New insights on structure and tectonics over the Laxmi Ridge using EIGEN6C4 modelled gravity data

摘要

A comparative analysis has been attempted for the study of structural and tectonic trends over and around (14 degrees-19 degrees N latitudes and 64 degrees-70 degrees E longitudes) the Laxmi ridge. Initially, three different edge enhancement techniques comprising total horizontal derivative (THD), analytical signal (AS) and Theta map have been tested over synthetic prismatic models with varying depths. It is observed that Theta map technique is relatively suitable for delineation of the edges for the sources at different depths. The free-air gravity (FAG) of the Laxmi ridge and surroundings have been generated using EIGEN6C4 high resolution combined earth gravity modelled data. Upward continued gravity anomaly at 20 Km, 40 km, 60 km, 90 km and 150 km heights have been estimated and these are further enhanced using Theta map technique. The enhanced upward continued maps at different height reveal that the sources of the Laxmi ridge low anomaly is constituted by crust, low density upper mantle materials and recent sediments. Present study reveals that the EIGEN6C4 modelled data could be used effectively to identify various structural features of different wavelength. The study reveals that the major lineaments trends are found along N-S, NE-SW and NW-SE directions followed by E-W, ENE-WSW and NNW-SSE directions including different regional and shallow lineaments trends. The delineated lineaments and their orientations are the results of multiple phases of rifting and breakup of India, Madagascar and Seychelles, since its initial stage.