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Constraining the Source Craters of Unbrecciated Lunar Mare Basalt Meteorites

  • Author / Creator
    Mijajlovic, Tatiana
  • MIL 05035, NWA 10597, NWA 8632, NWA 479 and NWA 4898 are all unbrecciated lunar mare basalt meteorites, interpreted to have individually experienced a single hypervelocity collision event that would have resulted in their ejection from the Moon. A comprehensive study of shock deformation and transformation effects constrain the upper and lower boundary limits of bulk shock pressures that would have been experienced during the ejection of each sample. Micro-Raman spectroscopy, electron imaging and optical properties were used characterize the structural state of calcic plagioclase (An80-90) within the meteorites, shock deformation and transformation in pyroxene and olivine, and the mineralogy and microtextures of shock melt within the samples. Confirmation of the partial or total amorphization of plagioclase feldspar to maskelynite constrains lower boundary ranges of 22 – 24 GPa for NWA 10597, 24 – 26 GPa for NWA 4898, and 25 – 27 GPa for MIL 05035, NWA 8632, and NWA 479. These pressures are associated with post-shock temperature increases < 200˚C. The shock deformation of olivine phenocrysts in the form of irregular fractures, weak mosaicism and planar fractures, accompanied by undulose extinction to weak mosaicism, and polysynthetic mechanical twinning of pyroxene phenocrysts constrain the upper limit of the shock pressure to 30 GPa for all five samples. High-pressure mineral investigations within the shock melt of the meteorites combined with Finite Element Heat Transfer (FEHT) modelling of cooling times provides constraints on the pressure-temperature-time history of each sample. This information then points the way for further determining the decay rate of the shock wave each sample experienced, the degree of adiabatic cooling involved in the post-shock environment and modelling the potential source crater diameters. These crater diameters in turn could be used as a potential parameter for constraining the geological unit from which these meteorites originated on the lunar surface.

  • Subjects / Keywords
  • Graduation date
    Fall 2023
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-0w5z-h679
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.