Advertisement

Characteristics of a Continental Margin Magmatic Arc as a Function of Depth: The Skagit-Methow Crustal Section

  • Bryan Kriens
  • Brian Wernicke
Part of the NATO ASI Series book series (ASIC, volume 317)

Abstract

Calc-alkaline arc magmatism has been documented throughout NW Washington and SW British Columbia at around 95–85 Ma. Migmatites, orthogneisses, directionless plutons, and volcanic flows of mid-Cretaceous age are exposed in the region, and represent the major constituents of the arc. In the Ross Lake area of northern Washington, upper to middle crustal levels of the arc have been uplifted and exposed by large-scale Paleogene folding as a relatively intact vertical crustal section. Thus, the vertical variation in deformation, metamorphism, and magma behavior in a magmatic arc may be directly observed. Based on stratigraphic, structural, and petrologic data, the arc-section consists of a brittlely deformed upper crust containing a few plutons, and a ductilely deformed and migmatized middle crust containing numerous large plutons. Ductility in the largely quartzose country rocks and plutons is observed only below the uppermost limit of voluminous middle crustal plutons at about 12–14 km depth in the crustal section. Assuming the onset of ductility in quartz represents a high strength gradient in the crust, the high strength “lid” at the brittle-ductile transition is suggested to have caused large-scale ponding of magma. Ambient country rock viscosity thus appears to be a major control on the mechanics of magma ascent in this region.

