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

合作研究：新生代早期的萨摩亚和拉罗汤加火山活动是否因翁通爪哇高原漂移到热点地区而受到抑制？

• 批准号: 2343988
• 负责人: Matthew Jackson
• 金额: $ 34.6万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-07-01 至 2027-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2343988&HistoricalAwards=false
• 关键词: Collaborative; Research; Was; early; Cenozoic

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.

当从深幔和融化的热岩石上向上的热岩羽时，海洋热点会形成。大约6000万年前，安大爪哇高原（OJP）越过萨摩亚和拉罗隆加李子。 OJP是地球上最大的火山结构。该项目将在OJP顶部采样海湾，以研究羽毛与上覆的大和厚的OJP之间的相互作用。早期的科学家，研究生和本科生将参加巡游。在港口，科学团队将领导当地公立学校和媒体的船舶之旅。在海上，PI将制作一个培训视频，概述如何为成功的巡游做准备和进行。最近的工作提供了诱人的提示，即目前活跃的萨摩亚热点可能是寿命长的地幔融化异常或热点，自白垩纪以来一直活跃。位于OJP以北的麦哲伦海山链中的87至106 MA火山中，有许多具有萨摩亚热点地球化学特征。至关重要的是，它们的年龄和位置与使用绝对板运动重建制成的萨摩亚热点的预测相匹配。识别萨摩亚热点的白垩纪片段（87-106 mA）的含义是深刻的。首先，使用相同的板运动模型，萨摩亚热点的重建表明，OJP在〜60-30 ma处经过萨摩亚羽流，以及在Rarotonga羽流上，第二个可能的寿命为较长的热点 - 约60-50 ma。其次，与萨摩亚和rarotonga热点轨道相比，与萨摩亚和rarotonga热点轨道的任何地方相比，萨摩亚和rarotonga羽流的厚度岩石圈的通过会导致较低程度的羽流融化。白垩纪与萨摩亚相关的麦哲伦海峡支持了较厚的岩石圈和更强的EM特征之间的假设关系，这揭示了较老（和较厚）岩石圈和更强的EM特征之间的牢固关系。一项为期43天的海上探险，可在OJP顶部的这两个热点轨道的建模痕迹进行采样，将测试OJP是否经过Samoan和Rarotonga羽流，以及这是否导致了极端EM熔体的产生。地球化学分析和40AR/39AR年龄的结合将独特地确定这两个热点的贡献。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响评估审查标准，被视为通过评估来获得珍贵的支持。