What is Magnetic in the Lower Crust? Studies from the Athabasca Granulite Terrane, Canada

下地壳中的磁性是什么？

• 批准号: 1045515
• 负责人: Laurie Brown
• 金额: $ 28.95万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-01 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1045515&HistoricalAwards=false
• 关键词: What; Magnetic; Lower; Crust; Studies

The International Decade of Geopotential Research, a global program concentrated on gravity and magnetic data from satellite observations, is drawing to a close with its most ambitious program. SWARM, a trio of satellites to measure magnetic fields, is due to launch in 2011 and will collect an unprecedented amount of field data. One of the goals of the mission is to investigate the magnetism of the Earth's crust, providing a bridge between models for the lower crust from satellite missions to our knowledge from aeromagnetic surveys. Previous studies of satellite data on crustal magnetism have led to models requiring high susceptibility and thick continental crust with strong magnetizations to duplicate the observed fields. Investigations of lower crustal rocks, now uplifted and exposed at the surface due to deformation, do not reveal similarly high susceptibilities, causing us to question magnetic processes in lower crustal rocks. One of the world's largest exposed sections of lower crustal rocks, the Athabasca Granulite Terrain in northern Canada, provides us an excellent place to study first hand the magnetic character of these deep-seated rocks. Aeromagnetic anomaly maps of the region reveal a complex and varied pattern with numerous positive and negative areas; the collection of rock samples from the area will allow us to study the magnetic nature and history of the materials. Results will aid in investigating the history of the Earth's magnetic field, and in unraveling the geologic history of our planet. The nature of the magnetic properties of lower crustal rocks, now exposed at the surface in the Athabasca Granulite Terrain, northern Canada, will aide in answering the question "What is magnetic in the lower crust" Earlier studies of lower crustal rocks exposed at the surface have failed to provide sufficient magnetization to model observed magnetic anomalies from satellite data. Our goal is to provide a detailed interpretation of lower crustal rocks in an area where aeromagnetic studies indicate there are numerous distinct anomalies and link this to satellite observations and models of the lower crust. It is hypothesized that remanent magnetization, possibly due to lamellar magnetization found in hemo-ilmenite rocks, must be a component of the observed magnetizations. Methods will include ground magnetic and susceptibility measurements in situ, collections of rocks from key field locations identified using aeromagnetic anomalies, and laboratory measurements of numerous magnetic properties. Measurements of hysteresis, susceptibility, and magnetization behavior at high and low temperatures along with microscopy studies, both optical and SEM, of well-identified lower crustal rocks will provide detailed information on the magnetic signature, behavior, and mineralogy of the materials responsible for the observed anomalies. All magnetic studies will be keyed to on-going geologic and metamorphic research in the terrain, providing additional constraints, information, and interpretations for aid in answering this question.

国际地势研究的国际十年是一项全球计划，集中在卫星观测的重力和磁数据上，它与最雄心勃勃的计划相结合。 群是测量磁场的三颗卫星，将于2011年推出，并将收集前所未有的现场数据。 该任务的目标之一是研究地球地壳的磁性，为从卫星任务到我们从航空磁调查中的知识的下层地壳之间提供了一个桥梁。先前对卫星磁性数据的研究导致了模型，需要高敏感性和厚厚的大陆地壳，并具有强大的磁性，以复制观察到的磁场。 由于变形而在表面上升高和暴露的下地壳岩石的研究并未显示出类似的高敏感性，从而导致我们质疑下层地壳岩石中的磁过程。 加拿大北部的阿萨巴斯卡颗粒状地形是世界上最大的下地壳岩石裸露部分之一，为我们提供了一个首次研究这些深层岩石的磁性特征的绝佳场所。 该区域的航空磁异常图揭示了一个复杂而变化的模式，具有许多正和负区域。该地区的岩石样品收集将使我们能够研究材料的磁性和历史。结果将有助于研究地球磁场的历史，并揭示我们星球的地质历史。 现在在加拿大北部的Athabasca颗粒状地形的表面暴露的下地壳岩石的磁性特性的性质将有助于回答“下层地壳中的磁性是什么”的问题。 我们的目标是在航空磁研究表明存在许多不同异常的区域中对下层岩石进行详细解释，并将其与卫星观测和下层外壳的模型联系起来。 假设，远期磁化，可能是由于在血铁岩石中发现的层状磁化而引起的，必须是观察到的磁化的组成部分。 方法将包括地面磁性和易感性测量，从使用航空磁异常鉴定的关键田间位置的岩石集合以及众多磁性特性的实验室测量。在高温和低温下的磁滞，易感性和磁化行为以及光学研究（光学和SEM）的测量值良好的下层地壳岩石将提供有关磁性异常的磁性签名，行为和矿物质学的详细信息。 所有磁性研究将被关键在地形中正在进行的地质和变质研究中，从而提供其他约束，信息和解释，以帮助回答这个问题。