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Fluid-Gesteinswechselwirkung an alpinotypen ultramafischen Gesteinen der norwegischen Kaledoniden
Alpine-type ultramafic rocks are tectonically emplaced from mantle into the crust. Their petrological and structural alterations occur during their path from deep-seated sources to their crustal emplacement. Therefore, these rocks are suitable for the study of fluid-rock interaction during the syn- and postorogenic processes. Reactions between rock and water-dominated fluid result in matrix alterations, the formation of veins, shear zones and mineral zonations.
Eight localities from the Upper- and Uppermost Allochthonous units of the Norwegian Caledonides were chosen to investigate relative time and place of fluid input, composition and amount of fluid, reacting with ultramafic rocks in different geological settings. Precursor rock, country rock and metamorphic evolution influenced fluid composition and reactions with the ultramafics. All rocks are isofacial with their country rock.
Under greenschist facies conditions the formation of serpentinites is typical, and the formation of ophicarbonates only requires small amounts of CO2. With increasing temperature, the formation of talc-marbles requires higher CO2 amounts. In the brittle to ductile regime, fluid flow is mainly channelled and deformation enforces fluid-rock interaction. Under amphibolite facies conditions, pervasive and channelled fluid flow is about equal. With increasing temperature first CO2 is controlling the reactions. From amphibolite facies on, SiO2 becomes more abundant in the fluid and controls mineral reactions. Once SiO2 is released, it remains efficient during retrograde evolution. With increasing temperature, diffusion becomes more important. Under granulite facies conditions, CO2-metasomatism causes the formation of sagvandites, and SiO2 is inferred to be added from the country rock. Diffusion becomes
more dominant resulting in the formation of reaction veins.
|SWD-Schlagwörter:||Fluide , stabile Isotope , Phasenstabilitäten , Ophiolith,|
|Freie Schlagwörter (deutsch):||Kaledoniden , Serpentinite , reaction progress , Adern|
|Freie Schlagwörter (englisch):||ultramafic rocks , fluid-flow , phase stabilities , reaction progress , stable isotopes|
|Institut:||Institut für Mineralogie, Petrologie und Geochemie|
|Fakultät:||Geowissenschaftliche Fakultät (bis Sept. 2002)|
|Erstgutachter:||Bucher, Kurt (Prof. Dr.)|
|Tag der mündlichen Prüfung:||24.09.2002|