Massive layer of pure anorthosite on the Moon

• Published in: Geophysical research letters Vol. 39; no. 13; pp. np - n/a
• Main Authors: Yamamoto, S., Nakamura, R., Matsunaga, T., Ogawa, Y., Ishihara, Y., Morota, T., Hirata, N., Ohtake, M., Hiroi, T., Yokota, Y., Haruyama, J.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.07.2012; American Geophysical Union
• Subjects: Anorthosite; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geophysics; Lunar crust; lunar magma ocean; Magma; Moon; Oceans; Onboard; Rock; North Pole; polar regions; Arctic region; nesosilicates; terrains; thickness; Moon; abundance; surveys; global; igneous rocks; magmas; olivine; Mixed layer; lunar crust; materials; anorthosite; plutonic rocks; silicates; Polar region; Pan; Diameter
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2012GL052098

We present a new global survey of the purest anorthosite (PAN) rock using the Spectral Profiler onboard Kaguya. We found that PAN rocks are widely distributed over the Moon, including the Feldspathic Highland Terrain and the south and north polar regions. All PAN sites are associated with huge impact structures with diameters larger than 100 km. Based on the global distributions of PAN and olivine‐rich sites, we propose the existence of a massive PAN layer with a thickness of ∼50 km below an uppermost mafic‐rich mixed layer with a thickness of ∼10 km. Below the PAN layer, a lower crustal layer with olivine‐rich materials may be present on the nearside, but not on the far side of the Moon. The existence of a PAN layer with a thickness of ∼50 km suggests an Al2O3 abundance of 33 to 34 wt.% in the lunar crust, which is higher than previous estimates of <32 wt.%. Our data indicate the massive production event of PAN during the early stage of the formation of the Moon, supporting the lunar magma ocean scenario. Key Points The existence of a massive layer of pure anorthosite on the Moon Massive production of pure anorthosite produced during the lunar magma ocean Dichotomy of lunar lower crust