International Journal of Earth Sciences

, Volume 99, Issue 8, pp 1773–1790 | Cite as

SHRIMP U–Pb zircon geochronology and Sr–Nd isotopic systematic of the Neoproterozoic Ghimbi-Nedjo mafic to intermediate intrusions of Western Ethiopia: a record of passive margin magmatism at 855 Ma?

  • Binyam W. Woldemichael
  • Jun-Ichi Kimura
  • Daniel J. Dunkley
  • Kenichiro Tani
  • Hiroto Ohira
Original Paper


The reworked Pre-Neoproterozoic and juvenile Neoproterozoic terrane of the Western Ethiopian Shield (WES) consists of three N–S trending terranes. These are the western migmatitic gneissic terrane, the central metavolcano sedimentary terrane (CVST) and the eastern migmatitic gneissic terrane. The eastern part of the CVST mostly consists of suture-related ultramafic-metasedimentary complexes, whereas metavolcanics predominate in the western part. Gabbroic to granitic intrusions frequently occur in the CVST and in adjacent areas. New zircon SHRIMP U–Pb ages for two gabbros and three diorites in the Ghimbi-Nedjo region of the WES indicate magmatic crystallization ages. Two pulses of magmatism, at 860–850 and 795–785 Ma, are documented with the former for the first time. The tholeiitic Kemashi diorite and Bikilal-Ghimbi gabbros have oceanic affinities and yield U/Pb zircon ages of 856.3 ± 9.8 and 846.0 ± 7.6 Ma, respectively. The calc-alkaline Gebeya Kemisa pyroxene diorite, and the Senbet Dura hornblende diorite plus the tholeiitic Wayu Meni gabbro, which collectively have arc-back arc characteristics are indistinguishable at ages of 794.3 ± 9.4, 787.7 ± 8.8 and 778.1 ± 6.3 Ma, respectively. Positive εNd (4.5–7.0) and low initial 87Sr/86Sr (0.7029 ± 0.0002) and a mean TDM model age of 0.95 Ga for the Ghimbi-Nedjo region (mean TDM model age of 0.95 Ga for the WES overall) indicate that the magmas were generated from juvenile Neoproterozoic depleted mantle sources, with no discernable involvement of pre-Neoproterozoic continental crust. The occurrence of gabbros and diorites with oceanic tholeiite affinities combined with the new ages suggests that the intrusions were emplaced in the earliest stages of the rifting of Rodinia. This event in the WES led to the development of a passive margin and associated plume-type magmatism at ~855 Ma. The two intrusive groups with differing magma chemistry and ages suggest that the earliest magmatism was tholeiitic and associated with the passive margin system followed by continental breakup to form the Mozambique Ocean. The combination of tholeiitic and calc-alkaline magmatism was related to arc and back-arc basin formation and later terrane accretion (~830–690 Ma).


SHRIMP U–Pb dating Intrusions Neoproterozoic Passive margin Western Ethiopian Shield EAAO 


  1. Abdelsalam MG, Stern RJ (1996) Sutures and shear zones in the Arabian Nubian Shield. J Afr Earth Sci 23:289–310CrossRefGoogle Scholar
  2. Abdelsalam MG, Liégeois JP, Stern RJ (2002) The Saharan metacraton. J Afr Earth Sci 34:119–136CrossRefGoogle Scholar
  3. Abraham A (1989) Tectonic history of the Pan-African low-grade belt of western. Ethiopia Note 305. Ethiopian Institute of Geological Survey, Addis Ababa, Ethiopia, p 22Google Scholar
  4. Agar RA, Stacey JS, Whitehouse MJ (1992) Evolution of the southern Afif terrane––a geochronologic study. Open-file rep DGMR-OF-10–15. Saudi Arabian Directorate General of Mineral Resources, pp 41Google Scholar
  5. Alemu T (2005) Discussion on “Geological setting and tectonic subdivision of the Neoproterozoic orogenic belt of Tuludimtu, Western Ethiopia. [J Afr Earth Sci 36:329–343]”. J Afr Earth Sci 41:329–332CrossRefGoogle Scholar
  6. Alemu T, Abebe T (2000) Geology of the Ghimbi area. Memoir 15. Geological Survey of Ethiopia, Addis Ababa, Ethiopia, p 158Google Scholar
  7. Allen A, Tadesse G (2003) Geological setting and tectonic subdivision of the Neoproterozoic orogenic belt of Tuludimtu, Western Ethiopia. J Afr Earth Sci 36:329–343CrossRefGoogle Scholar
  8. Anderson DL (1994) Superplumes or supercontinents? Geol 22:39–42CrossRefGoogle Scholar
  9. Ayalew T, Peccerillo A (1998) Petrology and geochemistry of the Gore-Gambella plutonic rocks: implications for magma genesis and the tectonic setting of the Pan-African Orogenic Belt of Western Ethiopia. J Afr Earth Sci 27:397–416CrossRefGoogle Scholar
  10. Ayalew T, Bell K, Moore JM, Parrish RR (1990) U–Pb and Rb–Sr geochronology of the Western Ethiopian Shield. Geol Soc Am Bull 102:1309–1316CrossRefGoogle Scholar
  11. Berhe SM (1990) Ophiolites in northeast and East Africa: implication for Proterozoic crustal growth. J Geol Soc Lond 147:41–57CrossRefGoogle Scholar
  12. Boillot G, Froitzheim N (2001) Non-volcanic rifted margins, continental break-up and the onset of sea-floor spreading: some outstanding questions. In: Wilson RCL, Whitmarsh RB, Taylor B, Froitzheim N (eds) Non-volcanic rifting of continental margins: a comparison of evidence from land and sea. Geological Society of London, London, Special publication 187, pp 9–30Google Scholar
  13. Braathen A, Grenne T, Selassie MG, Worku T (2001) Juxtaposition of Neoproterozoic units along the Baruda-Tulu Dimtu shear-belt in the East African Orogen of Western Ethiopia. Precamb Res 107:215–234CrossRefGoogle Scholar
  14. Carson CJ, Ague JJ, Coath CD (2002) U–Pb geochronology from Tonagh Island, East Antarctica: implications for the timing of ultra-high temperature metamorphism of the Napier Complex. Precamb Res 116:237–263CrossRefGoogle Scholar
  15. Coffin MF, Eldholm O (1994) Large igneous provinces: crustal structure, dimensions, and external consequences. Rev Geophys 32:1–36CrossRefGoogle Scholar
  16. Cornen G, Girardeau J, Monnier C (1999) Basalts, underplated gabbros and pyroxenites record the rifting process of the West Iberian margin. Mineral Petrol 67:111–142CrossRefGoogle Scholar
  17. Courtillot V, Jaupart C, Manighetti I, Tapponnier P, Besse J (1999) On causal links between flood basalts and continental break-up. Earth Planet Sci Lett 166:177–195CrossRefGoogle Scholar
  18. Courtillot V, Davaille A, Besse J, Stock J (2003) Three distinct types of hotspots in the Earth’s mantle. Earth Planet Sci Lett 205:295–308CrossRefGoogle Scholar
  19. Davidson A (1983) The Omo River project: reconnaissance geology and geochemistry of parts of Illababor, Kefa, Gamu Gofa and Sidamo, Ethiopia. Ethiopian Inst of Geolog Surv Bull 2:89Google Scholar
  20. Depaolo DJ (1981) Neodymium isotopes in the Colorado Front Range and crust–mantle evolution in the Proterozoic. Nature 291:193–196CrossRefGoogle Scholar
  21. Geoffroy L (2005) Volcanic passive margins. C R Geosci 337:1398–1408CrossRefGoogle Scholar
  22. GEOROC (2005) Geochemistry of rocks of oceanic and continental.
  23. Grenne T, Pedersen RB, Bjerkgård T, Braathen A, Selassie MG, Worku T (2003) Neoproterozoic evolution of Western Ethiopia: igneous geochemistry, isotope systematics and U–Pb ages. Geol Mag 140:373–395CrossRefGoogle Scholar
  24. Izumi S, Maehara K, Morris PA, Sawada Y (1994) Sr isotope data of some GSJ rock reference samples. Mem Fac Sci Shimane Univ 28:83–86Google Scholar
  25. Izumi S, Morris PA, Sawada Y (1995) Nd isotope data for GSJ reference samples JB-1a, JB-3 and JG-1a and the La Jolla standard. Mem Fac Sci Shimane Univ 29:73–76Google Scholar
  26. Jacobs J, Thomas RJ (2004) Himalayan-type indenter-escape tectonics model for the southern part of the late Neoproterozoic-early Paleozoic East African–Antarctic orogen. Geol 32:721–724CrossRefGoogle Scholar
  27. Johnson PR, Woldehaimanot B (2003) Development of the Arabian–Nubian shield: perspectives on accretion and deformation in the northern East African Orogen and the assembly of Gondwana. In: Yoshida M, Dasgupta S, Windley B (eds) Proterozoic East Gondwana: supercontinent assembly and breakup. Geological Society of London, London, Special Publication 206, pp 289–325Google Scholar
  28. Johnson TE, Ayalew T, Mogessie A, Kruger FJ, Poujol M (2004) Constraints on the tectonometamorphic evolution of the Western Ethiopia Shield. Precamb Res 133:305–327CrossRefGoogle Scholar
  29. Kazmin V, Shiferaw A, Balcha T (1978) The Ethiopian basement: stratigraphy and possible manner of evolution. Int J Earth Sci 67:531–546Google Scholar
  30. Kazmin V, Shiferaw A, Tefera M, Berhe SM, Chewaka S (1979) Precambrian structure of Western Ethiopia. Ann Geol Surv Egypt 9:1–18Google Scholar
  31. Kebede T, Koeberl C (2003) Petrogenesis of A-type granitoids from the Wallagga area, Western Ethiopia: constraints from mineralogy, bulk-rock chemistry, Nd and Sr isotopic compositions. Precamb Res 121:1–24CrossRefGoogle Scholar
  32. Kebede T, Koeberl C, Koller F (1999) Geology, geochemistry and petrogenesis of intrusive rocks of the Wallagga area, Western Ethiopia. J Afr Earth Sci 29:715–734CrossRefGoogle Scholar
  33. Kebede T, Kloetzli US, Koeberl C (2001a) U/Pb and Pb/Pb zircon ages from granitoid rocks of Wallagga area: constraints on magmatic and tectonic evolution of Precambrian rocks of Western Ethiopia. Mineral Petrol 71:251–271CrossRefGoogle Scholar
  34. Kebede T, Koeberl C, Koller F (2001b) Magmatic evolution of the Suqii-Wagga garnet-bearing two-mica granite, Wallagga area, Western Ethiopia. J Afr Earth Sci 32:193–221CrossRefGoogle Scholar
  35. Kebede T, Horie K, Hidaka H, Terada K (2007) Zircon ‘microvein’ in peralkaline granitic gneiss, Western Ethiopia: origin, SHRIMP U–Pb geochronology and trace element investigations. Chem Geol 242:76–102CrossRefGoogle Scholar
  36. Kennedy WQ (1964) The structural differentiation of Africa in the Pan-African ± 500 m.y. tectonic episode, 8th annual report on scientific results. University of Leeds, Leeds, p 50Google Scholar
  37. Key RM, Charlsey TJ, Hackman BD, Wilkinson AF, Rundle CC (1989) Superimposed Upper Proterzoic collision controlled orogenesis in the Mozambique orogenic belt of Kenya. Precamb Res 44:197–225CrossRefGoogle Scholar
  38. Kimura J-I, Yoshida T (2006) Contributions of slab fluid, mantle wedge and crust to the origin of Quaternary lavas in the NE Japan arc. J Petrol 47:2185–2232CrossRefGoogle Scholar
  39. Kimura J-I, Sisson TW, Nakano N, Coombs ML, Lipman PW (2006) Isotope geochemistry of early Kilauea magmas from the submarine Hilina bench: the nature of the Hilina mantle component. J Volcanol Geotherm Res 151:51–72CrossRefGoogle Scholar
  40. Kröner A (1984) Late Precambrian plate tectonics and orogeny: a need to redefine the term Pan-African. In: Klerkx J, Michot J (eds) African geology. Musee Royal L’Afrique Centrale, Tervuren, pp 23–28Google Scholar
  41. Kröner A, Sassi FP (1996) Evolution of the northern. Somali basement: new constraints zircon ages. J Afr Earth Sci 22:1–15CrossRefGoogle Scholar
  42. Kröner A, Stern RJ, Dawoud AS, Compston W, Reischmann T (1987) The Pan-African continental margin in northeastern Africa: evidence from a geochronological study of granulites at Sabaloka, Sudan. Earth Planet Sci lett 85:91–104CrossRefGoogle Scholar
  43. Küster D, Liegeois J-P, Matukov D, Sergeev S, Lucassen F (2008) Zircon geochronology and Sr, Nd, Pb isotope geochemistry of granitoids from Bayuda Desert and Sabaloka (Sudan): evidence for a Bayudian event (920–900 Ma) preceding the Pan-African orogenic cycle (860–590 Ma) at the eastern boundary of the Saharan Metacraton. Precamb Res 164:16–39CrossRefGoogle Scholar
  44. Ludwig KR (2003) Isoplot/Ex (Version 3): the geochronological toolkit for Excel. University of California, Berkeley, Geochrono Center Spec Publ 4Google Scholar
  45. Maas R, Kinny PD, Williams IS, Froude DO, Compston W (1992) The earth’s oldest known crust: a geochronological and geochemical study of 3900–4200-Ma-old detrital zircons from Mt. Narryer and Jack Hills, Western Australia. Geochim Cosmochim Acta 56:1281–1300CrossRefGoogle Scholar
  46. Meert JG (2003) A synopsis of events related to the assembly of eastern Gondwana. Tectonophys 362:1–40CrossRefGoogle Scholar
  47. Mogessie A, Belete KH, Hoinkes G (2000) Yubdo-Tulu Dimtu mafic–ultramafic belt, Alaskan-type intrusions in Western Ethiopia: its implication to the Arabian–Nubian Shield and tectonics of the Mozambique belt. Afr Earth Science Abstract: 18th Colloquium of African geology Graz 30(Suppl 1). doi:10.1016/S0899-5362(00)00051-8
  48. Nelson BK, DePaolo DJ (1984) Rapid production of continental crust 1.7 to 1.9 b.y. ago: Nd isotopic evidence from the basement of the North American mid-continent. Geol Soc Am Bull 96:746–754CrossRefGoogle Scholar
  49. Paces JB, Miller JD (1993) U–Pb ages of the Duluth complex and related mafic intrusions, northeastern Minnesota. Geochronologic insights into physical petrogenetic, paleomagnetic and tectonomagnetic processes associated with the 1.1 Ga mid-continent rift system. J Geophys Res 98:13997–14013CrossRefGoogle Scholar
  50. Patchett PJ, Kuovo O, Hedge CE, Tatsumoto M (1981) Evolution of continental crust and mantle heterogeneity: evidence from Hf isotopes. Contrib Mineral Petrol 78:279–297CrossRefGoogle Scholar
  51. Pearce JA, Stern RJ, Bloomer HS, Fryer P (2005) Geochemical mapping of the Mariana arc-basin system: implications for the nature and distribution of subduction components. Geochem Geophys Geosyst 6:Q07006. doi:10,1029/2004GC000895 CrossRefGoogle Scholar
  52. Schärer U, Kornprobst J, Beslier MO, Boillot G, Girardeau J (1995) Gabbro and related rock emplacement beneath rifting continental crust: U–Pb geochronological and geochemical constraints for the Galicia passive margin (Spain). Earth Planet Sci Lett 130:187–200CrossRefGoogle Scholar
  53. Schärer U, Girardeau J, Cornen G, Boillot G (2000) 138–121 Ma asthenospheric magmatism prior to continental break-up in the North Atlantic and geodynamic implications. Earth Planet Sci Lett 181:555–572CrossRefGoogle Scholar
  54. Seyid G (2002) Geology of the Abu Ramla area. Geol Surv Ethiopia Mem 16:133Google Scholar
  55. Stacey JS, Kramers JD (1975) Approximation of terrestrial lead isotope evolution by a two-stage model. Earth Planet Sci Lett 26:207–221CrossRefGoogle Scholar
  56. Stein M, Goldstein SL (1996) From mantle head to continental lithosphere in the Arabian–Nubian Shield. Nature 382:773–778CrossRefGoogle Scholar
  57. Stern RJ (1994) Arc assembly and continental collision in the Neoproterozoic East African Orogen: implications for the consolidation of Gondwanaland. Annu Rev Earth Planet Sci 22:319–351Google Scholar
  58. Stern RJ (2002) Crustal evolution in the East African Orogen: a neodymium isotopic perspective. J Afr Earth Sci 34:109–117CrossRefGoogle Scholar
