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Contributions to Mineralogy and Petrology

, Volume 147, Issue 5, pp 528–548 | Cite as

Eclogites of the Snowbird tectonic zone: petrological and U-Pb geochronological evidence for Paleoproterozoic high-pressure metamorphism in the western Canadian Shield

  • Julia A. Baldwin
  • Samuel A. Bowring
  • Michael L. Williams
  • Ian S. Williams
Original Paper

Abstract

Eclogite occurs within the southern domain of the East Athabasca mylonite triangle in northern Saskatchewan. Situated at the boundary between the Archean Rae and Hearne Provinces of the western Canadian Shield, the East Athabasca mylonite triangle is a fundamental exposure of the ~3,000-km-long Snowbird tectonic zone. The eclogite occurs in association with a variety of lower crustal high-pressure granulites that record a complex metamorphic history from 2.6 to 1.9 Ga. Temperatures of the eclogite facies metamorphism are constrained by garnet-clinopyroxene exchange thermometry at 920–1,000 °C. Minimum pressure conditions are recorded by the jadeite+quartz=albite geobarometer at 1.8–2.0 GPa. A near-isothermal decompression path to granulite facies conditions is inferred from retrograde reaction textures involving the formation of granulite facies assemblages such as orthopyroxene-plagioclase and pargasite-plagioclase. U-Pb IDTIMS zircon geochronology of the eclogite yields a weighted mean 207Pb/206Pb date of 1,904.0±0.3 Ma, which we interpret as the time of peak eclogite facies metamorphism. SHRIMP in situ analyses of metamorphic zircons included within omphacitic clinopyroxene support this interpretation with a weighted mean 207Pb/206Pb date of 1,905±19 Ma. Inclusion suites of high-pressure phases and the petrographic setting of zircon are a direct link between zircon growth and eclogite facies metamorphism. Zircon from one eclogite sample has older cores that are 2.54 Ga, which is a minimum age for the emplacement or earliest metamorphism of the gabbroic protolith. U-Pb rutile data indicate slow cooling at ~1°C/Ma below ~500 °C from 1.88 to 1.85 Ga. The formation and exhumation of the eclogites at ca.1.9 Ga has important implications for the tectonic significance of the Snowbird tectonic zone during the Paleoproterozoic. The eclogites described here are consistent with transport of continental crust to mantle depths during the Paleoproterozoic, followed by rapid buoyancy-driven exhumation to normal lower crustal depths.

Keywords

Zircon Kyanite Mafic Granulite Metamorphic Zircon Zircon Growth 
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.

Notes

Acknowledgements

This research was supported by National Science Foundation grant EAR-0001131 to SAB and MLW and a research grant from the Mineralogical Society of America to JAB. We thank J. Hanchar for providing the CL image shown in Fig. 11 and T. Grove, P.J. O’Brien, R. Berman, G. Ross for helpful discussions. We also appreciate N. Chatterjee’s assistance with the electron microprobe. Thorough and constructive reviews by F. Corfu and an anonymous reviewer greatly improved the manuscript.

