Shallow seafloor gas emissions near Heard and McDonald Islands on the Kerguelen Plateau, southern Indian Ocean

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Title: Shallow seafloor gas emissions near Heard and McDonald Islands on the Kerguelen Plateau, southern Indian Ocean
Authors: Spain, Erica A.Johnson, Sean C.Hutton, al.
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Date: Mar-2020
Online since: 2020-08-25T10:17:02Z
Abstract: Bubble emission mechanisms from submerged Large Igneous Provinces (LIPs) remains enigmatic. The Kerguelen Plateau, a LIP in the southern Indian Ocean, has a long‐sustained history of active volcanism and glacial/interglacial cycles of sedimentation, both of which may cause seafloor bubble production. We present the results of hydroacoustic flare observations around the under‐explored volcanically‐active Heard Island and McDonald Islands on the Central Kerguelen Plateau. Flares were observed with a split‐beam echosounder and characterized using multi‐frequency decibel differencing. Deep‐tow camera footage, water properties, water‐column δ3He, sub‐bottom profile, and sediment δ13C and δ34S data were analyzed to consider flare mechanisms. Excess δ3He near McDonald Islands seeps, indicating mantle‐derived input, suggests proximal hydrothermal activity; McDonald Islands flares may thus indicate CO2, methane, and other minor gas bubbles associated with shallow diffuse hydrothermal venting. The Heard Island seep environment, with sub‐bottom acoustic blanking in thick sediment, muted 3He signal, and δ13C and δ34S fractionation factors, suggest Heard seeps may either be methane gas (possibly both shallow biogenic methane and deeper‐sourced thermogenic methane related to geothermal heat from onshore volcanism) or a combination of methane and CO2, such as seen in sediment‐hosted geothermal systems (Procesi et al., 2019). These data provide the first evidence of submarine gas escape on the Central Kerguelen Plateau and expand our understanding of seafloor processes and carbon cycling in the data‐poor southern Indian Ocean. Extensive sedimentation of the Kerguelen Plateau and additional zones of submarine volcanic activity mean additional seeps or vents may lie outside the small survey area proximal to the islands.
Funding Details: Science Foundation Ireland
metadata.dc.description.othersponsorship: Australian Antarctic Science Program
Australian Research Council
Australian Government
Type of material: Journal Article
Publisher: American Geophysical Union
Journal: Earth and Space Science
Volume: 7
Issue: 3
Start page: 1
End page: 19
Copyright (published version): 2019 American Geophysical Union
Keywords: Large Igneous provinceHydroacoustic flaresCold methane seepShallow hydrothermalGeothermalGas bubbles
DOI: 10.1029/2019ea000695
Language: en
Status of Item: Peer reviewed
Appears in Collections:Earth Sciences Research Collection
ICRAG Research Collection

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