Humidity related magnetite alteration in an experimental setup
Humidity related magnetite alteration in an experimental setup
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DOI：
10.1093/gji/ggaa394
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发表时间：
2020-11
影响因子：
2.8
通讯作者：
Qi Zhang;E. Appel;H. Stanjek;J. Byrne;C. Berthold;J. Sorwat;W. Rösler;T. Seemann
中科院分区：
文献类型：
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作者：
Qi Zhang;E. Appel;H. Stanjek;J. Byrne;C. Berthold;J. Sorwat;W. Rösler;T. Seemann
磁铁矿低温氧化(LTO)是在常压条件下发生的，引起磁赤化的一种蚀变过程。利用磁性作为古气候指标，需要更好地理解湿度和温度如何影响这一过程。我们暴露了天然磁铁矿，70°C时粒度在90%之间的天然磁铁矿显示出最强的低温氧化作用，根据TV的分析，氧化度增加了3%，这是唯一通过穆斯堡尔分析表明赤铁矿发生部分蚀变的装置。在70°C的极端干燥条件下(Rh为∼的5%)的样品，以及在70°C的高湿和低湿交替暴露2周的样品，都显示出较小的低温氧化程度。对于∼为13%的中间Rh的样品，观察到最小的高温设置变化。结果表明，磁铁矿蚀变对湿度条件具有非线性敏感性，高湿度强烈有利于蚀变，但当极端湿度与干燥条件交替时，蚀变强烈减弱，这表明季节性在自然风化中的重要性。
Low-temperature oxidation (LTO) of magnetite is an alteration process which occurs under normal atmospheric conditions, causing maghemitization. The use of magnetic properties as palaeoclimate proxies requires improved understanding of how humidity and temperature affect such processes. We exposed natural magnetite, with grain size ranging from 90 per cent at 70 °C showed the strongest degree of LTO with an increase of the oxidation degree by ∼3 per cent according to Tv, and it was the only setup where partial alteration to hematite was indicated by Mössbauer analysis. The sample with extremely dry conditions (rH of ∼5 per cent) at 70 °C, and the sample that was exposed to cycles of high and low humidity in 2-weeks alternation at 70 °C, both revealed a smaller degree of LTO. The smallest change of the high temperature setups was observed for the sample with intermediate rH of ∼13 per cent. The results suggest a non-linear sensitivity of magnetite alteration to humidity conditions, high humidity strongly favours alteration, but alteration is strongly reduced when extreme humidity alternates with dry conditions, suggesting an importance of seasonality in natural weathering.