachment faults at slow-spreading ridges leads to strong modification of rock rheological, geophysical and geochemical properties, and to the emission of large amounts of H2 and CH4, and of complex carbon molecules that support primitive ecosystems. The sustainability and efficiency of this hydration process, serpentinisation, and of associated reactions, requires penetration and renewal of fluids at the mineral-fluid interface. However, precipitation of material along flow paths will affect porosity and permeability that, in turn, will have feedbacks effects on the reactions. It is thus necessary to investigate the sustainability of flow paths, and the evolution of reaction rates for a dynamic system under representative conditions. We investigate these processes by percolation experiments carried out under P, T representative conditions, using the ICARE Microlab experimental bench. We present the preliminary results of seawater percolation within samples of sintered San Carlos olivine. The experiments were carried out under a confined pressure of 190 bars and a temperature of 190 C and water flow was set at a constant specific discharge of 0.06 ml/h.. The experiments were performed at very slow flow rate to be more representative of natural systems. ICARE Microlab allows measuring continuously the permeability changes during the percolation experiment and sampling the brine at the outlet of the sample. After 20 days of experiments, poorly crystallized serpentine and iron oxide formed within the micro-cracks while permeability strongly decreases. Such rapid precipitation of serpentine results in clogging of fluid paths. The chemical composition of the outlet fluid is dominated by Si and is depleted in Mg relative to stoechiometric dissolution of olivine during the whole experiment suggesting that brucite possibly formed. SEM and AEM/TEM are used to characterize the reactive interfaces and the neoformed materials.

Luquot, Linda; Andreani, Muriel; Godard, Marguerite; Gouze, Philippe; Gibert, Benoit

2010-05-01

199

Olivine friction at the base of oceanic seismogenic zones  

USGS Publications Warehouse

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

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

2007-01-01

200

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

201

The composition of mesosiderite olivine clasts and implications for the origin of pallasites  

NASA Technical Reports Server (NTRS)

The composition of olivine clasts from the mesosiderites Emery, Mincy and Pinnaroo is investigated, and implications of the results for the origin of the pallasites, which, although chemically distinct, may be related to the diogenites, eucrites, howardites and mesosiderites, are discussed. Centimeter-sized olivines were analyzed by electron microprobe, and instrumental neutron activation analysis was performed on one olivine each from Emery and Pinnaroo and an olivine separate from the Brenham pallasite. The olivine compositions are found to range from Fa8 to Fa28, with Emery samples having values from Fa18 to Fa28, and to require essentially total melting of a source composition rich enough in FeO to produce basaltic clasts. It is argued that the mesosiderite olivines were formed in the outer few kilometers of their parent body, as were those of the pallasites, which have the same compositions as the mesosiderite olivines. A model is then developed for the origin of the pallasites as a by-product of igneous differentiation in the external heating of a chondritic parent body.

Mittlefehldt, D. W.

1980-01-01

202

Effect of Sulfur on Siderophile Element Partitioning Between Olivine and Martian Primary Melt  

NASA Technical Reports Server (NTRS)

Since olivine is a common early crystallizing phase in basaltic magmas that have produced planetary and asteroidal crusts, a number of experimental studies have investigated elemental partitioning between olivine and silicate melt [e.g., 1, 2, 3]. In particular, olivine/melt partition coefficients of Ni and Co (DNi and DCo) have been intensively studied because these elements are preferentially partitioned into olivine and thus provide a uniquely useful insight into the basalt petrogenesis [e.g., 4, 5]. However, none of these experimental studies are consistent with incompatible signatures of Co [e.g., 6, 7, 8] and Ni [7] in olivines from Martian meteorites. Chemical analyses of undegassed MORB samples suggest that S dissolved in silicate melts can reduce DNi up to 50 % compared to S-free experimental systems [9]. High S solubility (up to 4000 ppm) for primitive shergottite melts [10] implies that S might have significantly influenced the Ni and Co partitioning into shergottite olivines. This study conducts melting experiments on Martian magmatic conditions to investigate the effect of S on the partitioning of siderophile elements between olivine and Martian primary melt.

Usui, T.; Shearer, C. K.; Righter, K.; Jones, J. H.

2011-01-01

203

Detections and geologic context of local enrichments in olivine on Vesta with VIR/Dawn data  

NASA Astrophysics Data System (ADS)

magmatism characterizing the early history of the asteroid Vesta has long been investigated with the mafic and ultramafic meteorites howardite, eucrite, and diogenite (HED). The lack of geologic context for the meteorites, however, has limited its understanding. Here we use the visible to near-IR (VIR) orbital observations of Vesta's surface to detect relative enrichments in olivine and to study the associated geologic features. Because the near-IR signature of olivine on Vesta's surface is subtle relative to the widespread pyroxene absorption bands, a method was developed to distinguish olivine enrichments from admixture of pyroxenes with high Fe2+/M1, dark material, and potential Fe-bearing glass. Relative enrichment of olivine (~<50-60 vol %) is found in 2-5 km wide, morphologically fresh areas. Our global survey reveals a dozen of these areas clustering in the eastern hemisphere of Vesta. The hemispherical coincidence with a widespread, low enrichment in diogenite-like pyroxene suggests the presence of a distinct compositional terrain. On the central mound of the Rheasilvia impact basin, no olivine enrichment was found, suggesting the absence of an olivine-dominated mantle above the basin's excavation depth or, alternatively, a low amount of olivine homogeneously mixed with diogenite-like pyroxenes. Rare olivine-enriched areas in close proximity to diogenite-like pyroxene are found as part of material ejected by the Rheasilvia impact. Such cooccurrence is reminiscent of local, ultramafic lithologies within the crust. The possible formation of such lithologies on Vesta is supported by some HED meteorites dominated by olivine and orthopyroxene.

Ruesch, Ottaviano; Hiesinger, Harald; De Sanctis, Maria Cristina; Ammannito, Eleonora; Palomba, Ernesto; Longobardo, Andrea; Zambon, Francesca; Tosi, Federico; Capria, Maria Teresa; Capaccioni, Fabrizio; Frigeri, Alessandro; Fonte, Sergio; Magni, Gianfranco; Raymond, Carol A.; Russell, Christopher T.

2014-09-01

204

New insights into the formation of fayalitic olivine from Allende dark inclusions  

NASA Astrophysics Data System (ADS)

Although considerable progress has been made in unraveling the origin(s) of fayalitic olivines in dark inclusions (DIs), many questions remain still unresolved and/or controversial. We combine a chemical and petrographic study of the Allende dark inclusion 4884-2B (AMNH, New York) and ATEM studies of a fragment of the dark inclusion Allende AF (NHM, Vienna) and discuss an alternative way in which fayalitic olivines could have formed. Allende dark inclusion 4884-2B contains a few aggregates with variable proportions of transparent and feathery olivine. Two such objects (aggregates A and B) are the focus of this study as they preserve glasses that can help in deciphering the nature of the processes involved during olivine growth and subsequent olivine transformation. The petrographic and chemical characteristics of aggregates A and B indicate that the forsteritic stack olivines may be pseudomorphs of clear olivine crystals. The ATEM studies in All-AF suggest that fayalitic olivines may be the result of secondary processes (e.g., metasomatic exchange reactions) operating in the solar nebula. Transformation may have occurred through the mediation of a dry gas phase involving nonvolatile major elements, such as Mg and Fe (e.g., Dohmen et al. 1998). This mechanism could reveal olivine growth patterns (e.g., stacked platelets due to a rapid growth regime) and may have contributed to the development of their fibrous aspect while preserving the shape (i.e., volume) of the crystals. This highly selective process did completely or partially transform ferromagnesian minerals, but affected the fine-grained mesostasis only slightly.

Varela, Maria E.; Zinner, Ernst; Kurat, Gero; Chu, Hao-Tsu; Hoppe, Peter

2012-05-01

205

Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data  

NASA Astrophysics Data System (ADS)

We used spectral indexing and linear deconvolution to compare thermal infrared emission spectra of Fo91, Fo68, Fo53, Fo39, Fo18, and Fo1 olivine samples to Mars Global Surveyor Thermal Emission Spectrometer (TES) data over low-albedo regions of Mars. The Fo91, Fo68, Fo53, and Fo39 spectral end-members were confidently identified on Mars, a range of compositions wider than inferred from Martian meteorites. Small (less than hundreds of square kilometers) occurrences of the Fo91 spectral end-member are present in the rims of the Argyre and Hellas impact basins and may represent Martian mantle materials. The Fo68 spectral end-member is common throughout the highlands, chasmata, outflow channels, and Nili Fossae region. The Fo53 spectral end-member occurs in eastern Syrtis Major, the Nili Fossae region, and smooth-floored craters of the highlands. Although less abundant than Fo68 and Fo53, the distribution of the Fo39 spectral end-member suggests that some olivine on Mars is more Fe-rich than olivine in Martian meteorites. Global maps of olivine show that (1) materials containing 10-20% of olivine are common in the southern highlands of Mars, (2) olivine is most common near the topographic dichotomy boundary, and (3) olivine becomes uncommon near the poles suggesting that it may be influenced by topography and/or latitude (climate). Olivine is found in early Noachian to Amazonian terrains, some of which may be coeval with phyllosilicate and sulfate deposits detected by OMEGA implying that any early Noachian wet period of Mars' climate history may have been globally inhomogeneous or insufficient to weather the olivine that remains today.

Koeppen, William C.; Hamilton, Victoria E.

2008-05-01

206

H Diffusion in Olivine and Pyroxene from Peridotite Xenoliths and a Hawaiian Magma Speedometer  

NASA Technical Reports Server (NTRS)

Hydrogen is present as a trace element in olivine and pyroxene and its content distribution in the mantle results from melting and metasomatic processes. Here we examine how these H contents can be disturbed during decompression. Hydrogen was analyzed by FTIR in olivine and pyroxene of spinel peridotite xenoliths from Salt Lake Crater (SLC) nephelinites which are part of the rejuvenated volcanism at Oahu (Hawaii) [1,2]. H mobility in pyroxene resulting from spinel exsolution during mantle upwelling Most pyroxenes in SLC peridotites exhibit exsolutions, characterized by spinel inclusions. Pyroxene edges where no exsolution are present have less H then their core near the spinel. Given that H does not enter spinel [3], subsolidus requilibration may have concentrated H in the pyroxene adjacent to the spinel exsolution during mantle upwelling. H diffusion in olivine during xenolith transport by its host magma and host magma ascent rates Olivines have lower water contents at the edge and near fractures compared to at their core, while the concentrations of all other chemical elements appear homogeneous. This suggests that some of the initial water has diffused out of the olivine. Water loss from the olivine is thought to occur during host-magma ascent and xenolith transport to the surface [4-6]. Diffusion modeling matches best the data when the initial water content used is that measured at the core of the olivines, implying that mantle water contents are preserved at the core of the olivines. The 3225 cm(sup -1) OH band at times varies independantly of other OH bands, suggesting uneven H distribution in olivine defects likely acquired during mantle metasomatism just prior to eruption and unequilibrated. Diffusion times (1-48 hrs) combined with depths of peridotite equilibration or of magma start of degassing allow to calculate ascent rates for the host nephelinite of 0.1 to 27 m/s.

Peslier, A. H.; Bizimis, M.

2014-01-01

207

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

208

Fe-Mg-Mn relations of ureilite olivines and pyroxenes and the genesis of ureilites  

NASA Technical Reports Server (NTRS)

Microprobe analyses of ureilite and pigeonite cores are studied. The Fe/Mn-Fe/Mg relationship in the olivine core is examined. It is observed that magnetic processs such as fractional crystallization and partial melting, and FeO reduction contribute to the olivine core composition. The study of the Mg/Mn and Fe/Mn distributions reveals that these two distributions are not in equilibrium in the olivine and pigeonite cores. The effect of a reducing agent, carbon, on the ureilite genesis is investigated. It is concluded that fractional crystallization and FeO reduction are the major processes of ureilite genesis.

Mittlefehldt, D. W.

1986-01-01

209

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

210

Water dissolved in olivine: A single-crystal infrared study  

NASA Astrophysics Data System (ADS)

Polarized infrared spectra of the hydrogen impurities in an olivine single crystal, approximately (Mg0.9Fe0.1)2SiO4, from the Zargabad Island, Red Sea, are reported in the range 4200-3000 cm-1. In the O-H stretching frequency region, two groups of IR absorption bands occur which show the same pleochroism and the same temperature-induced shift between room temperature and 80 K. Each of these IR groups is composed of three equidistant bands at 3614, 3591, 3567 m-1 and at 3576, 3530, 3485 cm-1 (80 K values). These distinct multiplets are assigned to the OH--compensated octahedral and tetrahedral vacancy defects [OHV?oct]' and [OHV'tetr]*, respectively. It is suggested that the reduced effective charge of the tetrahedral, i.e., Si-type, vacancy is due to Si entering a nearby nonideal site for partial charge compensation. The multiplet splitting, 23 and 45 cm-1, is due to the isomorphous substitution of Mg and Fe on the adjacent M1 and M2 positions to which the proton-bearing oxygen is bound. This leads to the combinations (Mg Mg Si), (Mg Fe Si), (Fe Fe Si) and (Mg Mg Mg), (Mg Mg Fe), (Mg Fe Fe) at the octahedral M2 and at the tetrahedral vacancy sites, respectively. An IR signal which would correspond to the fully OH--compensated divalent cation vacancy defect [OHV?octHO]* appears to be absent. Instead a weak absorption band is observed in the range of the H-H stretching frequency of molecular H2. By analogy to molecular H2 in MgO and CaO single crystals and in fused silica it is concluded that OH- pairs, associated with this type of defects, undergo a charge transfer conversion into (H2 + O22-). The H2 are loosely bound to the peroxy entities which probably form peroxy bridges between SiO4 tetrahedra, e.g., Si-O-O-Si. Outgassing of H2 would leave excess oxygen behind, shifting the stoichiometry of the olivine in a direction which has never been discussed before.

Freund, Friedemann; Oberheuser, Gert

1986-01-01

211

Charge Localization and Transport in Lithiated Olivine Phosphate Materials  

SciTech Connect

We report density functional theory (DFT) calculations for olivine-type LiTMPO4 and TMPO4 (TM=Mn, Fe, Co, Ni) structures, using GGA+U and the B3LYP hybrid density functional that includes nonlocal Fock exchange. TM is typically characterized in terms of the formal oxide states of 2+ or 3+, corresponding to TM with localized charge in LiTMPO4 and TMPO4 structures, respectively, in which electron transport would take place by thermally activated hopping of electrons strongly localized on the transition metal (small polarons). In this work, we assess the validity of the concept of formal TM oxidation states in these materials, and conclude that the valence depends in large part on the strength of d-p hybridization. Stable small polaron formation, i.e., mixed 2+ and 3+ valence states, appears to require that the ratio of differences in the metal and oxygen ionic charges (dQTM/dQO) of the two end member phases is larger than 2, corresponding to the mixed-valence TM system. If the ratio of dQTM/dQO is smaller than 2, excess electrons prefer delocalization and the system behaves more single-valence like with charge transport more akin to metallic conduction. The critical ratio emerging from our analysis may turn out to be relevant to other transition metal systems as well, as a criterion to discriminate single-valence or mixed-valence characteristics and hence the predominant conduction mechanism.

Yu, Jianguo; Rosso, Kevin M.; Liu, Jun

2011-11-10

212

Shallow crystallization of Kilauean olivines: Magma density and picritic eruptions  

SciTech Connect

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

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

1992-01-01

213

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

214

Relation of the spectroscopic reflectance of olivine to mineral chemistry and some remote sensing implications  

NASA Astrophysics Data System (ADS)

High-resolution visible and near-IR diffuse spectral reflectance are used to systematically investigate apparent wavelength shifts as a function of mineral chemistry in the Fe/Mg olivine series from Fo(11) to Fo(91). The study also shows that trace amounts of nickel can be spectrally detected in the olivine structure. Significant compositional information can only be extracted at relatively high resolution, because the overall spectral characteristics of the olivines change only subtly as a function of the Fe/Mg ratio. This laboratory study is expected to aid in the interpretation of remotely sensed data from both terrestrial and extraterrestrial bodies. Terrestrial applications may include the recognition of ultramafic, ultrabasic, and basaltic terrains which in themselves may have mineral potential. Among extraterrestrial applications, the asteroids are obvious candidates for further examination. Some permutations of Fe-Mg-Ni relations in olivines are discussed as they apply to the interpretation of asteroid surfaces and other extraterrestrial bodies.

King, Trude V. V.; Ridley, W. Ian

1987-10-01

215

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

216

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

217

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

218

Raman spectroscopy of olivine in dunite experimentally shocked to pressures between 5 and 59 GPa  

NASA Astrophysics Data System (ADS)

Previous Raman investigations on experimentally shocked ingle-crystal olivine indicated that the olivine Raman bands seemingly shift to a higher wave number with increasing shock pressure. If this effect could be confirmed, Raman analysis of natural shock-metamorphosed minerals could potentially provide an important shock barometric tool. We carried out a Raman spectroscopic study on olivine in a series of natural dunite samples experimentally shocked to pressures between 5 and 59 GPa. In addition, we analyzed olivine grains in a sample of the Cold Bokkeveld C1 meteorite. We studied samples of several dunites with olivine of 90.64-92.00 mole% Fo to determine Raman effects in the region from 200 to 900 cm-1. Several olivine grains per sample/shock pressure stage were analyzed. Raman analysis, however, showed little or no shift with increasing shock pressure. The shifts to higher or lower frequencies observed were not specific for a given pressure stage, with some grains within a sample showing more shift than others. This finding is unrelated to the crystallographic orientation of analyzed grains and cannot be related systematically to the different degrees of optically determined shock metamorphism of the analyzed grains. We identified an increase in full width at half maximum (FWHM) for the 824 cm-1 band with increased shock pressure in the shocked heim samples above 45 GPa and, to a lesser extent, for the 856 cm-1 band. Evaluation of band broadening of olivine in the Cold Bokkeveld meteorite showed FWHM values that were much greater (9-20 cm-1) than those of olivine in the shocked dunite samples (7-12 cm-1). We concluded that these differences in FWHM are due to differences in chemical composition between the meteoritic and the experimentally shocked olivine. Therefore, using Raman spectroscopy to detect small shifts in wave numbers to higher frequencies with increased shock pressure does not yield consistent effects for polycrystalline dunite. An extra band at 650 cm-1 was identified in the Raman spectra of the unshocked Mooihoek dunite and the heim dunite samples shocked to 5, 29.3, and 59 GPa, as well as another at 696 cm-1 in all the spectra of the 59 GPa heim sample. The cause of these extra bands is not known. Comparison of these results with Raman spectra of olivine from the Cold Bokkeveld C1 meteorite did not allow us to determine shock pressures for the meteoritic olivine.

Farrell-Turner, S.; Reimold, W. U.; Nieuwoudt, M.; Erasmus, R. M.

2005-10-01

219

Electrical Conductivity of Olivine at High Pressure and Under Controlled Oxygen Fugacity  

Microsoft Academic Search

It is now generally accepted that the major phase in the earth's upper mantle is olivine with an approximate composi- tion Mgx.sFe0..SiO4 (Fujisawa, 1968). Published values of elec- trical conductivity a of olivine of this composition (either single crystal or polycrystalline) at high temperatures show very poor agreement (Duba and Lilley, 1972). In many in- stances the difference can be

A. Duba; H. C. Heard; R. N. Schock

1974-01-01

220

Effect of Water on the Rheological Behavior of Fe-rich Olivine  

Microsoft Academic Search

The influence of water content on the rheological properties of Fe-rich olivine was investigated in order to better understand the influence of hydrogen on the creep behavior of mantle rocks. Triaxial compressive creep experiments were performed on fine-grained samples of Fo50 and Fo50 + water. Samples were fabricated from a mixture of powders of San Carlos olivine, Fo90, and synthetic

Y. Zhao; M. E. Zimmerman; D. L. Kohlstedt

2003-01-01

221

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

222

Olivine-rich rims surrounding chondrules in the Mokoia CV3 carbonaceous chondrite: Further evidence for parent-body processes  

NASA Astrophysics Data System (ADS)

Fine-grained rims surrounding chondrules and inclusions in the Mokoia CV3 carbonaceous chondrite can be divided into phyllosilicate-rich and olivine-rich types. We present a petrographic and electron microscopic study of the olivine-rich rims and their host objects (referred to as chondrules/olivine-rich rims). The olivine-rich rims consist mainly of Fe-rich olivine and very minor phyllosilicate (saponite). Their host chondrules contain minor saponite and phlogopite, which resulted from aqueous alteration of anhydrous silicates. Mineralogical and compositional characteristics of the chondrules/olivine-rich rims suggest that they experienced mild thermal metamorphic effects. The rims commonly contain veins of coarse-grained Fe-rich olivine, magnetite, and Fe-(Ni) sulfides. The chondrules show abundant evidence of alteration along their peripheries, and the alteration textures suggest a mechanism for rim formation by replacement of the chondrules. Initially, enstatite and opaque nodules preferentially reacted to form coarse, platy, Fe-rich olivine crystals, which were subsequently divided into finer grains. Forsterite was also replaced by Fe-rich olivine. As the alteration advanced, these Fe-rich olivines were disaggregated, mixed with simultaneously produced saponite, and formed rims. In contrast, the surrounding matrix shows no evidence of such alteration and metamorphism. These observations indicate that the chondrules/olivine-rich rims did not experience these secondary processes in their present setting. The results suggest that the chondrules/olivine-rich rims experienced extensive replacement reactions in an environment in which aqueous fluids existed but only in minor amounts. They have probably also undergone simultaneous and/or subsequent mild thermal metamorphism. We suggest that the chondrules/olivine-rich rims are actually clasts transported from a relatively dry region in the parent body that was different from the region where Mokoia was finally lithified.

Tomeoka, Kazushige; Ohnishi, Ichiro

2014-07-01

223

High-Temperature Microindentation Tests on Olivine and Clinopyroxene  

NASA Astrophysics Data System (ADS)

The perspectives of microindentation techniques for the investigation of the mechanical behaviour of minerals at high temperatures are explored. The technique offers the following advantages: (1) natural specimens with small grain size can be used, (2) preparation is simple, (3) a reasonable number of experiments can be performed within a short period of time. The strength of single crystals as a function of orientation and the activated glide systems are studied using scanning electron microscopy (SEM) combined with electron backscatter diffraction (EBSD) facilities. Furthermore, the effects of compositional variations on the flow strength of solid solutions are explored. The indentation hardness tests are performed on selected grains within natural polycrystalline aggregates. The surface of the specimen is polished mechanically and chemically. The orientation of the crystals is determined using EBSD. The indentation tests are performed with a diamond pyramid (Vickers indenter) at temperatures of 25 C to 900 C. Loading is done with a constant displacement rate up to a force of 0.5 N, followed by a creep period of 10 s at constant load. SEM is used to measure the size of the indents and to examine their morphology in detail. The microhardness obtained for olivine depends on crystal and indenter orientation and decreases slightly with temperature. Slip steps are observed on the surface around the indents. Their orientation with respect to the crystal orientation indicates that the predominant glide system activated in the indentation process is \\{110\\}[001]. The Schmid factors for this glide system correlate with the observed orientation dependence of the hardness. Indentation hardness of clinopyroxene solid solutions depends on composition with jadeite being stronger than diopside. This is inverse to what is expected for dislocation creep. The high yield stresses inferred from the hardness data and the weak dependence of hardness on temperature are consistent with plasticity being the deformation regime explored in indentation hardness tests.

