Teleseismic P-wave tomography beneath the Malani Igneous Province in Rajasthan, Northwestern India
Abstract
The Malani Igneous Province (MIP) is a result of the second largest volcanic episode to affect the Indian Subcontinent and is characterised by acid volcanics. It represents an intraplate anorogenic felsic event covering an area of about 50,000 km2 in northwestern India. The MIP hosts the Barmer and Sanchor rifts in the west, the 850 Ma Erinpura Granites in the east that adjoin the Aravalli mountain belt, and also alkaline rocks of age 68 Ma which pre-date the Deccan volcanism in the center. The present study attempts to provide constraints on the prevalent hypothesis by mapping the three dimensional P-wave velocity perturbations (%) in the crust and upper mantle beneath the MIP using teleseismic P-wave tomography. During the period 2012 - 2017, a network of 15 broadband seismographs were deployed in phases at 29 locations, with an average operational period of two years per station. They cover an area of 300 x 300 km2 encompassing the MIP. The dataset consists of 7954 P-phase arrivals, picked from 933 teleseismic events with magnitudes greater than 5.5 within the epicentral range of 30-90 degree. P-wave residual data is prepared with respect to the ak135 theoretical Earth model and inverted using a weighted damped least square method. A multilayer model is obtained that is completely resolved up to a depth of 200 km. Large crustal velocity perturbations of up to -2% are observed over the Barmer and Sanchore rift zones in the western region. This observed low velocity zone extending down to 200 km may possibly reflect the influence of a thermal anomaly beneath the rift systems of northwestern India. This can be attributed to the reworking of the lithosphere during the Deccan episode or a possible compositional imprint of the Proterozoic Malani volcanism.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMS061.0019D
- Keywords:
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- 7299 General or miscellaneous;
- SEISMOLOGY