Abstract
Fine textures of exsolution lamellae and interface boundaries between augite and pigeonite in augite crystals from Skaergaard ferrogabbro 4430 have been studied by high resolution electron microscopy and X-ray methods. Thick pigeonite lamellae have higher densities of (100) stacking faults than thin lamellae. The displacement vector of the faults has been determined as 5/6c from the measured density of faults and the relative rotation of the augite and pigeonite lattices. The augite and pigeonite lattices are apparently coherent, and no growth ledges were observed at the interfaces. The stacking faults are often combined with the antiphase boundary of pigeonite resulting in a total displacement vector of 1/2(a+b)+5/6c. The observation of thick and thin pigeonite lamellae indicated that the thickening of (001) pigeonite lamellae was controlled by coherency strains accumulated at the interfaces between augite and pigeonite.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bollman, W., Nissen, H.-U.: A study of optimal phase boundaries: the case of alkali feldspars. Acta Crystallogr. A24, 546–557 (1968)
Carpenter, M.A.: Nucleation of augite at antiphase boundaries in pigeonite. Phys. Chem. Minerals 2, 237–251 (1978)
Champness, P.E., Copley, P.A.: The transformation of pigeonite to orthopyroxene. In: Electron microscopy in mineralogy, Wenk, H.-R. (ed.). Berlin, Heidelberg, New York: Springer 1976, pp. 228–233
Champness, P.E., Lorimer, G.W.: Precipitation (exsolution) in an orthopyroxene. J. Mater. Sci. 8, 467–474 (1972)
Copley, P.A., Champness, P.E., Lorimer, G.W.: Electron petrography of exsolution textures in an iron-rich clinopyroxene. J. Petrol. 15, 41–57 (1974)
Kohlstedt, D.L., Vander Sande, J.B.: On the detailed structure of ledges in an augite-enstatite interface. In: Electron microscopy in mineralogy, Wenk, H.-R. (ed.). Berlin, Heidelberg, New York: Springer 1976, pp. 234–237
Morimoto, N., Tokonami, M.: Domain structure of pigeonite and clinoenstatite. Am. Mineral. 54, 725–740 (1969a)
Morimoto, N., Tokonami, M.: Oriented exsolution of augite in pigeonite. Am. Mineral. 54, 1101–1117 (1969b)
Nobugai, K., Tokonami, M., Morimoto, N.: A study of subsolidus relations of the Skaergaard pyroxenes by analytical electron microscopy. Contrib. Mineral. Petrol. 67, 111–117 (1978)
Robinson, P., Ross, M., Nord, G.L. Jr., Smyth, J.R., Jaffe, H.W.: Exsolution lamellae in augite and pigeonite: fossil indicators of lattice parameters at high temperature and pressure. Am. Mineral. 62, 857–873 (1977)
Wood, B.J., Banno, S.: Garnet-orthopyroxene and orthopyroxene-clinopyroxene relationships in simple and complex system. Contrib. Mineral. Petrol. 42, 109–124 (1973)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Nobugai, K., Morimoto, N. Formation mechanism of pigeonite lamellae in skaergaard augite. Phys Chem Minerals 4, 361–371 (1979). https://doi.org/10.1007/BF00307537
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00307537