Lithium pegmatite of anatectic origin – A case study from the Austroalpine Unit Pegmatite Province (Eastern European Alps): Geological data and geochemical modeling

Tanja Knoll, Benjamin Huet, Ralf Schuster, Heinrich Mali, Theodoros Ntaflos, Christoph Hauzenberger

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung


There is an ongoing debate as to whether rare element pegmatite is always related to fractional crystallization of huge fertile granite bodies or whether it can also form directly from limited portions of enriched anatectic melt. In this contribution, we present a case study from the Eastern European Alps, showing the continuous evolution from melt generation in staurolite bearing micaschist to spodumene (LiAlSi2O6) bearing pegmatite. The investigated Austroalpine Unit Pegmatite Province formed during Permian lithospheric extension and all levels of the Permian crust are now accessible in a Cretaceous nappe stack. This nappe stack is mapped in detail, subdivided lithostratigraphically and the internal tectonic structure is well understood. It is clear that the described pegmatites are neither spatially nor genetically related to large fertile granite bodies. A review of geochronological data proofs that emplacement of pegmatite and leucogranite is broadly contemporaneous with high temperature-low pressure metamorphism of the country rocks. Field observations give clear evidence of a genetic link between simple pegmatite, leucogranite, evolved pegmatite and albite-spodumene pegmatite, on the one hand, and the subsolidus or suprasolidus metasediment hosting them on the other hand. These relations are underpinned by geochemical major and trace element investigations on all types of rock and the minerals therein. As source rock an Al-rich metapelite enriched in Li (70–270 ppm) with respect to the average upper continental crust is identified. The main Li-carrier is staurolite with up to 3000 ppm Li. The pegmatite and leucogranite originate in anatectic melts that formed between 0.6 and 0.8 GPa and 650–750 °C, corresponding 18–26 km depth. During melt formation staurolite was consumed by sillimanite forming reactions. Subsequently, the melts were enriched in Li by fractional crystallization of quartz and feldspar during their ascent to higher crustal levels. While simple pegmatite and inhomogeneous leucogranite formed in lower and intermediate levels, evolved and albite-spodumene pegmatite crystallised at high levels at conditions between 0.3 and 0.4 GPa and 500–570 °C, corresponding to about 12 km depth. Based on these data we develop a geochemical model for showing that Li can be transferred from a metasediment into an anatectic melt if staurolite is stable or metastable at the onset of melting. Such a melt can contain between 200 and 1000 ppm Li and the melt can be further enriched with up to 5000 to 10000 ppm Li through fractional crystallization of quartz and feldspar, allowing crystallization of spodumene. Estimated fractionation degrees vary between 81 and 99 %, depending on the protolith composition, the melting scenario and the partitioning coefficients. Li-Al-rich metasediments are therefore a rich source of certain rare elements when they first melt. However, the spectrum of elements contained in the melt depends on a wide variety of conditions. This anatectic model provides an alternative explanation for the formation of Li-rich pegmatite if no fertile parent granite can be identified.
FachzeitschriftOre geology reviews
PublikationsstatusElektronische Veröffentlichung vor Drucklegung. - 12 Jan. 2023

Bibliographische Notiz

Funding Information:
This research was supported financially by the ‘‘Mineral und Rohstoffinitiative’’ of the Bundesministerium für Wissenschaft, Forschung und Wirtschaft (BMWFW). The authors would like to thank Hugh Rice, Jürgen Konzett and Holger Paulick for discussions and review of the manuscript, Peter Onuk for measuring the muscovite samples at the LA ICP-MS, Christian Auer for his support with the SEM, Gerald Schuberth-Hlavec for building the pegmatite database and Richard Göd for his critical and constructive input. The authors also thank Ibrahim Özcan for processing the samples and Ilka Wünsche and Andreas Wunderlich for preparing the thin sections. The authors are grateful for reviews of associate editor Harald Dill and two anonymous reviewers, which improved the quality of the manuscript. Last but not least, a big heartfelt thanks to Caro, Little L and Johann, for their continued support and acceptance, and to Sloba for her motivation and support in all situations, as well as her role as the greatest possible role model.

Publisher Copyright:
© 2023 The Authors


  • Lithium
  • pegmatite
  • anatectic
  • Austroalpine

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