Skip to main content
SpringerLink
Log in

The Kenticha rare-element pegmatite, Ethiopia: internal differentiation, U–Pb age and Ta mineralization

  • Article
  • Published:
Mineralium Deposita Aims and scope Submit manuscript

Abstract

The Kenticha rare-element pegmatite, a globally important tantalite source in the Neoproterozoic Adola Belt of southern Ethiopia, is a highly fractionated, huge (2,000 m long and up to 100 m thick), subhorizontal, sheet-like body, discordantly emplaced in ultramafic host rock. It corresponds to the spodumene subtype of the rare-element pegmatite class and belongs to the lithium–cesium–tantalum petrogenetic family. The Kenticha pegmatite is asymmetrically zoned from bottom to top into granitic lower zone, spodumene-free intermediate zone, and spodumene-bearing upper zone. A monomineralic quartz unit is discontinuously developed within the upper zone. Whole-rock data indicate an internal geochemical differentiation of the pegmatite sheet proceeding from the lower zone (K/Rb ~36, K/Cs ~440, Al/Ga ~2,060, Nb/Ta ~2.6) to the upper zone (K/Rb ~19, K/Cs ~96, Al/Ga ~1,600, Nb/Ta ~0.7). The latter one is strongly enriched in Li2O (up to 3.21%), Rb (up to 4,570 ppm), Cs (up to 730 ppm), Ga (up to 71 ppm), and Ta (up to 554 ppm). Similar trends of increasing fractionation from lower zone to upper zone were obtained in muscovite (K/Rb 23–14, K/Cs 580–290, K/Tl 6,790–3,730, Fe/Mn 19–10, Nb/Ta 6.5–3.8) and columbite–tantalite (Mn/Mn + Fe 0.4–1, Ta/Ta + Nb 0.1–0.9). The bottom-to-top differentiation of the Kenticha pegmatite and the Ta mineralization in its upper part are principally attributed to upward in situ fractionation of a residual leucogranitic to pegmatitic melt, largely under closed system conditions. High MgO contents (up to 5.05%) in parts of the upper zone are the result of postmagmatic hydrothermal alteration and contamination by hanging wall serpentinite. U–Pb dating of Mn-tantalite from two zones of the Kenticha pegmatite gave ages of 530.2 ± 1.3 and 530.0 ± 2.3 Ma. Mn-tantalite from the Bupo pegmatite, situated 9 km north of Kenticha, gave an age of 529.2 ± 4.1 Ma, indicating coeval emplacement of the two pegmatites. The emplacement of the pegmatites is temporally related to postorogenic granite magmatism, producing slightly peraluminous, I-type plutons in the area surrounding the Kenticha pegmatite field. Fractionated members of this suite might be envisaged as potential parental magmas.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14

Similar content being viewed by others

References

  • Abraham A, Hassen N, Yemane T, Genzebu W, Seyid G, Mehari K, Alemu T (1992) The geological evolution of the proterozoic of southern Ethiopia. Abstr Vol 29th Intern Geological Congress, Kyoto, Japan, p 13

  • Asrat A, Barbey P (2003) Petrology, geochronology and Sr–Nd isotopic geochemistry of the Konso pluton, south-western Ethiopia: implications for transition from convergence to extension in the Mozambique Belt. Int J Earth Sci (Geol Rundsch) 92:873–890

    Article  Google Scholar 

  • Baker DR (1998) The escape of pegmatite dikes from granitic plutons: constraints from new models of viscosity and dike propagation. Can Mineral 36:255–263

    Google Scholar 

  • Baumgartner R, Romer RL, Moritz R, Sallet R, Chiaradia M (2006) Columbite–tantalite bearing granitic pegmatites from the Seridó Belt, northeastern Brazil: genetic constraints from U–Pb dating and Pb isotopes. Can Mineral 44:69–86

    Article  Google Scholar 

  • Beraki WH, Bonavia FF, Getachew T, Schmerhold R, Tarekegn T (1989) The Adola Fold and Thrust Belt, southern Ethiopia: a re-examination with implications for Pan-African evolution. Geol Mag 126:647–657

    Article  Google Scholar 

  • Beus AA (1966) Distribution of tantalum and niobium in muscovites from granitic pegmatites. Geokhimiya 10:1216–1220, in Russian

