EVOLUTION OF ICELANDIC RIFT ZONES UNDER CONDITIONS OF PERIODIC PLUME PULSE

The Mid-Atlantic Ridge within Iceland differs significantly from others by its structures. It consists of a few active rift zones with different kinematics and internal structure. At the same time, there are also several inactive rift zones, separated by block uplifts. This structural diversity is caused by the thermal influence of the Icelandic plume, which manifests itself in conditions of asymmetric spreading. Physical modeling was used to identify the conditions for the development of Icelandic rift zones and the features of their structure in relation to the cyclicity of plume activity. The resulting model reflects the structure and development of Icelandic rift zones over the last 21.5 Myr. Results show that the kinematics and internal structure of rift zones are a consequence of the development of multi-scale overlaps of spreading centers. Between them, block uplifts arise, which in the present-day topography are expressed as elevated peninsulas, mainly in the northern part of the island. The sizes of block uplifts depend on the distance between overlapping spreading axes. As the distance decreases, large uplifts are replaced by a series of small en-echelon blocks. The formation of this structural ensemble is the result of periodic increase in plume activity and its eastward displacement relative to the boundary of the lithospheric plates, which is caused by spreading asymmetry. There are two cycles of plume activity with different durations. The period of 7–8 Myr reflects the complete cycle of formation and development of overlappings, and the period of 2–3 Myr determines the evolution of the rift zone structure within the entire structural ensemble.