Collaborative Research: High Precision 40Ar/39Ar Geochronology and Paleomagnetism to Determine the History and Consequences of Louisville Mantle Plume Motion

合作研究：高精度 40Ar/39Ar 地质年代学和古地磁学以确定路易斯维尔地幔柱运动的历史和后果

• 批准号: 1154675
• 负责人: Jeffrey Gee
• 金额: $ 14.07万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1154675&HistoricalAwards=false
• 关键词: Collaborative; Research; Precision; 40Ar; 39Ar

A major outstanding question in geodynamics is whether primary hotspots in the Pacific, like the Hawaiian and Louisville hotspots, experienced similar amounts of plume motion or whether they moved independently. In December 2010 IODP Expedition 330 to the Louisville seamount trail set out to answer this critical question. Preliminary shipboard paleomagnetic data (although based upon limited shipboard sampling) clearly show the Louisville hotspot did not experience the same large 15° shift in paleolatitude as recorded for the Hawaiian hotspot between 80 and 50 Ma. Critically, these shipboard data neither allow for estimates of the duration of volcanism at individual sites drilled nor for the inclination of many cooling units (about half have no data yet or only a single sample). As importantly, the abundance of (mostly submarine) volcaniclastic material recovered makes estimating the paleolatitudes less straightforward than for the sites on the Hawaii-Emperor trail, where a sequence of discrete (primarilythat might be expected to have random directions, instead have consistent inclinations that are similar to those of intercalated lava flows and therefore may provide valuable paleolatitude information. The proponents therefore propose additional 40 Ar/39 Ar age determinations, paleomagnetic and rock magnetic studies, and integration of additional shore-based and shipboard data (e.g. borehole magnetic anomalies) that will allow the to address the following questions: 1. How long did it take to build the volcanic sequences drilled during Expedition 330 and are these intervals (and associated quiescence periods) long enough to average out secular variation?2. Do Louisville seamounts have post-erosional volcanism and if so what is its duration?3. What is the origin of consistent inclinations in some volcaniclastic units and do these provide a time-averaged remanence that can improve paleolatitude estimates?4. Are the inclination data from the Louisville seamounts sufficiently similar to provide a robust paleolatitude from pooled data?5. Can we use the ages and paleolatitude history of the Louisville hotspot to improve absolute plate motion models for Pacific plate? The results of this study will allow the proponents to (1) provide the most accurate and precise age framework for volcanic activity along the Louisville seamount trail, (2) to significantly reduce on the uncertainties in paleolatitude estimates, and (3) help to improve absolute plate motion model for the Pacific Plate taking into account the (lack of) motion of the individual Hawaiian and Louisville hotspots.Broader Impact and Educational Outreach: The proposed project is part of an international collaborative effort in support of the science objectives of IODP Expedition 330 to the Louisville Seamount Trail. The proponents are collaborating with eight international researchers from Japan, UK and Australia, with whom they will generate as complete as possible and much needed high-precision 40 Ar/39 Ar and paleomagnetic data sets. The Proponents will coordinate this concerted effort over the two years of our project, with the ultimate goal to delineate the most accurate paleolatitude and age history for the Louisville hotspot. They also will organize a series of outreach activities, including expanding the Expedition 330 website started by Koppers by adding scientific products and data sets resulting from this project and by linking these in with the online Seamount Catalog and MagIC. This work will be part of the Ph.D.thesis of two students at OSU and SIO.

地球动力学中的一个重大悬而未决的问题是，太平洋上的主要热点，如夏威夷和路易斯维尔的热点，是经历了类似数量的羽流运动，还是它们独立运动。2010年12月，IODP第330次路易斯维尔海山小道考察队开始着手回答这一关键问题。初步的船上古地磁数据(尽管基于有限的船上采样)清楚地表明，路易斯维尔热点没有经历像夏威夷热点在80至50 Ma之间记录的那样大的15°古纬度移动。关键的是，这些船上的数据既不能估计所钻探的个别地点的火山活动持续时间，也不能估计许多冷却装置的倾斜度(大约一半的人还没有数据或只有一个样本)。同样重要的是，由于发现了丰富的火山碎屑物质(主要是海底火山碎屑物质)，因此估算古纬度比夏威夷-帝王路线上的遗址要困难得多，在那里，一系列离散的(主要是海底的)火山碎屑物质可能具有随机的方向，相反，它们具有类似于夹层熔岩流的一致倾角，因此可能提供宝贵的古纬度信息。因此，支持者提出了额外的40Ar/39Ar年龄测定、古地磁和岩石磁学研究，以及额外的岸基和船上数据的整合(例如，钻孔磁异常)，这将使他们能够解决以下问题：1.建立在330次探险期间钻探的火山序列需要多长时间，这些间隔(和相关的静止期)是否足够长，足以平均出长期变化？2.路易斯维尔海山是否有侵蚀后火山作用，如果有，持续时间是多久？3.一些火山碎屑单元倾角一致的原因是什么，这些是否提供了足够的时间平均剩余，可以改善古纬度估计？4.路易斯维尔海山的倾角数据是否来自路易斯维尔海山5.我们能否利用路易斯维尔热点的年代和古纬度历史来改进太平洋板块的绝对板块运动模型？这项研究的结果将使支持者能够(1)提供路易斯维尔海山踪迹沿线火山活动的最准确和精确的年龄框架，(2)显著减少古纬度估计中的不确定性，以及(3)考虑到个别夏威夷和路易斯维尔热点的(缺乏)运动，有助于改进太平洋板块的绝对板块运动模型。广泛的影响和教育推广：拟议的项目是支持IODP 330对路易斯维尔海山踪迹的科学目标的国际合作努力的一部分。倡导者正在与来自日本、英国和澳大利亚的8名国际研究人员合作，他们将与他们一起生成尽可能完整和迫切需要的高精度40Ar/39Ar和古地磁数据集。支持者将在我们项目的两年时间里协调这一协调努力，最终目标是描绘路易斯维尔热点地区最准确的古纬度和年龄历史。他们还将组织一系列外联活动，包括扩展Koppers启动的Expedition330网站，增加该项目产生的科学产品和数据集，并将其与在线海山目录和MAGIC链接。这项工作将是俄亥俄州立大学和西澳州立大学两名学生博士论文的一部分。