Complex REE zonations in metamorphic garnet reflect accessory mineral reactions

University essay from Göteborgs universitet/Institutionen för geovetenskaper

Abstract: A garnet from the Sesia Zone, NW Italy, was selected for Major and Rare Earth Element(REE) mapping, using LA-ICP-MS – a procedure previously not conducted at the Departmentof Earth Science at University of Gothenburg. The original inclusion assemblage of the garnetis preserved, and the mapping revealed two distinct changes in both garnet chemistry andinclusion assemblage, both which can be linked to the metamorphic development of theregion. The onset and disappearance of REE bearing inclusions is mirrored in the garnet, as itshowed fluctuating concentrations of REEs, while the mineral assemblage changed. TheREEs are in this case the most valuable tool we have in terms of interpreting relict mineralreactions. If researched enough, the REEs on their own might yield enough information tointerpret metamorphic events such as subduction episodes.Key words: RARE EARTH ELEMENTS, REEs, GARNET, METAMORPHISM

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