Collaborative Research: Testing competing models for the origin and magma transport dynamics of the Columbia River LIP

美国西北太平洋地区数百万年来一直受到火山爆发的影响。特别值得注意的是，在1700万到600万年前，许多巨大的火山喷发形成了哥伦比亚河玄武岩（CRB）。CRB熔岩淹没了俄勒冈州和华盛顿州，在数千英尺或更高的地方产生了厚厚的熔岩堆，覆盖了超过15万平方英里的区域。如此大量的熔岩喷涌是地球上最大的火山事件，了解它们是了解地球动态行为基本方面的关键。CRB的熔岩是由裂缝喷发产生的，类似于今天在夏威夷、冰岛或其他玄武岩火山活动活跃的地区所观察到的，但规模要大得多。近年来，人们已经清楚地认识到，这些岩浆可以在地下横向移动很长一段距离，而不是在喷发前从地下的熔融源垂直移动。这项研究将解决CRB岩浆是否在地下长距离移动，以及岩浆储存地点的位置，以更好地了解来自地球内部深处（40公里）的岩浆在哪里上升到地表。这项研究将结合地质年代学、地球化学和岩石磁性技术来检查哥伦比亚河馈线堤内的岩浆流动，从而测试岩浆运输模型。研究了长约400公里的哥伦比亚河岩脉系统中年龄、化学成分和流向的沿走向变化，以约束该大火成岩省（LIP）管道系统的区域尺度岩浆运移动力学。这种多学科方法将为哥伦比亚河LIP堤防提供第一个磁流数据集，并为该省岩浆侵位的时间和动力学提供新的关键约束，这是目前所缺乏的。利用新数据可以解决的与哥伦比亚河LIP岩浆活动有关的关键问题包括：1)哥伦比亚河LIP岩浆是否起源于内华达州-俄勒冈州边界黄石热点的推断起始位置？2)是否存在离散的岩浆储存带，岩浆从那里横向流动到洪水熔岩中？3)岩脉群是在什么时间尺度上形成的？岩浆活动的发生地是否逐渐从黄石热点向北迁移？该项目将支持两所院校的研究生和本科生，并与新西兰奥克兰大学的教师和学生建立国际合作关系。PI团队还将为俄勒冈州和华盛顿州的当地高中教师举办实地研讨会。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。

he Pacific Northwest of the United States is an area that has been impacted by volcanic eruptions for millions of years. Particularly notable are the many huge eruptions that produced the Columbia River Basalts (CRB) between 17 and 6 million years ago. The CRB lavas inundated Oregon and Washington, producing thick stacks of lava, in places of thousands of feet or more, and covering in excess of 150,000 square miles. Such voluminous lava outpourings are Earth’s biggest volcanic events and understanding them is key to understanding fundamental aspects of the dynamic behavior of our planet. Lavas of the CRB were fed from fissure eruptions similar to those observed today on Hawaii, Iceland, or at other areas with active basalt volcanism, but much much larger in scale. In recent years, it has become clear the magmas feeding such events can travel long distances laterally underground, instead of vertically from an underlying melt source prior to their eruption. This study will address whether CRB magmas travelled in the subsurface for long distances, and where the magma storage sites were located, to better understand where magmas from the deep Earth interior ( 40 km) ascended to the surface.This study will combine geochronological, geochemical, and rock magnetic techniques to examine magma flow within Columbia River feeder dikes, and thus will test models of magma transport. Along-strike variations in the age, chemistry, and flow direction in the ~400 km-long Columbia River dike system will be examined to constrain regional-scale magma transport dynamics in the plumbing system of this Large Igneous Province (LIP). This multidisciplinary approach will provide the first dataset of magnetic flow for Columbia River LIP dikes and to supply new and critical constraints on the timing and dynamics of magma emplacement in the province, which are currently lacking. Key questions related to Columbia River LIP magmatism that can be addressed with the new data include: 1) Did Columbia River LIP magmas originate from the inferred inception position of the Yellowstone hotspot at the Nevada-Oregon border? 2) Were there discrete zones of magma storage, from which magma travelled laterally away to feed flood lavas? 3) Over what timescales were dike swarms emplaced, and did the site of magmatism progressively migrate northward away from the Yellowstone hotspot? This project will support graduate and undergraduate students at two institutions, and build an international collaboration with faculty and students at the University of Auckland, NZ. The PI team will also run field workshops for local high school teachers in both Oregon and Washington.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.