References

  1. Baldwin JA, Bowring SA, Williams ML (2003) Petrological and geochronological constraints on high-pressure, high-temperature metamorphism in the Snowbird tectonic zone, Canada. J Metamorph Geol 21:81–98CrossRefGoogle Scholar
  2. Barth MG, Rudnick RL, Carlson RW, Horn I, McDonough WF (2002) Re-Os and U-Pb geochronological constraints on the eclogite-tonalite connection in the Archean Man Shield, West Africa. Precambrian Res 118:267–283CrossRefGoogle Scholar
  3. Berman RG (1990) Mixing properties of Ca-Mg-Fe-Mn garnets. Am Mineral 75:328–344Google Scholar
  4. Berman RG (1991) Thermobarometry using multi-equilibrium calculations: a new technique, with petrological applications. Can Mineral 29:833–855Google Scholar
  5. Berman RG, Aranovich LY (1996) Optimized standard state and solution properties of minerals: I. Model calibration for olivine, orthopyroxene, cordierite, garnet, and ilmenite in the system FeO-MgO-CaO-Al2O2-TiO2-SiO2. Contrib Mineral Petrol 126:1–24Google Scholar
  6. Bingen B, Austrheim H, Whitehouse M (2001) Ilmenite as a source for zirconium during high-grade metamorphism? Textural evidence from the Caledonides of Western Norway and implications for zircon geochronology. J Petrol 42:355–375Google Scholar
  7. Brastad K (1985) Relationships between peridotites, anorthosites, and eclogites in Bjorkedalen, western Norway. In: Gee DG, Sturt BA (eds) The Caledonide Orogen—Scandinavia and related areas. Wiley, New York, pp 859–872Google Scholar
  8. Bröcker M, Enders M (1999) U-Pb zircon geochronology of unusual eclogite-facies rocks from Syros and Tinos (Cyclades, Greece). Geol Mag 136:111–118CrossRefGoogle Scholar
  9. Caby R (1994) Precambrian coesite from northern Mali; first record and implications for plate tectonics in the trans-Saharan segment of the Pan-African belt. Eur J Mineral 6:235–244Google Scholar
  10. Caby R, Bertrand JM, Black R (1981) Oceanic closure and continental collision in the Hogger-Iforas Pan-African segment. In: Kröner A (eds) Precambrian plate tectonics. Elsevier, Amsterdam, pp 407–434Google Scholar
  11. Carswell DA (1990) Eclogites and the eclogite facies: definitions and classification. In: Carswell DA (eds) Eclogite facies rocks. Chapman and Hall, New York, pp 1–13Google Scholar
  12. Chatterjee ND, Johannes W, Leistner H (1984) The system CaO-Al2O3-SiO2-H2O: new phase equilibria data, some calculated phases relations, and their petrological applications. Contrib Mineral Petrol 88:1–13Google Scholar
  13. Creaser RA, Heaman LM, Erdmer P (1997) Timing of high-pressure metamorphism in the Yukon-Tanana terrane, Canadian Cordillera: constraints from U-Pb zircon dating of eclogite from the Teslin tectonic zone. Can J Earth Sci 34:709–715Google Scholar
  14. Ellis DJ, Maboko MAH (1992) Precambrian tectonics and the physiochemical evolution of the continental crust. I. The gabbro-eclogite transition revisited. Precambrian Res 55:491–506CrossRefGoogle Scholar
  15. Ernst WG (1972) Occurrence and mineralogic evolution of blueschist belts with time. Am J Sci 272:657–668Google Scholar
  16. Flowers RM, Baldwin JA, Bowring SA, Williams ML (2002) Age and significance of the Proterozoic Chipman dike swarm, Snowbird tectonic zone, northern Saskatchewan. Geol Assoc Can—Mineralogical Association of Canada Annual Meeting Abstracts 27:35Google Scholar
  17. Fountain DM (1976) The Ivrea-Verbano zone and Strona-Ceneri zones, northern Italy: a cross section of the continental crust—new evidence from seismic velocities. Tectonophysics 33:145–166CrossRefGoogle Scholar
  18. Gebauer D, Lappin MA, Grünenfelder M, Wyttenbach A (1985) The age and origin of some Norwegian eclogites: a U-Pb zircon and REE study. Chem Geol 52:227–247Google Scholar
