Gravity anomalies and deep structure of the Andaman arc |
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| Authors: | Manoj Mukhopadhyay |
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| Institution: | (1) Department of Geophysics, Indian School of Mines, 826004 Dhanbad, India |
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| Abstract: | The Andaman arc is associated with a major Free-air anomaly pair of mean amplitude 180 mgal. Two-dimensional gravity interpretation suggests significant mass anomalies below the arc that presumably have resulted due to subduction of the Indian plate below the Burma plate. It is inferred that the Andaman trench is of asymmetric V-shape containing about 7 km sediments. An outer bathymetric rise seaward of the trench possibly corresponds to a lithospheric flexure by 500 m. The Cretaceous-Tertiary sediments constituting the Andaman sedimentary arc attain their maximum thickness of about 13 km under the Nicobar. Deep at the subduction zone. At this location a mafic mass is emplaced within the sedimentary section. The underlying oceanic crust apparently experiences phase transition at about 27 km depth in a Benioff zone environment. The Andaman volcanic arc underlies a low density zone that is at least 60 km wide. Along the east margin of the Andaman Sea, cuustal transition presumably occurs below the Mergui Terrace at the Malayan coast. |
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| Keywords: | plate subduction gravity field deep structure sediment distribution mafic mass within sediments low density zone below the volcanic axis and crustal transition |
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