  59. Stern RJ (2008) Neoproterozoic crustal growth: the solid earth system during a critical time of earth history. Gondwana Res 14:33–50CrossRefGoogle Scholar
  60. Stern RJ, Kröner A (1993) Late Precambrian crustal evolution in NE Sudan: isotopic and geochronologic constraints. J Geol 101:555–574CrossRefGoogle Scholar
  61. Stern RJ, Avigad D, Miller NR, Beyth M (2006) Evidence for the Snowball Earth hypothesis in the Arabian–Nubian Shield and the East African Orogen. J Afr Earth Sci 44:1–20CrossRefGoogle Scholar
  62. Sultan M, Tucker RD, El Alfy Z, Attia R, Ragab AG (1994) U–Pb (zircon) ages for the gneissic terrane west of the Nile, southern Egypt. Int J Earth Sci 83:514–522Google Scholar
  63. Sun SS, McDonough WF (1989) Chemical and isotopic systematic of oceanic basalts: implications for mantle composition and processes. In: Saunders AD, Norry MJ (eds) Magmatism in the ocean basins, Geological Society special publication 42. Blackwell Scientific publishing, London, pp 313–345, 398Google Scholar
  64. Tadesse G, Allen A (2004) Geochemistry of metavolcanics from the Neoproterozoic Tuludimtu orogenic belt, Western Ethiopia. J Afr Earth Sci 39:177–185CrossRefGoogle Scholar
  65. Tadesse G, Allen A (2005) Geology and geochemistry of Neoproterozoic Tuludimtu Ophiolite suite, Western Ethiopia. J Afr Earth Sci 41:192–211CrossRefGoogle Scholar
  66. Tefera M (1991) Geology of the Kurmuk and Asosa area. Ethiopian Institute of Geological Survey draft Rep 109, Addis Ababa, EthiopiaGoogle Scholar
  67. Tefera M, Berhe SM (1987) Geological map of Gore area (1:250, 000). Ethiopian Institute of Geological Survey, Addis Ababa, EthiopiaGoogle Scholar
  68. Tefera M, Cherenet T, Haro W (1996) Geological map of Ethiopia (1:2, 000, 000). Ethiopian Institute of Geological Survey, Addis Ababa, EthiopiaGoogle Scholar
  69. UNDP (1972) Mineral survey in two selected areas (Sidamo and Wellega) EthiopiaGoogle Scholar
  70. Vance D, Thirlwall M (2002) An assessment of mass discrimination in MC-ICP MS using Nd isotope. Chem Geol 185:227–240CrossRefGoogle Scholar
  71. White R, McKenzie DP (1989) Magmatism at rift zones: the generation ration of volcanic continental margins and flood basalts. J Geophys Res 94:7685–7729CrossRefGoogle Scholar
  72. Whitehouse M, Windley BF, Ba-Bttat MAO, Fanning CM, Rex DC (1998) Crustal evolution and terrane correlation in the eastern Arabian Shield, Yemen: geochronological constraints. J Geol Soc Lond 155:281–295CrossRefGoogle Scholar
  73. Williams IS (1998) U–Th–Pb geochronology by ion microprobe. Rev Econ Geol 7:1–35Google Scholar
  74. Williams IS, Claesson S (1987) Isotopic evidence for the Precambrian provenance and Caledonian metamorphism of high-grade paragneisses from the Seve Nappes, Scandinavian Caledonides. Contrib Mineral Petrol 97:205–217CrossRefGoogle Scholar
  75. Williams IS, Buick IS, Cartwright I (1996) An extended episode of early Mesoproterozoic metamorphic fluid flow in the Reynolds Range, central Australia. J Metamorph Geol 14:29–47CrossRefGoogle Scholar
  76. Woldemichael BW, Kimura J-I (2008a) Petrogenesis of the Bikilal-Ghimbi gabbro, Western Ethiopia. J Mineral Petrol Sci 103:23–46Google Scholar
  77. Woldemichael BW, Kimura J-I (2008b) Geochemistry of the Neoproterozoic Ghimbi-Nedjo mafic to intermediate intrusions: implications for magma genesis and tectonic setting of Neoproterozoic Western Ethiopia. Earth Sci 62:257–271Google Scholar

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Binyam W. Woldemichael
    • 1
    • 2
  • Jun-Ichi Kimura
    • 3
  • Daniel J. Dunkley
    • 4
  • Kenichiro Tani
    • 3
  • Hiroto Ohira
    • 1
  1. 1.Department of GeoscienceShimane UniversityMatsueJapan
  2. 2.Chesapeake CollegeWye MillsUSA
  3. 3.Institute for Research on Earth Evolution (IFREE)Japan Agency for Marine-Earth Science and Technology (JAMSTEC)YokosukaJapan
  4. 4.National Institute of Polar Research (NIPR)TokyoJapan

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