TY - JOUR
T1 - Synchronising rock clocks of Mars' history: Resolving the shergottite 40Ar/39Ar age paradox
AU - Cohen, Benjamin E.
AU - Mark, Darren D.
AU - Cassata, William S.
AU - Kalnins, Lara M.
AU - Lee, Martin R.
AU - Smith, Caroline L.
AU - Shuster, David L.
N1 - Funding Information:
We thank the Natural History Museum London and the Johnson Space Centre for the provision of shergottite samples. R. Dymock and J. Imlach (SUERC) assisted with 40Ar/39Ar, and Josh Wimpenny (LLNL) with ICP-MS analyses. We thank Jörg Fritz for discussions on shock metamorphism, Fred Jourdan and anonymous referees for reviews. This work was funded by the UK Science and Technology Facilities Council (grants ST/H002960/1, and ST/K000918/1 to D.F.M. and M.R.L.). W.S.C. was supported by the NASA Mars Fundamental Research Program (grant NNH14AX56I) and an LLNL Laboratory Directed Research and Development project (20-LW-008). Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. L.M.K. is supported by a Royal Society of Edinburgh Personal Research Fellowship funded by the Scottish Government. D.L.S. was supported by the Ann and Gordon Getty Foundation. NERC are thanked for continued funding of the Argon Isotope Facility at SUERC. The project was developed by B.E.C. D.F.M. and M.R.L.; samples were selected by C.L.S. D.F.M. D.L.S. and W.S.C.; samples were prepared by B.E.C. D.L.S. and W.S.C.; analyses and 40Ar/39Ar data interpretation were undertaken by B.E.C. W.S.C. D.F.M. and D.L.S.; the thermal models and code for isotope correlation diagrams were prepared by L.M.K.; and manuscript prepared by B.E.C. and D.F.M. with contributions from all authors.
Funding Information:
We thank the Natural History Museum London and the Johnson Space Centre for the provision of shergottite samples. R. Dymock and J. Imlach (SUERC) assisted with 40 Ar/ 39 Ar, and Josh Wimpenny (LLNL) with ICP-MS analyses. We thank Jörg Fritz for discussions on shock metamorphism, Fred Jourdan and anonymous referees for reviews. This work was funded by the UK Science and Technology Facilities Council (grants ST/H002960/1 , and ST/K000918/1 to D.F.M. and M.R.L.). W.S.C. was supported by the NASA Mars Fundamental Research Program (grant NNH14AX56I ) and an LLNL Laboratory Directed Research and Development project ( 20-LW-008) . Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 . L.M.K. is supported by a Royal Society of Edinburgh Personal Research Fellowship funded by the Scottish Government . D.L.S. was supported by the Ann and Gordon Getty Foundation . NERC are thanked for continued funding of the Argon Isotope Facility at SUERC. The project was developed by B.E.C., D.F.M., and M.R.L.; samples were selected by C.L.S., D.F.M., D.L.S., and W.S.C.; samples were prepared by B.E.C., D.L.S., and W.S.C.; analyses and 40 Ar/ 39 Ar data interpretation were undertaken by B.E.C., W.S.C., D.F.M., and D.L.S.; the thermal models and code for isotope correlation diagrams were prepared by L.M.K.; and manuscript prepared by B.E.C. and D.F.M. with contributions from all authors.
Publisher Copyright:
© 2023 The Author(s)
PY - 2023/11/1
Y1 - 2023/11/1
N2 - The shergottites are the most abundant and diverse group of Martian meteorites and provide unique insights into the mafic volcanic and igneous history of Mars. Their ages, however, remain a source of debate. Different radioisotopic chronometers, including 40Ar/39Ar, have yielded discordant ages, leading to conflicting interpretations on whether the shergottites originate from young (mostly <700 Ma) or ancient (>4,000 Ma) Martian volcanoes. To address this issue, we have undertaken an 40Ar/39Ar investigation of seven shergottite meteorites utilizing an innovative approach to correcting data for cosmogenic isotope production and resolution of initial trapped components which, crucially, do not require assumptions concerning the sample's geologic context. Our data yield statistically robust 40Ar/39Ar isochron ages ranging from 161 ± 9 Ma to 540 ± 63 Ma (2σ), synchronous with the U-Pb, Rb-Sr, and Sm-Nd ages for the respective meteorites. These data indicate that, despite experiencing shock metamorphism, the shergottites were sourced from the youngest volcanoes on Mars.
AB - The shergottites are the most abundant and diverse group of Martian meteorites and provide unique insights into the mafic volcanic and igneous history of Mars. Their ages, however, remain a source of debate. Different radioisotopic chronometers, including 40Ar/39Ar, have yielded discordant ages, leading to conflicting interpretations on whether the shergottites originate from young (mostly <700 Ma) or ancient (>4,000 Ma) Martian volcanoes. To address this issue, we have undertaken an 40Ar/39Ar investigation of seven shergottite meteorites utilizing an innovative approach to correcting data for cosmogenic isotope production and resolution of initial trapped components which, crucially, do not require assumptions concerning the sample's geologic context. Our data yield statistically robust 40Ar/39Ar isochron ages ranging from 161 ± 9 Ma to 540 ± 63 Ma (2σ), synchronous with the U-Pb, Rb-Sr, and Sm-Nd ages for the respective meteorites. These data indicate that, despite experiencing shock metamorphism, the shergottites were sourced from the youngest volcanoes on Mars.
U2 - 10.1016/j.epsl.2023.118373
DO - 10.1016/j.epsl.2023.118373
M3 - Article
SN - 0012-821X
VL - 621
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
M1 - 118373
ER -