Rare-earth element (REE) determinations of pegmatites and adjacent wallrocks of the calcalkaline Bergell intrusion are presented. The pegmatites are derived from a granitic magma produced by AFC contamination of a tonalité with roof pendant material. The geochemical differentiation of the acid dykes is characterized by a depletion of LREE probably caused by fractional crystallization of allanite and minor sphene. According to their REE distribution patterns two different pegmatite groups can be

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... distinguished: The pegmatites intruded m the high metamorphic Gruf unit (group B) reveal contaminated REE distribution patterns, strongly related to their adjacent wallrock, whereas the remaining dykes (group A) have undisturbed patterns. Group A pegmatites can be subdivided into two categories according to their degree of differentiation A lower fractionated biotite type with KzO > Na20 and a less developed negative Eu anomaly can be distinguished from a highly evolved muscovite type with Na20 > KzO and a strongly negative Eu anomaly. Biotite pegmatites show a differentiation trend towards a lower anorthite component m the feldspars leading to an increase of the Eu anomaly. Muscovite pegmatites are strongly depleted in Eu. The remaining low Eu content correlates with the CaO content. Late in situ fractionation and possible multiple injection led to an internal zonation of large pegmatite bodies and lenses. Strong variations of the REE content in this zones can be observed, similar to those observed in large scale lateral differentiation processes.