Titre du document / Document title

Géologie et genèse du gisement stratoïde cuprifère de Kinsenda (SE du Shaba, Zaïre) = Geology and genesis of the stratabound Kinsenda copper ore deposit (SE Shaba, Zaïre)

Auteur(s) / Author(s)

NGOYI K. ⁽¹⁾ ; DEJONGHE L. ^{(1 2)} ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Université libre de Bruxelles, 50 avenue F.D. Roosevelt, CP 160/02, 1050 Bruxelles, BELGIQUE
⁽²⁾ Service géologique de Belgique, 13 rue Jenner, 1000 Bruxelles, BELGIQUE

Résumé / Abstract

The cupriferous stratabound deposit at Kinsenda, situated the SE region of Shaba, Zaïre, is hosted in siliciclastic formations of the Lower Roan (Katangian of Neoproterozoic age), unconformably overlying the granitic Luina Dome. The source of the metals and the sulfur, as well as the trapping mechanisms, are constrained. A significant amount of metals has been derived through leaching of the basement, composed of igneous and metamorphic rocks. The metals were transported by underground gravity-driven waters, aided by the permeability of the fissured basement. They were introduced into the Katangan sedimentary basin through synsedimentary faults at the border of the Luina High during diagenesis of the Lower Roan siliciclastic sediments. A secondary source was provided by basinal brines produced during compaction of the sedimentary pile. These brines were capable of leaching the metal content of the sediments. The brines may have been modified by contact with evaporites at some stage in their evolution. Trapping of the metals occurred in two stages. During Roan sedimentation, small lagoons developed, which evolved toward restricted environments where bacterial activity was very important (forming a source of S). Such environments are favourable for the diagenetic precipitation of base-metals. During early diagenesis, the in-situ alteration of detrital ilmenite in the Kinsenda area led to an increase in soluble Fe, such that the first sulphide precipitated was pyrite. In a later diagenetic phase, the introduction of Cu-rich brines along active sedimentary faults led to substitution of Fe in pyrite by Cu, under reducing pH and Eh conditions. The Luina Dome is composed predominantly of a porphyritic granite (1882 ± 20 My; U-Pb zircon) which has been affected by the Lufilian orogeny the most intense events of which culminate around 600 My. During this orogeny, fluid circulation was strong enough to induce migration of elements, episodic Pb loss in zircon, and perturbate the Rb-Sr system in the basement and its Katangan cover. The copperbelt granites behaved as an open geochemical system, which led to hydrothermal alteration of the huge mineralisations in the area.

Revue / Journal Title

Bulletin de la Société belge de géologie   ISSN 0379-1807   CODEN BSBGDT 

Source / Source

1995, vol. 104, n^o3-4, pp. 245-281 [36 page(s) (article)] (3 p.1/2)

Langue / Language

Français
Revue : Multilingue

Editeur / Publisher

Société belge de géologie, Bruxelles, BELGIQUE  (1974-1998) (Revue)

Mots-clés anglais / English Keywords

Shaba Zaire ; copper ; igneous rocks ; metamorphic rocks ; metals ; basement ; faults ; diagenesis ; compaction ; leaching ; evaporites ; stratabound deposits ; siliciclastics ; metallogeny ; Zaire ; Central Africa ; Africa ; chemically precipitated rocks ; sedimentary rocks ;

Mots-clés français / French Keywords

Shaba ; Cuivre ; Roche ignée ; Roche métamorphique ; Elément métallique ; Socle ; Faille ; Diagenèse ; Compactage ; Lessivage ; Evaporite ; Gîte stratoïde ; Roche silicoclastique ; Métallogénie ; Zaïre ; Afrique Centrale ; Afrique ; Roche chimique ; Roche sédimentaire ;

Mots-clés espagnols / Spanish Keywords

Shaba ; Cobre ; Roca ignea ; Roca metamórfica ; Elemento metálico ; Basamento ; Quebrado ; Diagénesis ; Compactación ; Lavado con lejía ; Evaporito ; Metalogenia ; Zaire ; Africa ; Roca química ; Roca sedimentaria ;

Localisation / Location

INIST-CNRS, Cote INIST : 3696, 35400006950969.0020