Genesis of Damaran Granites in the Light of Rb/Sr and δ18O Data

  • U. Haack
  • J. Hoefs
  • E. Gohn


The mean (87Sr/86Sr) and mean (87Rb/86Sr) ratios of the intrusive granites from the northern and southern parts of the Orogen’s Central Zone plot on straight lines. These are interpreted as areal isochrons indicating the time of last Sr isotope homogenization 526 and 571 Ma ago in the respective source rocks.

Initial (87Sr/86Sr) and mean (87Rb/86Sr) ratios of approximately coeval granites of the main magmatic pulses in the North (~470 Ma) and in the South (~520 Ma) line up along isochrons suggesting that in both cases ~60 Ma elapsed after the homogenization in the protolith before large scale intrusions took place.

The data require that the intrusions have preserved the Rb/Sr ratios of their source rocks permitting only very little assimilation or fractionation.

The source rocks in the North and South had rather unradiogenic Sr 526 and 571 Ma ago, respectively. At Ri ≤ 0.7066 all presently known Damaran metasediments and metavolcanics as well as the basement must be excluded as the protoliths. A hypothetical source with a large proportion of low (87Sr/86Sr) volcanic material is required. In the centre, on the other hand, the Sr isotope ratios are more radiogenic and derivation from common Damaran metasediments is a distinct possibility.

Suitable protoliths for the alaskites are neither the granitic basement nor the arkosic Etusis Formation nor metasediments of the Kuiseb Formation. Derivation from Khan Formation metasediments or acidic lavas like those of the Naaupoort type is suggested by the Rb/Sr data. Two red granites could also stem from such sources whereas a third one was perhaps produced from Etusis metasediments.

The total rock δ18O values show an usual spread from 7.1 to 15.2% , the majority being very heavy. This excludes granulites and requires sediments or heavily altered volcanics as source rocks. Granites from the centre could have been derived from Damaran metasediments. A plot of their δ18O vs. initial Sr isotope ratios has a very clear negative slope. No trend is visible for the southern granites. Of the northern granites the older group shows a negative, the younger group a positive correlation. This is interpreted as indicating mainly altered volcanics (perhaps spilites) for the older and mixture of volcanogenic and metasedimentary rocks as the source for the younger group. The high δ18O values show that the granites are crustal remelts. The plot for the non-granitic intrusives which are all older than 550 Ma has a positive slope with δ18O between 6.5 and 10.5%, indicating a mixture between unaltered mantle derived and crustal material.


