Collaborative Research: Seismic Measurements of Magma Flux, Arc Composition, and Lower-Plate Serpentinization in the Central American Subduction Factory

根据该合同，PI将在中美洲焦点地点的哥斯达黎加部分对火山弧、弧后和下行板块进行有源地震调查。该计划的重点是弧的哥斯达黎加中部部分，这是一个熔岩化学显著转变的地点，因为这里狭窄的地峡非常适合使用陆上-海上技术进行详细的地震成像。这一位置还使哥斯达黎加区域地震网络的数据能够与拟议的区域有源阵列相结合。这种组合将产生该地区弧形地壳结构的详细三维图像。目标是确定基本的地壳结构、成分、综合岩浆通量和弧的分馏过程，并限制水化程度（例如，蛇纹岩化作用）。这项工作解决了以下问题：（1）什么是中美洲弧的整体组成，并通过推理，其原始岩浆？(2)长期岩浆流入弧的流量是多少，与其他弧相比如何？(3)哥斯达黎加弧的长度尺度和横向变化程度是什么？(4)洋壳和上地幔的水化状态是否沿弧沿着变化，如果是，它是否与“流体信号”的变化相关（例如，Ba/La）的弧熔岩？该计划需要两艘船（地震船和OBS船），包括大约80天的船时间，OBS的，以及与德国和其他正在进行的陆地地震研究的广泛合作。该研究具有一些更广泛的影响，包括研究生的广泛参与，教师培训活动，与德国和哥斯达黎加科学家的国际合作，以及对MARGINS计划目标的高度重视。

Under this award, the PIs will carry out an active-source seismic investigation of the volcanic arc, backarc, and downgoing plate in the Costa Rican portion of the Central American Focus Site. The program focuses on the central Costa Rican segment of the arc, a site of marked transitions in lava chemistry, because the narrow isthmus here is well-suited for detailed seismic imaging using onshore-offshore techniques. This location also enables the incorporation of data from the regional Costa Rican seismic network with the proposed areal active-source array. This combination will result in a detailed 3D image of arc crustal structure in the area. The goals are to determine the basic crustal architecture, composition, integrated magma flux, and fractionation processes of the arc, and to constrain the degree of hydration (e.g., serpentinization) in the downgoing Cocos Plate lithosphere. The work addresses the following: (1) What is the bulk composition of the Central American arc and, by inference, of its primary magma? (2) What is the long-term magma flux into the arc, and how does it compare to other arcs? (3) What are the length scales and degree of lateral variability in the Costa Rica arc? (4) Does the state of hydration of oceanic crust and upper mantle vary along the arc, and if so, does it correlate with changes in the "fluid signal" (e.g., Ba/La) of arc lavas? The program entails two ships (seismic ship and OBS ship), including about 80 days of ship time, OBS's, and extensive collaborative efforts with Germans and other ongoing seismic studies on land. The study has a number of broader impacts, including the extensive involvement of graduate students, teacher training activities, international collaboration with German and Costa Rican scientists, and high importance to the goals of the MARGINS program.