Variations in M factor along the ultra-slow spreading Mohns Ridge

Abstract:

The Mohns Ridge is located between ~71°N and 74°N in the Norwegian-Greenland Sea. We analyzed seafloor morphology and geophysical anomalies of the western Mohns Ridge to reveal the significant changes in magma supply along this ultra-slow spreading ridge (15 ~ 17 mm/yr). We identified normal faults on 17 segments of the Mohns Ridge with multibeam bathymetry data. The M factor, which is magmatic component in total plate separation, was measured according to the bathymetry in all profiles. The ridge segment-averaged MBA was also calculated along the ridge axis. The M factor of the western flank of the Mohns Ridge shows significant variations (0.29 ~ 0.80) and averages in a range of 0.50 ~ 0.63. No systematical trend are observed in faulting and M factor from south to north. On the other hand, the mantle Bouguer anomaly (MBA) along the western Mohns Ridge ranges in -130 ~ -70 mGal. The MBA is more negative at the northern side, indicating greater magma supply and thicker crust. The inconsistent between the M factor and MBA may suggest variable mantle temperature structure and/or ununiform magma distribution. Numerical simulations of melt generation and crustal accretion during seafloor spreading will be conducted to explore the mechanism of variations in M factor and MBA along ultra-slow spreading ridge。