Major and Trace Element Analysis of Silicate Rocks by XRF and Laser Ablation ICP-MS Using Lithium Borate Fused Glasses: Matrix Effects, Instrument Response and Results for International Reference Materials     

Zongshou Yu  Marc D. Norman  Philip Robinson 《Geostandards and Geoanalytical Research》2003,27(1):67-89

Major and trace element compositions of fifteen silicate rock reference materials have been determined by a combined XRF and laser ablation ICP‐MS (LA‐ICP‐MS) technique on glasses prepared by fusing the sample with a lithium borate flux (sample:flux = 1:3). Advantages of this technique include the ability to measure major and trace element abundances on a single sample using a quick and simple preparation that attacks resistant phases such as zircon without the need for acid dissolution. The method is suitable for a wide variety of bulk compositions including mafic, intermediate and silicic rocks. Abundance‐normalized mass response patterns (the ratio of signal intensity to element concentration) of the LA‐ICP‐MS analyses vary systematically with major element composition, demonstrating the presence of a matrix effect that cannot be compensated by normalisation to a single internal standard element. Increasing the sampling distance between the ICP‐MS cone and the torch reduces the magnitude of this effect, suggesting that a mechanism related to residence time of ablated particles in the plasma may be at least partially responsible for the observed variations in mass response patterns. When using a matrix‐matched calibration, agreement of the LA‐ICP‐MS results with published reference values or those obtained by solution ICP‐MS is 10% relative. Analytical precision based on replicate analyses is typically 5% RSD. Procedural detection limits that include contributions from gas background and flux are 0.01‐0.1 μg g‐¹ for the heavy mass trace elements (Rb‐U). Major element analyses by XRF show excellent agreement with results obtained using a conventional heavy element absorbing flux. High quality major and trace element data for silicate rocks can be achieved by a combined XRF and LA‐ICP‐MS analysis of Li₂B₄O₇/LiBO₂ fused glasses provided an appropriate matrix‐matched calibration is adopted.  相似文献   

Olivine flow mechanisms at 8 GPa   总被引：1，自引：0，他引：1  

Li Li  Paul Raterron  Donald WeidnerJiuhua Chen 《Physics of the Earth and Planetary Interiors》2003,138(2):113-129

The mechanisms responsible for high-temperature olivine deformation are investigated at a pressure of 8 GPa and temperatures up to 1780 K. San Carlos olivine specimens of different average grain sizes (0.5 and 5 μm) were deformed simultaneously between hard-alumina pistons during relaxation experiments. These experiments are carried out in a multi-anvil high-pressure apparatus coupled with synchrotron X-ray radiation. The different grain-size specimens experienced identical P-T-stress condition at any given time. A new method for measuring strains and strain rates (≥10⁻⁶ s⁻¹) of specimens at high pressure is documented. This method uses time-resolved in situ X-ray imaging and an image-analysis computation. The microstructures of run products, recovered after being quenched at different temperatures were characterized by transmission electron microscopy (TEM). We find that high-temperature olivine flow is grain-size insensitive at 8 GPa, which suggests that dislocation creep dominates olivine deformation at high pressure. This result is confirmed by the TEM investigation of our deformed specimens in which we find evidences of the activation of olivine dislocation slip systems. Specimen microstructures are consistent with dynamic recrystallization as an assisting process in olivine deformation during the high-pressure experiments. Extrapolation of our results to the low stress level and large grain size expected in the mantle suggests that dislocation creep assisted by dynamic recrystallization may also dominate natural olivine deformation in the upper mantle.  相似文献   

鼻咽癌CT影像特点分析     

彭吉东  蒋海清  雷剑 《CT理论与应用研究》2002,11(1):40-43

目的是加深对鼻咽癌（NPC）CT征象的认识，提高对其影像诊断水平。方法：搜集经病理证实的NPC69例，详细分析其放疗前CT表现。结果：本组病例，鼻咽侧壁增厚最多见（87．0％），咽旁间隙变窄次之（68．1％），其余依次为茎内软组织增厚致密（59．4％），其他部位受侵则相对少见。结论：NPC累及鼻咽侧壁多见，突破咽频底筋膜后，肿瘤多侵犯咽旁间隙和茎内软组织。  相似文献   

Equation of state of hexagonal aluminous phase in basaltic composition to 63 GPa at 300 K     

