Regional aeromagnetic and stratigraphic correlations of the Kalahari Copperbelt in Namibia and Botswana

Lehmann, J.; Master, Sharad; Rankin, W. J.; Milani, Lorenzo; Kinnaird, Judith A.; Naydenov, Kalin; Saalmann, Kerstin; Kumar, Manesh

doi:10.1016/j.oregeorev.2015.05.009

Cited by 27 publications

(27 citation statements)

References 48 publications

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“…and references therein] and (ii) very rare indications of Mesoproterozoic magmatism (see review in Lehmann et al . [])—both abundant in the NW Kalahari Craton in Namibia (diagram 6 in Figure a). In addition, the passive margins on each side of the Damara Belt developed diachronous (diagrams 4 to 6 in Figure a) and very different lithotectonic sedimentary packages [ Becker et al ., ; Hoffman and Halverson , ; Lehmann et al ., ] casting doubts on them being conjugated passive margins.…”

Section: Discussionmentioning

confidence: 99%

Structural and geochronological constraints on the Pan‐African tectonic evolution of the northern Damara Belt, Namibia

et al. 2016

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The Pan-African Orogen formed by convergence of numerous continental blocks during the Neoproterozoic to early Cambrian. This convergence eventually led to amalgamation of Gondwana, a supercontinent crosscut by a network of highly oblique linear orogenic belts that locally intersect each other, as in NW Namibia, where the NNW trending Kaoko Belt joins the NE trending Damara Belt. The northern Damara Belt has preserved well three regional Pan-African tectonic events due to the dominance of weak Neoproterozoic marine sediments (Damara Supergroup) that have been affected by low-grade metamorphism. A newly discovered early N-S horizontal contraction, dated by 40 Ar/ 39 Ar at~590 Ma, is tentatively linked to convergence between the Congo and Kalahari cratons. This was superseded by collision between the Congo and Rio de la Plata cratons between 580 and 530 Ma that thickened and exhumed the orogenic crust of the Kaoko Belt and produced upper crustal N-S oriented folds of earlier fold trains and associated axial planar schistosities in the northern Damara Belt. A switch from E-W to NW-SE horizontal shortening occurred at 530 Ma as a result of collision with the Kalahari Craton, triggering extensive syn-orogenic magmatism in the entire Damara Belt. During this last event, southward indentation and underthrusting of the Congo Craton promontory below the Neoproterozoic cover sequences produced a deformation front in the northern Damara Belt. Our results show that highly oblique convergent processes competed over a period of~120 Ma to build Gondwana in Namibia during the late Neoproterozoic to early Cambrian.The Damara Orogen is composed of three highly oblique branches, the NNW trending Kaoko and Gariep belts and the NE trending Damara Belt [Martin and Porada, 1977;Coward, 1981;Miller, 1983;Gray et al., 2008] that were at least partly active at the same time [e.g., Miller et al., 2009] during mutual convergence of three cratonic blocks, the Rio de la Plata, Congo, and Kalahari cratons (Figure 1). Despite the Damara Orogen being extensively LEHMANN ET AL.TECTONIC EVOLUTION NORTHERN DAMARA BELT 103

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Section: Discussionmentioning

confidence: 99%

Structural and geochronological constraints on the Pan‐African tectonic evolution of the northern Damara Belt, Namibia

et al. 2016

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“…Basement gneiss complexes in the SZ of the Damara Belt show remarkable similarities with Palaeo-to late Mesoproterozoic basement complexes in the Domes Region of the Lufilian Arc of Zambia, both in terms of their geochronology and tectonostratigraphic position, as well as the structural and metamorphic evolution (Unrug 1983;Kampunzu and Cailteux 1999;Porada and Berhorst 2000;Rainaud et al 2005;Lehmann et al 2015). With the discovery of major new Cu deposits in recent years, the Domes Region has become an important Cu district in Zambia, accounting for up to 10% of Cu resources in the Central African Copperbelt (Sillitoe et al 2015).…”

Section: Regional Correlationsmentioning

confidence: 99%

Orebody geometry, fluid and metal sources of the Omitiomire Cu deposit in the Ekuja Dome of the Damara Belt in Namibia

et al. 2017

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The Omitiomire Cu deposit (resource of 137 Mt at 0.54% Cu) in the Ekuja Dome of the Damara Belt in Namibia is hosted by an anastomosing, low-angle Pan-African (ca. 520 Ma) shear zone system developed around an older (ca. 1100-1060 Ma), late Mesoproterozoic intrusive breccia between a suite of mafic rocks (originally lava flows) and later tonalitic gneisses. High-grade ore shoots preferentially formed along contacts between tectonically interleaved biotiteepidote-quartz-chalcocite schists and felsic gneisses, and are directly related to an increase in the number and cumulative thickness of thin, contact-parallel mineralized shear zones. Alteration and mineralization are associated with elevated concentrations of K 2 O, Cr, Rb, S, and Cu and a loss of Na 2 O, CaO, and MgO. Oxygen isotope fractionation for quartz-biotite, quartz-feldspar, and quartz-amphibole mineral pairs support equilibrium temperatures of between 500 and 650 °C during the fluid/rock interaction. Mineral separates from amphibole-biotite gneisses and mineralized schists have similar ranges in δ 18 O values of about 1.2 to 2 ‰ relative to VSMOW. Coexisting minerals are arranged in an order of increasing δ 18 O values from biotite, to epidote, amphibole, and quartz, suggesting that the Omitiomire Shear Zone was a rock-dominated system. Similarly, H-isotope results for mineral separates from biotite-epidote schists and amphibole gneisses do not show any reversals for D/H fractionations, with δD values of between −48 and −82 ‰, typical of metamorphic-magmatic rocks. The homogeneous and low δ 34 S values (−6.1 to −4.7 ‰ CDT) are compatible with a local redistribution of sulfur from magmatic rocks and interaction with sulfur derived from metamorphic fluids of metasedimentary origin. The relatively low fluid/rock ratios and elevated Cu values (>1500 ppm) from unaltered amphibolite point to a local redistribution of an earlier (late Mesoproterozoic) Keweenaw-type Cu mineralization into later Pan-African shear zones during the exhumation of the Ekuja Dome. The timing, polyphase evolution, and tectonic setting of the Omitiomire deposit show remarkable similarities with the large Cu deposits of the Domes Region in the adjoining Lufilian Arc of northern Zambia. This suggests the presence of a much larger, regionally significant Cu province extending from central Namibia, through northern Botswana, and into Zambia. KeywordsDamara Belt . Cu . Mesoproterozoic dome . Pan-African . Shear zone . Stable isotopes . Fluid/rock ratio . Lufilian Arc * Shawn Kitt

