Abstract
Exsolution systems in synthetic pyroxenes were studied by transmission electron microscopy. An iron free sample En80Wo20 was prepared by devitrifying glass at 1300°C. Samples with bulk composition En50Fs30Wo20 and En35Fs38Wo27 were given various but well-defined heat treatments. The exsolution systems observed cannot unambiguously be related to the heat treatment.
Periodic lamellar exsolution was observed parallel to (001) and (100) with sharp satellite reflections in the diffraction diagram. In more complex exsolution systems coarse (100) lamellae were found together with fine lamellae parallel to (001) and (100). An unusual phenomenon occurs at a (100) twin boundary where both individuals display exsolution lamellae parallel to (001). Pigeonite lamellae in one twin meet augite lamellae of the other individual at the twin boundary and vice-versa. The precise matching is achieved by a change in width near the boundary.
Smoothly curved phase boundaries are developed in the obtuse angle of crosshatched (100) and (001) pigeonite lamellae in augite, whereas the boundaries in the acute angle are straight with sharp edges. This is consistent with elastic energy constraints.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bown MG, Gay P (1960) An X-ray study of exsolution phenomena in the Skaergaard pyroxenes. Mineral Mag 32:379–388
Buseck PR, Nord GL Jr, Veblen DR (1980) Subsolidus phenomena in pyroxenes. In: Prewitt CT (ed) Reviews in Mineralogy, Vol 7: Pyroxenes: Mineralogical Society of America, Washington DC, pp 117–211
Carpenter MA (1978) Nucleation of augite at antiphase boundaries in pigeonite. Phys Chem Minerals 2:237–251
Champness PE, Dunham AC, Gibbs FGF, Giles HN, Mackenzie WS, Stumpfl EF, Zussman J (1971) Mineralogy and petrology of some Apollo 12 lunar samples. Proc 2nd Lunar Sci Conf 1:359–376
Clark JR, Ross M, Appleman D (1971) Crystal chemistry of a lunar pigeonite. Am Mineral 56:888–908
Copley PA, Champness PE, Lorimer GW (1974) Electron petrography of exsolution textures in an iron-rich clinopyroxene. J Petrol 15:41–57
Fletcher RC, McCallister RH (1974) Spinodal decomposition as a possible mechanism in the exsolution of clinopyroxene. Carnegie Inst Washington Yearb 73:396–399
Grove TL (1982) Use of exsolution lamellae in lunar clinopyroxenes as cooling rate speedometers: an experimental calibration. Am Mineral 67:251–268
Hess HH (1941) Pyroxenes of common mafic magmas. Am Mineral 26:515–535, 573–594
Jagodzinski H, Korekawa M, Müller WF, Schröpfer L (1975) X-ray diffraction and electron microscope studies of clinopyroxenes from lunar basalts 75035 and 75075. Proc 6th Lunar Sci Conf:773–778
Lally JS, Heuer AH, Nord GL Jr, Christie JM (1975) Subsolidus reactions in lunar pyroxenes: an electron petrography study. Contrib Mineral Petrol 51:263–281
McCallister RH, Yund RA (1977) Coherent exsolution in Fe-free pyroxenes. Am Mineral 62:721–726
Morimoto N, Tokonami M (1969a) Oriented exsolution of augite in pigeonite. Am Mineral 54:1101–1117
Morimoto N, Tokonami M (1969b) Domain structure of pigeonite and clinoenstatite. Am Mineral 54:725–740
Müller WF (1974) Transmissionselektronenmikroskopische Untersuchung von Pyroxenen zweier lunarer Basalte. Fortschr Mineral 51 Beih 1:85–87
Müller WF (1976) In: Wenk HR (ed) Electron microscopy in mineralogy. Springer, Berlin Heidelberg New York, pp 2–3
Nakazawa H, Hafner SS (1977) Orientation relationships of augite exsolution lamellae in pigeonite hosts. Am Mineral 62:79–88
Nobugai K, Morimoto N (1979) Formation mechanism of pigeonite lamellae in Skaergaard augite. Phys Chem Minerals 4:361–371
Nord GL Jr, Lally JS, Heuer AH, Christie JM, Radcliffe SV, Griggs DT, Fisher RM (1973) Petrologic study of igneous and metaigneous rocks from Apollo 15 and 16 using high voltage transmission electron microscopy. Proc 4th Lunar Sci Conf 1:953–970
Poldervaart A, Hess HH (1951) Pyroxenes in the cristallisation of basaltic magmas. J Geol 59:472–489
Ried H (1982) Über den Realbau von Pyroxenen und Pyroxenoiden: Transmissionselektronenmikroskopische Untersuchungen insbesondere von Kettenperiodizitätsfehlern und Entmischungen. Dissertation, Frankfurt am Main
Ried H (1984) Intergrowth of pyroxene and pyroxenoid. Chain periodicity faults in pyroxene. Phys Chem Minerals 10:230–235
Robinson P, Ross M, Nord GL Jr, Smyth JR, Jaffe HW (1977) Exsolution lamellae in augite and pigeonite: fossil indicators of lattice parameters at high temperature and pressure. Am Mineral 62:857–873
Ross M, Huebner JS (1979) Temperature-composition relationships between naturally occurring augite, pigeonite, and orthopyroxene at one bar pressure. Am Mineral 64:1133–1155
Schröpfer L (1985) Observations of reactions in synthetic Ca-poor pyroxene single crystals at elevated temperatures by X-ray diffraction. Phys Chem Minerals 12:49–54
Schröpfer L, Feuer H (1985) Personal communication
Tullis J, Yung RA (1979) Calculation of coherent solvi for alkali feldspar, iron-free clinopyroxene, nepheline-kalsite and hematite-ilmenite. Am Mineral 64:1063–1074
Yund RA, McCallister RH (1970) Kinetics and mechanisms of exsolution. Chem Geol 6:5–30
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ried, H., Fuess, H. Lamellar exsolution systems in clinopyroxene. Phys Chem Minerals 13, 113–118 (1986). https://doi.org/10.1007/BF00311901
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00311901