Shear-zone hosted copper mineralisation of the Omitiomire deposit — Structural controls of fluid flow and mineralisation during subduction accretion in the Pan-African Damara Belt of Namibia

Kitt, Shawn; Kisters, Alexander F. M.; Steven, Nick; Maiden, K. J.; Hartmann, Karl

doi:10.1016/j.oregeorev.2015.10.035

Cited by 15 publications

(18 citation statements)

References 22 publications

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“…1 and electronic supplementary material (ESM) 1). The striking similarities between the Omitiomire deposit and the large Cu deposits in the Domes Region of Zambia suggest similar mineralization processes and controls and an extension of the Cu province from the Domes Region into Namibia (Kitt et al 2016).…”

Section: Introductionmentioning

confidence: 89%

“…1100 Ma) tonalites and amphibolites (Steven et al 2000) and are structurally overlain by the medium-P, medium-T amphibolite-facies metaturbiditic Kuiseb Formation, and imbricated slivers of serpentinite (Kasch 1986(Kasch , 1987. Both the structural location and lithological assemblages point to a tectonic position of the gneiss domes close to, or within, the subduction channel, recording initial burial and subsequent expulsion of basement rocks during northward subduction of the Kalahari Craton (Kitt et al 2016).…”

Section: Geological Overviewmentioning

confidence: 96%

“…The tonalitic magma intruded and brecciated a volumetrically subordinate mafic suite of amphibolite. Original intrusive contacts and the brecciation of the older amphibolitic sequence is preserved at lower strain intensities (Kitt et al 2016) (ESM 2a). At higher strains, angular xenoliths appear progressively sheared out and transposed into the regional gneissic fabrics (S2), associated with the partial or near pervasive retrogression of the rocks (Kitt et al 2016) (ESM 2b).…”

Section: Host Rocksmentioning

confidence: 99%

“…Drill core logging and structural mapping of scattered outcrops in the area revealed at least two deformation phases (Kitt et al 2016). The first phase (D1) in felsic gneisses is defined by the grain-shape preferred orientation of quartzfeldspar aggregates and biotite, and is only observed in the hinges of isoclinal, near recumbent F2 folds that refold the early S1 gneissosity.…”

Section: Structurementioning

confidence: 99%

“…S2 is a well-developed transposition fabric, formed through the progressive refolding of earlier intrusive contacts and the S1 gneissosity by tight to isoclinal F2 folds. This gneissic fabric forms the dominant structural element in the deposit (Steven et al 2000;Kitt et al 2016), as well as on a regional scale (Kasch 1987). F2 folds at Omitiomire show north-south trends and subhorizontal northerly or southerly plunges.…”

Section: Structurementioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 89%

Section: Geological Overviewmentioning

confidence: 96%

Section: Host Rocksmentioning

confidence: 99%

Section: Structurementioning

confidence: 99%

Section: Structurementioning

confidence: 99%

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