Collaborative research: Quantifying weathering rind formation rates using U-series isotopes along steep gradients of precipitation, bedrock ages, and topography in Guadeloupe

地球表面火山岩的机械和化学分解过程（即风化）调节了全球碳循环，向生态系统释放养分，并塑造了景观。尽管它具有根本性的重要性，但我们仍然缺乏有效的工具和关键的观察结果来量化火山岩的风化速率，并了解它们如何响应气候和构造制度的变化。在风化过程中，土壤中的岩石碎片通常会形成风化层。这些外壳可以提供理想的长期记录，以帮助了解化学风化的控制。研究人员建议将一种新的u系列同位素技术与散装化学、岩石学和电子显微探针分析相结合，以量化法属瓜德罗普岛热带火山Basse-Terre岛风化壳的形成速度。通过对单个流域风化壳的对比，他们将了解风化壳形成的微观控制因素，包括溶蚀、新相的形成和孔隙度的发育。此外，Basse-Terre岛的野外设置提供了一个极好的自然实验室，具有大的环境变量，使他们能够沿着陡峭的降水梯度、基岩年龄和大流域的地形研究环的形成。风化壳的组合分析将为直接测定化学风化速率提供一种新颖而基础的方法。这将对全世界研究从植物冠层顶部延伸到地下水底部的临界带或地球表面层的科学家产生广泛的兴趣。例如，这种方法提供了一种直接的方法来理解不同空间尺度上化学风化的控制。获得的见解还将有助于了解降水的变化如何影响土壤和土壤中的矿物溶解和反应表面，以及这些过程如何在长时间尺度上控制河流化学。该项目汇集了来自美国、法国和英国的资源和专业知识。德克萨斯大学埃尔帕索分校（UTEP）是美国最大的授予博士学位的西班牙裔服务学院之一，迪金森学院是宾夕法尼亚州的一所仅限本科生的文理学院，他们的研究生和本科生将在一个国际关键区研究地点（法国瓜德罗普岛）和宾夕法尼亚州立大学、巴黎环球物理研究所、斯特拉斯堡大学和布里斯托尔大学的研究机构进行研究。对于UTEP和迪金森学院来说，这一点尤为重要，因为学生很少有机会在国际上接触到这样的机会。该项目还将支持UTEP的一位早期职业教师（PI Ma）。UTEP和迪克森学院的教育和推广活动，与NSF资助的Pathways和STEP学者合作，以及UTEP的地球科学日，将使当地高中生和公众在快速发展和多样化的埃尔帕索地区接触到前沿的关键区域研究课题（水，土壤和环境）。该项目将吸引未来的STEM学生，他们希望研究和解决当地社区面临的新环境问题。

The process of mechanical and chemical decomposition of volcanic rocks at the Earth's surface (i.e., weathering) regulates the global carbon cycle, releases nutrients to ecosystems, and sculpts landscapes. Despite its fundamental importance, we still lack effective tools and key observations to quantify the weathering rates of volcanic rocks and to understand how they respond to changes in climate and tectonic regime. During weathering, rock fragments in soils commonly form weathering rinds. These rinds can provide an ideal long-term record to help understand the controls of chemical weathering. Investigators propose to combine a novel U-series isotopic technique with bulk chemical, petrographic, and electron microprobe analyses to quantify formation rates of weathering rinds on the tropical volcanic Basse-Terre Island of French Guadeloupe. By comparing weathering rinds from a single watershed, they will understand the controls on weathering rind formation at the micro-scale through processes including dissolution, formation of new phases, and development of porosity. In addition, the field setting at Basse-Terre Island provides a superb natural laboratory with large environmental variables, allowing them to study rind formation along steep gradients of precipitation, bedrock ages and relief at large watershed scale. The combined analysis of weathering rinds will provide a novel and fundamental method to directly determine chemical weathering rates. This will be of broad interests to scientists worldwide studying the Critical Zone or Earth's surface layer extending from the top of the vegetative canopy to the base of groundwater. For example, such an approach provides a direct means to understand the controls on chemical weathering across different spatial scales. The gained insights will also help to understand how changes in precipitation affect mineral dissolution and reaction surfaces in rinds and soils, and how these processes control river chemistry over long time scales. This project brings together resources and expertise from the U.S., France, and UK. Graduate and undergraduate students at Univ. of Texas at El Paso (UTEP), one of the largest Ph.D.-granting Hispanic Serving Institutes in the U.S., and Dickinson College, an undergraduate-only liberal arts college in Pennsylvania will conduct research at an international Critical Zone research site (Guadeloupe, France) and in research facilities at Pennsylvania State University, Institut de Physique du Globe de Paris, Univ. of Strasbourg, and Univ. of Bristol. This importance is highlighted for UTEP and Dickinson College where the students are rarely exposed to such opportunities at international levels. This project will also support one early career faculty (PI Ma) at UTEP. Educational and outreach activities at UTEP and Dickson College, in collaboration with the NSF funded Pathways and STEP Scholars, as well as Earth Science Day at UTEP, will expose local high school students and general public in the rapidly growing and diverse El Paso region to cutting edge Critical Zone research topics (water, soils, and environments). The project will attract future STEM students who wish to study and solve emerging environmental problems facing the local community.