Sr-Nd-Hf isotopic fingerprinting of transatlantic dust derived from North Africa
Sr-Nd-Hf isotopic fingerprinting of transatlantic dust derived from North Africa
复制标题
来自北非的跨大西洋尘埃的 Sr-Nd-Hf 同位素指纹图谱
DOI：
10.1016/j.epsl.2018.01.004
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发表时间：
2018-03-15
影响因子：
5.3
通讯作者：
Ji, Junfeng
中科院分区：
文献类型：
--
作者：
Zhao, Wancang;Balsam, William;Ji, Junfeng
非洲沙尘的远距离传输在理解沙尘与气候的关系方面起着重要作用，包括沙尘源区、沙尘路径和相关的大气和/或海洋过程。粘土大小的Sr-Nd-Hf同位素组成可以作为地球化学指纹来约束粉尘的来源和矿物粉尘的远程输送途径。我们研究了沿撒哈拉沙漠接壤的四个样带表面样品的粘土大小的Sr-Nd-Hf同位素组成。这些横断面来自马里、尼日尔、贝宁、多哥、埃及和摩洛哥。结果表明，西非克拉通（WAC）上马里样带的epsilon(Nd-mean) = -16.38, epsilon(Hf-mean) = -9.59, epsilon（Nd-mean）值较低。埃及样带的Sr-87/Sr-86比值最低（S-87/Sr-86（平均值）= 0.709842），epsilon（Hf）值最高（ε （Hf-平均值）= 0.34），epsilon（Nd）值最高。将北非样品中粘土大小的Sr-Nd-Hf同位素值与在巴巴多斯收集的跨大西洋非洲尘埃进行比较表明，尘埃的来源主要是萨赫勒西部和撒哈拉以及萨赫勒中部。夏季沙尘主要来自萨赫勒西部和撒哈拉地区。春秋两季跨大西洋沙尘的来源比夏季更加多样化，不仅包括西部地区的沙尘，也包括中南部地区的沙尘。跨大西洋沙尘源和汇的Sr-Nd-Hf同位素指纹图谱的比较也表明，沙尘源从冬季到春季再到夏季都向西北方向移动。同位素数据为判别源区古环境演化引起的沙尘档案变化提供了另一种工具。(C) 2018 Elsevier B.V.版权所有
Long-range transport of African dust plays an important role in understanding dust-climate relationships including dust source areas, dust pathways and associated atmospheric and/or oceanic processes. Clay-sized Sr-Nd-Hf isotopic compositions can be used as geochemical fingerprints to constrain dust provenance and the pathways of long-range transported mineral dust. We investigated the clay-sized Sr-Nd-Hf isotopic composition of surface samples along four transects bordering the Sahara Desert. The transects are from Mali, Niger/Benin/Togo, Egypt and Morocco. Our results show that the Mali transect on the West African Craton (WAC) produces lower epsilon(Nd) (epsilon(Nd-mean) = -16.38) and epsilon(Hf) (epsilon(Hf-mean) = -9.59) values than the other three transects. The Egyptian transect exhibits the lowest Sr-87/Sr-86 ratios (S-87/Sr-86(mean) = 0.709842), the highest epsilon(Hf) (epsilon(Hf-mean) = 0.34) and epsilon(Nd) values of the four transects. Comparison of the clay-sized Sr-Nd-Hf isotopic values from our North African samples to transatlantic African dust collected in Barbados demonstrates that the dust's provenance is primarily the western Sahel and Sahara as well as the central Sahel. Summer emission dust is derived mainly from the western Sahel and Sahara regions. The source of transatlantic dust in spring and autumn is more varied than in the summer and includes dust not only from western areas, but also south central areas. Comparison of the Sr-Nd-Hf isotopic fingerprints between the source and sink of transatlantic dust also suggests that a northwestward shift in dust source occurs from the winter, through the spring and into the summer. The isotopic data we develop here provide another tool for discriminating changes in dust archives resulting from paleoenvironmental evolution of source regions. (C) 2018 Elsevier B.V. All rights reserved.