Lanthanide abundances granite

Fig. 28. Typical lanthanide abundance patterns for K-rich granites and rhyolites (data are from table 18). Note the development of extreme depletion in Eu in the more highly fractionated granites.

Fig. 53. Lanthanide abundance patterns for the Archean upper and bulk crusts. In contrast to the post-Archean upper crust, there is no depletion in Eu, suggesting that K-rich granites were only a minor component in the Archean upper crust, compared with their later dominance. (Data are from table 3Z)...

Granite magmas are often rich in volatile compounds (e.g., water, halides, carbonates, alkalis) that tend to accumulate as residual fluids as these magmas solidify. Some granites show steep increases in heaviest lanthanide abundances as a result of interactions with hydrothermal fluids, either associated with their formation or as a result of later interactions (e.g., Kazakhstan massif, Mineyev, 1963 Nigeria, Aleksiyev, 1970 and Bowden and Whitley, 1974). 

Quantitative modelling has been less successfully applied to rocks cff more felsic composition, such as granodiorites, dacites, granites and rhyolites. This is principally due to the ubiquitous presence in these evolved rocks of minor mineral phases, such as sphene, allanite, apatite and zircon, whose lanthanide contents may account for a substantial fraction of the total rock budget. Thus Gromet and Silver (1983) found that sphene and allanite, in a granodiorite from the Peninsular Ranges, California, contained 80-95% of the lanthanide content of the total rock. Distribution coefficients are not well known for these phases and the abundances of these trace minerals are difficult to determine accurately. 

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