Quantifying basalt denudation rates and their contribution to the global carbon dioxide budget using cosmogenic Mn-53

使用宇宙成因 Mn-53 量化玄武岩剥蚀率及其对全球二氧化碳预算的贡献

• 批准号: 339625557
• 负责人: Dr. Steven Binnie
• 金额: --
• 依托单位: Scottish Universities Enviromental Research Centre (SUERC)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/339625557?language=en
• 关键词: Quantifying; basalt; denudation; rates; their

Chemical weathering of silicate rocks at the Earth's surface consumes atmospheric carbon dioxide and thus has the potential to influence global climate. In particular, the weathering of basalt rocks could be an important sink for carbon dioxide. Our understanding of what controls the chemical weathering rates of rocks has been limited by our inability to measure rates over the timescales that are relevant to land-forming processes. During the last two decades this situation has improved due to the development of terrestrial cosmogenic nuclide techniques, able to quantify denudation and thus extract rates of chemical weathering over millennial timescales and longer. Basaltic terrains have received little attention in this work, due in part to a lack of suitable target elements for cosmogenic nuclide measurements. However, recent progress has shown cosmogenic Mn-53 is able to quantify denudation rates in iron oxides, which means that it can be measured in basalt. Our overall aim is to take advantage of this new ability and to quantify the importance of basalt weathering as a global atmospheric carbon dioxide sink. To achieve this we will collect samples from two climatically diverse environments: the Paraná flood basalts in humid southern Brazil and the Etendeka flood basalts in arid Namibia. These rocks were originally extruded as one body but were split in two and separated due to the opening of the Atlantic Ocean. While they are lithologically the same, they experience very different amounts of precipitation and both are affected by dramatic temperature gradients. Cosmogenic Mn-53 concentrations in the rock samples will reveal rates of denudation and subsequently the influence that climatic factors have on rates of weathering. Additional investigations into the relationships between chemical and physical weathering, coupled with rates of denudation from nearby non-basaltic lithologies, will allow us to develop a broad understanding of the rates at which basalt weathers and the factors that control theserates.

地球表面硅酸盐岩石的化学风化会消耗大气中的二氧化碳，因此有可能影响全球气候，特别是玄武岩岩石的风化可能是我们对控制二氧化碳化学风化速率的重要了解。由于我们无法测量与土地形成过程相关的时间尺度上的速率，岩石的变化受到限制。在过去的二十年中，由于能够量化的陆地宇宙成因核素技术的发展，这种情况有所改善。在这项工作中，玄武岩地形的剥蚀以及化学风化的提取率很少受到关注，部分原因是缺乏适合宇宙成因核素测量的目标元素。然而，最近的进展表明，宇宙成因 Mn-53 是存在的。能够量化氧化铁的剥蚀率，这意味着可以在玄武岩中测量剥蚀率，我们的总体目标是利用这种新能力并量化玄武岩风化作为全球性的重要性。为了实现这一目标，我们将从两个气候不同的环境中收集样本：潮湿的巴西南部的巴拉那溢流玄武岩和干旱的纳米比亚的埃滕德卡溢流玄武岩这些岩石最初被挤压成一个整体，但被分成两部分并分开。由于大西洋的开口，虽然它们的岩性相同，但它们经历的降水量却截然不同，并且都受到岩石样本中巨大的温度梯度的影响。将揭示剥蚀率以及随后气候因素对风化率的影响，对化学和物理风化之间关系的进一步研究，加上附近非玄武岩岩性的剥蚀率，将使我们能够对风化率有更广泛的了解。玄武岩风化的速率以及控制这些速率的因素。