Schlindwein
Vera
Schlindwein
Vera
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PreprintExplosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean( 2007-11-26) Sohn, Robert A. ; Willis, Claire ; Humphris, Susan E. ; Shank, Timothy M. ; Singh, Hanumant ; Edmonds, Henrietta N. ; Kunz, Clayton G. ; Hedman, Ulf ; Helmke, Elisabeth ; Jakuba, Michael V. ; Liljebladh, Bengt ; Linder, Julia ; Murphy, Christopher A. ; Nakamura, Ko-ichi ; Sato, Taichi ; Schlindwein, Vera ; Stranne, Christian ; Tausenfreund, Upchurch ; Winsor, Peter ; Jakobsson, Martin ; Soule, Samuel A.Roughly 60% of the Earth’s outer surface is comprised of oceanic crust formed by volcanic processes at mid-ocean ridges (MORs). Although only a small fraction of this vast volcanic terrain has been visually surveyed and/or sampled, the available evidence suggests that explosive eruptions are rare on MORs, particularly at depths below the critical point for steam (3000 m). A pyroclastic deposit has never been observed on the seafloor below 3000 m, presumably because the volatile content of mid-ocean ridge basalts is generally too low to produce the gas fractions required to fragment a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel Ridge in the Arctic Basin at 85°E, to acquire the first-ever photographic images of ‘zero-age’ volcanic terrain on this remote, ice-covered MOR. Our imagery reveals that the axial valley at 4000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele), covering a large area greater than 10 km2. At least 13.5 wt% CO2 is required to fragment magma at these depths, which is ~10x greater than the highest values measured to-date in a MOR basalt. These observations raise important questions regarding the accumulation and discharge of magmatic volatiles at ultra-slow spreading rates on the Gakkel Ridge (6- 14 mm yr-1, full-rate), and demonstrate that large-scale pyroclastic activity is possible along even the deepest portions of the global MOR volcanic system.
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ArticleVolcanically hosted venting with indications of ultramafic influence at Aurora hydrothermal field on Gakkel Ridge(Nature Communications, 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, AntjeThe 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.