Boulder 1, Station 2, Apollo 17 - Petrology and petrogenesis
The clasts and matrices of Boulder 1, Station 2 are investigated by petrographic and microprobe methods. The boulder is shown to consist of two separate entities: an older metamorphosed breccia containing a diverse lithic clast population, and a friable matrix containing KREEPy basalts. It is suggested that the friable matrix was created in the Serenitatis event in a cool upper portion of the ejecta blanket and that the clasts were created in an earlier impact event. These results are shown to indicate that the Serenitatis event is younger than 4.01 billion years and that the lunar crust had a complex and varied history of magmatism, metamorphism, and brecciation in the interval between the origin of the moon and the assembly of the boulder.