@article{56aa4ef11cf04e58b781cc5765d21fc4,
title = "Pb-Pb ages of feldspathic clasts in two Apollo 14 breccia samples",
abstract = "Pb-Pb isochron ages of ca. 3.92 Ga for three K-feldspar-rich clasts from Apollo 14 breccias 14303 and 14083 were determined using Secondary Ion Mass Spectrometry (SIMS). These ages are interpreted to represent the resetting of the U-Pb system in the clasts as a result of brecciation during the Imbrium impact. One of the clasts contains zircon grains that record a significantly older crystallization age (ca. 4.33–4.35 Ga) for the rock represented by that clast. Initial Pb compositions determined for the clasts, combined with the previously measured Pb isotopic compositions of K-feldspar grains from several Apollo 14 breccia samples, constrain a range of initial Pb compositions in the ca. 3.9 Ga Fra Mauro formation at the Apollo 14 landing site. This range in initial Pb compositions indicates that the rocks represented by these clasts, or the sources of those rocks, evolved with a high 238U/204Pb (μ-value) for substantial periods of time, although the precise crystallization ages of the rocks represented by at least two of the clasts investigated here are unknown.",
keywords = "Age, Imbrium, Lunar breccia, Pb-isotopes",
author = "Nemchin, {A. A.} and H. Jeon and Bellucci, {J. J.} and Timms, {N. E.} and Snape, {J. F.} and Kilburn, {M. R.} and Whitehouse, {M. J.}",
note = "Funding Information: We appreciate critical comments of Ian Williams, James Connelly and anonymous reviewer, which helped to focus and improve the manuscript. The authors thank the astronauts of Apollo 14 for risking their lives to collect the samples. This work was funded by grants from the Knut and Alice Wallenberg Foundation and the Swedish Research Council to MJW and AAN and the Australian Research Council to AAN. The research has made use of NASA{\textquoteright}s Astrophysics Data System. The CAMECA IMS1280 at the University of Western Australia is a flagship of the Australian Microscopy & Microanalysis Research Facility (AMMRF), a facility funded by the University, State and Commonwealth Governments. The authors would also like to acknowledge the Australian Microscopy & Microanalysis Research Facility, AuScope, the Science and Industry Endowment Fund, and the State Government of Western Australian for contributing to the Ion Probe Facility at the Centre for Microscopy, Characterisation and Analysis at the University of Western Australia. Publisher Copyright: {\textcopyright} 2017 Elsevier Ltd",
year = "2017",
month = nov,
day = "15",
doi = "10.1016/j.gca.2017.08.024",
language = "English",
volume = "217",
pages = "441--461",
journal = "Geochimica Et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier BV",
}