Uranium Isotopic Composition and Constraints on the Provenance of the Qinghai‐Tibet Plateau's Surface Dust
Uranium Isotopic Composition and Constraints on the Provenance of the Qinghai‐Tibet Plateau's Surface Dust
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DOI：
10.1029/2021jf006480
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发表时间：
2022-03
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通讯作者：
Xiaoyu Jiao;Z. Dong;E. Parteli;J. Brahney;Ting Wei;Marcelli Augusto;J. Nie;Jiawen Ren;X. Qin
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作者：
Xiaoyu Jiao;Z. Dong;E. Parteli;J. Brahney;Ting Wei;Marcelli Augusto;J. Nie;Jiawen Ren;X. Qin
风沙的产生和排放可以提供地质演化与气候之间当代和历史联系的关键信息。TP尘同位素比值（234U/238U）的空间变化在松潘—甘孜—科尔溪、喜马拉雅和昆仑—柴达木—祁连地体表现出较高的数值，在拉萨和羌塘地体表现出较低的数值（234U/238U），但在所有样品中最大值出现在冰川带。在地形崎岖的冰川附近（如祁连山和喜马拉雅山脉）收集的粉尘（234U/238U）值高于在地形平坦的非冰川地区收集的粉尘。这些差异与冰川地区较高的侵蚀速率和粉尘粉碎运输过程是一致的，这是大量新鲜粉碎颗粒的主要来源。与全球其他地区的沉积物相比，典型风成汇（如黄土高原的黄土和冰芯粉尘等）的（234U/238U）值通常低于侵蚀速率高的高海拔地区。TP的（234U/238U）同位素值倾向于落在高海拔站点和粉尘汇之间，表明短粉碎时间（构造、景观动力学和冰川侵蚀）和长停留时间对TP的综合影响。与中亚其他粉尘源相比，TP粉尘的U - Nd - Sr同位素特征明显，可作为粉尘来源的有效示踪剂。利用U同位素，我们发现来自TP的粉尘经历了长距离运输，并构成了亚洲和北半球大气粉尘负荷的潜在重要组成部分。
The production and emission of aeolian dust can provide key information on the contemporary and historical links between geological evolution and climate. Here we use 234U/238U isotope ratios and the uranium (U) comminution age method on samples collected from Qinghai‐Tibet Plateau (TP) surface dust and glacier snowpack/cryoconites to determine the erosion and potential transport provenance of the dust, regardless of petrological origin. The spatial variation of the (234U/238U) isotope ratios of TP dust showed relatively high values in the Songpan‐Ganzi‐Hoh Xil, Himalayan and the Kunlun‐Qaidam‐Qilian terranes, while showing relatively low (234U/238U) values in Lhasa and Qiangtang terranes, but among all samples the highest value appeared in the glaciation zone. Dust collected from nearby glacial areas with rugged terrain (e.g., the Qilian and Himalayan Mountains) have higher (234U/238U) values than those collected in the topologically flat non‐glacial areas. These differences are consistent with elevated erosion rates and dust comminution‐transport processes in glacial areas, which yield a major source for large quantities of fresh comminuted particles. Compared to sediments from other regions of the globe, the (234U/238U) values of the typical aeolian sinks (such as loess on the Loess Plateau and ice core dust, etc.) are generally lower in comparison to areas with high elevations where erosion rates are high. The (234U/238U) isotope values of TP dust tend to fall between the high‐elevation sites and the dust sinks, indicating the combined influence of short comminution times (tectonics, landscape dynamics, and glacial erosion) and long residence time on the TP. When compared with other central Asian dust sources, U‐Nd‐Sr isotope signatures in TP dust are distinct and can be thus used as an effective tracer of dust provenance. Using U isotopes, we show that dust originating from the TP undergoes long‐range transport and constitutes potentially significant component of the Asian and Northern Hemisphere atmospheric dust load.