Source Rock Central Zone Regional Metamorphism Southern Central Leucocratic Granite 
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  1. Ahrendt, H., Hunziker, J.C. & Weber K. (1978) Age and degree of metamorphism and time of nappe emplacement along the southern margin of the Damara Orogen/Namibia (South West Africa).– Geol. Rundschau 67, 719.CrossRefGoogle Scholar
  2. Allsopp, H.L., & Ferguson, J. (1970) Measurements relating to the genesis of the Tsumeb pipe, South West Africa.– Earth Planet. Sci. Lett. 9, 448.CrossRefGoogle Scholar
  3. Baier, B., Eerckhemer, H., Gajewski, D., Green, R., Grimsel, C., Prodehl, G. and Vees, R. (1982) Deep seismic sounding in the area of the Damara Orogen (Namibia) This vol.Google Scholar
  4. Barnes, S.J. & Sawyer, E.W. (1980) An alternative model for the Damara mobile belt: ocean crust subduction and continental convergence.– Precambrian Research 13, 297.CrossRefGoogle Scholar
  5. Blaxland, A., Gohn, E., Haack, U. & Hoffer, E. (1979) Rb/Sr ages of late-tectonic granites in the Damara Orogen, Southwest Africa/Namibia.– N. Jb. Miner. Mh. 1979, 498.Google Scholar
  6. Erewer, M.S. & Lippolt, H.J. (1974) Petrogenesis of basement rocks of the upper Rhine region elucidated by rubidium-strontium systematics.– Contrib. Mineral. Petrol. 45, 123.CrossRefGoogle Scholar
  7. Briqueu, L. Lancelot, J.R., Valois, J.P. & Walgenwitz, F. (1980) U-Pb et genèse d’un type de minéralisation uranifère: les alaskites de Goanikontes (Namibie) et leur encaissant.– Bull. Cent. Rech. Fxplor. Prod. Elf Aquitaine, 4, 759.Google Scholar
  8. Brooks, C., James, D.E. & Hart, S.R. (1976) Ancient lithosphere: Its role in young continental volcanism.– Science 193, 1086.Google Scholar
  9. Purger, A.J. & Walraven, F. (1974) Summary of age determinations carried out during the period April 1975 to March 1976.– Ann. Geol. Surv. S. Afr. 11, 173.Google Scholar
  10. Chappell, B.W. & White, A.J.R. (1974) Two contrasting granite types.– Pacific Geology 8, 173.Google Scholar
  11. Clauer, N. & Kröner, A. (1979) Sr and Ar isotopic homogenization of pelitic sediments during low-grade regional metamorphism. The Pan-African upper Damaran sequence of northern Namibia (South West Africa).– Earth Planet. Sci. Lett. 43, 117.CrossRefGoogle Scholar
  12. Clayton, R.N. & Mayeda, T.K. (1963) The use of bromine pentafluoride in the extraction of oxygen from oxides and silicates for isotopic analysis.– Geochim. Cosmochim. Acta 27, 43.CrossRefGoogle Scholar
  13. Clifford, T.N., Rooke, J. M. & Allsopp, H. L. (1969) Petrochemistry and age of the Franzfontein granitic rocks of northern South West Africa.– Geochim. Cosmochim. Acta 33, 973.CrossRefGoogle Scholar
  14. Cook, F.A., Brown, L.D. & Oliver, J.E. (1980) The southern Appalachians and the growth of the continents.– Sci. Amer. 243,124.CrossRefGoogle Scholar
  15. Cortecci, G. Del Moro, A., Leone, G. & Pardini, G.C. (1979) Correlation between strontium and oxygen isotopic compositions of rocks from the Adamello massif (Northern Italy).– Contr. Mineral. Petrol. 68, 421.CrossRefGoogle Scholar
  16. Downing, K.N. & Coward, M.P. (1982) The Okahandja Lineament and its significance for Dmaran tectonics in Namibia.– Geol. Rdsch., 70, 972.CrossRefGoogle Scholar
  17. Faupel, J. (.1974) Geologisch-mineralogische Untersuchungen am Donkerhoek-Granit (Karibib-District, Südwestafrika).– Göttinger Arb. Geol. Paläont. 15, 95 pp.Google Scholar
  18. Faure, G. & Powell, J.L. (1972) Strontium isotope geology.– Springer.Google Scholar
  19. Finnemore S.H. (1978) The geochemistry and origin of the Matchless amphibolite belt, Windhoek district, South West Africa.– In: Mineralization in metamorphic terranes (W. J. Verwoerd, ed.) Geol. Soc. S. Afr. Spec. Publ. 4, 433.Google Scholar
