Bishop Tuff Revisited: New Rare Earth Element Data Consistent with Crystal Fractionation

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Science  22 Jun 1984:
Vol. 224, Issue 4655, pp. 1338-1340
DOI: 10.1126/science.224.4655.1338


The Bishop Tuff of eastern California is the type example of a high-silica rhyolite that, according to Hildreth, supposedly evolved by liquid-state differentiation. New analyses establish that the Bishop Tuff "earlyllate" rare earth element trend reported by Hildreth mimics the relations between groundmass glasses and whole rocks for allanite-bearing pumice. Differences in elemental concentrations between whole rock and groundmass are the result of phenocryst precipitation; thus the data of Hildreth are precisely those expected to result from crystal fractionation.