Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-23T22:39:21.207Z Has data issue: false hasContentIssue false
  • English
  • Français

Mylonitic microstructures and their bearing on the development of mylonites – an example from deformed trondhjemites of the Bergen Arc region, SW Norway

Published online by Cambridge University Press:  01 May 2009

S. Sinha Roy
S. Sinha Roy
Affiliation:
Geologisk Institutt, Universitetet i Bergen, Avd. A., J. Frielesgt 1, 5014 Bergen, Norway
Get access Rights & Permissions [Opens in a new window]

Summary

Thrust-bound bodies of trondhjemite, showing variable intensity of deformation, contain micro-structural evidences which suggest that the mylonitic fabric in them had developed in stages. An initial shearing stage was followed by a flattening one when the characteristic mylonitic microstructures and banding developed. These stages were punctuated and overlapped by phases of recovery and recrystallization. Mineral parageneses and microstructures indicate that prograde metamorphism and ductile deformation characterize the flattening stage. The origin of mylonite is explained in a scheme of progressive deformation during which planes of maximum shear strain and flattening became almost parallel, so that brittle microstructures were either modified or obliterated by ductile ones. The sequence of microstructural development and mineral redistribution suggest that in mylonite formation mechanical process is accompanied with chemical mobility.

Type
Articles
Information
Geological Magazine , Volume 114 , Issue 6 , November 1977 , pp. 445 - 458
Copyright
Copyright © Cambridge University Press 1977

