HR: 1340h
AN: V43B-1376    [Abstracts]
TI: Upper Crustal Abundances of Trace Elements: A revision and update
AU: * Hu, Z
EM: zchu@vip.sina.com
AF: State Key Laboratory of Geological Processes and Mineral Resources, Faculty of earth sciences, China University of Geosciences, No. 388 Lumo Road, Wuhan, HB 430074, China
AU: Gao, S
EM: sgao@263.net
AF: State Key Laboratory of Geological Processes and Mineral Resources, Faculty of earth sciences, China University of Geosciences, No. 388 Lumo Road, Wuhan, HB 430074, China
AU: Gao, S
EM: sgao@263.net
AF: State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 229 North Taibai Avenue, Xi'an, SX 710069, China
AB: We report new estimates of abundances of rarely analyzed elements (Be, B, Ge, As, Mo, Cd, In, Sn, Sb, Te, W, Tl, Bi) in the upper continental crust based on precise analysis by ICP-MS of well-characterized upper crustal samples (shales, pelites, loess, graywackes, granitoids and their composites) from Australia, China, Europe, New Zealand and North American. Abundances of Li, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Nb, Cs, Er, Tm, Yb, Lu, Ta, and U are also given, which show variations of >50% in previous estimates. Our new esitmate is mainly based on significant (r>0.78) inter-element correlations observed in the clastic sediments and sedimentary rocks we studied and from previous studies, which yield the following elemental ratios in the upper continental crust: La/Nb=2.68, La/Ta=33.73, Nb/Ta=12.70, Zr/Hf=36.23, Al₂O₃/Ga=8280, Ga/In=280, Th/Sn=43.38, Th/Rb=0.109, Rb/Cs=19.20, Rb/Tl=0.548, Th/Be=5.42, Rb/Be=50.24, Rb/Ge=72.07, Rb/W=66.40, Be/Bi=8.68, W/Bi=6.24, La/U=11.72, Fe₂O₃/Sc=4070, Fe₂O₃/Co=4030, Fe₂O₃/V=558, Fe₂O₃/Cr=804, Fe₂O₃/Ni=1880, Fe₂O₃/Cu=2180, Fe₂O₃/Zn=794, V/Sc=7.65, V/Co=6.97, Co/Cr=0.202, Co/Ni=0.433, Ni/Cr=0.458, In/Li=0.00168, B/Te=1758, Er/Tm=6.31, Er/Yb=0.986 and Er/Lu=6.46. Given the well-known upper crustal abundances of La (31 ppm), Th (10.5 ppm), Al₂O₃ (15.40%) and Fe₂O₃ (5.92%), these ratios lead to upper crustal abundances of Nb=11.6 ppm, Ta=0.92 ppm, Ga=18.34 ppm, In=0.066 ppm, Sn=2.28 ppm, Rb=94 ppm, Cs=4.92 ppm, Tl=0.53 ppm, Be=1.92 ppm, Ge=1.31 ppm, W=1.42 ppm, Bi=0.23 ppm, U=2.65 ppm, Sc=13.9 ppm, Co=14.7 ppm, V=106 ppm, Cu=27.2 ppm, Zn=74.6 ppm, Ni=34.0 ppm, Cr=72.8 ppm, Li=39 ppm, Te=0.019 ppm. No significant correlations exist between As, Sb, Mo, Cd, B and Te and other elements in the clastic sediments and sedimentary rocks. We thus calculate abundances of these elements by assuming the upper continental crust consists of 65% granitoid rocks plus 35% clastic sedimentary rocks. The validity of this assumption is supported by back- calculated upper crustal SiO₂, Al₂O₃, La and Th abundances, which are identical to the values of Rudnick and Gao (2003). We thus estimate upper crustal abundances of As=3.41 ppm, Sb=0.46 ppm, Mo=0.57 ppm, Cd=0.062 ppm, B=31.5 ppm and Te=0.018 ppm. We also suggest a ~20% increase in Tm, Yb and Lu abundances (i.e., 0.365 ppm Tm, 2.34 ppm Yb and 0.356 ppm Lu) compared to those of Rudnick and Gao (2003).
DE: 1020 Composition of the continental crust
DE: 8400 VOLCANOLOGY
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting