Crust composition

Altered oceanic crust composition based on Staudigel et al. (1996)... 

Wanke-Dreibus Mars mantle + crust composition... 

Mars bulk silicate (mantle + crust) composition, estimated from Martian meteorites by Wanke and Dreibus (1988). This composition differs from the bulk silicate of Earth, because of differences in volatile element abundances and core differentiation. 

This chapter reviews the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of the continental crust composition for the formation of the continents. Earth differentiation, and its geochemical inventories. 

In this chapter we review the composition of the upper, middle, and lower continental crust (Sections 3.01.2 and 3.01.3). We then examine the bulk crust composition and the implications of this composition for crust generation and modification processes (Sections 3.01.4 and 3.01.5). Finally, we compare the Earth s crust with those of the other terrestrial planets in our solar system (Section 3.01.6) and speculate about what unique processes on Earth have given rise to this unusual crustal distribution. 

The next major undertakings in determining upper-crust composition from large-scale surface... 

Figure 5 Comparison of REE patterns between (a) average post-Archean shales and loess and (b) various estimates of the upper continental crust composition. PA AS = post-Archean Australian Shale (Taylor and McLennan, 1985) NASC = North American shale composite (Haskin et al., 1966) ES = European shale composite (Haskin and Haskin, 1966) ECPAS = Eastern China post-Archean shale (Gao et al., 1998a). The loess range includes samples from China, Spitsbergen, Argentina, and France (Gallet et al., 1998 Jahn et al., 2001).

For the insoluble transition metals chromium, cobalt, and nickel, McLennan s (2001b) recent evaluation suggests approximate factor of 2 increases in average upper crustal values over those of Taylor and McLennan (1985). Taylor and McLennan s (1985) values were taken from a variety of sources (see Table 1 of Taylor and McLennan, 1981) and are similar to the Canadian Shield averages, which appear to represent a more felsic upper-crust composition, as discussed above. Even after eliminating these lower values, 30-40% variation exists for chromium, cobalt, and nickel between different estimates (Table 2 and Figure 3), and the upper cmstal concentrations of these elements remains poorly constrained relative to REE. 

Figure 13 Comparison of different models of the trace-element composition of the lower continental crust. All values normalized to the lower-crust composition of Rudnick and Fountain (1995), which is adopted here as the best estimate of the global lower crust. Gray-shaded field represents 30% variation from this value. Trace elements are divided into the following groups (a) transition metals, (b) high-field strength elements, (c) alkali, alkaline earth, and...

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