Collaborative Research: Flood Basalt Magma Genesis and Dynamics: Application of Crystal Isotope Stratigraphy and Igneous Componentry to the Columbia River Basalt Group

大陆洪泛玄武岩是大量岩浆（105 - 107 km3）在地质短时间（=106年）内喷发的产物。尽管人们普遍认为，上升的深根地幔柱为如此强烈的火山活动提供了热源，但在地幔柱的热冲击下，其他地幔和地壳岩石可能会融化，从而贡献了洪水玄武岩总喷发质量的一部分，也许是大部分。评估这些不同来源的岩浆对大陆洪水玄武岩熔岩的相对贡献是一个长期存在的问题。该项目将采用现代的小规模采样方法，针对哥伦比亚河洪水玄武岩的单晶和玄武岩基质内部和之间的关键地球化学示踪剂（主要是同位素比率）。由于这种方法是基于顺序生长的岩石结构，因此这项研究将能够重建岩浆是如何以及以什么顺序从不同的来源聚集的。此外，晶体在寄主岩浆中的停留时间可以通过晶体中同位素丰度比的空间变化的扩散模拟得到，从而限制了个别喷发的持续时间，这是评估这些事件对全球气候和生态破坏的潜在影响的重要参数。在接下来的几年里，所采用的技术将进入火山活动地球化学调查的主流，培训研究生以满足这一需求是该项目的另一个好处。

Continental flood basalts are the products of events in which very large volumes of magma (105 - 107 km3) are erupted in geologically short periods of time (=106 years). Although there is widespread agreement that rising deep-rooted mantle plumes provide the heat source for such intense volcanism, other mantle and crustal rocks may melt under the thermal impact of the plume to contribute some, perhaps most, of the total erupted mass of flood basalt. Assessing the relative contributions of magma from these different sources to continental flood basalt lavas is a long-standing problem. This project will apply modern approaches of small-scale sampling, targeting key geochemical tracers (chiefly isotope ratios) within and between single crystals and basalt matrix, to the Columbia River flood basalts. Because this approach is based on rock textures that grow sequentially, this research will enable reconstruction of how and in what order the magmas were assembled from different sources. In addition, residence times of crystals in their host magmas can be obtained by diffusion modeling of spatial variations in isotope abundance ratios in crystals, allowing constraints to be placed on the durations of individual eruptions, which is an important parameter in assessing the potential these events have for global climate and ecological disruption. Over the next few years, the techniques to be employed will enter the mainstream of geochemical investigations into volcanism, and training research students to meet this need is a further benefit of the project.