Albitized microcline grains of post-depositional and probable detrital origins in Brøttum Formation sandstones (Upper Proterozoic), Sparagmite Region of southern Norway

Untwinned albite (Ab_99.4An_0.4Or_0.2) grains, forming during diagenesis and very low-grade metamorphism, are common in sandstones of the Brøttum Formation (Upper Proterozoic) in the Sparagmite Region of southern Norway. These untwinned albite grains are usually clouded by vacuoles and tiny inclusions which are mostly made of carbonaceous material (although some albite grains also contain some combination of carbonates, quartz, phengite, chlorite, pyrite, halite and anatase). The presence of microcline grains replaced partly by albite indicates that the albite grains are pseudomorphs after microcline. Chessboard albite which occurs in the Brøttum Formation is suggested to be detrital in origin.