TY - JOUR
T1 - Trace element geochemistry of coarse-grained angrites from Northwest Africa
T2 - Implications for their petrogenesis on the angrite parent body
AU - Sanborn, Matthew E.
AU - Wadhwa, Meenakshi
N1 - Funding Information:
We thank Dr. Anthony Irving for providing us with polished sections and whole‐rock fragments of the NWA 2999, 4590, and 4801 angrites. We are grateful to Drs. Richard Hervig and Lynda Williams for their assistance with the Cameca IMS 6f SIMS measurements at ASU. We thank the two reviewers, Dr. Jon Friedrich and Dr. Amy Riches, for their detailed, constructive, and helpful feedback that greatly improved the manuscript, and the associate editor, Dr. Cyrena Goodrich for guiding the manuscript through the review process and providing additional feedback. This work was supported by NASA grant NNX15AH41G to M.W. and NASA Earth and Space Science Fellowship award NNX09AAQ94H to M.E.S./M.W. This document is approved for unlimited release through Los Alamos National Laboratory under LA‐UR‐20‐24003.
Funding Information:
We thank Dr. Anthony Irving for providing us with polished sections and whole-rock fragments of the NWA 2999, 4590, and 4801 angrites. We are grateful to Drs. Richard Hervig and Lynda Williams for their assistance with the Cameca IMS 6f SIMS measurements at ASU. We thank the two reviewers, Dr. Jon Friedrich and Dr. Amy Riches, for their detailed, constructive, and helpful feedback that greatly improved the manuscript, and the associate editor, Dr. Cyrena Goodrich for guiding the manuscript through the review process and providing additional feedback. This work was supported by NASA grant NNX15AH41G to M.W. and NASA Earth and Space Science Fellowship award NNX09AAQ94H to M.E.S./M.W. This document is approved for unlimited release through Los Alamos National Laboratory under LA-UR-20-24003.
Publisher Copyright:
© 2021 The Meteoritical Society (MET).
PY - 2021/3
Y1 - 2021/3
N2 - The angrites are a class of achondrites that encompass a wide range of igneous textures from quenched, volcanic, and subvolcanic stones to slowly cooled, plutonic rocks. The compositions of the various geochemical reservoirs generating this variety of rocks have not been investigated fully because historically the numbers and masses of angrites available for study have been quite small. However, the rapid increase in meteorites from Northwest Africa (NWA) has enabled a renewed opportunity for such an investigation. In particular, three samples, NWA 2999, 4590, and 4801, have provided a new window into our understanding of the origin and petrogenesis of the coarse-grained (plutonic) angrites. We report here the trace element abundances in individual mineral grains of pyroxene, plagioclase, olivine/kirschsteinite, and phosphate and in the whole-rock samples. We utilize these data to constrain the petrogenetic history of each of these samples on the angrite parent body (e.g., parental melt compositions and oxygen fugacity conditions) and assess genetic relationships to previously investigated angrites. The trace element abundances in each of the three coarse-grained angrites studied here indicate a unique history for each. The observed trace element abundances and patterns in NWA 2999 show similarities with previously studied fine-grained, volcanic angrites and potentially indicate a common geochemical source reservoir, even though NWA 2999 is temporally distinct from the volcanic angrites. In contrast, NWA 4590 has trace element characteristics analogous to other coarse-grained angrites (e.g., Lewis Cliff [LEW] 86010), suggesting that these samples originated from geochemically similar source reservoirs. The third angrite, NWA 4801, exhibits geochemical characteristics most similar to the plutonic, coarse-grained angrites, but also appears to have some affinities in its trace element characteristics to the volcanic, fine-grained angrites. This suggests that NWA 4801 may represent a petrogenetic link between two distinct geochemical reservoirs on the angrite parent body. In aggregate, the trace element distributions in these three plutonic angrites suggest that while they may have originated up to several million years after the fine-grained angrites, they sampled a range of source reservoirs on the angrite parent body. Some of these source reservoirs were likely similar to those of the fine-grained angrites, but others had distinct geochemical characteristics.
AB - The angrites are a class of achondrites that encompass a wide range of igneous textures from quenched, volcanic, and subvolcanic stones to slowly cooled, plutonic rocks. The compositions of the various geochemical reservoirs generating this variety of rocks have not been investigated fully because historically the numbers and masses of angrites available for study have been quite small. However, the rapid increase in meteorites from Northwest Africa (NWA) has enabled a renewed opportunity for such an investigation. In particular, three samples, NWA 2999, 4590, and 4801, have provided a new window into our understanding of the origin and petrogenesis of the coarse-grained (plutonic) angrites. We report here the trace element abundances in individual mineral grains of pyroxene, plagioclase, olivine/kirschsteinite, and phosphate and in the whole-rock samples. We utilize these data to constrain the petrogenetic history of each of these samples on the angrite parent body (e.g., parental melt compositions and oxygen fugacity conditions) and assess genetic relationships to previously investigated angrites. The trace element abundances in each of the three coarse-grained angrites studied here indicate a unique history for each. The observed trace element abundances and patterns in NWA 2999 show similarities with previously studied fine-grained, volcanic angrites and potentially indicate a common geochemical source reservoir, even though NWA 2999 is temporally distinct from the volcanic angrites. In contrast, NWA 4590 has trace element characteristics analogous to other coarse-grained angrites (e.g., Lewis Cliff [LEW] 86010), suggesting that these samples originated from geochemically similar source reservoirs. The third angrite, NWA 4801, exhibits geochemical characteristics most similar to the plutonic, coarse-grained angrites, but also appears to have some affinities in its trace element characteristics to the volcanic, fine-grained angrites. This suggests that NWA 4801 may represent a petrogenetic link between two distinct geochemical reservoirs on the angrite parent body. In aggregate, the trace element distributions in these three plutonic angrites suggest that while they may have originated up to several million years after the fine-grained angrites, they sampled a range of source reservoirs on the angrite parent body. Some of these source reservoirs were likely similar to those of the fine-grained angrites, but others had distinct geochemical characteristics.
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U2 - 10.1111/maps.13631
DO - 10.1111/maps.13631
M3 - Article
AN - SCOPUS:85101864240
SN - 1086-9379
VL - 56
SP - 482
EP - 499
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
IS - 3
ER -