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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 ArchiMer
Lamarque, Gaelle; Bascou, Jerome; Menot, Rene-pierre; Paquette, Jean-louis; Couzinie, Simon; Rolland, Yann; Cottin, Jean-yves.
This study presents the first geochronological results on basement rocks from the Penguin-Bage-Webb (PBW) domain located east of the Neoarchean-Paleoproterozoic Terre Adélie craton, Antarctica. Investigated samples are paragneiss xenoliths hosted within early Paleozoic granitoids, which were emplaced during the Ross orogeny. Zircon UPb dating yielded ages ranging from the Archean to the Cambrian, with a dominant Ediacaran (550–635 Ma) population and maximum depositional ages around 570–575 Ma. U–Th–Pb analyses of monazite suggest that the metamorphic event that formed the gneiss samples occured at ca. 515 Ma, shortly prior to incorporation within the granitic magmas. The studied samples likely represent relics of the pre-Gondawana Pacific margin, which was...
Tipo: Text Palavras-chave: Gondwana margin; Ross orogeny; George V Land; Antarctica-Australia connection; Zircon and monazite U-Pb dating.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00457/56903/58865.pdf
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Lithospheric and sublithospheric deformation under the Borborema Province of northeastern Brazil from receiver function harmonic stripping ArchiMer
Lamarque, Gaelle; Julià, Jordi.
The depth-dependent anisotropic structure of the lithosphere under the Borborema Province in northeast Brazil has been investigated via harmonic stripping of receiver functions developed at 39 stations in the region. This method retrieves the first (k=1) and second (k=2) degree harmonics of a receiver function dataset, which characterize seismic anisotropy beneath a seismic station. Anisotropic fabrics are in turn directly related to the deformation of the lithosphere from past and current tectonic processes. Our results reveal the presence of anisotropy within the crust and the lithospheric mantle throughout the entire province. Most stations in the continental interior report consistent anisotropic orientations in the crust and lithospheric mantle,...
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Ano: 2019 URL: https://archimer.ifremer.fr/doc/00503/61488/65288.pdf
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Modeling of anisotropy in the lithosphere and asthenosphere for real Earth cases: a critical assessment of the impact on SKS measurements ArchiMer
Lamarque, Gaelle; Piana Agostinetti, Nicola.
We investigate effects of realistic Earth's lithospheric structures on measurements of SKS seismic waves birefringence, which could be perturbed by different factors. We present SKS measurements recorded in four different tectonic settings. For each case, a realistic lithospheric structure is assumed and synthetic SKS splitting measurements are compared with the field observations. Our results show that: (a) in simple case, where anisotropy is aligned in both the lithospheric mantle and the asthenosphere, the SKS measurements can be safely interpreted as dominantly related to asthenospheric mantle flow; (b) in case of multi‐layer anisotropy in the lithospheric mantle, SKS measurement can corresponds to a combination of the different fast axis orientations...
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Ano: 2020 URL: https://archimer.ifremer.fr/doc/00630/74181/73777.pdf
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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 ArchiMer
Naumenko-dèzes, M.o.; Rolland, Y.; Lamarque, Gaelle; Duclaux, G.; Gallet, S.; Bascou, J.; Ménot, R.p..
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...
Tipo: Text Palavras-chave: East Antarctica; Ar-40/Ar-39 dating; Shear zones; HT metamorphism; P-T modelling; Mafic magmatism.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00599/71145/69465.pdf
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