Fluid inclusions, isotopic fluid composition and new age datings of rare-metal pegmatites, Sierra de San Luis, Argentina

SOSA, G.; VAN DEN KERKHOF, A.; WEMMER K.; LÜDERS, V.; PLESSEN, B.; MONTENEGRO T.

Heildenberg

Otro; 23rd Latin American Colloquium LAK 2014; 2014

Universität Heildenberg

Rare-metal (Be, Li, Nb, Ta, Sn) granitic pegmatites from the Sierra de San Luis (Argentina) are related to syn-Famatinian, meta- to peraluminous S-type granites (Sosa et al. 2007). Nb-Ta-pegmatites are concordantly emplaced in fine-grained quartz-mica schist of the Conlara Meta-morphic Complex in the east, while Sn-bearing pegmatites are emplaced in the westerly schist of the Pringles Metamorphic Complex (Sosa, 2002; Sims et al, 1998). The pegmatite minerals must have crystallized at 400-500°C /2-3 kbar from a H2O-NaCl-CO2-CH4-N2 dominated fluid, preserved as primary inclusions in beryl and plagioclase. Columbite-tantalite preserves only aqueous inclusions and crystallized at 300-400°C, the same crystallization temperature of cassi-terite; apatite crystallized at 200-300°C. Carbonic fluid inclusions show always higher CH4-concentrations in the Sn-pegmatites compared to the Nb-Ta-pegmatites (Van den Kerkhof et al., 2005).