Abstract Many of the world's largest fluorite deposits occur in the footwalls of major normal faults. The absence of associated igneous rocks and the high salinity of the fluid inclusions suggests that the mineralizing fluids originated in a sedimentary basin. The Albigeois fluorite vein deposits occur in the Hercynian schists of the southwestern Massif Central, France, and are thought to have formed during Early Permian (Autunian) extension. The Permian St. Affrique basin adjacent to the deposits is proposed as a fluid source. Reconstruction of the chemistry of the ore-forming process suggests that aluminum-fluoride complexes were predominantly responsible for fluorine transport in Albigeois, and that fluorite precipitated as a result of cooling. We identify A1F 3 0 as the principal species responsible for fluorine transport in solution. Cooling destabilizes this complex causing fluorite precipitation. The chemical constraints we discuss are specific to the Albigeois district; however, they may be applicable to other fluorite vein deposits of this type. Fluid inclusion temperatures place constraints on the thermal and fluid flow regimes during mineralization. Using simple thermal/hydrologic modeling we examined the processes of advective heat transport by fluid ascending in a vertical fracture system, and conductive cooling of the fluid to the surrounding rocks. The results suggest that high initial temperatures in the vicinity of 300°C are required in order to account for measured fluid inclusion temperatures as high as 200°C. In addition, fluid fluxes of at least 1.0×10 -6 m/s (≫30 m/yr) are required to bring isotherms between 100° and 200°C sufficiently close to the surface and close together: 1) to account for the fluid inclusion homogenization temperatures, and 2) to create the thermal gradient necessary to precipitate significant quantities of fluorite within a relatively small vertical interval. In active extensional environments normal faulting accompanied by rapid footwall uplift can bring mid-crustal rocks to shallower crustal levels temporarily increasing the geothermal gradient and favoring emplacement of magmatic intrusions in the footwall. Volatile-rich fluids escaping from cooling magma may enrich the groundwater in species such as HF and HC1, contributing to the formation of fluorite deposits at higher structural levels. Flow paths that satisfy both thermal and chemical constraints are likely to have existed wherever major extension of continental crust has occurred.