Electrical structure beneath Schirmacher Oasis, East Antarctica: a magnetotelluric study

Abstract

Maitri Station (70.76°S; 11.73°E) is located in Schirmacher Oasis, a coastal nunatak in north-central Dronning Maud Land covering an area of 35 km2. Here, we report results from the first magnetotelluric experiments and delineate the deep electrical conductivity structure under Schirmacher Oasis using the data acquired during the 24th Indian Antarctic Scientific Expedition. The magnetotelluric method has the advantage of shallow to deeper level coverage as the data acquisition covers a wide frequency band of 10−3–103 Hz, permitting different penetration depths depending on the frequency and conductivity of the layer under investigation. The modelling results indicate the presence of a highly resistive (8000–10 000 ohm m) upper crust, which shows a lateral variation in thickness from 20 km (below site 6) in the east to 10 km (between sites 1 and 2) in the west. It is underlain by a less resistive (500–600 ohm m) lower crust. The highly resistive upper crustal structure supports the existing notion that western Dronning Maud Land is a stable, cratonic platform. Results of free-air gravity, seismic, geomagnetic and surface wave dispersion investigations in East Antarctica also indicate a cratonic-type crust. The results of our study allow us to identify a westward thinning of the upper crust with a marked boundary between sites 1 and 2. We also find evidence for the continuity of the Mozambique mobile belt in East Antarctica on the western side of Schirmacher Oasis

Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

“…Thick ice covers nearly all of Antarctica; thus, geophysical methods are required to image sub‐ice geological structures. Magnetotellurics (MT) is a passive electromagnetic method that is an important geophysical technique for investigating sub‐ice structure in Antarctica as it combines good resolution, minimal environmental impact, and favorable logistics [e.g., Beblo and Liebig , ; Wannamaker et al , ; Murthy et al , ].…”

Preliminary Long-Period Magnetotelluric Investigation at the Edge of Ice Sheet in East Antarctica

“…In 2004, they also collected high-quality MT data onto the eastern Antarctica, which proved the feasibility of MT data collection of the whole Antarctic region (Wannamaker et al, 2004). After that, Armadillo et al (2004), Murthy et al (2013), Peacock and Selway (2016) also showed the excellent MT measurement at the eastern Antarctica (Figure 1). Long-period magnetotelluric (LMT) can be used to study the electrical structure of earth crust and mantle (Lizarralde et al, 1995;Mackie et al, 1988;Unsworth et al, 2005).…”

“…However, due to the fact that Antarctica is covered by ice and snow, limited by the bad natural environment and logistics supply difficulties, it is relatively difficult to carry out largescale long-time MT measurement continuously. At present, the most detection depth is generally within 40 kms using MT method (Armadillo et al, 2004;Murthy et al, 2013;Peacock and Selway, 2016;Wannamaker et al, 2004). The geophysical research on the structure of the Antarctic plate crust and lithospheric mantle is still focused on imaging the broadband seismic base station data (An et al, 2015;Heeszel et al, 2016;Ritzwoller et al, 2001), processing and inversion of satellite gravity anomaly data (Haeger et al, 2019;Ji et al, 2018;Scheinert et al, 2016), and joint processing and interpretation based on gravity and seismic data (Baranov et al, 2017;Tenzer et al, 2018).…”

Volcanic passive continental margin beneath Maitri station in central DML, East Antarctica: constraints from crustal shear velocity through receiver function modelling

“…Surface wave studies found craton-like velocities in East Antarctica (Bentley 1991;Ritzwoller et al 2001). A deep electrical conductivity structure under Schirmacher Oasis in central DML showed highly resistive (8000-10 000 ohm m) upper crust followed by lesser resistive (500-600 ohm m) lower crust; and the results were interpreted that the Schirmacher Oasis to be a stable cratonic platform (Murthy et al 2013). Another magnetotelluric study in the Schirmacher Oasis ( Fig.…”