To the Question of Magmatism and Origin of the Afanasy Nikitin Rise Due to Discovery of Ancient Zircon by Three Billion Years Age

A zircon with an age of ~2.9 Ga, much older than all existing dates, has been discovered for the first time in basalts of the Afanasy Nikitin Rise. Such an ancient age is typical of continental crust rocks of Western Hindustan or Antarctica. Analyses have revealed the geochemical similarity of magmas of the Conrad and Afanasy Nikitin rises and their difference from Crozet Rise magmas owing to their different formation conditions. Emplacement of the Conrad and Afanasy Nikitin rises occurred ~80–90 Ma ago under the influence of the same Conrad hotspot near the spreading Indian–Antarctic Ridge. This hotspot is a satellite of the giant Kerguelen Plume, active in the Eastern Indian Ocean from 130 Ma ago to the present. The plume formed the Ninetyeast Ridge in the ancient spreading center, and plume magmas leaked along the spreading zone up to the formation area of the Conrad and Afanasy Nikitin rises. During interaction of the Kerguelen Plume with the spreading zone and transform faults, nonspreading blocks of the ancient continental lithosphere of the Gondwana may have been preserved.