Collaborative Research: Paleomagnetism and Geochronology of the Mono Lake Event [?] Recorded in the Lava Flow Sequence of Santa Maria Volcano, Guatemala

合作研究：危地马拉圣玛丽亚火山熔岩流序列中记录的莫诺湖事件[？]的古地磁学和地质年代学

• 批准号: 0439155
• 负责人: Jimmy Diehl
• 金额: $ 12.61万
• 依托单位: Michigan Technological University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0439155&HistoricalAwards=false
• 关键词: Collaborative; Research; Paleomagnetism; Geochronology; Mono

Michigan Technological University and the University of Wisconsin-Madison have initiated a collaborative research project to test the hypothesis that the lava flows exposed in the crater wall of Santa Maria Volcano record a geomagnetic excursion known as the Mono Lake Event and that this event is global in extent. The Mono Lake is one of many proposed short-lived periods of geomagnetic instability that riddle Earth's geomagnetic field within longer intervals of constant normal or reversed polarity. Some of these short-lived instabilities affect the geomagnetic field globally whereas others are more local in extent. In either case, these periods of instability or excursions of the geomagnetic field are generally expressed in the rock record by paleomagnetic directions whose variation is outside the normal bounds of secular variation to the point of being almost fully reversed. Excursions which are global and have been dated precisely are important stratigraphic markers and are critical to understanding geodynamo processes. To date, there remains considerable debate as to whether the Mono Lake excursion is a global event as previous studies either are from sediments where dating is problematic and directional data not as reliable as from volcanic rocks or are from studies on volcanic rocks which either lack precise radioisotopic ages, or are based on incomplete paleomagnetic data. Therefore, the objective of this research is to fully characterize the geomagnetic variations (and therefore the Mono Lake Event) recorded by the lava flows exposed in the crater wall of Santa Maria Volcano using paleomagnetic techniques and to precisely determine age of the geomagnetic event using the 40Ar/39Ar incremental heating method. If the 40Ar/39Ar ages bear out the hypothesis that the Santa Maria lava flows record the Mono Lake event, then there is unequivocal evidence that this geomagnetic excursion is global in extent. An addition, well-defined 40Ar/39Ar ages for the lava flows at Santa Maria will place important boundary conditions on the volcanic flux for the latter stages of growth of the Santa Maria's cone.As for broader aspects of this research, Michigan Tech has worked closely with Guatemalan volcanologists at monitoring and hazards agencies (INSIVUMEH and CONRED) for more than 35 years, developing a synergistic relationship where the University has provided access to advanced laboratory and research applications and these volcanologists supply strong field context for obtaining relevant samples. In recent years, several Central American volcanologists have obtained degrees at Michigan Tech. This research will continue that tradition bringing a Guatemalan volcanologist to the United States to study both in the paleomagnetism laboratory at Michigan Tech and to participate in the dating of the Santa Maria lava flows at the University of Wisconsin-Madison. After completing his MS degree, this volcanologist will return to Guatemala where he is expected to provide leadership in important volcanic hazards work for decades.

密歇根理工大学和威斯康星大学麦迪逊分校发起了一个合作研究项目，以检验以下假设：圣玛利亚火山火山口壁中暴露的熔岩流记录了一次被称为莫诺湖事件的地磁漂移，并且该事件是全球性的。 莫诺湖是许多被提出的短暂的地磁不稳定时期之一，这些时期在较长的时间间隔内使地球的地磁场处于恒定的正常或反向极性。 其中一些短暂的不稳定性影响全球地磁场，而另一些则在范围上更具局部性。 在这两种情况下，这些地磁场不稳定或漂移的时期通常在岩石记录中用古地磁方向来表示，其变化超出长期变化的正常范围，几乎完全逆转。 全球性的、精确定年的漂移是重要的地层标志，对理解地球发电机过程至关重要。 到目前为止，莫诺湖的漂移是否是一个全球性事件仍然存在相当大的争议，因为以前的研究要么是来自沉积物，测年是有问题的，方向数据不如火山岩可靠，要么是来自火山岩的研究，要么缺乏精确的放射性同位素年龄，要么是基于不完整的古地磁数据。 因此，本研究的目的是充分表征地磁变化（因此莫诺湖事件）的熔岩流暴露在圣玛利亚火山火山口壁记录使用古地磁技术和精确确定地磁事件的年龄使用40 Ar/39 Ar增量加热方法。 如果40 Ar/39 Ar年龄证实了圣玛利亚熔岩流记录了莫诺湖事件的假设，那么有明确的证据表明，这种地磁漂移是全球范围的。 此外，圣玛利亚熔岩流的40 Ar/39 Ar年龄定义明确，这将为圣玛利亚火山锥生长后期的火山流量提供重要的边界条件。至于这项研究的更广泛方面，密歇根理工大学与危地马拉火山学家在监测和灾害机构密切合作（INSIVUMEH和CONRED）超过35年，发展协同关系，大学提供先进的实验室和研究应用程序，这些火山学家提供强大的现场环境，以获得相关样本。 近年来，几位中美洲火山学家在密歇根理工大学获得了学位。 这项研究将延续这一传统，将一名危地马拉火山学家带到美国，在密歇根理工大学的古地磁实验室进行研究，并参加威斯康星大学麦迪逊分校的圣玛利亚熔岩流的年代测定。 在完成他的硕士学位后，这位火山学家将返回危地马拉，预计他将在数十年内领导重要的火山灾害工作。