Abstract
The Kabanga Ni sulfide deposit represents one of the most significant Ni sulfide discoveries of the last two decades, with current indicated mineral resources of 23.23 Mt at 2.64% Ni and inferred mineral resources of 28.5 Mt at 2.7% Ni (Nov. 2008). The sulfides are hosted by a suite of ∼1.4 Ga ultramafic–mafic, sill-like, and chonolithic intrusions that form part of the approximately 500 km long Kabanga–Musongati–Kapalagulu igneous belt in Tanzania and Burundi. The igneous bodies are up to about 1 km thick and 4 km long. They crystallized from several compositionally distinct magma pulses emplaced into sulfide-bearing pelitic schists. The first magma was a siliceous high-magnesium basalt (approximately 13.3% MgO) that formed a network of fine-grained acicular-textured gabbronoritic and orthopyroxenitic sills (Mg# opx 78–88, An plag 45–88). The magma was highly enriched in incompatible trace elements (LILE, LREE) and had pronounced negative Nb and Ta anomalies and heavy O isotopic signatures (δ18O +6 to +8). These compositional features are consistent with about 20% contamination of primitive picrite with the sulfidic pelitic schists. Subsequent magma pulses were more magnesian (approximately 14–15% MgO) and less contaminated (e.g., δ18O +5.1 to +6.6). They injected into the earlier sills, resulting in the formation of medium-grained harzburgites, olivine orthopyroxenites and orthopyroxenites (Fo 83–89, Mg# opx 86–89), and magmatic breccias consisting of gabbronorite–orthopyroxenite fragments within an olivine-rich matrix. All intrusions in the Kabanga area contain abundant sulfides (pyrrhotite, pentlandite, and minor chalcopyrite and pyrite). In the lower portions and the immediate footwall of two of the intrusions, namely Kabanga North and Kabanga Main, there occur numerous layers, lenses, and veins of massive Ni sulfides reaching a thickness of several meters. The largest amount of high grade, massive sulfide occurs in the smallest intrusion (Kabanga North). The sulfides have heavy S isotopic signatures (δ34S wr = +10 to +24) that broadly overlap with those of the country rock sulfides, consistent with significant assimilation of external sulfur from the Karagwe–Ankolean sedimentary sequence. However, based partly on the relatively homogenous distribution of disseminated sulfides in many of the intrusive rocks, we propose that the Kabanga magmas reached sulfide saturation prior to final emplacement, in staging chambers or feeder conduits, followed by entrainment of the sulfides during continued magma ascent. Oxygen isotope data indicate that the mode of sulfide assimilation changed with time. The heavy δ18O ratios of the early magmas are consistent with ingestion of the sedimentary country rocks in bulk. The relatively light δ18O ratios of the later magmas indicate less bulk assimilation of the country rocks, but in addition the magmas selectively assimilated additional S, possibly through devolatization of the country rocks or through cannibalization of magmatic sulfides deposited in the conduits by preceding magma surges. The intrusions were tilted at ca. 1.37 Ga, during the Kibaran orogeny and associated synkinematic granite plutonism. This caused solid-state mobilization of ductile sulfides into shear zones, notably along the base of the intrusions where sulfide-hornfels breccias and lenses and layers of massive sulfides may reach a thickness of >10 m and can extend for several 10 s to >100 m away from the intrusions. These horizons represent an important exploration target for additional nickel sulfide deposits.
