Clast assemblages of possible deep-seated /77517/ and immiscible-melt /77538/ origins in Apollo 17 brecciasBreccia samples 77517 and 77538 are composed of abundant mineral and lithic clasts set in porous, poorly sintered matrices. Clast assemblages in the two rocks are of contrasting composition and origin. Breccia 77517 has Mg-rich olivine and pyroxene and calcic plagioclase clasts, indicating limited, almost exclusively ANT-suite parentage. A significant feature is the presence of an assemblage (aluminous enstatite, forsterite, anorthite, aluminous spinel) corresponding to spinel cataclasite, a rock type of deep-seated (about 60 km) crustal origin. Breccia 77538 contains Fe-rich pyroxene and rather sodic plagioclase clasts, indicative of predominantly KREEP and/or mare derivation. An important feature is the occurrence of high-K and high-Fe lithic clasts whose compositions resemble those of immiscible-melts produced during late-stage magmatic crystallization, and which probably originated via silicate liquid immiscibility in a KREEP or mare basalt magma. Both rocks contain numerous fine-grained breccia clasts which represent material that has been modified by impact processes at or very near the moon's surface.
Document ID
19790055138
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Warner, R. D. (New Mexico Univ. Albuquerque, NM, United States)
Taylor, G. J. (New Mexico Univ. Albuquerque, NM, United States)
Mansker, W. L. (New Mexico Univ. Albuquerque, NM, United States)
Keil, K. (New Mexico, University Albuquerque, N. Mex., United States)