Collaborative Research: North Sister Volcano: A Window into Deep Crustal Processes in a Mafic Arc

合作研究：北姐妹火山：了解镁铁质弧深层地壳过程的窗口

• 批准号: 0230373
• 负责人: A. Dana Johnston
• 金额: $ 13.93万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-04-01 至 2006-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230373&HistoricalAwards=false
• 关键词: Collaborative; Research; North; Sister; Volcano

JohnstonEAR-0230373 Crustal contamination of melts formed in subduction zones is widely accepted for arcs formed on silicic continental crust, but the potentially profound and likely cryptic effects of contamination by mafic crust are not well understood. The intellectual merit of the proposed work is the assessment of processes acting in the deep crust above a subduction zone that affect the magmas rising from the mantle. North Sister volcano of the Cascades volcanic arc is selected for this study because it is the least evolved (mafic) and oldest member of an arc volcano suite represented in the Three Sisters volcanoes, and lies in an unusually mafic segment of arc where the primitive, mantle contributions are constrained. The study's objectives are (1) to identify the compositional variety and proportion of regionally distinctive mantle-derived basalts that contributed to the construction of the basaltic andesite at North Sister; (2) to evaluate how these mantle inputs mix and interact with the deep crust; and (3) to constrain the depth at which the magmatic processes took place. To achieve these goals we will combine compositional and isotopic analysis of rocks selected to represent the age and mineralogical spectrum of lavas sampled during the course of mapping North Sister Volcano. Microanalysis of minerals and their melt inclusions will supplement the bulk rock analyses to discern magmatic histories. Experimental work on natural samples will reveal the pressure, temperature and water conditions under which the North Sister magmas formed. The broader impact of this work includes training in field, analytical and experimental skills of two graduate students, one of which is female and from an underrepresented groups in science. Two undergraduates will also be given research opportunities. The results of the study will be disseminated at national and international meetings and as papers in refereed journals. Technique development for high-pressure experimental work and melt inclusion analysis by laser ablation will contribute to scientific infrastructure. The project is a carefully crafted partnership between Oregon State and University of Oregon taking advantage of complementary facilities and investigator expertise. The proposed work is also of particular societal benefit as it addresses the history of a volcano that is in a particularly active part of the Cascades arc, where recently identified uplift has focused attention on potential volcanic hazards.

JohnstonEAR-0230373对俯冲带形成的熔体的地壳污染被广泛接受为硅质大陆地壳上形成的弧，但镁铁质地壳污染的潜在深远和可能的神秘影响并未得到很好的了解。这项拟议工作的学术价值是评估俯冲带上方地壳深层作用的过程，这些过程影响从地幔上升的岩浆。之所以选择喀斯喀兹火山弧的北姐妹火山进行这项研究，是因为它是三姐妹火山所代表的弧火山组中演化最少(镁铁质)和最古老的成员，并且位于弧内异常镁铁质的部分，原始地幔贡献受到限制。这项研究的目的是(1)确定促成北姐妹玄武岩建造的区域独特的地幔玄武岩的成分种类和比例；(2)评估这些地幔输入如何与深部地壳混合和相互作用；以及(3)限制岩浆作用发生的深度。为了实现这些目标，我们将对在绘制北姐妹火山地图过程中采样的熔岩的年龄和矿物学光谱进行选择的岩石的成分和同位素分析相结合。矿物及其熔体包裹体的微量分析将补充块状岩石分析，以识别岩浆史。对天然样品的实验工作将揭示北姐妹岩浆形成的压力、温度和水条件。这项工作的更广泛影响包括培训两名研究生的实地、分析和实验技能，其中一名是女性，来自科学界代表性不足的群体。两名本科生也将获得研究机会。这项研究的结果将在国家和国际会议上传播，并作为论文发表在相关期刊上。高压实验工作和激光烧蚀熔体包裹体分析技术的发展将有助于科学基础设施的建立。该项目是俄勒冈州立大学和俄勒冈大学之间精心设计的合作伙伴关系，利用互补的设施和调查人员的专业知识。拟议的工作还具有特别的社会效益，因为它涉及一座火山的历史，这座火山位于喀斯喀兹弧形特别活跃的部分，最近发现的隆起将注意力集中在潜在的火山危险上。