Feldspathic granulitic impactites and pre-final bombardment lunar evolutionIt is suggested that feldspathic granulitic impactites, which are characterized by a high model plagioclase content of between 70 and 80%, all formed in the period after consolidation of the lunar crust and before the final bombardment. The granulitic impactites contain essentially no KREEP component, which suggests that KREEP appeared on the lunar surface mostly after the formation of the granulitic impactites, at about the start of the final bombardment. The granulite metamorphism indicated by the matrix textures of these samples requires 1000 C temperatures for prolonged periods of time. The apparent sequence of formation is granulitic impactites before the final bombardment, crystalline-matrix breccias during the final bombardment, and vitric-matrix breccias after the final bombardment. The sequence is consistent with a described thermal model of breccia lithification and with characteristics of the decay of the meteorite flux rate.
Document ID
19780057765
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Warner, J. L. (San Francisco State Univ. CA, United States)
Phinney, W. C. (NASA Johnson Space Center Houston, Tex., United States)
Bickel, C. E. (San Francisco State University San Francisco, Calif., United States)
Simonds, C. H. (Lunar and Planetary Institute Houston, Tex., United States)