Dorner, D.; Schellewald, M.; Stckhert, B.

2001-12-01

224

Molecular Dynamics Simulations of Olivine-Silicate Melt Interfaces  

NASA Astrophysics Data System (ADS)

Partially molten rocks are important constituents of the Earth's crust and mantle. Their properties depend not only on the chemistry and mineralogy but also on the fraction and distribution of melt or fluid. Partially molten rocks strongly influence the chemical transport in the Earth and geodynamics. We model a partially molten rock on the atomic scale by confining a silicate melt of MgSiO3 composition between Mg2SiO4 olivine crystals. Molecular dynamics simulation is used to study the atomic scale structure and respective transport properties at the interfaces. To represent the atomic interaction, we use an advanced ionic model that accounts for anion polarization and shape deformations (Jahn and Madden, 2007). We construct interfaces between silicate melt layers of different thickness (1.85nm & 3.7nm) and mineral surfaces with different crystal orientations ((010), (001) and (100)). From the particle trajectories we derive various properties like charge density, cation coordination, connectivity of SiO4 tetrahedra and self diffusion coefficients. By adding some (Al, Ca) impurities to the system, the response to different chemical compositions is studied. To obtain a stable solid-melt interface, a temperature of 2000K is chosen. Simulations are performed at ambient pressure. We examine how the chemical composition and the self-diffusion coefficients vary across the interface. Our results indicate that with increase of surface energy, the self-diffusion coefficients of the various species decrease. This may be related to the stronger interaction of the crystal surface with the melt when the surface energy is high, which leads to more structured melt close to the interface. In conclusion, our simulations provide insight into the relation between atomic scale structure and transport properties in partially molten rocks. References S. Jahn and P.A. Madden (2007) Modeling Earth materials from crustal to lower mantle conditions: A transferable set of interaction potentials for the CMAS system. Phys. Earth Planet. Int. 162, 129-139.

Gurmani, Samia; Jahn, Sandro; Brasse, Heinrich; Schilling, Frank R.

2010-05-01

225

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

226

Experimental Partitioning of Cr(3+) and Sc(3+) into Olivine: Mechanisms and Implications  

NASA Technical Reports Server (NTRS)

Olivine (Mg, Fe)Si2O4 does not, by stoichiometry, accept cations such as Sc(3+) or Cr(3+). However, the partition coefficients of Sc and Cr between olivine and liquid are significant 0.2-1.0. We have measured Cr(3+) partition coefficients of near unity and have grown olivines with nearly 3 wt.% Sc2O3. Therefore, there must be a simple means of charge balancing 3+ ions in a crystal structure that was obviously not designed to receive other than 2+ ions on the olivine M sites. The simplest explanation is that two 3+ ions enter the olivine structure by displacing three 2+ ions and creating an M site vacancy. Even this explanation has difficulties. For minor elements in our experiments (1 wt.%) the odds of a minor element 3+ ion finding a second 3+ for charge balance are of the order of 100:1 against. Because of the reducing conditions of our experiments, Fe(3+) will not suffice; and Al(3+) is not in sufficient quantity in olivine for charge balance. Therefore, Cr or Sc must, in effect, charge balance itself. For true trace elements, the problem is compounded many times. For an ion at the 10 ppm level the chances of finding a second (for example) Sc ion is approx.10(exp 5):1 against. Of course, any other 3+ ion would suffice but comparisons between percent level doping experiments and trace level partitioning indicate that Henry s law is obeyed. This implies that the same substitution mechanism occurs at both the percent and tens of ppm levels. There are two simple solutions to this problem: (i) The electrical conductivity of olivine is such that charge balance need not be local. This requires substantial domains within the olivine crystal in electrical contact by migration of vacancies or electronic defects. (ii) The 3+ cation brings along its own charge-balancing ion because it existed as a dimer in the silicate liquid. Olivine is not a true insulator but is actually a p-type semiconductor. Even so, electrical communication by this means is unlikely over the tens or hundreds of unit cells that would be required for charge balance to be local. Therefore, we cautiously favor the idea that melt speciation is the means by which 3+ ions enter the olivine structure. Possibly this model might be tested by in situ XAFS measurements or by molecular dynamical calculations.

Jones, John; Mackwell, S. J.

2006-01-01

227

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

NASA Astrophysics Data System (ADS)

Water has been proved playing an important role in effecting physical properties of minerals. Previous studies have demonstrated that incorporating small amounts of water significantly reduce bulk moduli of wadsleyite and ringwoodite by 10% and 16% respectively (Yusa and Inoue, 1997; Inoue et al. 1998). Although olivine takes much smaller amount of water (10 times less) than wadsleyite and ringwoodite, rheology experiments have revealed that olivine is considerably weakened by water (Chen et al. 1998). Here we report a comparative study of effect of water on compressibility of San Carlos olivine, indicating a 5% reduction in bulk modulus. Hydrous olivine sample is prepared by annealing San Carlos olivine in presence of water at 12.5GPa and 1200C for an hour. Water content in the hydrous sample is about 0.1wt%, estimated according to water solubility in olivine at such P-T condition (Kohlstedt, Keppler and Rubie, 1996). Two small pieces of pressed hydrous and anhydrous sample are loaded in the same diamond anvil chamber; Ruby chips are placed between the two samples as a pressure marker. The specimens are compressed in solution of methanol and ethanol (4:1) pressure medium up to 11 GPa. Energy dispersive x-ray diffraction is conducted at the X17C beamline of the National Synchrotron Light Source. The diffraction data are processed using full spectrum Le Bail refinement method to derive accurate volumes of olivine. Fitting the experimental data to 3rd-order Birch-Murnaghan equation of state with fixed K0' = 4.29 (Abramson et al. 1997) yield bulk moduli of 130 4 GPa and 123 4 GPa for anhydrous and hydrous samples respectively. This result demonstrates that 0.1wt% of water reduces the bulk modulus of San Carlos olivine by 5%. As the hydrous sample is at water saturated condition, the 5% reduction represents the upper limit of water effect on the bulk modulus of olivine. Taking the effect of water on bulk moduli of both olivine and wadsleyite into account, if water presents at the boundary between upper mantle and transition zone, the amplitude of 410 km seismic discontinuity will be reduced, and therefore the mineral physics composition model will better agree with seismic observations - another evidence of presence of water in the mantle.

Chen, J.; Liu, H.; Yu, T.; Hu, J.

2005-12-01

228

Effect of water and stress on the lattice-preferred orientation of olivine  

NASA Astrophysics Data System (ADS)

The influence of water and stress on the lattice-preferred orientation (LPO) of olivine aggregates was investigated through large strain, shear deformation experiments at high pressures and temperatures ( P = 0.5-2.1 GPa, T = 1470-1570 K) under both water-poor and water-rich conditions. The specimens are hot-pressed synthetic olivine aggregates or single crystals of olivine. Water was supplied to the sample by decomposition of a mixture of talc and brucite. Deformation experiments were conducted up to ? (shear strain) 6 using the Griggs apparatus where water fugacity was up to 13 GPa at the pressure of 2 GPa. The water content in olivine saturated with water increases with increasing pressure and the solubility of water in olivine at P = 0.5-2 GPa was 400-1200 ppm H/Si. Several new types of LPO in olivine are found depending on water content and stress. Samples deformed in water-poor conditions show a conventional LPO of olivine where the olivine [100] axis is subparallel to the shear direction, the (010) plane subparallel to the shear plane (type-A). However, we identified three new types (type-B, C, and E) of LPO of olivine depending on the water content and stress. The type-B LPO of olivine which was found at relatively high stress and/or under moderate to high water content conditions is characterized by the olivine [001] axis subparallel to the shear direction, the (010) plane subparallel to the shear plane. The type-C LPO which was found at low stress and under water-rich conditions is characterized by the olivine [001] axis subparallel to the shear direction, the (100) plane subparallel to the shear plane. The type-E LPO which was found under low stress and moderate water content is characterized by the olivine [100] axis subparallel to the shear direction, the (001) plane subparallel to the shear plane. Observations by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) show that the dislocations in water-poor samples (type-A) are curved and both b = [100] and b = [001] dislocations have a similar population. Numerous subgrains are seen in water-poor samples in backscattered electron images. In contrast, water-rich samples (both type-B and type-C) contain mostly b = [001] dislocations and dislocations are straight and sub-grain boundaries are rare compared to those in water-poor samples. These observations suggest that (1) dominant slip systems in olivine change with water fugacity (and stress) and (2) grain boundary migration is enhanced in the presence of water. Seismic anisotropy corresponding to the fabrics under water-rich condition is significantly different from that under water-poor condition. Consequently, the relationship between seismic anisotropy and flow geometry in water-rich regions is expected to be different from that in water-poor regions in which type-A fabric dominates (i.e., the lithosphere). A few cases are discussed including anisotropy in the subduction zone and in the deep upper mantle.

Jung, H.; Katayama, I.; Jiang, Z.; Hiraga, T.; Karato, S.

2006-07-01

229

Influence of FeO and H on the electrical conductivity of olivine  

NASA Astrophysics Data System (ADS)

The influence of Fe (iron) and H (hydrogen) on the electrical conductivity of olivine was investigated. Synthetic olivine aggregates with the XFe = Fe/(Fe + Mg) (molar ratio) = 21-64% with the water content of 84-620 ppm wt (Paterson calibration) were prepared and their electrical conductivity was measured at P = 4 GPa and T = 873-1473 K. The impedance spectroscopy was used to calculate the DC electrical conductivity. We found that electrical conductivity of samples increases with increasing FeO content in both anhydrous and hydrous olivine. However, the way in which FeO enhances electrical conductivity is different between anhydrous and hydrous olivine. In anhydrous sample, the activation energy is reduced with FeO content and hence the effect of FeO content is large at low temperatures, but its effect is small at mantle temperatures. In contrast, FeO content does not affect the activation energy in hydrous olivine, and consequently, the magnitude of FeO effect is nearly independent of temperature. For both anhydrous and hydrous olivine, the influence of FeO is only modest at high temperatures (increase in conductivity by a factor of ?2 for the increase in FeO by 20% (e.g., from 10 to 30%)). In contrast, the FeO content has relatively large effects at low temperatures for anhydrous olivine. However, the role of hydrogen is large at low temperatures and hydrogen mechanism dominates under most cases. Therefore the influence of FeO on electrical conductivity is small at all temperatures for a plausible range of water content. We conclude that the water (hydrogen) content in a terrestrial planet can be inferred from observed conductivity without substantial influence of FeO if the temperature is constrained. The present results provide a basis for the interpretation of electrical conductivity model of other planets with different FeO contents.

Dai, Lidong; Karato, Shun-ichiro

2014-12-01

230

The legacy of crystal-plastic deformation in olivine: high-diffusivity pathways during serpentinization  

NASA Astrophysics Data System (ADS)

Crystal-plastic olivine deformation to produce subgrain boundaries composed of edge dislocations is an inevitable consequence of asthenospheric mantle flow. Although crystal-plastic deformation and serpentinization are spatio-temporally decoupled, we identified compositional readjustments expressed on the micrometric level as a striped Fe-enriched ( bar{X}_{text{Fe}} = 0.24 0.02 (zones); 0.12 0.02 (bulk)) or Fe-depleted ( bar{X}_{text{Fe}} = 0.10 0.01 (zones); 0.13 0.01 (bulk)) zoning in partly serpentinized olivine grains from two upper mantle sections in Norway. Focused ion beam sample preparation combined with transmission electron microscopy (TEM) and aberration-corrected scanning TEM, enabling atomic-level resolved electron energy-loss spectroscopic line profiling, reveals that every zone is immediately associated with a subgrain boundary. We infer that the zonings are a result of the environmental Fe2+Mg-1 exchange potential during antigorite serpentinization of olivine and the drive toward element exchange equilibrium. This is facilitated by enhanced solid-state diffusion along subgrain boundaries in a system, which otherwise re-equilibrates via dissolution-reprecipitation. Fe enrichment or depletion is controlled by the silica activity imposed on the system by the local olivine/orthopyroxene mass ratio, temperature and the effect of magnetite stability. The Fe-Mg exchange coefficients K_{text{D}}^{{{text{Atg}}/{text{Ol}}}} between both types of zoning and antigorite display coalescence toward exchange equilibrium. With both types of zoning, Mn is enriched and Ni depleted compared with the unaffected bulk composition. Nanometer-sized, heterogeneously distributed antigorite precipitates along olivine subgrain boundaries suggest that water was able to ingress along them. Crystallographic orientation relationships gained via electron backscatter diffraction between olivine grain domains and different serpentine vein generations support the hypothesis that serpentinization was initiated along olivine subgrain boundaries.

Plmper, Oliver; King, Helen E.; Vollmer, Christian; Ramasse, Quentin; Jung, Haemyeong; Austrheim, Hkon

2012-04-01

231

Effect of fO2 on the incorporation and diffusivity of Li in olivine  

NASA Astrophysics Data System (ADS)

Over the last decade the geochemical behaviour of Li has become of special interest since it was speculated that Li stable isotopes could be a promising tracer for subduction zone processes. However, there have been many studies of natural samples but our experimental and theoretical basis for interpreting these data is still lacking. Two diffusion mechanisms were identified for Li in olivine [1]. Their contribution to the net flux of Li in olivine depends on the vacancy concentration on the metal sites, which is sensitive to the fO2. Therefore we have studied the effect of fO2 on Li solubility and diffusion in olivine. Experimental approach: thin plates of crushed, natural olivine single crystals were embedded into two different kind of powders, ground plagioclase with about 2.5 ppm Li or a pre-annealed powder mixture of San Carlos olivine and isotopically enriched Li. All runs were performed in a gas-mixing furnace with fO2 controlled by flowing CO/CO2 mixture. In each run we simultaneously annealed about 100 micrometer-sized samples of Pakistan olivine and San Carlos olivine. In addition we have added to each run a mm sized crystallographically oriented parallelepiped of San Carlos olivine. For each powder reservoir we have performed a set of three anneals at 1200 C and different fO2. Cross sections of the run products were polished and analyzed with LA-ICP-MS. Results: In all cases the Li isotopes and concentrations were homogeneous in the 100 micrometer sized grains with one exception, the experiment at 1.e-10 bar with the highly enriched Li reservoir. The final Li concentration was slightly lower in the Pakistan than San Carlos olivine and was much lower in general if buffered by the plagioclase powder. Most importantly, the Li concentration increased systematically with increasing oxygen fugacity, indicating that the incorporation of Li in olivine is fO2 dependent. The mm-sized, oriented crystal was in most cases zoned and the extent of zoning depends on the diffusion direction. In addition the profiles became systematically longer with decreasing fugacity and at the most reducing conditions the crystal was almost homogenous. However, the isotopes were in all cases completely homogenized and equilibrated with the isotopically enriched reservoir. Thermodynamic model: We extended the quantitative point defect model for olivine [2] and reproduced the effect of fO2 on the solubility of Li when we assume it is mainly on the metal site and charge balanced by the formation of Fe3+ on the metal site. Conclusions: Our results strongly indicate that incorporation of Li is dependent on the fO2, less dependent on the trace element content. Diffusion of Li in olivine is anisotropic and dependent on fO2. Our quantitative point defect model for olivine underpins the experimental results. This will allow us to develop a multi-component diffusion model considering relevant point defects, e.g. Fe3+ and metal vacancies. Such a model will hopefully help us to simulate diffusion of Li at various natural circumstances including fO2 as a critical parameter. References: [1] Dohmen et al. (2010) Geochim Cosmochim Acta 74, 274-292; [2] Dohmen and Chakraborty (2007), Phys Chem Minerals 34, 597- 598.

Dohmen, R.; Coogan, L. A.

2012-12-01

232

Olivine + halides: a recipe for iron mobilization in volcanic ash?  

NASA Astrophysics Data System (ADS)

During the last decade, scientific evidences strongly suggest that volcanic ash iron has fertilization impact upon the surface ocean. Still, it is not well constrained how the insoluble iron in ash (i.e., as a component in minerals and also glass) could be mobilized during volcanic eruptions and atmospheric transport. Here we investigate the volcanic plume controls on ash iron solubility. We develope a conceptual box model to simulate the high, mid and low temperature chemical, physical and thermodynamic processes in eruption plumes to better constrain the iron mobilization in volcanic ash. We take into account the interaction of different species in a solid-liquid-gas system representing various volcanic settings (convergent plate, divergent plate and hot spot). Results show that the hot core of a volcanic plume (T>600C) does not produce soluble iron directly but significantly controls the Fe mineralogy and oxidation state at the ash surface. The final iron mineralogy at the ash surface (i.e. the ash's oxidation front with 1-100 nm thickness) is likely to be independent of temperature and oxygen fugacity and is closely correlated to the ratio of H2 and H2S content of the magmatic gas to the amount of entrained oxygen. As the plume continues rising and cooling, sulfuric acid condenses at about 150C followed by water condensation at about 50C which also dissociates sulfuric acid and produces H+ ions in the liquid phase. The aqueous phase scavenges the surrounding gas species (e.g. SO2, HCl, HF) and concurrently dissolves the ash surface constituents. Since HCl is about 4 orders of magnitudes more soluble than SO2, its dissolution mainly controls the pH of the liquid. Hence, high HCl concentrations in the gas phase results in lower pH in the aqueous phase (pH<0.5) and consequently an increase in the ash dissolution rate. Moreover reduced iron carrying minerals (e.g. fayalite) show a much higher dissolution rate in comparison with oxidized species (e.g. hematite). Thus, the presence of the reduced iron species in the mineral assemblage seems to be more favorable for the soluble iron production. We conclude that bio-available iron production is weakly correlated with the tectonic setting and is instead controlled by the halide content of the eruption plume and the oxidation state of the iron at the ash mineral assemblage (e.g. presence of olivine). This hypothesis could satisfactorily explain the extraordinary iron release from the ash of Hekla eruption in 2000 and also the fertilization impact caused by the ash erupted from Kasatochi in 2008.

Hoshyaripour, G.; Hort, M. K.; Langmann, B.

2013-12-01

233

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

NASA Astrophysics Data System (ADS)

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

Khler, P.; Abrams, J.; Vlker, C.; Wolf-Gladrow, D. A.; Hartmann, J.

2012-04-01

234

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 m olivine absorption band, and reddening. The attenuation of the 1 m band significantly shrinks the band FWHM and shifts the much reduced band center to shorter wavelengths around 0.95 m. 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 m 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

235

NiO and Fe\\/Mn in Fo-rich olivines from OIB, MORB, and mantle peridotites  

Microsoft Academic Search

Olivines from mantle peridotites have a narrow range of NiO (0.360.03 [1sigma] wt%), but NiO of olivines in basalts suggest NiO in mantle olivines is actually more variable: e.g., Hawaiian phenocrysts (Fo>90) have NiO >0.55%, and olivines from continental flood basalts can have >0.5% NiO. At the other end of the spectrum, some basaltic suites (e.g., Iceland, MORBs) have Fo>90

H. Li; M. Baker; A. E. Hofmann; D. Clague; E. Stolper

2006-01-01

236

Mineralogical Comparison of Olivine Xenocrysts in Angrites LEW 87051 and Asuka 881371  

NASA Astrophysics Data System (ADS)

Antarctic angrites LEW87051 (L7) and Asuka-881371 (A8) have distinctive textural and mineralogical similarities. L7 has porphyritic zoned olivines up to 0.5 mm in size distributed in a fine-grained groundmass [e.g. 1]. Some L7 olivines have Mg-rich cores which are out of equilibrium with the melt and are considered to be xenocrysts [e.g. 2]. A8 has an ophitic groundmass that contains olivine xenocrysts larger than 2 mm across [e.g. 3]. These reach up to Fo(sub)89, and are rich in Cr and poor in Ca, like L7 olivine cores. Despite these similarities, two major differences exist between L7 and A8. One is the range of compositions of the olivine xenocrysts. Although olivine cores of L7 are almost homogeneous in composition from one grain to another, A8 shows significant variations. Each large xenocryst in A8 is nearly homogeneous (except for an Fe-rich rim). However, core compositions of A8 olivine xenocrysts vary: Fo(sub)70-89, Cr2O3 0.3-0.7 wt%, CaO 0.0-0.6 wt%, Al2O3 0.05-0.25 wt%, while olivine cores of L7 are nearly uniform: Fo(sub)88-90, Cr2O3 0.2 wt%, CaO 0.3 wt%, Al2O3 0.1 wt% [3,4]. The other difference is grain size. L7 olivines are at most 0.5 mm across, while A8 olivines are generally larger than 2 mm. Thus L7 and A8 show significant differences. One possible interpretation is that both samples contained xenocrysts that were resorbed to differing degrees in a heating event. We previously suggested that L7 xenocrysts less Mg-rich than Fo(sub)85 somehow melted and only Mg-rich olivine survived [5]. The core of L7 olivine is more clearly zoned than A8 xenocrysts, possibly due to a higher degree of atomic diffusion. In the case of A8, xenocrysts with Mg as low as Fo(sub)70 remain, and the xenocrysts are quite large. This is consistent with the hypothesis that A8 experienced less resorption of xenocrysts than L7. It is possible that L7 olivine core and A8 olivine xenocrysts originate from the same source. Their FeO/MnO ratio (wt%) is almost same (ca. 80-90). However, the A8 xenocrysts show a wider compositional range. We previously calculated the cooling rate of L7 olivine and estimated that burial depth was less than 2 m [5]. Compositions of groundmass fassaite in L7 and A8 are nearly consistent [e.g. 6]. This suggests formation from similar melts. Our model of L7 and A8 formation is as follows. Olivine crystals of various compositions were incorporated in a melt and somehow reheated. In the case of L7, all but the most Mg-rich olivines were totally melted, while even Fo(sub)70 olivines did not melt for A8. After the melting stage, the outer part of the L7 porphyritic olivines and the groundmass of both L7 and A8 crystallized. The grain size of the groundmass of each sample reflects its burial depth. L7 crystallized near surface (~2 m) where the degree of melting was larger than for A8, which crystallized at a deeper burial depth but experienced less heating and melting. To realize such heating, impact would be appropriate. Hence, we conclude that L7 and A8 were formed under similar conditions and differences in xenocrysts were caused by differing degrees of melting. The coarser-grained groundmass of A8 was due to crystallization at greater depth than L7. However, some difficulty remains in relating the bulk compositions of A8 and L7 by simple olivine fractionation. This difficulty might be due to sample heterogeneity. Further bulk analysis and investigation of different PTS is required. We thank the MWG and NIPR for the samples. References: [1] McKay G. et al. (1990) LPS XXI, 771-772. [2] Mikouchi T. et al. (1994) LPS XXV, 907-908. [3] Yanai K. (1994) Proc. NIPR Symp. Antarc. Meteorites, 7, 30-41. [4] Mikouchi T. et al. (1995) 20th NIPR Symp. Antarc. Meteorites, 159-162. [5] Mikouchi T. et al. (1995) LPS XXVI, 973-974. [6] McKay G. et al. (1995) 20th NIPR Symp. Antarc. Meteorites, 155-158.

