Neoproterozoic crustal evolution in Southern Chad: Pan-African ocean basin closing, arc accretion and late- to post-orogenic granitic intrusion |
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| Authors: | A Pouclet M Vidal J-C Doumnang J-P Vicat R Tchameni |
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| Institution: | aInstitut des Sciences de la Terre d’Orléans, UMR 6113, Université, B.P. 6759, 45067 Orléans Cedex 2, France;bLaboratoire de Géologie, Faculté des Sciences, Université, B.P. 1027, N’Djamena, Tchad;cDépartement des Sciences de la Terre, Faculté des Sciences, Université, B.P. 454, Ngaoundéré, Cameroun |
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| Abstract: | In the Lake Léré region, southern Chad, Neoproterozoic terrains are distributed in four lithostructural groups that reveal the geotectonic evolution of a part of the Pan-African orogenic domain. The first group includes basaltic volcanic rocks and fine-grained detrital sedimentary rocks of pre-tectonic basins that were emplaced in an extensional regime, close to a volcanic arc. The second and third groups include calc-alkaline gabbroic intrusions emplaced at an upper crustal level and a midcrustal tonalite, respectively, that are interpreted to be the roots of an active margin volcanic arc. These first three groups experienced WNW to ESE compression, and may belong to a fore-arc basic—volcanic arc—back-arc basin system that was accreted eastward to the Palaeoproterozoic Adamaoua-Yadé Block. The fourth group includes post-tectonic granite plutons invading the older groups. This paper documents the accretion processes in the southern margin of the Saharan Metacraton. |
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| Keywords: | Pan-African orogen Volcanic arc Post-orogenic granites Neoproterozoic Chad |
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