Chemical and isotopic constraints on the petrogenesis of the large mare basalt clast in breccia 15459Results are presented that demonstrate that the large mare basalt clast in Apollo 15 breccia 15459 may represent one or more independent magma types. The complex nonequilibrium pyroxene and plagioclase compositions and relatively abundant mesostasis suggest that the 15459 clast is not a slowly cooled crystal cumulate. The addition of about 40 percent olivine to an olivine-normative basalt parental magma is found to be necessary to explain the high MgO abundances of picritic basalts by the accumulation of olivine in the magma. The present clast has a slightly younger age and a slightly higher Sr-87/Sr-86 ratio than most Apollo 15 basalts.
Document ID
19890049128
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Nyquist, L. (NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Lindstrom, M. (NASA Johnson Space Center Houston, TX, United States)
Bansal, B. (NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Mittlefehldt, D. (NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Shih, C.-Y. (Lockheed Engineering and Science Co. Houston, TX, United States)