arXiv subjects

Elias Wölfer

Publications and source records attributed to Elias Wölfer.

5 recordsLinked to original sources

arXiv2026

Origin of nucleosynthetic isotope variability in the NC reservoir: Evidence from Ti, Cr, and Mo isotopes

Nucleosynthetic isotope anomalies allow distinguishing between non-carbonaceous (NC) and carbonaceous (CC) type meteorites, and have revealed correlated isotope variations especially among NC bodies. Understanding the origin of this NC trend is important for identifying the processes that produced the NC isotope heterogeneity, and for using these isotope anomalies to reconstruct the early evolution of the solar protoplanetary disk. We report mass-independent Ti, Cr, and Mo isotope compositions for a comprehensive set of previously not or only poorly investigated meteorites, as well as acid leachates obtained from the sequential digestion of primitive ordinary chondrites. Some of the samples investigated in this study fill previously identified apparent gaps in the NC trend, suggesting these gaps reflect unrepresentative sampling of a more continuous isotopic trend. Bulk meteorites and leachates exhibit distinct isotope systematics, indicating that the NC isotope variability does not reflect selective thermal processing of presolar carriers in the disk. The NC trend also cannot reflect the continuous addition of CC dust from the outer to the inner disk, because early- and late-formed NC meteorites display largely overlapping isotopic compositions. Instead, we find that the NC isotope heterogeneity is best accounted for by fractionation and mixing among chemically and isotopically distinct dust components, similar to the processes that produced the isotopic variability among carbonaceous chondrites. On this basis we argue for the presence of substructures in the inner disk, which facilitated fractionation and mixing among distinct dust components, and helped preserve a long-lived dust reservoir from which NC planetesimals accreted over an extended period of time.

astro-ph.EP↗

arXiv2025

Origin of moderately volatile elements in Earth inferred from mass-dependent Ge isotope variations among chondrites

The bulk silicate Earth (BSE) is depleted in moderately volatile elements, indicating Earth formed from a mixture of volatile-rich and -poor materials. To better constrain the origin and nature of Earth's volatile-rich building blocks, we determined the mass-dependent isotope compositions of Ge in carbonaceous (CC) and enstatite chondrites. We find that, similar to other moderately volatile elements, the Ge isotope variations among the chondrites reflect mixing between volatile-rich, isotopically heavy matrix and volatile-poor, isotopically light chondrules. The Ge isotope composition of the BSE is within the chondritic range and can be accounted for as a ~2:1 mixture of CI and enstatite chondrite-derived Ge. This mixing ratio appears to be distinct from the ~1:2 ratio inferred for Zn, reflecting the different geochemical behavior of Ge (siderophile) and Zn (lithophile), and suggesting the late-stage addition of volatile-rich CC materials to Earth. On dynamical grounds it has been argued that Earth accreted CC material through a few Moon-sized embryos, in which case the Ge isotope results imply that these objects were volatile-rich, presumably because they were either undifferentiated or accreted volatile-rich objects themselves before being accreted by Earth.

astro-ph.EP↗

arXiv2024

Condensate evolution in the solar nebula inferred from combined Cr, Ti, and O isotope analyses of amoeboid olivine aggregates

Refractory inclusions in chondritic meteorites, namely amoeboid olivine aggregates (AOAs) and Ca-Al-rich inclusions (CAIs), are among the first solids to have formed in the solar system. The isotopic composition of CAIs is distinct from bulk meteorites, which either results from extreme processing of presolar carriers in the CAI-forming region, or reflects an inherited heterogeneity from the Sun's parental molecular cloud. Amoeboid olivine aggregates are less refractory than CAIs and provide a record of how the isotopic composition of solid material in the disk may have changed in time and space. However, the isotopic composition of AOAs and how this composition relates to that of CAIs and later-formed solids is unknown. Here, using new O, Ti, and Cr isotopic data for eight AOAs from the Allende CV3 chondrite, we show that CAIs and AOAs share a common isotopic composition, indicating a close genetic link and formation from the same isotopic reservoir. Because AOAs are less refractory than CAIs, this observation is difficult to reconcile with a thermal processing origin of the isotope anomalies. Instead, the common isotopic composition of CAIs and AOAs is readily accounted for in a model in which the isotopic composition of infalling material from the Sun's parental molecular cloud changed over time. In this model, CAIs and AOAs record the isotopic composition of the early infall, while later-formed solids contain a larger fraction of the later, isotopically distinct infall. This model implies that CAIs and AOAs record the isotopic composition of the Sun and suggests that the nucleosynthetic isotope heterogeneity of the solar system is predominantly produced by mixing of solar nebula condensates, which acquired their distinct isotopic compositions as a result of time-varied infall from the protosolar cloud.