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

1995-09-01

237

Olivine in terminal particles of Stardust aerogel tracks and analogous grains in chondrite matrix  

NASA Astrophysics Data System (ADS)

The dearth of both major and minor element analyses of anhydrous silicate phases in chondrite matrix has thus far hindered their comparison to the Wild 2 samples. We present 68 analyses of olivine (Fa0-97) in the coarse-grained terminal particles of Stardust aerogel tracks and a comprehensive dataset (>103 analyses) of analogous olivine grains (5-30 ?m) isolated in CI, CM, CR, CH, CO, CV3-oxidized, CV3-reduced, C3-ungrouped (Acfer 094 and Ningqiang), L/LL 3.0-4, EH3, and Kakangari chondrite matrix. These compositions reveal that Wild 2 likely accreted a diverse assortment of material that was radially transported from various carbonaceous and ordinary chondrite-forming regions. The Wild 2 olivine includes amoeboid olivine aggregates (AOAs), refractory forsterite, type I and type II chondrule fragments and/or microchondrules, and rare relict grain compositions. In addition, we have identified one terminal particle that has no known compositional analog in the meteorite record and may be a signature of low-temperature, aqueous processing in the Kuiper Belt. The generally low Cr content of FeO-rich olivine in the Stardust samples indicates that they underwent mild thermal metamorphism, akin to a petrologic grade of 3.05-3.15.

Frank, David R.; Zolensky, Michael E.; Le, Loan

2014-10-01

238

Protracted fabric evolution in olivine: Implications for the relationship among strain, crystallographic fabric, and seismic anisotropy  

NASA Astrophysics Data System (ADS)

Crystallographic fabrics in olivine-rich rocks provide critical information on conditions and mechanisms of deformation as well as seismic properties of Earth's upper mantle. Previous interpretations of fabrics produced in laboratory experiments were complicated by uncertainty as to whether the steady-state fabric was attained. To examine the systematics of the evolution of olivine crystallographic fabrics at high strain, we conducted torsion experiments on olivine aggregates to shear strains of up to ?20. Our results demonstrate that a steady-state fabric is not reached until a shear strain >10, a much higher value than previously thought necessary. Fabrics characterized by girdles of [010] and [001] axes or by clusters of [010] and [001] axes are both observed. Until now, these fabrics were associated with either two different deformation mechanisms or two different sets of deformation conditions. Here we establish that both fabrics are, in fact, part of the same evolutionary process. An eigenvalue analysis allows the fabric shape to be quantitatively correlated with the magnitude of shear strain. Misorientation analysis suggests that the observed fabric evolution results from the competition of the two easiest slip systems in olivine, (010)[100] and (001)[100]. Our results open up the possibility of using olivine crystallographic fabrics or seismic anisotropy to quantitatively evaluate strain histories in both field studies and geophysical investigations of upper-mantle rocks.

Hansen, Lars N.; Zhao, Yong-Hong; Zimmerman, Mark E.; Kohlstedt, David L.

2014-02-01

239

Protracted fabric evolution in olivine: Implications for the relationship among strain, crystallographic fabric, and seismic anisotropy  

NASA Astrophysics Data System (ADS)

Crystallographic fabrics in olivine-rich rocks provide critical information on conditions and mechanisms of deformation as well as seismic properties of Earth's upper mantle. Previous interpretations of fabrics produced in laboratory experiments were complicated by uncertainty as to whether the steady-state fabric was attained. To examine the systematics of the evolution of olivine crystallographic fabrics at high strain, we conducted torsion experiments on olivine aggregates to shear strains of up to ~20. Our results demonstrate that a steady-state fabric is not reached until a shear strain >10, a much higher value than previously thought necessary. Fabrics characterized by girdles of [010] and [001] axes or by clusters of [010] and [001] axes are both observed. Until now, these fabrics were associated with either two different deformation mechanisms or two different sets of deformation conditions. Here we establish that both fabrics are, in fact, part of the same evolutionary process. An eigenvalue analysis allows the fabric shape to be quantitatively correlated with the magnitude of shear strain. Misorientation analysis suggests that the observed fabric evolution results from the competition of the two easiest slip systems in olivine, (010)[100] and (001)[100]. Our results open up the possibility of using olivine crystallographic fabrics or seismic anisotropy to quantitatively evaluate strain histories in both field studies and geophysical investigations of upper-mantle rocks.

Hansen, Lars; Zhao, Yong-Hong; Zimmerman, Mark; Kohlstedt, David

2014-05-01

240

Structural and Electrochemical Characterization of Lithium Transition Metal Phosphates  

NASA Astrophysics Data System (ADS)

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

Hashambhoy, Ayesha Maria

241

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

242

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

243

Geochemistry of Pallasite Olivines and the Origin of Main-Group Pallasites  

NASA Technical Reports Server (NTRS)

Main-group pallasites (PMG) are mixtures of iron-nickel metal and magnesian olivine thought to have been formed at the core-mantle boundary of an asteroid [1]. Some have anomalous metal compositions (PMG-am) and a few have atypically ferroan olivines (PMG-as) [2]. PMG metal is consistent with an origin as a late fractionate of the IIIAB iron core [2]. Most PMG olivines have very similar Fe/Mg ratios, likely due to subsolidus redox reaction with the metal [3]. In contrast, minor and trace elements show substantial variation, which may be explained by either: (i) PMG were formed at a range of depths in the parent asteroid; the element variations reflect variations in igneous evolution with depth, (ii) the pallasite parent asteroid was chemically heterogeneous; the heterogeneity partially survived igneous processing, or (iii) PMG represent the core-mantle boundaries of several distinct parent asteroids [4, 5]. We have continued doing major, minor and trace elements by EMPA and INAA on a wider suite of PMG olivines, and have begun doing precise oxygen isotope analyses to test these hypotheses. Manganese is homologous with Fe(2+), and can be used to distinguish between magmatic and redox processes as causes for Fe/Mg variations. PMG olivines have a range in molar 1000*Mn/Mg of 2.3-4.6 indicating substantial igneous fractionation in olivines with very similar Fe/Mg (0.138-0.148). The Mg-Mn-Fe distributions can be explained by a fractional crystallization-reduction model; higher Mn/Mg ratios reflect more evolved olivines while Fe/Mg is buffered by redox reactions with the metal. There is a positive association between Mn/Mg and Sc content that is consistent with igneous fractionation. However, most PMG olivines fall within a narrow Mn/Mg range (3.0-3.6), but these show a substantial range in Sc (1.00-2.29 micro-g/g). Assuming fractional crystallization, this Sc range could have resulted from approx.65% crystallization of an ultramafic magma. This is inconsistent with formation at the core-mantle boundary of a single asteroid [4]. One alternative is that the PMG are fragments of several asteroids, and these could have had different initial Sc contents, Mn/Mg and differences in igneous history. Our preliminary O isotope data and those of [6, 7] do not support this, although the coverage of PMG olivines is incomplete. The PMG-as Springwater is not easily fit in any scenario. Its olivine has among the highest Mn/Mg suggesting it is one of the most evolved, but the lowest Sc content suggesting it is the least evolved. The O isotopic composition of Springwater olivine is the same as that of other PMG. Thus there is no indication that it represents a distinct parent asteroid. Our preliminary O isotopic data favor a single PMG parent asteroid. In this case, the olivines are more likely melt-residues, and that the parent asteroid was initially heterogeneous in chemical, but not isotopic, composition.

Mittlefehldt, D. W.; Rumble, D., III

2006-01-01

244

Chemical zoning and diffusion of Ca, Al, Mn, and Cr in olivine of springwater pallasite  

NASA Technical Reports Server (NTRS)

The pallasites, consisting mainly of Fe-Ni metal and olivine, are thought to represent the interior of a planetary body which slowly cooled from high temperature. Although the olivines are nearly homogeneous, ion microprobe studies revealed variations of Ca, Ti, Co, Cr, and Ni near grain edges. These variations were thought to represent diffusion in response to falling temperature of the parent body. Pallasite cooling rates have been estimated based on kamacite taenite textures but results differ by x100. In principle elemental profiles in olivine can allow estimates of cooling rate if diffusion coefficients are known; in addition, given a cooling rate, diffusion coefficients could be derived. Data are presented which show that apparent diffusion profiles can be measured for Al, Ca, Cr, and Mn which qualitatively agree with expected diffusion rates and have the potential of providing independent estimates of pallasite cooling rates.

Zhou, Y.; Steele, Ian M.

1993-01-01

245

Olivine Weathering and Sulfate Formation Under Cryogenic Conditions  

NASA Astrophysics Data System (ADS)

High resolution photography and spectroscopy of the martian surface (MOC, HiRISE) from orbit has revolutionized our view of Mars with one of the most important discoveries being wide-spread layered sedimentary deposits associated with sulfate minerals across the low to mid latitude regions of Mars. The mechanism for sulfate formation on Mars has been frequently attributed to playa-like evaporative environments under prolonged warm conditions. An alternate view of the ancient martian climate contends that prolonged warm temperatures were never present and that the atmosphere and climate has been similar to modern conditions throughout most of its history. This view has had a difficult time explaining the sedimentary history of Mars and in particular the presence of sulfate minerals which seemingly need more water. We suggest here that mixtures of atmospheric aerosols, ice, and dust have the potential for creating small films of cryo-concentrated acidic solutions that may represent an important unexamined environment for understanding weathering processes on Mars. This study seeks to test whether sulfate formation may be possible at temperatures well below 0C in water limited environments removing the need for prolonged warm periods to form sulfates on early Mars. To test this idea we performed laboratory experiments to simulate weathering of mafic minerals under Mars-like conditions. The weathering rates measured in this study suggest that fine grained olivine on Mars would weather into sulfate minerals in short time periods if they are exposed to H2SO4 aerosols at temperatures at or above -40C. In this system, the strength of the acidic solution is maximized through eutectic freezing in an environment where the silicate minerals are extremely fine grained and have high surface areas. This provides an ideal environment despite the very low temperatures. On Mars the presence of large deposits of mixed ice and dust is undisputed. The presence of substantial sulfur-rich volcanism, and sulfur-rich surface deposits also makes it very likely that sul-fate aerosols have also been an important component of the martian atmosphere. Thus mixtures of ice, dust, and sulfate aerosols are likely to have been common on the martian surface. Given the fact that it is not difficult to achieve surface temperatures above -40C on Mars throughout its history, it seems likely that sulfate formation on Mars is controlled by the availability of sulfate aerosols and not by the martian climate. The current polar regions of Mars and Earth provide interesting analogs. Large regions of sulfate-rich material have been detected on and around the modern north polar region of Mars. The prevalence of ice-dust mixtures in this region and the existence of sulfates within the ice cap itself are strong evidence for the origin of the sulfates from inside the ice deposits. In addition sulfates have been found in ice deposits in Greenland and Mount Fuji on Earth that have been attributed to forming within the ice deposit. These sulfates can form either through interaction with dust particles in the atmosphere or through weathering inside the ice itself.

Niles, P. B.; Golden, D. C.; Michalski, J. R.

2013-12-01

246

Dynamic crystallization of chondrule melts of porphyritic olivine composition - Textures experimental and natural  

NASA Astrophysics Data System (ADS)

A full range of textures characteristic for porphyritic olivine chondrules was reproduced in melts of the same composition, crystallized under dynamic crystallization conditions (under controlled cooling), as determined by electron microprobe analyses. The primary differences between the natural and experimentally produced porphyritic olivine textures were the nature and the extent of matrix crystallization, which reflected the subsolidus or low-temperature cooling history. The most confining limits on the chondrule-forming process were found to be the presence of crystalline precursors for the chondrule melts and the upper temperature limit of melting.

Lofgren, G.

1989-02-01

247

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

248

Short- and long-term olivine weathering in Svalbard: implications for Mars.  

PubMed

Liquid water is essential to life as we know it on Earth; therefore, the search for water on Mars is a critical component of the search for life. Olivine, a mineral identified as present on Mars, has been proposed as an indicator of the duration and characteristics of water because it dissolves quickly, particularly under low-pH conditions. The duration of olivine persistence relative to glass under conditions of aqueous alteration reflects the pH and temperature of the reacting fluids. In this paper, we investigate the utility of 3 methodologies to detect silicate weathering in a Mars analog environment (Sverrefjell volcano, Svalbard). CheMin, a miniature X-ray diffraction instrument developed for flight on NASA's upcoming Mars Science Laboratory, was deployed on Svalbard and was successful in detecting olivine and weathering products. The persistence of olivine and glass in Svalbard rocks was also investigated via laboratory observations of weathered hand samples as well as an in situ burial experiment. Observations of hand samples are consistent with the inference that olivine persists longer than glass at near-zero temperatures in the presence of solutions at pH approximately 7-9 on Svalbard, whereas in hydrothermally altered zones, glass has persisted longer than olivine in the presence of fluids at similar pH at approximately 50 degrees C. Analysis of the surfaces of olivine and glass samples, which were buried on Sverrefjell for 1 year and then retrieved, documented only minor incipient weathering, though these results suggest the importance of biological impacts. The 3 types of observations (CheMin, laboratory observations of hand samples, burial experiments) of weathering of olivine and glass at Svalbard show promise for interpretation of weathering on Mars. Furthermore, the weathering relationships observed on Svalbard are consistent with laboratory-measured dissolution rates, which suggests that relative mineral dissolution rates in the laboratory, in concert with field observations, can be used to yield valuable information regarding the pH and temperature of reacting martian fluids. PMID:19191538

Hausrath, E M; Treiman, A H; Vicenzi, E; Bish, D L; Blake, D; Sarrazin, P; Hoehler, T; Midtkandal, I; Steele, A; Brantley, S L

2008-12-01

249

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

NASA Astrophysics Data System (ADS)

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

Plmper, O.; Ryne, A.; Malthe-Srenssen, A.; King, H. E.; Jamtveit, B.

2012-04-01

250

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

251

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

252

Dehydration breakdown of antigorite and the formation of B-type olivine CPO  

NASA Astrophysics Data System (ADS)

Peridotite formed by contact metamorphism and dehydration breakdown of an antigorite schist from the Happo area, central Japan shows a strong olivine crystallographic preferred orientation (Ol CPO). The lack of mesoscale deformation structures associated with the intrusion and the lack of microstructural evidence for plastic deformation of neoblastic grains suggest that olivine CPO in this area did not form as a result of solid-state deformation. Instead, the good correspondence between the original antigorite orientation and the orientation of the newly formed olivine implies the CPO formed by topotactic growth of the olivine after antigorite. Ol CPO is likely to develop by a similar process in subduction zone environments where foliated serpentinite is dragged down to depths where antigorite is no longer stable. The Happo Ol CPO has a strong a-axis concentration perpendicular to the lineation and within the foliation-commonly referred to as B-type Ol CPO. Seismic fast directions parallel to the ocean trench are observed in many convergent margins and are consistent with the presence of B-type Ol CPO in the mantle wedge of these regions. Experimental work has shown that B-type CPO can form by dislocation creep under hydrous conditions at relatively high stresses. There are, however, several discrepancies between the characteristics of natural and laboratory samples with B-type Ol CPO. (1) The formation conditions (stress and temperature) of some natural examples with B-type CPO fall outside those predicted by experiments. (2) In deformation experiments, slip in the crystallographic c-axis direction is important but has not been observed in natural examples of B-type CPO. (3) Experimental work suggests the presence of H2O and either high shear stress or relatively low temperatures are essential for the formation of B-type CPO. These conditions are most likely to be achieved close to subduction boundaries, but these regions are also associated with serpentinization, which prevents strong olivine CPO patterns from forming. We show B-type Ol CPO can form as a result of static topotactic growth of olivine after high-temperature breakdown of foliated serpentinite. These results resolve the discrepancies between experimental and natural examples of B-type CPO and show the need to rethink the formation process of olivine CPO in convergent margins. Topotactic growth of olivine after antigorite can account for the inferred distribution of B-type Ol CPO in the mantle wedge more successfully than dislocation creep.

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

2014-02-01

253

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

NASA Astrophysics Data System (ADS)

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

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

2000-11-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2001-02-01

255

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

PubMed

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

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

2013-10-01

256

FeMg diffusion in olivine II: point defect chemistry, change of diffusion mechanisms and a model for calculation of diffusion coefficients in natural olivine  

Microsoft Academic Search

Analysis of existing data and models on point defects in pure (Fe,Mg)-olivine (Phys Chem Miner 10:2737,1983; Phys Chem Miner 29:680694, 2002) shows that it is necessary to consider thermodynamic non-ideality of mixing to adequately describe the concentration of\\u000a point defects over the range of measurement. In spite of different sources of uncertainties, the concentrations of vacancies\\u000a in octahedral sites in

Ralf Dohmen; Sumit Chakraborty

2007-01-01

257

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

258

Compositional controls on spinel clouding and garnet formation in plagioclase of olivine metagabbros, Adirondack Mountains, New York  

Microsoft Academic Search

Olivine metagabbros from the Adirondacks usually contain both clear and spinel-clouded plagioclase, as well as garnet. The latter occurs primarily as the outer rim of coronas surrounding olivine and pyroxene, and less commonly as lamellae or isolated grains within plagioclase. The formation of garnet and metamorphic spinel is dependent upon the anorthite content of the plagioclase. Plagioclase more sodic than

James M. McLelland; Philip R. Whitney

1980-01-01

259

The partitioning of Fe and Mg between olivine and carbonate and the stability of carbonate under mantle conditions  

Microsoft Academic Search

We have investigated the effect of Fe on the stabilities of carbonate (carb) in lherzolite assemblages by determining the partitioning of Fe and Mg between silicate (olivine; ol) and carbonates (magnesite, dolomite, magnesian calcite) at high pressures and temperatures. Fe enters olivine preferentially relative to magnesite and ordered dolomite, but Fe and Mg partition almost equally between disordered calcic carbonate

John A. Dalton; Bernard J. Wood

1993-01-01

260

Shock-compressed MgSiO3 glass, enstatite, olivine, and quartz: Optical emission, temperatures, and melting  

E-print Network

Shock-compressed MgSiO3 glass, enstatite, olivine, and quartz: Optical emission, temperatures glass, enstatite, olivine, and quartz: Optical emission, temperatures, and melting, J. Geophys. Res March 2004; accepted 10 March 2004; published 11 May 2004. [1] Optical emission of MgSiO3 glass

Stewart, Sarah T.

261

Nitrogen Isotopes in Olivine Separates from Volcanic Arcs, Hot Spots and Continental Mantle Xenoliths  

NASA Astrophysics Data System (ADS)

We report the first nitrogen isotopic data of olivine separates from volcanic arcs (Cerro Negro, Nicaragua; Izalco, El Salvador; Turrialba, Costa Rica; Ichinomegata, Japan). In addition, we report nitrogen isotopic data of olivine separates from ocean islands (Hawaii, Reunion, Iceland) and continental mantle xenoliths (San Carlos, Arizona). Samples were processed by crushing and analyzed using a modified noble gas mass spectrometer (VG3400). N concentrations range from 0.6 to 22 micro ccSTP/g olivine. The 15N/14N ratios (expressed in the ? 15N notation where ? 15N sample = {[(15N/14N)sample/(15N/14N)Air]-1} X 1000) of olivine separates are distinctly different from air (0.0 ) and range from lower than mean MORB (- 5 ) to values characteristic of (subducted) oceanic sediments (+ 7 ). Positive ? 15N values are found in olivines from volcanic arcs: Cerro Negro 1992 ash (+ 6.2 1.6 ), Izalco lava flow (+ 5.1 0.7 ), Ichinomengata spinel lherzolite (+ 1.1 0.5 ) with the exception of Turrialba lava (- 1.7 2.5 ). Olivines from hot spots have both positive and negative ? 15N signatures: Iceland, Theistareykir - northern rift zone (- 8 1.6 ), Hawaii, dunite from 1801 Kaupulehu flow of Hualuai volcano (+ 3.1 0.3 ) and Reunion dunite (+ 0.2 0.5 ). The San Carlos mantle xenolith has a value of - 1.5 2.5 . 40Ar/36Ar ratios of the samples as determined in this study or reported in the literature are significantly higher than air (295.5) in olivines from Ichinomegata, San Carlos, Iceland, Reunion and Hawaii. The olivines from Cerro Negro have a 40Ar/36Ar ratio of 306, close to that of air. The 3He/4He ratios of the samples are higher than the MORB value of 8.0 RA (RA is the 3He/4He of air), the exception being Cerro Negro (6.1 RA). Hawaii, Reunion and Iceland have 3He/4He of 10.3, 12.9 and 12.3 RA, respectively. ? 15N signatures of fumarole gas samples collected at Cerro Negro (+ 4.9 0.1 ), Turrialba (- 1.0 0.3 ) and localities close to Izalco (+ 4.0 0.4 ) are identical (within error) to those of the olivine separates. The results obtained in this study are significant and show that 1) N isotopes in olivine separates and volcanic/hydrothermal gas emissions both sample volatiles that are primarily derived from the magma source. 2) subduction of oceanic sediments and transfer of N through the mantle wedge controls the N isotopic composition in volcanic arcs as sampled by olivine separates and gas discharges. 3) the N isotopic signature of hot spot related volatiles is variable but the samples from Hawaii, and to a lesser extent from Reunion, support the idea that surficial N (from subducted sediments or oceanic basement) is recycled into the lower mantle. 4) N as sampled by the San Carlos mantle xenolith may record a greater extent of air contamination than the other samples. Alternatively, N data of San Carlos and the Iceland northern rift zone suggests that the N isotopic signature of the upper mantle may be more variable than previously inferred from MORB samples.

Fischer, T. P.; Takahata, N.; Sano, Y.; Hilton, D. R.

