西藏高原典型风尘物源区Sr-Nd同位素地球化学特征研究

发布时间：2018-06-25 19:54

本文选题：风尘 + Sr-Nd同位素　；参考：《昆明理工大学》2017年硕士论文

【摘要】：西藏高原作为世界最高的高原,其在冬夏季节分别作为陆地冷源和热源的中心,大大加强了亚洲大陆东亚季风和南亚季风的强度,对大气环流产生重要影响。同时,由于西藏高原高耸的海拔,冬季高空西风带的运行受到阻碍而分为南北两支,改变了气流的运动轨迹。由于西藏高原地表存在荒漠化区域,其细粒碎屑物质很容易被风所携带,进入高空西风激流带,在北半球高空进行远距离传输,推测,理论上远源风尘应该有来自西藏高原的贡献,故我们选择了这个研究项目。通过对西藏高原地表风尘物质,包括地表砂、黄土、风化物,加上河流砂样的Sr-Nd同位素特征研究,主要依据εNd值将高原划分了 10个同位素特征区,分别为日土分区(εNd:-9.06)、狮泉河分区(εNd:-7.6)、象泉河分区(εNd:-13.3)、措尼分区(εNd:-9.4)、仲巴分区(εNd:-8.9)、申扎分区(εNd:-15.1)、日喀则分区(εNd:-7.6)、山南分区(εNd:-9.5)、拉萨分区(εNd:-5.7)和唐古拉山分区(εNd:-9.38)。这些区域在空间上并不连续,因此划为不同分区。整体而言,各分区稀土元素特征差异并不明显,均反映出上地壳物质的稀土元素分布特征。各分区矿物组成虽然整体相似,但各分区有各自的特点。从西藏高原风尘物(包括地表砂和地表风化物质)的矿物特征分区看,与Sr-Nd同位素特征分区基本一致。矿物特征反映了西藏高原的风尘区域特征矿物以近源风化产物为主,一些区域广泛存在过岩浆、热液活动,区域氧化作用不强,化学风化作用较弱,局部存在蒸发作用。由西藏高原风尘物质的Sr-Nd同位素特征,结合矿物特征,在北太平洋深海沉积物和格陵兰冰芯为代表的远源风尘物质中,可能有部分西藏高原的物质贡献,主要来自雅江河谷和唐古拉山区域,其它区域虽然同位素特征与远源风尘物质相近,但由于区域风尘物质有限,被带入高空西风带的量也有限,因此贡献有限。
[Abstract]:As the highest plateau in the world, Tibet Plateau is the center of land cold source and heat source in winter and summer seasons, which greatly strengthens the intensity of East Asian monsoon and South Asian monsoon on the Asian continent, and has an important influence on the atmospheric circulation. At the same time, because of the high altitude of the Tibetan Plateau, the westerly belt is divided into the north and the south, which changes the track of the airflow. Due to the existence of desertification areas on the surface of the Tibetan Plateau, its fine clastic material is easily carried by the wind and enters the upper-level westerly jet belt for long-range transport at high altitude in the Northern Hemisphere, presumably. In theory, the far source of wind and dust should have contributed from the Tibetan Plateau, so we chose this research project. Based on the study of Sr-Nd isotopic characteristics of surface wind dust materials in Tibet Plateau, including surface sand, loess, weathered materials and river sand samples, the plateau is divided into 10 isotopic characteristic areas according to 蔚 ND value. It is divided into three subzones, namely, Japan (蔚 Nd: -9.06), Shiquan River (蔚 Nd: -7.6), Xiangquan River (蔚 Nd: -13.3), Tawni (蔚 Nd-9.4), Zhongba (蔚 Ndv-8.9), Shenza (蔚 Ndv-15.1), Rikatse (蔚 Nd: -7.6), Shannan (蔚 Nd-9.5), 蔚 Nd-5.7 and 蔚 Nd-9.38. These areas are not spatially contiguous and are therefore divided into different partitions. On the whole, there is no obvious difference in the REE characteristics among the subzones, which reflects the REE distribution of the upper crust material. Although the mineral composition of each subzone is similar as a whole, each zone has its own characteristics. According to the partition of the mineral characteristics of the aeolian dust (including surface sand and surface weathering material) in the Tibetan Plateau, it is basically consistent with the Sr-Nd isotopic zoning. The mineral characteristics show that near source weathering products are the main minerals in the aeolian region of Tibet Plateau. Magma, hydrothermal activity, regional oxidation are not strong, chemical weathering is weak, and local evaporation exists in some regions. Based on the Sr-Nd isotopic characteristics of the aeolian dust materials in the Tibetan Plateau and the mineral characteristics, there may be some material contributions of the Tibetan Plateau in the far source wind dust materials represented by the deep-sea sediments in the North Pacific Ocean and the Greenland ice core. Although the isotopic characteristics of the other regions are similar to those of distant wind dust materials, the contribution of other regions is limited because of the limited amount of regional wind dust materials and the amount brought into the upper level westerly belt.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P597

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