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

地球动力学中一个悬而未决的主要问题是，太平洋的主要热点，如夏威夷和路易斯维尔热点，是否经历了类似的羽流运动，或者它们是否独立运动。2010年12月，IODP 330考察队前往路易斯维尔海山小径，开始回答这个关键问题。初步的船载古地磁数据（尽管基于有限的船载采样）清楚地表明，路易斯维尔热点并没有像夏威夷热点记录的那样在80到50 Ma之间经历15°的古纬度大位移。至关重要的是，这些船上的数据既不能估计个别钻探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（大约一半还没有数据或只有一个样本）。同样重要的是，大量的（主要是海底的）火山碎屑物质的回收使得估算古纬度不像在夏威夷-皇帝小径上的遗址那么简单，在那里，一个离散的序列(主要是可能被期望有随机的方向，而不是有一致的倾斜度，类似于那些嵌入的熔岩流，因此可能提供有价值的古纬度信息。因此，支持者建议额外的40ar / 39ar年龄测定，古地磁和岩石地磁研究，以及整合额外的岸基和船上数据（例如钻孔磁异常），这将允许解决以下问题：建立330考察队钻探的火山序列需要多长时间？这些间隔（以及相关的静息期）是否足够长，足以平均出长期变化？路易斯维尔海山有后侵蚀火山活动吗？如果有，持续多久？在一些火山碎屑单元中，一致的倾角的起源是什么？这些是否提供了一个时间平均的残留物，可以改善古纬度的估计？路易斯维尔海山的倾角数据是否足够相似，足以从汇总数据中提供可靠的古纬度？我们能否利用路易斯维尔热点的年龄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)为路易斯维尔海山路径上的火山活动提供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，(3)有助于改善考虑夏威夷和路易斯维尔个别热点（缺乏）运动的太平洋板块绝对运动模型。更广泛的影响和教育推广：拟议的项目是国际合作努力的一部分，以支持IODP远征330到路易斯维尔海山小径的科学目标。支持者正在与来自日本、英国和澳大利亚的8位国际研究人员合作，他们将与他们一起生成尽可能完整和急需的高精度40ar / 39ar和古地磁数据集。倡议者将在我们项目的两年时间里协调这些共同努力，最终目标是为路易斯维尔热点描绘出最准确的古纬度和年龄历史。他们还将组织一系列外展活动，包括扩展由Koppers创建的Expedition 330网站，通过添加该项目产生的科学产品和数据集，并将这些产品和数据集与在线海底山目录和MagIC连接起来。这项工作将成为俄勒冈州立大学和SIO两名学生博士论文的一部分。

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.