Fault linkage on southeastern Bjørnøya: Implications for structural interpretations surrounding fertile ore-forming fault systems offshore

Abstract

Exploration for mineral resources offshore requires a detailed understanding and assessment of similar onshore mineral systems. The island of Bjørnøya in the Barents Sea presents a unique opportunity to investigate structurally controlled sulfide-bearing (Pb + Zn + Cu + Au) mineral systems in a tectonic and lithological setting relevant for the surrounding subsea domain. We applied geophysical methods including the interpretation of magnetic and gravity data, field mapping, photogrammetry, and stress-tensor analyses to describe the structural setting and estimate the relative timing of structural and ore-forming events. We show that fault linkage between N–S-striking normal faults and NW–SE-striking oblique-slip transtensional faults provided fluid pathways for mineralising fluids in the mid- to late Paleozoic, probably during the Carboniferous, leading to widespread structurally controlled vein mineralisation of sphalerite and galena on southeastern Bjørnøya. Migration of the ore-forming fluids on Bjørnøya depended on movement along active faults causing seismic pumping, while the ore precipitated following the reduction of sulfate to sulfide by hydrocarbons or hydrogen gas. The characteristic structural setting of mineralisations and ore deposits on Bjørnøya may act as an analog model in the search for primary targets of fluid pathways with potential for mineral resources offshore.