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

美国太平洋西北部是一个受火山喷发影响了数百万年的地区。尤其值得注意的是，在1700万到600万年前，许多巨大的火山喷发产生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，在数千英尺或更多的地方产生了厚厚的熔岩堆积，覆盖面积超过15万平方英里。如此大量的熔岩喷发是地球上最大的火山事件，了解它们是了解地球动态行为的基本方面的关键。CRB的熔岩来自裂隙喷发，类似于今天在夏威夷、冰岛或其他具有玄武岩活跃火山活动的地区观察到的喷发，但规模要大得多。近年来，很明显，为这类事件提供资金的岩浆可以在地下横向传播很长一段距离，而不是在它们喷发前从底层的熔融源垂直移动。这项研究将探讨CRB岩浆是否在地下进行了长距离的旅行，以及岩浆存储地点的位置，以更好地了解来自地球深处(40公里)的岩浆上升到地表的位置。这项研究将结合地质年代学、地球化学和岩石磁学技术来研究哥伦比亚河支流堤坝内的岩浆流动，从而检验岩浆运输的模型。将研究长约400公里的哥伦比亚河堤防系统中年龄、化学成分和流动方向的沿走向的变化，以限制这个大型火成岩省(LIP)管道系统中区域尺度的岩浆输送动力学。这种多学科方法将为哥伦比亚河唇形堤坝提供第一个磁流数据集，并对该省目前缺乏的岩浆侵位的时间和动力学提供新的关键约束。新数据可以解决的与哥伦比亚河岩浆作用相关的关键问题包括：1)哥伦比亚河嘴唇岩浆是否起源于内华达州-俄勒冈州交界处黄石热点的推断起始位置？2)是否有离散的岩浆储存带，岩浆从那里横向运移到洪水熔岩中？3)岩墙群在什么时间尺度上侵位，以及岩浆活动的地点是否逐渐向北迁移，远离黄石热点？该项目将支持两所大学的研究生和本科生，并与新西兰奥克兰大学的教职员工和学生建立国际合作。PI团队还将在俄勒冈州和华盛顿州为当地高中教师举办实地研讨会。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The 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.