Mineralogical composition of cryoconite on glaciers in northwest Greenland（グリーンランド北西部の氷河上クリオコナイトの鉱物組成）

Abstract

The mineralogical composition of cryoconite on a glacial surface was investigated on six glaciers in northwest Greenland (Qaanaaq Qaqortaq Tugto Bowdoin Sun and Scarlet Heart. The X‑ray diffraction analysis showed that the cryoconites mainly contained seven silicate minerals: hornblende quartz potassium feldspar plagioclase illite kaolinite and chlorite. Semi‑quantitative mineralogical analysis of the silicate mineral composition on the Qaanaaq Glacier showed little variation among the samples collected from five different elevations. This indicates that the minerals on the glacier were probably dominated by dust from a unique source which is recently transported from local sediments including soil and moraine. On the other hand the mineral composition varied significantly among the glaciers. Based on the clay mineral content the glaciers could be classified into three groups. Type A: high clay mineral content composed of illite and kaolinite found on Qaanaaq Qaqortaq and Tugto; Type B: high clay mineral content composed of only kaolinite found on Sun; and Type C: lower clay mineral content composed of only kaolinite found on Bowdoin and Scarlet Heart. The geographical distribution of the types of glaciers did not correspond with the geology in this area indicating that the mineralogical composition is not determined just by the geologi‑ cal conditions around glaciers but also by other factors such as the redistribution of sediments by glacial fluvial or coastal processes.