Complex magmatic and impact history prior to 4.1 Ga recorded in zircon from Apollo 17 South Massif aphanitic breccia 73235
MetadataShow full item record
NOTICE: This is the author’s version of a work that was accepted for publication in Geochimica et Cosmochimica Acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Geochimica et Cosmochimica Acta [75, 8, 2011] DOI 10.1016/j.gca.2011.01.036
Sample 73235 is one of several aphanitic impact melt breccias collected by the Apollo 17 mission at stations 2 and 3 on the slopes of the South Massif. This study presents a detailed investigation of internal structures and U-Pb ages of large zircon grains from this breccia sample. New data combined with the results of previous studies of zircon grains from the same location indicate that most zircon clasts in breccias from stations 2 and 3 formed during multiple magmatic events between 4.37 and 4.31 Ga, although the oldest zircon crystallized at about 4.42 Ga and the youngest at 4.21 Ga. In addition, zircons from the aphanitic breccias record several impact events prior to the 3.9 Ga Late Heavy Bombardment.The results indicate that the zircons probably crystallized at different locations within the Procellarum KREEEP Terrane and were later excavated and modified by several impacts and delivered to the same locality within separate ejecta blankets. This locality became a source of material that formed the aphanitic impact melt breccias of the South Massif during a 3.9 Ga impact. However, the zircons, showing old impact features, are not modified by this 3.9 Ga impact event suggesting that (i) this common source area was located at the periphery of excavation cavity, and (ii) the > 3.9 Ga ages recorded by the zircon grains could date large (basin-forming) events as significant as major later (3.9 Ga) collisions such as Imbrium and Serenitatis.
Showing items related by title, author, creator and subject.
Merle, Renaud; Nemchin, Alexander; Whitehouse, M.; Pidgeon, Robert; Grange, Marion; Snape, J.; Thiessen, F. (2017)In this paper, we compare the U-Pb zircon age distribution pattern of sample 14311 from the Apollo 14 landing site with those from other breccias collected at the same landing site. Zircons in breccia 14311 show major age ...
Apollo 12 breccia 12013: Impact-induced partial Pb loss in zircon and its implications for lunar geochronologyThiessen, F.; Nemchin, Alexander; Snape, J.; Bellucci, J.; Whitehouse, M. (2018)Apollo 12 breccia 12013 is composed of two portions, one grey in colour, the other black. The grey portion of the breccia consists mainly of felsite thought to have formed during a single crystallisation event, while the ...
Grange, Marion; Nemchin, Alexander; Pidgeon, Robert; Timms, Nicholas Eric; Muhling, J.; Kennedy, Allen (2009)Lunar breccia 73217 is composed of plagioclase and pyroxene clasts originating from a single gabbronorite intrusion, mixed with a silica-rich glass interpreted to represent an impact melt. A study of accessory minerals ...