Abstract:

rom October,1986 to May,1987,the third Antarctic Expedition and First Global Scientific Investigation were successfully carried out by Chinese scientists,during which 52 780km continuous gravity profiles of the three oceans-the Pacific,Atlantic and Indian Ocean were obtained.Based on the data obtained during this investigation,the depths of Moho discontinuity in some typical tectonic were inverted by the method of sinx/x.The characteristics of the gravity anomalies of two different types of continental margins,MidOcean Ridges,aseismic rigde,and abyssal basins in the Idian Ocean were analyzed and the geological interpretation for them were presented in this paper.The results showed theat the Atlantic passive continental margin off eastsouthern African coast is characterized by expansion sinking,and monotonous gravity anomalies with positive and negative unsymmetry.All these suggest an equilibrium state here.However,the pacific active continental margin in the northeastern margin of the Indian Ocean consists of complex arcvolcano system.Here the gravity anomalies is very complex,implying that the region is in an unequilibrium state.ChargosLaccadive Ridge is a typical aseismic ridge,not being a part of the MidIndian Ocean Ridge.The fact that most of the abyssal basins have a typical oceanic gravity combination declares the extensive existence of primary oceanic crusts in the Indian Ocean.