2004-12-01

262

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

263

Telling zoned from zoned: LA-MC-ICPMS and SIMS iron isotopic measurements of olivine  

NASA Astrophysics Data System (ADS)

Previous studies have revealed that iron and magnesium isotopes may be used to distinguish diffusion-driven zoning from crystal growth zoning in olivine crystals [1-3]. In magmatic systems, Mg-rich olivine is an early crystallizing phase. As the melt evolves, it becomes more Fe-rich, so that in reaching equilibrium, Fe diffuses into and Mg diffuses out of the initial olivine crystal. Because light isotopes diffuse faster than heavy isotopes [4], such diffusion-driven mechanism is accompanied with 1) a negative correlation of Fe and Mg isotopes, and 2) a negative correlation of Fe isotopes and a positive correlation of Mg isotopes with Fo#. Teng et al. [1] showed these correlations in olivine fragments from Kilauea Iki lava lake. Sio et al. [3] used microdrilling techniques to spatially resolve the same correlations in an olivine phenocryst from the Kilauea Iki lava lake. LA-MC-ICPMS and SIMS were used to measure Fe isotopes in the same olivine phenocryst [5]. These techniques provide lateral and depth resolution approximately an order of magnitude higher than microdrilling. There is perfect agreement in iron isotopic measurements between these three techniques. The rim of the olivine is at -0.2 and the core is at -1.3 in ?56Fe relative to IRMM-014. The thermal history and petrography of the Kilauea Iki lava lake is known, so diffusion-controlled zoning in the olivine phenocryst may be modeled as in a laboratory experiment. After measuring the crystallographic orientation of the olivine with TEM in a FIB section, the average Mg-Fe interdiffusion coefficient is calculated as a fraction of DMg-Fe along the [001] axis. The derived DFe-Mg[001] appears to be 1.1 to 8.6 times higher than the parameterization given by [6]. The large range in DFe-Mg[001] results from slight uncertainties in the initial lake temperature and the geometry of the olivine phenocryst used in the modeling. The empirical ?, used to relate diffusivities of isotopes of the same element expressed in Dl/Dh = (mh/ml)^? where l stands for the light isotope, and h stands for the heavy isotope, is 0.22-0.29 for 54Fe and 56Fe, and 0.16-0.20 for 24Mg and 26Mg. These ?-values are significantly higher than those documented in magmas [4]. LA-MC-ICPMS and SIMS provide the means to measure iron isotopic compositions with high spatial resolution in olivines. Such techniques can be employed on zoned crystals to understand their crystallization and cooling histories. Our work establishes LA-MC-ICPMS and SIMS Fe isotopic analyses as a powerful tool of petrology in the study of zoned minerals. [1] Teng et al. (2011) EPSL 308, 317-324. [2] Dauphas et al. (2010) Geochim. Cosmochim. Acta 74, 3274-3291. [3] Sio et al. (2011) Goldschmidt Abstract 1884. [4] Richter et al. (2009) Geochim. Cosmochim. Acta 73, 4250-4263. [5] Sio et al. (2011) Goldschmidt Abstract 974. [6] Dohmen et al. (2007) Phys Chem Minerals 34, 597-598

Sio, C.; Dauphas, N.; Teng, F.; Chaussidon, M.; Helz, R. L.; Roskosz, M.

2012-12-01

264

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

265

Metastable olivine wedge and deep dry cold slab beneath southwest Japan  

NASA Astrophysics Data System (ADS)

Oceanic plates subducted at trenches penetrate into the deep mantle, and encounter a structural boundary at a depth of 410 km where olivine, the dominant element of mantle rocks, transforms into a higher density form wadsleyite. This transformation may be delayed within the coldest core of subducting plates (slabs) due to kinetic effects, and it has been suggested that metastable olivine may persist deeper than 410 km. Using high density seismic array data in Japan, we show the direct image of the structure corresponding to this metastable olivine wedge (MOW) beneath southwest Japan. Numerical simulation of a subducting slab, including the kinetic effect of water (H 2O) on the olivine-wadsleyite transformation, indicates that the presence of the imaged MOW requires an insignificant amount of water (less than 100 wt. ppm) be present in the slab mantle, thus a deep dry cold slab. We infer that the transportation of water into the deep mantle occurs along the top surface of the subducting slab, but no significant amount within the slab itself. We also demonstrate that a numerical simulation including the kinetics of 660-km phase transformation can reconcile the observed deep depression of the 660-km discontinuity with a gentle Clapeyron slope.

Kawakatsu, Hitoshi; Yoshioka, Shoichi

2011-02-01

266

THE ORIGIN OF BROWN OLIVINE IN MARTIAN DUNITE C. M. Pieters1  

E-print Network

the visible through the near-infrared part of the spectrum are shown to be due to nano- phase metallic iron visible and near-infrared reflec- tance, mid-infrared emission and reflectance, and Mössbauer molecular structure remains intact. Near- infrared spectra of NWA 2737 olivine are compared with those

Hiroi, Takahiro

267

Space weathering simulations through controlled growth of iron nanoparticles on olivine  

E-print Network

Airless planetary bodies are directly exposed to space weathering. The main spectral effects of space weathering are darkening, reduction in intensity of silicate mineral absorption bands, and an increase in the spectral slope towards longer wavelengths (reddening). Production of nanophase metallic iron (npFe$^{0}$) during space weathering plays major role in these spectral changes. A laboratory procedure for the controlled production of npFe$^{0}$ in silicate mineral powders has been developed. The method is based on a two-step thermal treatment of low-iron olivine, first in ambient air and then in hydrogen atmosphere. Through this process, a series of olivine powder samples was prepared with varying amounts of npFe$^{0}$ in the 7-20 nm size range. A logarithmic trend is observed between amount of npFe$^{0}$ and darkening, reduction of 1 um olivine absorption band, reddening, and 1 um band width. Olivine with a population of physically larger npFe$^{0}$ particles follows spectral trends similar to other samp...

Kohout, T; Filip, J; Britt, D; Bradley, T; Tu?ek, J; Skla, R; Kletetschka, G; Kalk, J; Malina, O; ikov, K; Zbo?il, R

2014-01-01

268

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

269

Deformation of olivine in torsion under hydrous conditions Sylvie Demouchy a,  

E-print Network

Deformation of olivine in torsion under hydrous conditions Sylvie Demouchy a, , Andréa Tommasi Crystal-preferred orientation Seismic anisotropy a b s t r a c t We performed torsional deformation-pressed and then hot-pressed under hydrous conditions, pro- ducing aggregates with average grain sizes of 7 or 15 lm

Tommasi, Andrea

270

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

271

Herschel/PACS observations of the 69 $\\mu m$ band of crystalline olivine around evolved stars  

E-print Network

We present 48 Herschel/PACS spectra of evolved stars in the wavelength range of 67-72 $\\mu$m. This wavelength range covers the 69 $\\mu$m band of crystalline olivine ($\\text{Mg}_{2-2x}\\text{Fe}_{(2x)}\\text{SiO}_{4}$). The width and wavelength position of this band are sensitive to the temperature and composition of the crystalline olivine. Our sample covers a wide range of objects: from high mass-loss rate AGB stars (OH/IR stars, $\\dot M \\ge 10^{-5}$ M$_\\odot$/yr), through post-AGB stars with and without circumbinary disks, to planetary nebulae and even a few massive evolved stars. The goal of this study is to exploit the spectral properties of the 69 $\\mu$m band to determine the composition and temperature of the crystalline olivine. Since the objects cover a range of evolutionary phases, we study the physical and chemical properties in this range of physical environments. We fit the 69 $\\mu$m band and use its width and position to probe the composition and temperature of the crystalline olivine. For 27 sourc...

Blommaert, J A D L; Waters, L B F M; Waelkens, C; Min, M; Van Winckel, H; Molster, F; Decin, L; Groenewegen, M A T; Barlow, M; Garca-Lario, P; Kerschbaum, F; Posch, Th; Royer, P; Ueta, T; Vandenbussche, B; Van de Steene, G; van Hoof, P

2014-01-01

272

Olivine hydration in the deep upper mantle: Effects of temperature and silica activity  

Microsoft Academic Search

Although water controls the biology and geology of the surface, hydrogen is perhaps the most poorly constrained compositional variable in the bulk Earth. Its concentration in the upper mantle appears to be controlled by its solubility as hydroxyl in the nominally anhydrous silicate phases, olivine, pyroxene, garnet, wadsleyite, and ringwoodite. Here we describe a series of experiments showing that the

J. R. Smyth; D. J. Frost; F. Nestola; C. M. Holl; G. Bromiley

2006-01-01

273

Olivine-hosted melt inclusions and melting processes beneath the FAMOUS zone (Mid-Atlantic Ridge)  

E-print Network

important information about the processes of melt generation beneath mid-ocean ridges. They contain near; Olivine; Mid-ocean ridge basalts; Mantle melting 1. Introduction Melt generation at mid-ocean ridges-element systematics of MORB (mid- ocean ridge basalts) have been explained in terms of variation of the potential

Laubier, Muriel

274

Mixing primitive and evolved olivine tholeiite magmas in the Eastern Snake River Plain, Idaho  

Microsoft Academic Search

Butte 5206, a small monogenetic olivine tholeiite basalt (OTB) shield in the Eastern Snake River Plain (ESRP), erupted during late-Pleistocene time along the ArcoBig Southern Butte Volcanic Rift Zone. Geochemical data from Butte 5206 and other basalts that erupted in the vicinity, including correlated samples from coreholes, are evaluated for possible mechanisms of magma evolution in the ESRP. Thermodynamic and

Myles L. Miller; Scott S. Hughes

2009-01-01

275

Genesis of a Chemically Enriched Olivine Tholeiite from the Eastern Snake River Plain, Idaho  

Microsoft Academic Search

The eastern Snake River Plain (ESRP) volcanic province is overlain by 1-2 km of dominantly Quaternary olivine tholeiite lava flows associated with the Yellowstone hotspot. A second highly evolved geochemical basalt suite has been identified in previous studies, typified by the lava flows of Craters of the Moon National Monument (COM). Geochemical data from three new coreholes drilled on the

C. G. Chadwick; S. S. Hughes; M. McCurry; J. Chadwick

2004-01-01

276

Pyroxenes and olivines: Structural implications of shock-wave data for high pressure phases  

NASA Technical Reports Server (NTRS)

The nature of the shock-induced, high-pressure phases of olivine and pyroxene rocks is examined in the light of data for the densities of a new class of perovskite-related silicate structures. Also examined are some new Hugoniot and release adiabat data for bronzite. Reexamining available shock data for magnesian pyroxenes and olivines leads to the conclusion that they define a mixed phase (or disequilibrium) region to about the 100 GPa range, related to the kinetics of phase transformation in these silicates. By recognizing this point, certain discrepancies in previous interpretations of shock data can be explained. A set of theoretical Hugonoits for pyroxene and olivine stoichiometry, perovskite-bearing assemblages was constructed based on their properties deduced from high-pressure work, showing that the shock data is compatible with transformations to perovskites in the 45-7GPa region. Finally, the shock data indicate very similar properties for olivine and pyroxene at high pressures making them both equally likely candidates for the lower mantle.

Jeanloz, R.; Ahrens, T. J.

1975-01-01

277

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

278

Effect of Water and Iron Content on the Rheological Behavior of Olivine  

NASA Astrophysics Data System (ADS)

We have undertaken an experimental investigation of the effect of water and iron content on the viscosity of aggregates of Fe-Mg olivine in order to provide a basis for conparing convection models for the mantle of Earth with those for the more iron-rich mantle of Mars. Our study builds on three experimental observations: (i) At a given temperature, the viscosity of single crystals of San Carlos olivine [Fo90 = (Fe0.1Mg0.9)2SiO4] is signficantly higher than that of crystals of fayalite, Fo0, (ii) the viscosity of San Carlos olivine decreases with increasing water concentration, and (iii) the solubility of water in olivine increases with increasing iron concentration. To extend deformation experiments to polycrystalline samples of olivine of higher Fe content, powders of Fo50 and Fo70 were fabricated from mixtures of natural olivine, Fo90, and synthetic fayalite, Fo0. The resulting materials were ground into fine (<10 ? m) powders, cold-pressed into Ni capsules, and then hot-pressed at 300 MPa and 1533 K for 2 to 12 h. For experiments under hydrous conditions, two drops of water, each 0.03 ml, were added before sealing a sample within telescoping Ni cans for deformation. The average grain size of the resultant hot-pressed samples were between 20 and 57 ? m . In the samples deformed under hydrous conditions, water bubbles were present both within olivine grains and along grain boundaries, demonstrating that the samples were water-saturated. High-temperature, high-pressure compressive creep experiments in both the diffusion and the dislocation creep regimes were carried out using a gas-medium apparatus at temperatures of 1223 to 1473 K and a confining pressure of 300 MPa. Under both anhydrous and hydrous conditions, the viscosity of samples of Fo50 is a factor of >10 lower than the viscosity of samples of Fo70, which is a factor of >10 lower than the viscosity of samples of Fo90. The viscosity of a sample of a specific Fe:Mg ratio deformed under hydrous conditions is a factor of 10 lower than its counterpart deformed under anhydrous conditions. Therefore, at the same thermodynamic conditions (e.g., P, T, water fugacity), the viscosity of the more Fe-rich mantle ( 18 wt % FeO) of Mars will be a factor of 3 lower than the mantle ( 8 wt % FeO) of Earth.

Zimmerman, M. E.; Zhao, Y.; Kohlstedt, D. L.

2004-12-01

279

UNDERSTANDING OLIVINE CO2 MINERAL SEQUESTRATION MECHANISMS AT THE ATOMIC LEVEL: OPTIMIZING REACTION PROCESS DESIGN  

SciTech Connect

Carbonation of Mg-rich minerals offers an intriguing candidate carbon sequestration process technology, which can provide large-scale CO{sub 2} disposal. Such disposal bypasses many long-term storage problems by (i) providing containment in the form of mineral carbonates that have proven stable over geological time, (ii) generating only environmentally benign materials, and (iii) essentially eliminating the need for continuous site monitoring. The primary challenge for viable process development is reducing process cost. This is the primary focus of the CO{sub 2} Mineral Sequestration Working Group managed by Fossil Energy at DOE, which includes members from the Albany Research Center, Los Alamos National Laboratory, the National Energy Technology Laboratory, Penn State University, Science Applications International Corporation, and the University of Utah, as well as from our research group at Arizona State University. Carbonation of the widely occurring mineral olivine (e.g., forsterite, Mg{sub 2}SiO{sub 4}) is a leading process candidate, which converts CO{sub 2} into the mineral magnesite (MgCO{sub 3}). As olivine carbonation is exothermic, it offers intriguing low-cost potential. Recent studies at the Albany Research Center have found aqueous-solution carbonation is a promising approach. Cost effectively enhancing carbonation reactivity is central to reducing process cost. Many of the mechanisms that impact reactivity occur at the solid/solution interface. Understanding these mechanisms is central to the ability to engineer new and modified processes to enhance carbonation reactivity and lower cost. Herein, we report the results of our UCR I project, which focused on exploring the reaction mechanisms that govern aqueous-solution olivine carbonation using model olivine feedstock materials. Carbonation was found to be a complex process associated with passivating silica layer formation, which includes the trapping of magnesite nanocrystals within the passivating silica layers, cracking and exfoliation of the layers, silica surface migration, olivine etch pit formation, transfer of the Mg and Fe in the olivine into the product carbonate, and the nucleation and growth of magnesite crystals on/in the silica/olivine reaction matrix. These phenomena occur in concert with the large solid volume changes that accompany the carbonation process, which can substantially impact carbonation reactivity. Passivating silica layer formation appears to play a major role in inhibiting carbonation reactivity. New approaches that can mitigate the effectiveness of passivating layer formation may offer intriguing potential to enhance carbonation reactivity and lower process cost.

M.J. McKelvy; H. Bearat; A.V.G. Chizmeshya; R. Nunez; R.W. Carpenter

2003-08-01

280

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

281

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

282

Mantle potential temperatures at Hawaii, Iceland, and the mid-ocean ridge system, as inferred from olivine phenocrysts: Evidence for thermally driven mantle plumes  

Microsoft Academic Search

(1) Temperature differences between lavas erupted at ocean islands and mid-ocean ridges are crucial to documenting the existence of mantle plumes. Olivines are useful for T estimation because they provide a less homogenized account of the melting process compared to glass and whole rock samples. Olivine- liquid equilibria, and olivine phenocrysts from Hawaii, Iceland, and several mid-ocean ridge localities, indicate

Keith D. Putirka

2005-01-01

283

Magma plumbing system of the 2000 eruption of Miyakejima volcano, Japan, deduced from volatile and major component contents of olivine-hosted melt inclusions  

Microsoft Academic Search

Chemical analyses of 56 olivine-hosted melt inclusions and their host olivines from the explosive eruption of Miyakejima volcano, Japan, on 18 August 2000 were carried out by electron probe micro analyzer and secondary ion mass spectrometry in order to investigate the magma plumbing system of the eruption. The bimodal olivine core composition, relatively small rims, and diffusion profiles of the

Genji Saito; Yuichi Morishita; Hiroshi Shinohara

2010-01-01

284

Constraining kinetics of metastable olivine in the Marianas slab from seismic observations and dynamic models  

NASA Astrophysics Data System (ADS)

Transformation kinetics associated with the presence of a metastable olivine wedge in old and fast subducting slabs has been the subject of many studies in the last years. Even with improvements in kinetics models, many of the parameters are still not well constrained. In particular, there is no consensus on the blocking temperature that could inhibit the transformation from olivine to spinel. Recently, based on anomalous later phases in the P wave coda and differential P wave slowness, a wedge of metastable olivine was detected in the Marianas subduction zone, that is approximately 25 km wide, at a depth of 590 km and is truncated at 630 km. In this work, a thermomechanical model was used to mimic the subduction in the Marianas and try different blocking temperatures for the olivine/spinel transformation. The model includes, among other features, non-linear elasto-visco-plastic rheology based on laboratory data, phase transformations, latent heat, proper coupling between stress and thermal state of the slab and force balance of the system. The results show a positive correlation between the blocking temperature, depth of the wedge and its distance from the trench (or subduction angle). We compare these results to the situation in the Marianas and suggest that a blocking temperature for the olivine/spinel transformation of approximately 725 C would be the most likely. The volume of the wedge presents some oscillations that we relate to a runaway effect of the transformation kinetics in the mantle transition zone. Namely, the interaction between latent heat release and the advection of the isotherms due to the subduction velocity. The inclusion of shear heating in the model was fundamental to modeling such a subduction zone. Without shear heating, the slab shows a higher level of internal stress and the necessary bending to mimic the Marianas subduction zone cannot be reached.

Quinteros, Javier; Sobolev, Stephan V.

2012-03-01

285

Is Olivine Speedometer a Reliable Tool to Constrain Thermal Story of SNC Meteorite?  

NASA Astrophysics Data System (ADS)

Several quantitative studies on thermal stories of SNC meteorites have been carried out to infer burial depth. Two approaches are generally used: (i) indirect estimation based on textural observation compared with products from controlled cooling crystallization experiment (ii) direct quantitative cooling rate calculation from diffusion zoning in mineral. The first method, applied on basaltic shergottite, is largely based on textures and compositions of pyroxene and/or maskelinite. The second one, performed on picritic shergottite (EET79001 and Dar al Gani 476) and the nakhlite NWA 817, uses zoning of olivine to extract cooling rate. At the onset of cooling, olivine was homogeneous and was then modified by atomic diffusion due to contact with Fe-rich surrounding melt when olivine was incorporated as a xenocryst. It had long been argued that olivine speedometer, giving absolute cooling rate, was the reliable method compared to the first one which bears large uncertainties. Unfortunately any contribution using olivine as a speedometer in meteorites are negligent (or at least optimistic) about the assignment of uncertainties to cooling rate estimate. In such studies numerical procedures, where diffusion equation is solved by finite difference approximation, are generally preferred to analytical one. However error propagation becomes obvious when using analytical methods in as much they allow the dependence of cooling rate results on input parameter to be clearly seen. For instance temperature To and diffusion data (E the activation energy and Do the preexponential term of diffusion coefficient D expressed through the Arrhenius law) are first order parameters in cooling rate equation. Small errors on temperature and diffusion data are magnified due to the logarithmic relation ship between input T and cooling rate S.

Sautter, V.; Barrat, J. A.; Jambon, A.

2002-01-01

286

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 30N 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

287

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

288

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

289

Mineral sequestration of carbon dioxide in San Carlos olivine: An atomic level reaction study  

NASA Astrophysics Data System (ADS)

Since the late 19th century, atmospheric carbon dioxide (CO2) levels have been steadily on the rise. Approximately one third of all human emissions come from fossil fuel power plants. As countries become more dependent on electrical energy and bring on line new power plants, these atmospheric CO2 levels will continue to rise, generating strong environmental concern. Potential avenues to address this problem convert the CO2 from the gaseous phase to a liquid, supercritical fluid, or solid state and store it. Oceans, subsurface reservoirs such as depleted oil fields, and terrestrial carbon pools have all been suggested. The essential problem with all of these possible solutions is the issue of permanency. Mineral sequestration of CO2 is a candidate technology for reducing the amount of anthropogenic CO2 that is being released into the atmosphere. Olivine (e.g. forsterite, Mg2SiO4) is a widely available mineral that reacts with CO2 to form magnesite (MgCO3) and silica (SiO2). Magnesite is capable of immobilizing CO2 over geological time periods. Thus the issue of permanency has been addressed. The most promising mineral sequestration process developed to date is aqueous solution mineral carbonation. The solid/aqueous solution reaction interface provides insight to the mechanisms that govern the carbonation reactivity of olivine. Study of these mechanisms at the atomic level is critically important to facilitate engineering new processes that will enhance the reactivity of olivine with CO2 bearing media and to lower process costs. The study of the olivine carbonation reaction herein can be divided into three separate areas of research. The first area is a comprehensive study of olivine under conditions of electron irradiation. Analyzing radiation damage is critical to the verification and reliability of data collected from the samples using electron beam techniques. The next area of research is the analysis of the reaction layer composition and structure using High Resolution Electron Microscopy (HREM), Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), Electron Energy Loss Spectroscopy (EELS), and Energy Dispersive Spectroscopy (EDS). And finally a model describing the reaction mechanism and diffusion processes involved in the reaction will complete the research. Experiments using Secondary Ion Mass Spectroscopy (SIMS) aide in determining the chemical gradients of the reaction layer that will be used in the model. The goal of the research is to provide a comprehensive analysis of the olivine carbonation reaction layer to aide in the development of designing an economically viable process for the mineral sequestration of carbon dioxide.

