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Author Lamarque, G. Bascou, J. Ménot, R. P. Paquette, J. L. Rolland, Y. Cottin, J. Y.
Title George V Land paragneisses xenoliths dating. New insights for the Antarctica-Australia connection and geodynamic reconstructions. Type Conference - International - Poster
Year 2012 Publication Abbreviated Journal
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Abstract George V Land is constituted of terrains that are considered as the southern extension of Australia in Antarctica. This region plays a key role to better understand the assembly, evolution and separation of the Gondwana and Rodinia supercontinents. In the studied area two distinct continental domains in ages, nature, structures and crustal thicknesses are juxtaposed: the 1.7-2.4 Ga Terre Adélie Craton to the west and a younger domain, comprised of 500 Ma old intrusive complex to the east. The latter is mainly composed of granitoids and is associated with the Ross Orogeny. From field evidences, these two domains are likely separated by a major dextral strike-slip structure: the Mertz shear zone (MSZ, 145E). The MSZ was activated at 1.7 and 1.5 Ga respectively in amphibolite and greenschists facies conditions.
The tectonic evolution of the eastern region between 1.5 Ga (last activation of the MSZ) and 500 Ma (age of the domain bordering the craton) is a key question to geodynamic reconstructions. For this purpose we studied samples of paragneisses xenoliths hosted by the Palaeozoic granitoids, as they represent relics from the underlying basement of this domain. Xenoliths are few-centimeters to several decimeters in size and include different types of paragneisses that may coexist. U-Pb analyses were carried out on 130 zircons from three different xenoliths.
Extracted detritic zircons have similar ages from a sample to another showing a common origin of the sedimentary protolith. A large variety of ages were found from 580 Ma to 3.4 Ga and the best-represented age is about 580 Ga that may correspond to a metamorphic stage predating the intrusive event. Another interesting result is that almost no 1.6 to 2.4 Ga zircons were found, suggesting that sedimentary protolithes cannot be derived from erosion of the neighbouring Terre Adélie Craton. This result argues for a tectonic collage between the two domains. By comparing our results with previous similar studies in South Australia and West Antarctica, we propose a new scenario for the geodynamic evolution of the region before the opening of the Southern Ocean.
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Call Number Serial 5716
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Author Lamarque, G. Bascou, J. Maurice, C. Cottin, J. Y. Ménot, R. P.
Title Microstructural study of the Mertz shear zone, East Antarctica. Implications for deformation processes and seismic anisotropy Type Conference - International - Poster
Year 2015 Publication Abbreviated Journal
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Abstract The Mertz Shear Zone (MSZ; 146E 67S; East Antarctica) is one major lithospheric-scale structure which outcrops on the eastern edge of the Terre Adélie Craton (Ménot et al., 2007) and that could connected with shear zones of South Australia (e.g., Kalinjala or Coorong shear zone (Kleinschmidt and Talarico, 2000; Gibson et al., 2013)) before the Cretaceous opening of the Southern Ocean. Geochronological and metamorphic studies indicated an MSZ activity at 1.7 and 1.5 Ga respectively in amphibolite and greenschists facies conditions. The deformation affects both the intermediate and lower crust levels, without associated voluminous magma injection. Granulite crop out in the area of the MSZ. They were dated at 2.4 Ga (Ménot et al., 2005) and could represent some preserved Neoarchean tectonites. These rocks show various degrees of deformation including penetrative structures that may display comparable features with that observed in amphibolite and greenschists facies rocks, i.e. NS-striking and steeply dipping foliation with weekly plunging lineation. In the field, cinematic indicators for the MSZ argue for a dominant dextral shear sense. We proceed to optical analysis and crystallographic preferred orientation (CPO) measurements using EBSD technique in order to better constrain the deformation processes.
Our results highlight (1) a microstructural gradient from highly deformed rocks (mylonites), forming plurimetric large shear bands and showing evidences of plastic deformation, to slightly deformed rocks in preserved cores with no evidences of plastic deformation or with a clear strong static recrystallization; (2) CPO of minerals related with variations on deformation conditions. Feldspar and quartz CPO argue for plastic deformation at high temperature in the most deformed domains and for the absence of deformation or an important stage of static recrystallization in preserved cores; (3) uncommon CPO in orthopyroxene which are characterized by [010]-axes perpendicular to the foliation and [001]-axes parallel to the lineation. These CPO seem to be related to static recrystallization processes.
