Comparison of the Beauvoir and Cínovec rare metal granite/greisen systems: Role of muscovitization on Li-Sn-W-Ta hydrothermal remobilization
Résumé
We provide a comparative review of greisenization in the Beauvoir (France) and Cínovec (Czech Republic/Germany) deposits, which are two of the world's best studied examples of peraluminous Li-Sn-Ta-W-mineralized granitic systems. While the Cínovec granite cupola is two-to-eight times less enriched in rare metals than Beauvoir, a Li-Sn-W greisen deposit was formed in the former but not in the latter. At Beauvoir, alteration of igneous lepidolite produced Sn-rich and Li-W-Ta-depleted greisen muscovite. In contrast, igneous and greisen zinnwaldite at Cínovec have similar contents of Li, Sn, W and Ta. Late replacement of zinnwaldite by muscovite in the Cínovec greisen is marked by enrichment in Sn and depletion in Li, W and Ta, similar to greisen muscovite from Beauvoir. We conclude that muscovitization, although associated with secondary Sn enrichment, is not essential for the formation of mineralized greisens, which are primarily controlled by the emplacement depth of magmas and the intensity of pervasive alteration.
Domaines
Sciences de la Terre
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