    Google Scholar 

  • Brisbin WC (1986) Mechanics of pegmatite intrusion. Am Mineral 71:644–651

    Google Scholar 

  • Černý P (1989) Contrasting geochemistry of two pegmatite fields in Manitoba: products of juvenile Aphebian crust and polycyclic Archean evolution. Precambr Res 45:215–234

    Article  Google Scholar 

  • Černý P (1991) Rare-element granitic pegmatites. Part I: anatomy and internal evolution of pegmatite deposits. Geosci Can 18:49–67

    Google Scholar 

  • Černý P (1992) Geochemical and petrogenetic features of mineralization in rare-element granitic pegmatites in the light of current research. Appl Geochem 7:393–416

    Article  Google Scholar 

  • Černý P (2005) The tanco rare-element pegmatite deposit, Manitoba: regional context, internal anatomy, and global comparisons. In: Linnen RL, Samson IM (eds) Rare element geochemistry and mineral deposits. Geol. Assoc. Canada (GAC) short course notes 17. Geological Association of Canada, Toronto, ON, pp 127–158

    Google Scholar 

  • Černý P, Ercit TS (2005) The classification of granitic pegmatites revisited. Can Mineral 43:2005–2026

    Article  Google Scholar 

  • Černý P, Meintzer RE, Anderson AJ (1985) Extreme fractionation in rare-element granitic pegmatites: selected examples of data and mechanisms. Can Mineral 23:381–421

    Google Scholar 

  • Černý P, Blevin PL, Cuney M, London D (2005) Granite-related ore deposits. Econ Geol 100:337–370

    Google Scholar 

  • Černý P, Ercit TS, Smeds S-A, Groat LA, Chapman R (2007) Zirconium and hafnium in minerals of the columbite and wodginite groups from granitic pegmatites. Can Mineral 45:185–202

    Article  Google Scholar 

  • Clarke DB (1992) Granitoid rocks. Topics in earth sciences 7. Chapman & Hall, London, 283p

    Google Scholar 

  • Dawei H, Shiguang W, Xilin X, Jisheng Z, Tao W (2003) Metallogenetic province derived from mantle sources: Nd, Sr, S, Pb isotope evidence from the Central Asian Orogenic Belt. Gondwana Res 6:711–728

    Article  Google Scholar 

  • Emelyanov EL, Abebaw T, Tesfaye T, Teweldemedhin T (1986) Preliminary report on prospecting results of the Kenticha rare metal deposit.—Internal report (unpubl) Ethiopian Mineral Resource Development Corp, Ministry of Mines and Energy, Addis Ababa

  • Genna A, Nehlig P, Le Goff E, Guerrot C, Shanti M (2002) Proterozoic tectonism of the Arabian Shield. Precambr Res 117:21–40

    Article  Google Scholar 

  • Genzebu W, Hassen N, Yemane T (1994) Geology of the Agere Mariam area. Ethiopian Institute of Geological Surveys, memoir 8. Ethiopian Institute of Geological Surveys, Addis Ababa, 23p

    Google Scholar 

  • Gerstenberger H, Haase G (1997) A highly effective emitter substance for mass spectrometric Pb isotope ratio determinations. Chem Geol 136:309–312

    Article  Google Scholar 

  • Gichile S (1991) Structure, metamorphism and tectonic setting of a gneissic terrane, the Sagan-Aflata area, southern Ethiopia. Unpubl MSc thesis, University of Ottawa, Canada, 225p

  • Gordiyenko VV (1971) Concentration of Li, Rb and Cs in potash feldspar and muscovite as criteria for assessing the rare metal mineralization in granitic pegmatites. Int Geol Rev 13:134–142

    Article  Google Scholar 

  • 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, Windley BE, Dasgupta S (eds) Proterozoic East Gondwana: supercontinent assembly and breakup. Geological Society of London special publication 206. Geological Society of London, London, pp 289–325

    Google Scholar 

  • Kozyrev V, Girma K, Bekele WM, Teweldemedhin T (1982) Regional geological and exploration work for gold and other minerals in the Adola gold fields.—Internal report (unpubl) Ethiopian Mineral Resource Development Corp, Ministry of Mines and Energy, Addis Ababa, 260p

  • Kozyrev V, Girma K, Safonov J, Tuliankin V, Bekele WM, Bestujev A, Darijapov A, Teweldemedhin T, Gurbanivich G, Kaitukov M, Arijapov A (1988) Geological map of the Adola Region, 1:100000. Ethiopian Mapping Agency, Addis Ababa