  19. Gilboy CF (1978) Reconnaissance geology, Stony Rapids area (part of NTS area 74P). In: Christopher JE, Macdonald R (eds) Summary of investigations, Saskatchewan Geol Surv, pp 35–42Google Scholar
  20. Goodacre AK, Grieve RAF, Halpenny JF, Sharpton VL (1987) Horizontal gradient of the Bouguer gravity anomaly map of Canada, Canadian Geophysical Atlas, Map 5Google Scholar
  21. Green DH, Ringwood AE (1967) An experimental investigation of the gabbro to eclogite transformation and its petrological applications. Geochim Cosmochim Acta 48:767–833Google Scholar
  22. Green DH, Ringwood AE (1972) A comparison of recent experimental data on the gabbro-garnet granulite-eclogite transition. J Geol 80:277–288Google Scholar
  23. Griffin WL, O’Reilly SY, Pearson NJ (1990) Eclogite stability near the crust-mantle boundary. In: Carswell DA (eds) Eclogite facies rocks. Chapman and Hall, New York, pp 291–314Google Scholar
  24. Grove TL, Kinzler RJ, Bryan WB (1992) Fractionation of Mid-Ocean Ridge Basalt (MORB). In: (eds) Mantle flow and melt generation at mid-ocean ridges. Geophys Monogr 71. Am Geophys Union, pp 281–310Google Scholar
  25. Hanchar JM, Rudnick RL (1995) Revealing hidden structures; the application of cathodoluminescence and back-scattered electron imaging to dating zircons from lower crustal xenoliths. Lithos 36:289–303Google Scholar
  26. Hanmer S (1994) Geology, East Athabasca mylonite triangle, Saskatchewan. Geol Surv Can Map 1859AGoogle Scholar
  27. Hanmer S (1997) Geology of the Striding-Athabasca mylonite zone, northern Saskatchewan and southeastern District of Mackenzie, Northwest Territories. Geol Surv Can Bull 501:1–92Google Scholar
  28. Hanmer S, Parrish R, Williams M, Kopf C (1994) Striding-Athabasca mylonite zone: complex Archean deep-crustal deformation in the East Athabasca mylonite triangle, northern Saskatchewan. Can J Earth Sci 31:1287–1300Google Scholar
  29. Hanmer S, Williams M, Kopf C (1995a) Modest movements, spectacular fabrics in an intracontinental deep-crustal strike-slip fault: Striding-Athabasca mylonite zone, NW Canadian Shield. J Struct Geol 17:493–507CrossRefGoogle Scholar
  30. Hanmer S, Williams M, Kopf C (1995b) Striding-Athabasca mylonite zone: implications for the Archean and Early Proterozoic tectonics of the western Canadian Shield. Can J Earth Sci 32:178–196Google Scholar
  31. Hoffman PF (1988) United Plates of America, the birth of a craton: Early Proterozoic assembly and the growth of Laurentia. Annu Rev Earth Planet Sci Lett 16:543–603Google Scholar
  32. Hoffman PF (1989) Precambrian geology and tectonic history of North America. In: Bally AW, Palmer AR (eds) The geology of North America—an overview. Geol Soc Am pp 447–512Google Scholar
  33. Holland TJB (1980) The reaction albite=jadeite+quartz determined experimentally in the range 600–1,200 °C. Am Mineral 65:129–134Google Scholar
  34. Holland TJB (1990) Activities of components in omphacitic solid solutions: an application of Landau theory to mixtures. Contrib Mineral Petrol 105:446–453Google Scholar
  35. Indares A (1993) Eclogitized gabbros from the eastern Grenville Province; textures, metamorphic context, and implications. Can J Earth Sci 30:159–173Google Scholar
  36. Indares A, Dunning GR (1997) Coronitic metagabbro and eclogite from the Grenville Province of western Quebec; interpretation of U-Pb geochronology and metamorphism. Can J Earth Sci 34:891–901Google Scholar
  37. Jahn B, Caby R, Monie P (2001) The oldest UHP eclogites of the world: age of UHP metamorphism, nature of protoliths and tectonic implications. Chem Geol 178:143–158CrossRefGoogle Scholar
  38. Kay RW, Kay S (1993) Delamination and delamination magmatism. Tectonophysics 219:177–189CrossRefGoogle Scholar
