Combined mass-dependent and nucleosynthetic isotope variations in refractory inclusions and their mineral separates to determine their original Fe isotope compositions

Quinn R. Shollenberger, Andreas Wittke, Jan Render, Prajkta Mane, Stephan Schuth, Stefan Weyer, Nikolaus Gussone, Meenakshi Wadhwa, Gregory A. Brennecka

Research output: Contribution to journalArticle

Abstract

Calcium-aluminum-rich inclusions (CAIs) are the oldest dated materials that provide crucial information about the isotopic reservoirs present in the early Solar System. For a variety of elements, CAIs have isotope compositions that are uniform yet distinct from later formed solid material. However, despite being the most abundant metal in the Solar System, the isotopic composition of Fe in CAIs is not well constrained. In an attempt to determine the Fe isotopic compositions of CAIs, we combine extensive work from a previously studied CAI sample set with new isotopic work characterizing mass-dependent and mass-independent (nucleosynthetic) signatures in Mg, Ca, and Fe. This investigation includes work on three mineral separates of the Allende CAI Egg 2. For all isotope systems investigated, we find that in general, fine-grained CAIs exhibit light mass-dependent isotopic signatures relative to terrestrial standards, whereas igneous CAIs have heavier isotopic compositions relative to the fine-grained CAIs. Importantly, the mass-dependent Fe isotope signatures of bulk CAIs show a range of both light (fine-grained CAIs) and heavy (igneous CAIs) isotopic signatures relative to bulk chondrites, suggesting that Fe isotope signatures in CAIs largely derive from mass fractionation events such as condensation and evaporation occurring in the nebula. Such signatures show that a significant portion of the secondary alteration experienced by CAIs, particularly prevalent in fine-grained inclusions, occurred in the nebula prior to accretion into their respective parent bodies. Regarding nucleosynthetic Fe isotope signatures, we do not observe any variation outside of analytical uncertainty in bulk CAIs compared to terrestrial standards. In contrast, all three Egg 2 mineral separates display resolved mass-independent excesses in 56Fe compared to terrestrial standards. Furthermore, we find that the combined mass-dependent and nucleosynthetic Fe isotopic compositions of the Egg 2 mineral separates are well correlated, likely indicating that Fe indigenous to the CAI is mixed with less anomalous Fe, presumably from the solar nebula. Thus, these reported nucleosynthetic anomalies may point in the direction of the original Fe isotope composition of the CAI-forming region, but they likely only provide a minimum isotopic difference between the original mass-independent Fe isotopic composition of CAIs and that of later formed solids.

Original languageEnglish (US)
Pages (from-to)215-234
Number of pages20
JournalGeochimica et Cosmochimica Acta
Volume263
DOIs
StatePublished - Oct 15 2019

Fingerprint

Isotopes
Aluminum
Refractory materials
Minerals
aluminum
calcium
isotope
Calcium
mineral
Chemical analysis
isotopic composition
Solar system
egg
solar system
parent body
Fractionation
chondrite
condensation

Keywords

  • Ca isotopes
  • CAIs
  • Early Solar System
  • Fe isotopes
  • Mass-dependent fractionation
  • Mg isotopes
  • Nucleosynthetic anomalies

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Combined mass-dependent and nucleosynthetic isotope variations in refractory inclusions and their mineral separates to determine their original Fe isotope compositions. / Shollenberger, Quinn R.; Wittke, Andreas; Render, Jan; Mane, Prajkta; Schuth, Stephan; Weyer, Stefan; Gussone, Nikolaus; Wadhwa, Meenakshi; Brennecka, Gregory A.

In: Geochimica et Cosmochimica Acta, Vol. 263, 15.10.2019, p. 215-234.