  20. Fourcade, S. & Javoy, M. (1973) Rapport 18O/16O dans les roches du vieux socle catazonal d’In Ouzzal (Sahara Algerien).– Contr. Mineral. Petrol. 42, 235.CrossRefGoogle Scholar
  21. Haack, U. (1976) Rekonstruktion der Abkühlungsgeschichte des Damara-Orogens in Südwest- Afrika mit Hilfe von Spaltspuren-Altern. – Geol. Rundschau 65, 967.CrossRefGoogle Scholar
  22. Haack, U. & Gohn, E. (1979) Pb/Sr geochronology in the central Damara Orogen, Sw-Africa/Namibia.– Abstr. ECOG VI, 6th European Colloquium on Geochronology, Cosmochronology and Isotope Geology, Lillehammer, 39.Google Scholar
  23. Haack, U. Gohn, E. & Hartmann, O. (1982) Radiogenic heat production in Damaran rocks.– In: Geodynamic evolution of the Damara Orogen South West Africa/Namibia (R. McG. Miller, ed.) Geol. Soc. S. Afr. Spec. Publ., in press.Google Scholar
  24. Haack, U. Hoefs, J. & Gohn, E. (1982) Constraints on the origin of Damaran granites by Rb/Sr andö180 data.– Contr. Mineral. Petrol., 79, 279.CrossRefGoogle Scholar
  25. Haack, U., Gohn, E. & Klein, J.A. (1980) Rb/Sr ages of granitic rocks along the middle reaches of the Omaruru river and the timing of orogenetic events in the Damara Belt (Namibia).– Contr. Mineral. Petrol. 74, 349.CrossRefGoogle Scholar
  26. Halliday, A.N., Stephens, W.E. & Harmon, R.S. (1980) Rb-Sr and 0 isotopic relationships in 3 zoned Caledonian granitic plutons, Southern Uplands, Scotland: evidence for varied sources and hybridization of. magmas.– J. Geol. Soc. London 137, 329.CrossRefGoogle Scholar
  27. Hanson, G.N. (1978) The application of trace elements to the petrogenesis of igneous rocks of granitic composition.– Earth Planet. Sci. Lett. 38, 26.CrossRefGoogle Scholar
  28. Harmon, R.S. & Halliday, A.N. (1980) Oxygen and strontium isotope relationship in the British Caledonian granites.– Nature 283, 21.CrossRefGoogle Scholar
  29. Hartmann, O., Hoffer, E. & Haack, U. (1983) Crustal radioactivity and motion as causes of regional metamorphism in the Damara OrogenThis vol.Google Scholar
  30. Hawkesworth, C. J., Gledhill, A. R., Roddick, J. C., Miller, R.McG. & Kroner, A. (1982) Rb/Sr and l4Ar/39Ar studies bearing on models for the thermal evolution of the Damaran belt, Namibia.– In: Evolution of the Damara Orogen, South West Africa/Namibia (R.McG. Miller, ed.) Geol. Soc. S. Afr. Spec. Publ., in press.Google Scholar
  31. Hawkesworth, C.J., Kramers, J.D. & Miller, R.McG. (1981) Old model Nd ages in Namibian Pan-African rocks.– Nature 289, 278.CrossRefGoogle Scholar
  32. Hawkesworth, C.J. & Marlow, A. (1982) Isotope evolution of the Damara orogenic belt.– In: Geodynamic Evolution of the Damara Orogen, South West Africa/Namibia (R. McG. Miller, ed.) Geol. Soc. S. Afr. Spec.Publ., in press.Google Scholar
  33. Hoffer, E. (1977) Petrologische Untersuchungen zur Regionalmetamorphose Al-reicher Metapelite im siidlichen Damara-Orogen (Siidwest Afrika).– Habilitationsschrift, Gottingen.Google Scholar
  34. Hugo, P. & Schalk, K.E.L. (1973) The isotopic age of certain granites and acid lavas in the Rehoboth and Maltahohe districts, South West Africa.– Ann. Geol. Surv. S. Afr. 9, 103.Google Scholar
  35. Jacob, R.E. (1974) Geology and metamorphic petrology of part of the Damra Orogen along the lower Swakop river, South West Africa.– Bull. Precam. Res. Unit. Univ. Cape Town 17, 201 pp.Google Scholar
  36. Jacob, R.E. (1978) Granite genesis and related mineralization in part of the central Damara belt.– In: Mineralization in metamorphic terranes (W.J. Verwoerd, ed.) Geol. Soc. S. Afr. Spec. Publ, 4, 417.Google Scholar