Nunez, Ryan

290

Fe Mg diffusion in olivine II: point defect chemistry, change of diffusion mechanisms and a model for calculation of diffusion coefficients in natural olivine  

NASA Astrophysics Data System (ADS)

Analysis of existing data and models on point defects in pure (Fe,Mg)-olivine (Phys Chem Miner 10:27 37,1983; Phys Chem Miner 29:680 694, 2002) shows that it is necessary to consider thermodynamic non-ideality of mixing to adequately describe the concentration of point defects over the range of measurement. In spite of different sources of uncertainties, the concentrations of vacancies in octahedral sites in (Fe,Mg)-olivine are on the order of 10-4 per atomic formula unit at 1,000 1,200 C according to both the studies. We provide the first explicit plots of vacancy concentrations in olivine as a function of temperature and oxygen fugacity according to the two models. It is found that in contrast to absolute concentrations at 1,100 C and dependence on fO2, there is considerable uncertainty in our knowledge of temperature dependence of vacancy concentrations. This needs to be considered in discussing the transport properties such as diffusion coefficients. Moreover, these defect models in pure (Fe,Mg)-olivine need to be extended by considering aliovalent impurities such as Al, Cr to describe the behavior of natural olivine. We have developed such a formulation, and used it to analyze the considerable database of diffusion coefficients in olivine from Dohmen et al. (Phys Chem Miner this volume, 2007) (Part - I) and older data in the literature. The analysis documents unequivocally for the first time a change of diffusion mechanism in a silicate mineralfrom the transition metal extrinsic (TaMED) to the purely extrinsic (PED) domain, at fO2 below 10-10 Pa, and consequently, temperatures below 900 C. The change of diffusion mechanism manifests itself in a change in fO2 dependence of diffusivity and a slight change in activation energy of diffusionthe activation energy increases at lower temperatures. These are consistent with the predictions of Chakraborty (J Geophys Res 102(B6):12317 12331, 1997). Defect formation enthalpies in the TaMED regime (distinct from intrinsic defect formation) lie between -66 and + 15 kJ/mol and migration energies of octahedral cations in olivine are most likely 260 kJ/mol, consistent with previous inferences (Phys Chem 207:147 162, 1998). Plots are shown for diffusion at various constant fO2 as well as along fO2 buffers, to highlight the difference in behavior between the two. Considering all the diffusion data and constraints from the point defect models, (Fe Mg) diffusion in olivine along [001] is best described by the Master equations: (1) At oxygen fugacities greater than 10-10 Pa: log [D_{{{FeMg}}} (m2/s)] = - 9.21 - {201000 + (P - 105) 7 10^{{- 6}}}/{2.303RT} + 1/6log (fO2 /10^{{- 7}}) + 3X_{{{Fe}}} where T is in Kelvin, P and fO2 is in Pascals, X Fe is the mole fraction of the fayalite component and R is the gas constant in J/mol/K. (2) At oxygen fugacities less than 10-10 Pa: log [D_{{{FeMg}}} (m2/s)] = - 8.91 - {220000 + (P - 105) 7 10^{{- 6}}}/{2.303RT} + 3X_{{{Fe}}} These equations reproduce all of the 113 experimental data points within half an order of magnitude. (3) Alternately, a global equation averaging out the change of mechanism may be used, with somewhat larger errors in reproducing the measured diffusion data. It underestimates data at higher temperatures, and overestimates them at lower temperatures on the average. Note that fO2 is not explicitly considered here, leading to additional sources of error: log [D_{{{FeMg}}} (m2/s)] = - 8.27 - {226000 + (P - 105) 7 10^{{- 6}}}/{2.303RT} + 3X_{{{Fe}}} To obtain diffusion coefficients along [100] and [010], log 6 needs to be subtracted from each of the above equations.

Dohmen, Ralf; Chakraborty, Sumit

2007-08-01

291

Unusual spin fluctuations and magnetic frustration in olivine and non-olivine LiCoPO4 detected by P31 and Li7 nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

We report P31 and Li7 nuclear magnetic resonance (NMR) studies in new non-olivine LiZnPO4-type LiCoPO4tetra microcrystals, where the Co2+ ions are tetrahedrally coordinated. Olivine LiCoPO4, which was directly transformed from LiCoPO4tetra by an annealing process, was also studied and compared. The uniform bulk magnetic susceptibility and the P31 Knight shift obey the Curie-Weiss law for both materials with a high spin Co2+ (3d7, S =3/2), but the Weiss temperature ? and the effective magnetic moment ?eff are considerably smaller in LiCoPO4tetra. The spin-lattice relaxation rate T1-1 reveals a quite different nature of the spin dynamics in the paramagnetic state of both materials. Our NMR results imply that strong geometrical spin frustration occurs in tetrahedrally coordinated LiCoPO4, which may lead to the incommensurate magnetic ordering.

Baek, S.-H.; Klingeler, R.; Neef, C.; Koo, C.; Bchner, B.; Grafe, H.-J.

2014-04-01

292

Phospho-olivines as cathode materials for lithium ion battery: trends on microwave synthesis  

NASA Astrophysics Data System (ADS)

In recently years, scientific research has been focused on finding new sources of efficient energy storage and lithium batteries are one of the most outstanding alternatives. Nowadays, investigation on cathode materials constitute one of the key factors of lithium rechargeable batteries studies. Recently, oxides with olivine structures has triggered the battery field, due to its excellent electrochemical properties, crystal stability, energy density, power capacity and are not expensive. However, the demand and development of more enhanced cathode materials can be achieved by the use of sophisticated synthetic methods. The purpose of this article is to provide a perspective to the materials community on the opportunities and limitations of nanostructured materials by highlighting examples in synthesis, fundamental studies and applications on microwave synthesis as novel route to obtain high voltage phospho-olivines.

Alarcn-Suesca, C. E.; Nilges, T.

2014-04-01

293

Diffusion of Li in Olivine: Complex Behavior Arising From Effects of Li Concentration and Defect Chemistry  

NASA Astrophysics Data System (ADS)

An increasing number of studies are using Li-concentration and Li-isotope systematics to address various geochemical and cosmochemical questions. Large variations are observed [e.g. 1-3] but the origins of the fractionation (e.g. deep and old versus shallow and recent) are debated. Notably, in contrast to the behavior of heavier elements, significant kinetic fractionation e.g. during diffusion, is observed for Li [4]. To contribute to this discussion we have built upon our existing dataset of experimental Li diffusion in olivine [5]. We have determined diffusion rates for both isotopes of Li (6Li and 7Li) along [001] in olivine single crystals at 800 to 1200 C, 1 atmosphere total pressure and fO2 ~ WM buffer. It was found [5] that (i) diffusion of Li is fast compared to diffusion rates of Fe-Mg and other cations, (ii) diffusion of Li occurs simultaneously by two mechanisms whereby Li occupies vacant metal sites as well as interstitial sites, with dynamic exchange between these. Our further studies show, however, that the diffusion rates depend dramatically on the concentration of Li in olivine as well as the concentration of available point defects (e.g. vacancies). To account for this dependence we have extended our model and explicitly considered charge balance during incorporation and diffusion of Li in olivine based on a quantitative point defect model [6]. The observed concentration profiles of Li as well as its isotopes are well described by the model. Our main conclusions are: (i) 6Li diffuses about 4-6 % faster than 7Li on the interstitial site, (ii) to model homogenization timescales in natural systems, it is necessary to consider the full coupling between point defect concentrations (as functions of parameters such as fO2, fH2O) and Li concentration, as embodied in the model, and (iii) for concentrations of Li typically found in natural olivines (~ few ppm), the faster, interstitial diffusion mechanism is effectively absent and the modeling may be simplified. In these cases, Li diffusion rates are about an order of magnitude faster than rates of Fe-Mg diffusion in olivine; in special circumstances these two rates may even be similar. Under conditions that promote high concentrations of Li interstitials in olivine (e.g. presence of a Li rich fluid), isotopic equilibration of Li will proceed much faster than the rate at which Li concentrations equilibrate, but this need not always be the case in nature. Finally, Li diffusion rates in olivine are surprisingly slow in comparison to the rates in other minerals such as plagioclase [7] and clinopyroxene [8]. References [1] Tomascak PB (2004) Rev Miner Geochem, 55, 153-195. [2] Rudnick RL, Ionov DA (2007) Earth Planet Sci Lett, 256, 278-293. [3] Barrat JA, Chaussidon M, Bohn M, Gillet Ph, Gpel C, Lesourd M (2005) Geochim Cosmochim Acta, 69, 5597-5609. [4] Richter FM, Dauphasa N, and Teng F-Z (2008) Chem Geol, doi:10.1016/j.chemgeo.2008.06.011. [5] Dohmen R, Kasemann S, Coogan L, Chakraborty S, Fall AGU 2007 [6] Dohmen R, Chakraborty S (2007) Phys Chem Mineral, 34, 409-430. [7] Giletti BJ, Shanahan TM (1997) Chem Geol, 139, 3-20. [8] Coogan LA, Kasemann SA, Chakraborty S (2005) Earth Planet Sci Lett, 240, 415-424.

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

2008-12-01

294

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.; Grn, E.; Srama, R.

2014-08-01

295

Petrogenetic significance of minor elements in olivines from diamonds and peridotite xenoliths from kimberlites of Yakutia  

NASA Astrophysics Data System (ADS)

Peridotite xenoliths and diamonds from kimberlites represent an important source of information about the composition of the continental lithosphere at depths exceeding 120-150 km. Ultramafic (or peridotitic) U(P)-type of geological environment is dominating at these depths compared to eclogitic (E-type). Olivine is the most typical mineral both of peridotite xenoliths and as diamond inclusions in most kimberlites worldwide. In spite of its simple chemical composition it contains a number of petrogenetically significant minor elements such as Ti, Al, Mn, Ca, Cr, Ni, Co in low concentrations, mostly below 0.1 wt.% of oxide except of NiO. More than 500 industrial quality diamonds of size range between 0.8 and 3 mm containing olivine inclusions sometimes associated with enstatite, pyrope, chrome diopside and chromite were selected from current diamond production of nine major Siberian diamond mines. This collection also includes revised olivine diamond inclusions from Arkhangelsk (Russia), Majhgawan (India) diamond mines and Urals (Russia) alluvial mines. More than 30% of studied samples were prepared for analysis of olivines on a single polished surface with diamond. More than 300 peridotite xenoliths were selected for olivine studies from a representative collection from unaltered kimberlites of Udachnaya diamond mine. These xenoliths include low-temperature coarse lherzolites, harzburgites and dunites which are represented by spinel, garnet-spinel and garnet varieties. More than 70 xenoliths of high-temperature porphyroclastic (sheared) lherzolites from Udachnaya are also included in the examined collection. Olivines were analyzed for major and minor elements with a JEOL JXA 8200 electron microprobe at the Max-Planck Institute of Chemistry, Mainz. Special efforts were made to obtain high precision and accuracy in electron microprobe analyses, especially, for Ti, Al, Ni, Co, Ca, Mn and Cr. These elements were analyzed by using long counting time and high beam current yielding detection limits of around 10-15 ppm and errors of 20-30 ppm (2 standard errors). Minor element abundance of the overwhelming majority of studied forsteritic (Fo) olivines with Fo [100 Mg/(Mg + Fe)] between 91 and 94 varies within the following ranges in wt.% (NiO 0.310-0.420; CaO 0.005-0.045; MnO 0.070-0.131; Cr 2O 3 0.012-0.117; CoO 0.008-0.022; Al 2O 3 0.007- 0.039; TiO 2 0.005-0.042). It is concluded that all examined olivines share similar compositional features and are formed at high pressures. A significant positive correlation of Fe and Mn was observed as well as a trend to positive correlation of Cr and Al for a number of samples due to a possible dependence on T values and Cr/Al in bulk peridotites and a trend to positive correlation of Ca and Al due to the effect of temperature.

Sobolev, N. V.; Logvinova, A. M.; Zedgenizov, D. A.; Pokhilenko, N. P.; Malygina, E. V.; Kuzmin, D. V.; Sobolev, A. V.

2009-11-01

296

Olivine clasts from mesosiderites and howardites - Clues to the nature of achondritic parent bodies  

NASA Technical Reports Server (NTRS)

The compositional ranges of olivine clasts from mesosiderites and most clasts from howardites (FO90-55 and FO89-45 respectively) overlap. Only one clast in howardite Allan Hills A78006,9 (FO16) differs significantly. Differences in FeO/MnO in olivines from the two groups may be explained by different redox states of their source regions. Whether the two meteorite groups were derived from the same parent body is not clear, but the lack of Fe-rich eucritic clasts in mesosiderites together with the lack of tridymite-phosphate rich gabbros and basalts in howardites, suggests that different bodies are required since both meteorite groups are near-surface polymict breccias, which have probably sampled significant portions of their parent body surfaces.

Delaney, J. S.; Prinz, M.; Nehru, C. E.

1980-01-01

297

Crystal size distribution of olivine porphyrocrysts from the M?cinka Basalt (SW Poland)  

NASA Astrophysics Data System (ADS)

The occurrence of basalt in M?cinka (near Jawor) belongs to the Lower Silesian part of the Tertiary Central European Volcanic Province, extending from the Eifel Mts. in Germany through the Czech Republic to Lower Silesia. Volcanic activity began at the turn of the Eocene and Oligocene and lasted up to early Miocene. Here, we present data on chemical composition of basalt from M?cinka, chemical composition of individual minerals and crystal size distribution of olivine phenocrysts. Crystal size distribution (CSD) of olivine porphyrocrysts from volcanic rocks can be used to reconstruct rates of magma crystalization. They provide insight into the variations in nucleation and growth rates with time. Large crystals can give us information on crystallization before eruption, and small crystal give us information on crystallization after eruption. Here, we compare the information from mineral chemistry with that from CSD to reconstruct stages of basaltic magma crystallization. The M?cinka basalt is exposed in a quarry and forms two lava flows, overlain and interbedded by tuffs. Tertiary sedimentary rocks, lying on the Paleozoic metamorphic schists, occur below the lower lava flow. The thickness of the flows reaches maximum of 100 m. The rock is strongly cracked, in some places the cracks are irregular and wavy, and in some, they are regular and form columnar jointing. According to TAS, two types of basaltoids occur, i.e., basalt and basanite. In both types olivine, and rarely clinopyroxene, occur as phenocrysts and the matrix consists of plagioclase, Al - diopside, Ti magnetite/ilmenite, nepheline and glass.. The olivine is characterized by variable degrees of alteration. The major differences between basalt and basanite are observed in composition of olivine phenocrysts. In basalt two types of olivine phenocrysts occur. The first type typically contains 74 % Fo in cores to 68 % in margins. The second type contains 80 % Fo in cores to 75 % in margins. Olivine porphyrocrysts from basanite rocks typically contain 85 % Fo in cores to 80 % in margins. Pyroxene porphyrocrysts from both groups have similar Mg/(Mg+Fe) ratios from 85% (core) - 71 % (rim). Composition of matrix minerals is also similar between basalt and basanite. Plagioclase is zoned, contains up to 70 % of anorthite in cores and from 16 to 58 % in margins. Pyroxenes have the composition of Al-rich diopside, Mg/(Mg+Fe) varies from 68 % to 80 %. We measured sizes of olivine crystals in thin sections and plotted them against population densities. Two types of patterns with different slopes are seen for the rocks from M?cinka. Basalt is characterized by 0,10 - 0,16 values of G (growth rates) multiply t (crystalization time) for small crystals, and 0,20 - 0,28 for large crystals. On the other hand, basanite is characterized by 0,08 - 0,11 values for small crystals and 0,18 - 0,21 for large crystals. Difference in Gt values for large crystals is significant between basalt and basanite. It is consistent with long residence times and slow crystallization of the largest phenocrysts. Values of Gt for small crystals do not vary so much between basalt and basanite and probably reflect slightly different cooling rates after eruption. Both groups probably represent different stages of eruption or different lava flows.

Ja?wa, Aleksandra; Pietranik, Anna

2010-05-01

298

Alkali Olivine Basalt dredged near St. Paul's Rocks, Mid-Atlantic Ridge  

Microsoft Academic Search

RECENT studies of deep sea basalts have revealed the great predominance of olivine tholeiites over both normative nepheline and normative quartz basalts1. An alkali basalt recently dredged between 2,950 and 1,975 m near St. Peter and St. Paul Rocks (St. Paul's Rocks) consequently seemed worthy of prompt description. Although mentioned in an abstract2, we have not previously published a chemical

William G. Melson; Eugene Jarosewich; Richard Cifelli; GEOFFREY THOMPSON

1967-01-01

299

Dynamic recrystallization of olivine single crystals during high-temperature creep  

Microsoft Academic Search

High-temperature creep experiments were made on olivine single crystals under compressional stress to large strains. At strains larger than about 40 to 60%, dynamic recrystllization occurs and cellular wall dislocation structure is formed. Recrystallized grain size dg(mum) and cell wall spacing ds(mum) are dependent upon applied stress sigma(MPa) as: dg?(times)=103sigma1.18+\\/-0.11 and ds?(times)=102sigma-0.67+\\/-0.10.

Shun-ichiro Karato; Mitsuhiro Toriumi; Toshitsugu Fujii

1980-01-01

300

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: FumarolesMarsOlivineAcidophileGeothermalSearch for life (biosignatures)Synchrotron X-ray diffraction. Astrobiology 13, 10491064. PMID:24283927

Tschauner, Oliver

2013-01-01

301

Experimental Investigation of the Dissolution and Alteration of Olivine at Low Temperatures and Pressures  

Microsoft Academic Search

We have determined the surface characteristics of single crystals of olivine that have been altered under a variety of experimental conditions relevant to processes occurring on the Martian surface and in shallow crustal environments (i.e. mid-ocean ridge systems and hydrothermal environments). Most previous experiments have focused on dissolution rates of mineral powders at near-surface conditions of temperature (25 C), pressure

M. T. Deangelis; T. C. Labotka; D. R. Cole

2007-01-01

302

Oxygen isotope heterogeneity of the mantle beneath the Canary Islands: insights from olivine phenocrysts  

Microsoft Academic Search

A relatively narrow range of oxygen isotopic ratios (?\\u000a 18O=5.05.4) is preserved in olivine of mantle xenoliths, mid-ocean ridge (MORB), and most ocean island basalts (OIB). The\\u000a values in excess of this range are generally attributed either to the presence of a recycled component in the Earths mantle\\u000a or to shallow level contamination processes. A viable way forward to trace

Andrey A. GurenkoIlya; Ilya N. Bindeman; Marc Chaussidon

2011-01-01

303

Petrogenetic significance of minor elements in olivines from diamonds and peridotite xenoliths from kimberlites of Yakutia  

Microsoft Academic Search

Peridotite xenoliths and diamonds from kimberlites represent an important source of information about the composition of the continental lithosphere at depths exceeding 120150km. Ultramafic (or peridotitic) U(P)-type of geological environment is dominating at these depths compared to eclogitic (E-type). Olivine is the most typical mineral both of peridotite xenoliths and as diamond inclusions in most kimberlites worldwide. In spite of

N. V. Sobolev; A. M. Logvinova; D. A. Zedgenizov; N. P. Pokhilenko; E. V. Malygina; D. V. Kuzmin; A. V. Sobolev

2009-01-01

304

Olivine-spinel equilibria in lherzolite xenoliths from San Quintin, Baja California  

Microsoft Academic Search

Partitioning of Mg-Fe2+ between coexisting olivine and spinel is examined in sixty-eight lherzolite xenoliths that range from relatively undeformed rocks through intermediate varieties to extremely deformed and recrystallized tectonites. The partitioning data is plotted in a two-dimensional diagram whose axes represent (ln KD - 4 YFe3+SP) and YCrSP. The different textural types can be distinguished from each other with

Asish R. Basu

1977-01-01

305

Petrogenesis of Parental and Evolved Olivine Tholeiite Magmas, Eastern Snake River Plain, Idaho  

Microsoft Academic Search

Geochemical variations in over 500 whole-rock corehole and surface samples representing ~40 individual eruptions of olivine tholeiites on the eastern Snake River Plain (ESRP) portray a system with two major mechanisms of petrogenesis and possibly several magmatic sources in the mantle. Parental liquids, those with high MgO and low incompatible elements (MgO ~7.5-11.2 wt. %; La ~7-19 ppm; Ba ~100-290

S. S. Hughes; D. J. Geist; M. McCurry

2006-01-01

306

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

307

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

308

Primitive olivine-phyric shergottite NWA 5789: Petrography, mineral chemistry, and cooling history imply a magma similar to Yamato-980459  

E-print Network

began to crystallize at a high pressure consistent with conditions in Mars' lower crust/upper mantle rock and olivine core Mg#s 3 (=molar Mg/[Mg + Fe]) suggests that they could represent primitive melts

Treiman, Allan H.

309

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

310

Trace elements of olivine in silicate inclusions of IAB iron meteorites reflecting low-temperature history  

NASA Astrophysics Data System (ADS)

IAB iron meteorites with silicate inclusions may have formed at the core-mantle boundary of planetary bodies. Important constraints on the thermal evolution and the size of these bodies are given by cooling rates obtained from these meteorites. Recent metallographic cooling rates determined in metal grains enclosed in silicates of IAB irons are between 30 and 70 C/m.y. An independent method for obtaining cooling rates of IAB silicates inclusions was suggested by Kohler (1991). The Ca contents of olivines are zoned from core to rim reflecting cooling from about 650 to 500 C, at similar temperatures as kamacite-taenite exsolution occurs. Calcium zoning of ol was observed in Landes, Caddo County, Woodbine, and Persimmon Creek (recent ion microprobe data). In addition, the central Ca content of olivine grains of different IAB meteorites should also reflect cooling rates. Olivine core compositions in silicates of several IAB meteorites, e.g., Persimmon Creek (PC), El Taco (ET), Woodbine (WB), Landes (LA), Caddo County (CC), and Copiapo (COP) were determined with the electron microprobe. Results of the electron microporbe study are discussed. The use of Ca core contents and Ca profiles as indicators of low-temperature cooling rates requires further work. Nickel in ol may provide additional constraints on the thermal histories.

Zipfel, J.; Weinbruch, S.; Specht, S.; Palme, H.

1994-07-01

311

Helium solubility in olivine and implications for high 3He/4He in ocean island basalts.  

PubMed

High 3He/4He ratios found in ocean island basalts are the main evidence for the existence of an undegassed mantle reservoir. However, models of helium isotope evolution depend critically on the chemical behaviour of helium during mantle melting. It is generally assumed that helium is strongly enriched in mantle melts relative to uranium and thorium, yet estimates of helium partitioning in mantle minerals have produced conflicting results. Here we present experimental measurements of helium solubility in olivine at atmospheric pressure. Natural and synthetic olivines were equilibrated with a 50% helium atmosphere and analysed by crushing in vacuo followed by melting, and yield a minimum olivine-melt partition coefficient of 0.0025 +/- 0.0005 (s.d.) and a maximum of 0.0060 +/- 0.0007 (s.d.). The results indicate that helium might be more compatible than uranium and thorium during mantle melting and that high 3He/4He ratios can be preserved in depleted residues of melting. A depleted source for high 3He/4He ocean island basalts would resolve the apparent discrepancy in the relative helium concentrations of ocean island and mid-ocean-ridge basalts. PMID:16237441

Parman, Stephen W; Kurz, Mark D; Hart, Stanley R; Grove, Timothy L

2005-10-20

312

The effect of dynamic recrystallization on olivine fabric and seismic anisotropy: Insight from a ductile shear zone, Oman ophiolite  

Microsoft Academic Search

Subhorizontal mantle structures subparallel to the Moho are rotated into NWSE subvertical orientations across a shear zone in a sinistral sense of shear within the northern Fizh mantle section of the Oman ophiolite. Dynamic recrystallization resulted in grain size reduction of olivine and the development of porphyroclastic texture. Mean olivine grain size stabilized at ?0.7mm within the shear zone center;

Katsuyoshi Michibayashi; Toshiki Ina; Kyuichi Kanagawa

2006-01-01

313

Laboratory Simulation of Space Weathering: ESR Measurements of Nanophase Metallic Iron in Laser-irradiated Olivine and Pyroxene Samples  

NASA Technical Reports Server (NTRS)

S-type asteroids are believed to be parent bodies of ordinary chondrites. Although both S-type asteroids and ordinary chondrites contain the same mineral assemblage, mainly olivine and pyroxene, the reflectance spectra of the asteroids exhibit more overall depletion (darkening) and reddening, and more weakening of absorption bands relative to the meteorites. This spectral mismatch is explained by space weathering process, where high-velocity dust particle impacts should change the optical properties of the uppermost regolith surface of asteroids. In order to simulate the space weathering, we irradiated nanosecond pulse laser beam onto pellet samples of olivine (8.97wt% FeO) and pyroxene (enstatite: 9.88wt% FeO, hypersthene: 16.70wt%). We got spectral changes in our samples similar to that by space weathering on asteroids and confirmed nanophase alpha-metallic iron particles, which were theoretically predicted, not only on olivine but also on pyroxene samples by Transmission Electron Microscopy (TEM). Nanophase metallic iron particles were widely scattered throughout the amorphous rims developed along the olivine grains, whereas they were embedded in aggregates of amorphous in enstatite samples. Recently, we also measured laser-irradiated samples by ESR (Electron Spin Resonance). Strong ESR signals, characteristic to nanophase iron particles, are observed on irradiated olivine samples. In this paper, we report the quantities of nanophase metallic iron particles in pyroxene samples by ESR observations in addition to olivine samples.