Research output: Contribution to journalArticle

Shollenberger, Quinn R. ; Wittke, Andreas ; Render, Jan ; Mane, Prajkta ; Schuth, Stephan ; Weyer, Stefan ; Gussone, Nikolaus ; Wadhwa, Meenakshi ; Brennecka, Gregory A. / Combined mass-dependent and nucleosynthetic isotope variations in refractory inclusions and their mineral separates to determine their original Fe isotope compositions. In: Geochimica et Cosmochimica Acta. 2019 ; Vol. 263. pp. 215-234.
@article{a613d94762e4488ab57452b00c052a91,
title = "Combined mass-dependent and nucleosynthetic isotope variations in refractory inclusions and their mineral separates to determine their original Fe isotope compositions",
abstract = "Calcium-aluminum-rich inclusions (CAIs) are the oldest dated materials that provide crucial information about the isotopic reservoirs present in the early Solar System. For a variety of elements, CAIs have isotope compositions that are uniform yet distinct from later formed solid material. However, despite being the most abundant metal in the Solar System, the isotopic composition of Fe in CAIs is not well constrained. In an attempt to determine the Fe isotopic compositions of CAIs, we combine extensive work from a previously studied CAI sample set with new isotopic work characterizing mass-dependent and mass-independent (nucleosynthetic) signatures in Mg, Ca, and Fe. This investigation includes work on three mineral separates of the Allende CAI Egg 2. For all isotope systems investigated, we find that in general, fine-grained CAIs exhibit light mass-dependent isotopic signatures relative to terrestrial standards, whereas igneous CAIs have heavier isotopic compositions relative to the fine-grained CAIs. Importantly, the mass-dependent Fe isotope signatures of bulk CAIs show a range of both light (fine-grained CAIs) and heavy (igneous CAIs) isotopic signatures relative to bulk chondrites, suggesting that Fe isotope signatures in CAIs largely derive from mass fractionation events such as condensation and evaporation occurring in the nebula. Such signatures show that a significant portion of the secondary alteration experienced by CAIs, particularly prevalent in fine-grained inclusions, occurred in the nebula prior to accretion into their respective parent bodies. Regarding nucleosynthetic Fe isotope signatures, we do not observe any variation outside of analytical uncertainty in bulk CAIs compared to terrestrial standards. In contrast, all three Egg 2 mineral separates display resolved mass-independent excesses in 56Fe compared to terrestrial standards. Furthermore, we find that the combined mass-dependent and nucleosynthetic Fe isotopic compositions of the Egg 2 mineral separates are well correlated, likely indicating that Fe indigenous to the CAI is mixed with less anomalous Fe, presumably from the solar nebula. Thus, these reported nucleosynthetic anomalies may point in the direction of the original Fe isotope composition of the CAI-forming region, but they likely only provide a minimum isotopic difference between the original mass-independent Fe isotopic composition of CAIs and that of later formed solids.",
keywords = "Ca isotopes, CAIs, Early Solar System, Fe isotopes, Mass-dependent fractionation, Mg isotopes, Nucleosynthetic anomalies",
author = "Shollenberger, {Quinn R.} and Andreas Wittke and Jan Render and Prajkta Mane and Stephan Schuth and Stefan Weyer and Nikolaus Gussone and Meenakshi Wadhwa and Brennecka, {Gregory A.}",
year = "2019",
month = "10",
day = "15",
doi = "10.1016/j.gca.2019.07.021",
language = "English (US)",
volume = "263",
pages = "215--234",
journal = "Geochmica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Combined mass-dependent and nucleosynthetic isotope variations in refractory inclusions and their mineral separates to determine their original Fe isotope compositions

AU - Shollenberger, Quinn R.

AU - Wittke, Andreas

AU - Render, Jan

AU - Mane, Prajkta

AU - Schuth, Stephan

AU - Weyer, Stefan

AU - Gussone, Nikolaus

AU - Wadhwa, Meenakshi

AU - Brennecka, Gregory A.

