Trace elements lithosphere

Table 9.4. Trace element contents of the lithosphere and world soils (mg/kg) (Data from Han et al. 2002a, with kind permission of Springer Science and Business Media)...

Copper is found in the rocks and minerals of the earth s crust, occurring usually as sulfides and oxides, and sometimes as metallic copper (USEPA 1980). The mean concentration of copper in the upper lithosphere ranges from 70 to 100 mg/kg, ranking 14th among the trace elements in this... 

The variable isotopic compositions (especially for Pb) reveal geochemi-cally heterogeneous sources. The origin of this heterogeneity is debated and may derive either from shallow mantle processes, such as variable me-tasomatic modifications of the lithosphere by asthenospheric melts, or from mixing between a deep-mantle plume and asthenosphere-lithosphere material. Etna and Ustica show some trace element and isotopic characteristics (e.g. Rb/Nb, Ce/Pb, and boron isotopes), indicative of a contribution from subduction-derived components. 

Aluminum is the third most abundant element in the lithosphere, but its levels in natural waters, plants, and animals are relatively low [1], It occurs in a vast variety of oxide minerals and together with silicon forms the polymorphous aluminosilicates (Al205Si) in rocks and soils upon which all organisms depend [2]. In soils and sediments these clays have many functions they hold trace elements, permit growth of roots, sustain pH balance, and their cavities keep water available [3],... 

Jochum K. P., McDonough W. F., Pahne H., and Spettel B. (1989) Compositional constraints on the continental lithospheric mantle from trace elements in spinel peridotite xenoliths. Nature 340, 548-550. 

Saunders A. D., Norry M. J., and Tarney J. (1988) Origin of MORB and chemically-depleted mantle reservoirs trace element constraints. J. Petrol. (Special Lithosphere Issue), 415-445. 

Bodinier J.-L., Merlet C., Bedini R. M., Simien E., Remai di M., and Garrido C. J. (1996) Distribution of Nb, Ta, and other highly incompatible trace elements in the lithospheric mantle the spinel paradox. Geochim. Cosmochim. Acta 60, 545-550. 

Garrido C. J., Bodinier J.-L., and Alard O. (2000) Distribution of LILE, REE and HFSE in anhydrous spinel peridotite and websterite minerals from the Ronda massif insights into the nature of trace element reservoirs in the subcontinental lithospheric mantle. Earth Planet. Sci. Lett. 181, 341-358. 

Calculated bulk rock trace-element systematics of eclogites have wider implications for mantle recycling models and bulk silicate earth mass balance. The subchondritic Nb/Ta, Nb/La, and Ti/Zr of both continental cmst and depleted mantle require the existence of an additional reservoir with superchondritic ratios to complete the terrestrial mass balance. Rudnick et al. (2000) have shown that rutile-bearing eclogites from cratonic mantle have suitably superchondritic Nb/Ta, Nb/La, and Ti/Zr such that if this component formed 1 -6% by weight of the bulk silicate earth, this would resolve the mass imbalance. This mass fraction far exceeds the likely mass of eclogite in the continental lithosphere and so the material is proposed to reside in the lower mantle, possibly at the core-mantle boundary. 

Stosch H. G. and Lugmair G. W. (1986) Trace element and Sr and Nd isotope geochemistry of peridotite xenoliths from the Eifel (West Germany) and their bearing on the evolution of the sub-continental lithosphere. Earth Planet. Sci. Lett. 80, 281-298. 

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