Tourmaline in the Martinamor antiform occurs in tourmalinites (rocks with >15–20% tourmaline by volume), clastic metasedimentary rocks of the Upper Proterozoic Monterrubio formation, quartz veins, pre-Variscan orthogneisses and Variscan granitic rocks. Petrographic observations, back-scattered electron (BSE) images, and microprobe data document a multistaged development of tourmaline. Overall, variations in the Mg/(Mg + Fe) ratios decrease from tourmalinites (0·36–0·75), through veins (0·38–0·66) to granitic rocks (0·23–0·46), whereas Al increases in the same order from 5·84–6·65 to 6·22–6·88 apfu. The incorporation of Al into tourmaline is consistent with combinations of xχAl(NaR)−1 and AlO(R(OH))−1 exchange vectors, where xχ represents X-site vacancy and R is (Mg + Fe2+ + Mn). Variations in xχ/(xχ + Na) ratios are similar in all the types of tourmaline occurrences, from 0·10 to 0·53, with low Ca-contents (mostly <0·10 apfu). Based on field and textural criteria, two groups of tourmaline-rich rocks are distinguished: (1) pre-Variscan tourmalinites (probably Cadomian), affected by both deformation and regional metamorphism during the Variscan orogeny; (2) tourmalinites related to the synkinematic granitic complex of Martinamor. Textural and geochemical data are consistent with a psammopelitic parentage for the protolith of the tourmalinites. Boron isotope analyses of tourmaline have a total range of δ11B values from −15·6 to 6·8‰; the lowest corresponding to granitic tourmalines (−15·6 to −11·7‰) and the highest to veins (1·9 to 6·8‰). Tourmalines from tourmalinites have intermediate δ11B values of −8·0 to +2·0‰. The observed variations in δ11B support an important crustal recycling of boron in the Martinamor area, in which pre-Variscan tourmalinites were remobilized by a combination of mechanical and chemical processes during Variscan deformation, metamorphism and anatexis, leading to the formation of multiple tourmaline-bearing veins and a new stage of boron metasomatism.