Lunar apatite with terrestrial volatile abundances

• Published in: Nature (London) 2010-07, Vol.466 (7305), p.466-469
• Main Authors: Boyce, Jeremy W., Liu, Yang, Rossman, George R., Guan, Yunbin, Eiler, John M., Stolper, Edward M., Taylor, Lawrence A.
• Format: Article
• Language: English
• Subjects: 639/33/445/847; 704/2151/210; 704/2151/213; Alkalis; Apatite; Basalt; Carbon dioxide; Composition; Cosmochemistry. Extraterrestrial geology; Depletion; Earth sciences; Earth, ocean, space; Exact sciences and technology; Extraterrestrial geology; Geology; Glass; Humanities and Social Sciences; Identification and classification; Igneous rocks; Interstitials; letter; Lunar petrology; Mass spectrometry; Melts; Metamorphic; Mineralogy; Moon; multidisciplinary; Non silicates; Science; Science (multidisciplinary); Sulfides; Volatile organic compounds
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature09274

Earth-like lunar apatite It is thought that the lunar interior is deficient relative to the Earth in hydrogen, chlorine and other volatiles, due to near-complete degassing from the Moon-forming impact. New analyses of lunar basalt 14053, a much-studied sample collected by the Apollo 14 astronauts, suggest that portions of the lunar mantle or crust may be more volatile-rich than previously thought. Concentrations of hydrogen, chlorine and sulphur in the mineral apatite from 14053 are indistinguishable from apatites in common terrestrial igneous rocks. Measurements of apatites from other available lunar rock types will help to clarify the generality and significance of the terrestrial-like properties of this basalt. These authors report the concentrations of hydrogen, chlorine and sulphur in the mineral apatite from a lunar basalt, and show that the concentrations are indistinguishable from apatites in common terrestrial igneous rocks. They conclude that both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable materials within the Earth. The Moon is thought to be depleted relative to the Earth in volatile elements such as H, Cl and the alkalis 1 , 2 , 3 . Nevertheless, evidence for lunar explosive volcanism 4 , 5 has been used to infer that some lunar magmas exsolved a CO-rich and CO 2 -rich vapour phase before or during eruption 6 , 7 , 8 . Although there is also evidence for other volatile species on glass spherules 9 , until recently 10 there had been no unambiguous reports of indigenous H in lunar rocks. Here we report quantitative ion microprobe measurements of late-stage apatite from lunar basalt 14053 that document concentrations of H, Cl and S that are indistinguishable from apatites in common terrestrial igneous rocks. These volatile contents could reflect post-magmatic metamorphic volatile addition or growth from a late-stage, interstitial, sulphide-saturated melt that contained ∼1,600 parts per million H 2 O and ∼3,500 parts per million Cl. Both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable terrestrial materials. One possible implication is that portions of the lunar mantle or crust are more volatile-rich than previously thought.