Pinpointing the Mechanism of Magnetic Enhancement in Modern Soils Using High‐Resolution Magnetic Field Imaging
Pinpointing the Mechanism of Magnetic Enhancement in Modern Soils Using High‐Resolution Magnetic Field Imaging
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DOI：
10.1029/2022gc010812
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发表时间：
2023-03
期刊：
影响因子：
3.7
通讯作者：
R. Fu;B. Maher;J. Nie;Pengdong Gao;T. Berndt;Elizabeth Folsom;Timothy Cavanaugh
中科院分区：
文献类型：
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作者：
R. Fu;B. Maher;J. Nie;Pengdong Gao;T. Berndt;Elizabeth Folsom;Timothy Cavanaugh
在缓冲良好的现代土壤中，较高的年降雨量与土壤亚铁磁性矿物含量增加有关，特别是导致独特岩石磁性的超细颗粒。因此，古土壤磁性已被广泛用作古降水的代用指标。确定一个给定的样品中的磁性增强的主导机制（S）是可靠的推断古沉淀的关键。在这里，我们使用高分辨率磁场和电子显微镜来确定颗粒尺度设置和磁性增强的形成途径，在两个现代土壤中发展较高（10580 mm/y）和较低（10190 mm/y）的降水设置从祁连山，中国。我们发现，这两种土壤都含有1-30 μm的风成氧化铁颗粒，这些颗粒具有不可区分的岩石磁性，而降水量较高的土壤含有额外的超细（<150 nm）磁性不同的磁铁矿颗粒。我们表明，这些超细颗粒的原位沉淀（可能是在干湿循环过程中）是该土壤中唯一显着的磁性增强机制。这些结果表明，量子金刚石显微镜磁显微镜的潜力，从不同的，甚至密切混合，粮食人口提取磁信息。该信息可用于评估不同增强机制对总磁化强度的贡献。
In well‐buffered modern soils, higher annual rainfall is associated with enhanced soil ferrimagnetic mineral content, especially of ultrafine particles that result in distinctive rock magnetic properties. Hence, paleosol magnetism has been widely used as a paleoprecipitation proxy. Identifying the dominant mechanism(s) of magnetic enhancement in a given sample is critical for reliable inference of paleoprecipitation. Here, we use high‐resolution magnetic field and electron microscopy to identify the grain‐scale setting and formation pathway of magnetic enhancement in two modern soils developed in higher (∼580 mm/y) and lower (∼190 mm/y) precipitation settings from the Qilianshan Range, China. We found that both soils contain 1–30 μm aeolian Fe‐oxide grains with indistinguishable rock magnetic properties, while the higher‐precipitation soil contains an additional population of ultrafine (<150 nm) magnetically distinct magnetite grains. We show that the in situ precipitation of these ultrafine particles, likely during wet‐dry cycling, is the only significant magnetic enhancement mechanism in this soil. These results demonstrate the potential of quantum diamond microscope magnetic microscopy to extract magnetic information from distinct, even intimately mixed, grain populations. This information can be used to evaluate the contribution of distinct enhancement mechanisms to the total magnetization.