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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >The possible role of magnetic measurements in the discrimination of Sahara/Sahel dust sources
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The possible role of magnetic measurements in the discrimination of Sahara/Sahel dust sources

机译：磁测量在区分撒哈拉/萨赫勒尘埃源中的可能作用

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摘要

The mineral magnetic properties of deposited dusts collected along a broadly north-to-south transect across Niger have been investigated on both a bulk and particle size-specific basis. Dusts display a general north-to-south gradient in fine-grained ferrimagnetic mineral (magnetite/maghemite) concentrations, with samples south of the Sahara/Sahel transition (south of ~15·5 ~o N) generally containing greater concentrations than dusts from further north where the climate is much drier. This distinction is seen especially clearly in the clay (< 2μm) fraction, which harbours the products of weathering and pedogenesis. This gradient in ferrimagnetic mineral concentrations broadly parallels that previously reported for surface soils/sands across a similar latitudinal range. We suggest that the regional distinction in both dust and surface soil/sand magnetic properties can be related to differences in weathering regime between the arid Saharan parts of the transect and the Sahel sites where higher rainfall has permitted stronger weathering and pedogenesis. Given that the weathering-related magnetic signatures in the clays dominate the magnetic properties of the<16μm fractions in these samples, and that this particle size component is most likely to be involved in long-range transport, magnetic measurements hold out the potential of discriminating Sahara and Sahel dusts deposited in remote areas.
机译：在整个尼日尔河沿整个北-南横断面收集的沉积粉尘的矿物磁学特性均已进行了研究，具体取决于体积和粒径。粉尘在细粒亚铁磁性矿物（磁铁矿/磁铁矿）的浓度中呈现出从北到南的总体梯度，在撒哈拉/萨赫勒过渡带以南（〜15·5〜o N的南部）的样品所含浓度通常比来自更北，那里的气候更加干燥。这种区别在粘土（<2μm）级分中尤为明显，它包含风化作用和成岩作用的产物。亚铁磁性矿物质浓度的梯度大致平行于先前报道的在类似纬度范围内的表层土壤/沙子。我们认为，灰尘和表层土壤/砂土磁性的区域差异可能与该地区干旱的撒哈拉沙漠地区和萨赫勒地区之间的风化方式不同有关，那里较高的降雨允许更强的风化和成岩作用。鉴于粘土中与风化相关的磁特征主导了这些样品中<16μm馏分的磁性，并且这种粒径成分最有可能参与长距离传输，因此磁法测量具有区分潜力撒哈拉沙漠和萨赫勒尘土沉积在偏远地区。

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