S. Ono  K. Hirose  M. Isshiki  K. Mibe  Y. Saito 《Physics and Chemistry of Minerals》2002,29(8):527-531

A laser-heated diamond-anvil cell that is capable of operating up to a pressure of 63 GPa, with X-ray diffraction facilities using a synchrotron radiation source at the SPring-8, has been developed to observe the compressibility of a hexagonal aluminous phase, [K_0.15Na_1.66Ca_0.11Mg_1.29Fe²⁺ _0.86Al_3.13Ti_0.09Si_1.98] _Σ9.27O₁₂. The hexagonal aluminous phase is a potassium host mineral from the subducted oceanic crust in the Earth's lower mantle. A sample was heated using a YAG laser at each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at 300 K using an angle-dispersive technique. Pressure was measured using an internal platinum pressure calibrant. The observed unit-cell volumes were used to obtain a third-order Birch–Murnaghan equation of state: unit-cell volume V _o=185.94(±16) ų, density ρ _o=4.145 g/cm³, and bulk modulus K _o=198(±3) GPa when the first pressure is derivative of the bulk modulus K ^′ _o is fixed to 4. The density of hexagonal aluminous phase is lower than that of coexisting Mg-perovskite in the subducted oceanic crust.  相似文献   

Crystal orbital contributions to the pyrrhotite valence band with XPS evidence for weak Fe–Fe π bond formation     

H. W. Nesbitt  A. G. Schaufuss  G. M. Bancroft  R. Szargan 《Physics and Chemistry of Minerals》2002,29(1):72-77

 Synchrotron excited X-ray photoelectron spectra (SXPS) of hexagonal pyrrhotite reveal three distinct Fe 3d-derived photopeaks within its outer valence band. The t _2gα band (majority spin) is centered at about 2.5 eV, the e _g α band at about 1.0 eV and the t _2gβ (minority spin) contribution at about 0.25 eV. From these data the ligand field splitting energy is 1.5 (±0.2) eV and the majority spin pairing energy is 2.25 (±0.2) eV. These are the first such XPS measurements for this mineral. S 3p-derived bonding and non-bonding bands are identified, with the former centred at about 6.5 eV and the latter near 4.5 eV. The XPS results are remarkably consistent with SCF-Xα scattered wave molecular orbital calculations. Although the calculations and the collected spectra are consistent, they differ from a recent interpretation of the pyrrhotite valence band. An explanation for the discrepant results is provided. Auger resonant enhancement of Fe 3d photopeaks at 60 eV photon energy results in the t _2gα emission (at 2.5 eV) being strongly enhanced and broader than the t _2gβ emission (0.25 eV). The explanation of these observations requires the presence of weak Fe–Fe π and π^* crystal (molecular) orbitals located near 2.5 eV, and separated by no more than about 0.5 eV. The π-bonded crystal orbitals are derived from weak mixing of adjacent Fe t _2g atomic orbitals along the c crystallographic axis. Received: 15 June 2000 / Accepted: 11 June 2001  相似文献   

In situ X-ray observations of the decomposition of brucite and the graphite–diamond conversion in aqueous fluid at high pressure and temperature     

T. Okada  W. Utsumi  H. Kaneko  M. Yamakata  O. Shimomura 《Physics and Chemistry of Minerals》2002,29(7):439-445

 An experimental technique to make real-time observations at high pressure and temperature of the diamond-forming process in candidate material of mantle fluids as a catalyst has been established for the first time. In situ X-ray diffraction experiments using synchrotron radiation have been performed upon a mixture of brucite [Mg(OH)₂] and graphite as starting material. Brucite decomposes into periclase (MgO) and H₂O at 3.6 GPa and 1050 °C while no periclase is formed after the decomposition of brucite at 6.2 GPa and 1150 °C, indicating that the solubility of the MgO component in H₂O greatly increases with increasing pressure. The conversion of graphite to diamond in aqueous fluid has been observed at 7.7 GPa and 1835 °C. Time-dependent X-ray diffraction profiles for this transformation have been successfully obtained. Received: 17 July 2001 / Accepted: 18 February 2002  相似文献   

X射线荧光光谱法测定多目标地球化学调查样品中主次痕量组分   总被引：25，自引：13，他引：25  

张勤  樊守忠  潘宴山  李国会 《岩矿测试》2004,23(1):19-24

采用低压聚乙烯镶边垫底的粉末样品压片制样,用PW2440X射线荧光光谱仪对多目标地球化学调查样品中Na2O、MgO、Al2O3、SiO2、P、K2O、CaO、Ti、Mn、Fe2O3、Co、Nb、Zr、Y、Sr、Rb、Pb、Th、Zn、Cu、Ni、V、Cr、Ba、La等组分进行测定。重点讨论了微量元素的背景选择和谱线重叠校正问题。使用经验系数法和康普顿散射线作内标校正基体效应,经标准物质分析检验,结果与标准值吻合,用GBW07308和GBW07310水系沉积物国家一级标准物质作精密度试验,统计结果RSD(n=12)除La、Cr、Co和Th<14.00%以外,其余各组分均小于6.00%。  相似文献   

X射线荧光光谱法同时测定土壤样品中碳氮等多元素   总被引：14，自引：13，他引：14  

梁述廷  刘玉纯胡浩 《岩矿测试》2004,23(2):102-108

报道了采用粉末压片制样-X射线荧光光谱法测定土壤样品中C、N、S、Cl、Br、Hf、Mo、Sn、Se、Na、Mg、Al、Si、P、K、Ca、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、As、Rb、Sr、Y、Zr、Nb、Ba、La、Ce、U、Th、Pb等38种元素的分析方法。着重研究了C和N的分析条件、存在问题和注意事项。所拟方法的检出限，精密度和准确度大多数满足覆盖区多目标地球化学调查样品分析质量的要求。  相似文献   

