TY - JOUR
T1 - The Fe/S ratio of pyrrhotite group sulfides in chondrites
T2 - An indicator of oxidation and implications for return samples from asteroids Ryugu and Bennu
AU - Schrader, Devin L.
AU - Davidson, Jemma
AU - McCoy, Timothy J.
AU - Zega, Thomas J.
AU - Russell, Sara S.
AU - Domanik, Kenneth J.
AU - King, Ashley J.
N1 - Funding Information:
For supplying the samples that were necessary for this work, the authors would like to thank the Smithsonian Institution, NASA/NSF, the National Institute of Polar Research (NiPR), the Arizona State University Center for Meteorite Studies, the Natural History Museum London, and the Institut für Planetologie. US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program, which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center. We are grateful to Axel Wittmann for assistance with the EPMA at ASU and Laurence Garvie for sample preparation. We are also grateful to Emma Bullock, two anonymous reviewers, and Associate Editor Anders Meibom, whose constructive comments improved the quality of the manuscript. We acknowledge the use of facilities within the Eyring Materials Center at Arizona State University supported in part by NNCI-ECCS-1542160. This work was funded by NASA grant NNX17AE53G (PI: DLS, CoI: TJZ) and STFC grant no. ST/R000727/1.
Funding Information:
For supplying the samples that were necessary for this work, the authors would like to thank the Smithsonian Institution, NASA/NSF, the National Institute of Polar Research (NiPR), the Arizona State University Center for Meteorite Studies, the Natural History Museum London, and the Institut für Planetologie. US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program, which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center. We are grateful to Axel Wittmann for assistance with the EPMA at ASU and Laurence Garvie for sample preparation. We are also grateful to Emma Bullock, two anonymous reviewers, and Associate Editor Anders Meibom, whose constructive comments improved the quality of the manuscript. We acknowledge the use of facilities within the Eyring Materials Center at Arizona State University supported in part by NNCI-ECCS-1542160. This work was funded by NASA grant NNX17AE53G (PI: DLS, CoI: TJZ) and STFC grant no. ST/R000727/1.
Publisher Copyright:
© 2021 The Author(s)
PY - 2021/6/15
Y1 - 2021/6/15
N2 - Determining compositional trends among individual minerals is key to understanding the thermodynamic conditions under which they formed and altered, and is also essential to maximizing the scientific value of small extraterrestrial samples, including returned samples and meteorites. Here we report the chemical compositions of Fe-sulfides, focusing on the pyrrhotite-group sulfides, which are ubiquitous in chondrites and are sensitive indicators of formation and alteration conditions in the protoplanetary disk and in small Solar System bodies. Our data show that while there are trends with the at.% Fe/S ratio of pyrrhotite with thermal and aqueous alteration in some meteorite groups, there is a universal trend between the Fe/S ratio and degree of oxidation. Relatively reducing conditions led to the formation of troilite during: (1) chondrule formation in the protoplanetary disk (i.e., pristine chondrites) and (2) parent body thermal alteration (i.e., LL4 to LL6, CR1, CM, and CY chondrites). Oxidizing and sulfidizing conditions led to the formation of Fe-depleted pyrrhotite with low Fe/S ratios during: (1) aqueous alteration (i.e., CM and CI chondrites), and (2) thermal alteration (i.e., CK and R chondrites). The presence of troilite in highly aqueously altered carbonaceous chondrites (e.g., CY, CR1, and some CM chondrites) indicates they were heated after aqueous alteration. The presence of troilite, Fe-depleted pyrrhotite, or pyrite in a chondrite can provide an estimate of the oxygen and sulfur fugacities at which it was formed or altered. The data reported here can be used to estimate the oxygen fugacity of formation and potentially the aqueous and/or thermal histories of sulfides in extraterrestrial samples, including those returned by the Hayabusa2 mission and due to be returned by the OSIRIS-REx mission in the near future.
AB - Determining compositional trends among individual minerals is key to understanding the thermodynamic conditions under which they formed and altered, and is also essential to maximizing the scientific value of small extraterrestrial samples, including returned samples and meteorites. Here we report the chemical compositions of Fe-sulfides, focusing on the pyrrhotite-group sulfides, which are ubiquitous in chondrites and are sensitive indicators of formation and alteration conditions in the protoplanetary disk and in small Solar System bodies. Our data show that while there are trends with the at.% Fe/S ratio of pyrrhotite with thermal and aqueous alteration in some meteorite groups, there is a universal trend between the Fe/S ratio and degree of oxidation. Relatively reducing conditions led to the formation of troilite during: (1) chondrule formation in the protoplanetary disk (i.e., pristine chondrites) and (2) parent body thermal alteration (i.e., LL4 to LL6, CR1, CM, and CY chondrites). Oxidizing and sulfidizing conditions led to the formation of Fe-depleted pyrrhotite with low Fe/S ratios during: (1) aqueous alteration (i.e., CM and CI chondrites), and (2) thermal alteration (i.e., CK and R chondrites). The presence of troilite in highly aqueously altered carbonaceous chondrites (e.g., CY, CR1, and some CM chondrites) indicates they were heated after aqueous alteration. The presence of troilite, Fe-depleted pyrrhotite, or pyrite in a chondrite can provide an estimate of the oxygen and sulfur fugacities at which it was formed or altered. The data reported here can be used to estimate the oxygen fugacity of formation and potentially the aqueous and/or thermal histories of sulfides in extraterrestrial samples, including those returned by the Hayabusa2 mission and due to be returned by the OSIRIS-REx mission in the near future.
KW - Asteroid sample return
KW - Chondrite
KW - Oxidation
KW - Pyrite
KW - Pyrrhotite
KW - Sulfide
KW - Troilite
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U2 - 10.1016/j.gca.2021.03.019
DO - 10.1016/j.gca.2021.03.019
M3 - Article
AN - SCOPUS:85107085928
SN - 0016-7037
VL - 303
SP - 66
EP - 91
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -