Lanthanide abundances igneous rocks

Fig. 50. Both steep (KH21, YKl) and flatter (C-3, 8781) lanthanide abundance patterns are observed in Archean sedimentary rocks, and reflect derivation from felsic and basic igneous rocks, and lend weight to the suggestion that a tamodal mixing model best explains the provenance of Archean sedimentary rocks in greenstone belts. (Data are from table 30.)...

In the lanthanide series the Marker rule—even-numbered elements are more abundant than odd-numbered elements—is well exemplified in the following abbreviated sequence for abundance (g/tonne) in igneous rocks atomic number 57 (lanthanum, 18.3),atomic number 58(cerium, 46.1), atomic number 59 (praseodymium, 5.5) [11]. 

In the discussion of sedimentary rocks it was concluded that the relative lanthanide abundances in those rocks represented the average distributions of their igneous precursors. What are the distributions in igneous rocks Igneous rocks are those that form from high-temperature melts. 

The higher lanthanide concentrations and the light-lanthanide enrichment of average continental material relative to chondrites has been attributed to extraction of these elements from the mantle. A residue is left behind, whose average lanthanide distribution must complement that of the continental crust, assuming that the overall relative lanthanide abundances for the Earth are the same as those in the chondrites. The ocean floor igneous suite appears to be derived from that residue. Are there rocks that can plausibly be considered samples of that residue, and which have distributions deficient in light lanthanides relative to the chondrites Are there rocks that represent primitive terrestrial mantle from which the lanthanides and other incompatible elements have not yet been extracted ... 

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