Investigating the relationships among subduction character, volatile cycling, and eruptive activity along the Aleutian Arc

研究阿留申弧沿线的俯冲特征、挥发性循环和喷发活动之间的关系

• 批准号: 1551808
• 负责人: Tobias Fischer
• 金额: $ 5.8万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551808&HistoricalAwards=false
• 关键词: Investigating; relationships; among; subduction; character

The Aleutian Volcanic Arc stretches about 4,000 km from mainland Alaska to Kamchatka, Russia, separating the Bearing Sea to the north and the Pacific Ocean to the south. The arc is home to about 145 volcanoes of which 52 have erupted in historic time. The eruptive activity of these volcanoes ranges from continuous small explosions to devastatingly large eruptions such as the one that occurred at Katmai in 1912. Volcanic activity in the Aleutian Arc is a result of subduction of the Pacific plate beneath the North American plate. During this process, volatile elements such as water, carbon and nitrogen that are locked up in the sediments and oceanic crust are slowly transferred into the region deep under the Aleutian Arc volcanoes. Under high pressure the volatiles are squeezed out of the subducting plate into the overlying (mantle) region, where they help to melt rock and generate magma. The lower density of the magma and volatiles compared to the surrounding rock allows these fluids to ascend to the Earth's surface where the magma ultimately erupts through volcanism and the gases are released to the atmosphere. While it is well-known that volatiles play a significant role in both generating magma and influencing eruption explosivity, it is currently not well understood how the source of volatiles (subducted plate, mantle and crust) and the amount of volatiles released over time (e.g. their flux), may influence volcanic eruption size, explosivity and frequency. This project aims to constrain the process of volatile subduction and release through volcanism in the poorly studied Western Aleutians, and to provide insight into volcanic activity. The Western and Central portions of the Aleutian Volcanic Arc are the ideal locations to investigate the influence of subduction angle, rate and sediment composition on magma generation and volatile flux. The subduction rate and sediment flux increases along the arc from Kiska, the western-most volcano, to Cleveland, located within the central region of the arc. Additionally, the number of historic eruptions within Central Aleutian volcanoes appears to be greater in number than compared to the Western Aleutian volcanoes. Through a previous expedition volcanic gas samples, gas emission measurements and explosively erupted lava samples were collected at five Western Aleutian volcanoes. Through this project these samples will be analyzed for their chemical and isotopic composition and measurements will be used to compute the fluxes of carbon dioxide, sulfur dioxide, nitrogen and water to the atmosphere. Constraints on the quantity and type of material subducted into the Aleutian Arc from previous studies will be compared to the composition of volatile and lava outputs, as well as the total flux of volatiles measured here, to provide insight into volatile cycling and magma generation. This information will be compared to historic data on eruption size, style and frequency for each of the target volcanoes to identify possible links between subduction character and volcanic activity, to ultimately help improve eruption forecasting and hazard mitigation.

阿留申火山弧从阿拉斯加大陆到俄罗斯的坎奇特卡延伸约4,000公里，将轴承海与北部和南部的太平洋分开。 弧线是大约145座火山的家园，其中52座在历史时期爆发。 这些火山的爆发活性范围从连续的小爆炸到毁灭性的大型喷发，例如1912年在卡特玛（Katmai）发生的爆发。阿留申弧​​中的火山活性是北美板块下太平洋板块的俯冲的结果。在此过程中，锁定在沉积物中的水，碳和氮等挥发性元素被缓慢地转移到阿留申弧火山下的深处。 在高压下，挥发物从俯冲板中挤出到上覆的（地幔）区域，在那里它们有助于融化岩石并产生岩浆。 与周围的岩石相比，岩浆和挥发物的较低密度使这些流体可以升至地球表面，岩浆最终通过火山爆发，气体释放到大气中。 尽管众所周知，挥发物在产生岩浆和影响喷发爆炸性方面起着重要作用，但目前尚不清楚挥发物（俯冲板，地幔和地壳）的来源如何以及随着时间的推移（例如它们的变化）释放的挥发物量可能会影响伏击的大小，爆炸性，爆炸性，爆炸性，频率。该项目的目的是限制俯冲摇动的过程，并通过火山释放，在研究较差的西方阿留申者中，并洞悉火山活动。阿留申火山弧的西部和中央部分是研究俯冲角，速率和沉积物组成对岩浆产生和挥发性通量的影响的理想位置。俯冲速率和沉积物通量沿弧线从弧线的基斯卡（Kiska）到位于弧线中央区域内的克利夫兰（Cleveland）的弧线增加。此外，与西部的阿留申火山相比，阿留申火山中部火山中的历史爆发数量似乎要大。通过先前的探险火山气体样品，在五座阿留申式火山中收集了气体排放测量和爆炸性爆发的熔岩样品。通过该项目，将分析这些样品的化学和同位素组成，并将测量用于计算大气中二氧化碳，二氧化硫，氮和水的通量。将先前研究中俯冲到阿留申弧的材料的数量和类型的限制与挥发性和熔岩输出的组成以及此处测量的挥发物的总通量进行比较，以洞悉挥发性循环和岩浆的产生。该信息将与每个目标火山的喷发大小，样式和频率的历史数据进行比较，以确定俯冲特征和火山活动之间的可能联系，以最终有助于改善喷发预测和缓解危险。