| 松嫩沙地Sr?Nd同位素组成特征 |
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| 引用本文： | 谢远云,孙磊,康春国,迟云平,刘璐,王嘉新,杜慧荣.松嫩沙地Sr?Nd同位素组成特征[J].沉积学报,2020,38(4):771-780. |
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| 作者姓名： | 谢远云 孙磊 康春国 迟云平 刘璐 王嘉新 杜慧荣 |
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| 作者单位： | 1.哈尔滨师范大学地理科学学院，哈尔滨 150025 |
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| 基金项目： | 国家自然科学基金项目41871013, 41471070, 41601200 |
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| 摘 要： | 作为亚洲风尘源区的中国北方干旱—半干旱地区的Sr?Nd同位素组成已得到很好的研究，但位于欧亚黄土带最东端的松嫩沙地尚是空白，这影响了对该地区风尘系统的深入理解。为此，系统采集了松嫩沙地19个区域90个河流沙和风成沙样品，并对这些样品进行了分粒级处理（<63 μm、63~30 μm、30~10 μm、<10 μm和<30 μm）。对116个分粒级子样的酸不溶物（硅酸盐组分）进行了Sr?Nd同位素组成的测定。研究结果表明，松嫩沙地可划分出两个大区（嫩江水系和松花江水系）和七个小区，嫩江水系沉积物的Nd同位素组成显著高于松花江水系，而Sr同位素组成明显偏低。松嫩沙地8个剖面纵向上的同位素特征显示，Sr?Nd同位素组成存在“时间效应”，即随时间发生了明显变化，表明了源区地球化学组成的不稳定性。分粒级组成表明，粒度对87Sr/86Sr比值的影响很小，但对Nd同位素组成有明显影响，且存在Nd同位素比值富集在粗颗粒组分中的趋势，这与以往的研究结果不同。无论是地质历史时期还是现在，嫩江水系沉积物（大庆、杜蒙、齐齐哈尔、泰来、白城）对哈尔滨粉尘的贡献都很小。哈尔滨黄土与现代尘暴粉尘有不同的物源，哈尔滨黄土是春季尘暴天气作用的产物，有一个混合源，松花江水系沉积物（扶余、德惠、榆树等地）是哈尔滨黄土的主要粉尘源区，内蒙古中东部的沙地也为哈尔滨黄土贡献了部分的细颗粒粉尘。
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| 关 键 词： | Sr?Nd同位素组成 松嫩沙地 哈尔滨黄土 粉尘源区 物源示踪 |
| 收稿时间： | 2019-03-25 |
Sr?Nd Isotopic Partition Characteristics of the Songnen Sandy Land |
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| Institution: | 1.College of Geographic Science, Harbin Normal University, Harbin 150025, China2.Heilongjiang Province Key Laboratory of Geographical Environment Monitoring and Spatial Information Service in Cold Regions, Harbin Normal University, Harbin 150025, China3.Geography Department, Harbin Institute, Harbin 150086, China |
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| Abstract: | Ninety samples from nineteen sites in the Songnen Sandy Land, along with eight L1 loess deposit samples from the Harbin Tianheng mountain, were separated into different grain size fractions (<63 μm, 63?30 μm, 30?10 μm, <10 μm and <30 μm) and 124 acid?insoluble residues of the sub?samples were determined for Sr?Nd isotopic composition. The results showed that the Songnen Sandy Land is divided into two large areas (Nenjiang River drainage and Songhua River drainage) and seven small areas. The Nd isotope composition of sediments in the Nenjiang River Basin is significantly higher than for the Songhua River Basin, while Sr isotope composition is significantly lower. The isotopic characteristics of the eight areas showed that Sr?Nd isotope composition of the Songnen Sandy Land varied obviously with time, referred to as the “time effect”. The Sr?Nd isotopic composition of different grain?size fractions revealed that the particle size had little influence on the Sr isotopic ratio but clearly influenced Nd isotopic composition, with a variation of 2.7 ε units and enrichment in the coars?grained fractions. The time effect on Sr?Nd isotopic composition and the grain?size effect of Nd isotopic composition in the Songnen Sandy Land are well confined within the variation range between the regional samples and thus do not affect their application in pinpointing dust sources. The Sr?Nd isotopic composition presented in this study indicated that the sediments in the Nenjiang River drainage system have contributed very few dust particles to the Harbin eolian deposits throughout the geological past, and that the material sources of Harbin loess was different from modern dust?storm deposits. Harbin loess is the product of spring dust?storm weather and has a mixed source, with the dominant dust particles feeding to the Harbin loess being sediments of the Songhua River drainage (Fuyu, Dehui, and Yushu), but not the Nenjiang River drainage (Daqing, Dumeng, Qiqihar, Tailai and Baicheng). The sandy lands in the middle and eastern parts of Inner Mongolia fed some of the fine particle dust to the Harbin loess. |
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