  39. Kopf CF (1999) Deformation, metamorphism, and magmatism in the East Athabasca mylonite triangle, northern Saskatchewan: implications for the Archean and Early Proterozoic crustal structure of the Canadian Shield. Department of Geosciences 139Google Scholar
  40. Kornprobst J, Piboule M, Roden M, Tabit A (1990) Corundum-bearing garnet clinopyroxenites at Beni Bousera (Morocco): original plagioclase-rich gabbros recrystallized at depth within the mantle? J Petrol 31:717–745Google Scholar
  41. Krogh TE (1973) A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determination. Geochim Cosmochim Acta 46:485–494CrossRefGoogle Scholar
  42. Krogh TE (1982) Improved accuracy of U-Pb zircon ages by the creation of more concordant systems using an abrasion technique. Geochim Cosmochim Acta 46:637–649Google Scholar
  43. Leake BE (1978) Nomenclature of amphiboles. Am Mineral 63:1023–1052Google Scholar
  44. Mahan KH, Williams ML, Baldwin JA (2003) Contractional uplift of deep crustal rocks along the Legs Lake shear zone, western Churchill Province, Canadian Shield. Can J Earth Sci 40:1085–1110CrossRefGoogle Scholar
  45. Mariano AN (1989) Cathodoluminescence emission spectra of rare earth element activators in minerals. In: Lipin BR, McKay GA (eds) Geochemistry and mineralogy of rare earth elements, Rev Mineral 21. Mineral Soc Am, pp 339–348Google Scholar
  46. Maruyama S, Liou JG (1998) Initiation of ultrahigh-pressure metamorphism and its significance on the Proterozoic-Phanerozoic boundary. The Island Arc 7:6–35CrossRefGoogle Scholar
  47. Maruyama S, Liou JG, Terabayashi M (1996) Blueschists and eclogites of the world and their exhumation. Int Geol Rev 38:485–594Google Scholar
  48. Medaris G, Jelínek E, Mísar Z (1995) Czech eclogites: terrane settings and implications for Variscan tectonic evolution of the Bohemian Massif. Eur J Mineral 7:7–28Google Scholar
  49. Mezger K, Hanson GN, Bohlen SR (1989) High-precision U-Pb ages of metamorphic rutile: application to the cooling history of high-grade terranes. Earth Planet Sci Lett 96:106–118CrossRefGoogle Scholar
  50. Möller A, Appel P, Mezger K, Schenk V (1995) Evidence for a 2 Ga subduction zone: eclogites in the Usagaran belt of Tanzania. Geology 23:1067–1070CrossRefGoogle Scholar
  51. Mottana A, Carswell DA, Chopin C, Oberhänsli R (1990) Eclogite facies mineral parageneses. In: Carswell DA (eds) Eclogite facies rocks. Chapman and Hall, New York, pp 14–52Google Scholar
  52. O’Brien PJ (1993) Partially retrograded eclogites of the Münchberg Massif, Germany: records of a multi-stage Variscan uplift history in the Bohemian Massif. J Metamorph Geol 11:241–260Google Scholar
  53. O’Brien PJ, Röhr C, Okrusch M, Patzak M (1992) Eclogite facies relics and multistage breakdown in metabasites of the KTB pilot hole, NE Bavaria: implications for the Variscan tectonometamorphic evolution of the NW Bohemian Massif. Contrib Mineral Petrol 112:261–278Google Scholar
  54. O’Brien PJ, Rötzler J (2003) High-pressure granulites: formation, recovery of peak conditions and implications for tectonics. J Metamorph Geol 21:3–20CrossRefGoogle Scholar
  55. O’Brien PJ, Vrána S (1995) Eclogites with a short-lived granulite facies overprint in the Moldanubian Zone, Czech Republic: petrology, geochemistry, and diffusion modeling of garnet zoning. Geol Rundsch 84:473–488CrossRefGoogle Scholar
  56. Paquette J-L, Menot R-P, Peucat J-J (1989) REE, Sm-Nd, and U-Pb zircon study of eclogites from the Alpine External Massifs (Western Alps): evidence for crustal contamination. Earth Planet Sci Lett 96:181–198Google Scholar
  57. Percival JA, Card KD (1983) Archean crust as revealed in the Kapuskasing Uplift, Superior Province, Canada. Geology 11:323–326Google Scholar
  58. Poli S, Schmidt MW (1998) The high-pressure stability of zoisite and phase relationships of zoisite-bearing assemblages. Contrib Mineral Petrol 130:162–175Google Scholar
  59. Pouba Z, Padera K, Fiala J (1985) Omphacite granulite from the NE marginal area of the Bohemian Massif (Rychleby Mts.). Neues Jahrb Mineral Abh 151:29–52Google Scholar
  60. Powell R (1985) Regression diagnostics and robust regression in geothermometer/geobarometer calibration: the garnet-clinopyroxene geothermometer revisited. J Metamorph Geol 3:231–243Google Scholar
  61. Powell R, Holland TJB (1988) An internally consistent dataset with uncertainties and correlations; 3, applications to geobarometry, worked examples and a computer program. J Metamorph Geol 6:173–204Google Scholar
  62. Ross GM, Parrish RR, Villeneuve ME, Bowring SA (1991) Geophysics and geochronology of the crystalline basement of the Alberta Basin, western Canada. Can J Earth Sci 28:512–522Google Scholar
  63. Rubatto D (2002) Zircon trace element geochemistry: partitioning with garnet and the link between U-Pb ages and metamorphism. Chem Geol 184:123–138CrossRefGoogle Scholar
  64. Rubatto D, Gebauer D, Compagnoni R (1999) Dating of eclogite-facies zircons: the age of Alpine metamorphism in the Sesia-Lanzo Zone (Western Alps). Earth Planet Sci Lett 167:141–158CrossRefGoogle Scholar
  65. Rubatto D, Schaltegger U, Lombardo B, Colombo F, Compagnoni R (2001) Complex Paleozoic magmatic and metamorphic evolution in the Argentera Massif (Western Alps) resolved with U-Pb dating. Schweiz Mineral Petrogr Mitt 81:213–228Google Scholar
  66. Sanborn-Barrie M, Carr SD, Theriault R (2001) Geochronological constraints on metamorphism, magmatism, and exhumation of deep-crustal rocks of the Kramanituar Complex, with implications for the Paleoproterozoic evolution of the Archean western Churchill Province, Canada. Contrib Mineral Petrol 141:592–612Google Scholar
  67. Schmitz MD, Bowring SA (2001) The significance of U-Pb zircon dates in lower crustal xenoliths from the southwestern margin of the Kaapvaal craton, southern Africa. Chem Geol 172:59–76CrossRefGoogle Scholar
  68. Snoeyenbos DR, Williams ML, Hanmer S (1995) Archean high-pressure metamorphism in the western Canadian Shield. Eur J Mineral 7:1251–1272Google Scholar
  69. Stacey JS, Kramers JD (1975) Approximation of terrestrial lead isotope evolution by a two-stage model. Earth Planet Sci Lett 26:207–221Google Scholar
  70. Stern RA, Berman RG (2000) Monazite U-Pb and Th-Pb geochronology by ion microprobe, with an application to in situ dating of an Archean metasedimentary rock. Chem Geol 172:113–130CrossRefGoogle Scholar
  71. Sun SS, McDonough WF (1989) Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders AD, Norry MJ (eds) Magmatism in the ocean basins. Geol Soc Spec Publ, pp 313–345Google Scholar
  72. 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 14:29–47Google Scholar
  73. Williams ML, Hanmer S, Kopf C, Darrach M (1995) Syntectonic generation and segregation of tonalitic melts from amphibolite dikes in the lower crust, Striding-Athabasca mylonite zone, northern Saskatchewan. J Geophys Res 100:15717–15734Google Scholar
  74. Williams ML, Melis EA, Kopf C, Hanmer S (2000) Microstructural tectonometamorphic processes and the development of gneissic layering: a mechanism for metamorphic segregation. J Metamorph Geol 18:41–57CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Julia A. Baldwin
    • 1
    • 4
  • Samuel A. Bowring
    • 1
  • Michael L. Williams
    • 2
  • Ian S. Williams
    • 3
  1. 1.Department of Earth, Atmospheric and Planetary SciencesMassachusetts Institute of TechnologyCambridgeUSA
  2. 2.Department of GeosciencesUniversity of MassachusettsAmherstUSA
  3. 3.Research School of Earth SciencesThe Australian National UniversityCanberraAustralia
  4. 4.Department of Geology, Laboratory for Crustal PetrologyUniversity of MarylandCollege ParkUSA

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