Seismic properties of amphibolite and granulite rocks from the MSZ were calculated in order to evaluate the impact of deformation observed in amphibolite and granulite tectonites to seismic anisotropy. Computations were performed from measured CPO, single crystal elastic stiffness matrix, modal composition and density of characteristic samples. P- and S-waves anisotropies of the cratonic crust affected by the MSZ are small and even tend to be isotropic in the case of S-waves propagating vertically in the crust. These results permit us to better discuss seismic studies and in particular SKS analysis which were recently carried out in this area (Lamarque et al., 2015).
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Call Number Serial 6229
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Author Lamarque, G., Bascou, J., Ménot, R.P., Paquette, J.L., Rolland, Y., Cottin, J.Y.
Title George V Land paragneisses xenoliths dating. New insights for the Antarctica-Australia connection and geodynamic reconstructions Type Poster
Year 2015 Publication Egu, vienne, austria Abbreviated Journal
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Call Number Serial 6744
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Author Sue, C., Bascou, J.
Title Analyse quantitative de la déformation cassante en terre Terre Adélie: résultats préliminaires Type Conference - National - Communication
Year 2016 Publication 12èmes journées scientifiques du CNFRA, Lyon, France, 25-27 mai 2016 Abbreviated Journal
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Corporate Author Thesis Bachelor's thesis
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Call Number Serial 6745
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Author Lamarque, G., Barruol, G., Fontaine, F., Bascou, J., Cottin, J.Y., Ménot, R.P.
Title Étude sismologique des structures crustales et lithosphériques du craton de Terre Adélie, Antarctique de l’Est Type Conference - National - Communication
Year 2016 Publication 12èmes journées scientifiques du CNFRA, Lyon, France, 25-27 mai 2016 Abbreviated Journal
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Corporate Author Thesis Bachelor's thesis
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Call Number Serial 6746
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Author Lamarque, G., Bascou, J., Maurice, C., Cottin, J.Y., Ménot, R.P.
Title Deformation processes at the Archean-Proteozoic transition. Microstructural study of the Mertz shear zone, East Antarctica Type Non peer-reviewed symposium
Year 2016 Publication Société française d'exobiologie, atelier thématique origine et evolution de la terre primitive, saint etienne, france Abbreviated Journal
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Call Number Serial 6747
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Author Gaëlle Lamarque, Jérôme Bascou, Claire Maurice, Jean-Yves Cottin, Nicolas Riel, René-Pierre Ménot
Title Microstructures, deformation mechanisms and seismic properties of a Palaeoproterozoic shear zone: The Mertz shear zone, East-Antarctica Type Journal
Year 2016 Publication Tectonophysics Abbreviated Journal
Volume 680 Issue Pages 174-191
Keywords Crustal deformation Crystallographic preferred orientation (CPO) East Antarctica Microstructures Shear zone Strain localization
Abstract The Mertz shear zone (MSZ) is a lithospheric scale structure that recorded mid-crustal deformation during the 1.7Ga orogeny. We performed a microstructural and crystallographic preferred orientation (CPO) study of samples from both mylonites and tectonic boudins that constitute relics of the Terre Adélie Craton (TAC). The deformation is highly accommodated in the MSZ by anastomosed shear bands, which become more scattered elsewhere in the TAC. Most of the MSZ amphibolite-facies mylonites display similar CPO, thermal conditions, intensity of deformation and dominant shear strain. Preserved granulite-facies boudins show both coaxial and non-coaxial strains related to the previous 2.45Ga event. This former deformation is more penetrative and less localized and shows a deformation gradient, later affected by a major phase of recrystallization during retrogression at 2.42Ga. Both MSZ samples and granulite-facies tectonic boudins present microstructures that reflect a variety of deformation mechanisms associated with the rock creep that induce contrasted CPO of minerals (quartz, feldspar, biotite, amphibole and orthopyroxene). In particular, we highlight the development of an “uncommon” CPO in orthopyroxene from weakly deformed samples characterized by (010)-planes oriented parallel to the foliation plane, [001]-axes parallel to the stretching lineation and clustering of [100]-axes near the Y structural direction. Lastly, we computed the seismic properties of the amphibolite and granulite facies rocks in the MSZ area in order to evaluate the contribution of the deformed intermediate and lower continental crust to the seismic anisotropy recorded above the MSZ. Our results reveal that (i) the low content of amphibole and biotite in the rock formations of the TAC, and (ii) the interactions between the CPO of the different mineralogical phases, generate a seismically isotropic crust. Thus, the seismic anisotropy recorded by the seismic stations of the TAC, including the MSZ, must be due to mantle rather than crustal structures.
