Bolivia, define a layered stratigraphy of basal andalusite-, biotite(‐ muscovite)-bearing rhyolite tuVs (AR), overlain by cordierite-, biotite-bearing rhyolite tuVs (CR), and capped by biotite-bearing quartz latite tuVs, lavas, and late domal flows (QL). Mineral and whole-rock compositions become more evolved from top to bottom, INTRODUCTION with diVerentiation reflected by decreasing Ca, Ba, Mg, Fe, and Peraluminous granitic rocks are important beyond their rare earth elements (REE) versus increasing F, Na/K, and al- relative volumes in the crust because they host many of uminosity from QL to AR. Mineral, whole-rock, and glass inclusion the world’s ore deposits of Li, Be, Sn, W, Nb, and Ta. compositions are consistent with derivation of all three rock types These and other minor- to trace-level elements and from a single stratified magma reservoir, but age and spatial relations fluxing components (e.g. B, Cs, F, Cl, H2O, etc.) behave between the three units make this unlikely. Genesis of the QL incompatibly and are likely to be mobile in plutonic involved biotite-dehydration melting of an aluminous source at T settings. Fresh peraluminous volcanic rocks, and their > 750∞C and P [ 4‐6 kbar. If not co-magmatic with QL, the mineral-hosted melt (glass or devitrified) inclusions, may other units were generated primarily by muscovite-dehydration melting thus provide better estimates of the original magmatic at T = 730‐750∞C and P [ 3·5‐4·5 kbar for CR, and T concentrations of these important components. Although Z 750∞C for AR with pre-eruptive residence at low pressure peraluminous granitoids are common in collisional tec(1·5‐3·0 kbar). Low hematite contents (XHem Z 0·06) of ilmenite tonic settings, few examples of their volcanic equivalents grains in AR, CR, and early grains (as inclusions in plagioclase have been described. and sanidine cores) in QL indicate reduced conditions imposed by a The Bolivian tin belt (Fig. 1, inset) represents one of graphite-bearing source. Compositional variability among texturally the great strongly peraluminous igneous provinces of the later oxides (ilmenite with XHem= 0·06‐0·50, primary magnetite), world, and is one of few such regions bearing voluminous however, apparently records progressive increases in pre-eruptive f(O2) silicic peraluminous volcanic rocks. Most studies of the in QL. Plagioclase‐melt equilibria and electron microprobe analysis Bolivian igneous rocks have addressed their relations to diVerence for quartz-hosted glass inclusions suggest pre-eruptive melt tin mineralization, which typically is associated with H2O contents [5‐7 wt % for the AR, ~4‐6 wt % for the CR, pervasive alteration and/or veining of shallow porphyritic and ~3‐5 wt % for the QL.