Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology

Gaffney, A M; Borg, L E; Asmerom, Y

Title: Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology

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Abstract

Shock and thermal metamorphism of meteorites from differentiated bodies such as the Moon and Mars have the potential to disturb chronometric information contained in these meteorites. In order to understand the impact-related mechanisms and extent of disturbance to isochrons, we undertook experiments to shock and heat samples of 10017, a 3.6 billion year old lunar basalt. One sub-sample was shocked to 55 GPa, a second subsample was heated to 1000 C for one week, and a third sub-sample was maintained as a control sample. Of the isotope systems analyzed, the Sm-Nd system was the least disturbed by shock or heat, followed by the Rb-Sr system. Ages represented by the {sup 238}U-{sup 206}Pb isotope system were degraded by shock and destroyed with heating. In no case did either shock or heating alone result in rotated or reset isochrons that represent a spurious age. In some cases the true crystallization age of the sample was preserved, and in other cases age information was degraded or destroyed. Although our results show that neither shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptiblemore »« less

Authors:: Gaffney, A M; Borg, L E; Asmerom, Y

Publication Date:: Wed Dec 10 00:00:00 EST 2008

Research Org.:: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1019058

Report Number(s):: LLNL-JRNL-409386
TRN: US201114%%603

DOE Contract Number:: W-7405-ENG-48

Resource Type:: Journal Article

Journal Name:: Meteoritics and Planetary Science, vol. 46, n/a, January 1, 2011, pp. 35-52

Additional Journal Information:: Journal Volume: 46

Country of Publication:: United States

Language:: English

Subject:: 79 ASTRONOMY AND ASTROPHYSICS; 58 GEOSCIENCES; BASALT; CRYSTALLIZATION; DISTURBANCES; HEATING; METAMORPHISM; METEORITES

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                    Gaffney, A M, Borg, L E, and Asmerom, Y. Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology.  United States: N. p., 2008. 
        Web.

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                    Gaffney, A M, Borg, L E, & Asmerom, Y. Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology.  United States.

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                    Gaffney, A M, Borg, L E, and Asmerom, Y. 2008.  
        "Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology".  United States.  https://www.osti.gov/servlets/purl/1019058.

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@article{osti_1019058,

  title        = {Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology},

  author       = {Gaffney, A M and Borg, L E and Asmerom, Y},

  abstractNote = {Shock and thermal metamorphism of meteorites from differentiated bodies such as the Moon and Mars have the potential to disturb chronometric information contained in these meteorites. In order to understand the impact-related mechanisms and extent of disturbance to isochrons, we undertook experiments to shock and heat samples of 10017, a 3.6 billion year old lunar basalt. One sub-sample was shocked to 55 GPa, a second subsample was heated to 1000 C for one week, and a third sub-sample was maintained as a control sample. Of the isotope systems analyzed, the Sm-Nd system was the least disturbed by shock or heat, followed by the Rb-Sr system. Ages represented by the {sup 238}U-{sup 206}Pb isotope system were degraded by shock and destroyed with heating. In no case did either shock or heating alone result in rotated or reset isochrons that represent a spurious age. In some cases the true crystallization age of the sample was preserved, and in other cases age information was degraded or destroyed. Although our results show that neither shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptible than unshocked material to subsequent disturbance during impact-related heating or aqueous alteration on Mars or Earth. The combination of these processes may result in the disparate chronometric information preserved in some meteorites.},

  doi          = {},

  url          = {https://www.osti.gov/biblio/1019058},
  journal      = {Meteoritics and Planetary Science, vol. 46, n/a, January 1, 2011, pp. 35-52},
number       = ,

  volume       = 46,

  place        = {United States},

  year         = {Wed Dec 10 00:00:00 EST 2008},

  month        = {Wed Dec 10 00:00:00 EST 2008}

}

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