Collaborative Research: Seismic measurements of magma flux, arc composition, and lower-plate serpentinization in the Central American subduction factory

根据这项合同，PIS将对中美洲重点地区哥斯达黎加部分的火山弧、弧后和下行板块进行活动震源地震调查。该计划将重点放在弧形的哥斯达黎加中部，这是熔岩化学显著过渡的地点，因为这里狭窄的地峡非常适合使用陆上-近海技术进行详细的地震成像。这一地点还可以将哥斯达黎加区域地震台网的数据与拟议的区域有源震源阵列结合起来。这一组合将产生该地区弧形地壳结构的详细3D图像。目标是确定基本的地壳结构、成分、综合岩浆流量和弧的分馏过程，并限制向下的科科斯板块岩石圈的水化程度(例如蛇纹岩化)。这项工作涉及以下内容：(1)中美洲弧体的主体成分是什么？由此推断，它的原始岩浆是什么？(2)进入弧内的长期岩浆流量是什么，与其他弧体相比如何？(3)哥斯达黎加弧内横向变化的长度、尺度和程度是什么？(4)洋壳和上地幔的水化状态是否随弧线变化而变化，如果是这样，它是否与弧熔岩的“流体信号”(例如，Ba/La)的变化有关？该计划需要两艘船(地震船和OBS船)，包括大约80天的船期、OBS船，以及与德国人的广泛合作努力和其他正在进行的陆地地震研究。这项研究产生了许多更广泛的影响，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，以及对边际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.