Knowledge Resource Center for Ecological Environment in Arid Area
| 巴丹吉林沙漠物源—地球化学和地貌学证据 | |
| 其他题名 | Geochemical and geomorphological evidence for the provenance of aeolian deposits in the Badain Jaran Desert, northwestern China |
| 胡凡根 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 杨小平 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 摘 要中国北方沙漠是亚洲中纬度沙漠的重要组成部分。由于所处的特殊地理位置，中国北方沙漠是认识地球系统中各圈层相互作用规律的理想研究对象。沙源是沙漠形成的物质基础，识别沙漠的物质来源有助于理解沙漠的形成和演化以及各种地貌过程的相互作用，且对揭示黄土高原黄土的物质来源、搬运路径以及古气候意义也具有重要作用。本文通过对巴丹吉林沙漠风成沙丘表沙、河湖相沉积物及巴丹吉林沙漠东北部苏宏图盆地红色沙丘表沙地球化学特征的系统研究，结合地貌学研究，探讨了巴丹吉林沙漠的物质来源及其对黄土高原粉尘来源的指示意义。研究表明：（1）巴丹吉林沙漠沙丘表沙、河湖相沉积物与苏宏图盆地红色沙丘表沙具有不同的稀土元素分布和元素地球化学特征，虽然巴丹吉林沙漠表沙、河湖相沉积物及苏宏图盆地红色沙丘表沙样品球粒陨石标准化后的稀土元素都呈现出轻稀土元素相对富集、重稀土元素相对亏损、Eu负异常特征，但不同沉积物及颗粒组分之间Ce和Eu异常以及LaN/YbN 、GdN/YbN、LREE/HREE、LaN/SmN比值差别较大，与苏宏图盆地红色沙丘相比，巴丹吉林沙漠的源区物质可能具有相对较低的长石、独居石含量，较低的含Y矿物、含Eu矿物和较高的重矿物含量，反映了二者具有不同的物质来源；（2）地球化学组成及元素比值显示巴丹吉林沙漠表沙和苏宏图盆地红色沙丘表沙的源岩主要为长英质花岗岩、花岗闪长岩和类花岗岩的混合，且其物源区构造背景为大陆岛弧环境；（3）巴丹吉林沙漠沙丘表沙、河湖相沉积物以及苏宏图盆地红色沙丘表沙地球化学特征与其潜在物源区岩石地球化学特征对比表明，巴丹吉林沙漠物源主要来源于祁连山和蒙古戈壁-阿尔泰山风化碎屑物质的混合；苏宏图盆地红色沙丘的物源主要来自阿尔泰山－蒙古戈壁；一方面大量的祁连山风化碎屑物质可通过河流带到黑河冲积扇，这些冲积扇物质在风的作用下源源不断的对巴丹吉林沙漠进行补给；另一方面沙漠北部的阿尔泰山物质和蒙古戈壁广泛存在的河湖相沉积物通过河流和风蚀过程被带入额济纳盆地，最终在风力作用下搬运到巴丹吉林沙漠；然而，阿尔泰山－蒙古戈壁沉积物对巴丹吉林沙漠贡献较小，且主要集中在沙漠北部。巴丹吉林沙漠的最终物源主要来自青藏高原祁连山，其作为青藏高原祁连山重要的沉积汇说明，与青藏高原碎屑物质具有相似锆石年龄谱特征的黄土高原黄土也有可能是在近地面西北风作用下从巴丹吉林沙漠带来。 |
| 英文摘要 | AbstractThe north China deserts, an important part of the middle latitude desert belt of Asia, is ideal object to understand the interaction among various spheres of earth system due to its special geographical location. Badain Jaran Desert is the second largest desert in China and is well known particularly for the occurrence of the tallest dunes on Earth. Much earlier effort has been focused on the formation of the tallest dunes and the interpretation of palaeoenvironments on the basis of aeolian deposits mainly in the desert margins and inter-dune lacustrine sediments. However, the provenance of the sands making the Badain Jaran Desert is still not well understood due to lack of detailed and systematic research. Desert developed on the base of abundant sand meterials. Thus, identifying provenance of deserts is essential for understanding formation and changes of Earth surface processes due to palaeoclimatic fluctuations, and is important to reveal the source material, transport pathway and paleoclimatic implications of loess on Chinese Loess Plateau. In this paper, we present new geochemical data, together with geomorphology study, which provide insight to the provenance of dune sands in the Badain Jaran Desert, northwestern China, an important part of this desert belt. We sampled aeolian and lacustrine sediments in various parts of the Badain Jaran Desert, and examined their major, trace and rare earth elements (REE) in bulk samples, coarse and fine fractions, respectively. In addition, we took and analyzed samples from a rarely known dune field with red sands, northeast of the Badain Jaran. Through systematic geochemical investigation, we get the following results and conclusions: (1) sands from the Badain Jaran Desert are generally different from those in the red sand dune field in terms of REE pattern and geochemical characteristics, although the chondrite-normalized REE distribution patterns of both samples from the Badain Jaran Desert and the red sand dune field are characterized by steep light-REE (LREE) and relatively flat heavy-REE (HREE) shapes and with negative Eu anomalies, but they differ in Ce and Eu anomalies and LaN/YbN, GdN/YbN, LREE/HREE, LaN/SmN ratios; Badain Jaran Desert sand have a relatively low content of feldspar, monazite, Y-bearing and Eu-bearing minerals, and a relatively high content of heavy mineral, comparing to those of the red sand dune field, suggesting different sediment origins between them; (2) Geochemical composition of the aeolian sand samples indicates these sediments should be mainly derived from mixed source rocks of granite, granitoids and granodiorite; (3) Comparing the immobile trace elements and REE ratios of the samples from the Badain Jaran Desert, red sand dune field with rocks of granite, granitoids in their potential source areas indicate that, the aeolian sediments in the Badain Jaran Desert have a mixture of binary provenances, with one derived from Qilian Mountains via the drainage system of the Heihe River, and another from the Altay Mountains and Mongolian Gobi via deflation of northwest winds and alluvial processes; The Altay Mountains and Mongolian Gobi are the ultimate source areas for the red sand dune field. As the Badain Jaran Desert acts as sediment sinks of sediments from the Qilian Mountains of northeastern Tibetan Plateau via fluvial processes, it is likely that zircon grains of loess on the Chinese Loess Plateau with age distributions similar to those of the northern Tibetan Plateau could be derived from the Badain Jaran Desert. |
| 中文关键词 | 巴丹吉林沙漠 ; 地球化学 ; 微量和稀土元素 ; 物源 ; 地表过程 ; 青藏高原祁连山 ; 蒙古戈壁-阿尔泰山 |
| 英文关键词 | Desert Geochemistry Trace and rare earth elements Sediment source Surface process Tibetan Plateau Mongolia China |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地质与地球物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287830 |
| 推荐引用方式 GB/T 7714 | 胡凡根. 巴丹吉林沙漠物源—地球化学和地貌学证据[D]. 中国科学院大学,2017. |
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