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

合作研究：调查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: 1551978
• 负责人: Taryn Lopez
• 金额: $ 9.2万
• 依托单位: University of Alaska Fairbanks Campus
• 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 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551978&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; relationships; among

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延伸到俄罗斯堪察加，绵延约4000公里，北部是轴承海，南部是太平洋。这座弧形火山大约有145座，其中52座是在历史时期喷发的。这些火山的喷发活动范围从持续的小爆炸到毁灭性的大喷发，如1912年在Katmai发生的那次。阿留申弧区的火山活动是太平洋板块俯冲到北美板块之下的结果。在这个过程中，被锁在沉积物和洋壳中的水、碳和氮等挥发性元素慢慢转移到阿留申弧形火山深处的区域。在高压下，挥发物从俯冲板块挤压出来，进入上覆(地幔)区域，在那里它们有助于熔化岩石并产生岩浆。与周围岩石相比，岩浆和挥发物的密度较低，因此这些流体可以上升到地球表面，在那里岩浆最终通过火山作用喷发，气体被释放到大气中。虽然众所周知，挥发物在产生岩浆和影响喷发爆炸性方面都发挥着重要作用，但目前还不太清楚挥发物的来源(俯冲板块、地幔和地壳)和随时间释放的挥发物的量(例如，它们的通量)如何影响火山喷发的规模、爆炸性和频率。该项目旨在限制在研究较少的阿留申西部地区通过火山作用进行挥发性物质俯冲和释放的过程，并提供对火山活动的洞察。阿留申火山弧的西部和中部是研究俯冲角度、速度和沉积物成分对岩浆生成和挥发通量影响的理想地点。从最西端的基斯卡火山到位于弧形中心区域的克利夫兰，俯冲速率和沉积物通量沿弧形增加。此外，与阿留申西部火山相比，阿留申中部火山内历史性喷发的次数似乎更多。通过之前的一次探险，在阿留申西部的五座火山收集了火山气体样本、气体排放测量和爆炸性喷发的熔岩样本。通过这个项目，将分析这些样品的化学和同位素组成，并将使用测量结果来计算二氧化碳、二氧化硫、氮和水进入大气的通量。以前的研究对俯冲到阿留申弧中的物质的数量和类型的限制将与挥发分和熔岩输出的组成以及这里测量的挥发分总通量进行比较，以深入了解挥发分循环和岩浆生成。这些信息将与每个目标火山的喷发规模、类型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，最终帮助改进喷发预测和减灾。