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  • 1
    Electronic Resource
    Electronic Resource
    Vanadium partitioning and the oxidation state of Archaean komatiite magmas (1997)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 389 (1997), S. 842-845 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The MgO content of komatiite lavas is an important measure of their formation temperature deep in the Archaean mantle, and forms the basis for models of the early Earth's thermal and chemical evolution. Estimates of the primary MgO content of komatiites are sensitive to the oxidation ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/39860
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  • 2
    Electronic Resource
    Electronic Resource
    Automated in situ trace element analysis of silicate materials by laser ablation inductively coupled plasma mass spectrometry (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 73-78 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper describes the automated in situ trace element analysis of solid materials by laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS). A compact computer-controlled solid state Nd:YAG MerchantekTM EO UV laser ablation (LA) system has been coupled with the high sensitivity VG PQII S ICP-MS. A two-directional communication was interfaced in-house between the ICP-MS and the LA via serial RS-232 port. Each LA-ICP-MS analysis at a defined point includes a 60 s pre-ablation delay, a 60 s ablation, and a 90 s flush delay. The execution of each defined time setting by LA was corresponding to the ICP-MS data acquisition allowing samples to be run in automated cycle sequences like solution auto-sampler ICP-MS analysis. Each analytical cycle consists of four standards, one control reference material, and 15 samples, and requires about 70 min. Data produced by Time Resolved Analysis (TRA) from ICP-MS were later reduced off-line by in-house written software. Twenty-two trace elements from four reference materials (NIST SRM 613, and fused glass chips of BCR-2, SY-4, and G-2) were determined by the automated LA-ICP-MS method. NIST SRM 610 or NIST SRM 613 was used as an external calibration standard, and Ca as an internal standard to correct for drift, differences in transport efficiency and sampling yield. Except for Zr and Hf in G-2, relative standard deviations for all other elements are less than 10%. Results compare well with the data reported from literature with average limits of detection from 1 ng g–1 to 455 ng g–1 and less than 100 ng g–1 for most trace elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000528
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  • 3
    Electronic Resource
    Electronic Resource
    Constraints on the origin of mantle-derived low Ca garnets (1992)
    Springer
    Contributions to mineralogy and petrology 109 (1992), S. 421-430 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Current hypotheses for the source rock of low Ca garnets hosted in mantle-derived diamonds and xenoliths range from residues of komatiite generation, to subducted serpentinite, to subducted mid-ocean ridge (MORB) harzburgite. Experiments designed to test these hypotheses were undertaken. The stability and compositional variation of garnets at pressures above 4 GPa through the melting interval of hydrous peridotite, in the subsolidus of depleted harzburgite and peridotite compositions, and along the liquidus of aluminium-undepleted and aluminium-depleted komatiites were examined, and compared with petrological data for natural low Ca garnets. Partitioning of Cr between garnet and ultramafic liquid along the liquidus of komatiites and within the melting interval of peridotite, indicates that garnets in mantle residues after single stage Archean ultramafic liquid removal would contain 2 to 4 wt% Cr2O3. Thus, the more Cr-poor population of mantle-derived low Ca garnets, with Cr2O3 less than 4 wt%, could have originated by such a process. Experimental results for other compositions indicate that average cratonic peridotite or its hydrated equivalent is typically too Cr-poor to be the protolith from which low Ca garnets containing greater than 4 wt% Cr2O3 could have crystallized in the upper mantle. Experiments on a spinel harzburgite composition indicate that an extremely Cr-rich protolith (Cr/Cr+Al〉0.3) is required to crystallize spinel and Cr-rich low Ca garnets, at pressures deduced for the ultramafic inclusion suite in diamonds (5 to 7 GPa). Natural examples of such Cr-rich protoliths are represented in some ophiolite harzburgites. All the experimental data taken together require that low Ca garnets with greater than 4 wt% Cr2O3 originated from residues that underwent multiple melt extraction. Whether such multi-stage events formed protoliths for low Ca garnets at shallow (i.e. MORB source region) or deep (i.e. komatiite source region) levels in the Precambrian mantle is not completely resolvable. The former environment can better account for the abundance of spinel in many diamonds hosting low Ca garnets, but the latter scenario best explains the presence of low Ca garnets in harzburgite xenoliths with ‘cratonic’ bulk compositions well removed from typical MORB residues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306546
