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.

大约 6000 万年前，当翁通爪哇高原 (OJP) 的热岩柱从地幔深处上升并融化到萨摩亚和拉罗汤加岛柱上时，就会形成海洋热点轨迹。该项目将是地球上最大的火山结构。对 OJP 顶部的海山进行采样，以研究羽流与覆盖的大而厚的 OJP 之间的相互作用。 早期职业科学家、研究生和本科生。在港口，科学团队将带领当地公立学校和媒体参观船舶，而在海上，PI 将制作一个培训视频，概述如何准备和开展一次成功的巡航。暗示目前活跃的萨摩亚热点可能是一个长期存在的地幔融化异常点，或者说热点，自白垩纪以来，麦哲伦火山中的许多火山都一直活跃。位于 OJP 北部的海山链具有萨摩亚热点的地球化学特征，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，这对于识别萨摩亚白垩纪部分（87-106 Ma）具有重要意义。首先，使用相同的板块运动模型，对萨摩亚热点的重建表明，OJP 在约 60-30 点经过萨摩亚羽流。 Ma，以及拉罗汤加地幔柱（第二个可能长期存在的热点），时间约为 60-50Ma 其次，异常厚的 OJP 岩石圈经过萨摩亚和拉罗汤加地幔柱会导致较低程度的地幔柱熔化，且强度更强。比萨摩亚和拉罗汤加热点轨道上的其他任何地方都丰富的地幔（EM）特征支持了较厚的岩石圈和较强的EM特征之间的关系。与白垩纪萨摩亚相关的麦哲伦海山显示出更古老（因此更厚）的岩石圈和更强的电磁特征之间的牢固关系。为期 43 天的海上疏浚探险队沿着这两个热点轨道的模拟痕迹对海山进行了采样。 OJP 将测试 OJP 是否经过萨摩亚和拉罗汤加羽流，以及这是否导致极端电磁熔体的产生。 40Ar/39Ar 年龄将唯一地识别这两个热点的贡献。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。