Chemical dispersion among Apollo 15 olivine-normative mare basaltsAnalysis of Apollo 15 olivine-normative mare basalts for major and minor elements suggests that the hypothesis that the coarser-grained varieties (olivine microgabbros) consist of two chemical groups is incorrect. Instead, it is found that there is a single group including vesicular, coarse-grained, and fine-grained basalts. For the entire suite, the dispersion of compositions along the olivine trend is too great to be explained by short-range unmixing of an unfractionated flow. It is suggested that the general trend for the suite is olivine separation, probably through crystal settling. The textures, mineralogical characteristics, and chemical variation of the olivine-normative basalts are shown to be consistent with a sequence of thin fractionating flows, all from a common parent.
Document ID
19890023498
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Ryder, Graham (Lunar and Planetary Institute Houston, TX, United States)
Steele, Alison (Lunar and Planetary Institute, Houston, TX; Acadia University Wolfville, Canada)