A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. August 2014. / The Central African Copperbelt is located in the Lufilian Arc which straddles the border between
Zambia and the Democratic Republic of Congo (DRC). Mineralisation of the cupriferous Arc is found
in basal Neoproterozoic Katangan Supergroup sedimentary rocks, which in DRC are termed the
Mines Series Subgroup. The Mines Series is divided into the dolomitic and carbonaceous GRAT,
DStrat RSF, RSC, SD and CMN units. The composition of the units is homogeneous across the
Lubumbashi district and potentially across the Katangan basin. This study focussed on the Kinsevere
and Ruashi deposits in the Lubumbashi district, which are approximately 50 km apart.
The study confirmed that relative eustatic sea level changes resulted in the non-deposition of the
RSF and RSC stratigraphic units at Kinsevere. Sedimentation was followed by early pervasive potassic
alteration and silicification at the diagenetic stage whilst a magnesian dolomitisation event resulted
in alteration of potassic feldspars and recrystallisation of carbonates. Albitisation was veincontrolled
and late-stage scapolitisation altered evaporitic nodules. Finally, haematisation by late
iron-rich fluids circulating through the Roan Group strata resulted in oxidation of sulphides.
The structural analysis of Kinsevere Central pit indicates E-W and N-S shortening whereas the Ruashi
pit 1 deposit underwent NE-SW and N-S shortening. Initial shortening, associated with Kolwezian
deformation (D1), resulted in the formation of NE-thrust folds and a primary set of joints. The
Kolwezian deformation event (D2), reoriented the shortening direction from E-W to N-S, creating
interference folds and possibly a second set of joints. The final phase in the structural evolution of
the Kinsevere and Ruashi deposits was late-stage brittle deformation (faulting).
Mineralisation was a multi-stage process. Disseminated chalcopyrite and carrollite were deposited
from formation waters during diagenesis in a stable basin environment. Chalcopyrite, carrollite,
chalcocite and bornite are predominantly located at the base of the DStrat, whereas chalcopyrite
and pyrite dominate the stratigraphically higher portions of the deposits. Hypogene vein
mineralisation began at the syn- to late- orogenic stage with carrollite and chalcopyrite in beddingparallel
veins. Possible changes in the compression direction created the perpendicularly oriented
veins that host chalcopyrite, carrollite, bornite, covellite, digenite and chalcocite. Finally a late stage
of chalcopyrite and pyrite deposition occurred in and around the evaporites, indicating a strong
correlation between mineralisation, evaporites and scapolitisation.
iii
Near-surface supergene alteration of hypogene sulphide ores, resulted in Cu-Co carbonates and
oxides, such as malachite, azurite, cobaltiferous malachite, chrysocolla, kolwezite and
sphaerocobaltite being deposited in vugs and pore spaces above the meteoric water line. Faulted
and brecciated zones tend to have deeper supergene alteration. Between the sulphide facies at
depth and the supergene oxide facies at surface is a transition zone which marks the depth to which
oxidation has penetrated.
Sulphur isotope analysis from the Kinsevere and Ruashi deposits suggests a sulphur contribution
from a continental Red-Bed sedimentary source and from an evaporitic source.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/16918 |
| Date | 06 February 2015 |
| Creators | Johnson, Russell Douglas |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
Page generated in 0.0021 seconds