Abstract
Diffuse streaks in diffraction patterns of synthetic pyroxene single crystals at elevated temperatures are used to determine which reactions are initiated and how they proceed.
The samples investigated are a) a host orthopyroxene (Wo4En83Fs13) containing oriented pigeonite (Wo6En78Fs16) parallel to (100) and b) a pigeonite (Wo8En75Fs17). The maximum temperatures were 820° C and 1,015° C, respectively. No partial melting occurs at these temperatures, all reactions are in the subsolidus.
In case a) augite is formed parallel to the (001) plane of pigeonite, but the augite is not exsolved by the pigeonite. This is proved by the absence of the obligatory streaks between corresponding reflections in highly resolved precession photographs. Instead, there are streaks from augite to the corresponding reflections of the host orthopyroxene.
Example b) demonstrates that the temperature of the high-low transformation of pigeonite is very sensitive to the Ca content and clearly depends on the exsolution of augite. This augite is oriented parallel to (100) of pigeonite, not to (001). Both the high and the low pigeonite are present over a range of ∼150° C, while the exsolution of augite continues. Simultaneously, orthopyroxene is also formed sharing (100) of pigeonite. There seems to be an indication that only low pigeonite inverts to orthopyroxene.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Brett R, Butler P, Meyer C, Reid AM, Takeda H, Williams R (1971) Apollo 12 igneous rocks 12004, 12008, 12009, and 12022: A mineralogical and petrologic study. In: Proceedings of the Second Lunar Science Conference, Vol 1, The MIT Press, pp 301–317
Brown GE, Prewitt CT, Papike JJ, Sueno S (1972) A comparison of the structures of low and high pigeonite. J Geophys Research 77:5778–5789
Brown GE, Sueno S, Prewitt CT (1973) A new single-crystal heater for the precession camera and four-circle diffractometer. Am Mineral 58:698–704
Buseck PR, Nord GL, 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
Cameron M, Sueno S, Prewitt CT, Papike JJ (1973) High-temperature crystal chemistry of acmite, diopside, hedenbergite, jadeite, spodumene and ureyite. Am Mineral 58:594–618
Grove TL (1982) Use of exsolution lamellae in lunar clinopyroxenes as cooling rate speedometers: an experimental calibration. Am Mineral 67:251–268
Huebner JS, Turnock AC (1980) The melting relations at 1 bar of pyroxenes composed largely of Ca-, Mg-, and Fe-bearing components. Am Mineral 65:225–271
Ishii T (1975) The relations between temperature and composition of pigeonite in some lavas and their application to geothermometry. Mineral J 8:48–57
Jagodzinski H, Korekawa M (1972) X-ray investigations of lunar plagioclases and pyroxenes. In: Proceedings of the Third Lunar Science Conference (Supplement 3, Geochim Cosmochim Acta), Vol 1, The MIT Press, pp 555–568
Korekawa M, Schröpfer L (1982) Röntgenographische Untersuchungen an geheizten Ca-reichen Pigeoniten und Augiten bei währenden Temperaturen. Fortschr Mineral 60(1):120–122
Murakami T, Takéuchi Y, Yamanaka T (1982) The transition of orthoenstatite to protoenstatite and the structure at 1,080° C. Z Kristallogr 160:299–312
Nakazawa H, Hafner SS (1977) Orientation relationships of augite exsolution lamellae in pigeonite hosts. Am Mineral 62:79–88
Nord GL, Heuer AH, Lally JS (1976) Pigeonite exsolution from augite. In: Wenk HR (ed) Electron microscopy in mineralogy. Springer, Berlin Heidelberg New York, pp 220–227
Nord GL, McCallister RH (1979) cited by Buseck PR, Nord GL, Veblen DR in Subsolidus phenomena in pyroxenes. In: Prewitt CT (ed) Reviews in Mineralogy, Vol 7, Pyroxenes, Mineralogical Society of America, Washington, DC. pp 117–211 (1980)
Poldervaart A, Hess HH (1951) Pyroxenes in the crystallization of basaltic magma. J Geol 59:472–489
Prewitt CT, Brown GE, Papike JJ (1971) Apollo 12 clinopyroxenes: High temperature X-ray diffraction studies. Proceedings of the Second Lunar Science Conference, Vol 1. The MIT Press, pp 59–68
Ried H (1982) Über den Realbau von Pyroxenen und Pyroxenoiden: Transmissionselektronenmikroskopische Untersuchungen insbesondere von Kettenperiodizitätsfehlern und Entmischungen. Dissertation, University of Frankfurt
Ross M, Huebner S (1979) Temperature-composition relationships between naturally occuring augite, pigeonite, and orthopyroxene at one bar pressure. Am Mineral 64:1133–1155
Schröpfer L, Müller WF, Korekawa M, Jagodzinski H (1976) High resolution X-ray diffraction and transmission electron microscopy studies on exsolution phenomena of lunar pyroxenes from 14053. Abstr Seventh Lunar Science Conference, Lunar Science Institute, Houston, Texas, pp 779–781
Smyth JR (1974a) Experimental study on the polymorphism of enstatite. Am Mineral 59:345–352
Smyth JR (1974b) The high temperature crystal chemistry of clinohypersthene. Amer Mineral 59:1069–1082
Sueno S, Cameron M, Prewitt CT (1976) Orthoferrosilit: High-temperature crystal chemistry. Am Mineral 61:38–53
Takeda H, Ridley WI (1972) Crystallography and chemical trends of orthopyroxene-pigeonite from rock 14310 and coarse fine 12033. In: Proceedings of the Third Lunar Science Conference (Supplement 3, Geochimica et Cosmochimica Acta) Vol 1. The MIT Press, pp 423–430
Turnock AC, Lindsley DH, Grover JE (1973) Synthesis and unit cell parameters of Ca-Mg-Fe pyroxenes. Am Mineral 58:50–59
Walker F, Poldervaart A (1949) Karoo dolerites of the Union of South Africa. Geol Soc Am Bull 60:591–706
Yund RA, Tullis J (1983) Strained cell parameters for coherent lamellae in alkali feldspars and iron-free pyroxenes. Neues Jahrb Mineral Monatsh 1:22–34
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Schröpfer, L. Observation of reactions in synthetic Ca-poor pyroxene single crystals at elevated temperatures by X-ray diffraction. Phys Chem Minerals 12, 49–54 (1985). https://doi.org/10.1007/BF00348747
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00348747