GEODYNAMICS OF JOINT ZONES OF REYKJANES AND KOLBEINSEY SPREADING RIDGES WITH ICELAND RIFT ZONES

Abstract

Joint zones of Reykjanes and Kolbeinsey spreading ridges with Iceland large igneous province considerably differ in structure from adjacent spreading segments despite of similar kinematics. Tjörnes transform zone is a complicated system. It comprises several volcanic and amagmatic structures. In contrast, Reykjanes rift zone has relatively simple structure and homogeneous type of tectonic and magmatic activity. The causes of those differences and their modern dynamics are not fully explained hitherto. Basing on morphometric analysis of normal fault scarps parameters it was concluded that such significant differences of transform zones are result of spatial and temporal stability of adjacent structures. In turn, the latter is controlled by periodic increase of Iceland plume magmatic activity. Rift structures development within transform zones directly correlates with their position over adjacent spreading segments and their magmatic conditions. Modern development of both transform zones is caused by Iceland rift zones instability and migration impacted by Iceland plume thermal pulses. Consequently, transform zones undergo kinematic changes. For Tjörnes transform zone it is expressed in its structure gradual simplification: the western branch and block structures cease their activity. In Reykjanes rift zone rift axis gradually migrates southwards that probably results in its intensive volcanism.