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Crustal and Mantle Structure Beneath the Terre Adélie Craton, East Antarctica: Insights from Receiver Function and Seismic Anis

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Crustal and Mantle Structure Beneath the Terre Adélie Craton, East Antarctica: Insights from Receiver Function and Seismic Anis Crustal and mantle structure beneath the Terre Adélie Craton, East Antarctica: insights from receiver function and seismic anisotropy measurements Gaëlle Lamarque, Guilhem Barruol, Fabrice R. Fontaine, Jerôme Bascou, René-Pierre Ménot To cite this version: Gaëlle Lamarque, Guilhem Barruol, Fabrice R. Fontaine, Jerôme Bascou, René-Pierre Ménot. Crustal and mantle structure beneath the Terre Adélie Craton, East Antarctica: insights from receiver function and seismic anisotropy measurements. Geophysical Journal International, Oxford University Press (OUP), 2015, 10.1093/gji/ggu430. hal-01236105 HAL Id: hal-01236105 https://hal.univ-reunion.fr/hal-01236105 Submitted on 1 Dec 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Geophysical Journal International Geophys. J. Int. (2015) 200, 809–823 doi: 10.1093/gji/ggu430 GJI Seismology Crustal and mantle structure beneath the Terre Adelie´ Craton, East Antarctica: insights from receiver function and seismic anisotropy measurements Gaelle¨ Lamarque,1 Guilhem Barruol,2 Fabrice R. Fontaine,2 Jer´ omeˆ Bascou1 and Rene-Pierre´ Menot´ 1 1UniversitedeLyon,Universit´ eJeanMonnet,UMRCNRSIRD´ 6524,LaboratoireMagmasetVolcans,F-42023 Saint Etienne, France. E-mail: [email protected] 2Laboratoire GeoSciences´ Reunion,´ UniversitedeLaR´ eunion,´ Institut de Physique du Globe de Paris, Sorbonne Paris Cite,´ UMR CNRS 7154,Universite´ Paris Diderot, F-97744 Saint Denis, France Accepted 2014 October 30. Received 2014 September 22; in original form 2014 June 18 Downloaded from SUMMARY The Terre Adelie´ and George V Land (East Antarctica) represent key areas for understand- ing tectonic relationships between terranes forming the Neoarchean-Palaeoproterozoic Terre Adelie´ 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 http://gji.oxfordjournals.org/ 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 litho- spheric 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 by guest on December 15, 2014 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 (!)trendingE–W,thatis,paralleltothecontinentalmargin,and delay times (δt)rangingfrom0.8to1.6s.Theseresultsaresimilartothesplittingparameters 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 qual- ity 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. Key words: Seismic anisotropy; Cratons; Continental tectonics: strike-slip and transform; Crustal structure; Antarctica. of a homogeneous lithosphere, but likely derives from the accre- 1INTRODUCTION tion of numerous cratonic blocks (Mikhal’sky 2008;Boger2011; Constraining the seismic structure of cratons is fundamental for Veevers 2012;Harleyet al. 2013). In contrast, West Antarctica is understanding the formation and the evolution of the continen- characterized by thinner and younger lithosphere. The Terre Adelie´ tal lithosphere. A large part of the Antarctica continent, located Craton (TAC; 66.5–67.5◦Sand135–146◦E) is situated at the edge of east of the Trans-Antarctic Mountains, is cratonic and has been East Antarctica shield (Fig. 1A). It covers the Terre Adelie´ and the characterized from large-scale surface wave tomography by a thick western part of George V Land and extends from Rocher X (longi- lithosphere (Roult & Rouland 1994; Roult et al. 1994;Ritzwoller tude: 136◦40′E) in the west to the Mertz shear zone (MSZ; longitude: et al. 2001;Morelli&Danesi2004;Debayleet al. 2005;Hansen 146◦E) in the east (Peucat et al. 1999;Menot´ et al. 2007;Duclaux et al. 2014). Geological studies show that East Antarctica consists et al. 2008). Recent geophysical data (Aitken et al. 2014)suggest C ⃝ The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society. 