EAGER: Collaborative Research: Has Recent Tectono-Magmatic Activity at Lō'ihi (Kama’ehuakanaloa) Seamount perturbed vent-fluid circulation and hydrothermal Fe export to the oce

EAGER：合作研究：LÅihi (Kamaâehuakanaloa)海山最近的构造岩浆活动扰动了喷口流体循环和热液铁向海洋的输出

• 批准号: 2221282
• 负责人: Chris German
• 金额: $ 24.07万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2221282&HistoricalAwards=false
• 关键词: EAGER; Collaborative; Research; Recent; Tectono

Has Recent Tectono-Magmatic Activity at Lōʻihi (Kamaʻehuakanaloa) Seamount perturbed vent-fluid circulation and hydrothermal Fe export to the ocean?Like volcanoes on land, submarine volcanoes are not continuously erupting but can remain dormant for long periods. Even while dormant, however, the magmatic heat present beneath a volcano’s surface can continue to drive hot springs in between eruptions. The focus of this study is hot springs at the Kamaʻehuakanaloa underwater volcano (previously known as Lōʻihi), situated about 30 miles south of the Big Island of Hawai’i which last erupted in 1996. Prior studies between the mid 2000’s and late 2010’s have shown that the multiple hot-springs associated with that last eruption, at the summit of the volcano have been cooling down continuously. This study will investigate whether two sets of recent earthquakes at Kamaʻehuakanaloa may have altered that cooling trend. In May 2020 earthquakes associated with magma intrusion into the chamber deep within the seamount were detected. In 1996 earthquakes similar to this accompanied a volcanic eruption. More recently still, in December 2021 the strongest earthquakes of any kind since the 1996 eruption were detected. This project will use a deep-diving robot to investigate whether lava was erupted on the seafloor during these earthquakes and also if the composition of the fluids (chemically altered seawater) flowing out of the seafloor at the volcano’s summit has changed.The Lōʻihi seamount (recently renamed Kamaʻehuakanaloa) last erupted in 1996, significantly reshaping its summit and creating three collapse pits. Inside one of these, Pele’s Pit, hot springs have been studied which exhibited temperatures in excess of 200°C immediately post-eruption. Since 2006, however, the multiple sites that have been subject to long-term study within Pele’s Pit and around its rim have shown more modest temperatures of 15-55°C which, further, have exhibited progressive cooling at a rate of 1-2°C over a 12-year period from 2006 to 2018 (the most recent year for which time-series data exist). Thermodynamic modeling of the fluids collected in 2018 has provided new insight that the subsurface hydrothermal circulation within this steep sided seamount may extend much deeper than is typical at mid-ocean ridges (which are more elongate and exhibit shallower-sloping ridge flanks). Further, a geochemical consequence of Lōʻihi’s unusual circulation pattern may account for the unusually Fe-rich nature of the vent-fluids emerging from the seafloor at this intra-plate setting, and their impact on the surrounding ocean, when compared to mid-ocean ridges vents. This project will extend the 2006-2018 time-series of vent studies at Lōʻihi to investigate whether the subsurface hydrothermal circulation system has been perturbed by two significant episodes of seismicity that have subsequently occurred, as detected by the US Geological Survey’s Hawai’i Volcano Observatory. In May 2020, a swarm of earthquakes was detected that were distinctive compared to all seismic activity since the volcano last erupted in May 1996 because they exhibited T-phase activity, recognized as being diagnostic of magmatic fluids migrating within the interior of the seamount and potentially indicative of magma replenishment. In December 2021, an even more pronounced episode of seismicity was detected, up to magnitude M4.9, which matched the strongest earthquakes detected during the 1996 eruptions. This project will use the ROV Jason to investigate whether the seafloor hydrothermal venting at Lōʻihi has been perturbed following these episodes of seismicity. The project will test the hypothesis that the earthquakes, detected by T-phase seismic signals, perturbed the deep hydrothermal circulation cell at Lōʻihi, which in turn should be detectable at the seafloor through changes in vent-fluid temperatures and geochemical compositions. Changes in seafloor morphology and locations of vent-sites compared to the previous ROV dives in 2018 may also be expected. Conversely, the null hypothesis would be that the vent-sites that have been studied since 2006 continue to cool progressively (each vent should then be 6±2°C cooler than when last studied in 2018) with compositions that will have changed accordingly. Importantly, proving this null hypothesis would still be scientifically valuable. It would extend the longest time series available for any intra-plate hydrothermal field worldwide and continue to collect pre-event data in anticipation of future extrusive volcanism at Lōʻihi that will occur.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.