Kurahashi, E.; Yamanaka, C.; Nakamura, K.; Sasaki, S.

2003-01-01

314

Li Isotopes Variability In St. Vincent Melt Inclusions And Olivines: Distinction Between Diffusion And Magmatic Processes  

NASA Astrophysics Data System (ADS)

St. Vincent Island is located in the Lesser Antilles arc, generated by the subduction of the Atlantic plate beneath the Caribbean plate. Melt inclusions (MI) trapped in high Fo olivines from basaltic scoriae from this island have previously been characterized in major, volatile and trace elements and stable isotopes (Bouvier et al., 2008, 2010). They have been suggested to represent primary magmas and to record the influence of at least 3 different slab fluids. Their ?7Li display a large range (-10 to +7%), without clear correlation with other elements. Because of the fast Li diffusion rate, the Li isotopic variations could reflect isotopic fractionation by Li diffusion in or out of the MI, or the influence of a slab fluid with specific ?7Li signature. In order to understand the large ?7Li variability in MI, profiles of ?7Li have been performed in host olivines, using ion probes CAMECA IMS 1280. The selected olivines display chemical zoning, with thin rims (< 50?m) having lower Fo contents than cores. Their [Li] averages vary from 1.4 to 2.4 ppm. ?7Li have been corrected from matrix effects due to Fo variations. Both intra- and inter-grain ?7Li variabilities are larger than analytical error (2.7%, 2SD): within a crystal, ?7Li could vary by up to 15% (2SD), and from grain to grain, average ?7Li range from -6 to +3%, lower than mantle values. Li isotopes in rims are strongly fractionated (down to -13%) and associated with higher [Li] (>2 ppm). In cores, ?7Li range from -4 to +7%, as most of the MI. To distinguish diffusion from magmatic processes, these data are combined with ?18O, diffusing slowly. Intracrystalline ?18O variations can reach up to 0.8% (2SD), higher than analytical error (0.3%, 2SD), without systematic rim zoning. Average ?18O per grain vary from 5.0 to 5.8%, a range comparable but larger than previously published bulk ?18O for St. Vincent olivines (Van Soest et al., 2002). These values positively correlate with average ?7Li in cores. The Li fractionation in rims could be due to Li diffusion during cooling or to Li ingress into the rim from a Li-richer melt during magmatic transportation, whereas in cores, the correlation between ?7Li and ?18O and similarities between ?7Li in olivines cores and MI suggest that ?7Li in cores are not or only poorly affected by Li diffusion. Li isotopic variability in both MI and olivines thus reflect magmatic processes, as slab fluids inputs in the mantle source. Li isotopes could have been fractionated during non-equilibrium fluid extraction from the slab and/or during fluids migration within the mantle before MI trapping. Thus in situ analysis of ?7Li in MI and their host olivines from fast quenched samples as scoriae could be a valuable tool to understand the behavior of Li isotopes during deep magmatic processes.

Bouvier, A.

2011-12-01

315

The Standard Hydrous Olivine (SHO) conductivity model: A new tool for probing water in the upper mantle  

NASA Astrophysics Data System (ADS)

It has long been assumed that the incorporation of water in olivine has dramatic effects on the physical properties of the mantle, affecting large scale geodynamic processesand triggering most electrical conductivity anomalies in the mantle. But the conductivity models for hydrous olivine based on experimental measurements predict contrasting effects of water (e.g. Wang et al. 2006; Yoshino et al. 2009), precluding any unequivocal interpretation of electrical conductivities in the mantle. Our thesis is that the uncertainties and biases in the water contents of the olivines used for experiments were inappropriately appreciated, resulting in apparent incompatibilities when analysing the different datasets and in significant biases in the models outside of their range of calibration. Here, we analyse all published experimental work and provide a new model, SHO, that settles these major inconstancies. SHO is calibrated on the largest database of raw conductivity measurements on oriented single crystals and polycrystals of hydrous olivine, with water concentrations and temperatures spreading over 0-2220 wt. ppm and 200-1440 C. Our model provides both oriented conductivities, allowing for calculating conductivity anisotropy, and isotropic conductivity, relevant for olivine aggregates without preferential orientation. SHO isotropic conductivity (S/m) is given by 2.93 - 157000 -1.54 - 87000-1820C1/H32O ? = 10 e RT + 10 CH2Oe RT , where CH2O is the water concentration in olivine (wt. ppm), T the temperature (K) and R = 8.314 J/K/mol. In the normally hot mantle, our model predicts a moderate effect of water on the conductivity of olivine. High conductivities (~ 0.1 S/m) are obtained at great depths and elevated water concentrations only (> 350 km and > 400 wt. ppm). The strongest effects are therefore expected in the coldest regions of the mantle, like cratonic lithospheres or subduction zones, where higher incorporation of water in olivine is allowed. Wang, D., Mookherjee, M., Xu, Y., Karato, S. The effect of water on the electrical conductivity of olivine. Nature 443, 977-980 (2006) Yoshino, T., Matsuzaki, T., Shatskiy, A., Katsura, T. The effect of water on the electrical conductivity of olivine aggregates and its implications for the electrical structure of the upper mantle. Earth Planet. Sc. Lett. 288, 291-300 (2009)

Gards, Emmanuel; Gaillard, Fabrice; Tarits, Pascal

2014-05-01

316

Petrography, mineral chemistry, and crystallization history of olivine-phyric shergottite NWA 6234: A new melt composition  

NASA Astrophysics Data System (ADS)

Knowledge of Martian igneous and mantle compositions is crucial for understanding Mars' mantle evolution, including early differentiation, mantle convection, and the chemical alteration at the surface. Primitive magmas provide the most direct information about their mantle source regions, but most Martian meteorites either contain cumulate olivine or crystallized from fractionated melts. The new Martian meteorite Northwest Africa (NWA) 6234 is an olivine-phyric shergottite. Its most magnesian olivine cores (Fo78) are in Mg-Fe equilibrium with a magma of the bulk rock composition, suggesting that it represents a melt composition. Thermochemical calculations show that NWA 6234 not only represents a melt composition but is a primitive melt derived from an approximately Fo80 mantle. Thus, NWA 6234 is similar to NWA 5789 and Y 980459 in the sense that all three are olivine-phyric shergottites and represent primitive magma compositions. However, NWA 6234 is of special significance because it represents the first olivine-phyric shergottite from a primitive ferroan magma. On the basis of Al/Ti ratio of pyroxenes in NWA 6234, the minor components in olivine and merrillite, and phosphorus zoning of olivine, we infer that the rock crystallized completely at pressures consistent with conditions in Mars' upper crust. The textural intergrowths of the two phosphates (merrillite and apatite) indicate that at a very last stage of crystallization, merrillite reacted with an OH-Cl-F-rich melt to form apatite. As this meteorite crystallized completely at depth and never erupted, it is likely that its apatite compositions represent snapshots of the volatile ratios of the source region without being affected by degassing processes, which contain high OH-F content.

Gross, Juliane; Filiberto, Justin; Herd, Christopher D. K.; Daswani, Mohit Melwani; Schwenzer, Susanne P.; Treiman, Allan H.

2013-05-01

317

High temperature a.c. electrical properties of olivine single crystal with varying oxygen partial pressure: implications for the point defect chemistry  

Microsoft Academic Search

The electrical conductivity and dielectric constant of a natural olivine single crystal were measured as a function of frequency over 0.1-1000 Hz. The measurements were made at temperatures of 1000-1400C under a controlled oxygen partial pressure that was varied within the range of the olivine stability field. The observed dielectric constant of olivine increased with increasing oxygen pressure, and the

Hiroki Sato

1986-01-01

318

Wet, dry, Dopants and Defects - an Integrated View of Diffusion in Olivine as a Prototypical Silicate  

NASA Astrophysics Data System (ADS)

Knowledge of diffusion coefficients of different species in minerals is a necessary pre-requisite for understanding and modeling the compositional evolution of rocks. Their use to determine time scales of various geological processes, to understand the reaction mechanisms and rheological behavior of rocks and minerals, and to evaluate the significance of dates and temperatures obtained from geochronometers and geothermometers, is becoming routine. However, many aspects of diffusion behavior of minerals remain enigmatic. Two of these are: (1) Do the presence of small amounts of impurities ("dopants") affect diffusion rates, and if yes, how? (2) Water is known to enhance transport rates, but exactly at what conditions and how does the wet to dry transition occur? Can it be predicted? These questions can be approached by developing an appropriate description of the diffusion process in terms of point defect thermodynamics. The large body of systematic diffusion data and natural observations in olivine makes it the mineral of choice to explore this avenue. Diffusion coefficients for various cations as well as O are known typically as a function of temperature, and often as a function of other variables such as pressure, oxygen fugacity or water fugacity. We developed a quantitative point defect model that allows the role of trace elements (i.e. dopants in the terminology of material science) in controlling transport properties to be quantified [1]. In addition we explored the nature of wet to dry transition of these transport properties in olivine [2]. We have now combined these approaches to develop an integrated scheme for describing point defect chemistry and transport properties of olivine containing arbitrary trace elements, in the presence or absence of water. The approach is perfectly general and can be extended to any other mineral provided enough data are available. Oxygen fugacity is known to affect transport rates of Fe-bearing silicates but the extent of this influence depends on T and fO2. At low T (e.g., < 1000 C) a transition to a new diffusion mechanism, independent of fO2, occurs in impurity bearing natural olivines due to the presence of Al3+ and Cr3+ (Dohmen and Chakraborty, 2007). An extension of this model allows us to treat the role of water and the wet to dry transition in an exactly analogous, and self consistent, manner. The dependence of diffusion rates on fO2, fH2O and concentrations of various trace elements can be obtained without needing to empirically determine the critical fH2O at which the "wet" to "dry" transition occurs for each kinetic / transport property. We find that the transition occurs over a significant range of pressure and over this interval the kinetic behavior is transitional between wet and dry. We also find that although dopants play a key role in defining the transport properties of various semiconductors, in natural materials such as olivine their influence is limited because simultaneous incorporation of multiple trace elements of different ionic charges largely offset the effects of each other. We are left with Fe3+ (via oxygen fugacity) and H as the two key "impurities" that can commonly and significantly affect transport rates in olivines; their influence can now be calculated and predicted quantitatively. [1] Dohmen R, Chakraborty S (2007) Phys Chem Mineral, 34, 409-430. [2] Costa F, Chakraborty S (2008) Phys Earth Planet Int, 166, 11-29.

Dohmen, R.; Costa, F.; Chakraborty, S.

2008-12-01

319

An experimental study of Li partitioning between olivine and diopside at mantle conditions  

NASA Astrophysics Data System (ADS)

Measured 7Li/6Li of mineral separates from mantle xenoliths from diverse localities show unexpectedly large differences between olivines and pyroxenes, often with lighter Li found in the pyroxenes (Jeffcoate et al., 2007; Rudnick and Ionov, 2007; Ionov and Seitz, 2008). Although changes in isotopic fractionation with temperature could explain the differences, a kinetic isotope effect is as likely. Because 6Li diffuses faster than 7Li, bulk lithium exchange between two phases could result in dynamic isotopic fractionation, with the receiving phase becoming lighter and the donating phase becoming heavier. Thus if Li becomes more compatible in cpx upon cooling, that is, if DLiol/cpx is temperature-dependent, the diffusive exchange of Li will generate temporary 6Li enrichment in cpx and depletion in olivine. Experiments were conducted using a piston cylinder apparatus at 1100C and 1.4 GPa (1-5 days) to determine DLiol/cpx. San Carlos olivine and Dekalb diopside were finely ground for starting materials. A mixture of olivine (52 wt%), diopside (34 wt%), albite (7 wt%), and quartz (7 wt%) powders (0.0145 g) was loaded into a Pt capsule inside of a Ni crucible. Milli-Q water with 100 ppm Li and 500 ppm Ba (obtained through dilution of stock solutions) was added (0.1100 g) to serve as the lithium source. Lithium concentrations in olivine and diopside from experiments held for 1, 3, and 5 days were determined by laser ablation ICP-MS. Partition coefficients DLiol/cpx from runs at 3 and 5 days are, within error, the same, 1.9 (0.3). These fall in the lower portion of the range, D = 2-7, of limited previous measurements (Brenan et al., 1998b, Blundy and Dalton, 2000; Caciagli-Warman 2010). Partitioning experiments at 700 and 900C are ongoing. References Blundy, J. and Dalton, J. (2000) Experimental comparison of trace element partitioning between clinopyroxene and melt in carbonate and silicate systems, and implications for mantle metasomatism. Contrib. Mineral. Petrol. 139, 356-371. Brenan, J.M., Ryerson, F.J., Shaw, H.F. (1998b) The role of aqueous fluids in the slab-to-mantle transfer of boron, beryllium, and lithium during subduction: Experiments and models. Geochim. Cosmochim. Acta 62, 3337-3347. Caciagli-Warman, N. (2010) Experimental constraints on lithium exchange between clinopyroxene, olivine and aqueous fluids at high pressures and temperatures. Unpublished PhD thesis, University of Toronto. Ionov, D.A. and Seitz, H.M. (2008) Lithium abundances and isotopic compositions in mantle xenoliths from subduction and intra-plate settings: Mantle sources vs. eruption histories. Earth Planet. Sci. Lett. 266, 316-331. Jeffcoate, A.B., Elliot, T., Kasemann, S.A., Ionov, D., Cooper, K., Brooker, R. (2007) Li isotope fractionation in peridotites and mafic melts. Geochim. Cosmochim. Acta 71, 202-218. Rudnick, R.L. and Ionov, D.A. (2007) Lithium elemental and isotopic disequilibrium in minerals from peridotite xenoliths from far-east Russia: Product of recent melt/fluid-rock reaction, Earth Planet. Sci. Lett. 256, 278-293.

Yakob, J. L.; Feineman, M. D.; Penniston-Dorland, S. C.; Eggler, D. H.

2010-12-01

320

CO2 Geological Storage in Olivine Rich Basaltic Aquifers: New Insights From Flow-Through Experiments  

NASA Astrophysics Data System (ADS)

Injection of CO2-rich fluids into (ultra-)mafic aquifers is one of the methods envisaged for mitigation of increasing atmospheric CO2 concentrations. These rocks, rich in Mg, Fe and Ca, have a high potential to trap CO2 as carbonates minerals. However, the role of reaction-transport processes has not been investigated to predict the capacity and sustainability for CO2 storage in these highly reactive systems. We performed three percolation-reaction experiments on the ICARE-2 bench (Luquot et al., 2012) at 180C and total pressure of 12 MPa. NaHCO3 rich water (0.5 mol/L) mixed with CO2 (Pco2 = 10 MPa) were injected at an initial injection rate of 1 mL/h for exp. 1 and 2, and 0.1 mL/h for exp. 3 into sintered olivine analogues of accumulation zones in basaltic flows. The sintered samples comprise mainly olivine Fo87 (Mg1.75Fe0.24Ni0.01SiO4) with minor basalt and spinel (Mg0.57Cr1.19Ti0.03Mn0.01Fe0.66Al0.54O4). The initial porosity and permeability of samples ranges from 4 to 7 % and 30x10-18 to 400x10-18 m2 respectively. All experiments resulted in a strong permeability decrease (down to 10-18 m2) after 90 hours for exp. 1 and 2 and 55 hours for exp 3. The enrichment in several major and trace elements observed in outlet fluids indicates that dissolution of olivine (Si, Co), basalt (Al, Zr) and spinel (Cr, V) occurred, while the depleted Ca and Mg composition of outlet fluids indicates precipitation of Ca-Mg rich phases. Analyses of reacted samples indicate that all basalt grains were dissolved and the spatial distribution of etch pits on forsterite surfaces suggest the anisotropic dissolution of olivine. Ankerite and calcite is observed in pores of samples after exp. 1 and 2, and well-developed magnesite (Mg0.88Fe0.11Ca0.01CO3) and dolomite replacing dissolved olivine is found in exp.3 sample. The (001) planes of magnesite and dolomite are parallel to the (100) plane of forsterite. Downstream, no carbonates were found but the growth of relatively large (up to 5 m) Mg-Fe rich phyllosilicates plates perpendicular to (at the expense of ?) olivine surfaces was observed. The precipitation of these serpentine type minerals may explain the strong decrease in permeability during experiments. Carbonation was relatively efficient in our experiments: between 0.003g (exp.3) and 0.015 g (exp.1 & 2) of CO2 per gram of sample was trapped as carbonates. When these analyses are upscaled to the size of an injection site, they correspond to an average yield of 3.6 to 10.6 Mtons of CO2/km3/day. Our results indicate a strong control of flow rates on carbonation, and also on hydration reactions. This implies not only variations of the CO2 storage capacity of the basaltic aquifer with distance to the injection well, but also that controlling the injection rate would allow enhancing the efficiency of in situ carbonation. Luquot L., Andreani M., Gouze P., Camps P. (2012) CO2 percolation experiment through chlorite/zeolite-rich sandstone (Pretty-Hill Formation - Otway-Basin-Australia), Chemical Geology 294-295, 75-88, doi:10.1016/j.chemgeo.2011.11.018.

Peuble, S.; Godard, M.; Luquot, L.; Gibert, B.; Mainprice, D.; Martinez, I.; Gouze, P.

2012-04-01

321

D-H Interdiffusion Coefficients in Olivine: Implications for Electrical Conductivity in the Upper Mantle  

NASA Astrophysics Data System (ADS)

Knowledge about hydrogen diffusivity in mantle minerals is critical for understanding point defects and defect dominated processes such as creep and electrical conductivity. Hydrogen chemical diffusion coefficients have been used to constrain diffusivities of small polarons and Mg vacancies (Kohlstedt and Mackwell, 1998). Furthermore chemical diffusion coefficients have been used to calculate hydrogen contribution to electrical conductivity in olivine (Karato, 1990), however hydrogen self diffusion coefficients are more appropriate. In this study we use +{2}H as a traceable species of hydrogen to simulate the process of hydrogen self diffusion. Deuterium (+{2}H, sometimes referred to as D) was interdiffused into hydrogen (+{1}H) saturated, oriented, single crystal San Carlos olivine. We measured +{2}H and +{1}H profiles across samples from each of these experiments and fit interdiffusion coefficients (D_{D-H}). For olivine between 750-900 C at 2 GPa we measured D_{D-H, [100]} = 10+{(-5.0 +/- 1.4)}*e+{(-135 +/- 30 kJ/mol)/(RT)} m+{2}/s. This value is 1 order of magnitude lower than D_{Exch, [100]}, the chemical diffusion coefficient for +{1}H based redox exchange in San Carlos olivine (Kohlstedt and Mackwell, 1998). Activation energies for D_{Exch, [100]} and D_{D-H, [100]} are very similar. We measured D_{D-H, [001]} = 10+{-12.0 +/- 0.2} m+{2}/s at 900 C and 2 GPa; however only upper bound estimates for D_{D-H, [010]} and for D_{D-H, [001]} at lower temperatures could be determined with D_{D-H, [010]} D_{D-H, [001]} < 10+{-13} m+{2}/s. From comparison of D_{D-H} and D_{Exch} we calculate small polaron diffusion coefficients associated with redox exchange reactions (D_{h, [100]} = 10+{(-4.9 +/- 1.4)}*e+{(-135 +/- 30 kJ/mol)/(RT)} m+{2}/s) and confirm previous estimates of metal vacancy diffusion coefficients (D_{V(Me)} = D_{Incorp}/3). These +{2}H-+{1}H interdiffusion coefficients are used with the Nernst-Einstein relation to calculate electrical conductivity in hydrous olivine for comparison to experimental values. These calculations incorporate polaron and metal vacancy mobility estimates from anhydrous conductivity experiments. For 100 ppmw H_{2}O, 2 GPa and 900 C, the calculated electrical conductivity by hydrogen is 0.7-2.4 log units lower and activation energy is 60% higher than reported electrical conductivity measurements (Wang et al., 2006; Yoshino et al., 2006; Yoshino et al., 2009, Poe et al., 2010). Thus current estimates of defect concentrations and mobilities from diffusion experiments and measured dry and wet electrical conductivities are not mutually consistent. The calculation presented here would require unrealistically high amounts of H_{2}O to account for high electrical conductivity anomalies measured at asthenosphere depths. However, the apparent differences in activation energy suggest that multiple types of hydrogen defects/species may occur and would need to be considered in the relationship between hydrogen diffusion and conduction in olivine.

Du Frane, W. L.; Tyburczy, J. A.; Sharp, T. G.

2010-12-01

322

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

323

Comparison and calibration of nonheating paleointensity methods: A case study using dusty olivine  

NASA Astrophysics Data System (ADS)

We present a comparative study of nonheating paleointensity methods, with the aim of determining the optimum method for obtaining paleointensities from "dusty olivine" in chondritic meteorites. The REM method, whereby thermoremanent magnetization (TRM) is normalized by saturation isothermal remanent magnetization (SIRM), is shown to "over normalize" TRM in dusty olivine due to the transformation of stable single-vortex (SV) states to metastable single-domain (SD) states in a saturating field. The problem of over normalization is reduced in the REMc and REM' methods, which more effectively isolate the high-coercivity stable SD component of remanence. A calibration factor of f = 1600 (1000 < f < 2900) is derived for the REM' method. Anhysteric remanent magnetization (ARM) is shown to be a near perfect analogue of TRM in the stable SD component of dusty olivine. ARM normalization of the high-coercivity (100-150 mT) remanence with a calibration factor fARM = 0.91 (0.7 < fARM < 1.2) yields paleofield estimates within 30% of the actual field values for SD dominated samples. A Preisach method for simulating TRM acquisition using information extracted from first-order reversal curve (FORC) diagrams is shown to work well for SD dominated samples, but fails when there is a large proportion of SV remanence carriers. The failure occurs because (1) SV states are not properly incorporated into the Preisach distribution of remanence carriers, and (2) the acquisition of TRM by SV states is not properly modeled by the underlying SD thermal relaxation theory.

