Crustal and mantle structure beneath the Terre Adelie Craton, East Antarctica: insights from receiver function and seismic anisotropy measurements

Abstract

The Terre Adélie and George V Land (East Antarctica) represent key areas for understanding tectonic relationships between terranes forming the Neoarchean-Palaeoproterozoic Terre Adélie Craton (TAC) and the neighbouring lithospheric blocks, together with the nature of its boundary. This region that represents the eastern border of the TAC is limited on its eastern side by the Mertz shear zone (MSZ) separating more recent Palaeozoic units from the craton. The MSZ, that recorded dextral strike-slip movement at 1.7 and 1.5 Ga, is likely correlated with the Kalinjala or Coorong shear zone in South Australia, east of the Gawler Craton and may therefore represent a frozen lithospheric-scale structure. In order to investigate the lithospheric structure of the TAC and the MSZ, we deployed from 2009 October to 2011 October four temporary seismic stations, which sampled the various lithospheric units of the TAC and of the neighbouring Palaeozoic block, together with the MSZ. We used receiver function method to deduce Moho depths and seismic anisotropy technique to infer the upper mantle deformation. Results from receiver functions analysis reveal Moho at 40-44 km depth beneath the TAC, at 36 km under the MSZ and at 28 km beneath the eastern Palaeozoic domain. The MSZ therefore delimits two crustal blocks of different thicknesses with a vertical offset of the Moho of 12 km. Seismic anisotropy deduced from SKS splitting at stations on the TAC shows fast polarisation directions () trending E-W, that is, parallel to the continental margin, and delay times (δt) ranging from 0.8 to 1.6 s. These results are similar to the splitting parameters observed at the permanent GEOSCOPE Dumont D'Urville station (DRV: 95 • N, δt 1.1 s) located in the Palaeoproterozoic domain of TAC. On the MSZ, the small number of good quality measurements limits the investigation of the deep signature of the shear zone. However, the station in the Palaeozoic domain shows trending N60 • E, which is significantly different to the trending measurements from stations on the TAC, suggesting that the MSZ may also represent a major frontier between the Neoarchean-Palaeoproterozoic and Palaeozoic terranes.

Crustal and uppermost mantle structure variation beneath La Réunion hotspot track

“…From our experience (e.g. Fontaine et al 2013a;Lamarque et al 2015), this range of ray parameters is still narrow enough that RFs do not require corrections of converted phases (i.e. moveout corrections), given the depth range investigated.…”

“…Instead, we choose to concentrate on stacking similar radial RFs for a limited range of backazimuths and ray parameters in order to estimate the depths of first-order seismic discontinuities present beneath the station (e.g. Fontaine et al 2013a;Lamarque et al 2015). Before each stack, we examine the coherency of individual RFs using the cross-correlation matrix approach from Tkalčić et al (2011): we compute the cross-correlation coefficients for each pair of RFs.…”

3‐D Density, Thermal, and Compositional Model of the Antarctic Lithosphere and Implications for Its Evolution

“…We built this new map using a compilation of all existing Moho depths from receiver function, reflection, and refraction measurements (AN1 Moho, An et al, ; Janik et al, ; Lamarque et al, ; circles in Figure a). Interpolation is carried out within a 150‐km radius around these data points applying a remove‐compute‐restore technique suggested by Stolk et al ().…”

“…(a) Map of the Moho depth with superimposed determinations from refraction, reflection, and receiver function data (circles) (An et al, ; Janik et al, ; Lamarque et al, ). (b) Average density perturbations of the crystalline crust.…”

Ediacaran to lower Cambrian basement in eastern George V Land (Antarctica): Evidence from U Pb dating of gneiss xenoliths and implications for the South Australia- East Antarctica connection

“…In terms of geodynamic reconstruction, it implies that either (i) an old basement similar to the Terre Adélie/Gawler Cratons is present beneath the PBW block but was not exposed at the time of sediment deposition (Ediacaran to Lower Cambrian) so that it was not reworked as detritus feeding the Ediacaran-Lower Cambrian basins, or (ii) the lack of Terre Adélie/Gawler Cratons signature reflects the presence of a different basement in the PBW block. We favor the second hypothesis because seismic investigations (Lamarque et al, 2015), aeromagnetic exploration (Aitken et al, 2014;Ferraccioli et al, 2009;Finn et al, 2006) and gravity data (Jordan et al, 2013) support that the MSZ is a major continental scale tectonic structure that clearly separates two distinct lithospheric domains of probably contrasted ancestries.…”