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“…Generalized geologic map and Cu‐Ag deposits of the Ghanzi Ridge, Kalahari Copperbelt in Botswana (modified from Lehmann et al, 2015; Hall et al, 2018). Geology is inferred from known geology and geophysics.…”

Section: Introductionmentioning

confidence: 99%

“…Recent advances in understanding the geology and origin of Cu‐Ag mineralization in the KCB is a result of in‐depth studies on subjects spanning regional‐ to deposit‐scale characterization and delineation of the KCB (e.g., Schwartz et al, 1995; Gorman, 2013; Morgan, 2013; Shephard, 2014; Lehmann et al, 2015; Hall et al, 2018), depositional environment, geochronology (e.g., Modie, 1996, 2000; Hall, Hitzman, et al, 2018; Hall et al, 2021) and provenance and distribution of metals (e.g., Schwartz et al, 1995; Modie, 1996, 2000; Kelepile et al, 2017, 2020; Hall, Hitzman, et al, 2018). These studies altogether suggest that the litho‐structural control, permeability, metal source, sulfur source, and a reductant (in‐situ or mobile) were key elements for precipitation of the Cu‐Ag ores.…”

Section: Introductionmentioning

confidence: 99%

Diagenetic and epigenetic origins for Cu‐Ag mineralization in the Khoemacau Zone 5 deposit, Kalahari Copperbelt, northwestern Botswana

et al. 2022

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In the Kalahari Copperbelt, the mechanism of regional scale Cu-Ag mineralization has remained intensely debated between early diagenesis and a single pass during a regional deformation event. At the Zone 5 Cu-Ag deposit in northwestern Botswana, the orebody is hosted preferentially by chemically reduced metasedimentary rocks that overly oxidized, hematite-bearing arkosic sandstone. An early diagenetic mineralizing event has been identified which is characterized by fine-grained stratiform pyrite, including recrystallized framboidal pyrite, intergrown with diagenetic mineral assemblages in the host-rock. Diagenetic pyrite is in textural equilibrium with chalcopyrite, sphalerite, galena, and (Fe-Co-Ni) sulfarsenide. These minerals were subsequently overprinted by a more intense, multi-stage, structurally-controlled hydrothermal Cu-Ag mineralization event related to the Damaran orogeny ($600-480 Ma). The hydrothermal Cu-Ag mineralization was deposited from hot ($236-265 C), high salinity (19-24.6 wt% NaCl equiv.) hydrothermal ore fluids. Petrographic results reveal an apparent overlap in trace metal associations (Cu, Fe, As, Zn, Pb, Ni, Co) between the two mineralizing events, which can be explained by remobilization of precursor sulfides. The major Ag-carriers in the ore are chalcocite, covellite, and bornite. The δ 34 S values of diagenetic pyrite range from À35.8 to +11.4‰, whereas those of hydrothermal epigenetic sulfides, including pyrite, range from À28.0 to +3.0‰. We propose that the hydrothermal sulfides had acquired some bacterially-reduced sulfur from earlier-formed minerals. The δ 18 O and δ 13 C values of quartz and calcite associated with the hydrothermal mineralization are typical of Neoproterozoic sediment-hosted Cu-Ag deposits. However, the δ 18 O isotopic values of the calcite gangue are anomalously depleted, which is likely due to recrystallization under metamorphic conditions. Our studies at Zone 5 indicate that the Zone 5 Cu-Ag deposit is the result of a multi-stage mineralization history that includes both diagenetic and epigenetic events (punctuated by >400 m.y.) facilitated by a strong litho-structural control.

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Regional aeromagnetic and stratigraphic correlations of the Kalahari Copperbelt in Namibia and Botswana

Cited by 27 publications

References 48 publications

Structural and geochronological constraints on the Pan‐African tectonic evolution of the northern Damara Belt, Namibia

Structural and geochronological constraints on the Pan‐African tectonic evolution of the northern Damara Belt, Namibia

Orebody geometry, fluid and metal sources of the Omitiomire Cu deposit in the Ekuja Dome of the Damara Belt in Namibia

Diagenetic and epigenetic origins for Cu‐Ag mineralization in the Khoemacau Zone 5 deposit, Kalahari Copperbelt, northwestern Botswana

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