Investigating controls on Fe and V isotope systematics during hydrothermal venting at the evolving Kama'ehuakanaloa Seamount.

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

At hydrothermal vents metal-rich fluids expel into the ocean. Iron in these fluids can help support marine life. Black smokers, where vent fluids can reach 350 °C, are spectacular examples of these vents. Warm (< 60 °C) fluids can also be vented from undersea volcanic features called seamounts. There is little known about these warm hydrothermal systems and how they support life in the oceans. This project will analyze samples from Kama’ehuakanaloa, the seamount that will eventually become the next Hawai’ian island. Seamount hydrothermal vents may also be present on icy moons in the solar system, and thus the results from this project may offer a stepping stone in the search for life beyond Earth. Broader impacts include support for an early-career scientist and research opportunities for an undergraduate student. Low temperature submarine venting from intraplate settings exports iron (Fe) and other trace metals to the global oceans. Controls on this style of vent fluid chemistry, and its impacts on global biogeochemistry are not well constrained. The Kama’ehuakanaloa Seamount (KSM) hosts an Fe-rich low T venting system that has cooled at approximately 0.8 °C/yr since its last major eruptive activity in 1996. Published vent fluid temperature and Fe geochemistry have co-evolved since 2006, possibly driven by hydrothermal reaction temperatures, magmatic carbon dioxide (CO2) concentrations, or subseafloor mixing with unaltered seawater. Objective 1 of this project is to identify what drives coupled chemical and temperature systematics in KSM fluids. This will be addressed with elemental and Fe isotopic measurements, conducted using inductively coupled plasma mass spectrometry (ICP-MS) and multi-collector ICP-MS (MC-ICP-MS), of i) 2018 and 2023 KSM vent fluids, and ii) products of laboratory hydrothermal experiments conducted with a flexible gold cell hydrothermal apparatus. Approximately 10 new natural KSM fluid samples will be analyzed, and two experiments with different starting dissolved CO2 concentrations will be conducted over ~200 days. Each experiment will be subsampled approximately 6 times following periodic increases in temperature. Hydrothermal venting also modifies the geochemical cycling of other elements. Vanadium (V) is scavenged on hydrothermal Fe oxide precipitates in a manner which is well characterized at high T vent sites, but the potential impact of low T venting on the marine V cycle has not been rigorously studied. Objective 2 is to conduct the first V isotopic investigations of hydrothermal Fe oxide deposits (FeOX) at the KSM, to determine i) how V is scavenged by low T FeOX, ii) the impacts of low T venting on the global marine V (isotope) mass balance, and iii) the future potential to trace long-distance transport of KSM hydrothermal particles delivered to sediments. Vanadium isotope ratios in approximately 60 new and archived KSM FeOX samples, and small selection of archived KSM basalts and hydrothermal fluids, will be measured using MC-ICP-MS to pursue this objective. This project is jointly funded by the Marine Geology and Geophysics program and the Chemical Oceanography program in the Division of Ocean Sciences. 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.