Formation age of lunar Lalande crater and its implications for the source region of the KREEP-rich meteorite Sayh al Uhaymir 169
Formation age of lunar Lalande crater and its implications for the source region of the KREEP-rich meteorite Sayh al Uhaymir 169
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DOI：
10.1016/j.icarus.2022.115166
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发表时间：
2022-07
期刊：
影响因子：
3.2
通讯作者：
Luyuan Xu;L. Qiao;M. Xie;Yunhua Wu
中科院分区：
文献类型：
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作者：
Luyuan Xu;L. Qiao;M. Xie;Yunhua Wu
Sayh al Uhaymir（SaU）169陨石是KREEP最丰富的月球样品，如果能够确定其源区，将为KREEP和月球早期演化提供更多有价值的信息。以前的研究提出拉朗德陨石坑作为源区，对应于2.8 Ga的影响事件记录在SaU 169，而这种联系是高度依赖于潜在的源陨石坑的年龄测定。通过对叠加在拉兰德喷出物毯上的陨石坑进行计数，并对这些叠加陨石坑被拉兰德喷出物掩埋的过程进行建模，我们发现拉兰德周围的陨石坑统计数据受到直径大于~170 m的前拉兰德陨石坑的存在的严重影响，这可能导致拉兰德陨石坑的年龄被大大高估。考虑到这一影响，我们得到拉朗德陨石坑是一个哥白尼陨石坑，形成年龄为410 ± 20 Ma，而邻近的月海玄武岩单元的年龄为3.8−0.06+0.04Ga。拉朗德陨石坑的形成年龄与SaU 169中记录的任何放射性同位素年龄都不一致，表明拉朗德陨石坑不太可能是这颗月球陨石的源区。
As the most KREEP-rich lunar sample, the Sayh al Uhaymir (SaU) 169 meteorite would provide more valuable information concerning the KREEP and early lunar evolution of the Moon if its source regions can be pinpointed. Previous studies proposed Lalande crater as the source region that corresponds to the impact event of ~2.8 Ga recorded in SaU 169, whereas this linkage is highly dependent on the age determination of the potential source crater. By counting craters superposed on the ejecta blankets of Lalande and modelling the burial process of these superposed craters by Lalande's ejecta, we find that the crater statistics around Lalande are heavily influenced by the existing of pre-Lalande craters larger than ~170 m in diameter, which could lead to a largely overestimated age of Lalande crater. After taking this influence into consideration, we obtain that Lalande crater is a Copernican crater with a formation age of 410 ± 20 Ma, and the adjacent mare basalts unit has an Imbrian age of 3.8−0.06+0.04Ga. The formation age of Lalande crater is inconsistent with any of the radio-isotopic ages recorded in SaU 169, indicating that Lalande crater is unlikely to be the source region of this lunar meteorite.