GLAUCONITE WEATHERING IN AN ARCTIC ENVIRONMENT

Changes in clay mineralogy across an inactive outwash fan in Kongressdalen, Svalbard, show measurable weathering of glauconite since the fan's formation during the Little Ice Age (1550-1920). Kongressdalen is located in Western Spitsbergen, Svalbard, an archipelago located above the Arctic Circle between 78˚ to 81˚N and 10˚ to 35˚E. This region has an arctic-oceanic climate, with a mean annual air temperature of -6.3˚C and a mean annual precipitation of 445mm. The outwash fan is composed of moderately sorted sediments ranging in size from sand to coarse gravel. On average, the mud fraction composes 2-3% of the sediment, but may be as high as 7%. Most of the fan sediment is derived from the glauconite bearing Kapp Starosin formation of Permian age. X-ray diffraction of oriented, <1µm, unaltered sediment samples collected from freshly exposed channels reveal 10.0Å (001), 5.0Å (002), and 3.3Å (003) peaks that are unaffected by ethylene glycol saturation or heating to 550˚C for 1 hour. X-ray diffraction of weathered material collected from surfaces vegetated with moss and lichen display an additional peak at approximately 14.3Å, which shifts to 16.0Å upon ethylene glycol saturation, indicating the presence of an expandable smectite-like mineral. Incomplete expansion may be due to either mixed layering or incomplete formation of expandable layers. Both fresh and weathered samples contain kaolinite as indicated by peaks at 7Å and 3.5Å that are non-expandable and are destroyed with 1 hour of heating at 550˚C. X-ray fluorescence analysis of the mud fraction (<63µm) shows that the fan material is silica rich (approximately 80% SiO₂) with the weathered material depleted in potassium (1.60% K₂O) relative to the fresh sediment (2.43% K₂O)

These results show significant weathering of glauconite minerals can occur in arctic environments. Ratios of half peak height at half peak width for 10Å and 14Å peaks of the air dried samples reflect an increase in smectite relative to glauconite toward the northeast side of the fan, indicating a greater level of weathering and possibly older depositional surfaces towards the northeast.