MARGINS: Cl Isotope Systematics of Neogene Izu Arc Volcanic Rocks

边缘：新近纪伊豆弧火山岩的 Cl 同位素系统学

• 批准号: 0549055
• 负责人: Susanne Straub
• 金额: --
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0549055&HistoricalAwards=false
• 关键词: MARGINS; Cl; Isotope; Systematics; Neogene

The Earth remains a habitable planet through continual chemical exchanges between the deep interior (the mantle) and exterior reservoirs (atmosphere, oceans, continental and oceanic crust). Understanding the components of the dynamic Earth System is a central goal of modern research in the geosciences. The 'solid Earth cycle' begins with formation of oceanic crust by mantle melting beneath the globe-encircling mid-ocean ridges. The oceanic crust and the uppermost part of the underlying mantle form a 'slab' of several 10 kilometer thickness that is 'subducted' back to the deep mantle at the deep-sea trenches.'Subduction zones' are a vital part of the Earth system. On land they are recognizable from chains of volcanoes forming 'arcs' parallel to the deep-sea trenches (e.g. the Cascades, Aleutians, Indonesia). Subduction related hazards such as earthquakes, tsunamis and violent explosive eruptions can cause devastating destruction to human life and economics and are known to influence the global climate (e.g. 'year without summer' in 1816 following the 1815 eruption of Mt. Tambora in Indonesia).Such disasters are related directly to the processing of water in subduction zones. Water becomes enriched in the oceanic plate prior to subduction, and is subsequently lost from the slab (along with other volatile elements; e.g. Cl, CO2) during subduction. The processing of water in subduction zones may result in wide-spread 'serpentinization' of the upper mantle, which is the transformation of the dry and brittle peridotite into a hydrous, ductile serpentinite. Such serpentinite rocks may store large amounts of climatically active volatiles (e.g. H2O) that are injected or recycled to the atmosphere through explosive eruptions in arc volcanoes.The Subduction Factory portion of the MARGINS Program addresses the question of how serpentinite formation and destruction influences the volatile fluxes in subduction zones. However, direct geological evidence for serpentinite formation exists only to ~20-25 km depth, and investigation beyond these depths must rely on the chemistry of arc volcanoes. This is a challenging task because the chemistry of arcs reflects the influence of several source components, among which the signature of the serpentinite needs to be identified. Because serpentinite is a sink for the highly fluid-mobile Cl, its isotopes (35Cl, 37Cl) may have unique potential in tracing subduction serpentinization.This project aims to determine the potential of Cl isotopes as tracers of subduction serpentinite in Neogene (up to 20 million year old) volcanic rocks of the Izu Bonin arc (NW Pacific) via analysis of glassy volcanic ash fragments (1 mm). Prior studies by co-PI Susanne Straub revealed high Cl abundances the Izu Bonin arc melts, with the Cl likely derived from the serpentinized mantle below the arc. Cl isotopic analysis in volcanic glass particles will utilize new SIMS (secondary ion mass spectrometry) technology. The study will test for the effects of melt differentiation (e.g. degassing) that might affect the intrinsic isotope ratios. As the first systematic study of Cl isotopes in an arc setting, this work will promote the understanding of Cl isotope fractionation as well as the fluxes of Cl, and likely H2O in the broader geochemical cycle.Broader Impacts: The issues to be addressed are at the core of current research activities on the role of water in subduction zones, and of one of the three fundamental science themes of the MARGINS Subduction Factory Initiative. The project will promote scientific partnership between three key science research institutions in the U.S. Support for women in the geosciences also will furthered. Susanne Straub, a female researcher with a disability, has already made substantial contributions to Izu Bonin magmatism that is a key focus of her research. An undergraduate student will also be involved to work on this project, as this provides an excellent introduction to research.

通过深层内部（地幔）和外部储层（大气，海洋，大陆和海洋地壳）之间的连续化学交换，地球仍然是一个可居住的行星。了解动态地球系统的组成部分是地球科学中现代研究的核心目标。 “固体地球循环”始于地幔在地球上融化的环形中山脊的形成。海洋壳和下面地幔的最上部形成了几个10公里厚度的“平板”，这些厚度是“俯冲”回深海沟槽的深地幔。'Subduction区是地球系统的重要部分。在陆地上，它们是可以从与深海战es（例如级联，阿留申者，印度尼西亚）平行的火山链中识别的。与俯冲相关的危害，例如地震，海啸和暴力爆炸性喷发可能会造成对人类生活和经济学的破坏，并已知会影响全球气候（例如1816年1816年1816年在印第安纳州Tambora山爆发后，1816年的夏季''）与Subcocting Zone of Water of Water of Water of Water of Water of Water of Water of Water of Water of Water of Water of Water of Water of Water of Water。在俯冲之前，水富含海洋板，随后从平板（以及其他挥发性元素；例如CL，CO2）中流失。俯冲带中的水的加工可能会导致上地幔的广泛“蛇纹石化”，这是将干和脆性橄榄岩转化为含水的耐糊状蛇状质。这种蛇形岩石可能会通过弧火山的爆炸性爆发来存储大量的气候活跃挥发物（例如H2O）。但是，直接存在蛇形形成的地质证据仅存在约20-25公里的深度，而这些深度以外的研究必须依赖于弧火山的化学。这是一项具有挑战性的任务，因为ARC的化学反映了几种源成分的影响，其中需要识别蛇纹石的特征。 Because serpentinite is a sink for the highly fluid-mobile Cl, its isotopes (35Cl, 37Cl) may have unique potential in tracing subduction serpentinization.This project aims to determine the potential of Cl isotopes as tracers of subduction serpentinite in Neogene (up to 20 million year old) volcanic rocks of the Izu Bonin arc (NW Pacific) via analysis of glassy volcanic灰烬碎片（1毫米）。 Co-Pi Susanne Straub的先前研究表明，CL的含量很高，Izu Bonin Arc融化了，CL可能源自弧线下方的蛇形化地幔。火山玻璃颗粒中的CL同位素分析将利用新的SIMS（次级离子质谱法）技术。该研究将测试可能影响内在同位素比率的熔体分化（例如脱气）的影响。 As the first systematic study of Cl isotopes in an arc setting, this work will promote the understanding of Cl isotope fractionation as well as the fluxes of Cl, and likely H2O in the broader geochemical cycle.Broader Impacts: The issues to be addressed are at the core of current research activities on the role of water in subduction zones, and of one of the three fundamental science themes of the MARGINS Subduction Factory Initiative.该项目将促进美国三个关键科学研究机构在地球科学中对妇女的支持之间的科学伙伴关系。残疾的女性研究人员苏珊·斯特劳布（Susanne Straub）已经为伊祖·波宁·马格玛特（Izu Bonin Magmatism）做出了重大贡献，这是她研究的重点。本科生还将参与该项目的工作，因为这为研究提供了出色的介绍。