• Epsilon (ε) Nd values and Sm-Nd model ages (DM, Depleted Mantle model ages) are used to discriminate whole-rock protolith materials which are derived from more juvenile or from long-term LILE depleted vs enriched sources. In addition, and mostly in combination with mineral dating, DM model ages from whole rocks are used to estimate a “mean crustal residence time” for rocks of the continental crust (clastic sediments or their metamorphic derivates: schists, gneisses).
  
  
• Our main interest, however, is focused on mineral dating. The most important prerequisite for successful Sm-Nd mineral dating are ultrapure mineral separates. Depending on Nd concentration, sample sizes of some 10 - 100 mg are generally required (hence time-consuming hand-picking under the binocular microscope is inevitable!). To improve sample purity and to eliminate optically undetected micro-inclusions, acid leaching experiments (mainly for garnet) are also successfully performed.
  
  
• Garnet has variable, but generally high Sm/Nd ratios if compared with other minerals (the highest Sm/Nd ratios measured so far are > 16), and therefore it yields important time information in metamorphic rocks, but also in (meta-)igneous rocks. Because of its prominent importance for P-T-d estimation, Sm-Nd data from this mineral have been frequently determined  in order to link P-T-d and geochronological information directly (i.e., for one and the same material). In addition, garnet often shows conspicuous grain-internal trace element zonation resulting in strong variation of Sm/Nd, thus allowing “internal garnet isochrons” to be calculated. In our laboratory, Sm-Nd garnet analyses have been performed during the past fifteen years for a range of P-T conditions and on various lithologies (metabasites, metapelites, meta-pegmatites, dykes), with emphasis on the Eastern Alps.
  
  
• Despite the well-known low-fractionation behavior of REE, the apparent “spread” in Sm/Nd of the different minerals pertaining to one and the same assemblage - most importantly major and trace mineral phases - is generally sufficient to allow internal time resolution to be made. The following materials have been analyzed:
  
  
• Plagioclase-clinopyroxene (+ wr, ± orthopyroxene) pairs from gabbros (magmatic crystallsation age)
  
  
• Garnet-omphacite (+ zoisite, + amphibole, + phengite) pairs from eclogite (high-P age)

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• Garnet-feldspar (+ wr, + mica, + staurolite) pairs from schists, paragneisses (metamorphic crystallization)