Trace Element Geochemistry and the Early Lunar Differentiation

摘要

Convection cells in the early lunar magma ocean suggest a laterally inhomogeneous crust. In general, mineralogy and petrology of samples may be relatively insensitive to which cell they evolved in since major and minor element concentrations would not be expected to vary greatly from cell to cell. It is established that, although most samples are local material, a few samples are fragments of projectiles that excavated secondary craters and that they are exotic--i.e. originated in different cell--to their present locations. Thus caution must be exercised in genetically relating samples found at a given site. Ru and Os have been fractionated from one another and also partitioned in the stratigraphic column resulting from the differentiation of the early lunar magma ocean. Lithic breccias contain two types of fractionated Ru-Os which appear to be related to near-surface crustal stratigraphy. Basalts contain fractionated Ru-Os which is correlated with their depths of origin. These are based on the ages of extrusion which are time related to the depths at which melting occurred. (ERA citation 02:046758)