Geologica Belgica

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Mwabanwa Louis KIPATA, Damien DELVAUX, Mwene Ntabwoba SEBAGENZI, Jacques CAILTEUX & Manuel SINTUBIN

Brittle tectonic and stress field evolution in the Pan-African Lufilian arc and its foreland (Katanga, DRC): from orogenic compression to extensional collapse, transpressional inversion and transition to rifting.

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Mots-clés : brittle structural evolution, paleostress tensor, orogenic bending, extension, inversion, rifting

Abstract

Since the first and paroxysmal deformation stages of the Lufilian orogeny at ~ 550 Ma and the late Neogene to Quaternary development of the south-western branch of the East African rift system, the tectonic evolution of the Lufilian arc and Kundelungu foreland in the Katanga region of the Democratic Republic of Congo remains poorly known although it caused important Cu-dominated mineral remobilizations leading to world-class ore deposits. This long period is essentially characterized by brittle tectonic deformations that have been investigated by field studies in open mines spread over the entire arc and foreland. Paleostress tensors were computed for a database of 1889 fault-slip data by interactive stress tensor inversion and data subset separation. They have been assembled and correlated into 8 major brittle events, their relative succession established primarily from field-based criteria and interpreted in function of the regional tectonic context. The first brittle structures observed were formed during the Lufilian compressional climax, after the transition from ductile to brittle deformation (stage 1). They have been re-oriented during the orogenic bending that led to the arcuate shape of the belt (stage 2). Unfolding the stress directions allows to reconstruct a well-defined N-S to NNE-SSW direction of compression, consistent with the stress directions recorded outside the belt. Constrictional deformation occurred in the central part of the arc, probably during orogenic bending. After the bending, the Lufilian arc was affected by a NE-SW transpression of regional significance (stage 3), inducing strike-slip reactivations dominantly sinistral in the Lufilian arc and dextral in the Kundelungu foreland. The next two stages were recorded only in the Lufilian arc. Late-orogenic extension was induced by  stress axis permutation in a more trans-tensional regime (stages 4). Arc-parallel extension (stage 5) marks the final extensional collapse of the Lufilian orogeny. In early Mesozoic, NW-SE transpressional inversion felt regionally (stage 6) was induced by far-field stresses generated at the southern active margin of Gondwana. Since then, this region was affected by rift-related extension, successively in a NE-SW direction (stage 7, Tanganyika trend) and NW-SE direction (stage 8, Moero-Upemba trend).

To cite this article

Mwabanwa Louis KIPATA, Damien DELVAUX, Mwene Ntabwoba SEBAGENZI, Jacques CAILTEUX & Manuel SINTUBIN, «Brittle tectonic and stress field evolution in the Pan-African Lufilian arc and its foreland (Katanga, DRC): from orogenic compression to extensional collapse, transpressional inversion and transition to rifting.», Geologica Belgica [En ligne], number 1-2, volume 16 (2013), 1-17 URL : http://popups.ulg.ac.be/1374-8505/index.php?id=3967.

About: Mwabanwa Louis KIPATA

Geodynamics and Geofluids Research Group, K.U.Leuven, Celestijnenlaan 200E, B-3001, Leuven, Belgium ; Department of Geology, University of Lubumbashi, Route Kasapa, Lubumbashi, DRC ; Royal Museum of Central Africa, Leuvensesteenweg 13, B-3080, Tervuren, Belgium

About: Damien DELVAUX

Royal Museum of Central Africa, Leuvensesteenweg 13, B-3080, Tervuren, Belgium ; School of Geosciences, University of the Witwatersrand, South Africa

About: Mwene Ntabwoba SEBAGENZI

Department of Geology, University of Lubumbashi, Route Kasapa, Lubumbashi, DRC 

About: Jacques CAILTEUX

Department of Research and Development, Forrest Group, 22 Av. Kigoma, Lubumbashi, DRC

About: Manuel SINTUBIN

Geodynamics and Geofluids Research Group, K.U.Leuven, Celestijnenlaan 200E, B-3001, Leuven, Belgium