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Contributions to Mineralogy and Petrology

, Volume 94, Issue 4, pp 438–451 | Cite as

Age and evolution of the Grenville Province in eastern Labrador from U-Pb systematics in accessory minerals

  • U. Schärer
  • T. E. Krogh
  • C. F. Gower
Article

Abstract

U-Pb isotope analysis of zircon, titanite, monazite and rutile extracted from 15 different Grenville Province rocks in eastern Labrador reveals: 1) major crust formation through magmatism between 1,710 and 1,630 Ma ago; no evidence of older crustal material was found. 2) Pegmatite and gabbro intrusions between 1,500 and 1,400 Ma ago, probably related to incomplete rifting of the earlier formed crust. 3) Granite and syenite plutonism, presumably anorogenic, circa 1,300 Ma ago. 4) High grade metamorphism and anatexis during the Grenvillian Orogeny, causing Pb-loss in primary zircon and new growth of zircon, titanite and monazite at circa 1,030 Ma ago in the south (Lake Melville and Mealy Mountains terranes) and circa 970 Ma ago in the north (Groswater Bay Terrane and Trans-Labrador Batholith); geochronological distinction of these large-scale crustal segments substantiates their juxtaposition along deeply rooted, intracontinental ductile thrust zones during Grenvillian Orogeny. 5) Late Grenvillian growth of rutile in gabbros circa 925 Ma ago.

Keywords

Zircon Rutile Isotope Analysis Titanite Accessory Mineral 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Blaxland AB, Curtis LW (1977) Chronology of the Red Wine alkaline province, central Labrador. Can J Earth Sci 14:1940–1946Google Scholar
  2. Davis DW (1982) Optimum linear regression and error estimation applied to U-Pb data. Can J Earth Sci 19:2141–2149Google Scholar
  3. Emslie RF, Loveridge WD, Stevens RD (1984) The Mealy dykes, Labrador: petrology, age, and tectonic significance. Can J Earth Sci 21:437–446Google Scholar
  4. Fahrig WF, Loveridge WD (1981) Rb-Sr study of the Michael gabbro, Labrador. In: Rb-Sr and U-Pb isotopic age studies, report 4. Current Res Part C Geol Surv Canada Pap 81–1C:991–1003Google Scholar
  5. Gower CF, Ryan AB, Bailey DG, Thomas A (1980) The position of the Grenville Front in eastern and central Labrador. Can J Earth Sci 17:784–788Google Scholar
  6. Gower CF (1981) The geology of the Benedict Mountains, Labrador [13 J northeast and 13 I northwest]. Department of Mines and Energy Newfoundland and Labrador Report 81-3:26pGoogle Scholar
  7. Gower CF (1984) Geology of the Double Mer White Hills and surrounding region, Grenville Province, eastern Labrador. Current Res Part A Geol Surv Canada Pap 84–1A:553–561Google Scholar
  8. Gower CF, Owen V (1984) Pre-Grenvillian and Grenvillian lithotectonic regions in eastern Labrador — correlation with the Sveconorwegian Orogenic Belt in Sweden. Can J Earth Sci 21:678–693Google Scholar
  9. Gower CF (1985) Correlation between the Grenville Province and Sveconorwegian orogenic belt — implication for Proterozoic evolution of the southern margin of the Canadian and Baltic Shields. In: Tobi AC, Touret JLR (ed) The deep Proterozoic crust in the North Atlantic Provinces. NATO ASI Series C158:247–257Google Scholar
  10. Gower CF, Ryan B (1986) Proterozoic evolution of the Grenville Province and adjacent Makkovik Province in eastern Labrador. Geol Assoc Can Spec Pap 31 (in press)Google Scholar
  11. Gower CF, Erdmer P, Wardle RJ (1986) The Double Mer Formation and the Lake Melville Rift System, eastern Labrador. Can J Earth Sci (in press)Google Scholar
  12. Jaffey AH, Flynn KF, Glendenin LE, Bentley WC, Essling AM (1971) Precision measurements of half-lives and specific activities of 235U and 238U. Physiol Rev C 4:1889–1906Google Scholar
  13. Krogh TE (1973) A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations. Geochim Cosmochim Acta 37:485–494Google Scholar
  14. Krogh TE, Davis GL (1973) The significance of inherited zircons on the age and origin of igneous rocks — an investigation of the ages of the Labrador adamellites. Carnegie Inst Yearb 1972/1973:610–613Google Scholar
  15. Krogh TE (1982a) Improved accuracy of U-Pb zircon ages by the creation of more concordant systems using an air abrasion technique. Geochim Cosmochim Acta 46:637–649Google Scholar
  16. Krogh TE (1982b) Improved accuracy of U-Pb dating by selection of more concordant fractions using a high gradient magnetic separation technique. Geochim Cosmochim Acta 46:631–636Google Scholar
  17. Manhes G, Minster JF, Allègre CJ (1978) Comparative uraniumthorium-lead and rubidium-strontium study of the Saint Severin amphoterite: consequence for early solar system chronology. Earth Plant Sci Lett 39:14–24Google Scholar
  18. Schärer U, Allègre CJ (1983) The Palung granite (Himalaya): highresolution U-Pb systematics in zircon and monazite. Earth Planet Sci Lett 63:423–432Google Scholar
  19. Schärer U, Xu RH, Allègre CJ (1986) U-(Th)-Pb systematics and ages of Himalayan leucogranites, Tibet. Earth Planet Sci Lett 77:35–48Google Scholar
  20. Stacey JS, Kramers JD (1975) Approximation of terrestrial lead isotope evolution by a two-stage model. Earth Planet Sci Lett 26:207–221Google Scholar
  21. Steiger RH, Jäger E (1977) Subcommission on geochronology: convention on the use of decay constants in geo- and cosmochronology. Earth Planet Sci Lett 36:359–362Google Scholar
  22. Stevenson IM (1970) Rigolet and Groswater Bay map-areas, New-foundland (Labrador). Geol Surv Can, Pap 69–48:24Google Scholar
  23. Wanless RK (1972) Age determinations and geological studies, K-Ar isotopic ages report 10. Geol Surv Can, Pap 71–2:86–89Google Scholar
  24. Wanless RK (1973) Age determinations and geological studies, K-Ar isotopic ages, report 11. Geol Surv Can, Pap 73–2:99–104Google Scholar
  25. Xu RH, Schärer U, Allègre CJ (1985) Magmatism and metamorphism in the Lhasa Block (Tibet): a geochronological study. J Geol 93:41–57Google Scholar

Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • U. Schärer
    • 1
  • T. E. Krogh
    • 1
  • C. F. Gower
    • 2
  1. 1.Department of Mineralogy and GeologyRoyal Ontario MuseumTorontoCanada
  2. 2.Department of Mines and EnergyGovernment of Newfoundland and LabradorNewfoundlandCanada

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