Contributions to Mineralogy and Petrology

, Volume 69, Issue 2, pp 119–131 | Cite as

Mineral chemistry and zoning in eclogite inclusions from Colorado Plateau diatremes

  • Douglas Smith
  • M. Zientek
Article
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Accepted:

Abstract

Eclogite inclusions from kimberlitic diatremes on the Colorado Plateau contain intricately zoned garnet and pyroxene and unusual textures. Detailed electron microprobe traverses for a clinopyroxene-garnet-phengite-lawsonite-rutile assemblage show garnet zoning from Alm69Gr21Py10 (core) to Alm61Gr13Py26 (rim) and pyroxene zoning from Jd50 (core) through Jd77 to Jd55 (rim). Pyroxene cores are Cr-rich in another rock. Sharp compositional discontinuities and zoning reversals are preserved in garnet and pyroxene. Oscillatory zoning occurs in both phases on a 10–20 μm scale, with variations of up to 6% Py in garnet and 15% Jd in pyroxene. Phengite is unzoned and contains 74% celadonite endmember.

Skeletal, pyroxene-filled garnet crystals are common in some rocks, and garnets in other rocks clearly began growth as shell-like crystals. Some rocks contain domains of coarse, prismatic pyroxene with very fine-grained, interstitial magnesium silicates. The texture appears to have resulted from crystallization in the presence of a fluid phase, and water pressure is inferred to have equalled total pressure during crystallization. Eclogite formation at high water pressure may reflect subcrustal crystallization.

An analysis of error propagation shows that ferrous iron calculations from electron probe data are not meaningful for these jadeitic pyroxenes, and temperature differences between core and rim crystallization cannot be documented. The garnet textures and oscillatory zoning are unusual for metamorphic rocks, and they suggest disequilibrium crystallization after overstepping of reaction boundaries. All data fit a model of eclogite formation during cooling and metasomatism of basaltic dikes intruded into a cool upper mantle, but the results here do not preclude other origins, such as subduction zone metamorphism.

