RT Journal Article
T1 The Peña do Seo W-Sn deposit, NW Iberia: Petrology, fluid inclusions and O-H-S isotopes
A1 Caldevilla, P.
A1 González Menéndez, L.
A1 Martín Crespo, Tomás
A1 Vindel Catena, Elena
A1 Guedes, A.
A1 Berrezueta, Edgar
A1 Castañón, A.M.
A1 Gómez Fernández, Fernando
AB The Peña do Seo W-Sn ore deposit in NW Iberia consists mainly of quartz veins hosted in schists. Vein mineralogy comprises wolframite, cassiterite and minor molybdenite. Peraluminous S-type granites and minor metaluminous granitoid breccias crop out in the same location. Whole rock geochemistry, mineral characterization, fluid inclusions and stable isotope geochemistry have been combined to infer hydrothermal mineralization conditions.A pre-ore stage (0) involving the alteration of host rocks, three stages of mineralization (I, II and III), and a supergene stage (IV) have been identified. Stage I (oxide-halide-sulfide stage) consisted of a cassiterite-pyrite-fluorite mineralization in granitoid breccias. Stage II (main oxide stage) involved wolframite-rich selvages and wolframite-cassiterite-(molybdenite) quartz veins. Stage III (main sulfide stage) consisted of a sulfide mineralization in quartz veins comprising pyrite and minor arsenopyrite and chalcopyrite.Three types of fluid inclusions were found in vein quartz: (1) aqueous two-phase inclusions, with homogenization temperatures (Th) between 445 °C and 280 °C and moderate salinities (9–14 wt% NaCl eq.), (2) aqueous-carbonic three-phase fluid inclusions, with Th from 340 °C to 260 °C and low salinities (2–7 wt% NaCl eq.), and (3) aqueous two-phase fluid inclusions, with Th from 270 °C to 155 °C and low salinities (0–6 wt% NaCl eq.). δ18O values in quartz from mineralized veins range from +11.2‰ to +13.4‰, and between +15.0‰ and +15.4% in quartz from mineralized granitoid breccias. δ34S values in sulfides (pyrite, arsenopyrite and chalcopyrite) range between +13.0 ‰ and +37.1 ‰, thus suggesting a marine source of sulfate and possible equilibration with host-rock sulfides. δD values in muscovite and chlorite from quartz veins range between −105.7 ‰ and −71.5 ‰ and between −69.4 ‰ and −67.1 ‰, respectively, indicating a transition from magmatic to magmatic-metamorphic conditions.An aqueous (H2O–NaCl) magmatic-hydrothermal fluid led to the W-Sn mineralization, as deduced from the studied fluid inclusions and isotopic signatures. High W and Sn contents in the peraluminous granites indicate that the W-Sn mineralization in Peña do Seo could partially be related to the granites and granitoid breccias. Whereas the Sn (±W) likely derived from hydrothermal fluids exsolving from the crystallizing magmas, host quartz schists would have supplied other elements required for wolframite deposition such as Fe and Mn. Sulfide mineralization in stage III was probably driven by fluid dilution.
PB Elsevier Science B.V., Amsterdam
SN 0169-1368
YR 2023
FD 2023-04
LK https://hdl.handle.net/20.500.14352/73362
UL https://hdl.handle.net/20.500.14352/73362
LA eng
NO INTERREG V-A Spain-Portugal Cooperation Programme, 2014-20
NO Junta de Castilla y León
DS Docta Complutense
RD 6 abr 2025