Lithospheric Controls on Flood Basalt Volcanism

EAR-0309057埃尔金斯-坦顿大陆洪水玄武岩省是一个谜，因为它们在地质记录中很少出现，它们的非凡规模(至少105千米)，它们的形成速度(西伯利亚和其他几个在大约一百万年后完成)，以及它们与其他陆地灾难，包括物种灭绝，陨石撞击和海平面变化，明显或可能的年龄重合。西伯利亚洪水玄武岩省是最大的玄武岩省之一，在时间上也与地球历史上最大的二叠纪物种灭绝密切重合。因此，了解触发和形成大陆溢流玄武岩的过程不仅与地质学和地球物理学有关，而且可能与地球上的生命周期有关，当然也与全球化学系统的相互作用有关。洪水玄武岩是连接地球演化和地球生命演化的纽带。这项工作旨在帮助区分洪水玄武岩形成的相互竞争的理论，更具体地说，是为了更好地理解岩石圈在触发和喷发中的作用。该项目在实验岩石学和数值模拟领域架起了桥梁。这项工作将由P.I.执行，并将构成至少一名布朗大学本科生的本科生论文。这项工作将包括两部分：1.对来自西伯利亚的高镁岩浆进行高压和温度实验，以评估其形成压力和温度；2.进行数值模拟，以研究岩石圈喷发作为岩浆焦点和触发点的作用，并研究克拉通边缘的岩石圈地形及其对烟柱上升的影响。这将是对原始溢流玄武岩成分的首批实验研究之一。实验研究的结果有可能区分需要非常深的热熔融的熔岩模型，以及建议在较低温度下熔化的替代地幔岩性的模型。这些结果可能会显著改变溢流玄武岩的形成模式。

EAR-0309057Elkins-TantonContinental flood basalt provinces are enigmatic due to their infrequency in the geologic record, their remarkable size (at least 105 km3 of lava), their speed of formation (the Siberian and several others were complete in about a million years) and their apparent or possible age coincidences with other terrestrial catastrophes, including extinctions, meteorite impacts, and sea level changes. The Siberian flood basalt province, one of the largest, is also closely coincident in time with the Permian extinction, the largest in Earth history. Understanding the processes that trigger and create continental flood basalts therefore has relevance not only to geology and geophysics, but possibly to cycles of life on earth and certainly to interactions of global chemical systems. Flood basalts are a link between the evolution of the Earth and evolution of life on Earth.The work is designed to help differentiate among competing theories for the formation of flood basalts, and, more specifically, to create better understanding of the role of lithosphere in triggering and eruption. The project bridges the fields of experimental petrology and numerical modeling. The work will be carried out by the P.I. and will also constitute the undergraduate thesis of at least one Brown University undergraduate. The work will consist of two parts: 1. High-pressure and temperature experiments on high-MgO magmas from Siberia to assess their pressure and temperature of formation; and 2. Numerical modeling to study the role of lithospheric foundering as a magmatic focus and trigger, and to study lithospheric topography at the edge of cratons and how it affects plume ascent.This project will be one of the first experimental studies on primitive flood basalt compositions. The results of the experimental study have the potential to differentiate between models for lavas requiring very deep, hot melting, and models suggesting alternative mantle lithologies melting at lower temperatures. These results may significantly alter models for flood basalt formation.