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  • 4
    Electronic Resource
    Electronic Resource
    Oxidation state of mantle xenoliths from British Columbia, Canada (1990)
    Springer
    Contributions to mineralogy and petrology 104 (1990), S. 453-462 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Mössbauer spectra for 17 spinels separated from mantle xenoliths from six different eruptive centers in southern British Columbia, Canada were measured in an effort to accurately determine their Fe3+/total Fe ratios, and to examine lateral and vertical variations in oxygen fugacities (f o2's) calculated for these samples using published thermobarometric methods. Spectra acquired at 298 and 77 K suggest that both Fe2+ and Fe3+ are tetrahedrally coordinated in lherzolite spinels from this alkaline province. Calculatedf o2's for spinel lherzolites from British Columbia range from about 0.5 to 1.5 log units below the fayalite-magnetite-quartz (FMQ) oxygen buffer at 15 kbar using the thermobarometric method of O'Neill and Wall. Thesef o2's are on average more reducing than those reported for the upper mantle beneath the Massif Central and Japanese Arc and fall within the range for fresh MORB glasses and for lherzolite xenoliths from the southwestern United States and Mongolia. Significant variations inf o2 between samples from different eruptive centers with varying ages are absent, indicating that the oxidation state of the upper mantle was not affected by Cenozoic magmatism within this alkaline province.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575622
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  • 5
    Electronic Resource
    Electronic Resource
    An experimental calibration of the “Nickel in Garnet” geothermometer with applications (1994)
    Springer
    Contributions to mineralogy and petrology 117 (1994), S. 410-420 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The partitioning of Ni between olivine and garnet in two multi-component compositions was studied as a function of temperature and pressure in a 6–8 type multi-anvil apparatus. Weighted least squares regression of the experimental results for both compositions give a temperature dependence for Ni partitioning between olivine (Ol) and garnet (Gt) of the form: T=−10210(±114)/[lnD Gt/Ol Ni −3.59(±67)] where DGt/Ol/Ni=Ni content of Gt/Ni content of olivine (by weight) and Tis in Kelvin. The pressure effect on Ni exchange between olivine and garnet is estimated to be ∼0.13 J/bar, and should therefore have a negligible effect on the geothermometer, as is demonstrated in the experiments. The experimentally derived “Ni in Gt” geothermometer is in agreement with an extant empirical version between 1100 to 900°C, but the two thermometers produce significantly different results outside of this temperature range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307274
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  • 6
    Electronic Resource
    Electronic Resource
    Ferric iron in mantle-derived pyroxenes and a new oxybarometer for the mantle (1993)
    Springer
    Contributions to mineralogy and petrology 113 (1993), S. 236-248 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Ferric iron contents of coexisting ortho- and clinopyroxene from spinel lherzolite xenoliths were measured with Mössbauer spectroscopy and found to be significant. In orthopyroxene, the range in Fe3+/ΣFe is from 0.04 to 0.14; in clinopyroxene, the range is from 0.12 to 0.24. Reactions involving coexisting olivine, orthopyroxene, and clinopyroxene, where either the esseneite (CaFe3+ AlSiO6) or the acmite (NaFe3+Si2O6) component in the clinopyroxene is considered, are used to calculate oxygen fugacities. These oxygen fugacities agree well with those calculated with the olivine-orthopyroxene-spinel oxybarometer. Because these reactions do not involve garnet, spinel, or plagioclase, they may be applied to lherzolites to give internally-consistent oxygen fugacities across the pressure-dependent facies boundaries between plagioclase, spinel, and garnet lherzolite. Another application of this method is to predict the Fe3+/ΣFe in clinopyroxene coexisting with olivine and orthopyroxene given pressure, temperature, $$f_{o_2 }$$ , and the compositions of the coexisting phases in either experimental or natural assemblages. At values of $$f_{o_2 }$$ equal to those of the synthetic fayalite-magnetite-quartz buffer, for example, ∼15–35% of the iron in the clinopyroxenes from these xenoliths would be ferric. The simplifying assumption that all Fe is divalent in silicate phases at ‘geologically — reasonable’ oxygen fugacities must be re-evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283231
