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Refractory elements 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. [Pg.587]

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. [Pg.715]

The constancy of refractory element ratios in the Earth s mantle, discussed before, is documented in the most primitive samples from the Earth s mantle. Figure 8 plots (modified from Jochum et ai, 1989) the PM-normalized abundances of 21 refractory elements from four fertile spinel Iherzolites. These four samples closely approach, in their bulk chemical composition, the primitive upper mantle as defined in the previous section. The patterns of most of the REEs (up to praseodymium) and of titanium, zirconium, and yttrium are essentially flat. The three... [Pg.726]

The distribution of lithophile trace elements (REE + mbidium, caesium, strontium, barium, yttrium, zirconium, hafnium, niobium, tantalum, thorium, and uranium) normalized to primitive mantle (PM) values are illustrated in Figure 16 for a range of peridotite lithologies from the Ronda orogenic Iherzolite massif, and in Figure 17 for ophiolitic and abyssal refractory peridotites. [Pg.834]

If the fertile mantle protolith to oceanic and subcontinental mantle is nonchondritic in refractory elements, and if the bulk silicate Earth is chondritic in refractory elements, then a complimentary reservoir must exist elsewhere, presumably buried in the deep lower mantle and isolated from mantle convection (e.g., Anderson, 1989 Kellogg et al., 1999 Albarede and van der HUst, 1999). The primitive upper mantle could have acquired a superchondritic ratio as a consequence of crystal fractionation in a magma ocean, or perhaps by extraction of an early crust with low CaO/AbOs. [Pg.1077]

As refractory lithophile elements, the REE play an important role in constraining the overall composition and history of the silicate fraction of planets, which for the terrestrial planets is also termed their primitive mantle (equivalent to the present-day crust plus mantle). Since there is no evidence for significant planetary-scale fractionation of refractory elements during the assembly and differentiation of planetary bodies, it is widely accepted that the primitive mantles of terrestrial planets and moon possess chondritic proportions of the REE. As such, the absolute concentrations of REE (and other refractory elements) in primitive mantles provide an important constraint on the proportions of volatile elements to refractory elements and on the oxidation state (i.e., metal/silicate ratio) of the body. To date, the only major planetary bodies for which REE data are directly available are the Earth, Moon, and Mars, and Taylor and McLennan" recently reviewed these data. [Pg.9]

The inclusion of the subjects covered in Volume 1 of this Treatise illustrates the recognition that one critical avenue to understanding geo chemistry is to understand the solar environment in which Earth formed. Chapter 2.01 of this volume compares the composition of Earth with that of various primitive meteorite classes and with the spectroscopically determined composition of the Sun. Chemical variability in these meteorites reflects primarily two processes (i) volatility and (u) affinity for metal (the so-called siderophile elements) over silicate (lithophile elements). Perhaps the most surprising outcome of this comparison is that Earth s mantle has a bulk composition that is close to solar, at least for refractory lithophile elements. As detailed in Chapter 2.01, the mantle s most obvious departures from solar composition are its deficiencies in volatile and siderophile elements. The latter is easily understood in that Earth has a large metallic core that extracted the missing siderophile elements from the mantle (Chapter 2.15). [Pg.603]


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Mantle

Primitive element

Primitives

Refractory mantle

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