Compositional Range of Primary Magmas Observed Among the Apollo 17 Orange Volcanic Glasses (74220)

In addition to being a primary magma from the lunar mantle, the Apollo 17 orange volcanic glasses are the best-sampled deposit of a lunar fire-fountain. As a continuation of previous work, additional analyses of high-Ti, volcanic glass spherules handpicked from soil sample 74220,680 have been made by electron microprobe in order to acquire more information about processes associated with melt generation and melt eruption on the Moon. The present work has developed microprobe procedures for making high-precision analyses of the major- (Si, Ti, Al, Fe, Mg, Ca) and minor- (Cr, Mn) elements. The JEOL 733 electron microprobe was operated at a 15-keV accelerating potential with a counting time of 300-seconds per element per analysis at a beam current of 75 nanoamps. One homogeneous spherule of Apollo 17 orange volcanic glass was used as a working standard throughout the investigation to assess analytical precision and to fine-tune the calibration.