Relatively strongly magnetic fine components (<30μm, XS-4J and DS-4J) which are most environmentally sensitive were separated from layer S-{5-1} in the Xifeng and Duanjiapo loess sections and analyzed by MPV-3 for...Relatively strongly magnetic fine components (<30μm, XS-4J and DS-4J) which are most environmentally sensitive were separated from layer S-{5-1} in the Xifeng and Duanjiapo loess sections and analyzed by MPV-3 for their morphometric characteristics and reflectance, SEM-ESD for their element contents and XRD for their mineral phases, respectively. The results showed that minerals in both samples are dominated by detrial Fe-Ti oxides of aeolian origin. In sample XS-4J the reflectance and iron contents of magnetic minerals are usually high. In addition to magnetite (Fe-3O-4), maghemite (γFe-2O-3) and hematite (Fe-2O-3), some Fe-high oxide ({72.25 wt%}-{86.67 wt%}), ilmenite (FeTiO-3), and magnetite-ulvspinel were also detected. In sample DS-4J obvious negative linear correlations were found between Ti and Fe, and the contents of Mn, Si, Al and Ca are usually high and the minerals are dominated by magnetite (maghemite), goethite (FeOOH) and limonite (containing Si and OH). In addition, the signs of corrosion of magnetic minerals and newly crystallized magnetite (maghemite) were recognized. Differences in the composition and assemblage characteristics of magnetite minerals between XS and DS reflect significant differences in source rocks and preserving conditions.展开更多
文摘Relatively strongly magnetic fine components (<30μm, XS-4J and DS-4J) which are most environmentally sensitive were separated from layer S-{5-1} in the Xifeng and Duanjiapo loess sections and analyzed by MPV-3 for their morphometric characteristics and reflectance, SEM-ESD for their element contents and XRD for their mineral phases, respectively. The results showed that minerals in both samples are dominated by detrial Fe-Ti oxides of aeolian origin. In sample XS-4J the reflectance and iron contents of magnetic minerals are usually high. In addition to magnetite (Fe-3O-4), maghemite (γFe-2O-3) and hematite (Fe-2O-3), some Fe-high oxide ({72.25 wt%}-{86.67 wt%}), ilmenite (FeTiO-3), and magnetite-ulvspinel were also detected. In sample DS-4J obvious negative linear correlations were found between Ti and Fe, and the contents of Mn, Si, Al and Ca are usually high and the minerals are dominated by magnetite (maghemite), goethite (FeOOH) and limonite (containing Si and OH). In addition, the signs of corrosion of magnetic minerals and newly crystallized magnetite (maghemite) were recognized. Differences in the composition and assemblage characteristics of magnetite minerals between XS and DS reflect significant differences in source rocks and preserving conditions.
