Southernmost Patagonia: The Connection Between Magmatism, Subduction Zone, Slab Window and Sub-continental Mantle Lithosphere

地幔约占地球体积的82%和质量的68%，因此，它影响着地球表面的构造板块运动、地震和火山活动。 通过研究玄武熔岩（地幔的部分熔融）来了解地幔的组成和性质的一个基本步骤是建立地球内部挥发物（氢、碳、氟、氯、硫）的预算和分布。挥发分影响着地幔熔融、岩浆结晶、岩浆运移和火山喷发，其丰度和空间分布对地幔流动和温度模型提供了重要的制约。此外，挥发物是地球大气和海洋的关键组成部分，因此，限制地球内部和表面之间的挥发物循环对于理解我们星球的长期演化至关重要，因为它们从根本上影响板块构造，气候和可居住性。该项目将支持布朗大学的一名非洲裔美国女研究生、一名印度研究科学家和一名西班牙裔教授。它促进了与来自三个不同国家（美国、阿根廷和智利）的九个机构的地球化学家的合作，并将加强布朗大学、俄勒冈州州立大学和伍兹霍尔海洋学研究所的研究和教育基础设施。 将通过以下方式通报结果：1）同行评审的期刊，会议上的演讲和邀请的大学讲座，2）为当地小学和高中班级提供实践科学学习活动，3）通过公开讲座向普通观众推广。对于巴塔哥尼亚南部岩浆活动的起源，人们提出了各种各样的假设，从俯冲的纳斯卡和南极板块脱挥发分过程中地幔楔的通量熔融，到通过板窗上涌的碳酸盐和含水软流圈的绝热减压熔融，再到富含挥发分的交代的次大陆岩石圈地幔的熔融。所有提出的假说都援引了挥发分的作用。令人惊讶的是，关于该地区玄武岩和地幔捕虏体的挥发分含量的数据是不存在的。考虑到挥发物的重要性，这是地球化学数据中的一个明显遗漏。本研究的重点将是研究的区域和时间的变化，挥发性成分和地球化学特征的始新世-最近的玄武岩和相关的地幔捕虏体共同位于巴塔哥尼亚南部的地震阵列的微观结构。在这个地区的熔岩和捕虏体较小的熔体体积从当地缺乏稳定状态的岩浆房，经验相对较少的混合和分化，并提供了最好的机会，以确定地幔源的成分，岩性和挥发性成分。将这些地球化学和微观结构数据整合到以前资助的地震实验中，将能够更好地限制巴塔哥尼亚南部地幔的温度、成分、粘度和密度结构。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The Earth's mantle represents approximately 82% by volume and 68% by mass of the Earth, and therefore, it influences the movement of tectonic plates, earthquakes and volcanism on the surface. A fundamental step to understand the composition and nature of the Earth's mantle from the study of basaltic lavas (partial melts of the mantle) is to establish the budget and distribution of volatiles (hydrogen, carbon, fluorine, chlorine, sulfur) in the Earth's interior. Volatiles influence mantle melting, magma crystallization, magma migration and volcanic eruption, and their abundances and spatial distribution provide important constraints on models of mantle flow and temperature. Moreover, volatiles are key constituents of the Earth's atmosphere and oceans and, thus, constraining the cycling of volatiles between the Earth's interior and surface is of fundamental importance to understand the long-term evolution of our planet, as they fundamentally affect plate tectonics, climate, and habitability. The project will support an African-American female graduate student, an Indian research scientist and a Hispanic Professor at Brown University. It promotes the collaboration with geochemists from nine institutions from three different countries: USA, Argentina and Chile, and will enhance the infrastructure for research and education at Brown University, Oregon State University and Woods Hole Oceanographic Institution. Communication of results will occur through: 1) peer-reviewed journals, presentations at conferences and invited university lectures, 2) hands-on science learning activities for local elementary and high school classes, and 3) outreach to the general audience through public lectures.Diverse hypotheses have been proposed for the origin of the magmatism in southern Patagonia, from flux melting of the mantle wedge during devolatilization of the subducted Nazca and Antarctic plate, to adiabatic decompression melting of a carbonated and hydrous asthenosphere upwelling through the slab window, to melting of a volatile-rich metasomatized subcontinental lithospheric mantle. All proposed hypotheses invoke the role of volatiles. Surprisingly, data on the volatile contents of basalts and mantle xenoliths from this region are non-existent. This is a glaring omission from the geochemical data given the importance of volatiles. The focus of this study will be to examine the regional and temporal variations in volatile contents and microstructure of geochemically well-characterized Eocene-recent basalts and associated mantle xenoliths co-located with the seismic array from southern Patagonia. The lavas and their xenoliths in this region represent smaller melt volumes tapped locally from areas lacking steady-state magma chambers, experience relatively less mixing and differentiation, and offer the best opportunity to determine the composition, lithology and volatile contents of the mantle sources. The integration of these geochemical and microstructural data to a previously funded seismic experiment will enable better constraints on the temperature, composition, viscosity and density structure of the mantle beneath southern Patagonia.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.