Silica activity in lunar lavasCalculated values of log alpha SiO2 in lunar magmas range from approximately -0.8 to unity in the temperature range of 1100-1300 C. High-titanium mare basalts begin crystallizing at silica activities insufficient for orthopyroxene saturation; in contrast to terrestrial lavas, silica activities rise substantially with crystallization and cause silica saturation in the residuum. Igneous rocks of the highland regions have relatively higher initial silica activities than mare basalts. Thermodynamic calculations indicate that high-titanium mare basalts could be derived from a 90 to 240-km deep source region containing olivine and orthopyroxene in addition to other phases.
Document ID
19780062700
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Nash, W. P. (Utah Univ. Salt Lake City, UT, United States)
Haselton, J. D. (Utah, University Salt Lake City, Utah, United States)