A1100 Goldschmidt Conference Abstracts 2007 Low-grade zeolite facies Se isotopic variations in black shales metamorphism in gneisses of the of the Yutangba Se deposit, China 1,2 2 Simano nappe (Arvigo, Val Calanca, H.J. WEN AND J. CARIGNAN Grisons, Switzerland) 1SKLODG, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, China T. WEISENBERGER AND K. BUCHER (
[email protected]) University of Freiburg, Germany, 2CRPG-CNRS, 15, Rue Notre-Dame des Pauvres, B.P. 20, (
[email protected]) 54501, Vandoeuvre-lès-Nancy Cedex, France (
[email protected]) Banded biotite gneisses intercalated with coarse light coloured two mica gneisses and less frequently with The Yutangba Se deposit is the only sedimentary-type Se calcsilicate lenses are mined as buidling stones at Arvigo. The deposit known in the world to date. Se is present in relatively rock series belongs to the upper Simano nappe of the high abundance in both host rocks and ores, with crystalline Penninic basement. The Arvigo quarry became concentrations of up to 1.3% on average in the enriched zones. famous for a large number of Alpine fissure minerals, which Our preliminary study showed that about 66% Se occurs as occur in extensional fractures and cavities of the granitic nanograins of elemental Se (Se0) embedded in kerogen. Three gneisses. Fissures and gashes formed by semi-brittle hypotheses are proposed to explain the presence of Se0:1) sea deformation of granitic gneisses, which were generated during water Se was reduced by a high productivity of marine exhumation and uplift of the Alpine orogen.