| dc.description.abstract | Hydrothermally enriched sediments are linked to hydrothermal systems on the seafloor, and thus, studies utilizing sediment cores represent a narrative method to investigate hydrothermal activity. Plume particles from active vent sites disperse and deposit alongside hemipelagic sediments around hydrothermally active areas. This mixed sedimentation allows for combined geochronology and plume transport reconstruction. Studies focused on hydrothermal sediments along the Arctic Mid-Ocean Ridges (AMOR) are to date limited, and the factors controlling the dispersal of plume particles remain poorly understood. The Mohns Ridge (71°15’ N to 73°35’N), a segment of the AMOR, situated in the Norwegian Greenland Sea, host several active and inactive hydrothermal systems discovered during the last decades. This study focuses on the Fåvne-, Mohn’s Treasure-, and Loki’s Castle Vent Field, all situated along the Mohns Ridge. This study has investigated sediments collected by gravity- and push- cores revealing complex sedimentary stratigraphy. The sediment cores have been studied and analyzed through optical imaging, geochemical analyses (XRF-scanning, SEM-EDS and ICP-MS/OES analyses) and geochronology (14C ages from foraminifera). The aim is to determine the duration of an active hydrothermal system, investigate the mixing of hydrothermal and hemipelagic sediments, and to study out-flow rate and spatial particle dispersal. This study documents that high temperature hydrothermal activity can be traced in sediments through positive Eu anomalies and high Cu and Zn concentrations. The sediment core taken near the Fåvne Vent Field reveals an ancient hydrothermal system yet unknown that was active 9000 years ago. Fåvne Vent Field is believed to be initiated for a little over 5800 years ago. Another sediment core taken at the Gnitahei Deposit, reveals plume signals attributed from the Fåvne Vent Field, which is located 800 m north-east of the sampling site. The assumption is based on correlation of hydrothermal-signature sediment layers with near-identical 14C ages of approximately 5000 years. In the same core, the study uncovered that the Gnitahei Deposit was uplifted and exposed more than 20 000 years ago. Near Mohn’s Treasure, a sheet flow erupted at the flanks of the rift valley approximately 7000 years ago covering the debris material from the sulfide deposit. Long-term high temperature venting at Mohn’s Treasure is revealed by positive Eu anomaly and elevated Cu concentrations (2.1-5.2 wt%, avg. 2.6 wt%). At Loki’s Castle, this study indicates that the hydrothermal activity initiated approximately 11 300 years ago. Overall, this study broadens the understanding of hydrothermally enriched sediments and provides insights into hydrothermal processes and plume dispersal along the Mohns Ridge. | |
