Spatial trace and rare earth elemental compositions of surficial sediments on the high Mountains, Central Asia, and implications for desert sand and Asian dust

Abstract

As one of the major mountain systems in Central Asia, the Tianshan Mountains provide vast amounts of sediment to adjacent areas. The elemental compositions of surficial sediments on the piedmont of the Tianshan Mountains were investigated to track surface processes. However, spatial comparisons of the elemental compositions of the sediments in the Tianshan Mountains and adjacent areas remain limited. To address this issue, this study investigated the trace element compositions (including rare earth elements (REEs)) of surficial sediments in a vast region ranging from the Pamirs, Tarim Basin, and Tianshan Mountains to the Junggar Basin. According to statistical analyses of the selected source tracers of trace element and REE ratios, this large region can be geochemically divided into two regions. One region comprises the Pamirs, Tarim Basin, and South and Central Tianshan Mountains (PTSC), where the sediments are characterized by contrary source tracer ratios compared with the other region comprising the Yili Basin, North Tianshan, and Junggar Basin (YNTJ). We suggest that the source bedrock is the primary factor controlling the trace element and REE compositions in these two regions. The trace element and REE compositions in the PTSC and YNTJ regions represent signatures of the two endmembers of Asian dust. The trace compositions of loess deposits on the Chinese Loess Plateau (CLP) and Asian dust archived in the North Pacific Ocean (NPO) mostly resemble those of sediments in the PTSC region, suggesting that Asian dust is mainly derived from sediments eroded from the North Tibetan Plateau. Our study enriches our understanding of the source materials of Asian dust archived in the CLP and NPO.