The fluorite deposits of Asturias (northern Iberian Peninsula) are hosted by rocks of Permo-Triassic and Palaeozoic age. Fluid inclusions in ore and gangue minerals show homogenization temperatures from 80 to 170°C and the presence of two types of fluids: an H20-NaCI low-salinity fluid «8 eq. wt% NaCI) and an H20-NaCI-CaCI2 fluid (7-13 wt% NaCI and 11-14 wt% CaCI2). The low salinity and the Cl/Br and NalBr ratios (CI/Brmolar 100-700and NalBr molar 20-700) are consistent with an evaporated sea water origin of this fluid. The other end-member of the mixture was highly saline brine with high Cl/Br and NalBr ratios (CI/Brmolar 700-13 000 and NalBrmolar 700-11 000) generated after dissolution of Triassic age evaporites.

Calculated 6180 of fluids ranges from 03 to + 7.4%0 during barite precipitation, from +0.8 to +4%0 during quartz formation and around + 3%0 during carbonate deposition. The 634S of barite (+ 17 to + 56%0), is explained by sulphate reduction processes (either thermochemically or bacterially mediated) in a system closed with respect to sulphate. The 634S of sulphide (+ 0.6 to -32%0) is compatible with these processes although bacterial processes must have dominated at Villabona. Organic matter was an important source ofC in the fluids especially in Villabona (613C=-14.8 to -2.5%0 in calcites and from -7.9 to -2.2%0 in dolomites). Differences in host rock and position within the basin, and the lithology of the basement, seem to have exerted a strong control on the chemistry of mineralizing fluids providing each district with distinctive characteristics.

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The origin and age of the hydrothennal fluids related to the precipitation of fluorite, barite and calcite in the Villabona, La

Hydrothermal quartz-apatite veins, called "Iberian-type", occur exclusively in the southern Central Iberian Zone. This study presents a multidisciplinary approach leading to the mineralogical, fluid inclusions, and geochemical characterization of these veins from two representative areas, Logrosán and Belvís-Navalmoral, in order to establish their relationship with nearby phosphorous-rich granites and apatite in Neoproterozoic metasediments. The mineral assemblage of these veins comprises quartz, apatite, minor sulfides, dolomite, Fe-Mg-carbonates and Fe-Mn-oxides. Three texturally different types of apatite have been recognized in the veins: apatite I showing prismatic habit associated with minor sulfides, apatite II occurring as white fibrous radial crystal aggregates called "dahllite", and apatite III as grayish to greenish hexagonal crystals. Hydrothermal apatite from veins (H-apatite) is enriched in Sr and depleted in Mn-Y-REE-Th-U-Pb compared to magmatic apatite (M-apatite) from the granitic plutons. However, trace element compositions of apatite from metasedimentary phosphorous-rich levels or nodules (Sapatite) of the Schist-Greywacke Complex show similar characteristics to the H-apatite, although the H-apatite stands out for its relatively high Sr-contents. This relative Sr enrichment in H-apatite is interpreted as inherited from both phosphate in Neoproterozoic metasediments (S-apatite) and carbonate levels. REE, fluid inclusion and stable isotope data are consistent with a long episode of hydrothermal activity implying cooling and dilution processes while interacting with phosphate-rich shale and carbonate beds in the SGC. Fluid inclusion study undertaken on hydrothermal apatite and quartz reveals the presence of aqueous low salinity fluids (0.2-6.7 wt.% NaCl equiv.) at moderate to low Th (125-350 °C). All available data point at a recycling event of the southern CIZ metasediments (the SGC) during post-Variscan hydrothermal fluid circulation as the more plausible origin of the phosphate vein-type mineralizations.