The Gamburtsev Subglacial Mountains (GSM) in central East Antarctica are  completely buried beneath the East Antarctic Ice Sheet. The GSM are known to be underlain by anomalously thick crust (~50–60 km) and ~200 km thick Precambrian lithosphere, but their crustal-scale geology remains less well- studied. Little is known about the 3D heterogeneity in crustal architecture beneath the GSM, and how this may relate to larger-scale tectonic processes responsible for Gondwana amalgamation.Here, we use airborne gravity and aeromagnetic anomalies to explore the crustal architecture of the GSM in unprecedented detail. The gravity and magnetic images show three distinct geophysical domains, and a dense lower crustal root is modelled beneath the northern and central domains. We propose that the root may reflect magmatic underplating, associated with Pan-African age back-arc basin formation and inversion, followed by the collision of Australo-Antarctica and Indo-Antarctica. The high frequency linear magnetic patterns parallel to the Gamburtsev Suture zone, suggest that the upper crustal architecture is dominated by thrust and strike-slip faults, formed within a large-scale transpressional fault system.We calculated a 2D gravity and magnetic model along a passive seismic profile to investigate the crustal architecture of the GSM, with the aid of depth to magnetic source estimates.   By combining the crustal model with  geological constraints, we propose a new evolutionary model suggesting that the crust of the northern and central GSM domains formed part of a cryptic accretionary orogen, of proposed Pan-African (~650-550 Ma?) age. The inferred accretionary stage was followed by continental collision (~540-520 Ma?) along the Gamburtsev suture, which is linked here to Gondwana amalgamation.
<p>East Antarctica is the least understood continent on Earth due to its vast size, major ice sheet cover and remoteness. Coastal outcrops and glacial erratics have yielded cryptic but nevertheless fascinating clues into up to 3 billion years of East Antarctica&#8217;s geological and tectonic evolution. These geological constraints represent in turn the pillars to address global geodynamic linkages between East Antarctica, Australia, India, South Africa and Laurentia in the growth, assembly and dispersal of Gondwana, Rodinia and Nuna during the complex evolution of Earth's supercontinent cycles. However, due to the lack of drilling, our ability to project, test and augment such supercontinental linkages and several speculative geological interpretations in the interior of the continent beneath the East Antarctic Ice Sheet remains very limited.</p><p>While airborne and satellite gravity data and seismology are providing key new constraints on crustal and lithosphere thickness and help unveil large-scale heterogeneity in the East Antarctic lithosphere, detailed imaging of the architecture of individual crustal domains and their tectonic boundaries relies critically on magnetic anomaly data interpretation.</p><p>Here we exploit ongoing analyses of a recent continental-scale magnetic anomaly compilation (ADMAP 2.0) (Golynsky et al., 2018, GRL) augmented by major new datasets we recently collected, processed and compiled over the Recovery and South Pole frontiers and enhanced satellite magnetic imaging to:</p><p>1) reveal a more complex mosaic of distinct but in several places still cryptic Precambrian crustal provinces that represent the building blocks of interior East Antarctica;</p><p>2) provide new geophysical constraints that can be used to test different hypotheses of East-West Gondwana amalgamation along several candidate suture zones, including in particular the Shackleton suture zone, which provides a unique window on several distinct Precambrian terranes at the inferred leading edge of the composite Mawson Continent, as well as unique occurrences of Pan-African age rocks of ophiolitic affinity and</p><p>3) re-assess potential paths and the significance of the Kuunga suture zone between Greater India and East Antarctica and re-evaluate the tectonic origin of a major magnetic and gravity lineament previously thought to delineate the Indo-Australo-Antarctic suture and finally</p><p>4) propose new surveys in other frontier regions including in particular the under-explored interior of Princess Elizabeth Land and Recovery Subglacial Highlands that are critical in order to test the possible connectivity of the Kuunga, Gamburstev and potentially also Shackleton suture zones.&#160;</p><p>Finally, we showcase examples of how we are combining aeromagnetic and gravity interpretations for East Antarctica with global magnetic and gravity datasets, geochronology, geochemistry, geology, tectonics and paleomagnetic data in an evolving plate kinematic framework (in GPlates) to re-assess supercontinent reconstructions with particular emphasis so far on Nuna and Gondwana.</p>
Abstract Several satellite gravity anomaly models are freely available to calculate the free‐air gravity anomaly in areas where shipborne gravity measurements are scarce. Two models produced by the Technical University of Denmark (DTU17) and the Scripps Institution of Oceanography (SIOv32.1), respectively, were selected to compute the free‐air anomalies over the Cosmonaut Sea, East Antarctica. A statistical comparison analysis was performed to evaluate the resolution of satellite gravity anomaly models by comparing them with the shipborne surveying date. The radially averaged energy spectra of free‐air anomaly from different sources were calculated and compared over two selected regions to further evaluate the reliability of the data derived from satellite gravity anomaly models. The satellite gravity anomaly models have a better resolution in the ocean basin than in the area near the continental shelf. The comparison analysis revealed that the precision of both DTU17 and SIOv32.1 is close to the shipborne gravity data, but on average, SIOv32.1 is a little bit better than DTU17. The spectral analysis showed that the shipborne measurements may provide higher resolution than the satellite gravity anomaly model at wavelengths shorter than 20 km, and the free‐air data derived from SIOv32.1 have better resolution than the one from DTU17. These shipborne datasets will provide contributions for the updates of the Antarctic gravity anomaly and enable new high‐resolution combined Earth gravity models to be derived in Antarctica.
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