Aluminum primitive mantle

More controversial (although sometimes cited as proven fact) have been claims (e.g., Taylor and Jakes, 1974 Taylor, 1982) that the bulk Moon is enriched roughly twofold in the cosmochemically refractory lithophile elements (a class that includes the REEs, the heat sources thorium and uranium, and the major elements aluminum, calcium, and titanium), and that compared to Earth s primitive mantle, the Moon s silicate mg ratio is much lower, i.e., its EeO concentration is much higher. Neither of these claims has been confirmed by recent lunar science developments, which include the advent of global thorium and samarium maps (Lawrence et al., 2002a Prettyman et al., 2002), data from lunar meteorites, and some radically changed interpretations of the Apollo seismic database. 

The two elements calcium and aluminum are RLEs. The assumption is usually made that aU RLEs are present in the primitive mantle of the Earth in chondritic proportions. Chondritic (undifferentiated) meteorites show significant variations in the absolute abundances of refractory elements but have, with few exceptions discussed below, the same relative abundances of lithophile and siderophile refractory elements. By analogy, the Earth s mantle abundances of refractory lithophile elements are assumed to occur in chondritic relative proportions in the primitive mantle, which is thus characterized by a single RLE/Mg ratio. This ratio is often normalized to the Cl-chondrite ratio and the resulting ratio, written as (RLE/Mg)N, is a measure of the concentration level of the refractory component in the Earth. A single factor of (RLE/Mg) valid for all RLEs is a basic assumption in this procedure and will be calculated from mass balance considerations. 

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