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References
Arndt NT (2005) The conduits of magmatic ore deposits. In: Mungall JE (ed) Exploration for platinum-group element deposits. Mineral Assoc Can, Short Course Series 35:181-201
Barnes S-J, Picard C, Giovenazzo D, Tremblay C (1992) The composition of nickel-copper sulphide deposits and their host rocks from the Cape Smith Fold Belt, northern Quebec. Austr J Earth Sci 39:335–347
Barnes S-J, Melezhik VA, Sokolov SV (2001) The composition and mode of formation of the Pechenga nickel deposits, Kola Peninsula, northwestern Russia. Can Min 39:447–471
Bea F, Pereira MD, Stroh A (1994) Mineral/leucosome trace-element partitioning in a peraluminous migmatite (a laser ablation–ICP-MS study). Chem Geol 117:291–312
Boudreau AE, Meurer WP (1999) Chromatographic separation of the platinum-group elements, gold, base metals and sulfur during degassing of a compacting and solidifying igneous crystal pile. Contrib Mineral Petrol 134:174–185
Cahen L, Delhal J, Vail JR, Bonhomme M, Ledent D (1984) The geochronology and evolution of equatorial Africa. Clarendon, Oxford, p 495
Deblond A (1990) Late Kibaran layered igneous rocks from eastern Burundi. A progress report. IGCP No 255 Newsletter/Bulletin 3:9–17
Deblond A (1994) Geologie et petrologie des Massifs basiques et ultrabasiques de la ceinture Kabanga-Musongati au Burundi. Musée Royal de L’Afrique Centrale, Annales, Sciences Geologiques 99:123
Deblond A, Tack L (1999) Main characteristics and review of mineral resources of the Kabanga-Musongati mafic-ultramafic alignment in Burundi. J Afr Earth Sci 29:313–328
Duchesne J-C, Liegeois J-P, Deblond A, Tack L (2004) Petrogenesis of the Kabanga-Musongati layered mafic-ultramafic intrusions in Burundi (Kibaran Belt): geochemical, Sr-Nd isotopic constraints and Cr-Ni behaviour. J Afr Earth Sci 39:133–145
Evans DM, Byemelwa L, Gilligan J (1999) Variability of magmatic sulphide composition at the Kabanga nickel prospect, Tanzania. J Afr Earth Sci 29:329–351
Evans DM, Boadi I, Byemelwa L, Gilligan J, Kabete J, Marcet P (2000) Kabanga mafic Ni sulfide deposits, Tanzania: morphology and geochemistry of associated intrusions. J Afr Earth Sci 30:651–674
Fernandez-Alonso M, Tack L, De Waele B, Cutten H, Baudet D, Tahon A (2006) The NE Kibaran belt (NKB): New uniform stratigraphies and GIS compiled geological map. Abstr., 21st Coll on African Geology, Maputo
Gosse R (1992) The Kabanga Ni-(Co-Cu) sulphide deposit, western Tanzania. IGCP no 255 Newsletter/Bulletin 4:73–76
Grey IM (1967) Geological map of Ngara with explanation. Mineral resources division, Dodoma, Tanzania. Quarter degree sheet 29 and 29W, scale 1: 125.000
Kokonyangi J, Armstrong R, Kampunzu A, Yoshida M, Okudaira T (2004) U-Pb zircon geochronology and petrology of granitoids from Mitwaba (Katanga, Congo): Implications for the evolution of the Mesoproterozoic Kibaran belt. Prec Res 132:79–106
Kokonyangi J, Kampunzu AB, Pouyol M, Okudaira T, Yoshida M, Shabeer KP (2005) Petrology and geochronology of Mesoproterozoic mafic-intermediate plutonic rocks from Mitwaba (D.R. Congo): implications for the evolution of the Kibaran belt in central Africa. Geol Mag 142:109–130
Layton-Matthews D, Lesher CM, Burnham OM et al (2007) Magmatic Ni-Cu-PGE deposits in the Thompson nickel belt. In: Goodfellow WD (ed) Mineral deposits in Canada: a synthesis of major deposit types, district metallogeny, the evolution of geological provinces and exploration methods. Geol Assoc Can Spec Publ 5, Ottawa
Li C, Maier WD, de Waal SA (2001) Magmatic Ni-Cu vs PGE deposits: Contrasting genetic controls and exploration implications. S Afr J Geol 104:309–318
Li C, Ripley EM, Mathez EA (2003) The effect of S on the partitioning between olivine and silicate melt in MORB. Chem Geol 201:295–306
Li C, Xu Z, De Waal SA, Ripley EM, Maier WD (2004) Compositional variations of olivine from the Jinchuan Ni-Cu sulfide deposit, western China: implications for ore genesis. Min Deposita 39:159–172
Maier WD, Barnes S-J (2010) The Kabanga Ni sulfide deposits, Tanzania II: Chalcophile element geochemistry. Min Deposita, in press
Maier WD, Gomwe T, Barnes S-J, Li C, Theart H (2004) Platinum-group elements in the Uitkomst Complex, South Africa. Econ Geol 99:499–516
Maier WD, Peltonen P, Livesey T (2007) The ages of the Kabanga North and Kapalagulu intrusions, western Tanzania: a reconnaissance study. Econ Geol 102:147–154
Maier WD, Barnes S-J, Bandyayera D, Livesey T, Li C, Ripley E (2008a) Early Kibaran rift-related mafic-ultramafic magmatism in western Tanzania and Burundi: petrogenesis and ore potential of the Kapalagulu and Musongati layered intrusions. Lithos 101:24–53
Maier WD, Barnes S-J, Chinyepi G, Barton JM, Eglington B, Setshedi I (2008b) The composition of magmatic Ni-Cu-(PGE) sulfide deposits in the Tati and Selebi Phikwe belts of eastern Botswana. Mineral Deposita 43:37–60
Mattey D, Lowry D, Macpherson (1994) Oxygen isotope composition of mantle peridotites. Earth Planet Sci Lett 128:231–241
McDonough WF, Sun S-s (1995) The composition of the Earth. Chem Geol 120:223–253
Naldrett AJ (1997) Key factors in the genesis of Noril’sk, Jinchuan, Voisey’s Bay and other world-class Ni-Cu-PGE deposits: implications for exploration. Austr J Earth Sci 44:283–315
Naldrett AJ (2004) Magmatic sulfide deposits. Springer, Heidelberg, p 727
Ntungicimpaye A, Tack L (1992) Les metavolcanites intermediaires a acides kibariennes du NW du Burundi. IGCP Newsletter/Bulletin 4:45–50
Oberthuer T, Melcher F, Lodziak J, Wöhrl C (2002) Kabanga, Tanzania: Ni-As-PGE rich veins in the footwall of the Sulfide ore bodies. BGR, Hannover
Patino Douce AE, Johnston AD (1991) Phase equilibria and melt productivity in the pelitic system: implications for the origin of peraluminous granitoids and alunminous granulites. Contrib Mineral Petrol 107:202–218
Peltonen P (2005) Svecofennian mafic-ultramafic intrusions. In: Lehtinen M, Nurmi PA, Rämö OT (eds) Precambrian geology of Finland; key to the evolution of the Fennoscandian shield: developments in Precambrian Geology 14. Elsevier, Amsterdam
PNUD-UNDP (1977) Gisements lateritiques de nickel au Burundi. Recherches minières (technical report), United Nations, New York, 39 p
Pohl W (1994) Metallogeny of the northeastern Kibara belt, Central Africa – recent perspectives. Ore Geology Reviews 9:105–130
Rice A, Moore J (2001) Physical modeling of he formation of komatiite-hosted Ni deposits and a review of the thermal erosion paradigm. Can Min 39:491–503
Ripley EM (1981) Sulfur isotopic studies of the Dunka Road Cu-Ni deposit, Duluth Complex, Minnesota. Econ Geol 76:610–620
Ripley EM (1999) Systematics of sulphur and oxygen isotopes in mafic igneous rocks and related Cu-Ni-PGE mineralization. In: Keays RR, Lesher CM, Lightfoot PC, Farrow CEG (eds) Dynamic processes in magmatic ore deposits and their application to mineral exploration: Geol. Assoc. Can., Short Course Notes 13:133-158
Roeder PL, Emslie RF (1970) Olivine-liquid equilibrium. Contrib Mineral Petrol 71:257–269
Seat Z, Beresford SW, Grguric BA, Waugh RS, Hronsky JMA, Gee MAM, Groves DI, Mathison CI (2007) Architecture and emplacement of the Nebo-Babel gabbronorite-hosted magmatic Ni-Cu-PGE sulphide deposit, West Musgrave, Western Australia. Mineral Deposita 42:551–581
Tack L, Liegeois J-P, Deblond A, Duchesne JC (1994) Kibaran A-type granitoids and mafic rocks generated by two mantle sources in late orogenic setting (Burundi). Prec Res 68:323–356
Tack L, Fernandez-Alonso M, Tahon A, Wingate MTD (2002) Meso and Neoproterozoic emplacement ages of magmatic rocks in Burundi: new constraints for the geodynamic evolution of the Northeastern Kibaran belt (NKB). Abstract Vol IGCP 418/440 (the Kibaran of southwest Africa) technical meeting, Windhoek, 2002
Tack L, Wingate MTD, De Waele B, Meert J, Belousova EA, Griffin WL, Tahon A, Fernandez-Alonso M, Baudet D, Cutten HNC, Dewaele S (2008) The Proterozoic Kibaran belt in central Africa: intracratonic 1375 Ma emplacement of a LIP. Abstr., XXXIII Int Geol Congr Oslo
Teale EO (1931) Annual report of the Geological Survey Department. Geological Survey Department, Tanganyika Territory, p 41
Vokes FM (1969) A review of the metamorphism of sulphide deposits. Earth-Sci Rev 5:99–143
Acknowledgements
The Kabanga Nickel Company is thanked for funding the analytical work and travel to site. Additional funding was provided by NSERC (to SJB) and NSF (grants EAR 0608645 and EAR 0710910 to ER). Special thanks go to the Kabanga exploration staff for their invaluable logistical support and good company. J Brophy, E Elswick, and C Moore are thanked for thoughtful reviews of earlier versions of parts of this paper. Later versions were reviewed by PC Lightfoot, JS Marsh, J-C Duchesne, X Yang, and an anonymous reviewer. Craig Moore and Steve Studley of the Indiana University Stable Isotope Research Facility are thanked for assistance with various phases of stable isotopic analyses. Part of this research was supported by a Society of Economic Geology student research grant to A. Sarkar.
