Geochemistry enrichment-depletion

Keywords geochemistry, Rudny Altai, depletion, enrichment, anomaly... 

Goldberg, I.S., Abramson, G.J., Los, V.L. 2003. Depletion and enrichment of primary haloes their importance in the genesis of and exploration for mineral deposits Geochemistry. Exploration, Environment, Analysis, 3, 281-293. 

Dixon et al. (2002) take this approach one step further, and use new data on water contents, trace element and isotope geochemistry of Atlantic basalts to argue that mantle endmember reservoirs or components, previously defined on the basis of their isotope geochemistry, have different water contents. They propose that depleted MORE mantle (DMM) has 100 ppm H2O, FOZO ( focus zone component of Hart et al., 1992) has 750 ppm H2O, and enriched mantle (EM) has approximately half the H2O concentration as FOZO. 

Nd/ Nd low 8nneodymium isotopic compositions, the remarkable aspect of the frequency distribution for CLM as a whole is that the pronounced mode is within 58 units of bulk Earth and the mean 8j,jd value is 1.8. On this basis, the dominant neodymium isotopic characteristic of CLM is not enriched but is close to, or slightly more depleted than bulk Earth. Of course, if Depleted Mantle is used as a reference point then the CLM mode is enriched. The strontium isotope frequency distribution has a long tail out to very radiogenic ( enriched ) compositions but the mean Sr/ Sr is 0.7047 very close to estimates of bulk Earth. It is important to bear in mind that this statistical view of CLM geochemistry could... 

Figure 6.27 Cartoon diagram showing the difTerent crust and mande reservoirs and the possible relationships between them, based upon the observations of isotope geochemistry. The mande reservoirs are identified using the nomenclature of Zindler and Hart (1986) M, enriched mande DM, depleted mande MMU, mantle with high U/Pb ratio PMMA, prevalent mande PM, primitive mande.

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