1. Reinterpretation of a major terrane boundary in the northern Svalbard Caledonides based on metamorphic fingerprinting of rocks in northern Spitsbergen
- Author
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Bazarnik, Jakub, Kosminska, Karolina, McClelland, William C., Strauss, Justin V., Piepjohn, Karsten, Elvevold, Synnove, Zieliuski, Grzegorz, and Majka, Jaroslaw
- Subjects
Metamorphism (Geology) -- Analysis ,Tectonics (Geology) -- Analysis ,Rocks, Metamorphic -- Composition -- Testing ,Earth sciences - Abstract
Tectonic models for development of the Svalbard Caledonides depend on reliable assessment of the metamorphic evolution of the various basement provinces involved. The Mosselhalvoya Group (MG) and the Atomfjella Complex (AC) have previously been assigned to the Nordaustlandet and West Ny-Friesland terranes, respectively. New analytical data and petrographic observations indicate that both units experienced two-stage metamorphism under similar pressure-temperature (P-T) conditions. Two stages of amphibolite facies metamorphism (Ml and M2) are clearly recorded by garnet and staurolite porphyroblast textures. The results of thermodynamic phase equilibrium modeling indicate that peak M2 metamorphism occurred at ~ 7-7.5 kbar and 590-600 [degrees]C in both units. Zirconium-in-rutile trace element thermometry confirms the temperature estimates for Ml and M2 stages of metamorphism. Monazite chemical Th-U-Pb dates from the MG resolve a two-stage garnet growth at 444 [+ or -] 7 Ma (Ml) and 423 [+ or -] 6 Ma (M2). In contrast, monazite dated in the AC defines a single age of 420 [+ or -] 4 Ma interpreted as M2 growth. We suggest M2 was coeval with early strike-slip motion along the Billefjorden Fault Zone, whereas Ml reflects initial tectonic burial of the studied units. The similarity in metamorphic history between the both units suggests that the boundary between them is a subordinate thrust fault within the Atomfjella thrust stack rather than a major boundary separating the Nordaustlandet and West Ny-Friesland terranes. The MG should be included within the West Ny-Friesland terrane and the tectonic boundary with the Nordaustlandet terrane is likely the Eolussletta Shear Zone. Key words: Mosselhalvoya Group, Atomfjella Complex, West Ny-Friesland terrane, Nordaustlandet terrane, thermodynamic phase equilibrium modelling, monazite, 1. Introduction The Svalbard Caledonides are traditionally divided into three main basement blocks, terranes, or provinces with differing structural history, sedimentary record, and tectono-thermal evolution (Harland 1997). The Northeastern, Northwestern, [...]
- Published
- 2023
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