Lithospheric magnetic anomaly map of Indian subcontinent (LAMI-1) from Swarm satellite data

Abstract

A preliminary lithospheric magnetic anomaly map of the Indian subcontinent (LAMI-1) was generated utilising seven years (April 2014–December 2020) of data recorded by the Swarm satellite constellation. To obtain a high-resolution lithospheric anomaly map, the fields originating from sources other than lithospheric sources are eliminated sequentially. The external field component is minimised by selecting the days of low geomagnetic activity (Kp < 2 and –20 < Dst < 20) within night-time hours. The main and the remaining external field sources are removed using data from CHAOS model. The model of residual data is achieved directly through the damped least square inversion technique by expanding the Legendre polynomial of order n = 6–50. The resulting satellite-derived lithospheric magnetic anomaly mostly reflects intermediate to long wavelength deep geological phenomena, with diverse tectonic provinces exhibiting discrete magnetic fingerprints/impressions with amplitudes ranging from high to low. Various tectonic blocks of the Indian subcontinent show distinct signature in the derived lithospheric anomaly map. The Himalayas and the Deccan Volcanic Province are associated with low magnetic signatures. The Central Indian Tectonic Zone and the Arakan Yoma Fold belt appear to have positive magnetisation. The division of Dhawar Craton into Western and Eastern Dharwar by Chitradurga Boundary shear is clearly evident in the anomaly map. A possible track of the Reunion hotspot is depicted as a north–south oriented high within the Marwar block. The comparison between the vertical (Z) component of LAMI-1 with the vertical component of MAGSAT data and MF7 lithospheric model from Champ satellite data indicates the LAMI-1 model shows far less noise and sharper anomalies with tectonic blocks better resolved compared to the other models.