UNIQUE MINERALOGICAL PROPERTIES OF CIRCUM-ARCTIC SOURCE REGIONS

The use of mineralogy in interpreting sediment provenance, transport pathways, and paleoclimatic records is well established. In order to use mineralogy for these purposes in the Arctic Ocean, unique circum-Arctic mineralogy must exist. Preliminary results show that there are a number of minerals that can potentially be used to explore changes in provenance and variations in transport processes. Due to the likely contrast in the transport of coarse-grained (ice-rafted) and fine-grained (current and ice-rafted) material, each fraction is examined separately. Representative source samples were selected and separated into <45 μm fractions for X-Ray diffraction analysis of mineralogy. This size fraction was chosen to avoid the overwhelming quartz signal from the coarsest material while still retaining the signal of ice-rafted detritus as well as fine-grained material transported via currents. In general, the results show that the North American sources have much greater amounts of dolomite and less feldspar compared to Eurasian sources. The Eurasian sources clearly show a preponderance of feldspar as well as mafic minerals, probably due largely to the Putorana Trap Basalts along the Siberian coast (Taymyr Peninsula). For example, the plagioclase feldspars offer the opportunity to highlight differences between these regions. The samples were analyzed for six plagioclase feldspar phases. The North American sources contain primarily albite while nearly devoid of other plagioclase phases. Conversely, the Eurasian sources have a much broader plagioclase composition. In addition to a concentrated albite signal, these Siberian regions contain appreciable concentrations of other phases, specifically, oligoclase, bytownite, and labradorite. The clay fraction also shows differences between North American and Eurasian sources. For instance, sources show that expandable clay minerals are ubiquitous, but individual mineral species differ in the two Arctic regions. The Eurasian region is associated with higher ferruginous smectite and hectorite, while the North American sources are restricted to primarily saponite and are the only regions where calcic smectite is found in any significant concentration.