  37. Jacob, R.E., Kroner, A. & Burger, A.J. (1978) Areal extent and first U-Pb age of the Pre-Damara Abbabis complex in the central Damara belt of South West Africa (Namibia).– Geol. Rdsch., 67, 706.CrossRefGoogle Scholar
  38. Kohler, H. & Miiller-Sohnius, D. (1979) Rb-Sr systematics on paragneiss series from the Moldanubicum (Eavaria, W.Germany).– Abstr. ECOG VI, 6th European Colloquium on Geochronology, Cosmochronology and Isotope Geology, Lillehammer, 61.Google Scholar
  39. Köhler, H. & Miiller-Sohnius, D. (1980) Rb-Sr systematics on parageneiss series from the Bavarian Moldanubicum, Germany.– Contr. Mineral. Petrol. 71, 387.CrossRefGoogle Scholar
  40. Kröner (1979) written communicationGoogle Scholar
  41. Kröner, A. (1982) Rb-Sr geochronology and tectonic evolution of the Pan-African Damara Belt of Namibia, South-West Africa.– Amer. J. Sci,, in press.Google Scholar
  42. Kröner, A., Halpern, M. & Jacob, R.E. (1978) Rb/Sr geochronology in favour of polymetamorphism in the Panafrican Damara Eelt of Namibia (South West Africa).– Geol. Rdsch., 67, 688.CrossRefGoogle Scholar
  43. Kröner, A. & Hawkesworth, C. (1977) Late Pan-African emplacement ages for Rössing alaskitic granite (Damara Belt) and Rooi Lepel bostonite (Gariep Belt) in Namibia and their significance for the timing of metamorphic events.– Report Res. Inst. Afr. Geol. Univ. Leeds 20, 14.Google Scholar
  44. Kröner, A. & Welin, E. (1973) Evidence for a 500 my old thermal episode in South-West Africa.– Earth Planet. Sci. Lett. 21, 149.CrossRefGoogle Scholar
  45. Falling, S. (1978) Some aspects of the lithostratigraphic and tectono-metamorphic evolution in the Nauchas-Rehoboth area, S.W.A. (Namibia).– Univ. Cape Town, Precam. Res. Unit., Ann. Rep. 14/15, 183.Google Scholar
  46. Marlow, A.G. (1982) Geology and Rb/Sr geochronology of mineralized and radioactive granites and alaskites, Namibia.– preprint.Google Scholar
  47. Martin, H. (1983)Overview of the geosynclinal, structural and metamorphic development of the intracontinental branch of the Damara Orogen.– This vol.Google Scholar
  48. Martin, H. (1983) Alternative geodynamic models for the Damara Orogen. A critical discussion.– This vol.Google Scholar
  49. Martin, H. & Porada, H. (1977a) The intracratonic branch of the Damara Orogen in South Wst Africa. I. Discussion of geodynamic models.– Precambrian Research 5, 311.Google Scholar
  50. Martin, H. & Porada, H. (1977b) The intracratonic branch of the Damara Orogen in South West Africa. II. Discussion of relationship with the Pan African mobile system.– Precambrian Research 5, 339.Google Scholar
  51. Masi, U., O’Neil, J.R. & Kistler, R.N. (1981) Stable isotope systematics in Mesozoic granites of central and northern California and southwestern Oregon.– Contr. Mineral. Petrol. 76, 116.CrossRefGoogle Scholar
  52. McCulloch, M.T., Gregory, R.T., Wasserburg, G.J. & Taylor, jr., H.P. (1981) Sm-Nd, Rb-Sr, and 180/160 isotopic systematics in an oceanic crustal section: Evidence from the Samail Ophiolite.– J. Geophys. Res. 86, 2721.CrossRefGoogle Scholar
  53. Michard-Vitrac, A., Albarlde, F., Dupuis, C. & Taylor, jr., H.P. (1980) The genesis of Variscan (Hercynian) plutonic rocks. Inferences from Sr, Pb and O studies on the Maladeta igneous complex, Central Pyrenees, (Spain).– Contr. Mineral. Petrol. 72, 57.CrossRefGoogle Scholar
  54. Miller, R.McG. (1973) The Salem granite suite, South West Africa: Genesis by partial melting of Khomas schist.– Memoir 64, Geol. Surv., Dept. of Mines, Petroria.Google Scholar
  55. Miller, R.McG. (1979) The Okahandja Lineament, a fundamental tectonic boundary in the Damara Orogen of South West Africa/Namibia.– Trans. Geol. Soc. S. Afr. 82, 349.Google Scholar
