title: Ages of crystalline rocks from fra mauro.
abstract: 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 10(9) 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.
authors.forename: L
authors.initials: L
authors.lastname: Husain
authors.forename: J F
authors.initials: JF
authors.lastname: Sutter
authors.forename: O A
authors.initials: OA
authors.lastname: Schaeffer