{"title":"A plume of volcanic 3He observed in the Shallow North Pacific","authors":"W.J. Jenkins , T.M. Joyce , G.C. Johnson , D.A. Hansell","doi":"10.1016/j.epsl.2025.119634","DOIUrl":null,"url":null,"abstract":"<div><div>In April 1994, we observed a ∼100 m thick plume of volcanic <sup>3</sup>He at 140 m depth, extending approximately 700 km meridionally, and centered at 18°N along 110°W in the Pacific. It was not present in two subsequent occupations. The plume had a significant dissolved helium excess, with a <sup>3</sup>He/<sup>4</sup>He ratio 7.4 ± 0.6 times atmospheric, consistent with an upper mantle volcanic source. It resulted from a series of eruptions that occurred at 250 m depth on the flank of nearby Socorro Island from January 1993 that continued to the end of 1995. Using plume rise height, we estimate an initial heat flux of 6.7 ± 3.3 GW, with a total output of 0.2 - 4 × 10<sup>17</sup> Joules. Numerical simulations show that the estimated <sup>3</sup>He inventory released is a function of persistence, ocean velocity, and horizontal eddy mixing rates, allowing us to constrain the total release of <sup>3</sup>He to 24 – 28 mol, about 5 – 6 % of the annual global oceanic hydrothermal <sup>3</sup>He flux. The <sup>3</sup>He:heat ratio was 0.06 – 2 fmol J<sup>-1</sup>, about 3 to 100 times larger than the ratio of helium to heat produced by U and Th decay, and much greater than “typical” mid-ocean ridge hydrothermal systems. By entraining deeper, nutrient-rich water, including iron, the buoyant plume from such venting may spur bursts of new biological activity in otherwise low-productivity waters, which may locally enhance export of particulate matter to the deep sea and significantly alter shallow inventories of dissolved organic carbon.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"671 ","pages":"Article 119634"},"PeriodicalIF":4.8000,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Earth and Planetary Science Letters","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0012821X25004327","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
In April 1994, we observed a ∼100 m thick plume of volcanic 3He at 140 m depth, extending approximately 700 km meridionally, and centered at 18°N along 110°W in the Pacific. It was not present in two subsequent occupations. The plume had a significant dissolved helium excess, with a 3He/4He ratio 7.4 ± 0.6 times atmospheric, consistent with an upper mantle volcanic source. It resulted from a series of eruptions that occurred at 250 m depth on the flank of nearby Socorro Island from January 1993 that continued to the end of 1995. Using plume rise height, we estimate an initial heat flux of 6.7 ± 3.3 GW, with a total output of 0.2 - 4 × 1017 Joules. Numerical simulations show that the estimated 3He inventory released is a function of persistence, ocean velocity, and horizontal eddy mixing rates, allowing us to constrain the total release of 3He to 24 – 28 mol, about 5 – 6 % of the annual global oceanic hydrothermal 3He flux. The 3He:heat ratio was 0.06 – 2 fmol J-1, about 3 to 100 times larger than the ratio of helium to heat produced by U and Th decay, and much greater than “typical” mid-ocean ridge hydrothermal systems. By entraining deeper, nutrient-rich water, including iron, the buoyant plume from such venting may spur bursts of new biological activity in otherwise low-productivity waters, which may locally enhance export of particulate matter to the deep sea and significantly alter shallow inventories of dissolved organic carbon.
期刊介绍:
Earth and Planetary Science Letters (EPSL) is a leading journal for researchers across the entire Earth and planetary sciences community. It publishes concise, exciting, high-impact articles ("Letters") of broad interest. Its focus is on physical and chemical processes, the evolution and general properties of the Earth and planets - from their deep interiors to their atmospheres. EPSL also includes a Frontiers section, featuring invited high-profile synthesis articles by leading experts on timely topics to bring cutting-edge research to the wider community.