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  • 7
    Electronic Resource
    Electronic Resource
    The Ni-in-garnet geothermometer: calibration at natural abundances (1999)
    Springer
    Contributions to mineralogy and petrology 136 (1999), S. 240-246 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Experiments to study the partitioning of Ni between olivine and garnet at natural abundances were performed at 1200 °C – 3 GPa, 1300 °C – 3, 5 and 7 GPa and 1500 °C – 5 GPa using piston-cylinder and multi-anvil apparatus. The experiments were intended to provide a further test of the Ni-in-garnet geothermometer calibrated previously using enhanced Ni levels. The run products were analysed by electron microprobe using special operating conditions to enhance counting statistics. Ni-Mg and Fe-Mg exchange between olivine and garnet was tightly reversed. Results of the experiments suggest that Ni substitution in garnet behaves according to Henry's Law up to levels of ∼3000 ppm. The Ni-in-garnet geothermometer derived from reversed experiments in this study is consistent (within error) with that derived from previous experiments at enhanced levels of Ni; neither of these experimental calibrations is consistent with any empirically derived Ni-in-garnet geothermometer. Sources of the discrepancy between the empirical and experimental calibrations of the Ni-in-garnet geothermometer are examined in detail and it is concluded that the main reason for the differences involves errors in the calculation of temperatures in the empirical version. These errors are clearly demonstrated using a recently published data set for garnet peridotite xenoliths in which both Ni-in-garnet and more conventional multi-equilibrium thermobarometry was employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050535
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  • 8
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    Automated in situ trace element analysis of silicate materials by laser ablation inductively coupled plasma mass spectrometry (2000)
    Springer
    Details
    Publication Date: 2000-08-30
    Print ISSN: 0937-0633
    Electronic ISSN: 1432-1130
    Topics: Chemistry and Pharmacology
    Published by Springer
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  • 9
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    Postglacial wetland succession, carbon accumulation, and forest dynamics on the east coast of Vancouver Island, British Columbia, Canada (2019)
    Cambridge University Press
    Details
    Publication Date: 2019
    Description: 〈div data-abstract-type="normal"〉〈p〉Peatland development and carbon accumulation on the Pacific coast of Canada have received little attention in paleoecological studies, despite wetlands being common landscape features. Here, we present a multi–proxy paleoenvironmental study of an ombrotrophic bog in coastal British Columbia. Following decreases in relative sea level, the wetland was isolated from marine waters by 13,300 cal yr BP. Peat composition, non-pollen palynomorph, and C and N analyses demonstrate terrestrialization from an oligotrophic lake to a marsh by 11,600 cal yr BP, followed by development of a poor fen, and then a drier ombrotrophic bog by 8700 cal yr BP. Maximum carbon accumulation occurred during the early Holocene fen stage, when seasonal differences in insolation were amplified. This highlights the importance of seasonality in constraining peatland carbon sequestration by enhancing productivity during summer and reducing decomposition during winter. Pollen analysis shows that 〈span〉Pinus contorta〈/span〉 dominated regional forests by 14,000 cal yr BP. Warm and relatively dry summers in the early Holocene allowed 〈span〉Pseudotsuga menziesii〈/span〉 to dominate lowland forests 11,200–7000 cal yr BP. 〈span〉Tsuga heterophylla〈/span〉 and 〈span〉P. menziesii〈/span〉 formed coniferous forest in the mid- and late Holocene. Tephra matching the mid-Holocene Glacier Peak–Dusty Creek assemblage provides evidence of its most northwesterly occurrence to date.〈/p〉〈/div〉
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
    Topics: Geography , Geosciences
    Published by Cambridge University Press
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  • 10
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    Effect of alkalinity on sulfur concentration at sulfide saturation in hydrous basaltic andesite to shoshonite melts at 1270 ºC and 1 GPa (2018)
    Mineralogical Society of America
    Details
    Publication Date: 2018-01-01
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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