Structural setting of the neo archean terrains in the Commonwealth Bay area (143°-145°E), Terre Adélie Craton, East Antarctica.
International audience Lithological and structural maps from the East Commonwealth Bay Unit (ECB; Terre Adélie and Georges V land, Antarctica) are presented with a summary of the main structural and metamorphic data obtained in the area. The ECB unit is structured during the Late Archean – Lower Pro...
Published in: | Gondwana Research |
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Main Authors: | , , , , , , |
Other Authors: | , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2005
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Subjects: | |
Online Access: | https://hal.archives-ouvertes.fr/hal-00103170 https://hal.archives-ouvertes.fr/hal-00103170/document https://hal.archives-ouvertes.fr/hal-00103170/file/Menot_et_al._2005.pdf https://doi.org/10.1016/S1342-937X(05)70258-6 |
Summary: | International audience Lithological and structural maps from the East Commonwealth Bay Unit (ECB; Terre Adélie and Georges V land, Antarctica) are presented with a summary of the main structural and metamorphic data obtained in the area. The ECB unit is structured during the Late Archean – Lower Proterozoic (at 2.4-2.5 Ga), with (i) granulite metamorphism at 9 - 6 kbar and 850 ± 50 °C of lower-mid crust and amphibolite metamorphism (P ≤ 5 kbar, T ≤ 750°C) of the upper crustal levels. (ii) The lower crustal granulites are uplifted, and suffered local partial melting and then retrogression into the amphibolite facies at 550 ± 50°C – 5 kbar. Granulites are extruded in the core of a crustal-scale anticlinal fold, granulites being retrogressed only on the rims of the anticline. Crustal-scale folding, along with other structural features results from intense NE-SW shortening, that prevailed during the Late Archean orogenic cycle. Strike-slip and extensive motions are only minor in that process. (iii), Top-to-the-East thrusting and nappe piling has (at least locally) occurred under lower amphibolite to greenschist facies conditions. Finally, it seems that (iv) the Paleoproterozoic 1.7 Ga structural imprint may have only affected the rims of the Archean units. The tectonic context observed in the 1.7 Ga Cape Hunter phyllites features mainly E-W shortening component and vertical extrusion. The Eastern (Mertz) and Western (Port Martin) parts of the Archean block were reactivated by localized dextral shearing. |
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