  56. Nieberding, F. (1976) Die Grenze der zentralen Granitzone südwestlich Otjimbingwe (Karibib-District, Südwestafrika): Intrusionsverband, Tektonik, Petrographie.– Göttinger Arb. Geol. Paläontol. 19, 78 pp.Google Scholar
  57. O’Neil, J.R. & Chappell, B.W. (1977) Oxygen and hydrogen isotope relations in the Eerridale batholith, Southwestern Australia.– J. Geol. Soc. Lond. 133, 559.CrossRefGoogle Scholar
  58. O’Neil, J.R., Shaw, S.E. & Flood, R.H. (1977) Oxygen and hydrogen isotope compositions as indicators of granite genesis in the New England batholith, Australia.– Contr. Mineral. Petrol. 62, 313.CrossRefGoogle Scholar
  59. Puhan, D. (1979) Petrologische und thermometrische Untersuchungen an Dolomit-Calcit-Marmoren des zentralen Damara-Orogens.– Habilitationsschrift Göttingen.Google Scholar
  60. Roddick, J. C. & Compston, W. (1977) Strontium isotopic equilibration: a solution to a paradox.– Earth Planet. Sci. Lett. 34, 238.CrossRefGoogle Scholar
  61. Sawyer, E.W. (1978) Damarant structural and metamorphic geology of an area Southwest of Walvis Bay, S.W. Africa/Namibia.– M. Sci. thesis, Univ. of Cape Town, 205 pp.Google Scholar
  62. Schmidt, A. (1982) Geochemische Untersuchungen an Graniten des Damara Orogens, Namibia.– Dissertation Gottingen.Google Scholar
  63. Schmidt, A. & Wedepohl, K.H. (1982) Chemical composition and genetic relations of the Matchless amphibolite (Damara Orogenic Belt) Geodynamic Evolution of the Damara Orogen.– Spec. Publ. Geol. Soc. S. Afr., in press.Google Scholar
  64. Smith, D.A.M. (1965) The geology of the area around the Khan and Swakop rivers West Africa.– Geol. Surv. S. Afr., Mem. 3 (S.W.A. Series), 113pp.Google Scholar
  65. Streckeisen, A. (1976) To each plutonic rock its proper name.– Earth Sci. Rev. 12, 1.CrossRefGoogle Scholar
  66. Taylor, H.P. (1966) The oxygen isotope geochemistry of Petrol. 19, 1.Google Scholar
  67. Taylor, H.P. (1977) Water rock interactions and the origin of H2.0 in granitic batholiths.– J. Geol. Soc..133, 509.CrossRefGoogle Scholar
  68. Taylor, H.P. (1978) Oxygen and hydrogen isotope studies of plutonic granitic rocks.– Earth Planet. Sci. Lett. 38, 177.CrossRefGoogle Scholar
  69. Taylor, H.P. & Silver, L.T. (1978) Oxygen isotope relationship in plutonic igneous rocks of the Peninsular Ranges batholith, Southern and Eaja California.– Short papers of the 4th International Conference on Geochronology, Cosmochronology and Isotope Geology, Report 78–701, 423.Google Scholar
  70. Veizer, J. & Hoefs, J. (1976) The nature of 180/lb0 and 13C/12C carbonate rocks.– Geochim. Cosmochim/Acta 40, 1387.CrossRefGoogle Scholar
  71. Watters, B.R. (1976) Possible late Precambrian subduction zone in South Nature 259, 471.Google Scholar
  72. Wedepohl, K.H., Meyer, K. & Muecke, G.K. (1983) Chemical composition and genetic relations of meta-volcanic rocks from the Rhenohercynian Belt of Northern Germany.– This vol.Google Scholar
  73. Wilson, A.E., Green, D.C. & Davidson, L.R. (1970) The use of oxygen isotope geochemistry on granulites and related intrusions, Musgrave Ranges, Central Australia.– Contr. Mineral. Petrol. 27, 166.CrossRefGoogle Scholar
  74. Winkler, H.G.F. (1983) A survey of granitic rocks of the Damara Orogen and considerations on their genesis.– This vol.Google Scholar
  75. Zwart, H.J. (1968) Metamorphic facies series in the European orogenic belts and their bearing on the cause of orogeny.– Spec. Pap. Geol. Assoc. Canada 5, 7.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1983

Authors and Affiliations

  • U. Haack
    • 1
  • J. Hoefs
    • 1
  • E. Gohn
    • 1
  1. 1.Geochemisches InstitutGöttingenGermany

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