    Google Scholar 

  • Küster D (2009) Granitoid-hosted Ta mineralization in the Arabian–Nubian Shield: ore deposit types, tectono-metallogenetic setting and petrogenetic framework. Ore Geol Rev 35:68–86

    Article  Google Scholar 

  • Lagache M, Quéméneur J (1997) The Volta Grande pegmatites, Minas Gerais, Brazil: an example of rare-element granitic pegmatites exceptionally enriched in lithium and rubidium. Can Mineral 35:153–165

    Google Scholar 

  • Lenoir JL, Küster D, Liégeois JP, Utke A, Haider A, Matheis G (1994) Origin and regional significance of Late Precambrian and Early Paleozoic granitoids in the Pan-African belt of Somalia. Geol Rundsch 83:624–641

    Article  Google Scholar 

  • Linnen RL, Cuney M (2005) Granite-related rare-element deposits and experimental constraints on Ta–Nb–W–Sn–Zr–Hf mineralization. In: Linnen RL, Samson IM (eds) Rare element geochemistry and mineral deposits. Geol Assoc Canada (GAC) short course notes 17. Geological Association of Canada, Toronto, On, pp 45–68

    Google Scholar 

  • London D (2005a) Geochemistry of alkalis and alkaline earths in ore-forming granites, pegmatites, and rhyolites. In: Linnen RL, Samson IM (eds) Rare element geochemistry and mineral deposits. Geol Assoc Canada (GAC) short course notes 17. Geological Association of Canada, Toronto, On, pp 17–43

    Google Scholar 

  • London D (2005b) Granitic pegmatites: an assessment of current concepts and directions for the future. Lithos 80:281–303

    Article  Google Scholar 

  • London D (2008) Pegmatites. Can Mineral Spec Publ 10:347

    Google Scholar 

  • Lu HZ, Wang ZG, Li YS (1997) Magma-fluid transition and the genesis of pegmatite dike No.3, Altay, Xinjiang, northwest China. Chin J Geochem 16:43–52

    Article  Google Scholar 

  • McDonough WF, Sus S-s (2005) The composition of the earth. Chem Geol 120:223–253

    Article  Google Scholar 

  • Morgan GBVI, London D (1999) Crystallization of the little three layered pegmatite–aplite dike, Ramona District, California. Contrib Mineral Petrol 136:310–330

    Article  Google Scholar 

  • Norton JJ (1983) Sequence of mineral assemblages in differentiated granitic pegmatites. Econ Geol 78(854–87):4

    Google Scholar 

  • Partington GA, McNaughton NJ, Williams IS (1995) A review of the geology, mineralization, and geochronology of the Greenbushes pegmatite, Western Australia. Econ Geol 90:616–635

    Article  Google Scholar 

  • Poletayev JA, Verbvsky ON, Teweldemedhin T, Musa E, Alemayehu B, Manaye Y (1991) The geology and rare metal potential of the Kenticha pegmatite deposit. Internal report (unpubl) Ethiopian Mineral Resource Development Corp, Ministry of Mines and Energy, Addis Ababa, 113p

  • Quéméneur J, Lagache M (1999) Comparative study of two pegmatitic fields from Minas Gerais, Brazil, using Rb and Cs contents of micas and feldspars. Rev Brasil Geociências 29:27–32

    Google Scholar 

  • Roda E, Pesquera A, Gil-Crespo PP, Torres-Ruiz J, Fontan F (2005) Origin and internal evolution of the Li–F–Be–B–P-bearing Pinilla de Fermoselle pegmatite (Central Iberian Zone, Zamora, Spain). Am Mineral 90:1887–1899

    Article  Google Scholar 

  • Roda E, Pesquera A, Gil-Crespo PP, Torres-Ruiz J, De Parseval P (2006) Mineralogy and geochemistry of micas from the Pinilla de Fermoselle pegmatite (Zamora, Spain). Eur J Mineral 18:369–377

    Article  Google Scholar 

  • Romer RL (2003) Alpha-recoil in U–Pb geochronology: effective sample size matters. Contrib Mineral Petrol 145:481–491

    Article  Google Scholar 

  • Romer RL, Smeds SA (1996) U–Pb columbite ages of pegmatites from Sveconorwegian terranes in southwestern Sweden. Precambr Res 76:15–30

