Collaborative Research: Was early Cenozoic Samoa and Rarotonga volcanism suppressed when the Ontong Java Plateau drifted over the hotspots?

当热岩柱从地幔深处涌出并融化时，海洋热点轨迹就形成了。大约6000万年前，Ontong Java Plateau（OJP）移动到萨摩亚和拉罗汤加的羽状物上。OJP是地球上最大的火山结构。该项目将在大洋洋脊顶部对海山进行取样，以研究羽流与覆盖在其上的大而厚的大洋洋脊之间的相互作用。早期的职业科学家，研究生和本科生将参加巡航。在港口，科学小组将带领当地公立学校和媒体的图尔斯参观。在海上，PI将制作一个培训视频，概述如何准备和进行成功的巡航。最近的工作提供了诱人的线索，目前活跃的萨摩亚热点可能是一个长期存在的地幔熔融异常，或热点，自白垩纪以来一直活跃。位于OJP北部的麦哲伦海山链中的许多87至106 Ma火山具有萨摩亚热点地球化学特征。重要的是，它们的年龄和位置与使用绝对板块运动重建对萨摩亚热点的预测相匹配。确定萨摩亚热点的白垩纪部分（87-106马）的影响是深远的。首先，使用相同的板块运动模型，重建的萨摩亚热点表明，OJP通过萨摩亚羽在~60-30 Ma，并在拉罗汤加羽第二，可能是长寿的热点在~60-50 Ma。第二，萨摩亚和拉罗通加地幔柱上的异常厚的OJP岩石圈的通道将导致较低程度的地幔柱熔融，其富集地幔（EM）特征比沿着萨摩亚和拉罗通加热点轨道的其他任何地方都要强。较厚的岩石圈和较强的EM签名之间的假设关系的支持白垩纪萨摩亚相关的麦哲伦海山，表现出较老（因此较厚）的岩石圈和较强的EM签名之间的强大的关系。一个为期43天的海上疏浚探险采样海山沿着模拟的痕迹，这两个热点轨道上的OJP顶部将测试是否OJP通过萨摩亚和拉罗汤加羽，以及这是否导致极端EM融化的一代。地球化学分析和40 Ar/39 Ar年龄的组合将独特地确定这两个热点的贡献。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Oceanic hotspot tracks form when plumes of hot rock upwell from the deep mantle and melt. Approximately 60 million years ago the Ontong Java Plateau (OJP) moved over the Samoan and Rarotonga plumes. The OJP is the largest volcanic structure on Earth. This project will sample seamounts on top of the OJP to study the interactions between plumes and the overlying large and thick OJP. Early-career scientists, graduate students, and undergraduate students will take part in the cruise. In port the science team will lead ship tours for local public schools and media. While at sea the PIs will make a training video that outlines how to prepare for and carry out a successful cruise. Recent work offers tantalizing hints that the currently active Samoan hotspot may be a long-lived mantle melting anomaly, or hotspot, that has been active since the Cretaceous. Many of the 87 to 106 Ma volcanoes in the Magellan Seamount Chain, located north of the OJP, have Samoan hotspot geochemical signatures. Critically, their ages and locations match predictions for the Samoan hotspot made using absolute plate motion reconstructions. The implications for identifying a Cretaceous segment (87-106 Ma) of the Samoan hotspot are profound. First, using the same plate motion models, reconstructions of the Samoan hotspot show that the OJP passed over the Samoan plume at ~60-30 Ma, and over the Rarotonga plume—a second, possibly-long-lived hotspot—at ~60-50 Ma. Second, passage of the extraordinarily thick OJP lithosphere over the Samoan and Rarotonga plumes would have resulted in lower degree plume melts with stronger enriched mantle (EM) signatures than anywhere else along the Samoan and Rarotonga hotspot tracks. The hypothesized relationship between thicker lithosphere and stronger EM signatures is supported by the Cretaceous Samoa-related Magellan Seamounts, which exhibit a robust relationship between older (and therefore thicker) lithosphere and stronger EM signatures. A 43-day seagoing dredging expedition to sample the seamounts along the modeled traces of these two hotspot tracks on top of the OJP will test whether the OJP passed over the Samoan and Rarotonga plumes, and whether this resulted in generation of extreme EM melts. A combination of geochemical analyses and 40Ar/39Ar ages will uniquely identify contributions from these two hotspots.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.