Collaborative Research: Beryllium-10 in detrital magnetite as a new tool in erosion and weathering studies

石英中的宇宙成因铍-10（10 Be）被广泛用于量化景观中的侵蚀和风化速率。 10 Be在研究地表过程中很有用，因为它只在地表附近产生，因此可以测量矿物颗粒在土壤中的停留时间。 这些停留时间可以很容易地解释为数百年至数千年的平均侵蚀速率，使其在景观演变和土壤可持续性研究中几乎是理想的。 然而，使用石英存在问题。 它并不存在于所有景观中，其化学制备需要使用危险的氢氟酸，限制了能够处理样品的实验室数量。 该项目将开发磁铁矿中的10 Be，作为确定流域平均侵蚀和风化速率的新工具。 在大多数情况下，磁铁矿的侵蚀速率与石英的侵蚀速率一样有用。 然而，磁铁矿更容易从其他矿物中分离出来，其化学制备的危险性和成本都要低得多。 该项目的贡献将包括开发快速、成本效益高的矿物分离和化学制备技术。 这将为一个全新的研究群体开放10 Be的使用。 该项目将在三个已深入研究侵蚀和风化速率的景观中测试该方法。 此外，还将探索将磁铁矿和石英中的10 Be结合起来使用，作为一种新的、易于测量的流域平均化学风化程度的指标。不久前，测量长期侵蚀和风化的速率极为困难，部分原因是人类观测的时间尺度通常比景观侵蚀的时间尺度短。在过去的20年左右，宇宙成因的核素，如石英中的10 Be，为测量数百至数千年来平均的侵蚀和风化速率提供了新的工具。这推动了对表面过程的定量理解的革命。然而，在某些景观中测量侵蚀速率仍然很困难，因为首选的宇宙成因目标矿物石英并不存在于所有岩石类型中。因此，以宇宙成因为基础的侵蚀率很少在火山景观中测量，例如。此外，宇宙成因核素的所有工作都是在世界各地的几十个实验室中完成的，因为石英不容易为10 Be的分析做准备，并且需要昂贵的专用设备来处理所涉及的大量有害酸。 磁铁矿的使用有可能克服这些困难。 10 Be在其中产生的方式与石英中的方式大致相同。 在许多不含石英的岩石中，它是一种微量矿物。 磁铁矿比石英更容易分离和溶解。 因此，本项目开发的技术有望将10 Be的使用开放给不存在石英的新景观，以及缺乏石英分离和溶解专用设备资源的新研究人员。 磁铁矿和石英风化速率不同。 这提出了一个令人兴奋的可能性，即来自同一条河流的磁铁矿和石英矿物对中的10 Be将产生土壤化学风化的指标。 这项研究将集中在两个NSF的关键区观测站（卢基略和南部塞拉利昂）的实地考察，从而利用现有的基础设施投资研究风化过程及其与地质，气候和生态的关系。

Cosmogenic Beryllium-10 (10Be) in quartz is widely used to quantify rates of erosion and weathering in landscapes. 10Be is useful in the study of surface processes because it is produced only near the ground surface, and thus provides a measure of the residence time of mineral grains in soils. These residence times can be readily interpreted in terms of erosion rates averaged over hundreds to thousands of years, making them nearly ideal in studies of landscape evolution and soil sustainability. There are problems with the use of quartz, however. It is not present in all landscapes and its chemical preparation requires the use of hazardous hydrofluoric acid, limiting the number of laboratories that are able to process samples. This project will develop 10Be in magnetite as a new tool for determining catchment-averaged rates of erosion and weathering. For most purposes, erosion rates from magnetite would be just as useful as erosion rates from quartz. Magnetite, however, is easier to separate from other minerals and its chemical preparation is far less hazardous and expensive. The project's contributions will include development of rapid, cost-effective mineral separation and chemical preparation techniques. This should open the use of 10Be to a whole new community of researchers. The project will test the method in three landscapes where erosion and weathering rates have been intensively studied. In addition, it will explore the coupled use of 10Be in magnetite and quartz as a new, readily measured index of the catchment-averaged degree of chemical weathering.Not long ago, it was extremely difficult to measure long-term rates of erosion and weathering, in part because the timescales of human observation are usually short compared to the timescales of landscape erosion. Over the last 20 or so years, cosmogenic nuclides such as 10Be in quartz have provided new tools for measuring rates of erosion and weathering averaged over hundreds to thousands of years. This has fueled a revolution in quantitative understanding of surface processes. Yet measurements of erosion rates in some landscapes have remained difficult because the preferred cosmogenic target mineral, quartz, is not present in all rock types. Hence cosmogenic-based erosion rates have rarely been measured in volcanic landscapes, for example. Moreover, all of the work on cosmogenic nuclides is done in just a few dozen labs around the world because quartz is not easy to prepare for analysis of 10Be, and costly, specialized equipment is needed to handle the large volumes of hazardous acids that are involved. Usage of the mineral magnetite has the potential to overcome these difficulties. 10Be is produced within it in much the same way as it is in quartz. It is present as a trace mineral in many rocks where quartz is absent. Moreover, magnetite is easier to separate and dissolve than quartz. Hence, techniques developed in this project promise to open the use of 10Be to new landscapes where quartz is absent, and also to new researchers who lack resources for the specialized equipment of quartz separation and dissolution. Magnetite and quartz weather at different rates. This raises the exciting possibility that 10Be in the mineral pair magnetite and quartz from the same stream will yield an index of chemical weathering in soil. This research will focus on fieldwork at two of NSF's Critical Zone Observatories (Luquillo and Southern Sierra), thus capitalizing on existing infrastructure investment for studying weathering processes and their relationships with geology, climate, and ecology.