Petrographic features of dated wolframite, cassiterite and apatite in the Echassières complex. (a) Quartz vein from the La Bosse stockwork (plane-polarized and cross-polarized light), showing wolframite corroded by an assemblage of cassiterite, topaz and muscovite (1-2). Fine-grained topaz, muscovite, cassiterite and quartz occur either as discrete crack-fillings (3) or as larger zones (4) crosscutting or infilling the boundaries of coarser quartz grains showing evidence of dynamic recrystallization (undulose extinction and subgrains). In (1) cassiterite form vein-like infill crosscutting wolframite, and in (3) topaz replaces wolframite along an irregular, embayed contact. In (4), the darker zones correspond to cavities. (b) Micro-XRF chemical map of a quartz-muscovite-apatite-wolframite vein from the La Bosse stockwork crosscutting mica schist and early quartz lens (see Fig. 3d for location of the thin section). Note the spatial relationship between wolframite and apatite. (c) Example of cathodoluminescence (CL) images of cassiterite grains from the B1 unit of the Beauvoir granite showing oscillatory zonation locally truncated by high-CL signal zones.