TY - CONF A1 - Tatzel, Michael A1 - Vogl, Jochen A1 - Rosner, M. A1 - Tütken, T. T1 - Exploring variations in the three-isotope space: A new approach and application to magnesium isotope fractionation in the mammal food web N2 - In chemical elements with three or more stable isotopes, mass-dependent stable isotope fractionation is expressed by co-varying isotope ratios. In the three-isotope space ((δ’m2/δ’m1)/(( δ’m3/δ’m1)) these plot along a line with a slope (β), the so called ‘terrestrial fractionation line’. This partitioning of stable isotopes results from both kinetic and equilibrium reactions that are characterized by specific β-values. For the natural range of isotope ratios of ‘novel’ stable isotope systems such as Si, Mg, Fe, Zn, Cu this information cannot be accessed because samples fall close to the delta-zero standard where the current measurement precision is too low to resolve small differences in β. We present a new approach to resolve deviations from a reference slope β by standard-sample bracketing against material offset from the natural range. We use this approach to explore the isotope fractionation mechanism in the mammalian food web. We have analyzed Mg stable isotope ratios in bone bioapatite of herbivore, omnivore and carnivore mammals. Positive shifts in δ26/24Mg along the trophic chain (from herbivore to carnivore) together with β= 0.513 suggest the presence of two isotope fractionation mechanisms operating during biomineralization. While positive shifts in δ26/24Mg are in favor of equilibrium isotope fractionation process, the proximity of β to the theoretically calculated β(kinetic) of typically 0.511 suggests the presence of a second component that fractionates stable isotopes kinetically. The herein presented approach is applicable to any element with 3+ stable isotopes analyzed by multi-collector inductively coupled plasma mass spectrometry. T2 - ESAS & CANAS 2018 CY - Berlin, Germany DA - 20.03.2018 KW - Magnesium delta values KW - Equilibrium isotope fractionation KW - Kinetic isotope fractionation KW - Measurement uncertainty KW - Mammals KW - Food web PY - 2018 AN - OPUS4-44643 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -