Collaborative Research: The influence of incoming plate structure and fluids on arc melt generation at the Lesser Antilles subduction system

俯冲带，即一个构造板块被推到另一个板块之下的地方，是已知的火山和地震灾害丰富的地区。安的列斯群岛是俯冲带火山活动的结果。随着大西洋海底被推入地下，它会下沉，随身携带着大量但未知的水，这些水要么是从裂缝中挤压出来的，要么是在地球更温暖的内部加热时从矿物中失去的。释放的流体在控制地震发生和加强岩浆生成过程中发挥了作用，形成的岩浆向上移动，并为形成岛屿的火山提供食物。该项目将使用电磁方法对安的列斯俯冲系统进行成像。这些数据将被用来识别流体含量高的地区，包括正在俯冲到安的列斯群岛下方的大洋板块中的水和岩浆。更广泛的影响包括与德国和法国的国际合作，以及对早期职业研究人员、研究生和本科生的支持。波多黎各大学的学生将参加实地考察项目。安的列斯群岛被视为一个末端成员系统，在缓慢扩张的中大西洋海脊形成洋壳俯冲，预计将携带大量水束缚在蛇纹化的上地幔内。进入板块的地震成像显示出高度的结构可变性，这表明进入地幔楔形的高流量流体将被局部化。这个项目将把这些局部的高流体流量区域与熔岩的产生联系起来，这些熔体为火山弧提供了养分。电磁(EM)方法是表征流体进入俯冲系统的传输以及随后将这些流体释放到上覆滑脱和地幔楔中的理想方法。电磁方法大致分为两类：被动大地电磁(MT)法，这种方法利用自然产生的信号来寻找大深度(可达200公里或更远)；控制源电磁测深(CSEM)法，将发射器拖到船后，产生人造电磁信号，由一系列海底仪器记录下来。CSEM可用于定量测定地壳和上地幔中的流体。该项目将获得安的列斯俯冲系统的MT/CSEM调查，该调查将检验这样一种假设，即进入板块中储存的较高流体含量导致大量水通量进入下沉板块上方的弧前地壳和弧地幔楔体。流体输入沿走向的变化将表现为地幔传导性的变化，由于释放的流体体积较大，并产生含水熔体，高通量区域的传导性大大增强。实地考察计划将包括两次研究巡航和土地征用。该项目由海洋科学部的海洋地质和地球物理计划和地球科学部的地球物理计划支持。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Subduction zones, where one tectonic plate is pushed beneath another, are known areas of abundant volcanic and seismic hazard. The Antilles islands are the result of such volcanic activity at a subduction zone. As the Atlantic seafloor is pushed down into the earth, it sinks, carrying with it a large, but unknown volume of water that is released, either squeezed from cracks, or lost from minerals as they heat up in the warmer interior of the earth. Released fluids play a role in controlling earthquake generation and enhancing the process of magma generation, with the magma formed moving upwards and feeding the volcanoes that create the islands. This project will use electromagnetic methods to image the Antilles subduction system. These data will be used to identify areas of high fluid content including both water and magma in the oceanic plate that is subducting beneath the Antilles. Broader impacts include international collaborations with Germany and France and support for early career researchers graduate students, and undergraduates. Students from the University of Puerto Rico will participate in the field programs. The Antilles is viewed as an end-member system with subduction of oceanic crust formed at the slow spreading Mid-Atlantic Ridge expected to carry large volumes of water bound within serpentinized upper-mantle. Seismic imaging of the incoming plate shows a high degree of structural variability that suggests that high fluxes of fluids into the mantle wedge will be localized. This project will link these localized areas of high fluid flux to the generation of melts that feed the volcanic arc. Electromagnetic (EM) methods are ideal for characterizing the transport of fluids into a subduction system and the subsequent release of those fluids into the overlying decollement and mantle wedge. EM methods broadly fall into two categories: the passive magnetotelluric (MT) method, which uses naturally occurring signals to look to great depth (up to 200 km or more); and controlled source electromagnetic (CSEM) sounding, in which a transmitter is towed behind a ship and generates an artificial EM signal that is recorded by an array of seafloor instruments. CSEM is useful for quantifying fluids in the crust and uppermost mantle. This project will acquire a MT/CSEM survey across the Antilles subduction system that will test the hypothesis that higher fluid contents stored in the incoming plate results in a substantial water flux into the forearc crust and arc mantle wedge above the downgoing slab. Variations in fluid input along strike will be manifested as variations in mantle conductivity, with regions of high flux being substantially more conductive as a result of the larger volume of fluids released and hydrous melts generated. The field program will consist of two research cruises and land acquisition.This project is supported by the Marine Geology and Geophysics program in the Division of Ocean Sciences and the Geophysics program in the Division of Earth Sciences.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.