A New Alpine Metallogenic Model for the Pb-Ag Orogenic Deposits of Macôt-la Plagne and Peisey-Nancroix (Western Alps, France)

Understanding mass transfer associated with fluids circulation and deformation in the Alpine orogeny is often complex due to common multistage crystallization. For example, two emblematic historic Pb-Ag deposits of French Alps, Macôt-la Plagne (MP) Peisey-Nancroix (PN), a sedimentary or orogenic origin still debated. To discriminate between metallogenic models deposits, an integrative methodology combining field, microstructural, mineralogical, thermobarometrical, geochronological data was here applied for establishing detailed Pressure–Temperature–Time–Deformation (P-T-t-d) mineralization conditions. Both are located Permo-Triassic quartzite External Briançonnais domain along Internal Front (Internal Western Alps). The ore mainly occurs as veins disseminated textures containing galena, pyrite, variable content tetrahedrite–tennantite chalcopyrite. Quartz porphyroclasts sulfide microstructures indicate dynamic recrystallization during main fluid episode. Chlorites K-white micas (phengite) chemical analysis thermodynamic modeling from compositional maps onset at 280 °C, precipitation stage 315 ± 35 °C 6.25 0.75 kbar. In situ U-Pb dating on monazite, cogenetic sulfides, gives ages around Ma both deposits. dataset converges MP-PN relation thrusting “Nappe des Gypses” metamorphic peak.