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MDSG 2011 Genera! Ora! Presentation
Evolutien of sediment-hosted
Cu-Co ere mineralization in the Central African Copperbelt
Ph. Muchez1,*,H. EI Desouky1,A. Boyce2, D. Brems1, A. De Cleyn1,S. Dewaele3, L. Lammens 1
1,
J. Cailteux4 & O. Sikazwe5
Geodynamics and Geofluids Research Group, K.U.Leuven, Celestijnenlaan 200E, B-3001 .
2 SUERC,Scotland;3
Leuven, Belgium
RoyalMuseumtor CentralAfrica,Belgium;4 EG.M.F., GroupeForrest
International, Lubumbashi, D.R.Congo; 5 University of Zambia, School of Mines, Zambia
* Corresponding author:
[email protected] The Central African Copperbelt is one of the largest and richest Cu-Co metallogenie provinces in the world. A recent consensus suggests these high-grade stratiform deposlts resulted trom multiple mineralizationlremobilization stages [1-5]. During initial fitting, Cu and Co sulfides formed due to convective circulation of brines in the underlying rock pile including the pre-Katangan basement, trom which metals ware leached. Interaction of these brines with bacteriogenicsulfide resulted in early diagenetic(-820 Ma) stratiform mineralization [6]. This stage occurs in the DRC, but is absent or obscured in Zambia. are events then occurred during the Lufilian Orogeny [7] at -583-526 Ma. In Zambia, layerparallel veins formed at lithostatie pressures during basin inversion. Subsequently, rocks and layer-parallel veins ware folded, concentrating minerals in the hinge zones of the folds. Highly irregular veins formed at high pressures during the main phase of the orogenesis. Unfolded massive veins crosscut all preceding stages. In the DRC, Dras are remobilized in veins and late stage nodules, and cement tectonic breccias [4, 8] . To unravel this complex metallogenesis, mineralogical and geochemical studiés must be carried out on individual stages. 834Sincreases trom early diagenetic stratiform sulfides to syn-orogenic sulfides [5, 9], reflecting the evolution trom early bacteriogenic sulfides to sulfur derived trom thermochemical sulfate reduction [9-10]. Fluids associated with the first Cu-Co mineralization stage had moderate temperature (115° to :S;220°C)and.salir.;Jity (11.3 to 20.9 eq.wt% NaCI). In the DRC [4], the second Cu-Co stage is related to a hydrothermal fluid with a higher temperature (>270°C) and salinity (35 - 45 eq. wt% NaCI). Although, the barren host-rock carbonates show Sr isotope signatures compatible with Neoproterozoic marine seawater, carbonates associated with all the mineralization/remobilization stages in Zambia and with the early diagenetic mineralization stage in the DRC are significantly more radiogenic, reflecting the interaction of the fluids with basementrocks or basement-derivedsiliciclasticsedimentsderivedtrom it [5-6, 9, 11] References [1] Cailteux et al. 2005, Journalof African Earth Sciences 42, 134-158. [2] Selley et al. 2005, Economic Geology 100th Anniversary Volume, pp. 965-1000. [3] Oewaele et al. 2006, Journalof African Earth Sciences 46, 455-469. [4] EI Oesouky et al. 2009, are Geology Reviews 36, 315-332; [5] EI Oesouky et al. 2010, Mineralium Oeposita, 00110.1007/s00126-010-0298-3. [6] Muchez et al. 2008, Mineralium Oeposita 43, 575-589. [7] Brems et al. 2009, Journalof African Earth Sciences 55,185-196. [8] Cailteux & Kampunzu 1995, Musée Royal de I' Afrique Central, Annales des Sciences Géologiques [9] Muchez et al. 2010, Journalof African Earth Sciences 58, 457-474. [10] McGowan et aL, 2003, Geology 31,497-500. [11] Roberts et al. 2009, Mineralium Oeposita 44,881-891.
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