Crystal-chemical and energetic systematics of wadeite-type phases A2BSi3O9 (A = K, Cs; B = Si, Ti, Zr)     

Hongwu Xu  Alexandra Navrotsky  M. Lou. Balmer  Yali Su 《Physics and Chemistry of Minerals》2005,32(5-6):426-435

Wadeite K₂ZrSi₃O₉ and its analogues K₂TiSi₃O₉ and Cs₂ZrSi₃O₉, synthesized by high-temperature solid-state sintering, have been investigated using powder X-ray diffraction coupled with Rietveld analysis and high-temperature oxide melt solution calorimetry. The crystal chemistry and energetics of these phases, together with K₂Si^VISi₃ ^IVO₉, a high-pressure wadeite analogue containing both tetrahedral and octahedral Si, are discussed in term of ionic substitutions. As the size of the octahedral framework cation increases, Si⁴⁺ → Ti⁴⁺ → Zr⁴⁺, the cell parameter c increases at a much higher rate than a. In contrast, increasing the interstitial alkali cation size (K⁺ → Cs⁺) results in a higher rate of increase in a compared with c. This behavior can be attributed to framework distortion around the interstitial cation. The enthalpies of formation from the constituent oxides (ΔH_f,ox⁰) and from the elements (ΔH_f,el⁰) have been determined from drop-solution calorimetry into 2PbO·B₂O₃ solvent at 975 K. The obtained values (in kJ/mol) are as follows: ΔH_f,ox⁰ (K₂TiSi₃O₉) = −355.8 ± 3.0, ΔH_f,el⁰ (K₂TiSi₃O₉) = −4395.1 ± 4.8, ΔH_f,ox⁰ (K₂ZrSi₃O₉) = −374.3 ± 3.3, ΔH_f,el⁰ (K₂ZrSi₃O₉) = −4569.9 ± 5.0, ΔH_f,ox⁰ (Cs₂ZrSi₃O₉) = −396.6 ± 4.4, and ΔH_f,el⁰ (Cs₂ZrSi₃O₉) = −4575.0 ± 5.5. The enthalpies of formation for K₂Si^VISi₃ ^IVO₉ were calculated from its drop-solution enthalpy of an earlier study (Akaogi et al. 2004), and the obtained ΔH_f,ox⁰ (K₂SiSi₃O₉) = −319.7 ± 3.4 and ΔH_f,el⁰ (K₂SiSi₃O₉) = −4288.7 ± 5.1 kJ/mol. With increasing the size of the octahedral framework cation or of the interstitial alkali cation, the formation enthalpies become more exothermic. This trend is consistent with the general behavior of increasing energetic stability with decreasing ionic potential (z/r) seen in many oxide and silicate systems. Further, increasing the size of the octahedral framework cation appears to induce more rapid increase in stability than increasing the interstitial alkali cation size, suggesting that framework cations play a more dominant role in wadeite stability.  相似文献   

Effects of defect and pressure on the thermal expansivity of Fe x O     

Jianzhong Zhang  Yusheng Zhao 《Physics and Chemistry of Minerals》2005,32(4):241-247

Pressure–volume–temperature measurements have been carried out using synchrotron X-ray diffraction for wüstite at static pressures of 1.9, 2.6, and 5.4 GPa. Our results revealed that the composition change of wüstite and, hence, rearrangements of defect structures are primarily caused by the magnetite (Fe₃O₄) exsolution at temperatures of 523–723 K. Based on the isobaric volume–temperature data collected during cooling, the contribution of compositional variations to the unit-cell volumes of wüstite in the ranges of 300–673 K and 723–1073 K is negligibly small, within the experimental uncertainties. These observations suggest that the measured volume changes in the range of 300–673 K and 723–1,073 K can be attributed to the metal–oxygen bond expansion. Owing to the magnetite exsolution, thermal expansion data are obtained in each experiment at 1.9, 2.6, and 5.4 GPa for wüstite of two different compositions, Fe_0.987O and Fe_0.942O. At all three pressures, Fe_0.942O shows a thermal expansion that is about 30% larger than Fe_0.987O. Such findings represent the first experimental evidence of a substantial effect of nonstoichiometry on thermal expansivity, and based on previous thermodynamic calculations of the defect formation and interaction, this effect is likely associated with the distinct defects arrangements in iron-rich and more iron-deficient wüstite. This study also presents thermal equations of state for wüstite of two different compositions. Such volume-related properties at high temperatures are experimentally difficult to obtain in wüstite but important for thermodynamic studies in the binary Fe–O system.  相似文献