Tellurium Stable Isotope Variations Among Chondrites and Terrestrial Samples
Abstract
The siderophile volatile elements S, Se, and Te are among the most strongly depleted elements in the silicate Earth. They are generally thought to derive predominantly from late accretion, defined as the addition of broadly chondritic material to the Earth's mantle after cessation of core formation. However, it has been suggested that the S isotopic composition of Earth's mantle is isotopically fractionated with respect to chondrites, and that this isotope fractionation results from the preferential incorporation of heavy S isotopes into core-forming metallic melts [1]. As such, only a fraction of the S present in the Earth's mantle would have been added by late accretion. However, the concentration for S, Se, and Te inferred for the Earth's mantle have been used to argue that the entire mantle budget of these elements derives from a volatile-rich late veneer [2]. Mass-dependent Te isotope variations are a promising tool to address these issues and ultimately better constrain the nature and origin of the late-accreted material. Tellurium stable isotope variations may arise as a result of nebular processes, potentially leading to distinct isotopic compositions among chondrites, but may also be produced by isotope fractionation during core formation. Thus, Te stable isotopes may allow to distinguish between different chondrite groups as potential sources of the late veneer, and to investigate the relative roles of late accretion and core formation for establishing the Te abundance of Earth's mantle. We developed a 123Te-125Te double spike method for the precise measurements of Te isotope variations by multi-collector ICP-MS. Currently we are analyzing a suite of well-characterized terrestrial mantle rocks together with samples from the major chondrite classes, with the ultimate goal to evaluate whether the budget of Te in Earth's mantle reflects late accretion or core formation. [1] Labidi J. et al (2013) Nature 501, 208-211. [2] Wang Z. & Becker H. (2013) Nature 499, 328-331.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P31G3767H
- Keywords:
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- 1027 Composition of the planets;
- GEOCHEMISTRYDE: 3672 Planetary mineralogy and petrology;
- MINERALOGY AND PETROLOGYDE: 6299 General or miscellaneous;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5455 Origin and evolution;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS