Contributions to Mineralogy and Petrology

, Volume 94, Issue 4, pp 427–437 | Cite as

Four zircon ages from one rock: the history of a 3930 Ma-old granulite from Mount Sones, Enderby Land, Antarctica

  • L. P. Black
  • I. S. Williams
  • W. Compston


Ion microprobe U-Th-Pb analyses of zircons from a granulite-grade orthogneiss from Mount Sones, Enderby Land, Antarctica, record the ages of four principal events in the history of the gneiss, three of which already have been recognized through previous isotopic dating of other samples. The structure of the zircons indicates at least four different stages of growth. The several zircon ages were obtained by grouping the analyses according to the stage they represented in the observed “stratigraphic succession” of growth and thereby defining separate U-Pb discordance patterns for each stage. The stratigraphically oldest zircon (rare discrete cores) is indistinguishable in age from the most common, euhedrally zoned zircon. Both crystallized when the tonalitic precursor of the orthogneiss was emplaced into the crust 3927±10 Ma ago, making the orthogneiss currently the oldest known terrestrial rock. The outer parts of most grains and some whole grains recrystallized at 2948±31/−17 Ma, during or immediately after possibly ∼100 Ma of high granulite grade metamorphism. The recrystallized zircon was isotopically disturbed by tectonism associated with reactivation of the southern margin of the Napier Complex at ∼1000 Ma. In the intervening time, at 2479±23 Ma, the cores and zoned zircon suffered a major isotopic disturbance involving movement of radiogenic Pb which left most of the crystals with radiogenic Pb deficiencies, but produced local radiogenic Pb excesses in others. A new generation of zircon, characterized by very high Th/U and low U, grew at that time. That event — deformation and possibly a minor rise in temperature — produced widespread perturbations of other isotopic systems throughout the Napier Complex.


Zircon Outer Part Southern Margin Isotopic System Grade Metamorphism 
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  1. Black LP, James PR (1979) Preliminary isotopic ages from Ender by Land, Antarctica. Geol Soc Aus J 26:266–267 (Abstract)Google Scholar
  2. Black LP, James PR (1983) Geological history of the Archaean Napier complex of Enderby Land. In: Oliver RL, James PR, Jago JB (eds) Antarctic Geoscience. Australian Academy of Science Canberra, pp 11–15Google Scholar
  3. Black LP, James PR, Harley SL (1983a) The geochronology, structure and metamorphism of early Archaean rocks at Fyfe Hills, Enderby Land, Antarctica. Precamb Res 21:197–222Google Scholar
  4. Black LP, James PR, Harley SL (1983b) Geochronology and geological evolution of metamorphic rocks in the Field Islands area, East Antarctica. J Metamorphic Geol 1:277–303Google Scholar
  5. Black LP, Fitzgerald JD, Harley SL (1984) Pb isotopic composition, colour and microstructure of monazites from a polymetamorphic rock in Antarctica. Contrib Mineral Petrol 85:141–148Google Scholar
  6. Compston W, Williams IS, Meyer C (1984) U-Pb geochronology of zircons from lunar breccia 73217 using a sensitive high massresolution ion microprobe. Proc Lunar Planet Sci Conf 14th, J Geophys Res 89 [Suppl] B525–534Google Scholar
  7. Cumming GL, Richards JR (1975) Ore lead isotope ratios in a continuously changing earth. Earth Planet Sci Lett 28:155–171Google Scholar
  8. DePaolo DJ, Manton WI, Grew ES, Halpern M (1982) Sm-Nd, Rb-Sr and U-Th-Pb systematics of granulite facies rocks from Fyfe Hills, Enderby Land, Antarctica. Nature 298:614–618Google Scholar
  9. Grew ES (1978) Precambrian basement at Molodezhnaya station, East Antarctica. Bull Geol Soc Am 89:801–813Google Scholar
  10. Grew ES, Manton WI (1979) Archaean rocks in Antarctica: 2.5 billion year uranium lead ages of pegmatites in Enderby Land. Science 206:443–445Google Scholar
  11. Harley SL, Black LP (1986) The Archaean geological evolution of Enderby Land, Antarctica. In: Tarney J, Park RG (eds) Proceedings of conference on the evolution of the Lewisian and comparable Precambrian terrains. Leicester Univ, UKGoogle Scholar
  12. McCulloch MT, Black LP (1984) Sm-Nd isotopic systematics of Enderby Land granulites and evidence for redistribution of Sm and Nd during metamorphism. Earth Planet Sci Lett 71:46–58Google Scholar
  13. McIntyre GA, Brooks C, Compston W, Turek A (1966) The statistical assessment of Rb-Sr isochrons. J Geophys Res 71:5459–5468Google Scholar
  14. Rogers JJW, Adams JAS (1969) Uranium, Abundances in common igneous rocks. In: Wedepohl KH (ed) Handbook of Geochemistry. Springer, Berlin Heidelberg New York, pp 92-E-1–92-E-8Google Scholar
  15. Sheraton JW, Offe LA, Tingey RJ, Ellis DJ (1980) Enderby Land, Antarctica — an unusual Precambrian high-grade metamorphic terrain. J Geol Soc Aust 27:1–18Google Scholar
  16. Sheraton JW, Black LP (1983) Geochemistry of Precambrian gneisses: relevance for the evolution of the East Antarctic shield. Lithos 16:273–296Google Scholar
  17. Sheraton JW, Black LP, McCulloch MT (1984) Regional geochemical and isotopic characteristic of high-grade metamorphics of the Prydz Bay area: the extent of Proterozoic reworking of Archaean continental crust in East Antarctica. Precamb Res 26:169–198Google Scholar
  18. Silver LT, Williams IS, Woodhead JA (1980) Uranium in granites from the southwestern United States: Actinide parent-daughter systems, sites and mobilization. First year rept for Dept of Energy, DOE-GJBX-45(81), Calif Inst of Technology, pp 379Google Scholar
  19. Sobotovich EV, Kamenev YeN Komaristyy AA, Rudnick VA (1976) The oldest rocks of Antarctica (Enderby Land). Int Geol Rev 18:371–388Google Scholar
  20. Steiger RH, Jäger E (1977) Subcommission on Geochronology: convention on the use of decay constants in geoand cosmochronology. Earth Planet Sci Lett 36:359–362Google Scholar
  21. Williams IS, Compston W, Black LP, Ireland TR, Foster JJ (1984) Unsupported radiogenic Pb in zircon: a cause of anomalously high Pb-Pb, U-Pb and Th-Pb ages. Contrib Mineral Petrol 88:322–327Google Scholar

Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • L. P. Black
    • 1
  • I. S. Williams
    • 2
  • W. Compston
    • 2
  1. 1.Bureau of Mineral ResourcesCanberraAustralia
  2. 2.Research School of Earth SciencesAustralian National UniversityCanberraAustralia

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