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Open Access

Subsurface Chemistry of the Imbrium Basin Inferred from Clementine UVVIS Spectroscopy

Earth, Planets and Space200658:BF03352649

Received: 18 March 2005

Accepted: 9 June 2006

Published: 25 December 2006


Since ejecta around an impact crater is excavated from a depth, its mineralogy and chemistry will provide us with information on the composition of the pre-impact subsurface. The depth from which crater ejecta were excavated was determined from laboratory experiments, field studies, and a simplified quantitative model (Z-model and the scaling law of ejection velocity). Based on the results of these studies, it is believed that surface material of an ejecta blanket between 1.1 and 1.5 radii from the crater was excavated from a depth of 0.13 to 0.15 radii. The following results were obtained from combining the surface and subsurface basalt distributions with crater-counting ages for the mare basalt, we obtained the following results: (1) The averages of TiO2 and FeO increased with time from the Imbrian to the Eratosthenian periods, which is represented by a continuous trend curve on the TiO2-FeO graph: (2) volcanic activities in Mare Imbrium drastically decreased and basalts changed from a low-Ti to high-Ti content around the transition of the Imbrian to Eratosthenian period: (3) basalts with less than 3 wt% TiO2 erupted in succession mainly in the Imbrian period.

Key words

Imbrium basinsubsurfaceejectaagevolcanism