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

合作研究：岩床和岩脉系统中的岩浆动力学 - 来自卡鲁大型火成岩省磁性织物和古地磁的约束

• 批准号: 0738685
• 负责人: Stephanie Maes
• 金额: $ 3.35万
• 依托单位: College of Saint Rose
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-15 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0738685&HistoricalAwards=false
• 关键词: Collaborative; Research; Magma; Dynamics; Sill

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.

大陆地壳中的岩浆转移是一个首要问题，需要解决才能理解岩浆系统如何在时间和空间上运作。对于大型火成岩省份来说，这一点尤其重要，在这些省份中，大量岩浆在相对较短的时间内(大约100万年)从源头运往地球表面。磁组构技术，如磁化率各向异性方法，已经成功地约束了流动几何和运动学。然而，这种方法的许多方面仍然模棱两可。例如，没有令人满意的解释来解释这样的情况，即磁性面理平行于岩墙，而被认为模拟流动方向的磁性线理却垂直于岩脉边界。本研究项目通过结合几种独立的方法(图像分析、电子背向散射衍射、磁滞剩磁各向异性)来确定矿物组构和岩浆流动参数来解决这些问题。6个对照实验专门研究了喂与不喂岩脉之间磁性组构的差异，单区磁铁矿颗粒对磁化率各向异性的可能贡献，以及层状形成过程在矿物组构发育中的重要性。实验的目标自然实验室是南非的卡鲁大火成岩省，该地区地图绘制得很好，除了可用的连续钻孔岩心外，还有特殊的暴露。该项目将由来自南伊利诺伊大学、圣罗斯学院和新墨西哥大学的美国研究团队与来自罗兹大学和地球科学委员会的南非科学家合作进行。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。它将定义可以并且应该使用磁化率各向异性技术的边界。这项调查的结果将使更广泛的社区能够更有信心地将这项技术应用到许多其他地质环境中，以确定其结果的重要性。尽管该项目专注于一种类型的岩浆系统(贫硅岩浆)，但其结果很可能会在富含二氧化硅的系统中得到更广泛的应用。这项研究将对火成岩岩石学和火山岩群落产生重大影响，因为岩浆转移仍然是这些学科的关键问题之一。该项目涉及研究生和本科生广泛参与国际研究，并努力扩大未被充分代表的群体对地球科学的参与。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(构造学计划和地球物理计划)支持这项研究。