Collaborative Research: Magma Dynamics in Sill and Dike Systems - Constraints From Magnetic Fabrics and Paleomagnetism in the Karoo Large Igneous Province

大陆地壳中的岩浆迁移是一个一级问题，需要解决以了解岩浆系统如何在时间和空间中运作。这一点在大火成岩省的情况下尤其重要，因为从地质学上讲，大量的岩浆在相对较短的时间内（大约100万年）从源头转移到地球表面。磁组构技术，如磁化率各向异性方法，已成功地约束流动的几何形状和运动学。然而，这一方法的许多方面仍然模糊不清。例如，没有令人满意的解释解释的情况下，磁叶理是平行于岩墙，但磁线理，这是应该模仿流动方向，是垂直于岩墙边界。本研究项目通过结合几种独立的方法（图像分析，电子背散射衍射，各向异性的滞回剩磁）来确定矿物组构和岩浆流动参数来解决这些问题。六个控制实验专门研究馈线和非馈线岩脉之间的磁组构的差异，单域磁铁矿颗粒的磁化率各向异性的可能贡献和矿物组构的发展中的层形成过程的重要性。实验的天然实验室是南非的卡鲁大火成岩省，该地区除了可用的连续钻孔岩心外，还具有良好的绘图和特殊的暴露。该项目将由来自南伊利诺伊大学、圣罗斯学院和新墨西哥州大学的美国研究小组与来自南非罗兹大学和地球科学理事会的科学家合作开展。这项研究将为目前最常用于确定岩浆流动方向的磁化率各向异性技术提供理论背景和验证。它将定义磁化率各向异性技术可以和应该使用的边界。这项调查的结果将使更广泛的社区能够将这项技术应用于许多其他地质环境，并对其结果的意义有更大的信心。虽然该项目侧重于一种类型的岩浆系统（硅质贫乏的岩浆），但其结果很可能对富硅质系统有更广泛的应用。由于岩浆迁移仍然是火成岩岩石学和火山岩群落学的核心问题之一，因此，这一研究将对这些学科产生重大影响。该项目涉及研究生和本科生广泛参与国际研究，并努力扩大代表性不足的群体在地球科学中的参与。NSF国际科学与工程办公室（近东和南亚计划）和NSF地球科学部（构造计划和地球物理计划）正在支持这项研究。

Magma transfer in the continental crust is a first order problem that needs to be addressed to understand how magmatic systems operate through time and in space. This is particularly important in the case of Large Igneous Provinces in which large volumes of magma have moved from the source to the surface of the Earth in, geologically speaking, relatively short times (approximately 1 million years). Magnetic fabric techniques, such as the Anisotropy of Magnetic Susceptibility method, have been successful in constraining flow geometry and kinematics. However, numerous aspects of this approach are still ambiguous. For example, no satisfactory explanation accounts for cases where the magnetic foliation is parallel to a dike wall and yet the magnetic lineation, which is supposed to mimic the flow direction, is perpendicular to the dike boundary. This research project addresses these issues by combining several independent methods (image analysis, Electron BackScatter Diffraction, Anisotropy of Anhysteretic Remanent Magnetism) to determine the mineral fabric and magma flow parameters. Six controlled experiments specifically investigate differences in magnetic fabrics between feeder and non-feeder dikes, the possible contribution of single domain magnetite grains to Anisotropy of Magnetic Susceptibility and the importance of layering-forming processes in development of mineral fabric. The natural laboratory targeted for the experiments is the Karoo Large Igneous Province in South Africa, a region with well-mapped, exceptional exposures in addition to available continuous borehole cores. The project will be carried out by a U.S. research team from Southern Illinois University, College of Saint Rose, and University of New Mexico in partnership with South African scientists from Rhodes University and the Council for Geoscience.This study will provide the theoretical background and validation for the technique Anisotropy of Magnetic Susceptibility that is currently the most often used to determine magma flow direction. It will define the boundaries within which the Anisotropy of Magnetic Susceptibility technique could and should be used. The results of this investigation will enable the broader community to apply this technique to many other geological settings with greater confidence regarding the significance of its results. Although the project focuses on one type of magmatic system (silica-poor magmas), it is very likely that the results will have broader applications to silica-rich systems. This research will considerably impact the igneous petrology and volcanic community because magma transfer is still one of the key questions in these disciplines. The project involves extensive graduate and undergraduate participation in international research and makes efforts to broaden participation of underrepresented groups in the Earth Sciences. The NSF Office of International Science and Engineering (Near East and South Asia Program) and the NSF Earth Sciences Division (Tectonics Program and Geophysics Program) are supporting this research.