Keywords

Subduction Zone Ferrous Iron Oscillatory Zoning Magnesium Silicate Colorado Plateau 
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. Albee, A.L., Ray, L.: Correction factors for electron probe microanalysis of silicates, oxides, carbonates, phosphates, and sulfates. Anal. Chem. 42, 1408–1414 (1970)Google Scholar
  2. Bearth, P.: Zur Entstehung alpinotyper Eklogite. Schweiz. Mineral. Petrogr. Mitt. 45, 179–188 (1965)Google Scholar
  3. Bottinga, Y., Kudo, A., Weill, D.: Some observations on oscillatory zoning and crystallization of magmatic plagioclase. Am. Mineral. 51, 792–806 (1966)Google Scholar
  4. Bryhni, I., Griffin, W.L.: Zoning in eclogite garnets from Nordfjord, west Norway: Contrib. Mineral. Petrol. 32, 112–125 (1971)Google Scholar
  5. Chapman, D., Pollack, H.N.: Regional geotherms and lithospheric thickness. Geology 5, 265–268 (1977)Google Scholar
  6. Church, W.R.: Eclogites. In: Basalts: The Poldervaart Treatise on Rocks of Basaltic Composition (H.H. Hess and Arie Poldervaart, eds.), Vol. 2, pp. 755–798. New York, London, Sydney: Interscience Publishers 1968Google Scholar
  7. Coleman, R.G., Lee, D.E., Beatty, L.B., Brannock, W.W.: Eclogites and eclogites: their differences and similarities. Geol. Soc. Am. Bull. 76, 483–508 (1965)Google Scholar
  8. Dudley, P.P.: Electron microprobe analyses of garnet in glaucophane schists and associated eclogites. Am. Mineral. 54, 1139–1150 (1969)Google Scholar
  9. Ernst, W.G.: Significance of phengitic micas from low-grade schists. Am. Mineral. 48, 1357–1373 (1963)Google Scholar
  10. Ernst, W.G., Seki, Y., Onuki, H., Gilbert, M.C.: Comparative Study of Low-Grade Metamorphism in the California Coast Ranges and the Outer Metamorphic Belt of Japan. Geol. Soc. Am. Mem. 124, 276 p. (1970)Google Scholar
  11. Essene, E.J., Fyfe, W.S.: Omphacite in Californian metamorphic rocks. Contrib. Mineral. Petrol. 15, 1–23 (1967)Google Scholar
  12. Essene, E., Ware, N.G.: The low temperature xenolith origin of eclogites in diatremes. Geol. Soc. Am. Abstr. 2, 547–548 (1970)Google Scholar
  13. Fisher, G.W.: Rate laws in metamorphism. Geochim. Cosmochim. Acta 42, 1035–1050 (1978)Google Scholar
  14. Griffin, W.L., Raheim, A.: Convergent metamorphism of eclogites and dolerites, Kristiansund area, Norway. Lithos 6, 21–40 (1973)Google Scholar
  15. Helmstaedt, H., Anderson, O.L., Gavasci, A.T.: Petrofabric studies of eclogite, spinel-websterite, and spinel-lherzolite xenoliths from kimberlite-bearing breccia pipes in southeastern Utah and northeastern Arizona. J. Geophys. Res. 77, 4350–4365 (1972)Google Scholar
  16. Helmstaedt, H., Doig, R.: Eclogite nodules from kimberlite pipes of the Colorado Plateau — samples of subducted Francican-type oceanic lithosphere. Phys. Chem. Earth 9, 95–111 (1975)Google Scholar
  17. Helmstaedt, H., Schulze, D.J.: Type A-Type C eclogite transition in a xenolith from the Moses Rock diatreme-further evidence for the presence of metamorphosed ophiolites beneath the Colorado Plateau. In: Extended Abstracts. Sec. International Kimb. Conf. (1977)Google Scholar
  18. Kirkpatrick, R.J.: Crystal growth from the melt: a review. Am. Mineral. 60, 798–814 (1975)Google Scholar
  19. Krogh, E.J., Raheim, A.: Temperature and pressure dependence of Fe-Mg partitioning between garnet and phengite, with particular reference to eclogites. Contrib. Mineral. Petrol. 66, 75–80 (1978)Google Scholar
  20. Lofgren, G.: An experimental study of plagioclase crystal morphology: Isothermal crystallization. Am. J. Sci. 274, 243–273 (1974)Google Scholar
  21. McGetchm, T.R.: The Moses Rock dike: geology, petrology and mode of emplacement of kimberlite-bearing breccia dike, San Juan County, Utah. Doctorate dissertation, Calif. Inst. Tech., 405 p. (1968)Google Scholar
  22. McGetchm, T.R., Silver, L.T.: A crustal-upper mantle model for the Colorado Plateau based on observations of crystalline rock fragments in the Moses Rock dike. J. Geophys. Res. 77, 7022–7037 (1972)Google Scholar
  23. McGetchin, T.R., Ullrich, G.W.: Xenoliths in maars and diatremes with interferences for the moon, Mars, and Venus. J. Geophys. Res. 78, 1833–1853 (1973)Google Scholar
  24. Murad, E.: Zoned birefringent garnets from Thera Island, Santorini Group (Aegean Sea). Mineral. Mag. 40, 715–719 (1976)Google Scholar
  25. Newton, R.C., Fyfe, W.S.: High pressure metamorphism. In: The Evolution of the Crystalline Rocks (D.K. Bailey and R. MacDonald, eds.), pp. 101–186. London-New York-San Francisco: Academic Press 1976Google Scholar
  26. Newton, R.C., Kennedy, G.C.: Some equilibrium reactions in the join CaAlSi2O8-H2O. J. Geophys. Res. 68, 2967–2976 (1963)Google Scholar
  27. Nitsch, K.H.: Das P-T-Xco2-Stabilitätsfeld von Lawsonit. Contrib. Mineral. Petrol. 34, 116–134 (1972)Google Scholar
  28. Nitsch, K.H.: Neue Erkenntnisse zur Stabilität von Lawsonit. Fortschr. Mineral. 51, Beiheft 1, 34–36 (1974)Google Scholar
  29. O'Hara, M.J., Mercy, E.L.P.: Eclogite, peridotite, and pyrope from the Navajo country, Arizona and New Mexico. Am. Mineral. 51, 336–352 (1966)Google Scholar
  30. Raheim, A., Green, D.H.: Experimental determination of the temperature and pressure dependence of the Fe-Mg partition coefficient for coexisting garnet and clinopyroxene. Contrib. Mineral. Petrol. 48, 179–203 (1974)Google Scholar
  31. Raheim, A., Green, D.H.: P, T paths of natural eclogites during metamorphism — a record of subduction. Lithos 8, 317–328 (1975)Google Scholar
  32. Ryburn, R.J., Raheim, A., Green, D.H.: Determination of the P, T paths of natural eclogites during metamorphism — record of subduction. Lithos 9, 161–164 (1976)Google Scholar
  33. Shewmon, P.G.: Transformations in Metals, 394 p. New York: McGraw-Hill 1969Google Scholar
  34. Sibley, D.F., Vogel, T.A., Walker, B.M., Byerly, G.: The origin of oscillatory zoning in plagioclase: a diffusion and growth controlled model. Am. J. Sci. 276, 275–284 (1976)Google Scholar
  35. Smith, D.: Hydrous minerals and carbonates in peridotite inclusions from the Green Knobs and Buell Park kimberlitic diatremes on the Colorado Plateau. Proc. Sec. International Kimb. Conf. (in press)Google Scholar
  36. Smith, D., Levy, S.: Petrology of the Green Knobs diatreme and implications for the upper mantle below the Colorado Plateau. Earth Planet. Sci. Lett. 29, 107–125 (1976)Google Scholar
  37. Thompson, A.B., Tracy, R.J., Lyttle, P.T., Thompson, J.B. Jr.: Prograde reaction histories deduced from compositional zonation and mineral inclusions in garnet from the Gassetts schist, Vermont. Am. J. Sci. 277, 1152–1167 (1977)Google Scholar
  38. Velde, B.: Phengite micas: synthesis, stability and natural occurrence. Am. J. Sci. 263, 886–913 (1965)Google Scholar
  39. Velde, B.: Si4+ content of natural phengites. Contrib. Mineral. Petrol. 14, 250–258 (1967)Google Scholar
  40. Watson, K.D.: Kimberlite pipes of northeastern Arizona. In: Ultramafic and Related Rocks (P.J. Wyllie, ed.), pp. 261–269. New York: Wiley and Sons 1967Google Scholar
  41. Watson, K.D., Morton, D.M.: Eclogite inclusions in kimberlite pipes at Garnet Ridge, northeastern Arizona. Am. Mineral. 54, 267–285 (1969)Google Scholar
  42. Yoder, H.S. Jr., Chinner, G.A.: Almandite-pyrope-water system at 10,000 bars. Carnegie Inst. Washington Yearbook 59, 81–84 (1960)Google Scholar

Copyright information

© Springer-Verlag 1979

Authors and Affiliations

  • Douglas Smith
    • 1
  • M. Zientek
    • 1
  1. 1.Department of Geological SciencesUniversity of Texas AustinTexasUSA

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