Basalts and gabbros from Mare Crisium - Evidence for extreme fractional crystallizationPetrographic and electron microprobe techniques were used to examine igneous fragments in Luna 24 samples 24088 and 24105. It is the complex chemistry of the pyroxenes that distinguishes the different rock types. Basaltic pyroxenes exhibit an Fe-enrichment trend; the evolutionary trends are more complex in the gabbros, with enrichments in both Fe and Ti and a depletion in Cr. These chemical evolutionary trends are displayed by a progressive variation in rock types from Mg-rich olivine-gabbro to olivine-gabbro, and to ferrogabbro and ferrotroctolite. The low TiO2 content of the primary melt, possibly represented by the least-evolved Mg-rich olivine-gabbro, retarded the formation of early ilmenite and spinel, such that 'Fenner Trend' Fe enrichment occurred. The ferrotroctolite is probably the end product of chemical evolution by extreme fractional crystallization, controlled primarily by olivine and pyroxene crystallization.
Document ID
19890049131
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Lu, F. (Tennessee Univ. Knoxville, TN, United States)
Taylor, L. A. (Tennessee Univ. Knoxville, TN, United States)
Jin, Y. (Tennessee, University Knoxville, United States)