Diagenesis of spiculites and carbonates in a Permian temperate ramp succession – Tempelfjorden Group, Spitsbergen, Arctic Norway

• Published in: Sedimentology
• Main Authors: Matysik, Michał, Stemmerik, Lars, Olaussen, Snorre, Brunstad, Harald
• Other Authors: Betzler, Christian, Vetenskapsrådet
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Tempelfjord*; Tempelfjorden; Spitsbergen
• Online Access: http://dx.doi.org/10.1111/sed.12404; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fsed.12404; https://onlinelibrary.wiley.com/doi/pdf/10.1111/sed.12404

Abstract This paper explores little investigated diagenesis of spicule‐dominated sediments, based on Permian spiculites and cool‐water carbonates of the Tempelfjorden Group in central Spitsbergen. Field observations, petrography, stable isotope geochemistry, and mineralogical and chemical analyses reveal that the strata have been subjected to multistage diagenesis as the result of silica phase transitions at medium burial depths and deep‐burial overprinting. The growth of silica concretions occurred during the opal‐A/opal‐ CT conversion and was controlled by the content and distribution of clay and spicules in the sediment, resulting in a variety of megascopic silica fabrics. Opal‐ CT was subsequently dissolved, and all silica is now in a stable quartz stage. Petrographically, the rocks are characterized by a variety of chalcedony and quartz cements which perfectly preserve precursor textures. Most cements precipitated from silica‐oversaturated fluids, and their shapes reflect the silica saturation state and geometry of the pore space. Some microquartz and cryptoquartz also formed by a solid–solid inversion (recrystallization) of chalcedony. The cements have δ 18 O values between +30‰ and +20‰ Standard Mean Ocean Water and display a systematic depletion in 18 O from the first to the last crystallized, interpreted to reflect a gradual increase in temperature during burial. The precipitation of quartz cements started in the Middle Triassic when the strata passed the 19°C isotherm at burial depths of ca 600 m, and was completed in the mid‐Cretaceous, 2·3 km beneath the sea floor at temperatures of 75°C. Late diagenetic overprinting of the chert includes fracturing, brecciation and cementation with carbonate cements having δ 18 O values between +2‰ and −30‰ Pee Dee Belemnite and δ 13 C values between +4‰ and −14‰ Pee Dee Belemnite; they are linked to hot solutions introduced during Cretaceous volcanism or Palaeogene tectonism. This study illustrates the diagenetic pathway during burial of spicule‐rich sediments in a ...