Component mantle

Niu Y, Regelous M, Wendt IJ, Batiza R, O Hara MJ (2002) Geochemistry of near-EPR seamounts importance of somce versus process and the origin of emiched mantle component. Earth Planet Sei Lett 199 327-345... 

In the 143Nd/l44Nd vs 87Sr/86Sr plot, draw the mixing triangle at the 20 percent mesh size for a mixture of three mantle components, the depleted mantle (DM), the enriched mantle I (EM I) and the enriched mantle II (EM II). The isotopic ratios and relative concentrations of each component are listed in Table 1.10. 

Figure 1.9 A hypothetical hyperbolic triangle for the mixing of three mantle components in the sense of Zindler and Hart (1986). Data from Table 1.10.

Poreda RJ, Craig H (1992) He and Sr isotopes in the Lau Basin mantle Depleted and primitive mantle components. Earth Planet Sci Lett 113 487-493... 

The simple oxides regarded as possible lower mantle components have proved amenable to a number of approaches involving quantum-mechanical calculations. For both MgO and CaO, the bonding, equations of state, and relative stabilities of the NaCl-type (51) and the CsCl-type (52) structures have been calculated using both modified electron-gas studies... 

Niedermann S., Bach W., and Erzinger J. (1997) Noble gas evidence for a lower mantle component in MORBs from the southern East Pacific Rise decoupling of helium and neon isotope systematics. Geochim. Cosmochim. Acta 61, 2697-2715. 

Noble gases and nitrogen in martian meteorites reveal several interior components having isotopic compositions different from those of the atmosphere. Xenon, krypton, and probably argon in the mantle components have solar isotopic compositions, rather than those measured in chondrites. However, ratios of these noble gas abundances are strongly fractionated relative to solar abundances. This decoupling of elemental and isotopic fractionation is not understood. The interior ratio in martian meteorites is similar to chondrites. 

Farley K. A., Natland J. H., and Craig H. (1992) Binary mixing of enriched and undegassed (primitive ) mantle components (He, Sr, Nd, Pb) in Samoan lavas. Earth Planet. Set Lett. Ill, 183-199. 

Milner S. C. and le Roex A. P. (1996) Isotope characteristics of the Okenyena igneous complex, northwestern Namibia constraints on the composition of the early Tristan plume and the origin of the EM 1 mantle component. Earth Planet. Sci. Lett. 141, 277-291. 

In order to use noble gases as tracers for the involvement of different mantle components in a particular environment, the absolute... 

Marty B., Appora L, Barrat J. A. A., Deniel C., Vellutini P., and Vidal P. (1993) He, Ar, Sr, Nd, and Pb isotopes in volcanic rocks from Afar—evidence for a primitive mantle component and constraints on magmatic sources. Geochem. J. 27, 219-228. 

Richard D., Marty B., Chaussidon M., and Arndt N. (1996) Hehum isotopic evidence for a lower mantle component in depleted Archean komatiite. Science 273, 93-95. 

Figure 9 Examples of models proposed for the chemical structure of the terrestrial mantle, (a) Whole mantle convection with depletion of the entire mantle. Some subducted slabs pass through the transition zone to the coremantle boundary. Plumes arise from both the core-mantle boundary and the transition zone. This model is not in agreement with isotopic and chemical mass balances, (b) Two-layer mantle convection, with the depleted mantle above the 660 km transition zone and the lower mantle retaining a primitive composition, (c) Blob model mantle where regions of more primitive mantle are preserved within a variously depleted and enriched lower mantle, (d) Chemically layered mantle with lower third above the core comprising a heterogeneous mixture of enriched (mafic slabs) and more primitive mantle components, and the upper two-thirds of the mantle is depleted in incompatible elements (see text) (after Albarede and van der Hilst, 1999).

If the model outlined above is valid, sihcic magmatism in the LFB involved net crustal growth, as juvenile mantle-derived liquids, or their differentiates were instrumental in the formation and compositional evolution of hornblende granites, and, to a lesser extent, the cordierite granites. The amount of new crust generated is estimated by determining the overall mantle component present within both granitic types, and this is best done isotopically, since the trace-element ratios are poorly constrained for the potential basaltic end-members. 

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