最近的构造-岩浆活动是否干扰了夏威夷海山的喷流循环和热液铁向海洋的输出？像陆地上的火山一样，海底火山不是持续喷发，而是可以长时间处于休眠状态。然而，即使在休眠期间，火山表面下存在的岩浆热量也会在喷发之间继续推动温泉。这项研究的重点是位于夏威夷大岛以南约30英里处的Kama hawehuakanaloa水下火山的温泉（以前被称为lki hawihi），该火山上一次喷发是在1996年。在2000年代中期到2010年代后期之间的先前研究表明，火山顶部与最后一次喷发有关的多个温泉一直在不断冷却。这项研究将调查最近发生在卡马阿瓦卡analoa的两组地震是否改变了这种冷却趋势。2020年5月，与岩浆侵入海山深处的岩浆室有关的地震被探测到。1996年，类似的地震伴随着火山爆发。最近，在2021年12月，人们发现了自1996年火山喷发以来最强烈的地震。这个项目将使用一个深潜机器人来调查在这些地震中海底是否爆发了熔岩，以及从火山山顶流出的流体（化学改变的海水）的成分是否发生了变化。lki - ihi海山（最近更名为Kama - ehuakanaloa）上一次喷发是在1996年，那次喷发极大地改变了它的峰顶，并造成了三个塌陷坑。在其中的贝利坑（Pele’s Pit）里，人们研究过的温泉在喷发后立即显示出超过200°C的温度。然而，自2006年以来，对贝利坑内及其边缘的多个地点进行的长期研究显示，温度更为温和，为15-55°C，而且，在2006年至2018年（有时间序列数据的最近年份）的12年期间，温度以1-2°C的速度逐渐冷却。2018年收集的流体的热力学模型提供了新的见解，即这个陡峭的海山内的地下热液循环可能比典型的海洋中脊（更细长，呈现出较浅的倾斜脊翼）延伸得更深。此外，与洋中脊喷口相比，夏威夷不寻常的环流模式的地球化学结果可能解释了在这种板块内环境下从海底冒出的喷口流体不寻常的富铁性质，以及它们对周围海洋的影响。该项目将延长2006-2018年在夏威夷岛进行的火山口研究时间序列，以调查地下热液循环系统是否受到随后发生的两次重大地震活动的干扰，正如美国地质调查局夏威夷火山观测站所探测到的那样。2020年5月，与1996年5月火山最后一次喷发以来的所有地震活动相比，发现了一群地震，因为它们表现出t相活动，被认为是海山内部岩浆流体迁移的诊断，可能表明岩浆补充。2021年12月，探测到一次更为明显的地震活动，震级高达4.9级，与1996年火山喷发期间探测到的最强地震相匹配。该项目将使用ROV Jason来调查lhi的海底热液喷口是否在这些地震活动事件后受到干扰。该项目将测试一种假设，即通过t相地震信号检测到的地震扰乱了lki - ihi的深层热液循环细胞，而反过来，通过喷口流体温度和地球化学成分的变化，海底应该可以检测到这种循环细胞。与之前的ROV潜水相比，预计2018年海底形态和喷口位置也会发生变化。相反，零假设是，自2006年以来研究的喷口位置继续逐渐冷却（每个喷口届时应比2018年最后一次研究时冷却6±2°C），其成分将相应发生变化。重要的是，证明这个零假设仍然具有科学价值。它将延长世界范围内任何板块内热液场可用的最长时间序列，并继续收集事件前数据，以预测未来在夏威夷将发生的喷发性火山活动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。