    Article  Google Scholar 

  • Romer RL, Smeds SA (1997) U–Pb columbite chronology of post-kinematic Palaeoproterozoic pegmatites in Sweden. Precambrian Res 82:85–99

    Article  Google Scholar 

  • Romer RL, Wright JE (1992) U–Pb dating of columbites: a geochronologic tool to date magmatism, metamorphism, and ore deposits. Geochim Cosmochim Acta 56:2137–2142

    Article  Google Scholar 

  • Smith SR, Foster GL, Romer RL, Tindle AG, Kelley SP, Noble SR, Horstwood M, Breaks FW (2004) U–Pb columbite–tantalite chronology of rare-element pegmatites using TIMS and laser ablation-multi collector-ICP-MS. Contrib Mineral Petrol 147:549–654

    Article  Google Scholar 

  • Steiger RH, Jäger E (1977) Subcommission on geochronology: convention on the use of decay constants in geo- nad cosmochronology. Earth Planet Sci Letters 36:359–362

    Article  Google Scholar 

  • Stern RJ (1994) Neoproterozoic (900–550 Ma) arc assembly and continental collision in the East African Orogen: implications for consolidation of Gondwanaland. Ann Rev Earth Planet Sci 22:319–351

    Google Scholar 

  • Stilling A, Černý P, Vanstone PJ (2006) The Tanco Pegmatite at Bernic Lake, Manitoba. XVI. Zonal and bulk composition and their petrogenetic significance. Can Mineral 44:599–623

    Article  Google Scholar 

  • Stoeser DB, Camp VE (1985) Pan-African microplate accretion in the Arabian Shield. Geol Soc Am Bull 96:817–826

    Article  Google Scholar 

  • Sweetapple MT, Collins PLF (2002) Genetic framework for the classification of Archean rare metal pegmatites in the North Pilbara Craton, Western Australia. Econ Geol 97:873–895

    Article  Google Scholar 

  • Tadesse S, Zerihun D (1996) Composition, fractionation trend and zoning accretion of the columbite–tantalite group of minerals in the Kenticha rare metal field (Adola, southern Ethiopia). J Afr Earth Sci 23:411–431

    Article  Google Scholar 

  • Teklay M, Kröner A, Mezger K, Oberhänsli R (1998) Geochemistry, Pb–Pb single zircon ages and Nd–Sr isotope composition of Precambrian rocks from southern and eastern Ethiopia: implications for crustal evolution in East Africa. J Afr Earth Sci 26:207–227

    Article  Google Scholar 

  • Tsige L (2006) Metamorphism and gold mineralization of the Kenticha–Katawicha area, Adola Belt, southern Ethiopia. J Afr Earth Sci 45:16–23

    Article  Google Scholar 

  • Tsige L, Abdelsalam MG (2005) Neoproterozoic–early Phanerozoic gravitational tectonic collapse in the southern part of the Arabian Shield: the Bulbul Belt of southern Ethiopia. Precambr Res 138:297–318

    Article  Google Scholar 

  • Van Lichtervelde M, Salvi S, Béziat D, Linnen RL (2007) Textural features and chemical evolution in tantalum oxides: magmatic versus hydrothermal origins for Ta mineralization in the Tanco Lower pegmatite, Manitoba, Canada. Econ Geol 102:257–274

    Article  Google Scholar 

  • Wang T, Tong Y, Jahn BM, Zou TR, Wang YB, Hong DW, Han BF (2007) SHRIMP U–Pb zircon geochronology of the Altai No. 3 pegmatite, NW China, and its implications for the origin and tectonic setting of the pegmatite. Ore Geol Rev 32:325–336

    Article  Google Scholar 

  • Webber KL, Simmons WB, Falster AU, Foord FE (1999) Cooling rates and crystallization dynamics of shallow level pegmatite–aplite dikes, San Diego County, California. Am Mineral 84:708–717

    Google Scholar 

  • Worku H (1996) Geodynamic development of the Adola Belt (southern Ethiopia) in the Neoproterozoic and its control an gold mineralization. Ph.D. thesis, Tech Univ Berlin, 156p

  • Worku H, Schandelmeier H (1996) Tectonic evolution of the Neoproterozoic Adola Belt of southern Ethiopia: evidence for a Wilson Cycle process and implications for oblique plate collision. Precambr Res 77:179–210

    Article  Google Scholar 

  • Yibas B, Reimold WU, Armstrong R, Koeberl C, Anhaeusser CR, Phillips D (2002) The tectonostratigraphy, granitoid geochronology and geological evolution of the Precambrian of southern Ethiopia. J Afr Earth Sci 34:57–84

