Mineralogy and geochemistry of cryoconite sediments in Eqip Sermia glacier (Central-West Greenland)

The geochemical and mineralogical composition of cryoconite sediments on the Greenland Ice Sheet cap (Central-West Greenland) was investigated with the aim to characterize grain size, mineralogy and geochemistry of dark materials deposited on glacial surface. Cryoconite particles collected on the Eqip Sermia glacier have angular-faceted, sharp-edged shape of the fine grains with mean size of 10-50 mm. The X-ray diffraction analysis of these cryoconite sediments shows that they mainly contain three silicate minerals (quartz, amphibole and plagioclase) and rare oxides, with slight variation in modal composition. Also X-ray fluorescence geochemical exploration reveals a similar pattern among samples. Trace elements content normalized to the averaged upper continental crust indicates values close to 1, except for a depletion in barium and enrichment in chromium. This average composition resembles the mean of weathered rocks in the surrounding area, indicating that dark material deposition was probably dominated by input of local geological outcrops around the glacier.