STRUCTURE OF MID-OCEANIC RIFT ZONE OF INDIAN OCEAN AND ITS PLACE IN WORLD RIFT SYSTEM

We report results obtained from detailed geological-geophysical surveys of representative parts of the rift zone and other associated tectonic zones of the Indian Ocean. Detailed bathymétrie maps and seismic profiles and the analysis of all geophysical data are presented. The petrography, petrochemistry and physical properties were investigated for some specimens of magmatic rocks from the rift zone. The rift zone and the Mid-Oceanic Ridge of the Indian Ocean are zones of active development of the earth's crust under the intensive influence of the upper mantle. The earth's crust in the rift zone is a mosaic of normal crustal blocks and upper mantle material squeezed out upwards. The first were formed by zonal melting processes with the division of pyrolite into peridotites and gabbro-basalts. The second are residual peridotites squeezed out upwards in a crystalline state and subjected to varying degrees of serpentinization. The serpentinization occurs at a depth of 10-15 km and arises because of the degassing of the mantle. From the amount of titania and silica, the degree of differentiation of the mantle under the Indian Ocean is less than under the continents. © 1969.