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bell, T. H. & Etheridge, M. A. 1973. Microstructures of mylonites and their descriptive terminology. Lithos 6, 337–48.CrossRefGoogle Scholar
Bellière, J. 1971. Mylonites, blastomylonites et domaines polymetamorphiques. Ann. Soc. geol. Belg. 94, 249–63.Google Scholar
Borradaile, G. J. 1976. A strain study of a granite–granite gneiss transition and accompanying schistosity formation in the Betic orogenic zone, SE Spain. J. geol. Soc. Lond. 132, 417–28.CrossRefGoogle Scholar
Carter, N. L., Christie, J. M. & Griggs, D. T. 1964. Experimental deformation and recrystallization of quartz. J. geol. 72, 687–733.CrossRefGoogle Scholar
Christie, J. M. 1960. Mylonitic rocks of the Moine thrust-zone in the Assynt Region, NW Scotland. Trans. geol. Soc. Edinb. 18, 79–93.CrossRefGoogle Scholar
Dalziel, I. W. D. & Bailey, S. W. 1968. Deformed garnets in a mylonitic rock from the Grenville Front and their tectonic significance. Am. J. Sci. 266, 542–62.CrossRefGoogle Scholar
Donath, F. A., Faill, R. T. & Tobin, D. G. 1971. Deformational mode fields in experimentally deformed rocks. Bull. geol. Soc. Am. 82, 1441–62.CrossRefGoogle Scholar
Eispacher, G. H. 1970. Deformation mechanics of mylonitic rocks and fractured granites in Cobequid Mountains, Nova Scotia, Canada. Bull. geol. Soc. Am. 81, 2009–20.CrossRefGoogle Scholar
Eskola, P. 1932. On the principle of metamorphic differentiation. Bull. Comm. geol. Fin. 67, 68–77.Google Scholar
Gay, N. C. & Jaeger, J. C. 1975. Cataclastic deformation of geological materials in matrices of differing composition. I. Pebbles and conglomerates. Tectonophysics 27, 303–22.CrossRefGoogle Scholar
Hara, I., Takeda, K. & Kimura, T. 1973. Preferred lattice orientation of quartz in shear deformation. Hiroshima Univ. J. Sci. 7, 1–10.Google Scholar
Higgins, M. W. 1971. Cataclastic rocks. Prof. Pap. U.S. geol. Surv. 687, 97 pp.Google Scholar
Hobbs, B. E., Means, W. D. & Williams, P. 1976. An Outline of Structural Geology. New York: John Wiley.Google Scholar
Hossack, J. R. 1968. Pebble deformation and thrusting in the Bygdin area, Southern Norway. Tectonophysics 5, 315–339.CrossRefGoogle Scholar
Johnson, M. R. W. 1967. Mylonite zones and mylonitic banding. Nature, 213, 246–7.CrossRefGoogle Scholar
Knopf, E. B. 1931. Retrogressive metamorphism and phyllonitization. Am. J. Sci. 21, 1–27.CrossRefGoogle Scholar
Kolderup, C. F. & Kolderup, N. H. 1940. Geology of the Bergen Arc System. Bergens Mus. Skr. 20.Google Scholar
Krupicka, J. & Sassano, G. P. 1972. Multiple deformation of crystalline rocks in the Tazin Group, Eldorado Fay Mine, NW Saskatchewan. Can. J. Earth Sci. 9, 422–33.CrossRefGoogle Scholar
Kvale, A. 1960. The nappe area of the Caledonides in Western Norway. In: Guide to Excursion A7 and C4. Int. geol. Congr. 21st. Norsk geol. Unders. 212e.Google Scholar
Lapworth, C. 1885. The Highland controversy in British geology: its causes, course and consequences. Nature, Lond. 32, 558–9.Google Scholar
Moore, A. C. 1973. Studies of igneous and tectonic textures and layering in the rocks of the Gosse Pile intrusion, Central Australia. J. Petrology 14, 49–80.CrossRefGoogle Scholar
Nadai, A. 1963. Theory of Flow and Fracture of Solids. New York: McGraw-Hill.Google Scholar
Prinz, M. & Poldervaart, A. 1964. Layered mylonite from Beartooth Mountains, Montana. Bull. geol. Soc. Am. 75, 741–4.CrossRefGoogle Scholar
Quensel, P. 1916. Zur Kenntnis der Mylonitbilding erläutert an Material ausdem Kebnekaisgebeit. Bull. geol. Inst. Uppsala. 15, 91–116.Google Scholar
Ramberg, H. 1952. The Origin of Metamorphic and Metasomatic Rocks. Chicago: University of Chicago Press.Google Scholar
Ramsay, D. M. & Sturt, B. A. 1976. The syn-metamorphic emplacement of Mageroy nappe. Norsk. geol. Tiddsskr. (in the press).Google Scholar
Ramsay, J. G. & Graham, R. H. 1970. Strain variation in shear belts. Can. J. Earth Sci. 7, 786–813.CrossRefGoogle Scholar
Reed, J. G. & Bryant, B. 1964. Evidence for strike-slip faulting along the Brevard zone in North Carolina. Bull. geol. Soc. Am. 75, 1177–96.CrossRefGoogle Scholar
Reitan, P. H. 1968. Frictional heat during metamorphism: quantitative evaluation of concentration of heat generation in time. Lithos 1, 151–63.CrossRefGoogle Scholar
Ross, J. V. 1973. Mylonitic rocks and flattened garnets in the Southern Octanogan of British Columbia. Can. J. Earth Sci. 10, 1–17.CrossRefGoogle Scholar
Sander, B. 1912. Über einige Gesteinsgruppe des Tauernwestendes. Jahrb. Kaisler. königl. geol. Reichsanstalt. 62, 219–88.Google Scholar
Schmidt, W. 1932. Tektonic und Verformungslehre. Berlin: Borntraeger.Google Scholar
Schwerdtner, W. M. & Bauer, G. 1975. Tectonic significance of mylonite zones. N. Jb. Miner. Mh. 11, 500–9.Google Scholar
Sclar, C. B. 1965. Layered mylonites and the process of metamorphic differentiation. Bull. geol. Soc. Am. 76, 611–12.CrossRefGoogle Scholar
Shelley, D. 1974. Mechanical production of metamorphic banding – a critical appraisal. Geol. Mag. 111, 287–92.CrossRefGoogle Scholar
Siddans, A. W. B. 1972. Slaty cleavage – a review of research since 1815. Earth Sci. Rev. 8, 205–32.CrossRefGoogle Scholar
Sinha Roy, S. 1977. Relation between coplanar minor folds of variable orientation, stretching lineation and thrust in the Daling rocks from Sikkim Himalayas. J. geol. Soc. Ind. 18, 153–69.Google Scholar
Sturt, B. A. 1969. Wrench fault deformation and annealing recrystallization during almandine amphibolite facies regional metamorphism. J. Geol. 77, 319–32.CrossRefGoogle Scholar
Sturt, B. A. 1974. New perspective of the bergen Arc System. Misc. Pap. geol. Soc. Lond. 2, 17–19.Google Scholar
Sturt, B. A., Skarpenes, O., Ohanian, A. T. & Pringle, I. R. 1975. Reconnaissance Rb/Sr isochron study in the Bergen Arc System and regional implications. Nature, Lond. 253, 595–9.CrossRefGoogle Scholar
Sturt, B. A. & Thon, A. 1976. Discussion: The age of orogenic deformation in the Swedish Caledonides. Am. J. Sci. 276, 385–9.CrossRefGoogle Scholar
Tullis, J., Christie, J. M. & Griggs, D. T. 1973. Microstructures and preferred orientation of experimentally deformed quartzite. Bull. geol. Soc. Am. 86, 632–8.2.0.CO;2>CrossRefGoogle Scholar
Turner, F. J. 1941. The development of pseudo-stratification by metamorphic differentiation in the schists of Otago, New Zealand. Am. J. Sci. 239, 1–16.CrossRefGoogle Scholar
Turner, F. J. 1948. Evolution of metamorphic rocks. Mem. geol. Soc. Am. 30.Google Scholar
Turner, F. J. & Verhoogen, J. 1960. Igneous and Metamorphic Petrology. New York: McGraw-Hill.Google Scholar
Vernon, R. H. 1974. Controls of mylonitic compositional layering during non-cataclastic ductile deformation. Geol. Mag. 111, 167–277.CrossRefGoogle Scholar
Vernon, R. H. & Ransom, D. M. 1971. Retrograde schists of the amphibolite facies at Broken Hill. J. geol. Soc. Aust. 18, 167–277.CrossRefGoogle Scholar
Waters, A. C. & Cambell, C. D. 1935. Mylonites from San Andreas Fault zone. Am. J. Sci. 29, 473–503.CrossRefGoogle Scholar
Wenk, E. 1936. Zur genese der Bändergneise von Ornö Huvud. Bull. geol. Inst. Uppsala. 26, 53–89.Google Scholar
White, S. 1973. Syntectonic recrystallization and texture development of quartz. Nature, Lond. 244, 276–8.CrossRefGoogle Scholar
Wilkinson, P., Soper, N. J. & Bell, A. M. 1975. Skolithos pipes as strain markers in mylonites. Tectonophysics 28, 143–57.CrossRefGoogle Scholar
Zeck, H. P. 1974. Cataclastites, hemiclastites, holoclastites, blasto-ditto, and myloblastites – cataclastic rocks. Am. J. Sci. 274, 1064–73.CrossRefGoogle Scholar