Manuela Fehr


Last Name

Fehr

First Name

Manuela

ORCID

0000-0001-6360-6358

Organisational unit

03946 - Schönbächler, Maria / Schönbächler, Maria

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Publications 1 - 10 of 27
  • Zirconium isotope evidence for incomplete admixing of r-process components in the solar nebula
    Item type: Journal Article
    Schönbächler, Maria; Lee, Der-Chuen; Rehkämper, Mark; et al. (2003)
    Earth and Planetary Science Letters
  • Tellurium stable isotope fractionation in chondritic meteorites and some terrestrial samples
    Item type: Journal Article
    Fehr, Manuela; Hammond, Samantha J.; Parkinson, Ian (2018)
    Geochimica et Cosmochimica Acta
  • Potential Nucleosynthetic sources of the titanium isotope variations in solar system materials
    Item type: Other Conference Item
    Williams, N.H.; Fehr, Manuela; Akram, W.M.; et al. (2012)
    Meteoritics & Planetary Science
  • Lithium isotope constraints on crust-mantle interactions and surface processes on Mars
    Item type: Journal Article
    Magna, Tomáš; Day, James M.D.; Mezger, Klaus; et al. (2015)
    Geochimica et Cosmochimica Acta
  • Application of MC-ICPMS to the precise determination of tellurium isotope compositions in chondrites, iron meteorites and sulfides
    Item type: Journal Article
    Fehr, Manuela; Rehkämper, Mark; Halliday, Alex N. (2004)
    International Journal of Mass Spectrometry
  • Search for nucleosynthetic and radiogenic tellurium isotope anomalies in carbonaceous chondrites
    Item type: Journal Article
    Fehr, Manuela; Rehkämper, Mark; Halliday, Alex N.; et al. (2006)
    Geochimica et Cosmochimica Acta
  • Lithium isotopes as indicators of meteorite parent body alteration
    Item type: Journal Article
    Sephton, Mark A.; James, Rachael H.; Fehr, Manuela; et al. (2013)
    Meteoritics & Planetary Science
  • Isotopically heavy Ti in kimberlites explained by assimilation of metasomatised lithospheric mantle
    Item type: Journal Article
    Anguelova, Merislava; Giuliani, Andrea; Fehr, Manuela; et al. (2025)
    Geochimica et Cosmochimica Acta
    Kimberlites represent some of the Earth’s deepest sourced mantle melts, but the origin of their variable geochemical signatures is debated, including contributions by source variations and lithospheric interaction during ascent. To evaluate this further, the Ti isotope compositions of selected kimberlites (n = 24) from major cratons worldwide with emplacement ages from 1.15 Ga to the Holocene are reported. The kimberlites display variable Ti isotope compositions ranging from +0.007 ± 0.027 ‰ to +0.173 ± 0.027 ‰ for δ⁴⁹Ti (deviation of ⁴⁹Ti/⁴⁷Ti from the OL-Ti standard). The observed δ⁴⁹Ti variation of ∼0.17 ‰ is notably larger compared to typical mantle-derived primitive magmas (i.e. basalts and komatiites). Significant inter-province δ⁴⁹Ti variations are in contrast with negligible variations within each locality. Notably, primitive and highly differentiated kimberlites within the same kimberlite field display uniform Ti isotope compositions. These results contrast with the Ti isotope differentiation trends observed for silicate magmas, corroborating late-stage crystallisation of major Ti-carriers (i.e. spinel, perovskite, mica) in kimberlites, and may further indicate limited crystal-melt Ti isotope fractionation in carbonated silicate magmas. Heavy Ti isotope compositions observed in some kimberlites cannot be explained by the limited isotopic fractionation predicted between carbonated melts and peridotitic sources during partial melting, or by mixing of ambient mantle with subducted material, including terrigenous sediments with elevated δ⁴⁹Ti. Instead, isotopically heavy Ti appears to occur in kimberlites featuring elevated concentrations of mica and low Mg/Fe in olivine, both considered a hallmark of extensive interaction of primary kimberlite melts with strongly metasomatised, Fe-Ti-rich lithospheric mantle. These observations underscore a dominant role of the lithospheric mantle in shaping the anomalously heavy Ti isotope compositions of kimberlites.
  • Constraining the mass-dependent Ti isotope composition of the chondritic reservoir – An inter-laboratory comparison study
    Item type: Journal Article
    Anguelova, Merislava; Vilela, Nicolas; Kommescher, Sebastian; et al. (2024)
    Geochimica et Cosmochimica Acta
    Titanium isotopes are a promising tracer for planetary differentiation processes. The application of this tracer is, however, currently hampered by the lack of a robust estimate for the chondritic reservoir. Here, we conducted an inter-comparison Ti isotope study of three laboratories with the aim of providing an accurate and precise estimate for the chondritic reservoir. While previous estimates may suffer from heterogeneities on the sampling scale, we chose ordinary chondrites to minimise uncertainties associated with the necessary corrections for nucleosynthetic isotope variations in chondrites, and to allow the analysis of sufficiently large sample sizes representative for bulk meteorites. Titanium isotope data reported by the different laboratories are in good agreement with each other. Ordinary chondrites of different subgroups (H, L, LL) and petrologic types (3–6) display identical Ti isotope compositions within uncertainties (average δ⁴⁹Ti = +0.023 ± 0.009 ‰, 2SE, n = 20; permille deviation of ⁴⁹Ti/⁴⁷Ti from the OL-Ti standard). The average Ti isotope composition of ordinary chondrites is within 2SE identical to that of OIBs (+0.029 ± 0.005 ‰, 2SE, n = 52) and all pre 2.7 Ga mafic and komatiitic rocks (+0.019 ± 0.006 ‰, 2SE, n = 58), indicating that the δ⁴⁹Ti values of the bulk silicate Earth and ordinary chondrites are indistinguishable. Furthermore, our average Ti isotope composition of ordinary chondrites overlaps with those of the Moon, Mars and Vesta, suggesting a homogeneous inner Solar System in terms of mass-dependent Ti isotopes.
  • Tellurium isotopes and their applications in cosmo- and geochemistry
    Item type: Doctoral Thesis
    Fehr, Manuela (2004)
Publications 1 - 10 of 27