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

俯冲带，一个构造板块被推到另一个板块的下面，是已知的火山和地震多发地区。安的列斯群岛就是这种火山活动在俯冲带的结果。随着大西洋海底被推入地球，它下沉，带着大量但数量不详的水被释放出来，这些水要么是从裂缝中挤出来的，要么是在地球温暖的内部加热时从矿物质中流失的。释放出来的流体在控制地震产生和加强岩浆生成过程中发挥着作用，岩浆向上流动，为火山提供养分，形成了岛屿。该项目将使用电磁方法对安的列斯俯冲系统进行成像。这些数据将用于确定在安的列斯群岛下俯冲的海洋板块中流体含量高的区域，包括水和岩浆。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。来自波多黎各大学的学生将参加实地项目。安的列斯群岛被认为是一个端元系统，由缓慢扩张的大西洋中脊形成的海洋地壳俯冲而成，预计将在蛇纹石化的上地幔内携带大量的水。进入板块的地震成像显示了高度的结构变异性，这表明进入地幔楔的高通量流体将被定位。该项目将把这些高流体通量的局部区域与为火山弧提供燃料的熔体的产生联系起来。电磁（EM）方法是表征流体进入俯冲系统的运移过程以及随后这些流体释放到上覆的滑脱体和地幔楔体的理想方法。电磁方法大致分为两类：被动大地电磁（MT）方法，它使用自然发生的信号来观察深度（高达200公里或更深）；可控源电磁测深（CSEM），将发射机拖在船后，产生人工电磁信号，由一系列海底仪器记录。CSEM对地壳和上地幔流体的定量分析是有用的。该项目将对整个安的列斯俯冲系统进行MT/CSEM调查，以验证一个假设，即传入板块中储存的较高流体含量导致大量水流入弧前地壳和下沉板块上方的弧幔楔。沿走向流体输入的变化将表现为地幔电导率的变化，由于释放的流体体积较大，产生的含水熔体较大，高通量区域的导电性实质上更强。实地计划将包括两次研究巡航和土地征用。本项目由海洋科学部海洋地质与地球物理项目和地球科学部地球物理项目资助。该奖项反映了美国国家科学基金会的法定使命，并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，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.