Eruptive-volcanic-basalt structures in the Truong Sa-Spratly Islands and adjacent areas from interpreting gravity and magnetic data

Tran Tuan Dung*, Nguyen Quang Minh


In the Spratly Islands (Truong Sa Islands) and adjacent areas, volcanic activities are quite strong after the sea-floor spreading in the Cenozoic Era. However, it is difficult to define their ranges and spatial locations. Based on the different characteristic between eruptive volcanic basalt and sedimentary rocks near the surface, it can be said that, the blocks which are higher density and magnetization than those surroundings could be identified as eruptive volcanic basalt. This paper presents the methods of reduction to the magnetic equator in low latitudes to bring out a better correlation between magnetic anomalies and their causing-sources; High-frequency filtering is to separate gravity and magnetic anomalies as well as information about the volcanic basalts in the upper part of the Earth's crust; 3D total gradient is to define the spatial location of high density and magnetic bodies. The potential structures of eruptive volcanic basalt are predictively determined by multi-dimensional correlation analysis between high-frequency gravity and magnetic anomalies with weighted total gradient 3D. The results from the above-mentioned methods have shown that the distribution of the eruptive volcanic basalt mainly concentrates along the Spratly Island’s seafloor-spreading axis, transitional crust, Manila trench and some large fault zones. These results are improved by available  seismic data in the study area.


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Spratly Islands, Reduction to the equator, 3D total gradient, Eruptive volcanic basalt.

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