10.1007/s11479-008-1006-z

Abstract

The brief characteristics of the large intraplate rises of the Indian and Atlantic oceans—the Ninetyeast, Mascarene, Maldives, and Walvis ridges and the Kerguelen Plateau—are discussed. The formation of these, as well as many other intraplate ridges, plateaus, and islands, is usually thought to be a result of the function of long-lived stationary deep-sourced mantle plumes. Despite the wide popularity of this conjecture, many new geological, geophysical, and geochemical data appear to be inconsistent with its basic principles. The rises discussed in this paper are characterized by some common features in combination with peculiarities in magmatism, which are explained in terms of the hot-spot hypothesis by different-scale interaction between the plume material and the depleted upper mantle source. Such an approach provides no convincing evidence that explains the block structure of rises, compositional variations in basalts of their basements, etc. The formation of large fault zones in the consolidated oceanic crust, which, having reached a certain depth, provoke melting and ascent of the upper mantle material, is regarded as an alternative mechanism responsible for the formation of such structural elements. Deep-sourced and/or asthenospheric fluid flows may substantially affect the melting. A compositional difference in basalts from separate segments of rises is probably due to vertical and lateral heterogeneity of the upper mantle.