Mantle enrichment

Rabinowicz M, Ceuleneer G, Monnereau M, Rosemberg C (1990) Three-dimensional models of mantle flow across a low-viscosity zone implications for hotspot dynamics. Earth Planet Sci Lett 99 170-184 Reid MR(1995) Processes of mantle enrichment and magmatic differentiation in the eastern Snake River Plain Th isotope evidence. Earth Planet Sci Lett, 131 239-254 Reid MR, Ramos FC (1996) Chemical dynamics of enriched mantle in the southwestern United States Thorium isotope evidence. Earth Planet Sci Lett, 138 67-81. 

If continental peridotite xenoliths are divided into cratonic and noncratonic compositions, the vast majority of highly enriched neodymium isotope compositions originate in cratonic mantle and very few are evident in noncratonic mantle. Enriched neodymium isotope compositions can also be found in mantle sampled by orogenic peridotites (Reisberg and Zindler, 1986 Pearson et ai, 1993 Chapter 2.04) but not the extreme values evident in cratonic CLM. This is expected, given the great antiquity of cratonic CLM. Further subdivision of cratonic samples (Figure 37) shows... 

Vaselli O., Downes H., Thirwall M. F., Dobosi G., Coradossi N., Seghedi L, Szakacs A., and Vannucci R. (1995) Ultramafic xenoliths in Plio-pleistocene alkali basalts from the eastern Transylvanian Basin depleted mantle enriched by vein metasomatism. J. Petrol. 36, 23 —53. 

Exley R. A. and Smith J. V. (1982) The role of apatite in mantle enrichment processes and in the petrogenesis of some alkali basalt suites. Geochim. Cosmochim. Acta 46, 1375-1384. 

USA new constraints on mantle enrichment processes. Earth Planet. Set Lett. 119, 495-509. 

Figure 5.13 Discrimination diagram for basalts based upon K.-Ta covariations and using Yb as a normalizing factor (after Pearce, 1982). The diagram shows the Belds of volcanic-arc basalts (VAB), MORB and within-plate basalts (WPB). Volcanic-arc basalts are subdivided into tholeiitic (Thol), calc-alkaline (CA) and shos honitic (Sho) varieties. MORB and within-plate basalts are subdivided into tholeiitic (Thol), transitional (Trans) and alkaline (Aik) varieties. Alkaline volcanic-arc basalts also plot in the alkaline held. The plotting coordinates, shown at the margin of the diagram, are extracted from Pearce (1982 — Figure 6). The solid arrows indicate the direction of mantle depletion (D) mantle enrichment (E) and enrichment via a fluid phase (F).

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