Polymetallic nodules offshore NE Greenland: links to Fram Strait opening and local hydrothermal activity

This study presents the first documentation and analysis of polymetallic Fe–Mn seafloor nodules from offshore Northeast Greenland. Samples were collected from three sites by dredging and gravity coring along the slopes of both the outer and transform margin highs. The morphology, petrography, and whole-rock geochemistry of twenty-four nodules were determined. ¹⁰Be/⁹Be and (U–Th)/He dating were undertaken for representative samples to constrain the time of formation. Two nodule groups were identified in all studied sampling sites. Group 1 (n = 19) are light banded, primarily hydrogenetic nodules with notable enrichments in Mn and Fe, as well as several trace elements including rare earth elements (REE), V, Co, and Y. They have geochemical and textural similarities to Fe–Mn deposits from the Arctic Basin. ¹⁰Be/⁹Be age estimates suggest that growth initiated around 13,5 Ma, shortly after the opening of the Fram Strait, which influence deep-water circulation and inflow of nutrient-rich Arctic waters onto the NE Greenland shelf. Group 2 nodules (n = 5) are dense with high Fe (up to 64 wt% Fe₂O₃), low Mn content and little to no enrichment in trace elements and REEs. They are interpreted as hydrothermal in origin, with preliminary (U–Th)/He ages suggesting Quaternary formation under weak, diffuse fluid circulation in near-bottom environments of uncertain source. This study expands our understanding of seafloor mineralization in the Arctic–North Atlantic gateway, revealing that on the NE Greenland shelf this process reflects a long-term interplay between tectonic evolution, ocean circulation, and fluid-driven alteration.