Lappe, Sophie-Charlotte L. L.; Harrison, Richard J.; Feinberg, Joshua M.; Muxworthy, Adrian

2013-07-01

324

Fundamentals of elasticity of (Mg1-x, Fex)2SiO4 olivine  

NASA Astrophysics Data System (ADS)

We study the influence of iron on the elasticity of (Mg1-x, Fex)2SiO4 olivine (0 ? x ? 0.125), a major constituent of the Earth's upper mantle. We calculate static elastic properties by first principles for this solid solution and investigate the effect of atomic arrangement, an artifact of supercell calculations, on all single crystal and poly-crystalline elastic moduli. From calculated wave propagation velocities we find the heterogeneity ratios of shear to compressional wave velocity, and bulk sound to shear wave velocity. Their values are, though limited to composition considerations, marginally consistent with seismic tomography.

Nez-Valdez, M.; Umemoto, K.; Wentzcovitch, R. M.

2010-07-01

325

THE DISTRIBUTION OF NICKEL AND IRON BETWEEN OLIVINE AND MAGMATIC SULFIDES IN SOME NATURAL ASSEMBLAGES  

Microsoft Academic Search

The distribution of nickel and iron between olivine and bulk sulfide has been determined in four nickel-copper- PGE (platinum-group-element) sulfide deposits. The mean distribution-coetticient 1f$iff{$!il is 5.0 + 1.7 in the Katahdin deposit (Maine), 8.3 + 3.1 in the Moxie pluton (Maine), 10.8 I 2.3 in the Dumont deposit (Quebec), and 1 1.4 t 4.8 in the Platinum Reef of

JOHN F. H. THOMPSON; STEPHEN J. BARNES

326

Mechanically Activated Olivine as Feedstock for Ex-situ Carbon Dioxide Sequestration: Preliminary Experiments  

NASA Astrophysics Data System (ADS)

Fossil fuel power plants need sequestration to significantly lower CO2 emissions. In nature, Mg- and Ca- rich silicates react with CO2(aq) and perform a natural sequestration by dissolution of silicates and a later precipitation of carbonates. This type of sequestration is environmentally friendly and stable. One severe problem with adopting this method for industrial processes is the slow reaction rate. For mineral carbonation to be an alternative, reaction rates have to be increased. Pretreatment methods involving mechanical, chemical or physical treatment can increase the rate. Resources of suitable minerals are also acquired. One abundant Mg-rich silicate mineral is olivine. Forsterite is olivine containing only Mg. An experimental study of an aqueous flow-through process was done with olivine(Fo93) reacted at 128C and 150 bars in fluid flow of 0.15 ml/min CO2 and 0.75 ml/min H2O. The total duration of the experiments varied between 19 and 71h. With a total of 2,22 mol % CO2 in the mixture, the fluid had two phases and 1,68 mol % CO2 dissolved in the H2O phase. The chosen pretreatment was mechanical activation (energy intensive milling). Influence of activation can not solely be explained by the decreased particle size. Mechanical activation also disturbs the crystal lattice, leading to amorphization. Distorted bonds in the crystal lattice due to deformation and micro fractures are also important features. The activation was done in a Fritsch mono planetary mill for 0-60 minutes, 20 grams of olivine, and 2ml DI H2O added to some samples. An observed effect was non-stochiometric dissolution in the first 20-60 minutes, with max Mg:Si = 10.5 (material molar ratio=1.86). After the initial reactions, Mg:Si stabilized near stochiometric values (1.73-1.94). Geochemical modeling of the reference material indicates subsaturation of forsterite (log Q/K ? -11), serpentine (log Q/K ? -177), and magnesite (log Q/K ? -1.4).

Haug, A.; Munz, I. A.; Kihle, J.

2006-12-01

327

Calcio-olivine ?-Ca2SiO4: I. Rietveld refinement of the crystal structure  

NASA Astrophysics Data System (ADS)

The structure of the natural mineral calcio-olivine (?-Ca2SiO4) found in skarn xenoliths in the region of the Lakargi Mountain (North Caucasus, Kabardino-Balkaria, Russia) is refined by the Rietveld method [ a = 5.07389(7) , b = 11.21128(14) , c = 6.75340(9) , V = 384.170(5) 3, Z = 4, ?calcd = 2.98 g/cm3, space group Pbnm]. The X-ray diffraction pattern of a powdered sample is recorded on a STOE STADI MP diffractometer [?Cu K ?1; Ge(111) primary monochromator; 6.00 < 2? < 100.88; step width, 2.5 in 2?; number of reflections, 224]. All calculations are performed with the WYRIET (version 3.3) software package. The structural model is refined in the anisotropic approximation to R p = 6.44, R wp = 8.52, R exp = 5.85, R B = 4.98, R F = 6.90, and s = 1.46. It is shown that the sample under investigation is a mixture of several mineral phases, among which calcio-olivine (the natural analogue of the ?-Ca2SiO4 compound) (83%), hillebrandite (13%), and wadalite (4%) are dominant. Only the scale factors and the unit cell parameters are refined for hillebrandite Ca2SiO3(OH)2 [ a = 3.63472(16) , b = 16.4140(10) , c = 11.7914(8) , space group Cmc21, Z = 6] and wadalite Ca6Al5Si2O16Cl3 ( a = 12.0088 , space group, I bar 4 3 d Z = 4). The results of the structure refinement of the main component of the sample confirm that the mineral calcio-olivine is isostructural to the synthetic compound ?-Ca2SiO4. The structure of this compound is formed by the heteropolyhedral framework composed of Ca octahedra joined together into olivine-like ribbons and isolated Si tetrahedra.

Gobechiya, E. R.; Yamnova, N. A.; Zadov, A. E.; Gazeev, V. M.

2008-05-01

328

Deuterium-Hydrogen Interdiffusion in Olivine: Implications for Point Defects and Electrical Conductivity  

NASA Astrophysics Data System (ADS)

Knowledge about hydrogen diffusivity in mantle minerals is critical for determining mantle hydrogen distribution, and additionally for understanding point defects. Chemical diffusion of hydrogen in olivine depends on self diffusion and concentration of hydrogen and other point defects, such as small polarons and metal vacancies. In this study we measured hydrogen self diffusion in olivine, and we compare these values to those previously reported for chemical 1-H redox exchange DExch. Deuterium 2-H was interdiffused into hydrogen 1-H saturated single crystals of San Carlos olivine between 750-900 C at 2 GPa. We measured and fit the resulting 2-H and 1-H profiles to obtain the interdiffusion coefficient DH,[100] = 10^(-5.04+/-1.43)*e(-137+/-31kJ/mol)/(RT) m^2/s. This is ~1 log unit lower than DExch,[100], with similar activation energy Ea,[100]. DH is anisotropic with DH,[001] = 10^(-12.0+/-0.2) m^2/s at 900 C and 2 GPa; only upper bound estimates for DH,[010] could be determined from our experiments. We use DH,[100] and DExch,[100] to calculate the small polaron diffusion coefficient associated with redox exchange Dh,[100] = 10^-3.90*e(-142kJ/mol)/(RT) m^2/s. Dh,[100] is combined with reported values for DExch,[010] and DExch,[010] to calculate values for DH,[010] and DH,[001] that are consistent with our upper bound estimates. These DH values, both measured and derived, are used with the Nernst-Einstein relation to calculate the electrical conductivity ? by hydrogen in olivine ?H. We calculate ?H = 10^1.63*e(-126kJ/mol)/(RT) S/m, which is similar in magnitude to the lower range of reported ? measurements. This similarly suggests that hydrogen alone cannot account for high ? anomalies observed at asthenospheric depths (~10^-2 to ~10^-1 S/m). The Ea for hydrogen mobility/diffusion we calculate are higher (~40% for 100 ppmw H2O) than those derived from previous ? measurements. This work supported by NSF EAR 0739050 to J. A. Tyburczy and R. Hervig. The SIMS data were obtained at the ASU National SIMS Facility, supported by NSF EAR 0622775 to R. Hervig & P.Williams. Piston cylinder experiments were conducted in the ASU OmniPressure lab. Prepared by LLNL under Contract DE-AC52-158 07NA27344.

Tyburczy, J. A.; Du Frane, W. L.

2011-12-01

329

The effect of silica activity on the diffusion of Ni and Co in olivine  

NASA Astrophysics Data System (ADS)

The diffusion of Ni and Co was measured at atmospheric pressure in synthetic monocrystalline forsterite (Mg2SiO4) from 1,200 to 1,500 C at the oxygen fugacity of air, along [100], with the activities of SiO2 and MgO defined by either forsterite + periclase (fo + per buffer) or forsterite + protoenstatite (fo + en buffer). Diffusion profiles were measured by three methods: laser-ablation inductively-coupled-plasma mass-spectrometry, nano-scale secondary ion mass spectrometry and electron microprobe, with good agreement between the methods. For both Ni and Co, the diffusion rates in protoenstatite-buffered experiments are an order of magnitude faster than in the periclase-buffered experiments at a given temperature. The diffusion coefficients D M (M = Ni or Co) for the combined data set can be fitted to the equation: with Ea(Ni) = - 284.3 kJ mol-1 and Ea(Co) = - 275.9 kJ mol-1, with an uncertainty of 10.2 kJ mol-1. This equation fits the data (24 experiments) to 0.1 in log D M. The dependence of diffusion on is in agreement with a point-defect model in which Mg-site vacancies are charge-balanced by Si interstitials. Comparative experiments with San Carlos olivine of composition Mg1.8Fe0.2SiO4 at 1,300 C give a slightly small dependence on , with D (), presumably because the Mg-site vacancies increase with incorporation of Fe3+ in the Fe-bearing olivines. However, the dependence on fO2 is small, with D ( fO2)0.120.12. These results show the necessity of constraining the chemical potentials of all the stoichiometric components of a phase when designing diffusion experiments. Similarly, the chemical potentials of the major-element components must be taken into account when applying experimental data to natural minerals to constrain the rates of geological processes. For example, the diffusion of divalent elements in olivine from low SiO2 magmas, such as kimberlites or carbonatites, will be an order of magnitude slower than in olivine from high SiO2 magmas, such as tholeiitic basalts, at equal temperatures and fO2.

Zhukova, Irina; StC O'Neill, Hugh; Cambell, Ian H.; Kilburn, Matt R.

2014-08-01

330

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 ulvspinel. 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

331

Natural examples of olivine lattice preferred orientation patterns with a flow-normal a-axis maximum.  

PubMed

Tectonic plate motion is thought to cause solid-state plastic flow within the underlying upper mantle and accordingly lead to the development of a lattice preferred orientation of the constituent olivine crystals. The mechanical anisotropy that results from such preferred orientation typically produces a direction of maximum seismic wave velocity parallel to the plate motion direction. This has been explained by the existence of an olivine preferred orientation with an 'a-axis' maximum parallel to the induced mantle flow direction. In subduction zones, however, the olivine a axes have been inferred to be arranged roughly perpendicular to plate motion, which has usually been ascribed to localized complex mantle flow patterns. Recent experimental work suggests an alternative explanation: under conditions of high water activity, a 'B-type' olivine preferred orientation may form, with the a-axis maximum perpendicular to the flow direction. Natural examples of such B-type preferred orientation are, however, almost entirely unknown. Here we document widespread B-type olivine preferred orientation patterns from a subduction-type metamorphic belt in southwest Japan and show that these patterns developed in the presence of water. Our discovery implies that mantle flow above subduction zones may be much simpler than has generally been thought. PMID:14749828

Mizukami, Tomoyuki; Wallis, Simon R; Yamamoto, Junji

2004-01-29

332

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

333

The Onset of Anelastic Behaviour in Fine-Grained Olivine at High Temperature  

NASA Astrophysics Data System (ADS)

With increasing temperature, fine-grained polycrystalline materials undergo a transition from elastic to anelastic behaviour, involving grain-boundary sliding recoverably accommodated by elastic distortion of adjacent grains - according to the classic theory of Raj and Ashby. This model, recently revisited by Morris and his colleagues, predicts shear-mode dissipation localised in temperature-period space as a 1/Q peak with height of order 0.01. Experimental data for fine-grained polycrystalline olivine are yet to provide unequivocal evidence of the expected dissipation peak and associated dispersion of the shear modulus. Accordingly, we have embarked on a new series of measurements on synthetic olivine polycrystals in which the specimens are enclosed within copper, rather than the usual steel, jackets for the forced-oscillation experiments at high temperature and pressure. In this way, we avoid the complicating effects of uncertainties in the mechanical behaviour of the jacket arising from the sluggish ferrite-austenite phase transition in mild steel. An exploratory torsional forced-oscillation experiment has already yielded a tantalising glimpse of a possible dissipation peak. The results of follow-up torsional-oscillation tests on more nearly optimal specimens, tested over a wider range of temperature, will be described. We will also report constraints on the recoverability of the inelastic strain from complementary microcreep tests, and the outcomes of exploratory flexural-oscillation measurements.

Jackson, I.; David, E.; Faul, U.

2013-12-01

334

Olivine fabric evolution in a hydrated ductile shear zone at the Moho Transition Zone, Oman Ophiolite  

NASA Astrophysics Data System (ADS)

The Fizh massif, Oman Ophiolite, contains a ductile shear zone at the Moho Transition Zone. The dunites in the shear zone are classified based on microstructures into coarse granular texture, medium-grained texture, mylonite, and ultramylonites toward a gabbro contact. The average grain size of olivine decreases toward the shear zone, which contains a zone of high strain (15 m wide). The proportion of hydrous minerals (amphibole and chlorite) in the shear zone show an increase toward the gabbro contact, suggesting that water infiltrated the shear zone from the gabbro contact. Equilibrium temperatures indicate a higher deformation temperature (900?C) outside of the high strain zone compared with inside this zone (750?C). Under these geochemical and temperature conditions, the temporal evolution of olivine crystal-preferred orientations (CPO) indicates the following continuous deformation scenario. First, deformation by dislocation creep under higher temperatures resulted in slip by D-type {0kl}[100] and then weak E-type (001)[100] slip. Next, deformation by dislocation creep under lower temperatures and higher stress conditions produced a C-type (100)[001] CPO. Finally, superplastic deformation by grain boundary sliding resulted in a random CPO.

Michibayashi, Katsuyoshi; Oohara, Tatsuya

2013-09-01

335

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

336

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

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

2006-08-01

337

A primitive dark inclusion with radiation-damaged olivine in the Ningqiang carbonaceous chondrite  

NASA Astrophysics Data System (ADS)

Ningqiang is a unique carbonaceous chondrite, with similarities to the oxidized CV3s, and includes abundant magnetite, awaruite, CAIs, fayalitic olivine and dark inclusions (DIs). It has a somewhat lower refractory lithophile-element content and a higher carbon and H2O abundance than typical CV3s. We have examined a large (5 mm) Ningqiang DI in order to assess its origin and its relationship to host Ningqiang and to DIs in CV3 and other carbonaceous chondrites. This DI indicated a more primitive nature that previously studied DIs, and provided a wider window to nebular history. The DI in Ningqiang was studied by EMPA, SEM and TEM techniques. It was cut, polished and thin-sectioned, and two chips of the DI and one of the host rock matrix were ion-milled for TEM investigation. Laboratory-derived k-values were used; most analyses are precise to within 3 percent relative, those for olivine are precise to within 1 percent relative for major elements.

Zolensky, Michael; Nakamura, Keiko; Weisberg, Michael; Prinz, Martin

1997-03-01

338

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

339

Chemical and morphological changes during olivine carbonation for CO2 storage in the presence of NaCl and NaHCO3.  

PubMed

The increasing concentrations of CO2 in the atmosphere are attributed to the rising consumption of fossil fuels for energy generation around the world. One of the most stable and environmentally benign methods of reducing atmospheric CO2 is by storing it as thermodynamically stable carbonate minerals. Olivine ((Mg,Fe)2SiO4) is an abundant mineral that reacts with CO2 to form Mg-carbonate. The carbonation of olivine can be enhanced by injecting solutions containing CO2 at high partial pressure into olivine-rich formations at high temperatures, or by performing ex situ mineral carbonation in a reactor system with temperature and pressure control. In this study, the effects of NaHCO3 and NaCl, whose roles in enhanced mineral carbonation have been debated, were investigated in detail along with the effects of temperature, CO2 partial pressure and reaction time for determining the extent of olivine carbonation and its associated chemical and morphological changes. At high temperature and high CO2 pressure conditions, more than 70% olivine carbonation was achieved in 3 hours in the presence of 0.64 M NaHCO3. In contrast, NaCl did not significantly affect olivine carbonation. As olivine was dissolved and carbonated, its pore volume, surface area and particle size were significantly changed and these changes influenced subsequent reactivity of olivine. Thus, for both long-term simulation of olivine carbonation in geologic formations and the ex situ reactor design, the morphological changes of olivine during its reaction with CO2 should be carefully considered in order to accurately estimate the CO2 storage capacity and understand the mechanisms for CO2 trapping by olivine. PMID:24469156

Gadikota, Greeshma; Matter, Juerg; Kelemen, Peter; Park, Ah-Hhyung Alissa

2014-03-14

340

Are CI Chondrites Cometary Samples? A Search for Olivine and Use as a Discrimination Index.  

NASA Astrophysics Data System (ADS)

CI chondrites are among the most unusual type of carbonaceous chondrites. There are only five CI1 meteorite falls. They are heavily altered (BULLOCK et al., 2005), yet show a similar bulk composition to the solar photosphere (ANDERS and GREVESSE, 1989; LODDERS, 2003). There still remains uncertainties about the origin and formation of the parent bodies for such meteorites. One theory is that CI chondrites derive from cometary nuclei, based on evidence from textural and mineralogical arguments (CAMPINS and SWINDLE, 1998) and orbital parameters (GOUNELLE et al., 2006). We now have known cometary material to compare to CI chondrites. The NASA sample return mission Stardust returned to Earth on January 2006. This mission collected cometary dust particles by flying through the coma of comet 81P/Wild 2. The Preliminary Examination (Science, 314, 2006) and subsequent studies (MaPS, 43, 2008), showed that expected hydrated minerals seem to be absent. This may in part be because finer-grained hydrated minerals are less likely to survive the collection process (ISHII et al., 2008) although experimental studies (BURCHELL et al., 2006; NOGUCHI et al., 2007) have shown that coarser (> m) phyllosilicates can survive capture under conditions analogous to the Stardust encounter. To determine the relationship between CIs and returned cometary material, we may therefore have to focus on the distinctive composition of anhydrous minerals, which are rare in CI meteorites. Olivine is a common mineral in the solar system, and has been reported in diverse compositions within Stardust samples, especially with distinctive levels of Fe, Cr and Mn. In cold cometary bodies it is unlikely that the chemical composition of olivine will have been affected by parent body processing, so olivines are likely to be unaltered and could provide evidence for any primary genetic link between CIs and cometary material. In this study we present an optimised analytical technique to detect micrometer-sized olivine grains in large area searches of the matrix of CI chondrites, locating the sparse grains, which can then be characterised by microanalysis (Electron Microprobe, TEM, TOF-SIMS). We then compare CI olivine compositions with Stardust ones, in order to distinguish any genetic link. References: ANDERS E. and GREVESSE N. (1989) Abundances of the elements - Meteoritic and solar. Geochimica et Cosmochimica Acta 53, 197-214. BULLOCK E. S., GOUNELLE M., LAURETTA D. S., GRADY M. M. and RUSSELL S. S. (2005) Mineralogy and texture of Fe-Ni sulfides in CI1 chondrites: Clues to the extent of aqueous alteration on the CI1 parent body. Geochimica et Cosmochimica Acta 69, 2687-2700. BURCHELL M. J., GRAHAM G. and KEARSLEY A. (2006) Cosmic Dust Collection in Aerogel. Annual Review of Earth and Planetary Sciences 34, 385-418. CAMPINS H. and SWINDLE T. D. (1998) Expected characteristics of cometary meteorites. Meteoritics & Planetary Science 33, 1201-1211. GOUNELLE M., SPURNY, PAVEL and BLAND P. A. (2006) The orbit and atmospheric trajectory of the Orgueil meteorite from historical records. Meteoritics & Planetary Science 41, 135-150. ISHII H. A., BRADLEY J. P., DAI Z. R., CHI M., KEARSLEY A. T., BURCHELL M. J., BROWNING N. D. and MOLSTER F. (2008) Comparison of Comet 81P/Wild 2 Dust with Interplanetary Dust from Comets. Science 319(5862), 447-450. LODDERS K. (2003) Solar System Abundances and Condensation Temperatures of the Elements. Astrophysical Journal 591, 1220-1247. NOGUCHI T., NAKAMURA T., OKUDAIRA K., YANO H., SUGITA S. and BURCHELL M. J. (2007) Thermal alteration of hydrated minerals during hypervelocity capture to silica aerogel at the flyby speed of Stardust. Meteoritics and Planetary Science 42, 357-372.

Le Gac, Y.; Kearsley, A. T.; Bland, P. A.; Russell, S. S.

2009-04-01

341

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 ? 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 ? 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.; Plmper, O.; Putnis, A.

2009-04-01

342

Disclinations and grain boundary migration: evidence for a new deformation mechanism in olivine-rich rocks (Invited)  

NASA Astrophysics Data System (ADS)

The rheology of olivine-rich rocks remains poorly understood. In particular, the ability of orthorhombic olivine to bear large strains represents an apparent violation of the von Mises criterion due to a lack of slip systems. In this study we show that a more general description of the deformation process including the motion of rotational defects referred to as disclinations can solve the olivine deformation paradox. Disclinations were proposed together with dislocations by Volterra (1907) to account for elastic distorsions (distorzione) in solids. They have recently been experimentally evidenced from orientation maps in several polycrystalline metallic alloys (Beausir & Fressengeas, 2013). Using high-resolution EBSD orientation maps we show that disclinations 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 allows further understanding of grain boundary-mediated plasticity in polycrystalline aggregates. By providing the missing mechanism for describing plastic flow in olivine, the present work allows multiscale modeling of the rheology of the upper mantle, from the atomic scale to the scale of the flow. Beausir, B. & Fressengeas, C., Disclination densities from EBSD orientation mapping. International Journal of Solids and Structures 50 (1), 137-146 (2013). Volterra, V., Sur l'quilibre des corps lastiques multiplement connexes. Annales scientifiques de l'cole Normale Suprieure 24, 401-517 (1907). Acknowledgement for support: ERC grant RheoMan, Marie Curie fellowship PoEM and ANR NanoMec.

Cordier, P.; Demouchy, S. A.; Beausir, B.; Taupin, V.; Fressengeas, C.

