Abstract
During regional metamorphism of the Malenco serpentinized peridotite (Sondrio, northern Italy), the mineral assemblage pentlandite-awaruite-magnetite-native copper-antigorite-brucite-olivine-diopside is formed. The opaque assemblage indicates very reduced fluids with fO2 values 4 log units below QFM. Primary fluid inclusions were trapped in diopside overgrowth, contemporaneous with the opaque assemblage. These metamorphic fluids are saline aqueous solutions (about 10.4 mol% NaCl equivalent) and contain molecular H2 of approximately 1 mol%, as shown by micro-Raman analysis and microthermometry. The fluids are interpreted to have been formed during deserpentinization at the olivine-in isograd under strong reducing conditions.
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Peretti, A., Dubessy, J., Mullis, J. et al. Highly reducing conditions during Alpine metamorphism of the Malenco peridotite (Sondrio, northern Italy) indicated by mineral paragenesis and H2 in fluid inclusions. Contr. Mineral. and Petrol. 112, 329–340 (1992). https://doi.org/10.1007/BF00310464
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DOI: https://doi.org/10.1007/BF00310464