Ramalho Sofia P.

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Sofia P.

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Volcanically hosted venting with indications of ultramafic influence at Aurora hydrothermal field on Gakkel Ridge

2022-10-31 , German, Christopher R , Reeves, Eoghan P , Türke, Andreas , Diehl, Alexander , Albers, Elmar , Bach, Wolfgang , Purser, Autun , Ramalho, Sofia P , Suman, Stefano , Mertens, Christian , Walter, Maren , Ramirez-Llodra, Eva , Schlindwein, Vera , Bünz, Stefan , Boetius, Antje

The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across-unusually large for a volcanically hosted vent on a slow-spreading ridge and more comparable to tectonically hosted systems that require large time-integrated heat-fluxes to form. The hydrothermal plume emanating from Aurora exhibits much higher dissolved CH/Mn values than typical basalt-hosted hydrothermal systems and, instead, closely resembles those of high-temperature ultramafic-influenced vents at slow-spreading ridges. We hypothesize that deep-penetrating fluid circulation may have sustained the prolonged venting evident at the Aurora hydrothermal field with a hydrothermal convection cell that can access ultramafic lithologies underlying anomalously thin ocean crust at this ultraslow spreading ridge setting. Our findings have implications for ultra-slow ridge cooling, global marine mineral distributions, and the diversity of geologic settings that can host abiotic organic synthesis - pertinent to the search for life beyond Earth.

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Hot vent beaneath an icy ocean: the Aurora vend field, Gakkel Ridge, revealed

2022-11-08 , Ramirez-Llodra, Eva , Argentino, Claudio , Baker, Maria , Boetius, Antje , Costa, Carolina , Dahle, Håkon , Denny, Emily M. , Dessandier, Pierre-Antoine , Eilertsen, Mari H. , Ferre, Benedicte , German, Christopher R. , Hand, Kevin , Hilário, Ana , Hislop, Lawrence , Jamieson, John W. , Kalnitchenko, Dimitri , Mall, Achim , Panieri, Giuliana , Purser, Autun , Ramalho, Sofia P. , Reeves, Eoghan P. , Rolley, Leighton , Pereira, Samuel I. , Ribeiro, Pedro A. , Sert, Muhammed Fatih , Steen, Ida H. , Stetzler, Marie , Stokke, Runar , Victorero, Lissette , Vulcano, Francesca , Vågenes, Stig , Waghorn, Kate Alyse , Buenz, Stefan

Evidence of hydrothermal venting on the ultra-slow spreading Gakkel Ridge in the Central Arctic Ocean has been available since 2001, with first visual evidence of black smokers on the Aurora Vent Field obtained in 2014. But it was not until 2021 that the first ever remotely operated vehicle (ROV) dives to hydrothermal vents under permanent ice cover in the Arctic were conducted, enabling the collection of vent fluids, rocks, microbes, and fauna. In this paper, we present the methods employed for deep-sea ROV operations under drifting ice. We also provide the first description of the Aurora Vent Field, which includes three actively venting black smokers and diffuse flow on the Aurora mound at ~3,888 m depth on the southern part of the Gakkel Ridge (82.5°N). The biological communities are dominated by a new species of cocculinid limpet, two small gastropods, and a melitid amphipod. The ongoing analyses of Aurora Vent Field samples will contribute to positioning the Gakkel Ridge hydrothermal vents in the global biogeographic puzzle of hydrothermal vents.