2013-12-01

343

Geobarometry of ultramafic xenoliths from Loihi Seamount, Hawaii, on the basis of CO2 inclusions in olivine  

USGS Publications Warehouse

Abundant fluid inclusions in olivine of dunite xenoliths (???1-3 cm) in basalt dredged from the young Loihi Seamount, 30 km southeast of Hawaii, are evidence for three coexisting immiscible fluid phases-silicate melt (now glass), sulfide melt (now solid), and dense supercritical CO2 (now liquid + gas)-during growth and later fracturing of some of these olivine crystals. Some olivine xenocrysts, probably from disaggregation of xenoliths, contain similar inclusions. Most of the inclusions (2-10 ??m) are on secondary planes, trapped during healing of fractures after the original crystal growth. Some such planes end abruptly within single crystals and are termed pseudosecondary, because they formed during the growth of the host olivine crystals. The "vapor" bubble in a few large (20-60 ??m), isolated, and hence primary, silicate melt inclusions is too large to be the result of simple differential shrinkage. Under correct viewing conditions, these bubbles are seen to consist of CO2 liquid and gas, with an aggregate ??{variant} = ??? 0.5-0.75 g cm-3, and represent trapped globules of dense supercritical CO2 (i.e., incipient "vesiculation" at depth). Some spinel crystals enclosed within olivine have attached CO2 blebs. Spherical sulfide blebs having widely variable volume ratios to CO2 and silicate glass are found in both primary and pseudosecondary inclusions, demonstrating that an immiscible sulfide melt was also present. Assuming olivine growth at ??? 1200??C and hydrostatic pressure from a liquid lava column, extrapolation of CO2 P-V-T data indicates that the primary inclusions were trapped at ??? 220-470 MPa (2200-4700 bars), or ??? 8-17 km depth in basalt magma of ??{variant} = 2.7 g cm-3. Because the temperature cannot change much during the rise to eruption, the range of CO2 densities reveals the change in pressure from that during original olivine growth to later deformation and rise to eruption on the sea floor. The presence of numerous decrepitated inclusions indicates that the inclusion sample studied is biased by the loss of higher-density inclusions and suggests that some part of these olivine xenoliths formed at greater depths. ?? 1983.

Roedder, E.

1983-01-01

344

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

345

Suppression of Phase Separation in LiFePO4 Nanoparticles During Battery Discharge  

E-print Network

Using a novel electrochemical phase-field model, we question the common belief that LixFePO4 nanoparticles separate into Li-rich and Li-poor phases during battery discharge. For small currents, spinodal decomposition or nucleation leads to moving phase boundaries. Above a critical current density (in the Tafel regime), the spinodal disappears, and particles fill homogeneously, which may explain the superior rate capability and long cycle life of nano-LiFePO4 cathodes.

Bai, Peng; Bazant, Martin Z

2011-01-01

346

Suppression of Phase Separation in LiFePO 4 Nanoparticles During Battery Discharge  

E-print Network

Using a novel electrochemical phase-field model, we question the common belief that LiXFePO? nanoparticles always separate into Li-rich and Li-poor phases during battery discharge. For small currents, spinodal decomposition ...

Bai, Peng

347

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

348

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity  

NASA Astrophysics Data System (ADS)

The specific capacity of commercially available cathode carbon-coated lithium iron phosphate is typically 120-160?mAh?g-1, which is lower than the theoretical value 170?mAh?g-1. Here we report that the carbon-coated lithium iron phosphate, surface-modified with 2 wt% of the electrochemically exfoliated graphene layers, is able to reach 208?mAh?g-1 in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes, where the graphene flakes exhibit a capacity higher than 2,000?mAh?g-1. The highly conductive graphene flakes wrapping around carbon-coated lithium iron phosphate also assist the electron migration during the charge/discharge processes, diminishing the irreversible capacity at the first cycle and leading to ~100% coulombic efficiency without fading at various C-rates. Such a simple and scalable approach may also be applied to other cathode systems, boosting up the capacity for various Li batteries.

Hu, By Lung-Hao; Wu, Feng-Yu; Lin, Cheng-Te; Khlobystov, Andrei N.; Li, Lain-Jong

2013-04-01

349

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

350

Optimization of LiFePO4 Nanoparticle Suspensions with Polyethyleneimine for Aqueous Processing  

SciTech Connect

Addition of dispersants to aqueous based lithium-ion battery electrode formulations containing LiFePO{sub 4} is critical to obtaining a stable suspension. The resulting colloidal suspensions enable dramatically improved coating deposition when processing electrodes. This research examines the colloidal chemistry modifications based on polyethyleneimine (PEI) addition and dispersion characterization required to produce high quality electrode formulations and coatings for LiFePO{sub 4} active cathode material. The isoelectric point, a key parameter in characterizing colloidal dispersion stability, of LiFePO{sub 4} and super P C45 were determined to be pH = 4.3 and 3.4, respectively. PEI, a cationic surfactant, was found to be an effective dispersant. It is demonstrated that 1.0 wt % and 0.5 wt % PEI were required to stabilize the LiFePO{sub 4} and super P C45 suspension, respectively. LiFePO{sub 4} cathode suspensions with 1.5 wt % PEI demonstrated the best dispersibility of all components, as evidenced by viscosity and agglomerate size of the suspensions and elemental distribution within dry cathodes. The addition of PEI significantly improved the LiFePO{sub 4} performance.

Li, Jianlin [ORNL; Armstrong, Beth L [ORNL; Kiggans, Jim [ORNL; Daniel, Claus [ORNL; Wood III, David L [ORNL

2012-01-01

351

A laser-ablation ICP-MS study of Apollo 15 low-titanium olivine-normative and quartz-normative mare basalts  

E-print Network

fractionation, within the lava flows. In contrast, the younger ($3.25 Ga) olivine-normative basalts experienced, the older ($3.35 Ga) quartz-normative basalts, with lower TiO2 experienced olivine, chromite, and Cr ($4.0 to 2.8 Ga; e.g., Snyder et al., 2000) and composition- ally different from that of Earth (Taylor

Perfect, Ed

352

H2O and CO2 in kimberlitic fluid as recorded by diamonds and olivines in several Ekati Diamond Mine kimberlites, Northwest Territories, Canada  

Microsoft Academic Search

Surface dissolution features on diamonds and Fourier Transform Infra Red spectroscopy (FTIR) of phenocrystal and xenocrystal olivines from kimberlites contain a record of magmatic fluid in kimberlite magmas. We investigated composition and behavior of kimberlitic fluid and the effect of volatiles on the eruption style and geology of kimberlites using microdiamonds and olivine concentrates from six kimberlite pipes with different

Yana Fedortchouk; Sergei Matveev; Jon A. Carlson

2010-01-01

353

H 2O and CO 2 in kimberlitic fluid as recorded by diamonds and olivines in several Ekati Diamond Mine kimberlites, Northwest Territories, Canada  

Microsoft Academic Search

Surface dissolution features on diamonds and Fourier Transform Infra Red spectroscopy (FTIR) of phenocrystal and xenocrystal olivines from kimberlites contain a record of magmatic fluid in kimberlite magmas. We investigated composition and behavior of kimberlitic fluid and the effect of volatiles on the eruption style and geology of kimberlites using microdiamonds and olivine concentrates from six kimberlite pipes with different

Yana Fedortchouk; Sergei Matveev; Jon A. Carlson

2010-01-01

354

Spectral properties of carbonatized ultramafic mantle xenoliths and their host olivine basalts, Jabal Al Maqtal basin, South Eastern Desert, Egypt, using ASD FieldSpec spectroradiometer  

Microsoft Academic Search

Understanding the spectral properties of the carbonatized ultramafic mantle xenoliths and their host olivine basalts exposed at Jabal Al Maqtal strike-slip basin, south Eastern Desert, Egypt using portable ASD FieldSpec is the main task of this article. Field data revealed the presence of ultramafic mantle xenoliths at different stratigraphic levels within Jurassic olivine basalts. Ultramafic mantle xenoliths are recorded within

Ahmed A. Madani

2011-01-01

355

Olivine or impact melt: Nature of the Orange material on Vesta from Dawn  

NASA Astrophysics Data System (ADS)

NASAs Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types: (a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), (b) lobate patches with well-defined edges (nicknamed pumpkin patches), and (c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed Leslie feature first identified by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Several possible options for the composition of the orange material are investigated including, cumulate eucrite layer exposed during impact, metal delivered by impactor, olivine-orthopyroxene mixture and impact melt. Based on our analysis, the orange material on Vesta is unlikely to be metal or olivine (originally proposed by Gaffey (Gaffey, M.J. [1997]. Icarus 127, 130-157)). Analysis of the elemental composition of Oppia ejecta blanket with GRaND suggests that its orange material has ?25% cumulate eucrite component in a howarditic mixture, whereas two other craters with orange material in their ejecta, Octavia and Arruntia, show no sign of cumulate eucrites. Morphology and topography of the orange material in Oppia and Octavia ejecta and orange patches suggests an impact melt origin. A majority of the orange patches appear to be related to the formation of the Rheasilvia basin. Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt.

Le Corre, Lucille; Reddy, Vishnu; Schmedemann, Nico; Becker, Kris J.; O'Brien, David P.; Yamashita, Naoyuki; Peplowski, Patrick N.; Prettyman, Thomas H.; Li, Jian-Yang; Cloutis, Edward A.; Denevi, Brett W.; Kneissl, Thomas; Palmer, Eric; Gaskell, Robert W.; Nathues, Andreas; Gaffey, Michael J.; Mittlefehldt, David W.; Garry, William B.; Sierks, Holger; Russell, Christopher T.; Raymond, Carol A.; De Sanctis, Maria C.; Ammanito, Eleonora

2013-11-01

356

Formation of accretionary dust mantles in the solar nebula: Evidence from preirradiated olivines in CM chondrites  

NASA Astrophysics Data System (ADS)

CM chondrites are regolith breccias consisting of lithic clasts embedded in a fine-grained clastic matrix. The majority of these lithic clasts belongs to a texturally well-defined rock type (primary rock) that can be described as an agglomerate of chondrules and other coarse-grained components, most of which are surrounded by fine-grained rims (dust mantles). Metzler et al. (1992) explain these textures as the result of accretionary processes in the solar nebula, while an alternative model explains them to be the result of regolith processes on the parent body (Sears et al. 1993). The main intention of the present study is to discern between both models by investigating the occurrence, frequency, spatial distribution, and textural setting of preirradiated (track-rich) olivines in CM chondrites. Track-rich olivines were studied in situ in six polished thin sections from 4 different CM chondrites (Cold Bokkeveld, Mighei, Murchison, Nogoya) by optical and scanning electron microscopy (SEM). It was found that their occurrence is restricted to the clastic matrix of these meteorites. The primary rock seems to have formed in an environment shielded from cosmic radiation, since fragments of this rock are free of track-rich grains and solar noble gases. This finding supports the solar nebula model for the formation of dust mantles around chondrules and other coarse-grained components, and points against a regolith origin. In Cold Bokkeveld, a small breccia-in-breccia clast was found, which has been irradiated as an entity within the uppermost millimeters to meters of its parent body for at least about 3 Ma. This clast seems to represent a compacted subsurface layer that was later excavated by impact and admixed to the host breccia. Furthermore, the results of this study may affect the interpretation of compaction ages obtained by fission track methods, since these ages may be mixtures of different contact ages between finegrained, U-rich dust and U-poor olivines. In some cases, they may date the formation of dust mantles in the solar nebula, while in other cases the lithification of the host breccias may be dated.

Metzler, Knut

2004-08-01

357

Chlorine/bromine ratios in fracture-filling aqueous alteration products in Nakhla olivine  

SciTech Connect

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 +/- 13 shows that the secondary altered material is pristine, extraterrestrial and akin to the Martian soil. During the early Martian history, volcanic emanations contributed large excesses of volatiles including halogens, sulfur and water to the Martian crust. These chemically-reactive elements had undergone extensive redistribution over time due to a variety of surface processes on Mars. To understand the nature of the alterations due to aqueous activity in the Martian surface environment, a study of halogens, in particular Cl/Br ratios in secondary mineralization products may provide valuable insights. Dreibus and Waenke arrived at a Cl/Br ratio of {approx}110 for the Martian surface materials by studying glasses and bulk samples of several SNC meteorites using neutron activation. Nakhla probably offers the most diverse suite of aqueous precipitates to be found among the SNC meteorites. Numerous veins of hydrous clay within olivine grains are present in Nakhla. Bridges and Grady and Wentworth and McKay observed massive concentrations of halite of probable Martian evaporitic origin, in association with siderite and anhydrite in interstitial areas in Nakhla. Dreibus et al. reported Cl/Br ratios in 3 Nakhla fragments from 104 to 550 and found that 90% of the Cl and Br was readily leachable from this material. Their Nakhla leachate ratio was 580. Their analysis of an attached salt grain yielded a ratio of 5440, similar to that in table salt. Xirouchakis et al. found 20 ppm Br in glass veins in Los Angeles shergottite based on XRF measurements with the x-ray microprobe (beamline X26A) at the Brookhaven Nat. Lab. We examine in this study whether a Cl/Br ratio similar to that of Dreibus and Waenke is also present in products of secondary mineralization, generated as a result of aqueous alteration in some SNC meteorites. We have studied the Cl/Br ratios in fracture-filling materials in veins in Nakhla olivines (thin sections) by determining Br contents using the X-ray Microprobe facility at GeoSoilEnviroCARS (Advanced Photon Source/University of Chicago) and by determining Cl using SEM-based EDX measurements at the same sites in the veins.

Sutton, S.R.; Rao, M.N.; Dreibus, G.; McKay, D.S.; Wanke, H.; Wentworth, S.; Newville, M.; Trainor, T.; Flynn, G.J. (Max-Plank Inst); (SUNY Plattsburgh); (UofC); (Lockheed Martin); (NASA)

2005-04-22

358

A High-strain Flow Law for Olivine: Grain-size Sensitivity and Crystallographic Fabric  

NASA Astrophysics Data System (ADS)

The dislocation-accommodated grain-boundary sliding regime, which has recently been recognized in deformation experiments on olivine aggregates, has important implications for the rheological characteristics of the upper mantle and for the interpretation of microstructures in naturally deformed rocks. However, previous experimental studies suffer from both the difficulty in synthesizing samples with a desired mean grain size and the limitation that crystallographic fabrics have not fully developed at low strains. We alleviate these difficulties in a series of innovative deformation experiments. Aggregates of iron-bearing olivine, hot pressed as hollow cylinders, were deformed in torsion at 1200C in a gas-medium apparatus at constant strain rate until a steady-state shear stress was reached, which occurred by a shear strain of ~5. Since recrystallized grain size is a function of shear stress, we were able to systematically vary the mean grain size among samples by changing the controlling shear-strain rate. Above a shear strain of ~5, strain rate stepping tests were performed to determine the stress exponent. Between each strain-rate step, the strain rate was returned to the original strain rate to reset the microstructure. Experiments were stopped when the total shear strain reached ~11. Our results yield a stress exponent of ~4 and a grain size exponent of ~1, both of which agree with previous small-strain compression experiments on olivine in the dislocation-accommodated grain-boundary sliding regime. If the dependence of strain rate on grain size in the power-law flow law is removed by inserting the grain-size piezometer, the apparent stress exponent in the resulting grain size independent flow law increases to 5.2. Microstructural analyses indicate that very strong crystallographic-preferred orientation (CPO) fabrics are developed with M-indices of ~0.6. The CPO fabrics have [100] maxima sub-parallel to the shear direction and [010] maxima sub-perpendicular to the shear plane, consistent with activation of the (010)[100] slip system. These results confirm the validity of grain-size exponents previously determined in compression experiments and demonstrate that grain-boundary sliding can form very strong CPO fabrics at high strain. Thus, the observation of a pronounced CPO in naturally deformed rocks may indicate the activation of grain-boundary sliding rather than simply dislocation creep, and both the grain-size and the deformation conditions need to be compared to newly derived flow laws to determine the dominant deformation mechanism.

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

2011-12-01

359

Discovery of Wadsleyite (?-phase olivine) in Peridotites of the Nidar Ophiolite, Indus Suture Zone, Indian Himalaya  

NASA Astrophysics Data System (ADS)

In two presentations at this meeting (this and Das et al.) we report the discovery of ultra high-pressure mineral assemblages in peridotites of the Nidar Ophiolite in NW Indian Himalaya. The peridotite hosts of the ultra-deep origin minerals occur as 'xenoliths' within mapped dunite channels at the base of the ophiolite. Here we report the discovery of wadsleyite (?-phase olivine) within a Cr-spinel grain of the peridotite. The wadsleyite measures 120 ?m x 30 ?m included in the 300 ?m x 500 ?m Cr-spinel grain of the peridotite. The euhedral opaque wadsleyite grain displays Raman spectra of forsteritic olivine, doublet at 823 cm-1, 854 cm-1 with a 961 cm-1 peak. The peaks at 542 cm-1 and 918 cm-1 are also seen in experimentally shocked dunite. The 918 cm-1 is the principal wadsleyite peak; one at 699 cm-1 may also belong to it. The 372 cm-1 peak along with 605 cm-1 peak may be assigned to ringwoodite. These spectra were obtained at the Wadia Institute using a LabRAM HR-Horibe Jovin Yovon instrument, and confirmed at Cornell University's CCMR with a Renishaw IN Via Conofocal Raman Spectroscope. Thus the grain is primarily a forsteritic olivine but signatures of high pressure Mg2SiO4 spinelloid are present. Based on the P-T stability of wadsleyite, we infer this grain began its journey at depths between 410 km - 660 km in the mantle transition zone, and reflecting the scale and dynamics of convective flow of heat and matter arrived within the peridotites beneath the Nidar Ophiolite's volcanic crust. Laser Raman spectra of the wadsleyite grain within a Cr-spinel of a peridotite body at the base of the Nidar Ophiolite Complex, Indus Suture Zone , Indian Himalaya. The spectra is one of several confirmed by two different Laser Raman facilities at the Wadia Institute , India and at the CCMR, Cornell University , USA. See text for detailed analysis of the spectra.

Basu, A. R.; Das, S.; Mukherjee, B. K.

2013-12-01

360

On the Activation Volume for Dislocation Creep and Diffusion in Olivine and Other Minerals  

NASA Astrophysics Data System (ADS)

The activation volume is an important parameter that characterizes the pressure dependence of plastic deformation. However, experimental determination of activation volume is challenging and, for olivine, the published results range from ~0 to ~30 cm3/mol. This vast range of V* is translated into more than 10 orders of magnitude difference in viscosity in the deep upper mantle (for a given stress). The main reasons for this large discrepancy include (i) the large experimental errors in the previous experimental studies on V* due to the limited pressure range and the limited resolution of mechanical measurements and (ii) the confusions in parameterization of flow law. In this talk, I will discuss several issues in determining and interpreting V*. In addition to the issues of uncertainties in experimental measurements, one important issue in the experimental determination of V* is the choice of flow law formula. It is customary to use a power-law equation to determine V*, but the appropriateness of power-law relationship is not obvious, and two issues need to be addressed carefully. First, at stress exceeding ~200 MPa (for olivine), deviation from power- law behavior is appreciable and the exponential flow law becomes important. The transition to exponential flow law will result in (i) apparently small V* if the data were fitted to a power-law relation, and (ii) apparently negative dependence of activation enthalpy (as observed by Green and Borch (1987)). Second, the flow-law parameterization under water-saturated conditions needs to include the pressure dependence of water fugacity. When this effect is ignored, apparently small activation volume would be obtained. Third, if deform,ation is in the transient creep regime rather than in the "steady-state" creep regime, then the activation volume will be an apparent activation volume that can be significantly lower than the "true" activation volume if the transient creep behavior is pressure-dependent. I will review the existing data on olivine and other materials to estimate the "intrinsic" ("true") activation volumes in these minerals.

Karato, S.

2006-12-01

361

Lunar highland rocks - Element partitioning among minerals. II - Electron microprobe analyses of Al, P, Ca, Ti, Cr, Mn and Fe in olivine  

NASA Technical Reports Server (NTRS)

Lunar olivines from anorthosites, granulitic impactites, and rocks in the Mg-rich plutonic trend were subjected to electron probe measurements for Al, P, Ca, Ti, Cr and Mn, which show that the FeO/MnO ratio for lunar olivines lies between 80 and 110 with little difference among the rock types. The low values of Ca in lunar olivines indicate slow cooling to subsolidus temperatures, with blocking temperatures of about 750 C for 67667 and 1000 C for 60255,73-alpha determined by the Finnerty and Boyd (1978) experiments. An important paradox is noted in the low Ti content of Fe-rich olivines from anorthosites, although both Ti and Fe tend to become enriched in liquid during fractional distillation. Except for Ca and Mn, olivine from anorthosites has lower minor element values than other rock types. Formation from a chemically distinct system is therefore implied.

Smith, J. V.; Hansen, E. C.; Steele, I. M.

1980-01-01

362

Experimental partitioning of rare earth elements and scandium among armalcolite, ilmenite, olivine and mare basalt liquid  

NASA Technical Reports Server (NTRS)

An experimental study was carried out to measure partition coefficients for two rare-earth elements (Sm and Tm) and Sc among armalcolite, ilmenite, olivine and liquid coexisting in a system modeled on high-Ti mare basalt 74275. This 'primitive' sample was chosen for study because its major and trace element chemistry as well as its equilibrium phase relations at atmospheric pressure are known from previous studies. Beta-track analytical techniques were used so that partition coefficients could be measured in an environment whose bulk trace element composition is similar to that of the natural basalt. Partition coefficients for Cr and Mn were determined in the same experiments by microprobe analysis. The only equilibrium partial melting model appears to be one in which ilmenite is initially present in the source region but is consumed by melting before segregation of the high-Ti mare basalt liquid from the residue.

Irving, A. J.; Merrill, R. B.; Singleton, D. E.

1978-01-01

363

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

364

Seismic evidence for a metastable olivine wedge in the subducting Pacific slab under Japan Sea  

NASA Astrophysics Data System (ADS)

We apply a forward-modeling approach to high-quality arrival time data from 23 deep earthquakes greater than 400 km depth to investigate the detailed structure of the subducting Pacific slab beneath the Japan Sea. Our results show that a finger-like anomaly exists within the subducting Pacific slab below 400 km depth, which has a P-wave velocity 5% lower than the surrounding slab velocity (or 3% lower than that of the normal mantle), suggesting the existence of a metastable olivine wedge (MOW) in the slab. The MOW top and bottom depths are 400 and 560 km, respectively. The MOW is estimated to be about 50 km wide at 400 km depth and close to the slab upper boundary. At 560 km depth the MOW is located at about 25 km below the slab upper boundary. Most of the deep earthquakes are located in the MOW. Our results favor transformational faulting as the mechanism for deep earthquakes.

Jiang, Guoming; Zhao, Dapeng; Zhang, Guibin

2008-06-01

365

Crystal Size Distributions from Porphyritic Olivine Chondrules: Insights into Formation Conditions  

NASA Technical Reports Server (NTRS)

Most chondrules preserve, in their texture, a record of their precursor material and the nature and intensity of the nebular events in which they were formed. We have used crystal size distributions (CSDs) together with crystallization experiments to explore the textures of natural chondrules and their relationships to natural formation conditions. Many careful experimental studies have demonstrated fundamental relationships between the texture of a chondrule and its precursor material, melting intensity, and cooling rate. However, until recently most studies have focused on distinctions between textural types (e.g., barred, radial, porphyritic). Previous work has shown that CSDs provide precise, reproducible characterizations of chondrule-scale textures, and can be used together with crystallization experiments to estimate chondrule formation conditions. Here, we expand this study to investigate the link between texture and formation conditions for a range of natural porphyritic olivine (PO) chondrules.

Zieg, M. J.; Lofgren, G. E.

2003-01-01

366