An unusual clast in lunar meteorite MacAlpine Hills 88105: A unique lunar sample or projectile debris?
Article first published online: 26 FEB 2014
© The Meteoritical Society, 2014.
Meteoritics & Planetary Science
Volume 49, Issue 4, pages 677–695, April 2014
How to Cite
Joy, K. H., Crawford, I. A., Huss, G. R., Nagashima, K. and Taylor, G. J. (2014), An unusual clast in lunar meteorite MacAlpine Hills 88105: A unique lunar sample or projectile debris?. Meteoritics & Planetary Science, 49: 677–695. doi: 10.1111/maps.12270
- Issue published online: 18 APR 2014
- Article first published online: 26 FEB 2014
- Manuscript Accepted: 10 JAN 2014
- Manuscript Received: 18 MAY 2013
- Leverhulme Trust. Grant Numbers: F/07 112/P, 2011-569
Lunar meteorite MacAlpine Hills (MAC) 88105 is a well-studied feldspathic regolith breccia dominated by rock and mineral fragments from the lunar highlands. Thin section MAC 88105,159 contains a small rock fragment, 400 × 350 μm in size, which is compositionally anomalous compared with other MAC 88105 lithic components. The clast is composed of olivine and plagioclase with minor pyroxene and interstitial devitrified glass component. It is magnesian, akin to samples in the lunar High Mg-Suite, and also alkali-rich, akin to samples in the lunar High Alkali Suite. It could represent a small fragment of late-stage interstitial melt from an Mg-Suite parent lithology. However, olivine and pyroxene in the clast have Fe/Mn ratios and minor element concentrations that are different from known types of lunar lithologies. As Fe/Mn ratios are notably indicative of planetary origin, the clast could either (1) have a unique lunar magmatic source, or (2) have a nonlunar origin (i.e., consist of achondritic meteorite debris that survived delivery to the lunar surface). Both hypotheses are considered and discussed.