Collaborative Research: Do symmetric and asymmetric segments on the Mid-Atlantic Ridge have distinct geochemical signatures?

大西洋中的大洋中脊将北美和南美与欧洲和非洲分开，是地球上主要的构造板块边界之一。 直到最近，人们才发现，这条海脊由对称和不对称交替扩张的部分组成，这两种扩张的特点是不同类型的地震活动。 海洋地质学中的一个首要问题是：是什么导致了这些差异，它们是否主要与地壳和下地幔的机械或化学性质的差异有关。 这项研究为这个问题提供了新的线索。 它涉及一次密集的实地活动，对六个相邻的对称和不对称扩张的洋中脊段进行取样。 在这一活动期间，将部署深潜工具，以查明以前未发现的热液喷口的存在。从海底挖掘的岩石和玻璃样品将进行岩相学检查，以确定矿物组合，并选择样品进行地球化学分析。 将对选定的样品进行主要和微量元素、挥发物以及Sr、Nd和Pb同位素分析。 还将检查熔体夹杂物。 这些数据将用于确定与更深地幔成分或行为相关的岩浆差异是否是不同类型扩张的原因。 这项工作的更广泛影响包括研究和教育的紧密结合。 这将导致为大学生开设一门关于大洋中脊科学的课程，其中包括分析实验室和海上实地考察部分，课程材料将张贴在网上供传播。 它还将直接培训10多名本科生、两名研究生和两名早期职业研究人员。 收集到的样本和数据将立即向公众提供，由此产生的地球化学分析结果将公布在一个可供公众查阅的网站上。 该项目还涉及与法国科学家合作的一个重要组成部分。

The mid-ocean ridge in the Atlantic that separates North American and South America from Europe and Africa is one of the major tectonic plate boundaries on the planet. Only recently has it become obvious that this ridge consists of segments of alternating symmetric and asymmetric spreading, both of which are characterized by different styles of seismicity. A first order question in marine geology is: what causes these differences and do they primarily relate to differences in the mechanical or chemical properties of the crust and underlying mantle. This research sheds new light on this question. It involves an intensive field campaign to sample six adjacent mid-ocean ridge segments that alternate between symmetric and asymmetric spreading. During the campaign, deep submergence tools to identify the presence of previously undiscovered hydrothermal vents will be deployed. Samples of rock and glass dredged from the seafloor will be examined petrographically for mineral associations and to select samples for geochemical analysis. Selected samples will be analyzed for major and trace elements, volatiles, and Sr, Nd, and Pb isotopes. Melt inclusions will also be examined. These data will be used to determine whether magmatic differences that can be related to deeper mantle composition or behavior are the cause of the different types of spreading. Broader impacts of the work include strong integration of research and education. It will result in the development of a course on mid-ocean ridge science for undergraduates that includes analytical laboratory and seagoing field components, with course materials being posted on the web for dissemination. It will also directly train over 10 undergraduates, two graduate students, and two early career researchers. Samples and data collected will be made immediately available to the public and resulting geochemical analyses will be posted on a publicly accessible website. The project also involves a strong component of collaboration with French scientists.