Abstract
Monoclinic calcium-poor shear-transformation lamellae and calcium-rich exsolution lamellae occur parallel to (100) in orthopyroxene. The formation of both structures from an orthopyroxene host involves a shear on (100) parallel to [001], with additional cation exchange in the exsolution case. The shear transformation involves a macroscopic simple shear angle of 13.3° (shear strain of 0.236) and produces a specific a-axis orientation with respect to the sense of shear; we have found that this orientation dominates in exsolution lamellae in kinked orthopyroxene, where the sense of shear is known. In undeformed orthopyroxene, there is generally no preferred sense of orientation of the monoclinic a axes. We advance a specific model for exsolution involving nucleation and growth by shear transformation combined with cation exchange, thus circumventing the classical nucleation barrier and permitting exsolution at lower solute supersaturations.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Boland JN (1974) Lamellar structures in low-calcium orthopyroxenes. Contrib Mineral Petrol 47:215–222
Bown MG, Gay P (1959) The identification of oriented inclusions in pyroxene crystals. Am Mineral 44:592–602
Boyd FR, Brown GM (1969) Electron-probe study of pyroxene exsolution. Mineral Soc Am Spec Pap 2:211–216
Brown WL, Morimoto N, Smith JV (1961) A structural explanation of the polymorphism and transitions of MgSiO3. J Geol 69:609–616
Buseck PR, Iijima S (1975) High resolution electron microscopy of enstatite. II: Geological application. Am Mineral 60:771–784
Carter NL (1976) Steady state flow of rocks. Rev Geophys Space Phys 14:301–360
Champness PE, Lorimer GW (1973) Precipitation (exsolution) in orthopyroxene. J Mater Sci 8:467–474
Champness PE Lorimer GW (1974) A direct lattice-resolution study of precipitation (exsolution) in orthopyroxene. Philos Mag 30:357–365
Champness PE, Lorimer GW (1976) Exsolution in silicates. In: Christie JM, Cowley J, Heuer A, Thomas G, Tighe N, Wenk H-R (eds) Applications of electron microscopy in mineralogy. Springer, Berlin Heidelberg New York, pp 174–204
Christian JW (1965) The theory of transformations in metals and alloys. Pergamon Press, Oxford
Clark JR, Appleman DE, Papike JJ (1969) Crystal-chemical characterization of clinopyroxenes based in eight new structure refinements. Mineral Soc. Am Spec Pap 2:31–50
Coe RS (1970) The thermodynamic effect of shear stress on the orthoclino inversion in enstatite and other phase transitions characterized by a finite simple shear. Contrib Mineral Petrol 26:247–264
Coe RS, Kirby SH (1975) The orthoenstatite to clinoenstatite transformation by shearing and reversion by annealing: Mechanism and potential applications. Contrib Mineral Petrol 52:29–55
Coe RS, Müller WF (1973) Crystallographic orientation of clinoenstatite produced by deformation of orthoenstatite. Science 180:64–66
Cottrell AH (1953) Dislocations and plastic flow in crystals. Clarendon Press, Oxford, p 223
Etheridge MA (1975) Deformation and recrystallization of orthopyroxene from the Giles Complex, central Australia. Tectonophysics 25:87–114
Green HW, Radcliffe SV (1972) Deformation processes in the upper mantle. In: Flow and fracture of rocks. Geophys Monogr Am Geophys Union 16:139–156
Hess HH (1941) Pyroxenes of common mafic magmas, Parts I and II. Am Mineral 26:515–535, 573–594
Hess HH (1960) Stillwater igneous complex, Montana. Geol Soc Am Mem 80
Jaeger JC (1957) The temperature in the neighborhood of a cooling intrusive sheet. Am J Sci 255:306–318
Kirby SH (1976) The role of crystal defects in the shear-induced transformation of orthoenstatite to clinoenstatite. In: Christie JM, Cowley J, Heuer A, Thomas G, Tighe N, Wenk H-R (eds) Applications of electron microscopy in mineralogy. Springer, Berlin Heidelberg New York, pp 465–472
Kirby SH, Etheridge MA (1981 in press) Experimental deformation of rock-forming pyroxenes: Ductile strength and flow mechanisms. Tectonophysics
Kohlstedt DL, Vander Sande JB (1973) Transmission electron microscopy investigation of the defect microstructure of four natural orthopyroxenes. Contrib Mineral Petrol 42:169–180
Kohlstedt DL, Vander Sande JB (1976) On the detailed structure of ledges in an augite-enstatite interface. In: Christie JM, Cowley J, Heuer A, Thomas G, Tighe N, Wenk H-R (eds) Applications of electron microscopy in mineralogy. Springer, Berlin Heidelberg New York pp 234–237
Lorimer GW, Champness PE (1973) Combined electron microscopy and analysis of an orthopyroxene. Am Mineral 58:243–248
McLaren AC, Etheridge MA (1976) A transmission electron microscope study of naturally deformed orthopyroxene: Slip mechanism. Contrib Mineral Petrol 57:163–177
Morimoto N, Koto K (1969) The crystal structure of orthoenstatite. Z Kristallogr 129:65–83
Nesbitt RW, Goode ADT, Moore AC, Hopwood TP (1970) The Giles Complex, central Australia: A stratified sequence of mafic and ultramafic intrusions. Geol Soc South Africa Spec Publ 1:547–564
Nicolas A, Bouchez JL, Boudier F (1972) Kinematic interpretation of plastic deformation in the lherzolite massif of Lanzo (Piemont Alps) — comparison with other massifs. Tectonophysics 14:143–172
Nicolas A, Bouchez JL, Boudier F, Mercier JC (1971) Textures, structures and fabrics due to solid state flow in some European lherzolites. Tectonophysics 12:55–68
Paterson MS (1969) The ductility of rocks. In: Argon AS (ed) Physics of strength and plasticity, MIT Press, Cambridge, Mass pp 377–392
Poldervaart A, Hess HH (1951) Pyroxenes in the crystallization of basaltic magma: J Geol 59:472–489
Raleigh CB, Kirby SH, Carter NL, Ave Lallement HG (1971) Slip and the clinoenstatite transformation as competing rate processes in enstatite. J Geophys Res 76:4011–4022
Smith JV (1969) Structure and stability of MgSiO3 polymorphs. Mineral Soc Am Spec Pap 2:3–29
Smith PPK (1978) Electron microscope studies of phase transformation in minerals of the pyroxene group. Unpubl Ph D Thesis, Univ Manchester
Tromsdorff V, Wenk H-R (1968) Terrestrial metamorphic clinoenstatite in kinks of bronzite crystals. Contrib Mineral Petrol 19:158–168
Turner FJ, Heard HC, Griggs DT (1960) Experimental deformation of entstatite and accompanying inversion to clinoenstatite. Proc. 21st Int Geol Congress, Copenhagen 18:399–408
Vander Sande JB, Kohlstedt DL (1974) A high-resolution electron microscopy study of exsolution in enstatite. Philos Mag 29:1041–1049
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Kirby, S.H., Etheridge, M.A. Exsolution of Ca-clinopyroxene from orthopyroxene aided by deformation. Phys Chem Minerals 7, 105–109 (1981). https://doi.org/10.1007/BF00308225
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00308225