Mineralogical–Geochemical Features of Ice-Rafted Sediments in Some Arctic Regions

Resumo

The quantitative mineral composition estimated using the Rietveld method and some geochemical features are considered for bulk samples of the ice-rafted sediments (IRS) from some Arctic regions. Layer silicates in the studied samples vary from ~20 to ~50%. They are dominated by micas and their decomposition products (illite and likely some part of smectites) at significant contents of kaolinite, chlorite, and transformation/decomposition products of the latter. A significant content of illite and muscovite among layer silicates in most IRS samples suggests that sources of the sedimentary material were mainly mineralogically similar to modern bottom sediments of the East Siberian and Chukchi seas, as well as presumably sediments of the eastern Laptev Sea. It is suggested that a significant kaolinite fraction in IRS samples from the North Pole area can be caused by the influx of ice-rafted fine-grained sedimentary material from the Beaufort or Chukchi seas, where kaolinite is supplied from the Bering Sea. Positions of IRS data points in the (La/Yb)_N–Eu/Eu*, (La/Yb)_N–(Eu/Sm)_N, and (La/Yb)_N–Th diagrams show that the studied samples contain variable proportions of erosion products of both mafic and felsic magmatic rocks and/or sufficiently mature sedimentary rocks. This conclusion is confirmed by localization of IRS data points in the Th/Co–La, Si/Al–Ce, and Si/Al–Sr diagrams.