Abstract
Diopside twins mechanically on two planes, (100) and (001), and the associated macroscopic twinning strains are identical (Raleigh and Talbot, 1967). An analysis based on crystal structural arguments predicts that both twin mechanisms involve shearing of the (100) octahedral layers (containing Ca2+, Mg2+ and Fe2+ ions) by a magnitude of c/2. Small adjustments or shuffles occur in the adjacent layers containing the [SiO4]4− tetrahedral chains. While the (100) twins are conventional with shear parallel to the composition plane, this analysis predicts that (001) twins form by a mechanism closely related to kinking.
A polycrystalline diopside specimen was compressed 8% at a temperature of 400° C, a pressure of 16 kilobars, and a compressive strain rate of about 10−4/s. Transmission electron microscopy on this specimen has revealed four basic lamellar features:
-
1)
(100) mechanical twin lamellae;
-
2)
(100) glide bands containing unit dislocations;
-
3)
(001) twin lamellae;
-
4)
(101) lamellar features, not as yet identified.
The (001) twins often contain remnant (100) lamellae of untwinned host. Twinning dislocations occur in these (100) lamellae and in the (001) twin boundaries with very high densities. Diffraction contrast experiments indicate that the twinning dislocations associated with both twin laws glide on (100) with Burgers vector b=X [001] where X is probably equal to 1/2 on the basis of the structural analysis.
Parallels are drawn between mechanical twinning in clinopyroxenes and clinoamphiboles. The exclusive natural occurrence of basal twins in shock-loaded clinopyroxenes and of analogous (\(\bar 1\)01) twins in clinoamphiboles is given a simple explanation in terms of the relative difficulty of the “kinking” mechanism as compared to direct glide parallel to the composition plane.
Similar content being viewed by others
References
Adams, F.D.: An experimental investigation into the action of differential pressure on certain minerals and rocks, employing the process suggested by Professor Kick. J. Geol. 18, 489–525 (1910)
Bloss, F.D., Papike, J.J., eds.: High temperature crystal chemistry. Am. Mineralogist 58, 577–704 (1973)
Borg, I.: Some shock effects in granodiorite to 270 kilobars at the Piledriver site. Am. Geophys. Union Geophys. Mon. 16, 293–311 (1972)
Brown, W.L., Morimoto, N., Smith, J.V.: A structural explanation of the polymorphism and transitions of MgSiO3. J. Geol. 69, 609–616 (1961)
Buck, P.: Verformung von Hornblende-Einkristallen bei Drücken bis 21 kb. Contrib. Mineral. Petrol. 28, 62–71 (1970)
Buck, P., Paulitsch, P.: Experimentelle Verformung von Glimmer- und Hornblende-Einkristallen. Naturwissenschaften 56, 460 (1969)
Buerger, M.J.: The genesis of twin crystals. Am. Mineralogist 30, 469–482 (1945)
Burnham, C.W., Clark, J.R., Papike, J.J., Prewitt, C.T.: A proposed crystallographic nomenclature for clinopyroxene structures. Z. Krist. 125, 109–119 (1967)
Cahn, R.W.: Twinned crystals. Phil. Mag., Suppl. 3, 363–445 (1954)
Cameron, M., Sueno, S., Prewitt, C.T., Papike, J.J.: High-temperature crystal chemistry of acmite, diopside, hedenbergite, jadeite, spodumene and ureyite. Am. Mineralogist 58, 594–618 (1973)
Chao, E.C.T.: Shock effects in certain rock-forming minerals. Science 156, 192–202 (1967)
Clark, J.R., Appleman, D.E., Papike, J.J.: Crystal-chemical characterization of clinopyroxenes based on eight new structure refinements. Mineral. Soc. Am. Spec. Papers 2, 31–50 (1969)
Coe, R.S., Kirby, S.H.: The orthoenstatite to clinoenstatite transformation by shearing and reversion by annealing: mechanism and potential applications. Contrib. Mineral. Petrol. 52, 29–55 (1975)
Deer, W., Howie, R.A., Zussman, J.: Rock-Forming Minerals, Vol. 2, Chain Silicates, p. 2. New York: John Wiley 1963
