Apollo 15 Mg- and Fe-norites - A redefinition of the Mg-suite differentiation trendThe Apollo 15 highland rocks from the Apennine Front include clasts of mafic plutonic rocks from deep in the lunar crust that were brought to the surface by the Imbrium and Serenitatis impacts. The Apollo 15 norites exhibit wide variations in mineral and bulk compositions and include Fe-norites that plot between the three major pristine rock fields on a diagram of Mg' in mafic minerals vs An in paglioclase. Based on assemblages and compositions of minerals, and on ratios of elemental abundances, it is concluded that these Apollo 15 Fe-norites are differentiated members of the Mg-norite suite. The Apollo 15 and 17 norites and troctolites form a closely related suite of rocks, whose variations in mineral compositions represent the main differentiation trend of the Mg-suite. This trend in mineral compositions has a steeper slope than the previous Mg-suite field. The parent magmas for these Mg-suite rocks formed by partial melting deep in the lunar mantle. Differentiation by fractional crystallization may also have included assimilation of crustal components as the magmas rose from the mantle and crystallized plutons in the lower crust.
Document ID
19890049134
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Lindstrom, M. M. (NASA Johnson Space Center Houston, TX, United States)
Marvin, U. B. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Mittlefehldt, D. W. (Lockheed Engineering and Science Co. Houston, TX, United States)