Ages of Crystalline Rocks from Fra Mauro

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Science  24 Sep 1971:
Vol. 173, Issue 4003, pp. 1235-1236
DOI: 10.1126/science.173.4003.1235


Crystallization ages for six rocks from Fra Mauro have been measured by the argon-40-argon-39 method. All six rocks give an age of 3.77 ± 0.15 x 109 years, which is the same as for fragmental rocks from this site. It is concluded that the Imbrium event and the crystallization of a significant portion of the pre-Imbrian basalts were essentially contemporaneous.