Low-temperature oxidation of magnetite in rock weathering - a humidity proxy?

岩石风化中磁铁矿的低温氧化 - 湿度代理？

• 批准号: 314584880
• 负责人: Professor Dr. Erwin Appel
• 金额: --
• 依托单位: Arbeitsgruppe Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/314584880?language=en
• 关键词: Low; temperature; oxidation; magnetite; rock

Previous work gave hints that low-temperature oxidation (LTO) of magnetite is a potential proxy of paleo-humidity. In this project, we intend studying LTO in magnetite during rock weathering. The Deccan basalts (W-India) providing strong magnetic und comparable bedrock lithology across a large gradient of mean annual precipitation (MAP of ~200 to >3000 mm/yr) shall serve as study area. We will also check for a possible influence of temperature by comparison with basalts and limestones in SW-China, located in a similar MAP regime but with much cooler conditions. To analyze the LTO effect we suggest performing a systematic study of magnetite alteration along a weathering gradient from non-weathered bedrock, weathered rock surfaces and nearby detached materials, avoiding influence of soil formation. At some of our locations, partners from India and China will add catchment studies. We assume that LTO first increases magnetic hardness of magnetite due to maghemitization, followed by transformation into lower magnetic hematite or goethite. One can identify these processes by bulk measurements, which will be important to use suitable fast-to-measure parameters sensitive for LTO for obtaining high-resolution data sets in reasonable time. The project results could provide important knowledge for paleoclimate studies using lacustrine archives, and may also explain magnetic signals in paleosols.

以前的工作暗示，低温氧化（LTO）的磁铁矿是一个潜在的代理古湿度。在这个项目中，我们打算研究岩石风化过程中磁铁矿的LTO。德干玄武岩（印度西部）应作为研究区，该玄武岩在年平均降水量（MAP约为200至>3000 mm/年）的大梯度范围内提供强磁性和类似的基岩岩性。我们还将通过与中国西南部的玄武岩和石灰岩进行比较来检查温度的可能影响，这些玄武岩和石灰岩位于类似的MAP区域，但条件要冷得多。为了分析LTO效应，我们建议对磁铁矿蚀变进行系统研究，沿着非风化基岩、风化岩石表面和附近分离材料的风化梯度，避免土壤形成的影响。在我们的一些地点，来自印度和中国的合作伙伴将增加集水研究。我们认为，LTO首先增加磁硬度磁铁矿由于磁赤铁矿化，然后转化为低磁性赤铁矿或针铁矿。人们可以通过批量测量来识别这些过程，这对于使用对LTO敏感的合适的快速测量参数以在合理的时间内获得高分辨率数据集将是重要的。该项目的研究结果将为利用湖泊档案研究古气候提供重要的知识，并可能解释古土壤中的磁信号。

项目成果

Humidity related magnetite alteration in an experimental setup

• DOI: 10.1093/gji/ggaa394
• 发表时间: 2020-11
• 期刊: Geophysical Journal International
• 影响因子: 2.8
• 作者: Qi Zhang;E. Appel;H. Stanjek;J. Byrne;C. Berthold;J. Sorwat;W. Rösler;T. Seemann

Nano‐Magnetite Aggregates in Red Soil on Low Magnetic Bedrock, Their Changes During Source‐Sink Transfer, and Implications for Paleoclimate Studies

• DOI: 10.1029/2020jb020588
• 发表时间: 2020-10
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Qi Zhang;E. Appel;Shouyun Hu;R. Pennington;Jannik C. Meyer;U. Neumann;M. Burchard;Frederik J. Allstädt;Long-sheng Wang;A. Koutsodendris