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Detailed Reference Information |
Marvin, U.B., Lindstrom, M.M., Bernatowicz, T.J., Podosek, F.A., Sugiura, N. and Sugiura, N. (1987). The composition and history of breccia 67015 from North Ray Crater. Journal of Geophysical Research 92. doi: 10.1029/JB092iB04p0E471. issn: 0148-0227. |
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We have examined feldspathic fragmental breccia 67015 from the rim of North Ray Crater and found it to be the most diverse and complex of the Apollo 16 FFBs. It contains a wider range of clast types than any of the others and is not dominated by any single lithology. We have identified several crystalline lithologies, occurring in minor amounts, that we believe represent highland plutonic rocks. Plagioclase fragments are the most abundant breccia constituent, followed by clasts of impact melt rocks and granulites. The impact melts are of two main types: feldspathic fragment-laden melts and mafic, KREEPy melt rocks of VHA basalt composition. Textural evidence indicates that some of the VHA melts were hot and plastic when they accumulated into the breccia. 40Ar-39Ar dates show that both types of melts solidified about 3.9¿109 years ago. Magnetic measurements on clasts show a scatter of NMR directions, making it impossible to read a consistent imprint of an ancient dipolar magnetic field. Previous studies of Apollo 16 stratigraphy suggested that KREEPy melt rocks were introduced to the site as Imbrium impact ejecta, about 3.8¿106 years ago. Our results indicate that the highlands crust contained KREEP components as early as 3.9¿109 years ago. ¿ American Geophysical Union 1987 |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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