Main characteristics and genesis of the Vale de Pães skarn (Cuba-Vidigueira, Ossa Morena Zone, Portugal)

摘要: The Vale de Paes (Cuba-Vidigueira) mineralisation is composed of magnetite ± sulphides and hosted in a Pre-Variscan metamorphic sequence intruded by igneous rocks belonging to the Beja Igneous Complex. Its mineral chemical features are compatible with zoned Fe-skarn: Mg-rich (Fo + Di90, oxidised) Ca-rich (Grs Di81-39, oxidised or relatively reduced). In Fe-Mg skarn, deposition occurred along anhydrous assemblage at ≈ 600 °C; precipitated from retrograde stage onset (≤ 550 °C) during hydrated carbonate phases formation period (< 420 °C). Fe-Ca together association, was followed 400°C. mineralising process involved moderate-high salinity fluids controlled variations redox potential pH.