Dollinger, G., Blacic, J.D.: Deformation mechanisms in experimentally and naturally deformed amphiboles. Earth and Planet. Sci. Letters 26, 409–416 (1975)
Friedel, J.: Mechanical twinning. Ch. 6.7. In: Dislocations, pp. 173–177. Oxford-London-Edinburgh-New York-Paris-Frankfurt: Pergamon Press 1964
Green, H.W. II., Griggs, D.T., Christie, J.M.: Syntectonic and annealing recrystallization of finegrained quartz aggregates. In: Experimental and Natural Rock Deformation (Sander Volume), P. Paulitsch, ed., pp. 272–336. Berlin-Heidelberg-New York: Springer 1970
Griggs, D.T., Turner, F.J., Heard, H.C.: Deformation of rocks at 500 to 800° C. In: Rock Deformation, Geological Society of America Memoir 79, D.T. Griggs and J. Handin, eds., pp. 56–61 (1960)
Holser, W.T.: Relation of symmetry to structure in twinning, Zeit. Krist. 110, 249–265 (1958)
Hornemann, U., Müller, W.F.: Shock-induced deformation twins in clinopyroxene. Neues Jahrb. Mineral. Monatsh. 247–256 (1971)
Jawson, M.A., Dove, D.B.: The crystallography of deformation twinning. Acta Cryst. 13, 232–240 (1960)
Kirby, S.H.: The role of crystal defects in the shear-induced transformation of orthoenstatite to clinoenstatite. In: Applications of Electron Microscopy. In: Mineralogy, H.-R. Wenk, ed., pp. 465–472. Berlin-Heidelberg-New York: Springer 1976
Kirby, S.H., Christie, J.M.: A comparative study of two modes of deformation twinning in diopside (abstract). Trans. Am. Geophys. Union 53, 727 (1972)
McCormick, J.W.: Computer simulation of dislocation images in quartz. In: Applications of Electron Microscopy in Mineralogy. pp. 113–122. Berlin-Heidelberg-New York: Springer 1976
Mügge, O.: Über künstliche Zwillingsbildung durch Druck am Antimon, Wismuth und Diopsid. Neues Jahrb. Mineral. Geol. u. Paleont. 1, 181–191 (1886)
Pabst, A.: Transformation of indices in twin gliding. Bull. Geol. Soc. Am. 66, 897–912 (1955)
Papike, J.J., Ross, M., Clark, J.R.: Crystal-chemical characterization of clinoamphiboles based on five new structure refinements. Mineral. Soc. Am. Spec. Papers 2, 117–136 (1969)
Raleigh, C.B.: Glide mechanisms in experimentally deformed minerals. Science 150, 739–741 (1965)
Raleigh, C.B., Talbot, J.L.: Mechanical twinning in naturally and experimentally deformed diopside. Am. J. Sci. 265, 151–165 (1967)
Rooney, T.P., Gavasci, A.T., Riecker, R.E.: Mechanical twinning in experimentally and naturally deformed hornblende. Air Force Cambridge Research Laboratories Environmental Research Papers No. 484, 21 p. (1974)
Rooney, T.P., Riecker, R.E.: Constant strain rate deformation of amphibole minerals. Air Force Cambridge Research Laboratories Environmental Research Papers No. 430, 35 pp. (1973)
Rooney, T.P., Riecker, R.E., Gavasci, A.T.: Hornblende deformation features. Geology 3, 364–366 (1975)
Rooney, T.P., Riecker, R.E., Ross, M.: Deformation twins in hornblende. Science 169, 173–175 (1970)
Sclar, C.B.: Shock metamorphism of lunar rocks and fines from Tranquility Base. Proc. Apollo 11 Lunar Sci. Conf. Geochim. Cosmochim. Acta 1, Suppl. 1, 849–864 (1970)
Smyth, J.R.: Experimental study on the polymorphism of enstatite. Am. Mineralogist 59, 345–352 (1974)
Turner, F.J.: Nature and dynamic interpretation of deformation in calcite of three marbles. Am. J. Sci. 251, 276–298 (1953)
Wenk, H.-R.: Submicroscopical twinning in lunar and experimentally deformed pyroxenes. Contrib. Mineral. Petrol. 26, 315–323 (1970)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Kirby, S.H., Christie, J.M. Mechanical twinning in diopside Ca(Mg,Fe)Si2O6: Structural mechanism and associated crystal defects. Phys Chem Minerals 1, 137–163 (1977). https://doi.org/10.1007/BF00307315
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00307315