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Supplementary Table 1
Reproducibility and precision of ICP-MS analyses (XLS 36 kb)
Supplementary Table 2
Composition of Kabanga olivines (XLS 54 kb)
Supplementary Table 3
Composition of Kabanga and Luhuma orthopyroxenes (XLS 22 kb)
Supplementary Table 4
Compositions of Kabanga and Luhuma plagioclase (XLS 19 kb)
Supplementary Table 5
Composition of Kabanga chromites (XLS 39 kb)
Supplementary Table 6
Major and trace element concentrations in Kabanga silicate rocks (XLS 156 kb)
Supplementary Table 7
Composition of Kabanga sedimentary rocks (XLS 48 kb)
Supplementary Table 8
Modeling of Kabanga magmas (XLS 44 kb)
Supplementary Table 9
Oxygen and sulfur isotopes of minerals and whole-rocks from ore-bearing intrusions in the Kabanga area (XLS 61 kb)
Supplementary Table 10
Sulfur and oxygen isotopes of sedimentary country rocks in the Kabanga area (XLS 23 kb)
Supplementary Fig. 1
Photomicrographs of Kabanga sedimentary rocks. (A) Sulfidic andalusite–muscovite schist, MNB, KN01-05, 538 m. (B) Banded pelite, MNB, KN01-01, 1,645 m. (C) Bleached contact zone in hornfels adjacent to ultramafic rock, Kabanga Main, KN05-01, 138 m. (PDF 2,334 kb)
Supplementary Fig. 2
CIPW norms of Kabanga and Luhuma rocks. Silicate rocks from Kapalagulu and Musongati are shown for comparison (Maier et al. 2008a). (PDF 20 kb)
Supplementary Fig. 3
(A, B) Compositional variation of Kabanga orthopyroxenes, plotting Al2O3 and Cr2O3 vs Mg#. Dashed line represents field of Uitkomst orthopyroxenes (Maier et al. 2004) and shaded field represents compositional range of Bushveld orthopyroxenes (data from Teigler and Eales 1996, The Lower and Critical Zones of the western limb of the Bushveld Complex, as indicated by the Nooitgedacht boreholes. Geol Surv S Afr Bull 111: 126p). (C, D) Compositional variation of Kabanga chromites plotting Fe# and Ni vs Mg#. Bushveld Lower Zone (LZ) data are from Teigler and Eales (1996). (PDF 20 kb)
Supplementary Fig. 4
Variation in trace element ratios and S within the MNB body (as intersected by drill core KN01-08). Yellow-shaded blocks indicate observed ranges within units. See Fig. 7 of paper for legend. (PDF 16 kb)
Supplementary Fig. 5
Histogram of whole-rock δ34S in different intrusions at Kabanga and Luhuma, and their sedimentary host rocks. (PDF 15 kb)
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ESM 3
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Maier, W.D., Barnes, SJ., Sarkar, A. et al. The Kabanga Ni sulfide deposit, Tanzania: I. Geology, petrography, silicate rock geochemistry, and sulfur and oxygen isotopes. Miner Deposita 45, 419–441 (2010). https://doi.org/10.1007/s00126-010-0280-0
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DOI: https://doi.org/10.1007/s00126-010-0280-0