PY - 2019/10/15

Y1 - 2019/10/15

N2 - Calcium-aluminum-rich inclusions (CAIs) are the oldest dated materials that provide crucial information about the isotopic reservoirs present in the early Solar System. For a variety of elements, CAIs have isotope compositions that are uniform yet distinct from later formed solid material. However, despite being the most abundant metal in the Solar System, the isotopic composition of Fe in CAIs is not well constrained. In an attempt to determine the Fe isotopic compositions of CAIs, we combine extensive work from a previously studied CAI sample set with new isotopic work characterizing mass-dependent and mass-independent (nucleosynthetic) signatures in Mg, Ca, and Fe. This investigation includes work on three mineral separates of the Allende CAI Egg 2. For all isotope systems investigated, we find that in general, fine-grained CAIs exhibit light mass-dependent isotopic signatures relative to terrestrial standards, whereas igneous CAIs have heavier isotopic compositions relative to the fine-grained CAIs. Importantly, the mass-dependent Fe isotope signatures of bulk CAIs show a range of both light (fine-grained CAIs) and heavy (igneous CAIs) isotopic signatures relative to bulk chondrites, suggesting that Fe isotope signatures in CAIs largely derive from mass fractionation events such as condensation and evaporation occurring in the nebula. Such signatures show that a significant portion of the secondary alteration experienced by CAIs, particularly prevalent in fine-grained inclusions, occurred in the nebula prior to accretion into their respective parent bodies. Regarding nucleosynthetic Fe isotope signatures, we do not observe any variation outside of analytical uncertainty in bulk CAIs compared to terrestrial standards. In contrast, all three Egg 2 mineral separates display resolved mass-independent excesses in 56Fe compared to terrestrial standards. Furthermore, we find that the combined mass-dependent and nucleosynthetic Fe isotopic compositions of the Egg 2 mineral separates are well correlated, likely indicating that Fe indigenous to the CAI is mixed with less anomalous Fe, presumably from the solar nebula. Thus, these reported nucleosynthetic anomalies may point in the direction of the original Fe isotope composition of the CAI-forming region, but they likely only provide a minimum isotopic difference between the original mass-independent Fe isotopic composition of CAIs and that of later formed solids.

AB - Calcium-aluminum-rich inclusions (CAIs) are the oldest dated materials that provide crucial information about the isotopic reservoirs present in the early Solar System. For a variety of elements, CAIs have isotope compositions that are uniform yet distinct from later formed solid material. However, despite being the most abundant metal in the Solar System, the isotopic composition of Fe in CAIs is not well constrained. In an attempt to determine the Fe isotopic compositions of CAIs, we combine extensive work from a previously studied CAI sample set with new isotopic work characterizing mass-dependent and mass-independent (nucleosynthetic) signatures in Mg, Ca, and Fe. This investigation includes work on three mineral separates of the Allende CAI Egg 2. For all isotope systems investigated, we find that in general, fine-grained CAIs exhibit light mass-dependent isotopic signatures relative to terrestrial standards, whereas igneous CAIs have heavier isotopic compositions relative to the fine-grained CAIs. Importantly, the mass-dependent Fe isotope signatures of bulk CAIs show a range of both light (fine-grained CAIs) and heavy (igneous CAIs) isotopic signatures relative to bulk chondrites, suggesting that Fe isotope signatures in CAIs largely derive from mass fractionation events such as condensation and evaporation occurring in the nebula. Such signatures show that a significant portion of the secondary alteration experienced by CAIs, particularly prevalent in fine-grained inclusions, occurred in the nebula prior to accretion into their respective parent bodies. Regarding nucleosynthetic Fe isotope signatures, we do not observe any variation outside of analytical uncertainty in bulk CAIs compared to terrestrial standards. In contrast, all three Egg 2 mineral separates display resolved mass-independent excesses in 56Fe compared to terrestrial standards. Furthermore, we find that the combined mass-dependent and nucleosynthetic Fe isotopic compositions of the Egg 2 mineral separates are well correlated, likely indicating that Fe indigenous to the CAI is mixed with less anomalous Fe, presumably from the solar nebula. Thus, these reported nucleosynthetic anomalies may point in the direction of the original Fe isotope composition of the CAI-forming region, but they likely only provide a minimum isotopic difference between the original mass-independent Fe isotopic composition of CAIs and that of later formed solids.

KW - Ca isotopes

KW - CAIs

KW - Early Solar System

KW - Fe isotopes

KW - Mass-dependent fractionation

KW - Mg isotopes

KW - Nucleosynthetic anomalies

UR - http://www.scopus.com/inward/record.url?scp=85071829747&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85071829747&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2019.07.021

DO - 10.1016/j.gca.2019.07.021

M3 - Article

AN - SCOPUS:85071829747

VL - 263

SP - 215

EP - 234

JO - Geochmica et Cosmochimica Acta

JF - Geochmica et Cosmochimica Acta

SN - 0016-7037

ER -