Iron oxyhydroxide-rich hydrothermal deposits at the high-temperature Fåvne vent field, Mohns Ridge

Caroline Gini; John Jamieson; Eoghan P. Reeves; Amy Gartman; Thibaut Barreyre; Michael G. Babechuk; Steffen L. Jorgensen; Katleen Robert

doi:10.1029/2024gc011481

USGS · 70255562

Iron oxyhydroxide-rich hydrothermal deposits at the high-temperature Fåvne vent field, Mohns Ridge

Caroline Gini·John Jamieson·Eoghan P. Reeves·Amy Gartman·Thibaut Barreyre·Michael G. Babechuk·Steffen L. Jorgensen·Katleen Robert

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Abstract

The recently discovered Fåvne vent field, located at 3,040 m depth on the slow-spreading Mohns mid-ocean ridge between Greenland and Norway, is a high-temperature (≥250°C) vent field that is characterized by Fe oxyhydroxide-rich and S-poor chimneys and mounds. The vent field is located on both the hanging wall and footwall of a normal fault with a ∼1.5 km throw that forms the western edge of the ∼20 km wide ridge axial valley. Data collected during exploration of the site using a remotely operated vehicle as well as mineralogical and geochemical analyses of rock samples and sediments are used to characterize the geological setting of the vent field and composition of the hydrothermal deposits. The chimney walls are highly porous and lack defined chalcopyrite lined conduits, typical of high-temperature chimneys. Overall, abundant Fe oxyhydroxide precipitation at high-temperature vents at Fåvne reflects an excess of Fe over reduced S in the fluid, leading to precipitation of Fe oxide and oxyhydroxide minerals at high to moderate temperature vents (>100°C), and as microbially mediated and abiotic precipitation of Fe oxyhydroxide minerals at low-temperature diffuse vents (<100°C). The mounds and chimneys exhibit low base metal and reduced S concentrations relative to globally averaged seafloor deposits and suggest subseafloor mixing of hydrothermal fluid with seawater, causing metal sulfide precipitation. Cobalt enrichment at Fåvne may reflect a subsurface influence of an ultramafic substrate on circulating fluids, although ultramafic rocks are absent on the seafloor and no other elements typical of ultramafic deposits are present.

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Geochemistry, Geophysics, Geosystems Article

Source-reported bounding extent: 66.9804124151006° to 74.30569199847616° latitude; -14.945593530960565° to 3.9250034267149374° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Caroline Gini, John Jamieson, Eoghan P. Reeves, Amy Gartman, Thibaut Barreyre, Michael G. Babechuk, Steffen L. Jorgensen, Katleen Robert. 2024-06-21. Iron oxyhydroxide-rich hydrothermal deposits at the high-temperature Fåvne vent field, Mohns Ridge. https://doi.org/10.1029/2024gc011481

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