    Article  Google Scholar 

  • Yibas B, Reimold WU, Anhaeusser CR, Koeberl C (2003) Geochemistry of the mafic rocks of the ophioloitic fold and thrust belts of southern Ethiopia: constraints on the tectonic regime during the Neoproterozoic (900–700 Ma). Precambr Res 121:157–183

    Article  Google Scholar 

  • Yihunie T (2002) Pan-African deformation in the basement of the Negele area, southern Ethiopia. Int J Earth Sci (Geol Rundsch) 91:922–933

    Article  Google Scholar 

  • Yihunie T (2003) Chemical Th–U–total Pb isochron ages of zircon and monazite from granitic rocks of the Negele area, southern Ethiopia. J Earth Planet Sci Nagoya Univ 50:1–12

    Google Scholar 

  • Yihunie T, Adachi M, Takeuchi M (2004) P–T conditions of metamorphism of Neoproterozoic rocks of the Negele area, southern Ethiopia. Gondwana Res 7:489–500

    Article  Google Scholar 

  • Zerihun D (1991) Le mineralizzazioni a Ta-Nb: classificazione, prospezione, valutazione. Il caso di Kenticha (area di Adola, Sidamo—Ethiopia).—unpubl Ph.D. thesis, Univ of Milan, 365p

  • Zerihun D, Garbarino C, Valera R (1995) Granite pegmatite system in Kenticha (Adola, Sidamo, Ethiopia) rare metal pegmatite belt: petrochemistry, regional pegmatite zoning and classification. SINET Ethiopian J Sci 18:119–148

    Google Scholar 

Download references

Acknowledgments

The authors are grateful to the German Academic Exchange Service (DAAD) for granting a research fellowship to D. Küster at TU Berlin and a visiting scholarship to D. Tolessa at Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) in Hannover. The support of Mekelle University through a field research grant to D. Küster and K. Bheemalingeswara is much appreciated. We acknowledge the logistic support of the Geological Survey of Ethiopia and the Ethiopian Mineral Development Share Company, especially their crews at Kenticha Mine and Shakisso. We thank Dr. G. Matheis (TU Berlin) for his support and cooperation and P. Marsiske (TU Berlin) for XRF analysis. Thanks go also to the following persons at the BGR laboratories for their analytical input: P. Rendschmidt (polished and thin sections), F. Korte (XRF), H. Lorenz (ICP-MS), and J. Lodziak (electron microprobe). Marcus Sweetapple is thanked for his careful review and constructive comments. Finally, we are indebted to the Director of Ethiopian Mineral Development Share Company for his allowance to publish the data.

Author information

Author notes

  1. Dirk Küster

    Present address: Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655, Hannover, Germany

Authors and Affiliations

  1. Department of Applied Geology, Mekelle University, P.O. Box 231, Mekelle, Ethiopia

    Dirk Küster & K. Bheemalingeswara

  2. Institut für Angewandte Geowissenschaften, Technische Universität Berlin, FG Mineralogie-Petrologie Ackerstrasse 71–76, 13355, Berlin, Germany

    Dirk Küster

  3. GeoForschungsZentrum Potsdam, Telegrafenberg, 14473, Potsdam, Germany

    Rolf L. Romer

  4. Geological Survey of Ethiopia, P.O. Box 2302, Addis Ababa, Ethiopia

    Dandena Tolessa

  5. Ethiopian Mineral Development Share Company, P.O. Box 2543, Addis Ababa, Ethiopia

    Desta Zerihun

  6. Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655, Hannover, Germany

    Frank Melcher & Thomas Oberthür

Authors
  1. Dirk Küster
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Rolf L. Romer
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Dandena Tolessa
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Desta Zerihun
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. K. Bheemalingeswara
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Frank Melcher
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Thomas Oberthür
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Dirk Küster.

Additional information

Editorial handling: B. Lehmann

Rights and permissions

Reprints and permissions

About this article

Cite this article

Küster, D., Romer, R.L., Tolessa, D. et al. The Kenticha rare-element pegmatite, Ethiopia: internal differentiation, U–Pb age and Ta mineralization. Miner Deposita 44, 723–750 (2009). https://doi.org/10.1007/s00126-009-0240-8

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00126-009-0240-8

Keywords

Search

Navigation