Keywords

Country Rock Quartz Diorite Middle Crust Magma Ascent Contact Aureole 
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.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Adams, J.B., 1964, Origin of the Black Peak quartz diorite, Northern Cascades, Washington:American Journal of Science, v. 262, p. 290–306.CrossRefGoogle Scholar
  2. Armstrong, R.L., 1988, Mesozoic and Early Cenozoic magmatic evolution of the Canadian Cordillera, in Clark, S.P., B.C. Burchfiel, and J. Suppe, eds., Processes in Continental Lithospheric Deformation: Geological Society of America Special Paper 218, p. 55–91.Google Scholar
  3. Barksdale, J.D., 1975, Geology of the Methow Valley, Okanogan County, Washington: State of Washington, Department of Natural Resources, Division of Geology and Earth Resources Bulletin 68, 72 p.Google Scholar
  4. Brace, W.F., and Kohlstedt, D.L., 1980, Limits on lithospheric stress imposed by laboratory experiments: Journal of Geophysical Research, v. 85, n. Bll, p. 6248–6252.Google Scholar
  5. Daly, R.A., G.E. Manger, and S.P. Clark, 1966, Density of rocks: Geological Society of America Memoir 97, p. 20–26.Google Scholar
  6. Fuis, G.S., W.D. Mooney, J.H. Healy, G.A. McMechan, and W.J. Lutter, 1984, A seismic refraction survey of the Imperial Valley region, California: Journal of Geophysical Research, v. 89, n. B2, p. 1165–1189.Google Scholar
  7. Glazner, A.F., and Ussier III, W., 1988, Trapping of magma at midcrustal density discontinuities: Geophysical Research Letters, v. 15, n. 7, p. 673–675.Google Scholar
  8. Haugerud, R.A., 1985, Geology of the Hozameen Group and Ross Lake shear zone, Maselpanik area, North Cascades, southwest British Columbia [Ph.D. thesis]: Seattle, Washington, University of Washington, 269 p.Google Scholar
  9. Hoppe, W.J., 1984, Origin and age of the Gabriel Peak Orthogneiss, North Cascades, Washington [M.Sc. thesis]: Lawrence, Kansas, University of Kansas, 79 p.Google Scholar
  10. Kriens, B., 1987, Cretaceous-Tertiary tectonic evolution of the North Cascades, Washington: new findings from the Ross Lake fault zone and vicinity: Geological Society of America Abstracts with Programs, v. 19, n. 6, p. 396.Google Scholar
  11. Kriens, B., 1988, Tectonic Evolution of the Ross Lake Area, Northwest Washington-Southwest British Columbia [Ph.D. thesis]: Cambridge, Massachussetts, Harvard University, 214 p.Google Scholar
  12. Kriens, B., E. Aliberti, and B. Wernicke, 1987, Early Eocene convergent deformation in the North Cascades and SW British Columbia - occlusion tectonics vs. dextral slip: International Union of Geodesy and Geophysics Abstracts, 19th General Assembly, v. 1, p. 111.Google Scholar
  13. Kriens, B., and Wernicke B., 1986, Crustal sections and arc magmatism: new findings from the Ross Lake fault zone, North Cascades, Washington (abstract): EOS, v. 67, n. 44, p. 1189.Google Scholar
  14. Kriens, B., and Wernicke, B., 1987, Characteristics of a continental margin magmatic arc with depth: the Skagit-Methow crustal section: Geological Society of America Abstracts with Programs, v. 19, n. 7, p. 733.Google Scholar
  15. Kriens, B., and Wernicke, B., 1987, Characteristics of a continental margin magmatic arc with depth: the Skagit-Methow crustal section: Geological Society of America Abstracts with Programs, v. 19, n. 7, p. 733.Google Scholar
  16. Marsh, B.D., 1982, On the mechanics of igneous diapirism, stoping, and zone melting: American Journal of Science, v. 282, p. 808–855.CrossRefGoogle Scholar
  17. Mattinson, J.M., 1972, Ages of zircons from the Northern Cascade Mountains, Washington: Geological Society of America Bulletin, v. 83, p. 3769–3784.CrossRefGoogle Scholar
  18. Miller, R.B., 1988, Possible role of ductile shear zones in linking overstepping strike-slip faults, Ross Lake fault zone, North Cascades, Washington: Geological Society of America Abstracts with Programs, v. 20, n. 7, p. A108.Google Scholar
  19. Miller, R.B., S.A. Bowring, and W.J. Hoppe, 1988, New evidence for extensive Paleogene plutonism and metamorphism in the crystalline core of the North Cascades: Geological Society of America Abstracts with Programs, v. 20, n. 5, p. 432–433.Google Scholar
  20. Miller, R.B., P. Misch, and W.J. Hoppe, 1985, New observations on the central and southern segments of the Ross Lake fault zone, North Cascades, Washington: Geological Society of America Abstracts with Programs, v. 17, n. 6, p. 370.Google Scholar
  21. Miller, R.B., and N.W. Walker, 1987, Structure and age of the Oval Peak Batholith: implications for the Ross Lake Fault Zone, Washington: Geological Society of America Abstracts with Programs, v. 19, n. 6, p. 433.Google Scholar
  22. Misch, P., 1964, Age determinations on crystalline rocks of Northern Cascade Mountains, in Kulp, J.L., Senior Investigator, Investigations in Isotopic Geochemistry: U.S. Atomic Energy Commission Publication NYO-7243, Appendix D, Columbia University, Lamont Geological Observatory, Palisades, New York, Appendix D, pp. 1–15.Google Scholar
  23. Misch, P., 1966, Tectonic evolution of the Northern Cascades of Washington State: Canadian Institute of Mining and Metallurgy Special Volume 8, p. 101–148.Google Scholar
  24. Misch, P., 1988, Tectonic and metamorphic evolution of the North Cascades: an overview, in Ernst, W.G., ed., Metamorphism and Crustal Evolution of the Western United States: Englewood Cliffs, New Jersey, Prentice-Hall, p. 180–195.Google Scholar
  25. Rivers, M.L., and Carmichael, I.S.E., 1987, Ultrasonic studies of silicate melts: Journal of Geophysical Research, v. 92, n. B9, p. 924720139270.Google Scholar
  26. Roddick, J.A., J.E. Muller, and A.V. Okulitch, 1979, Fraser River 1:1,000,000 geological map: Geological Survey of Canada, sheet 92, map 1386A.Google Scholar
  27. Sams, D.B., and Saleeby, J.B., 1988, Geology and petrotectonic significance of crystalline rocks of the southernmost Sierra Nevada, California, in Ernst, W.G., ed., Metamorphism and Crustal Evolution of the Western United States: Englewood Cliffs, New Jersey, Prentice-Hall, p. 865–893.Google Scholar
  28. Strehlau, J., and Meissner, R., 1987, Estimation of crustal viscosities and shear stresses from an extrapolation of experimental steady state flow data, in Fuchs, K., and Froidevaux, C., eds., Composition, Structure, and Dynamics of the Lithosphere - Asthenosphere System: American Geophysical Union Geodynamics Series, v. 16, p. 69–87.Google Scholar
  29. Tabor, R.W., J.C. Engels, and M.H. Staatz, 1968, Quartz diorite-quartz monzonite and granite plutons of the Pasayten River area, Washington - petrology, age, and emplacement, in Geological Survey Research 1968: U.S. Geological Survey Professional Paper 600-C, p. C45–C52.Google Scholar
  30. Tennyson, M.E., and Cole, M.R., 1978, Tectonic significance of Upper Mesozoic Methow-Pasayten Sequence, northeastern Cascade Range, Washington and British Columbia, in Howell, D.G. and K.A. McDougall, eds., Mesozoic Paleogeography of the Western United States, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium, p. 499–508.Google Scholar
  31. Trexler, J.H., Jr., and Bourgeois, J., 1985, Evidence for mid-Cretaceous wrench faulting in the Methow basin, Washington: tectonostratigraphic setting of the Virginian Ridge Formation: Tectonics, v. 4, p. 379–394.Google Scholar
  32. Turcotte, D.L., and Schubert, G., 1982, Geodynamics: Applications of Continuum Physics to Geological Problems: New York, New York, John Wiley and Sons, 450 p.Google Scholar
  33. Wernicke, B., 1986, The Basin and Range moho, 5–10 second reflectivity, and a simple physical model for continental rift magmatism (abstract): EOS, v. 67, p. 1184.Google Scholar
  34. Whitney,D. L. and McGroder, M. F., 1989, Cretaceous crustal section through the proposed Insular-Intermontante suture, North Cascades, Washington: Geology, V. 17, p. 555–558.Google Scholar

Copyright information

© Kluwer Academic Publishers 1990

Authors and Affiliations

  • Bryan Kriens
    • 1
  • Brian Wernicke
    • 2
  1. 1.Department of Earth and Planetary SciencesHarvard UniversityCambridgeUSA
  2. 2.Department of Earth SciencesCalifornia State UniversityCarsonUSA

Personalised recommendations