Pb isotopic constraints on the formation of the Dikulushi Cu-Pb-Zn-Ag mineralisation, Kundelungu Plateau (Democratic Republic of Congo)

• Published in: Mineralium Deposita
• Main Authors: Haest, Maarten, Schneider, Jens, Cloquet, Christophe, Latruwe, Kris, Vanhaecke, Frank, Muchez, Philippe
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer-Verlag 2010
• Subjects: dikulushi cu-ag deposit; lead isotopes; polysulphide vein-type mineralisation; lufilian arc; central african copperbelt; lead-isotope; neoproterozoic nguba; katanga supergroup; lufilian foreland; northern sweden; icp-ms; deposit; zambia; belt; Northern Sweden
• Online Access: https://lirias.kuleuven.be/handle/123456789/305748; https://doi.org/10.1007/s00126-010-0279-6; https://lirias.kuleuven.be/bitstream/123456789/305748/1//Pb+isotopic+constraints+on+the+formation+.pdf

Base metal-Ag mineralisation at Dikulushi and in other deposits on the Kundelungu Plateau (Democratic Republic of Congo) developed during two episodes. Subeconomic Cu-Pb-Zn-Fe polysulphide ores were generated during the Lufilian Orogeny (c. 520 Ma ago) in a set of E-W- and NE-SW-oriented faults. Their lead has a relatively unradiogenic and internally inhomogeneous isotopic composition (Pb-206/Pb-204 = 18.07-18.49), most likely generated by mixing of Pb from isotopically heterogeneous clastic sources. These sulphides were remobilised and enriched after the Lufilian Orogeny, along reactivated and newly formed NE-SW-oriented faults into a chalcocite-dominated Cu-Ag mineralisation of high economic interest. The chalcocite samples contain only trace amounts of lead and show mostly radiogenic Pb isotope signatures that fall along a linear trend in the Pb-207/Pb-204 vs. Pb-206/Pb-204 diagram (Pb-206/Pb-204 = 18.66-23.65; Pb-207/Pb-204 = 15.72-16.02). These anomalous characteristics reflect a two-stage evolution involving admixture of both radiogenic lead and uranium during a young fluid event possibly c. 100 Ma ago. The Pb isotope systematics of local host rocks to mineralisation also indicate some comparable young disturbance of their U-Th-Pb systems, related to the same event. They could have provided Pb with sufficiently radiogenic compositions that was added to less radiogenic Pb remobilised from precursor Cu-Pb-Zn-Fe polysulphides, whereas the U most likely originated from external sources. Local metal sources are also suggested by the Pb-208/Pb-204-Pb-206/Pb-204 systematics of combined ore and rock lead, which indicate a pronounced and diversified lithological control of the immediate host rocks on the chalcocite-dominated Cu-Ag ores. The Pb isotope systematics of polysulphide mineralisation on the Kundelungu Plateau clearly record a diachronous evolution. status: published