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，玄武岩的风化可能是二氧化碳的重要汇。我们对控制岩石化学风化速率的因素的理解一直受到限制，因为我们无法测量与陆地形成过程相关的时间尺度上的速率。在过去的二十年中，由于陆地宇宙成因核素技术的发展，这种情况有所改善，能够量化剥蚀，从而提取千年时间尺度和更长时间的化学风化率。玄武岩地形在这项工作中很少受到关注，部分原因是缺乏合适的目标元素宇宙成因核素测量。然而，最近的进展表明，宇宙成因Mn-53能够量化氧化铁的剥蚀率，这意味着它可以在玄武岩中测量。我们的总体目标是利用这种新的能力，并量化玄武岩风化作为全球大气二氧化碳汇的重要性。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洪水玄武岩和干旱的纳米比亚的Etendeka洪水玄武岩。这些岩石最初被挤压成一个整体，但由于大西洋的开放而一分为二并分开。虽然它们在岩性上相同，但它们经历的降水量非常不同，并且都受到剧烈的温度梯度的影响。岩石样品中的宇宙成因Mn-53浓度将揭示剥蚀速率以及气候因素对风化速率的影响。对化学和物理风化之间关系的进一步调查，以及附近非玄武岩岩性的剥蚀率，将使我们对玄武岩风化的速率和控制这些速率的因素有一个广泛的了解。