¹R. T. Pidgeon, ¹R. E. Merle, ¹M. L. Grange, ^1,2A. A. Nemchin,²M. J. Whitehouse
¹Department of Applied Geology, Curtin University, Perth, Western Australia, Australia
²Swedish Museum of Natural History, Stockholm, Sweden

Impact breccia 14311, was collected from the Apollo 14 landing site as a potential sample of the underlying Fra Mauro Formation. Published zircon U-Pb ages of >4000 Ma date the source material of the breccia and the apatite U-Pb age of ~3940 Ma is interpreted as dating thermal resetting of the apatite U-Pb systems. In this contribution we present new age information on the late stage thermal history of the breccia based on the annealing of radiation damage in the zircons. From Raman spectroscopic determination of the radiation damage within SIMS analytical spots on the zircons and the U and Th concentrations determined on these spots, we demonstrate that the radiation damage in the zircons has been annealed and we estimate the age of annealing at 3410 ± 80 Ma. This age is interpreted as a cooling age following heating of the breccia to above the annealing temperature of ~230 °C for stage 1 radiation damage in zircon, but below the temperature needed to reset the U-Pb system of apatite (~500 °C). It is proposed that this thermal event was associated with the prolonged period of Mare volcanism, from 3150 to 3750 Ma, that generated massive basalt flows in the vicinity of the sample location.

Reference
Pidgeon RT, Merle RE, Grange ML, Nemchin AA, Whitehouse MJ (2015) Annealing of radiation damage in zircons from Apollo 14 impact breccia 14311: Implications for the thermal history of the breccia.
Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12572]
Published by arrangement with John Wiley & Sons

^1,2Hiroshi Nagaoka, ³Yuzuru Karouji, ⁴Hiroshi Takeda, ⁵Timothy J. Fagan, ⁶Mitsuru Ebihara, ^1,2Nobuyuki Hasebe
¹Research Institute for Science and Engineering, Waseda University, Shinjuku 169-8555, Tokyo, Japan
²School of Advanced Science and Engineering, Waseda University, Shinjuku 169-8555, Tokyo, Japan
³Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara 252-5210, Kanagawa, Japan
⁴Department of Earth and Planetary Science, University of Tokyo, Hongo 113-0033, Tokyo, Japan
⁵Department of Earth Science School of Education, Waseda University, Shinjuku 169-8050, Tokyo, Japan
⁶Department of Chemistry, Tokyo Metropolitan University, Hachioji 192-0397, Tokyo, Japan

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Reference
Nagaoka H, Karouji Y, Takeda H, Fagan TJ, Ebihara M, Hasebe N (2015)
Mineralogy and petrology of lunar meteorite Northwest Africa 2977 consisting of olivine cumulate gabbro including inverted pigeonite. Earth, Planets and Space 67, 200

Link to Article [doi:10.1186/s40623-015-0368-y]