Structure Formation of the Southeast Indian Ridge at the Early Stages of Development: Physical Modeling

The features of the structure formation of the Earth’s crust at the early stage of formation of the Southeast Indian Ridge were studied. The process of formation was associated with the separation of Australia from Antarctica and the advance of the rift zone westward towards the ancient oceanic lithosphere and, then, towards the large igneous province of Kerguelen, formed by the activity of the plume of the same name. The separation of Australia and Antarctica spanned a long period of continental rifting (~160‒80 Ma), which was followed by ultraslow spreading (~80‒45 Ma), slow spreading (~45‒40 Ma), and, finally, by recent stationary spreading at average rates (after 40 Ma). The advance of the rift zone towards the ancient oceanic lithosphere gave way to the accretion of young oceanic crust on the emerging Southeast Indian Mid-Oceanic Ridge. The early stages of development of the young spreading ridge are reflected in the modern structural plan of the study region. The advance of the rift zone from the continent into the boundaries of the ancient oceanic lithosphere led to the formation of the Naturalist Plateau and the Bruce Bank near the Antarctic margin. The break-up of the ancient oceanic lithosphere and the formation of the young crust on the Southeast Indian Ridge led to the formation of conjugated Diamantina and Labuan suture zones, fixing the position of the initial rifting. The transition from ultraslow spreading at the initial stage of oceanic crust formation to stationary spreading at average rates is clearly recorded in the change in the ruggedness of the accretionary relief. The Southeast Indian Mid-Oceanic Ridge collided as a result of its propagation westward with a large igneous province during the formation of the Kerguelen Plateau and separated the Broken Range from the plateau. The authors carried out physical modeling of the development conditions of rifting and spreading processes, as well as structure formation within the Southeast Indian Ridge.