Abstract
Ion-thinned samples of lunar rock 12052 have been examined in the electron microscope. Exsolution textures have been observed in the pyroxene on a finer scale than those found in Apollo 11 rocks, indicating a faster cooling rate. The early stages of the reaction involve modulations on both (001) and (100) which suggest that decomposition may occur by a spinodal mechanism. A two-stage exsolution structure in the augite rim of a phenocryst is consistent with a sudden increase in the cooling rate—possibly when the magma was extruded onto the surface of the moon.
The presence of antiphase domains in all primary and precipitated pigeonites confirms that pigeonites of all compositions have the space group C2/c at high temperatures.
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References
Ardell, A. J., Nicholson, R. B., Eshelby, J. D.: On the modulated structure of aged Ni-Al alloys. Acta Met. 14, 1295–1309 (1966).
Bailey, J. C., Champness, P. E., Dunham, A. C., Esson, J., Fyfe, W. S., MacKenzie, W. S., Stumpfl, E. F., Zussman, J.: Mineralogy and petrology of Apollo 11 lunar samples. Proc. Apollo 11 Lunar Sci. Conf. Geochim. Cosmochim. Acta, Suppl. 1, 1, 169–194 (1970).
Bancroft, G. M., Bown, M. G., Gay, P., Muir, I. D., Williams, P. G. L.: Mineralogical and petrological investigation of some Apollo 12 samples. Second Lunar Sci. Conf. (unpublished proceedings, 1971).
Barber, D. J.: Thin foils of non-metals made for electron microscopy by sputter-etching. J. Materials Sci. 5, 1–8 (1970).
Bence, A. E., Papike, J. J., Prewitt, C. T.: Apollo 12 clinopyroxenes: chemical trends. Earth Plan. Sci. Lett. 8, 393–399 (1970).
Bown, M. G., Gay, P.: Observations on pigeonite. Acta Cryst. 10, 440–441 (1957).
—: The identification of oriented inclusions in pyroxene crystals. Am. Mineralogist 44, 592–602 (1959).
—: An X-ray study of exsolution phenomena in the Skaergaard pyroxenes. Mineral. Mag. 32, 379–388 (1960).
Boyd, F. R.: Anatomy of a mantled pigeonite from Oceanus Procellarum. Carnegie Inst. Wash. Yearbook 69, 216–228 (1971).
Cahn, J. W.: Spinodal decomposition. Trans. AIME 242, 166–180 (1968).
Carter, N. L., Leung, I. S., Ave'Lallemant, H. G., Fernandez, L. A.: Growth and deformational structures in silicates from Mare Tranquillitatis. Proc. Apollo 11 Lunar Sci. Conf. Geochim. Cosmochim. Acta., Suppl. 1, 1, 267–285 (1970).
Champness, P. E., Dunham, A. C., Gibb, F. G. F., Giles, H. N., MacKenzie, W. S., Stumpfl, E. F., Zussman, J.: Mineralogy and petrology of some Apollo 12 lunar samples. Proc. Second Lunar Sci. Conf. 1, 449–466 (1971).
- Lorimer, G. W.: Lunar pyroxenes. Proc. 7th Intl. Elect. Microscopy Cong., Grenoble, 639–640 (1970).
Fisher, R. M., Marcinowski, M. J.: Direct observations of antiphase boundaries in the AuCu3 superlattice. Phil. Mag. 6, 1385–1405 (1961).
Huston, E. L., Cahn, J. W., Hilliard, J. E.: Spinodal decomposition during continuous cooling. Acta Met. 14, 1053–1062 (1966).
Korekawa, M. Nissen, H.-U., Philipp, D.: X-ray and electron-microscopic studies of a sodium-rich low plagioclase. Z. Krist. 131, 418–436 (1970).
Morimoto, N., Tokonami, M.: Domain structure of pigeonite and clinoenstatite. Am. Mineralogist 54, 725–740 (1969a).
—: Oriented exsolution of augite in pigeonite. Am. Mineralogist 54, 1101–1117 (1969b).
Owen, D. C., McConnell, J. D. C.: Spinodal behaviour in an alkali feldspar. Nature Phys. Sci. 230, 118–119 (1971).
Poldervaart, A., Hess, H. H.: Pyroxenes in the crystallisation of basaltic magma. J. Geol. 59, 472–489 (1951).
Prewitt, C. T., Papike, J. J.: Cummingtonite: a reversible nonquenchable transition from P21/m to C2/m symmetry. Earth Plan. Sci. Lett. 8, 448–450 (1970).
Radcliffe, S. V., Heuer, A. H., Fisher, R. M., Christie, J. M., Griggs, D. T.: High voltage (800 KV) electron petrography of Type B rooks from Apollo 11. Proc. Apollo 11 Lunar Sci. Conf. Geochim. Cosmochim. Acta, Suppl. 1, 1, 731–748 (1970).
Ross, M., Bence, A. E., Dwornik, E. J., Clark, J. R., Papike, J. J.: Mineralogy of the lunar clinopyroxenes, augite and pigeonite. Proc. Apollo 11 Lunar Sci. Conf. Geochim. Cosmochim. Acta, Suppl. 1, 1, 839–848 (1970).
- Huebner, J. S., Dowty, E.: Melting and sub-solidus phase relationships of augite and pigeonite from lunar rock 12021. Second Lunar Sci. Conf. (unpublished proceedings, (1971).
Yund, R. A., McCallister, R. H.: Kinetics and mechanisms of exsolution. Chem. Geol. 6, 5–30 (1970).
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Champness, P.E., Lorimer, G.W. An electron microscopic study of a lunar pyroxene. Contr. Mineral. and Petrol. 33, 171–183 (1971). https://doi.org/10.1007/BF00374061
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DOI: https://doi.org/10.1007/BF00374061