809 810 G. Lamarque et al. Downloaded from Figure 1. (A) Location of Terre Adelie´ and George V Land in the Antarctic continent. (B) Links between south Australia and Antarctica. TAC, Terre Adelie´ Craton; GC, Gawler Craton; MSZ, Mertz shear zone; KSZ, Kalinjala shear zone; CSZ, Coorong shear zone. (C) Synthetic geological map of the Terre Adelie´ Craton (after Menot´ et al. 2007). Purple areas are Palaeoproterozoic terranes and correspond to the Dumont D’Urville and Cape Hunter Basins; green and brown areas are Archean terranes, green area referring to the intermediate to upper amphibolitic crust and brown to the granulitic crust. Orange area represents the Palaeozoic crust, mainly composed of granitoids. Darkest colours correspond to outcrops. MSZ denotes the Mertz shear zone and ZSZ denotes the Zel´ ee´ http://gji.oxfordjournals.org/ shear zone. Directions of structures measured at surface are drawn in black. Seismic stations are represented by yellow triangles with a red contour for the DRV permanent station from GEOSCOPE network, and with a black contour for PORMA, PIDGE, CORRE and PINGU temporary stations used in the ArLiTA program. that the TAC may extend westward to the Frost Fault (127◦E). Gran- (2) The upper mantle seismic anisotropy signature (fast po- itoid rocks dating from the Ross orogeny (500 Ma) outcrop to the larisation direction and delay time), that could be associated to east of the MSZ and are generally related to the geological evolu- large-deformation events: that is, to the Neoarchean to Palaeopro- tion of the West Antarctica domain (Di Vincenzo et al. 2007). The terozoic pervasive deformation, related to orogenic cycles, or to MSZ thus appears to be a major boundary between the Neoarchean- the Cretaceous lithospheric deformation linked to the rifting and by guest on December 15, 2014 Palaeoproterozoic TAC and the Early Palaeozoic units, that is, be- opening of the Southern Ocean, or finally, to the present-day as- tween the East Antarctica shield and the West Antarctica orogenic thenospheric flow induced by plate motion relative to the deeper belts. Based on the scarce rocky outcrops in the TAC, which is mantle. mostly covered by the ice cap, the MSZ is inferred to trend roughly (3) The crustal or lithospheric nature of a major shear zone such NS (Talarico & Kleinschmidt 2003) and could be traced to the as the MSZ. Kalinjala or the Coorong shear zone of south Australia (Fig. 1B) (4) The connection of deep structures between Antarctica and before the opening of the Southern Ocean (Kleinschmidt & Ta- Australia which were separated during the opening of the Southern larico 2000;Gibsonet al. 2013). The TAC likely represents the Ocean. southern extension of the Gawler Craton in south Australia (Oliver After a description of the geological framework of this area, &Fanning1997;Peucatet al. 1999;Fanninget al. 2002;DiVin- we present two complementary methods which allow inference of cenzo et al. 2007). getting information on both the crustal structure and the lithospheric The precise geometry of the blocks constituting the TAC, and deformation from respectively the receiver function technique and their relationship to Palaeozoic domains are key questions that are shear wave splitting measurements. The obtained results allow to difficult to answer. Since the Neoarchean and Palaeoproterozoic discuss the following points: (i) the lateral variation of the crustal terranes underwent complex metamorphic and tectonic evolution, structure across the craton boundary, (ii) the connections between the present-day 3-D geometry of blocks boundaries is difficult to the Antarctica–Australia lithospheric structures, (iii) the possible decipher by geological surface analysis alone. The ArLiTA exper- sublithospheric origin of the mantle seismic anisotropy and (iv) the iment (Architecture de la Lithosphere` de Terre Adelie)´ developed
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