Magma source transition of lunar mare volcanism at 2.3Ga

作者：Kato Shinsuke^*; Morota Tomokatsu; Yamaguchi Yasushi; Watanabe Sei ichiro; Otake Hisashi; Ohtake Makiko

来源：Meteoritics & Planetary Science, 2017, 52(9): 1899-1915.

DOI：10.1111/maps.12896

Mare basalts provide insights into the composition and thermal history of the lunar mantle. The ages of mare basalts suggest a first peak of magma activity at 3.2-3.8Ga and a second peak at similar to 2Ga. In this study, we reassess the correlation between the titanium contents and the eruption ages of mare basalt units using the compositional and chronological data updated by SELENE (Kaguya). Using morphological and geological criteria, we calculated the titanium content of 261 mare units across a representative area of each mare unit. In the Procellarum KREEP Terrane, where the latest eruptions are located, an increase in the mean titanium content is observed during the Eratosthenian period, as reported by previous studies. We found that the increase in the mean titanium content occurred within a relatively short period near approximately 2.3Ga, suggesting that the magma source of the mare basalts changed at this particular age. Moreover, the high-titanium basaltic eruptions are correlated with a second peak in volcanic activity near similar to 2Ga. The high-titanium basaltic eruptions occurring during the last volcanic activity period can be explained by the three possible scenarios (1) the ilmenite-bearing cumulate rich layer in the core-mantle boundary formed after the mantle overturn, (2) the basaltic material layers beneath the lunar crust formed through upwelling magmas, and (3) ilmenite-bearing cumulate blocks remained in the upper mantle after the mantle overturn.

• 出版日期2017-9