Metal sources for the Nkana and Konkola stratiform Cu–Co deposits (Zambian Copperbelt): Insights from Sr and Nd isotope ratios |
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| Institution: | 1. KU Leuven, Department of Earth and Environmental Sciences, Celestijnenlaan 200E, 3001 Leuven, Belgium;2. University of Johannesburg, Department of Geology, Auckland Park 2006, Johannesburg, South Africa;3. Ghent University, Department of Analytical Chemistry, Krijgslaan 281-S12, 9000 Ghent, Belgium;1. School of Earth Sciences and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, PR China;2. School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, PR China;3. Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, PR China;1. Consejo Nacional de Investigaciones Científicas y Técnicas, Centro Patagónico de Estudios Metalogenéticos, Instituto de Investigación en Paleobiología y Geología Universidad Nacional de Río Negro, Avenida Roca 1242, 8332 Roca, Río Negro, Argentina;2. Departamento de Geología y Petróleo, Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén, Argentina;3. Dirección Provincial de Hidrocarburos y Energía de la Provincia del Neuquén, Argentina;4. Université de Poitiers, IC2MP, CNRS-UMR 7285, Hydrasa, Bâtiment B08, Rue Albert Turpin, F-86022 Poitiers Cedex, France;5. Departamento de Geología, Universidad Nacional del Sur, San Juan 670, 8000 Bahía Blanca, Argentina;6. EGRU, School of Earth and Environmental Sciences, James Cook University, Townsville, QLD, 4811, Australia |
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| Abstract: | The Central African Copperbelt lies within the Lufilian orogenic belt, in the border region between the Democratic Republic of Congo (DRC) and Zambia. A Sr and Nd isotope study was performed on gangue carbonates associated with multiphase mineralisation at the Zambian Konkola and Nkana deposits. Comparison with isotopic signatures of basement rocks provides new insights into the likely metal source(s) for the Cu–Co mineralisation. At least three mineralisation phases can be identified with respect to the Lufilian orogeny. Gangue carbonates of the first, pre- to syn-kinematic mineralisation phase in both deposits have Sr and Nd isotopic compositions that correspond to felsic rocks of the Domes Region, a tectonic zone in the Zambian part of the Lufilian Belt where basement rocks crop out. However, the isotopic signatures from both deposits differ. This can be attributed to local variation in isotopic composition of the basement below the deposits. Radiogenic isotope ratios suggest that subsequent, syn-kinematic mineralisation at both sites occurred due to the remobilisation of precursor ore. Petrographic evidence indicates that the third, late-kinematic mineralisation phase at Nkana resulted from a renewed input of metals with a mafic affinity (e.g. Co, Ni). However, Sr and Nd isotope ratios resemble those of the earlier mineralisation phases and do not reflect a change in source composition. Nonetheless, comparison with the isotopic signatures of the Co-poor Konkola deposit and Co-rich stratiform deposits in the DRC might indicate a mafic component in the Nkana metal source. Calculated mixed isotopic compositions support such a mafic component. |
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