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Title: 3230-3200 Ma post-orogenic extension and mid-crustal magmatism along the southeastern margin of the Barberton Greenstone Belt, South Africa.
Authors: Lana, Cristiano de Carvalho
Buick, Ian S.
Stevens, Gary
Rossouw, Riana
Wet, Willem de
Keywords: Dome and keel
Issue Date: 2011
Citation: LANA, C. de C. et al. 3230-3200 Ma post-orogenic extension and mid-crustal magmatism along the southeastern margin of the Barberton Greenstone Belt, South Africa. Journal of Structural Geology, v. 33, n. 5, p. 844-858, maio 2011. Disponível em: <>. Acesso em: 22 out. 2012.
Abstract: The Barberton Granitoid-Greenstone Terrain (SouthAfrica) preserves a complex and protracted evolution involving several events of magmatism and terrain accretion along convergent tectonic boundaries. Recent studies propose that the main period of tectonic accretion and arc-related magmatism is linked to a system of divergent subduction zones above which voluminous TTG magmas were emplaced between ca. 3236 and 3227 Ma. Our structural and LA-ICP-MS U–Pb geochronology study along the southeasternmargin of the BarbertonGreenstoneBelt (BGB) ties the waning stages of this TTG magmatism to a short (ca. <30 Ma) period of mid-crustalextension, between 3228 and 3205 Ma. We document a major NE-trending detachment that juxtaposed upper sequences (Moodies Group clastic sediments) against mid-crustal 3418 ± 10 Ma amphibolite-facies rocks of the base of the greenstonebelt (Onverwacht Group rocks). Several granodiorite bodies - intruded along this detachment - contain well-preserved (syn- and post-magmatic) fabrics that are demonstrably related to extensional shearing and exhumation. Field observations and U–Pb zircon data from these granitoids are consistent with the deformation taking place at 3228 ± 10 Ma – contemporaneous with the voluminous (3236–3227 Ma) TTG magmatism in the northwestern margin of the BGB. The timing of the granodiorite emplacement also constrains a minimum age for the deposition of the Moodies Group clastic sediments, which for much of the southern and southeastern parts of the BGB must have happened before ca. 3228 Ma. 3205 ± 9 Ma subvolcanic dykes intruded into the granodiorite complex indicate that the period of exhumation and cooling of the crystalline rocks along the extensional detachment was relatively short (<30 Ma), between 3228 and 3205 Ma. Our observations combined with previously published structural data from the northwestern and southern margin of the belt suggest that the main mechanism of large-scale infolding of the supracrustal strata was shortly followed by the extension-related magmatism and subsequent, solid-state diapiric movement of the arc-related plutons.
ISSN: 01918141
metadata.dc.rights.license: O periódico Journal of Structural Geology concede permissão para depósito deste artigo no Repositório Institucional da UFOP. Número da licença: 3315440628001.
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