EAGER: Collaborative Research: Has Recent Tectono-Magmatic Activity at Loihi (Kamaehuakanaloa) Seamount perturbed vent-fluid circulation and hydrothermal Fe export to the ocean?

在洛伊希（卡马埃瓦卡纳洛阿）海山最近的构造-岩浆活动扰动了喷口流体循环和热液铁输出到海洋吗？像陆地上的火山一样，海底火山不会持续喷发，但可以长期休眠。然而，即使在休眠期，火山表面下的岩浆热也可以在喷发之间继续驱动温泉。这项研究的重点是卡马瓦卡纳洛亚水下火山（以前称为洛伊希）的温泉，位于夏威夷大岛以南约30英里处，最后一次喷发是在1996年。2000年代中期至2010年代后期的研究表明，与火山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玛瓦卡纳洛亚的两次地震是否改变了这种冷却趋势。2020年5月，监测到与岩浆侵入海山深处的岩浆房有关的地震。1996年，类似的地震伴随着火山爆发。最近，在2021年12月检测到自1996年爆发以来最强烈的地震。该项目将使用深潜机器人，调查在地震期间海底是否有熔岩喷发，以及从火山顶部流出的海底流体（化学变化的海水）的成分是否发生变化。洛伊希海山（最近更名为卡马瓦卡纳洛亚）上一次喷发是在1996年，其山顶发生了重大变化，并产生了三个塌陷坑。 在其中一个，贝利坑，温泉已被研究，显示温度超过200°C立即爆发后。 然而，自2006年以来，在贝利坑内及其边缘进行长期研究的多个地点显示出15-55°C的温和温度，并且在2006年至2018年的12年间（时间序列数据存在的最近年份）以1-2°C的速度逐渐冷却。 对2018年收集的流体进行的热力学建模提供了新的见解，即这个陡峭的海山内的地下热液循环可能比大洋中脊的典型情况（更长，并且具有较浅的斜坡脊侧面）延伸得更深。此外，Lōzihi不寻常的环流模式的地球化学后果可能解释了在这个板内环境中从海底出现的喷口流体的异常富铁性质，以及它们对周围海洋的影响，与大洋中脊喷口相比。该项目将延长2006-2018年对洛伊希火山口的时间序列研究，以调查地下热液循环系统是否受到美国地质调查局夏威夷火山观测站探测到的随后发生的两次重大地震活动的干扰。 2020年5月，监测到一系列地震，与1996年5月火山最后一次爆发以来的所有地震活动相比，这些地震是独特的，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特征，并可能表明岩浆补充。2021年12月，监测到一次更明显的地震活动，震级高达M4. 9级，与1996年火山爆发期间监测到的最强地震相当。该项目将利用“Jason”号探测器调查在这些地震活动事件之后，洛伊希的海底热液喷发是否受到了扰动。 该项目将检验一种假设，即由T相地震信号探测到的地震扰动了洛伊希的深层热液循环单元，而这种循环单元又可以通过喷口流体温度和地球化学成分的变化在海底探测到。 与2018年前几次潜水相比，海底形态和喷口位置也可能发生变化。 相反，零假设是，自2006年以来研究的排气口位置继续逐渐冷却（每个排气口应比2018年最后一次研究时冷却6±2°C），其组成将相应变化。 重要的是，证明这个零假设仍然具有科学价值。 该奖项将延长全球板内热液区最长的时间序列，并继续收集事件前的数据，以预测未来在Lōzuihi发生的喷出火山活动。该奖项反映了NSF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。

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.