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ISSN 0040-1951 ISBN 0040-1951 Medium
Area Expedition Conference
Notes Approved yes
Call Number Serial 6748
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Author Mourier, T.
Title Structure magnétique du crtaon de Terre Adélie (Antarctique Est) Type Master 2
Year 2017 Publication Abbreviated Journal
Volume Issue Pages 53p
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Call Number Serial 6749
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Author Gaston Godard, Julien Reynes, Jérôme Bascou, René-Pierre Ménot, Rosaria Palmeri
Title First rocks sampled in Antarctica (1840): Insights into the landing area and the Terre Adélie craton Type Journal
Year 2017 Publication Comptes Rendus Geoscience Abbreviated Journal
Volume 349 Issue 1 Pages 12-21
Keywords “Terre Adélie” craton Antarctica High- metamorphism Icecap shrinking Little Ice age Migmatite Prehnite-pumpellyite
Abstract In January 1840, Dumont d’Urville's expedition landed along the coast of “Terre Adélie” and took three rock specimens, the first ever sampled on the Antarctic continent. The petrological and geochemical study of these samples, stored at the “Muséum national d’histoire naturelle”, in Paris, characterizes them as migmatitic cordierite+microcline-bearing paragneiss and mesocratic quartz+biotite-bearing amphibolite. The paragneiss reached 670°C at 3.2 kbar, suggesting an abnormal high-T gradient of ca. 60°C/km during the regional metamorphism that affected the “Terre Adélie” craton 1.7Ga ago. The studied samples are identical to the rocks observed at the “Rocher du Débarquement”, confirming that this was the actual landing place. On the other hand, quartz diorite and volcanic rocks reportedly sampled in Adélie Land during the same expedition and stored at Le Mans and Toulouse Museums do not originate from Antarctica. The examination of Dumont d’Urville's map suggests an icecap shrinking by 9 km in the landing area since 1840.
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ISSN 1631-0713 ISBN 1631-0713 Medium
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Call Number Serial 6750
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Author M. O. Naumenko-Dèzes, Y. Rolland, G. Lamarque, G. Duclaux, S. Gallet, J. Bascou, R. P. Ménot
Title Petrochronology of the Terre Adélie Craton (East Antarctica) evidences a long-lasting Proterozoic (1.7–1.5 Ga) tectono-metamorphic evolution — Insights for the connections with the Gawler Craton and Laurentia Type Journal
Year 2020 Publication Gondwana Research Abbreviated Journal
Volume 81 Issue Pages 21-57
Keywords Ar/Ar dating East Antarctica HT metamorphism Mafic magmatism P-T modelling Shear zones
Abstract The Terre Adélie Craton displays superimposed strain fields related to the Neoarchean (2.6–2.4 Ga, M1) and Paleo-Mesoproterozoic (1.7–1.5 Ga, M2) metamorphic events. M1 is a regional granulite facies event, constrained by P-T modelling at ~0.8–1.0 GPa – 800–850 °C, followed by a decompressional retrogression in the upper amphibolite facies at ~0.6 GPa – 750 °C. M2 Stage 1 P-T peak is constrained at 0.6–0.7 GPa – 670–700 °C, followed by a steep P-T path down to 0.3 GPa – 550 °C. Retrogression after M2 PT peak occurred in a context of dextral shearing along the Mertz Shear Zone along with thrust motions within the eastern Terre Adélie Craton. In this paper, we present a series of 63 new 40Ar/39Ar ages of biotite and amphibole pairs in mafic rocks from a complete traverse of the Terre Adélie Craton. 40Ar/39Ar dating constrains M2 amphibolite facies metamorphism at a regional scale between 1700 and 1650 Ma, during stage 1 peak metamorphism. During retrogression, lower amphibolite facies recrystallization mainly occurred along vertical shear zones and mafic dykes between 1650 and 1600 Ma (Stage 2), followed by amphibolite to greenschist facies metamorphism until after 1500 Ma (Stage 3). At the scale of the Mawson continent, this event is related to the growth of an active margin above an oblique subduction zone. The supra-subduction model best explains opening of Dumont D'Urville and Hunter basins at 1.71 Ga followed by their rapid closure and metamorphism at 1.70 Ga. In this context, episodic shear zone reactivation and magmatic dyke emplacement led to a partial reequilibration of the 40Ar/39Ar system until <1500 Ma. This latter phase of mafic magmatism largely coincides with a hot spot event at the scale of the Gawler Craton and western Laurentia paleocontinent.
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ISSN 1342-937X ISBN Medium
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Notes Approved yes
Call Number Serial 7643
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