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arXiv2023

Age and genetic relationships among CB, CH and CR chondrites

The carbonaceous Bencubbin-like (CB), high-metal (CH), and Renazzo-like (CR) chondrites are metal-rich chondrites that have been suggested to be genetically linked and are sometimes grouped together as the CR chondrite clan. Of these, the CB and CH chondrites are thought to have formed in an impact-generated vapor-melt plume from material that may be isotopically akin to CR chondrites. We report Mo, Ti, Cr, and Hf-W isotopic data for CB and CH chondrites in order to determine their formation time, to assess whether these chondrites are genetically related, and to evaluate their potential link to CR chondrites. An internal Hf-W isochron for the CH chondrite Acfer 182 yields an age of 3.8 +- 1.2 Ma after the formation of Ca-Al-rich inclusions (CAIs), which is indistinguishable from the mean Hf-W model age for CB metal of 3.8 +- 1.3 Ma. The Mo isotopic data for CB and CH chondrites indicate that both contain some of the same metal and silicate components, which themselves are isotopically distinct. As such, the different Mo isotopic compositions of bulk CB and CH chondrites reflect their distinct metal-to-silicate ratios. CR metal exhibits the same Mo isotopic composition as CB and CH metal, but CR silicates have distinct Mo and Ti isotopic compositions compared to CB and CH silicates, indicating that CB/CH chondrites may be genetically related to CR metal, but not to CR silicates. Together, the new isotopic data are consistent with formation of CB and CH chondrites in different regions of a common impact-generated vapor- melt plume and suggest that the CB and CH metal may derive from a metal-rich precursor genetically linked to CR chondrites. The Hf-W systematics of CH and CB chondrites indicate that the impact occurred at 3.8 +- 0.8 Ma after the formation of Ca-Al-rich inclusions and, hence, up to ~1 Ma earlier than previously inferred based on Pb- Pb chronology.

astro-ph.EP↗

arXiv2023

Origin of isotopic diversity among carbonaceous chondrites

Carbonaceous chondrites are some of the most primitive meteorites and derive from planetesimals that formed a few million years after the beginning of the solar system. Here, using new and previously published Cr, Ti, and Te isotopic data, we show that carbonaceous chondrites exhibit correlated isotopic variations that can be accounted for by mixing among three major constituents having distinct isotopic compositions, namely refractory inclusions, chondrules, and CI chondrite-like matrix. The abundances of refractory inclusions and chondrules are coupled and systematically decrease with increasing amount of matrix. We propose that these correlated abundance variations reflect trapping of chondrule precursors, including refractory inclusions, in a pressure maximum in the disk, which is likely related to the water ice line and the ultimate formation location of Jupiter. The variable abundance of refractory inclusions/chondrules relative to matrix is the result of their distinct aerodynamical properties resulting in differential delivery rates and their preferential incorporation into chondrite parent bodies during the streaming instability, consistent with the early formation of matrix-poor and the later accretion of matrix-rich carbonaceous chondrites. Our results suggest that chondrules formed locally from isotopically heterogeneous dust aggregates which themselves derive from a wide area of the disk, implying that dust enrichment in a pressure trap was an important step to facilitate the accretion of carbonaceous chondrite parent bodies or, more generally, planetesimals in the outer solar system.

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