McLennan(2000)‚Ι‚ζ‚ιkwRelationships between the trace element composition of sedimentary rocks and upper continental crustxi20-21•Ε‚߁jl

wAbstract
@Estimates of average composition of various Precambrian shields and a variety of estimates of the average composition of upper continental crust show considerable disagreement for a number of trace elements, including Ti,Nb, Ta, Cs, Cr, Ni, V, and Co. For these elements and others that are carried predominantly in terrigenous sediment, rather than in solution (and ultimately into chemical sediment), during the erosion of continents the La/element ratio is relatively uniform in clastic sediments. Since the average rare earth element (REE) pattern of terrigenous sediment is widely accepted to reflect the upper continental crust, such correlations provide robust estimates of upper crustal abundances for these trace elements directly from the sedimentary data. Suggested revisions to the upper crustal abundance of Taylor and McLennan(1985) are as follows (all in parts per million): Sc=13.6, Ti=4100, V=107, Cr=83, Co=17, Ni=44, Nb=12, Cs=4.6, Ta=1.0, and Pb=17. The upper crustal abundances of Rb, Zr, Ba, Hf, and Th were also directly reevaluated and K, U, and Rb indirectly evaluated (by assuming Th/U, K/U, and K/Rb ratios), and no revisions are warranted for these elements. In the models of crustal composition proposed by Taylor and McLennan(1985) the lower continental crust (75“ of the entire crust) is determined by subtraction of the upper crust (25“) from a model composition for the bulk crust, and accordingly, these changes also necessitate revisions to lower crustal abundances for these elements.

Keywords: Geochemistry; Composition of the crust; Trace elementsx

1. Introduction
2. Comparison of upper crustal estimates
3. Sedimentary rocks and upper crustal compositions
@3.1. Cs in the upper crust
@3.2. Nb-Ta-Ti in the upper crust
@3.3. Cr-Ni-V-Co in the upper crust
4. Methods
@4.1. Database
@@4.1.1. Shales, muds, and loess (fine grain)
@@4.1.2. Sand and sandstones (coarse grain)
@4.2. Approach
5. Results
@5.1. REE, Th, and Sc
@5.2. Rb and Cs
@5.3. Nb, Ta, and Ti
@5.4. Ferromagnesian trace elements (Cr, Ni, V, and Co)
@5.5. Other elements (Zr, Hf, Ba, and Pb)
6. Discussion
@6.1. Some comparisons
@6.2. Implications for the bulk continental crust and lower crust

w
Table 5. Composition of the continental crust revised from Taylor and McLennan(1985)
Œ³‘f–Ό ’PˆΚ γ•”’nŠk ‘S’nŠk ‰Ί•”’nŠk
Li

ppm
 20 13 11
Be ppm 3.0 1.5 1.0
B ppm 15 10 8.3
Na wt“ 2.89 2.30 2.08
Mg wt“ 1.33 3.20 3.80
Al wt“ 8.04 8.41 8.52
Si wt“ 30.8 26.8 25.4
P ppm 700 c c
K wt“ 2.80 1.1a 0.53a
Ca wt“ 3.00 5.29 6.07
Sc ppm 13.6b 30 35b
Ti wt“ 0.41b 0.54 0.58b
V ppm 107b 230 271b
Cr ppm 83b 185 219b
Mn ppm 600 1400 1700
Fe wt“ 3.50 7.07 8.24
Co ppm 17b 29 33b
Ni ppm 44b 128 156b
Cu ppm 25 75 90
Zn ppm 71 80 83
Ga ppm 17 18 18
Ge ppm 1.6 1.6 1.6
As ppm 1.5 1.0 0.8
Se ppm 50 50 50
Rb ppm 112 37c 12c
Sr ppm 350 260 230
Y ppm 22 20 19
Zr ppm 190 100 70
Nb ppm 12b 8.0b 6.7b
Mo ppm 1.5 1.0 0.8
Pd ppb 0.5 1 1
Ag ppb 50 80 90
Cd ppb 98 98 98
In ppb 50 50 50
Sn ppm 5.5 2.5 1.5
Sb ppm 0.2 0.2 0.2
Cs ppm 4.6c 1.5c 0.47c
Ba ppm 550 250 150
La ppm 30 16 11
Ce ppm 64 33 23
Pr ppm 7.1 3.9 2.8
Nd ppm 26 16 12.7
Sm ppm 4.5 3.5 3.17
Eu ppm 0.88 1.1 1.17
Gd ppm 3.8 3.3 3.13
Tb ppm 0.64 0.60 0.59
Dy ppm 3.5 3.7 3.6
Ho ppm 0.80 0.78 0.77
Er ppm 2.3 2.2 2.2
Tm ppm 0.33 0.32 0.32
Yb ppm 2.2 2.2 2.2
Lu ppm 0.32 0.30 0.29
Hf ppm 5.8 3.0 2.1
Ta ppm 1.0b 0.8b 0.73b
W ppm 2.0 1.0 0.7
Re ppb 0.4 0.4 0.4
Os ppb 0.05 0.05 0.05
Ir ppb 0.02 0.1 0.13
Au ppb 1.8 3.0 3.4
Tl ppb 750 360 230
Pb ppm 17b 8.0 5.0b
Bi ppb 127 60 38
Th ppm 10.7 4.2a 2.0a
U ppm 2.8 1.1a 0.53a
aRevisions suggested by McLennan and Taylor(1996).
bRevisions suggested in this study.
cRevisions discussed in this study and by McLennan et al.(2001).
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Acknowledgments
References

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