Axial And Off-Axial Morphology Of Arctic And Polar Atlantic Spreading Ridges (Analogous Modeling)

Andrey Kohan

The ultra-slow spreading ridges with extension velocities less than 20 mm/year are presented with Reykjanes, Kolbeynsey, Mohns, Knipovich and Gakkel ridges situated in North Atlantic and Arctic, and South West INn (SWIR) and American-Antarctic ridges (AAR) situated in south Atlantic and southern part of INn ocean. All of them develop in specific geodynamical conditions, which result in influence of certain geodynamical factors (kinematics, underlying mantle temperature, crustal structure). We see different patterns of structure-forming factors leading to formation of different relief of rift zones. Analyses of morphostructure and morphometry on a basis of detailed bathymetry, published data and results of experimental modeling let to distinguish morphotectonic types of ultra-slow spreading ridges and key structure forming factors leading to formation of their relief and tectonic patterns. Reykjanes and Kolbeynsey ridges, central part of SWIR form under influence of hotspots. Relief changes from fast-spreading-like to slow-spreading like with increase of distance form hotspots. Knipovich ridge and AAR formed as a results of regional changes of plate kinematic patterns and have significant strike-slip components in their kinematics. Relief is formed by long strike-slip segments with absence of magmatic activity and short magmatic segments. Central part of Gakkel ridge and eastern part of SWIR form in conditions of «cold» spreading and are largely amagmatic. Basalts are almost absent and replaced by serpentinised peridotites. Large portions of the ridge have no volcanic features. Western part of SWIR and Gakkel ridges, presumably, form in conditions of increased mantle temperatures. They have relief same with slow spreading Mid-Atlantic ridge. Thus, relief is formed under different combinations of tectonic, magmatic and metamorphic (serpentinisation) geomorphodynamical processes. Geodynamical conditions of ultraslow spreading are considered also

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013